Engineering Properties and Applications of Lead Alloys

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ENGINEERING PROPERTIES AND APPLICATIONS OF LEAD ALLOYS

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ENGINEERING PROPERTIES AND APPLICATIONS OF LEAD ALLOYS Sivaraman Guruswamy University of Utah Salt Lake City, Utah

Prepared for the International Lead Zinc Research Organization, Inc. Research Triangle Park, North Carolina

M A R C E L

MARCEL DEKKER, INC. D E K K E R

-

N E WYORK BASEL

ISBN: 0-8247-8247-X

This book is printed on acid-free paper. Headquarters

Marcel Dekker, Inc. 270 Madison Avenue, New York, NY 10016 tel: 2 12-696-9000; fax: 2 12-685-4540 Eastern Hemisphere Distribution

Marcel Dekker AG Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41-61-261-8482: fax: 41-61-261-8896 World Wide Web

http://www.dekker.com The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/Professional Marketing at the headquarters address above. Copyright 0 2000 by Marcel Dekker, Inc. All Rights Reserved.

Neither this book nor any part may be reproduced or transmitted in any form or by anymeans,electronic or mechanical,includingphotocopying,microfilming,and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Current printing (last digit): I O 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA

To vdsantha, Kavitha, and our parents

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Foreword

This book represents the first new compilation on lead technology in a half century. Prior to this publication, the definitive source on lead was Wilhelm Hoffman's Leacl and Leacl Alloys-P1.c)pc.r-ties und Technology, the tirst edition of which was published in German i n 1941, based on the research work Hoffman and his colleagues conducted at the Lead Research Center in Berlin. Following World War 11, there was a major expansion in the technical and scientific literature on lead and several years' work was required before the second edition of the book was published in 1962. That book contained virtually all the relevant technical data on lead, its alloys, and its uses, along with processing methodologies. An English translation by Hoffman was pubthe lished in 1970. It is noteworthy that in the forewordHoffmannotes initiative of the then relatively young International Lead Zinc Research Organization (ILZRO) to carry out an active international program of research on lead. ILZRO is pleased to have sponsored the work of Sivaraman Guruswamy and trusts that his efforts will ensure that modern technical knowledge of the properties of this ancient metal will be readily available to technologists in the new century. Special acknowledgment must be paid to Jeffrey Zelms, president of the Doe RunCompany,and to CharlesYanke,president of VulcanLead Resources,both of whomrecognized the need for thisbook and urged ILZRO to undertake this project. . l e u m e F . Cols President International Lead Zinc Research Organization,

Inc. V

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Preface

Lead is a rare element in the earth’s crust, but since it is found in concentrated deposits it can be produced atlow cost, and ranks fifthin tonnage consumed after iron, copper, aluminum, and zinc. Some of the many applications of lead are: automobile batteries, uninterruptible power sources for computers that store and process vital national security and business information, solders used in printed circuit boards, radiation shields in nuclear facilities, radiation shields in CAT scanners and other medical X-ray apparatus, keels in yachts, balancing weights in computer hard disk drives, lead and lead-lined vessels in chemical plants, vacuumseals in lightbulbs, the explosive detonation cords in the Space Shuttle, acousticbarrier panels, crystal glasses, fiber-optic cables, and infrared detectors in pollution monitoring. These applications underscore the importance of lead to modern life. The most comprehensive text on this topic is Lead and Lead Alloys by Hoffmann,published by Springer Verlag in 1941andrevised in 1962 of the Interand 1970. In response to a recognized need, Frank Goodwin, national LeadZincResearchOrganization, initiated andorganizedaconon lead. sortium of sponsorsforanup-to-dateandcomprehensivebook When Dr. Goodwinapproachedmetowrite this book, I wasexcitedand honored to be trusted with this enormous task. The book is intended as an introductory resource on lead and lead alloys, providing information on engineering properties, processing of various lead forms, and engineering applications that takeadvantage of the unique properties of lead and lead alloys. The book will also be a resource for professionals involved in the production and application of lead alloy products. Itis hoped that the text will stimulateimprovements in existing applicationsanddevelopment of new applications to take advantage of the unique properties of lead and lead vii

viii

Preface

alloys. The book focuses on the use of lead in pure or alloy form for engineering applications. In setting boundaries for the scope of the book, we decided not to address the use of lead in the form of chemicals. The book has five chapters. The introductory chapter provides information on worldwide sources of lead, production of refined lead from Pb ores, and key information on pure lead. This is followed, in Chapter 2 , by the presentation of an exhaustive set of data on the physical, mechanical, corrosion, acoustic, damping, and nuclear properties of lead and lead alloys. Adequate background information is given so that the reader can appreciate the importance and limitations of the data. Chapter 3 deals with the processing of lead products and gives the user a general appreciation and background of the processing of commercially available lead product forms. The topics covered include casting, rolling, extrusion, machining, welding, and mechanical joining techniques. New developments in continuous casting of strips for battery grids, continuous casting of rods, friction-stir welding, and water-jet machining of lead products are included in this section. Chapter 4 introduces the reader to a wide spectrum of modern and historic applications in which lead and its alloys have been used and provides a rationalization for the choice of lead in these applications. Most applications involve the use of lead in a form that is recycled. Chapter 5 provides information on health and safety issues, and the recommended guidelines for the safe and appropriate handling of lead products. It is our hope that the book will meet the many needs of experienced and nascent users of lead and lead alloys. Publications by the International LeadZincResearchOrganization (ILZRO), Lead Industries Association (LIA), Lead Development Association (LDA), and Lead Sheet Association (LSA), and the groundbreaking work of Hoffman have been heavily relied on in preparing this book. Many individuals and companies were also helpful.I am grateful for their generosity in providing the information and permission to use it extensively. Special thanks are due to SpringerVerlag for generously allowing use of the material from Dr. Hoffmann’s classic book. I would like to thank the following for responding generously to my requests for information. David Wilson, Lead Development Association, London Jerome F. Smith, Lead Industries Association, N Y Michael King, V. Ramachandran, and Alan Kafka, ASARCO, NY Eugene Valeriote and Jennifer Coe, Cominco, Canada Peter Bryant and Paul Frost, Britannia Refined Metals, United Kingdom Stan Hall, Lead Sheet Association, Kent, United Kingdom E. G. Russell, Aberfoyle Limited, Australia

Preface

ix

Masao Hirano and F. Sakurai, Mitsubishi Materials, Japan Tatsuya Yamamoto, Mitsui Mining and Smelting, Japan John Manders, PASMINCO, Australia Takao Mori, Japan Lead Zinc Development Association Chuck yanke and Scott Hutcheson, Vulcan Lead, W1 Toshiharu Kanai, Sumitomo Metal Mining, Japan Kazuyoshi Inoue, Toho Zinc Co., Japan Goran Villner, Boliden Market Research, Sweden Francois Wilmotte, Centre d’lnformation du Plomb, France David Prengaman, RSR Corporation, Dallas, TX Akiro Hosoi, Dowa Mining, Japan Albano Piccinin, Union Miniere, Belgium P. R.JanischandRichardD.Beck,BlackMountainMineralDevelopment, South Africa Shuya Fujie, Nippon Mining, Japan

I would like to express my great appreciation to Pat Mosley and Robert Putnam of ILZRO, Paul Frost of Britannia Metals, Eugene M. Valeriote and his colleagues at Cominco, and Dr.Venkoba Ramachandran of ASARCO of the manuscript and valuable comments. I also for their critical review would like to thank Janice Atkinson at ILZRO for all her help. I would also like to acknowledge the kindness of all my teachers, in particular John Hirth, who generously shared their knowledge and wisdom. The invaluable, timely, and enthusiastic help of my student Nakorn Srisukhumbowomchai in the preparation of this book is gratefully acknowledged. 1 would also like to thank my other students and colleagues in the Department of Metallurgical Engineering at the University of Utah who have been very supportive and provided a conducive environment during this period. Finally, I would like to take this opportunity to express my deep sense of gratitude to Frank Goodwin, ILZRO, for his confidence in me, providing materials from ILZRO as I needed them, reviewing the manuscript, giving permission to use extensively many of his publications, helping promptly whenever I needed it, and for his friendship. Most of all, I am very lucky to have the unqualified love, encouragement, and support of my wife, Vasantha, and daughter, Kavitha.

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Contents

Foreword Preface 1.

1’

Jerome F. Cole

1’11

Introduction I. WorldwideSources of Lead 11. Refined LeadProductionandConsumption 111. Production of LeadMetal IV. HealthandSafety Issues V. Properties of PureLead

Patterns

1 2 6 15 18 19

2.

Properties of Leadand Its Alloys I. PhysicalProperties of Leadand Its Alloys 11. Mechanical Properties of Lead and Lead Alloys 111. Creep Behavior IV. Fatigue Strength V. CorrosionProperties VI. AcousticProperties of LeadandLeadComposites VII. NuclearProperties

27 27 57 123 168 192 232 276

3.

Processing of LeadProducts I. MeltingandCasting 11. Metal Forming 111. Joining of Lead

309 310 342

4.

Applications of Lead I. Lead-Acid Batteries

of LeadAlloys

377 429 430 xi

Contents

xii

11. 111. IV. V. VI. VII. VIII. IX. X. XI. XII. XIII.

XIV.

x v.

XVI. XVII. XVIII. XIX.

Use of Lead in Earthquake Protection Use of Lead in Brick Wall Infills Lead-Tin Alloys in Organ Pipes Use of Lead Sheets in Architecture Lead in Radiation Shielding and Waste Management Use of' Lead Alloys for Printing Types Bearing Metals Packaging and Sealing Fusible Alloys Lead Heat-Treating Baths Use of Lead in Inertial Applications Solders Ammunition Lead Cable Sheathing Insoluble Lead Anodes Use of Lead in Bi-Based Oxide High-T, Superconductors Lead in Glass Lead Chalcogenide Semiconductors

S. Lead in the Environment I . Toxic Properties of Lead 11. Occupational Exposures

4s 8 476 479 483 499 530 534 539 542 546 547 550 5 69 570 585 587 589

S9 1 593

596 599 60.5

Index

62 I

ENGINEERING PROPERTIES AND APPLICATIONS OF LEAD ALLOYS

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Introduction

In a world of rapidly changing technologies, lead and other classical metals and alloys havecontinued to maintain their importance.Lead (chemical symbol Pb), is an essential commodity in the modern industrial world, ranking fifthin tonnageconsumed after iron,copper,aluminum, and zinc. In 1996, the UnitedStates,China, the UnitedKingdom,Germany,Canada, Japan, South Korea, Italy, France, Mexico, Spain, Taiwan, India, and Brazil accounted for 77% of the 6,045,000 metric tons of refined lead consumed in the world [l]. Slightly over half of the lead produced in the world now comes from recycled sources. Lead,copper, silver, andgoldwere the metals first used by ancient humans[2,3].Leadhasbeenmined and smeltedfor at least 8000 years. Lead beads found in Turkey have been dated to around 6500 B.C. The Egyptians used lead as early as 5000 B.C. A leadmine in RioTinto in Spain B.C. operated in 2300 BC. and the Chineseused lead coinsaround2000 Simplicity of reduction from ores, low melting point, and ease of fabrication presumably led to its use. Leadwasalsowidelyused by the Greeks and in 3-m lengths and in 15 different standard diRomans. Lead water pipes ameters have been found in the ruins of Rome and Pompeii, confirming the use of lead during that period. Some pipes still in excellent condition have been found in modern-day Rome and Britain [4]. The toxicity of lead was identified by Marcus Vitruvius Pollio, a first-century Roman architect and engineer, from the poor color of the lead workers of those times [3]. Despite their known toxicity, lead and its alloys can be handled safely and continue to be critical in many areas for the modem society. This continued dependence on lead arises from several of its unique properties. The low melting point, ease of casting, high density, softness and high mallea1

2

Chapter 1

bility at room temperature, low strength, ease of fabrication, excellent resistance to corrosion in acidic environments, attractive electrochemical behavior in manychemicalenvironments,chemical stability in air, water, and earth, the highatomicnumber, and stable nuclearstructurehavemadea unique place for lead in our life. Lead affords us the protection from dangerous x-ray, gamma ray, neutron, and other ior.izing radiation. I t serves as one of the most efficient acoustic insulation materials. It also acts as a sealthat hasservedwell in seismic ant. It hasuniquedampingcharacteristics protection of buildings and other structures. It acts as a space-efficient counterweight. Its chemical and electrochemical characteristics make it useful as the most economically viable material in batteries that serve as a primary electrical powersource in automobiles and asaback up powersupply for computers that store andprocess vital national security andbusiness information. As with many elements used in high technology, health hazards posed by lead is a concern. Lead and its compounds are cumulative poisons and should be handled with recommended precautions. These materials should not be used in contact with food and other substances that may be ingested. A proper understanding and appropriate use of lead and its alloys in existing applications and in applications yet to be conceived require an up-to-date sourcebook on the properties of lead and its alloys, its processing techniques, and their engineering applications. The intent of this book is to serve suchpurpose. In preparing this book, International LeadZincResearch Organization (ILZRO) publications, Lead Industries Association (LIA) publications, LeadDevelopmentAssociation(LDA) publications, Lead SheetAssociation (LSA) publications, help of many in the industry and academia, and the classic work of Professor Hoffman [2] have been relied upon heavily.

I.

WORLDWIDE SOURCES OF LEAD

Lead constitutes only about 12.5 ppm by weight of the Earth’s crust, and it ranks 34th among elements in relative abundance [S,6]. It ranks well below (0.57%), aluminum (8.23%), iron (5.63%), magnesium(2.33%),titanium zirconium (165 ppm), chromium (100 ppm), nickel (75 pp”), zinc (70 ppm), and copper (SS ppm). However, the occurrence of concentrated and easily accessible lead ore deposits is unexpectedly high, and these are widely distributed throughout the world. This makes lead easily mined and produced at low cost. The most important ore mineral is galena, PbS (87% Pb), followed by (77.5% Pb). The latter two anglesite, PbSO, (68% Pb), and cerussite, PbCO,%

Introduction

3

minerals result from the natural weathering of some galena. Lead and zinc Ores are frequently found together because of their similar affinity for both oxygen (lithophile) and sulfur (chalcopile) and their transport to the same degree by carbonate solutions [6]. Galena ores may be associated with sphalerite (ZnS), pyrite (Fe$), marcasite (Fe$, a low-temperature polymorph of pyrite), chalcopyrite (CuFeS,), tetrahedrite [ ( C U F ~ ) , ~ S ~ , S cerussite ,,], (PbCO,), anglesite (PbSO,), dolomite [CaMg(CO,),], calcite (CaCO,), quartz (SiO,), and barite (BaSO,), as well as the valuable metals gold, silver, bismuth, and antimony [2,4,7,8]. The formation of lead ore deposits likely occurred by the concentration of metal sulfides in the liquid remaining after the crystallization of silicates from molten magma and the penetration of this liquid under pressure into available channels such asfault fissures. Aqueous solution of these minerals, including PbS, in hydrothermal fluids leads to their transport and the preon cipitation of PbS as the temperature and pressure decreases. Depending the temperature and pressure at which they are formed, the ore deposits are classified into five categories (listed in the decreasing order of temperature and pressure): telethermal, leptothermal,mesothermal,pyrometasomatic, and hypothermal [2,7]. The types of deposits with lead as a major constituent include strata-bound deposits, volcanic-sedimentary deposits, replacement deposits, veins, and contact metamorphic deposits [8]. Strata-bound deposits are bedded layered deposits formed at the same time as the host rock. Volcanic-sedimentary deposits contain massive sulfide bodies commonly interlayered with volcanic or sedimentary rocks. The ore is commonly a finegrained mixture of pyrite or pyrrhotite, sphalerite, galena, and chalcopyrite, withminoramounts of nonmetallicandcarbonateminerals.Replacement deposits of lead and zinc are commonly irregular hydrothermal deposits in carbonate rocks, but some also occur in quartzites or metamorphic rocks. The vein deposits are commonly situated in faults, joints,orformational contacts. The veins are generally arranged in pod-shaped deposits or shoots 3-30 ft long horizontally anddippinghundreds of feet vertically. Many highlyproductivevein-typedeposits are in Europe,CentralAmerica,and South America. Contact metamorphic deposits are found near igneous intrusions, which have either provided the solutions or emanations creating the deposits, or have altered and rearranged a mineral deposit already present prior to the intrusion. Depositsrange in sizefromsmall vein systems to massive pods hundreds of feet long (81. The estimated economic reserves of lead in the world are 71 million tons and are scattered around the world [4,8-10]. Australia(19.4million tons), the United States (8 million tons), Canada (4 million tons), Mexico (3 milliontons), the formerSovietUnion (9 milliontons),andChina (7 million tons) account for over two-thirds of these reserves. The total world

4

Chapter 1

reserve base (which includes marginal deposits) is estimated at 124 million tons. If lead scrap, now a major source of lead, and less economic lead ore deposits are considered, the entire reserve base for the world is estimated at 140 million tons [4]. The concentration of lead in ore bodies of commercial interest generally ranges from 2% to 6%, with an average of 2.5%. Improvements in ore-dressingtechniqueshavemadepossible the exploitation of deposits having lead contents even less than 2%. Australia, the United States, Canada, Peru, Mexico, China, the former USSR,Sweden,andSouthAfrica are the leadingcountries in leadmine production [l]. Thecombinedproduction in the RussianFederation,Kazakhstan,andUzbekistanhaveprecipitouslydroppedfrom the levels at 1993. In contrast, the production in Chinese mines have doubled between 1993 and 1996. Table 1 presents the levels of lead mined in different countries during 1993- 1996. The total world lead mine production in 1997 and 1998 were 3.03 and 3.1 1 million tons respectively. Most (88%) of the lead mined in the United States comes from 8 mines in Missouri and the rest comes from 11 mines in Colorado, Idaho, Montana, Alaska, Washington, and Nevada. Most of the known U.S. reserves for lead are located in federally owned land in Missouri; future mine development depends on the outcome of the U.S. government’s intent to reform the Mining Law of 1872. The bulk of the Canadian lead mine output comes from Trail MineB.C.;FaroMine, Yukon Territories; No.12Mine at Bathurst, N.B.; andFIin FlonandSnowLake,Manitoba.The principal lead mines in SouthAmerica are CerrodePasco,Milpo,Huanzala,Atacocha,and Colquijirco mines in Peru, Naica, Real de Angeles, Sta Barbara, San Fran del Oro, and El Monte mines in Mexico, Aguilar Mine in Argentina, and Quiomo Mine in Bolivia. About 56% of lead mined in Latin America came from 12 mines and the rest came from over 60 small mines producing lead as a by-product of Zn and/or Ag extraction. Mexico and Peru produce more than 90% of lead mined in Latin America [9- 1 l]. When the newBHPMine at Cannington,Australiareaches its full capacity of 175,000 tons/year, it will be the largest lead mine in the world. This together with the other two largest mines in Australia at Broken Hill (South) (N.S.W.) and Mount Isa (Queensland) will account for the bulk of lead mined in Australia. The other major mines are McArthur River Mine (NT), Hellyer Mine (TAS), Rosebery Mine (TAS), Thalanga Mine (N.S.W), Woodlawn Mine (N.S.W.), and Woodcutters Mine (NT). The lead output of Sweden, the majorproducer in westernEurope, comes from mines at Garpensburg, Laisvall, Langdal, Petiknas, Renstrom, and Ammeberg. In the former USSR, the larger lead mines are in the Leninogarsk region, the Kentau region, and the Karatau region in Kazakhstan, Uchkulachskoye deposits in Uzbekistan, and the Maritime region in the Rus-

5

Introduction Table 1 Total Mine Production in Thousands of Tons [ 11 Annual totals

Europe Austria Bulgaria Czech Republic'' Finland Greece Ireland Italy Macedonia Norway Poland Romania Russian Federation Slovenia Spain Sweden United Kingdom Yugoslavia F.R.

1993

1994

1995

39 1 2 34 2

398 32 0

383 33 -

-

-

-

26 45 7 33 2 49 17 34 1

25 104 1

9

Africa Algeria Morocco Namibia South Africa Tunisia Zambiah

206 I 79 18

Oceania Australia

52 1 521

Americas Argentina Bolivia Brazil Canada Honduras Mexico Peru United States

950 12 23 0 183 4 141 225 362

100

0 8

20 54 14 29 3 53 21 25 0 23 113 2 9 192 1 70 21 96 3

21 46 15

25 1 55 20 23 -

30 100

2 12

1996 363 -

28 -

3 8 45 12 27 2 54 19 18 24 99 2 22

-

189 1 74 20 89 5 -

487 487

424 424

475 475

979

1047 10 20 7 210 3 164 238 394

I IS5 11 16 8 257 5 172 249 436

1

10

20 1 171 3 170 233 370

186 1

68 22 88 7

Chapter 1

6 Table 1 Continued

Annual totals 1996

1995 Asia China India

1994 6.54 462 30

Iran 10 Japan Kazakhstan38 Korea, D.P.R. Korea, Rep. 2 2 (Burma) Myanmar Thailand Turkey Uzbekistan19 Other CIS World total Monthly average 226 Western world 2004 Monthly average

1993 632 338 30 15 17 104 70 7 2 S

819 643 35 16

14

18

8 28 S5 21

7

11

10

30 3

1

27 2700 225 2019 I68

10

250 2159 167

Note: Lead content by analysis of lead ores and concentrates ores and concentrates known to be intended for lead recovery. "Prior to 1993, data refer to Czechoslovakia. hContent of ore hoisted.

7 520 34 16 10 40 S0

40

4

4

S 12

2

10 12 1

IO IO

300 2754 230

1

2000 167

2

l80

plus the lead content of other

sian Federation. The principal lead mines in China are the Fdnkau Mine in Guangdong, Mengru Lead/Zinc Mine in Yunan, Changba LeadIZinc Mine in Gansu, Lijiagou Mine in Gansu, QiandongshanMine in Shaanxi,and Hunan Mine in Hengyang. The major lead mine in Thailand is located in Song Toh, 250 km northwest of Bangkok. The major lead mines in India are Rajpura-Dariba Mine and the Zawar Minegroup in Rajasthan. The major lead mines in Japan are at Kamioka in Gifu Perfecture and Toyoha in Akita Perfecture. In Africa, the major mines are located in Bou Jaber (Fedj Hassen Mine) and Bougrine (Tunisia), Black Mountain (South Africa), and Tuissit, Zeida, and Marrakech (Morocco).

II. REFINED LEAD PRODUCTION AND CONSUMPTION PATTERNS

Summaries of the world production ofrefinedlead and lead consumption patterns around the world are presented in Tables 2 and 3. The United States,

Introduction Table 2

7

RefinedLead:MetalProductioninThousands

of Tons [ I ]

Annual totals 1993

1994

I995

I996

I806 21 112 60 23 2.59 334 10 198 22 23 65 8 18 45 12 62 82 6 20 416 6

1839 16 I23 62 25 260 332

1826 23 122 72 22 297 3 l4

I830 24 121 74 22

Africa Algeria Kenya Morocco Namibia Nigeria South Africa Zimbabwe

1 54

135 6 2 64 24 4 32 3

141 7 2 62 27 8 32 3

131

Americas Argentina Brazil Canada Colombia Mexico United States Venezuela

1870 28 67 217 3 256 1196 14

1915

2059 28 50 28 I 4 230 1358 16

2 142 28 39 309

Europe Austria Belgium Bulgaria Czech Republic France Germany Ireland Italy Macedonia Netherlands Poland Portugal Romania Russian Federation Slovenia Spain Sweden Switzerland Ukraine United Kingdom Yugoslavia ER.

7 2 72 31 5

32 3

10

I1

223 21 24 63 13 21 34

189 22 21 70 8 23 30 14 82 83 7 14 387

15

75 83 6 9

416 4

25 64 252 3 214 I249 16

II

30 l

238 12 210 24 22 70 6 19 30 13

91

84 7 21 406 30 8

2 62 19

5

32 3

10

222 141I 25

Chapter 1

8

Table 2 Continued Annual totals

Asia

China India Indonesia

Iran Israel Japan Kazakhstan Korea, D.P.R. Korea, Rep. Malaysia Pakistan

Philippines Saudi Arabia Taiwan, China Thailand Turkey U.A.E.

Oceania Australia New Zealand World total

I993

I994

I995

1996

1401 412 51 35 35 7 309 245 65 128 29 3 23 31 17 4 4

1341 468 70 30 31 8 292 I45 50 130 33 3

1475 608 66 30 30 8 288 93 45

IS28 706 67 30 30 8 287 69 40 141 36 3

17 36 17 4 4

18

6 36 19 4 4

41 18 12 4

24 I 236 5

242 236 6

243 237 6

234 228 6

5472

5472

5744

5865

181

33 3

18 15

Note: Excludes secondary lead recovery by remelting alone

China, Canada, the United Kingdom, France, Japan, Germany, Australia, Mexico, Belgium, South Korea, Spain, and Sweden account for 73% of world production of refined lead. The United States alone accounts for 25% of the world production. The world refined lead production levels in 1997 and I99X were 6.0 and 5.96 million tons respectively. The Doe Run Co. accounts for nearly 100% of primary lead production in the United States. Both companies employ sintering/blast furnace operations at their smelters and pyronietallurgical methods in their refineries. Domestic mine production in 1992 accounted for over 90% of the U S . primary lead production; the balance originated from the smelting of imported ores and concentrates. Secondary lead production made up about 77% of the lead produced in the United States in 1996 versus 54% in 1980 (Table 4). The amount of sec-

6

Introduction

9

Table 3 RefinedLead:MetalConsumptioninThousands

of Tons [ l ]

Annual totals 1995

1994

Europe Austria Belgium Bulgaria Czech Republic" Denmark Finland France Germany Greece Hungary Ireland Italy Netherlands Poland Portugal Romania Russian Fed. Slovenia Spain Sweden Switzerland United Kingdom Yugoslavia ER.

1993 1813 62 74 25 23 2 4 226 352 6 8 23 238 48 59 26 20 92 11

102 24 4 353 5

1878 64 65 20 18 4 5 237 354 7 8 28 25 1 58 55

34 16 103 13 112 31 8 355

1970 65 69 19 27 4 3 263 360 8 12 25 27 1 62 55 34 19 93 14

1979 58 53 17 32 7 4 255 342 8 12 27 268 57 62 34 22 95

131

137 41

36

15

IO

IO

355

5

8

368 12

Africa Algeria Egypt Morocco Nigeria South Africa Tunisia

108

1IO

112

1 l9

18 7 6

18

19

6

6 9 5 60 5

20 9 7 5 63

Americas Argentina Brazil Canada Colombia Mexico Peru United States Venezuela

1760 33 75 70

7

5

5

59

59 5

3

II

I57 13 1367 27

1925 33 85 73 8

1976 30

5

2087 31 105 63 10 141

161

92 71 9 134

13 1513 28

IO

IO

1592 28

1687 30

Chapter 1

10

Table 3 Continued

Annual totals 1996

Asia

China India

Indonesia Iran Japan

Kazakhstan Korea D.P.R. Korea, Rep. Malaysia Pakistan Philippines Singapore Taiwan, China Thailand Turkcy Oceania 82 Australia 78 New Zealand World total

1995 I993

1994

147 I 300 70 75 60 370 30 40 20 1 51 X 32

1 507 290 90 91 60 345 20 36 233 53 X 25

8

IO

117 48 37

121 62 35

1726 445 96 90 67 334 15 35 272 66 X 27 12 I32 63 34

4

81 77 4

67 62 5

71 67 4

6045 52195865

1789 470 1 04 x7 70 330 12 32 290 75 9 26 13 I24 x0 35

5 502

N o f c : The consumption of retined lead. including the Iced content of nntlrnonial lead regardless 1.e.. whether ores, concenlrrrles, lead bullion, alloys. of source material from which produccd, resdues, slag. or scrap. Pig lead and Icnd alloys wlthout undergoing further treatment before reuse are excluded. "Prior to 1993, data refer to Czechoslovakia.

ondary lead produced was 698 X 10' tons in 1988, 888 X I O3 tons in 1990, and 1085 X 10' tons in 1996. The leading secondary lead producers include GNB Battery Technologies (Atlanta, GA), Exide Corporation (Reading, PA), and RSR Corporation (Dallas, TX). In Canada, the leading refined lead producers are Cominco, Hudson Bay Mining and Smelting Co. Ltd. (Minorco), Brunswick Mining and Smelting Co. Ltd. (Noranda), and Anvil Range Mining Co. Secondary lead accounts for about 37% of refined lead production in Canada. In South America, major lead producers include CENTROMIN in Peru and PenBIes and Empresas Frisco in Mexico. In the United Kingdom, the major lead producers are Brittania Refined Metals Co., MIM Holdings,

Table 4

Recovery of Secondary Lead in Thousands of Tons

[l]

Annual totals retined lead and lead alloys" I995

1994

1993

Europe Austria Belgium France Germany" Greece Ireland Italy Macedonia Netherlands Portugal Slovenia Spain Sweden Switzerland United Kingdom

808 14 25 146 160 4 10 93 3 23

885

8

13 1.5

12 62 38 6 204

Africa Morocco South Africa Other

51 3

Americas Argentina Brazil Canada Mexico United States Venezuela Other

IO64 16 39 69 60

Asia India Japan Korea, Rep. Taiwan, China Other

315

Oceania Australia New Zealand

32 16

86 1

14 5

939 24

4

925 23 30 168 I64 4

IO

11

128 3 24

126

12 144 4 22 6

16 26 155 1S6

75 43 6 21 I

5

21 8

14 82 41 7 22 1

49 3 32 14

S4 3 32

1137

1236 26 40 104 60 984 16

18

40 99 60 898 16 6

19

6

31

163 I 50 S

13 91

42 7 225 S3

4 32 17 1362 25 39 I 15

60 1085

25 13 404 25 I47 52 16 164

97 43

332 24 1 10 43

15

17

16

142

138

147

27 22

30

5

31 25 6

26 4

28 24 4

Total

2265

2434

2625

2786

Totalrecovery

2654

2829

3026

3185

18

380 26 140 51

"Retined lend and lend alloys (lead content) produced from secondary materials (scraps. wastes and residues). "Dataprior to 1991 include the former Federal Rcpublic only. 'Recovery of secondary mnteriul by renlelting wilhout undergomg further treatment.

11

12

Chapter 1

and Biliton (U.K.). About 55% of lead produced in the UnitedKingdom comes from secondary lead. Major lead producers in Europe include MetaleuropWeser Blei GmbH,Berzelius Metallhiitten GmbH, and Norddeutsche Affinerie in Germany, Societe Miniere et Metallurgique de Penin Italy, Boliden naroyyaS.A. in France,governmentownedEnirisorse Mineral AB in Sweden, and Metallurgie-Hoboken-Overpelt SA (Union Minere) in Belgium. In Italy, 68% of lead production comes from secondary lead, whereas in France and Germany, secondary lead accounts for about 54% and 6370, respectively. Mitsui Mining and Smelting Co., Mitsubhishi Mining and Smelting Co., Sumitomo Metal Mining Co., and Hosakura Mining Co. are the major lead producers in Japan and secondary lead makes up 5 1% of lead produced in Japan. Other major producersin Asia include Korea Zinc Co. in South Korea and the government-owned Hindustan Zinc Ltd. in India. In Australia, the major lead producers are MIM Holdings, GSM, Pasminco, Aberfoyle, and Biliton. Table 4 provides a summary of the secondary lead component of refined lead in different countries. The data show that the secondaryleadcomponent inlead productionhasbeen steadily increasingworldwide and currently slightly over half (53%) of the lead produced in the world comes from secondary sources. World consumption of lead grew steadily through the mid-1980s at a rate of 3-4% until 1989. The consumptiondecreasedbetween1989and 1993 and was followed by steady growth at 5 % per annum to a level of about 6 million tons. Consumption in the United States followed a similar trend. With the opening of the Communist Bloc production to Western markets in 1989, there was a change in the lead supply situation. The Communist Bloc exported 180,000 tons to the West in 1993, as opposed to a net import of 140,000 tons of lead in 1980. This dramatic change in the market/supply situation impacted on the price of lead. During 1987-1997, the price range for lead ranged from 20 to 40@/lband typically about 25@/lb [ 121. Longterm trends in the price of lead are dependent on the overall world economy as well as on the investments in industrial infrastructure in the former Communist Bloc and Asian economies. The primary market for lead at this time is in energy storage batteries followed by the chemical and cable sheathing applications. In Table 5, consumption patterns of major lead users are provided. The future use of lead may be decided by the resolution of environmental concerns. Some markets for lead are declining or being phased out due to environmental concerns, whereas other segments are growing and newer marketsare being developed. In 1990, the state of California (United States) required that 2% of new cars by 2003. meetzero-emissionstandards in 1998, 5% by 2001,and10% in New York, Massachusetts, and Similar laws were subsequently enacted seven other eastern U.S. states [ 13,141. In 1996, the California Air Resources

13

Introduction

Table 5 Production and Consumption Patterns and Consumers [ I ]

I996

I995

1994

of Major Producers

1993

France Refined lead Production Primary Secondary Consumption Principal uses Batteries Cable sheathing Sheet/strip Ammunition Alloys Gas. additives Oxides Miscellaneous

259 1 l3 146 226 244 156 16 19 8 4 5 24 12

260 138 105 163 155 255 237 254 170 14 17 8

Germany Refined lead Production Primary Secondary Consumption Principal uses Batteries Cable sheathing Pipe/sheet/shot Chemicals Gas. additives Alloys Miscellaneous Italy Refined lead Production Primary Secondary Consumption Principal uses Batteries Cable sheathing Pipe/sheet Ammunition

24

30 297 129 168 263 279 192 14 18 7 5 6 27

11

IO

334 174 160 352 362 204 9 50 80 2 8 9

332 176 156 150 354 342 378 333 216 194 8 8 49 57 66 77 3 3 9 8 8

3 l4

198 105 93 238 236 107 34 12 24

223 210 66 95 128 25 1 234

5 5

115

27 12 22

1

150

238 88

164 360 360 207 8 54 73 3 8 7

5

189 63 126 27 1 247 125 27 11

24

144

268

14

Chapter 1

Table 5 Continued ~

1996

1995 Alloys Gas. additives Oxides Miscellaneous

Japan Refined lead Production Primary Secondary Consumption Principal uses Batteries Cable sheathing Pipe/sheet Chemicals Alloys Miscellaneous United Kingdom Refined lead Production Primary Secondary Consumption Principal uses Batteries Cable sheathing Pipe/sheet Shot Tetraethyl Chemicals Alloys Miscellaneous United States Refined lead Production Primary Secondary Consumption

1994

1993 3 4 42

40

4 4 42

10

10

10

309 212 97 370 37 1 256 7

292 182

288 148 I40 334 334 232 4

287 140 147 330 330 233

11

12 41

10

3 5

I 10

345 346 239 5 10 51

59 14 25

13 28

416 212 204 353 299 103 9 84

416 205 21 1 355 303 100 9 94

46 12 29

387 166

22 1 355 328 109 10

102 6

6

I1

27

406 181 225 368 316 107 9 94

3

5

39 18 21 22

32 18 22 23

35

19 23 24

38 18 20 25

I l96 335 86 1 1367

1249 3s 1 898 1513

1358 374 984 I592

141I 326 1085 1687

5

introduction

15

Table 5 Continued

1996

I995

Principal uses Batteries Cable sheathing Pipe/sheet Chemicals Ammunition Alloys Gas. additives Miscellaneous

1994

1993 1599 1356 6 30 62 71 47

l68 1 1412

17 27 64 65 44

1450 I223 16 25 63 62 43

18

18

27

31

1286 105 1

7

37 67 58

69

Boarddecided not to mandate the introduction of zero-emissionvehicles and let the auto companies voluntarily sell zero-emission vehicles from 1998 to 2002. The auto industry committed to reach a goal of 10% of the vehicles sold to be zero-emission vehicles in 2003. Zero-emission vehicles are generallyaccepted to mean electric (i.e., battery-poweredcars) and there is considerable research efforttobringsuitableelectricvehicles to market. Although many battery systems are being investigated for powering electric vehicles, the lead-acid battery is by far the most mature and accepted. If lead-acid battery technology is adopted, the demand for lead is expected to increase strongly. The established world resources of 7 1 X 10' tonscan meet the demand for electric vehicles for a long time. In addition, seismic protection and damping applications are also likely to increase.

111.

PRODUCTION OF LEAD METAL

Lead is processedfromore to refined metal in fourstages:oredressing, smelting, drossing, and refining [2-41. The ore-dressing step involves crushing (jaw or gyratory crushers), grinding (rod mill or ball mill or autogenous), and concentration (gravity or froth flotation). Crushing and grinding are done so as to physically liberate galena and other minerals from the interlocking unwanted waste rock or gangue. The mineral ground to smaller than 0.2 the gangueusing gravity mm is separated in the concentrationstepfrom concentrators or froth flotation. Froth flotation is generally used for sulfide ores. The fine slurry is mixed with frothing agents and collector agents and air is pumped through the solution. The collector agent adsorbs to the surface of the mineral, making the particle hydrophobic, and causes the particle to attach to the air bubble and raise to the froth. Frothing agents such as pine

16

Chapter 1

oil, cresylic acid, polyglycols, and long chain alcohols which stabilize the froth are used along with collectors such as xanthates. The concentrate is obtained by skimming the froth from the cell, dewatering by settling, and vacuum filtering to a moisture content of 15%. The lead concentrate would typically have, by wt.%, 45-75 Pb, 0-15 Zn, 10-30 S, 1-8 Fe, 0.1-2 Sb, 0-3 CaO, 0-3 Cu, 0.5-4 insolubles, and small amounts of Au, Ag, As, and Bi. The concentrate is then smelted using a sinter-blast furnace or Imperial smelt process. In sintering and smelting steps, Pb and other metal sulfides are reduced in a series of steps. Before being fed in to the blast furnace, the concentrate is roasted to remove most of the sulfur and to agglomerate further the fine products so that they will not be blown out of the blast furnace. In this step, the concentrate is mixed with coke and fluxing agents such as limestone or iron oxide, and spread on a moving grate. Airis blown through the grate at a temperature of 1400°C. Sulfur along with coke that has been addedservesasfuel, and the sulfurdioxideformed is recovered for the production of sulfuric acid. The roasting results in a sintered brittle product containing oxides of lead, zinc, iron, and silicon along with lime, metallic lead, and the remaining sulfur. The sinter is broken into lumps as it comes off the moving grate. The prefluxed sinter lumps are loaded on top of the blast furnace along with coke fuel. The blast of air admitted to the bottom of the blast furnace aids the combustion of coke, generating a temperature of 12OO"C, and the carbonmonoxideproducedreduces the metaloxides, producing molten metal and carbon dioxide. Nonmetallic wastes form a slag with the fluxing materials. Typical composition of the slag is, by wt.%, 2533 FeO, IO- 17 CaO, 20-22 SiO,, 1-2 Pb, and 13- 17 Zn. Some lead is trapped in the slag also and this is kept to a minimum. The molten metal is tapped into drossing kettles or molds. The liquid metal containing 95-99% lead and dissolved metallic and nonmetallic impurities is referred to as the base bullion. In addition to noble metals, base bullion contains the impurities Sb, As, Sn, Cu, and Bi. Copper sulfide has a lower solubility in lead and, therefore, some of it is removed as matte (molten sulfide layer). If Sb or As is present, Fe and Cu could react with them to form arsenate or antimonides and removed as a speiss layer (consisting of antimonides and arsenates and having a density of -6). Several new commercialsmeltertechnologieshavebeendeveloped, including KIVCET, Isasmelt, and QSL processes but the sinter-blast furnace and Imperialsmeltfurnace are still widely used [3,4,15]. These new processes are direct smelting processes carried out in relatively small, intensive reactors. These processes require neither the sintering of feed materials nor the use of metallurgical coke. They also produce lower volumes of gas and dust that would require treatmentwith pollution-control equipment.The

Introduction

17

KIVCET and QSL processes consist of a single furnace, and unifyin a single structure all phases of desulfurization and reduction of lead oxide into lead bullion. KIVCET is a Russian acronym for “flash-cyclone-oxygen-electricsmelting.” It employs the autogenous (i.e., fuelless) flash smelting of raw materials, with the heat-producing oxidation of the concentrated sulfide ore raising the temperatureto 130O-140O0C, which is enough to reduce the oxidized materials to metal. The process involves the proportioning, drying, and mixing of the lead-bearing materials and fluxes, followed by their injection into the reaction shaft. The injected materials are ignited by a heated blast of commercially pure oxygen. The smeltedlead bullion and slag collect in the hearth while zinc vapor undergoes combustion with carbon monoxide in the electric furnace to produce zinc oxide. Hot sulfurous gases generated by the smelting process are used to produce steam and sulfuric acid as byproducts. TheKIVCETprocessappears to produce significantly less flue dustthanother direct processes,and its furnacebrickworkhasalonger service life. The QSL (Queneau-Schuhmann-Lurgi) process can handle all grades of lead concentrates, including chemically complex secondary minerals. A pelletized mixture of concentrates, fluxes, recirculated flue dust, and a small amount of coal is dropped into the melt consisting mainly of primary slag in a refractory-lined reactor. Oxygen is blown through tuyeres at the bottom to oxidize the unroasted charge in the molten bath at a temperature of 1000- 1 100°C to produce metallic lead, primary slag with as much as 30% lead oxide, and sulfurous off-gas. The primary slag is reduced via coal injected into the second section of the furnace through submerged tuyeres. In the Isasmelt process, an air lance is brought in through the top of a furnace and its tip is submerged in the melt containing the sulfide concentrate. A blast from the lance produces a turbulent bath in which the concentrates are oxidized to produce a high-lead slag. This slag is tapped continuously and it is reduced with coal. Crude lead transferred to a second furnace, where and slag are tapped continuously from the second furnace and separated for further refining. The final stage is the refining of lead when the impurities are removed to meet the standards for commercial sale and to recover valuable by-products. The impure bullion is cooled so that most of the copper segregates in the kettle due its low solubility in lead at temperatures just above the melting point. The dross that contains Cu is skimmed off along with the remaining CO, Ni, and Zn. The rest of the Cu is removed by treating it with S (10 kg/ ton) (at Cu levels of <0.01%) as sulfur reduces the solubility of copper in molten lead even further. The melt is then brought to a temperature of 700750°C in a reverberatory furnace or kettle and air or steam is blown in over the surface. The elements Sn, As, and Sb are oxidized before Pb and carried into scum, which are skimmed off for recovery later. This step is referred

Chapter 1

18

to as the “softening” step, as it removes As, Sb, and Sn that harden lead in solid state. The elements that still remain after the softening step include Ag, Au, Cu, Te, and Pt metals. The Parkes zinc desilvering process is then used for Ag removal. In this process, 1-2% Zn is added to molten lead in desilvering kettles. With stirring, the molten zinc reacts to form intermetallic compounds with gold and silver. The compounds are lighter than lead, and on cooling to below 370°C but above the melting point of lead, they form a crust that is removed and processed for the recovery of the precious metals. The remaining zinc is then removed by reheating the molten lead to 500°C and creating a vacuum over the surface. The Pattinson process, which is now rarely used and replaced by the Parkes desilverizing process, depends on lead being cooled slowly, allowing part of it to solidify. The solidified part is skimmed off and the silver will remain in the molten lead left behind.Pattinsonlead is similar to Parkes lead but the production process is more intensive. A typical composition of Pattinson lead would be Pb-0.068 wt.% Cu-0.002 wt.% Ag-0.032 wt% Bi0.001 wt.%Sb-0.0005wt.%Cd-0.02wt.%Sn-0.001 wt.% TI-0.001 wt.% Fe. The Harris process of softening and dezincing is designed to remove impurities from desilvered lead by stirring a mixture of molten caustic salts at atemperature of 450-500°Cintothemolten lead. Metallicimpurities react with the chemicals and are collected in the form of their oxides or oxysalts. Bismuth removal from lead can be achieved by treatment with Ca and Mg. Bi forms a compound, CaMgzBiz, that has a low solubility in lead. The limits ofBi after this step is <0.005%. Use ofNa could reduce this to a 0.001% level. Electrolytic refining oflead can also beused when lead of high purity is required or when purifying lead with a high Bi content. The lead thus obtained from the above treatments is 99.9-99.99% pure. Double electrolysis can be used to make lead of 99.9995% purity. Zone melting also can be used to produce ultrapure grades of Pb.

IV.

HEALTH AND SAFETY ISSUES

Inmostof the applications in which the use ofleadis increasing andin which lead is expected to be used, the lead and its alloys haveminimal contact with the user. The lead i n these applications is expected to be recovered for recycling. However, the users must be aware of health effects of lead absorption in the body.

Introduction

19

Lead enters the body through inhalation and ingestion. It is absorbed into the circulatory system from the lungs and digestive tract, and excreted via the urine and feces. The intake of lead approximately equals output, but excessive exposure and intake can lead to increase in tissue concentrations and illness. A chronic exposure (exposure to excessive amounts of lead over alongperiod of time)could affect the blood,nervoussystem, digestive system, reproductive system, and kidneys. Such effects include anemia, muscularweakness,kidneydamage,andreproductiveeffects that involve reduced fertility in both men and women and damage to the fetus of exposed pregnant women. Symptoms of chronic lead poisoning include fatigue, headache, constipation, uneasy stomach, irritability, poor appetite, metallic taste, weight loss, and loss of sleep. As many of these symptoms also occur in many common illnesses, physicians should be consulted and periodic blood tests andscreening is requiredfor lead workers.Proper ventilation, good work practices, following rules of good hygiene, and wearing respirators and protective gloves help control exposure to lead. Lead in the environment is regulated in different parts of the world because of its potential occupational impact, as well as concern about the impact lead may have on the cognitive and physical development of young children. Standards have been set for lead in air, water, and other environmental media. In the United States, Part 1910 of Title 29 of the Code of Federal Regulations provides information on regulationsby the Occupational Safety and Health Administration (OSHA) and other U.S. agencies govemingoccupationalexposure to lead. Chapter5discusseshealthand safety issues and the regulatory standards governing the use and exposure to lead.

V.

PROPERTIES OF PURE LEAD

Lead has an atomic number of 82 and belongs to Group 14 (IVA) of the periodic table. Ordinary lead is bluish gray in color. It consists of a mixture of isotopes of mass numbers 204, 206, 207, and 208. The stable isotopes of lead are products of decay of three naturally radioactiveelements: '"hPb comes from the uranium series, 20XPbfrom the thorium series, and ""7Pbfrom the actinium series. Depending on the origin of lead, the relative abundance of the different isotopes vary. Ordinary lead consists of 15% ""Pb, 23.6% "IXPb, 22.6% '07Pb, and 52.3% roxPb [4,16]. The average atomic weight is 207.21 t- 0.04. The crystal structure of lead in solid form is face-centered cubic (fcc). The lattice parameter of 99.999% pure lead is 4.95008 t 0.0001 at 20°C [17]. Excellent ductility of lead at room temperature is mainly derived from low the fcc crystal structureand the lowmelting point ( T M ) .Leadhasa

A

20

Chapter 1

melting point of 327.3”C at 1 atm pressure. The density of electrolytic lead at 25°C is 1 1.3307 g/cm’ [ 181. For radium lead from uranium ores, which hasa greater proportion of lower-atomic-weightisotopesandanaverage atomicweight of 206.3, the density is 11.288 g/cm.’ [19]. The theoretical density based on the lattice parameter data for 20°Cand a perfect lattice is 11.345 g/cm’, which is higherthanexperimentallymeasuredvalues, suggesting a significant vacancy concentration at room temperature. The vacancy concentration near the melting temperature is about 2 X at.% [20]. The density of molten lead at melting point is 10.785 + 0.0173 g/cm’ [2 I 1. The experimental value for the velocity of sound, or longitudinal elastic waves, in lead is 1560 m/s [22]. The theoretically calculated value from ( E ) anddensity (p) data,using the formula U = the elasticmodulus is 1212.5m/s,which is aboutone-fourth of the value for steel. The values of the Young’s modulus, shear modulus, and compression modulus for polycrystalline lead are about 17, 7.8, and 43.3 GPa, respectively [23-251. The Poisson’s ratio is 0.44 [23]. These elastic properties coupled with a high density make lead an attractive material for damping and acoustic barrier applications. The damping for very pure lead expressed as a loss of energy per half the vibration period divided by the potential energy of the system is about lo-’. This corresponds to a natural logarithmic decrean extremely low value [26]. The natural logarithmic ment of 5 X [27].Theotherphysical dampingconstant for cast lead isof 4.57 X properties of lead and lead alloys that are of engineering interest include density, thermal expansion coefficients, specific heat, elastic properties, melting point, boiling point, vapor pressures, surface tension, thermal conductivity, electrical conductivity, damping coefficients, and magnetic and acoustic properties. A summary of key data on pure lead are given in Table 6. Other data are presented in later chapters. The different properties of interest are improved by alloying additions and heat treatment. The nuclear stability under neutron bombardment, high absorption coefficient for gamma radiation, and ease of fabrication has made lead a very valuable material in nuclear radiation shielding applications. The density and low stiffness makes it attractive for damping and acoustic barrier applications. Its ability to form low-melting-point alloys makes it very attractive in it Valsolder applications. Its outstanding electrochemical behavior makes uable in battery applications. Its density and low stiffness makes it attractive as an efficient sound-barrier material, whereas its ductility and IOW stiffness makes it valuable in seismic protection. Its resistance in manychemical environments has made it valuable in the chemical industry. An attempt is made here to present comprehensive information on different aspects of lead and lead alloys used in the above-mentioned and other engineering appli-

m,

Introduction

21

Table 6 Physical Properties of Lead ~

Property

Ref.

Bluish gray Color 82 Atomic number face-centered cubic Atomic arrangement 207.22 Atomic weight ?"lPb, 2'WPb, z"5pb, mPb, Isotopes ?07pb, ?(lxpb,?("pb, ?l"pb Common lead is considered to be a constant mixture of isotopes of 207.22 atomic weight. 18.27 X 10 '(I m' Atomic volume at 20°C calc. Density ( X 10' kg/m') 11.1005 Ordinary lead, 327°C (solid) 10.686 327.4"C just liquid 10.686 350°C 10.597 400°C 10.536 450°C 10.477 500°C 10.359 600°C 10.245 700°C 10.132 800°C 1 1.35- 1 1.37 Rolled sheet, 20°C 11.34 Pure cast lead, 20°C 327.4"C Melting point Rate of change of melting point with increase of pressure 0.08 K/MPa 15-200 MPa 0.068 K/MPa 800-1200MPa 0.054 K/MPa 2000-3000 MPa 1,740"C Boiling piont 23 kJ/kg Latent heat of fusion 4.744 kJ/mol Latent heat of fusion, per mole 66 kJ/kg Heat required to heat lead from 20°C to melting point 860 kJ/kg Latent heat of vaporization Elastic properties of single-crystal lead: . . S,,, the compliance tensor in contracted notation, in lo-" m'/N. E, = S p , c,,,elastic stiffness coefficients in contracted notation, in 10"' Pd. cr, = c,,&, Shear modulus = C,,. If material is isotropic, C,., = '/? ( C , , - c,?)

-273 20

6.75 9.3

-3.1 -4.26

5.28 6.94

7.22 10.1

6.7 4.83

5.7 4.09

2,223 2,16,28 2,17 2,16,28 16

17 28,29

28 28 23

30 31 31 32,33 34 34 28 34 35

1.89 1.44

22

Chapter 1

Table 6 Continued Property Elastic properties of polycrytalline lead Young's Modulus at room temperature Compression modulus ( 1 atm, 20°C) Shear modulus Poisson's ratio Yield point Velocity of sound in liquid lead Natural logarithmic damping decrement for cast lead Loss of energy per one half vibration period/potential energy of the system Logarithmic decrement Hardness, Moh's scale Thermal conductivity Temp. ("C) -

Ref.

16.6 GPa 43 GPa 7.81 GPa 0.44 880 kPa 1776 m/s 4.57 x 10"

23 25.36 35,37 2,23 38 39 27

1 x 10"

26

5 x 10"

26 28 28,40,41

1 .S

J/m

K

48.9 38.5 36.0 33.9 32.2 30.9 24.6 24.6 24.6

247

- 160

0 100 200 300 400 500 600 Thermal conductivity (silver = 100) Coefficient of linear expansion (- 190 to 19°C) Coefficient of linear expansion (17-

S

8.2 IO"'/K

28 42

26.5

X

29.3

X

10-"/K

42

12.9

X

10. "/K

43

I00"C) Coefficient of volume expansion (liquid at melting point to 357°C) ( 1 7- 100°C) calculated Increase in volume from 20°C to liquid at melting point Decrease in volume on solidifying Increase in volume on melting Shrinkage on casting taken in practice Shrinkage in volume calculated from liquid at melting point to 20°C

87.9 x 10-6rK 6.1% 3.85% 4.01% 0.9-2.6% 5.80%

28 28 28 28 28 28

Introduction Table 6

23

Continued

Property Recrystallization temperature Self-diffusion coefficient In single crystal, IO-’ m’/s In polycrystalline lead D,;,,,,,,, 10-(’ m’/s D,,, IO-‘ m’/s Specific heat of lead Temp. (“C) - 150 - 100

-50 0 50 100

300 327.3 (solid) 327.4 (liquid) 378 418 459

Ref.

28

=

-33°C

0.28 1 exp( - 24.2 IO/RT)

44

1 17 exp( -25,7OO/RT) 45 8 1 exp( - 1 S,700/RT)

Specific heat (J/kg K)

28,34

1l7

121 123 126 128 132 I42 150

I40 I42 140 140

Vapor pressure Temp. (“C)

808 1000

1200 1365 1525 1870 2100

Pressure (torr)

46

0.08 1.77 23.29 166 760 4788 8892

Surface tension Temp. (“C)

327.3 (solid) 350 400 500 600 800 1000

10” N/M

700 460 445 434 425 416 410

14 14 -+ 14 t 14 2 14 % 14 %

2

2

24

Chapter 1

Table 6 Continued Property

Ref.

210

Grain boundary energy Viscosity Temp. ("C)

47 P

350 400 450 500 550 600

48

2.648 2.315 2.057 1.850 1.681 1 S40

Magnetic susceptibility, (g")

18-300°C 300-600°C Specific electrical conductance at 0°C at 18°C at melting point Temperature coefficient of electrical resistivity 28 Relative electrical conductance (copper = 100) Relative electical resistance (copper = 100) Electrical resistivity

-12 x lo-" -0.08 x 10-l'

28.49 28

5.05 X IO' cm"ohm I 4.83 X IO' cm-' ohm-.' 1.06 X IO4 cm" ohm" (4.1-4.3) X 10 'PC

28

7.82 1280 IACS units

28 28

Temp. ("C)

6.02 14.1 20.4 28.0 36.9 94.0 107.2

- 183.0

-78.0 0

90.4 196.1 318.0 600.0 Electrochemical equivalence Valence 1

2 4

c/g

g/A , h

465.7 93 1.4 1862.8

7.7302 3.865 1 1.9326

28

Introduction Table 6

25

Continued

Property Electrolytic solution pressure Ions of Pb'* Ions of Pb" Potential of lead electrode With normal calomel electrolyte With normal hydrogen electrolyte On absolute scale Thermoelectric potential against Pt

Ref.

28 6.3 Pa 3.0 x lo-"' Pa 28 0.415 V 0.132 v 0.145 V 0.44 mVPC

28

cations. In Chapter 2, data on the physical properties, mechanical properties, corrosion properties in different environments, acoustic properties, and nuclear properties are presented. Chapter 3 deals with the different forms of lead available and the fabrication processes used tomanufacture these shapes.Chapter 4 dealswith different engineering applications and the designconsiderations that make lead andlead alloys valuable in these applications.

This Page Intentionally Left Blank

Properties of Lead and Its Alloys

1.

PHYSICAL PROPERTIES OF LEAD AND ITS ALLOYS

Lead is commonly alloyed with other elementsso as to improve its physical, mechanical, or electrochemical properties. These elements will be in solid solution in the lead phase at levels below the solubility limit. At levels above the solubility limit, the solute elements may form intermetallic compounds/ in the second phaseswithleadandothersoluteelementsorbepresent terminal phase richin the solute element. At any given temperature, composition, and pressurecondition, different phasescancoexistunder thermodynamic equilibrium. The phases and their relative amounts under variand composition conditions are presented ous pressure ( P ) ,temperature (p, graphically as phase diagrams. The morphology and spatial distribution of the grains of the different phases, however, depend on the prior heat treatment or thermomechanical treatment. Excellent qualitative understanding of alloy phases exist today that allowprediction of phase stability starting from the consideration of the atomic structure of the constituent elements. The changes in the energy levels of electrons as the atoms are brought together to form a solid with a particular crystal structure can be calculatedand the energy of asystem estimated. A detailed treatment has been presented elsewhere [50,51]. Under a given set of conditions, one phase or a mixture of different phases will have minimum energy and will exist in stable equilibrium. The energy parameter that is used to determine the stability of a given phase of a specific chemical composition at a given temperature and pressure is the Gibbs free energy, G. G is a function of energy associated with the interaction between atoms (bond energies) and the thermal vibration of atoms, entropy associated 27

28

Chapter 2

with spatial configuration or arrangement of atoms, and distribution of energies among the different modes of vibration, pressureandtemperature. When alloying additions are made to lead, the solubility limits of alloying elements in terminal solid solutions and the tendency to form intermediate phases are influenced by the interactions between different alloyingadditions, and Pb atoms manifest as changes in bond energies and vibrational frequencies. Such interactions depend on the electronic structure of the alloying element atoms and lead atoms and are, therefore, influenced by the relative atomic size, valence, electronegativity, and e/a ratio (bonding electron per atom). The influence of atomic size, valence, and electronegativity were considered by Hoffman [ 2 ] when he examined the different binary phase diagrams of lead. He classified Pb binary phase diagrams into four groups as given below (Table 1). The atomic sizes assigned to an atom depend on the crystalline lattice it occupies and the nature of bond [52].The atomic sizes indicated in Table 1 correspond to that in a metallic face-centeredcubic (fcc) lattice with a coordination number 12.

Table 1 The Atomic Sizes in Coordination Number 12 of the Different Elements Used in the Alloying of Lead 121. (Courtesy of Springer Verlag, New York.) Group I Element Atomic size

AI

CO

Cr

Cu

(A)

1.43

1.26

1.28

1.28

Fe 1.27

Group I1 Element Atomic size

Ag 1.44

As

Cd

Sb

Sn

(A)

1.48

1.52

1.61 1.58

Group 111 Element Atomic size

(A)

Au Ba K 1.44 2.25 2.36 1.57

Element Atomic size

(A)

1.82 1.97

Bi

Bi

(A)

1.82

Note: The atomic size of lead

Mn

Ni

Si

Zn

1.31

1.24

1.34

1.37

Mg Na Pd 1.60 1.92 1.37 1.38

Pt

Ca

La Ge Ce Element 1.39 1.86 Atomic size (A) 1.82 Group IV Element Atomic size

Li

Ga 1.39

Pr

S Sr Se -

Hg 1.55 IS

In 1.57

1.75 A.

1.7 2.16 1.6

Te

U -

Sn

TI

Pb

1.58

1.71

1.75

Properties of Lead and Its Alloys

29

Group I. Systems with miscibility gap in the liquid state but form no intermediatephases.Thisgroupconsists of metalswithsmallest atomic radii and mainly involves transition metals Al, CO, Cr, Cu, Fe, Ga, Mn, Ni, Si, and Zn. Group 11. Eutectic without intermediate phases. This group involves Cd, Sn, Sb, As, and Ag. Among these, Cd, Sn, and Sb have higher solubility in Pb compared to As and Ag. Group 111. Systems with intermediate phases. These can be grouped under the following systems: 1. Witheutecticon the lead side 2. With peritectic on the lead side 3 . With liquidus curve rising steeply from the lead side

Among these, the alkali and alkaline earth metals form intermediate phases with lead. Temperature-dependent solid solution in these alloys allows for age hardening of these alloys. Au, Pd, and Pt also formintermediatephases but havelimited solid solubility. Group VIAelements S, Se,and Te form intermetallic compoundsPbS, PbSe, and PbTe and show limited solubility in Pb. Group IV. Large solid solubility on the lead side. Systems with smaller difference in atomic size and electronegativities belong to this group. These include Bi, Hg, In, Sn, and T1.

A.

Phase Diagrams of Important Binary and Ternary Lead Alloys

Commercial lead alloys contain one or more of the elements Sb, Sn, Ca, Ag, Te, Cu,Cd,Li,In,Ba,Bi,and As as keyalloying additions. Other elements that maybepresentasalloyingadditivesinclude Ni, Na, Sr, S, and Al. Some of the important binary and ternary phase diagrams involving lead are presented below. 1.

Pb-Ag Alloys

Lead-silver alloys are of interest because of their high resistance to recrystallization and grain refinement and their high creep strength. Lead and silver [53,54].The phase form a eutectic system without any intermediate phase diagram of the Pb-Ag system (Figure 1) shows that the eutectic point occurs at acomposition of 2.5 wt.% Ag andatemperature of 304°C [53]. The maximum solid solubility of Ag in lead is obtained at the eutectic temperature and is 0.1 wt.%. The solubility drops to 0.05 wt.% at 200°C and 0.02 wt.% at 100°C. Solubility of Pb in Ag is also very low at room temperature.

30

Chapter 2

Figure 1 Pb-Ag phase diagram [2,53].(Courtesy of Springer Verlag, New York.)

However, supersaturated solutions containing up to 10 wt.% Pb in Ag have beenobtained by electrodeposition[55,56]. Ag formsametastable intermediate phase, Ag,Pb, around defects in quenched alloys with <0.026 wt.% Ag [2]. On aging with storage at room temperature, the alloy softens because of the decomposition of this phase. The large difference in atomic size of silver and Pb (Aula = -0.17) leads to low solid solubility and low values of diffusion coefficients. In solid solution, Ag provides for high resistance to recrystallization, as may be expected from the high activation energy for diffusion. Rolled alloys with0.1% Ag after heat treatment at 160- 180°C show fine grains similar to Pb-Te alloys [57,58]. The addition of silver leads to a marked increase in creep strength even at contentsbelow 0.005% in the purest electrolytic lead (99.9995%) [59]. The optimal effect occurs between 0.01% and 0.05% Ag and high creep strength is obtained more likely at 0.01 wt.% levels [58,60]. Leadalloyedwithsilvershows excellent resistance to sulfuric acid. Pb- 1% Ag alloy can be made into anodes with exceptionally good corrosion

Propertiesof Lead and Its Alloys

31

resistance over a broad range of current densities. Extruded or cast bars of this alloy are among the best possible insoluble anodes for electrolytically refining zinc and manganese. Lead anodes with 1% silver have long service of shipbottoms 1611. lives when used in the cathodicprotectionsystems Eutectic Pb-Ag alloys are used as soft solders of high melting point. Alloys with 1.5% Ag and 1 % Sn are used in high-melting-point solders. Another low-silver alloy (0.1%) is one of the best precoats used to metallurgically bond lead to steel. 2.

Pb-As Alloys

Lead-arsenic alloys are of interest in cable sheathing and in radiation protection applications. Arsenic has also been used as an additive i n antimonial lead for water pipes and storage battery grids. Figure 2 illustrates the phase diagram of the Pb-As eutectic system [2,53,62-641. The eutectic point occurs at acomposition of 2.8 wt.% As andatemperature of 288°C.The maximum solid ,solubility of As in lead is 0.046 wt.% at 288°C. The solid solubility of As in Pb at 50°C is 0.007 wt.%. During the melting of these In hypereutecticalloys, As alloys, arsenic loss occursthroughoxidation. crystals that form during cooling through the two-phase region have a tendency to rise. This segregation can be suppressed by faster cooling at As contents less than8%. Brinell hardness increases withincrease in arsenic content. Maximum hardness is obtained on quenching when a supersaturated solid solution of As in Pb is obtained. Subsequent storage at room temperature leads to softening as As is precipitated [63]. The density of Pb-As alloys decreases from 11.34 g/cm3 at 0% As to 10.775 g/cm3 at 5 wt.% As. Shrinkage decreases from 1.02% for pure lead to 0.82% for 0.1-8% As alloys. Surface tension also falls with As content. Alloys with 0.85% As have very low volume shrinkage on solidification and pore-free castings of Pb-As alloys can be obtained for radiation protection applications. The compressive strength of Pb-As alloys is not high and, in addition, they soften on aging at room temperature. Therefore, they are not used in type metal or bearing metal applications. Arsenic is generally added to lead, together with tin, bismuth, silver, or tellurium, to provide the resistance to bending and creep needed in power cables sheathing exposed to severe vibration. One such alloy contains 0.15% As, 0.1% Sn, and 0.1% Bi. Arsenic is also added to antimonial lead to accelerate age hardening.

3.

Pb-Ba Alloys

The Pb-Babinaryphasediagram is similar to the Pb-Cabinaryphase diagram (Figure 3) [64a]. The eutectic point isat 4.5 wt.% Ba and a temperature of 293°C. The eutectic phases consist of white needles of BaPb,

Chapter 2

32

0

327.502.C

3

l

(b)

5

0 1 Pb

2

As (at.%)

IO

3

Y

15

5

AS (wt.%)

6

8 Pb

AS (wt.%)

Figure 2 Pb-As phasediagram [2,53,62-641. (Courtesy of ASM International, Materials Park, Ohio and Springer Verlag, New York.)

and the lead phase.Themelting point of BaPb, is 617°C. The solubility limit of Ba in Pb is 0.5 wt.% at 130°C and decreases to 0.02 wt.% at room temperature. Thus, significant age hardening can be obtained, as is shown in Table 2 and Figure 4 [65]. The Brinell hardness increases from 4 to as high as 45.5 at a Ba content of 10.4%. Ba is very reactive and high-Ba alloys decompose in air. However, low-Ba alloys are not hard enough for

Properties andof Lead

Its Alloys

33

Pb (at.%) IO

0

80

30

40

60

50

80

70

90

IW

1000

Ba (at.%) f5

600

-500

E P

WO

E

I-" So0 zoo ~ fOO0

Pb

a+EaPb,p

~

2

~

5L

6

8

~

f O f 2 W

.

.

76

+

~

20

Ba (wt.%)

Figure 3 Pb-Baphasediagram [2,53,64a]. (Courtesy of ASM International, Materials Park, Ohio, and Springer Verlag, New York.)

"

w

Chapter 2

34

Table 2 BrinellHardnessAfter Quenching and Aging at Room Temperature for 35 Days (Determined from Figure 4) Wt.% Ba H,, (2 mm/l5.6 kg130 S) Aging time (days)

0.015

4.5 35

0.024 8.0 35

0.024 15.5

36

0.14 17.5 35

0.14 7 7

0.58 15

7

use as bearing metal. Ba is used as a secondary additive in age hardenable Pb-Ca alloys, where it results in an additional increase of hardness. These alloys are also used in radiation shielding applications.

4.

Pb-Bi Alloys

The atomicsize of Bi does not differ very much from that of lead. The negligible lattice dilation when Bi substitutionally dissolves in Pb leads to a very large solid solubility. For the same reason, the solid-solution hardening obtained with Bi addition is negligible. Bi at levels greater than 0.1% accelerates the recrystallization of lead, the effect becoming marked with increasing Bi content. This is consistent with the increase of interdiffusion coefficient with increasing Bi content. Although it accelerates recrystalliza(x9.81 MPa)

Storage time at 20°C (Days)

Figure 4 Hardnessversus ageing time for Pb-Ba alloys 12,651. (Courtesy of Springer Verlag, New York.)

Properties of Lead and Its Alloys

35

tion, no intense grain growth relative to pure lead is observed [2]. Whereas Bi addition has very little influence on mechanical properties, excellent wetting properties make Pb-Bi alloys very valuable as solders for glass-to-metal joints. Their desirable solidification shrinkage characteristics and casting properties that provide an ability to reproduce surface details make them useful in printing and prototyping applications. Molten Pb-Bi alloys are used for heat treatment and in other heat-transfer applications. Small additions are used in type metals and bearing metals based on Pb-Sb-Sn for improved casting properties. The phase diagram of Pb-Bi alloys (Figure 5 ) shows a large solid solubility of about 17.5 wt.% Bi in Pb at room temperature 153,661. The solubility at a temperature of 184°C is 23.5 wt.%. An eutectic reaction involving the intermediate @ phase and the Bi terminal phase occurs at a composition of 56.5% Bi and a temperature of 125°C. The p phase has an hcp structure. Both Pb and Bi have a low cross section for neutron absorption. Coupling this with the low melting points of these alloys had made these alloys attractive in heat-transfer applications in nuclear reactor systems. Lead contracts on solidification and Bi expands on solidification. A neareutectic alloy containing 55.9% Bi shows a minimum in contraction at 1.52 5 0.1% [67]. A slight grain-refining action is observed at 0.18 wt.% in alloys used for cable sheathing [681. At levels of up to 0.1 wt.% Bi, no significant difference in creep behavior is observed compared to 99.99915 wt.% lead [69]. Bi addition has minimal influence on corrosion in atmospheric, water, soil, and cold sulfuric acid. Up to a level of 0.05 wt.%, Bi has no effect on durability and selfdischarge of PbSb battery grids in storage batteries. At 0.5 wt.% Bi in Plante-type plates, Bi caused deterioration in dimensional stability and durability [70]. Bi decreases resistance to sulfuric acid attack at high temperatures and Cu compensates for Bi. Bi addition to alkaline-earthcontaining alloys is undesirable, as Bi removes Ca from lead. It may be recalled that during the purification of lead, the addition of Ca or Mg is used to form compounds with Bi that rise up to the surface and removed as dross and to reduce the Bi level (to 0.007-0.009 wt.% Bi by Ca addition and to 0.001 wt.% with Na addition).

5.

Pb-Ca Alloys

Lead-calcium and Pb-Ca-Sn alloys are of interest in pipe, wire, cable sheathing, anodes, storage battery grid, chemical-handling equipment, radiation shielding, and other applications. Ca is also used as an important secondary additive in hardened lead bearing metals. A peritectic reaction is observed on the lead-rich side in the Pb-Ca system at 3283°C (Figure 6) [2,53,71]. This reaction involves the molten

Chapter 2

36 Bi (at.%) 10

20

-100

Bi (wt.%)

Pb

Bi

Pb

Figure 5 Pb-Bi phase diagram [2,53,66]. (Courtesy of ASM International, Materials Park, Ohio, and Springer Verlag, New York.)

Pb-0.07 wt.% Ca phase and Pb,Ca, and results in the a-Pb phase containing 0.1 wt.% Ca. The solubility of Ca in Pb decreases to -0.01 wt.% at room temperature. At Ca contents greater than 0.07% Pb,Ca precipitates on solidification. Pb,Ca crystals have a cube or star shape and appear white on polishing and tarnish dark after etching. The crystal structure of Pb,Ca is similar to that of Cu,Au [72]. At higher Ca contents (>0.1 wt.%), the microstructure consists of primary crystals of Pb,Ca and a lead matrix with

Its Alloys

Properties andof Lead

37

Ca

Pb Ca (at.%)

a2

Ca (at.%)

if5

5-

1

Ca (wt.%)

010

2

25

I0

Figure 6 Pb-Caphasediagram [2,53,71]. (Courtesy of ASM International,Materials Park, Ohio, and Springer Verlag, New York.)

Chapter 2

38

finer Pb,Ca precipitates [73]. At these higher Cacontents, the two-phase structure leads to grain refinement. The density of Pb-Ca alloys decrease by 0.029 &/cm.' per 0.1 wt.% Ca addition [74]. A pronounced age hardening is observed in Pb-Ca alloys at all Ca levels. The amount of Ca in supersaturated solid solutions at room temperature depends on the rates of solidification and the rate of cooling in solid state after solidification. The maximum Ca content observed in supersaturated solid solutions obtained by rapid solidification is as much as 0.16 wt.% [ 7 5 ] , but, typically, it is about 0.13 wt.% in quenched alloys. The higher the Ca level, the greater is the hardness increase observed on aging at room or higher temperatures. The aging of the 0.07 wt.% Ca alloy at room temperature changes the Brinell hardness from 4 to a maximum level of 8.25 (10 mm/3 1.2 kg/l20 S) in 6 h (Figure 7). Electrical resistivity drops from 22.62.5 X to 22.2.5 X IO-" R.cm. The maximum in hardness for alloys quenched occurs at 0.13 wt.% and in air-cooled alloys at 0.085 wt.% [76]. No increase in hardness in cast alloys occurs above -0.1 wt.% Ca. In heattreated alloys as well, 0.1 wt.% Ca alloys show the maximum hardness. Secondary additions of other alkali and alkali earth metals Li, Ba, and Na increase the hardness. The addition of tin to a Pb-Ca-Sn alloy increases the hardness, ultimate tensile strength (UTS), and stress rupture properties. Additions of Sb and Bi decrease the hardness as theyform intermetallic compounds with Ca and segregate from the melt. Because of the presence of the finely distributed precipitate phase, the age-hardened alloys show a very high resistance to recrystallization after room-temperature working. Alloys of higher Ca content sometimes creep more readily than a lower-Cacontent alloy, mainly due to the smaller grain size [2].

Storage lime (h)

Figure 7 Change of hardnessand electricalresistivitywith storage in Pb-0.07 wt.% Ca alloy [2,76]. (Courtesy of Springer Verlag, New York.)

Properties andof Lead

Its Alloys

39

The fine-grained wrought Pb-Ca and Pb-Ca-Sn alloys possess improved material integrity and also exhibit improved corrosion performance, as they tend to undergo uniform corrosion. The corrosion resistance of these alloys is higherthan that ofantimonyalloys in many applications. The higher solidification temperatures and narrower freezing ranges of cast calcium (and calcium-tin) alloys can require higher casting and mold temperatures than antimony alloysto prevent rapid freeze-off. However, the quicker solidification time allows a faster production of large cross-section castings.

6. Pb-Cd Alloys The extent of use of binary Pb-Cd alloys is not very significant. However, large amounts of Cd are used i n low-melting Pb solders. Small additions of Cdwith Sb and Snformconstituents of cablesheathingalloysandpipe alloys. Pb-Cd alloys are of interest in storage batteries because of the lowest possible self-discharge. Lead-cadmium is an eutectic system (Figure 8) [53,77,78]. The solubility of Cd in solid lead is 3.3 wt.% at 248"C, 2.5 wt.% at 232"C, and 0.3 wt.% at room temperature. The eutectic point is at a temperature of 248°C and a Cd content of 17.5%. Discontinuous precipitation is observed in this system. The Pb-Cd alloys are age-hardenable due to high solubilities of Cd at higher temperature which decreases to a low level at room temperature.

7 . Pb-CU Alloys Copper contents of less than 0 . 1 wt.% provide considerable grain refinement and structural stability at high temperature. These alloys are of interest in cable sheathing applications. The chemical industry also prefers Cu containing lead for its mechanical properties and structural stability, and its good resistance to sulfuric acid at hightemperature.Pb-CualloyswithaCu content in the range of 37.4-87 wt.% are used in the bearing applications where the Cu phase provides the structural integrity and the Pb phase acts as a lubricant. The eutectic reaction in this system occurs on the lead side at 326°C (Figure 9) [79]. The eutecticcomposition of 0.006 wt.% Cu is very low and the structure that forms on solidification is that of a divorced eutectic. The solubility limit of Cu is <0.007 wt.% at room temperature [go]. The monotectic reaction in this system occurs at a temperature of 954°C. The critical point occurs at 995°C and a Cu content of 64 wt.% CU.

8.

Pb-Sb Alloys

The addition of 1 - 13 wt.% antimony to lead creates alloys that have very high tensile strength, resistance to fatigue, and hardness greater than pure

Chapter 2

40

150

I,,,

, , _ , , , , , , , , , , , , ,

(

IW

,

I

,

,

I

I

V “

0

IO

20

30

Cd

Figure 8 Pb-Cdphasediagram Park, Ohio.)

40

50

Pb (wt.%)

60

70

80

90

LW Pb

1771. (Courtesy of ASM International,Materials

lead (99.99%). For this reason, the antimoniallead is often called “hard lead” and the removal of antimony in lead refining is called “softening.” Pb-Sb alloys are used for pipe, cable sheathing, collapsible tubes, storage battery grids, anodes, sulfuric acid fittings, and x-ray and gamma ray shielding (in the absence of neutron irradiation). Pb-Sballoys retain a bright appearance in air for a longer time compared soft lead alloys. The Pb-Sb eutectic phase diagram is shown in Figure IO [81]. The eutectic point is at a temperature of 252°C and a composition of 1 1.1 wt.%. The solubility of Sb in lead is 3.45wt.% at the eutectic temperature and decreases to 0.3 wt.% at 50°C. Thus,considerableagehardeningcanbe obtained in thesealloys. An addition of 0.01 wt.% S lowerstheeutectic temperature by 1.9”Candincreases the eutectic composition by 0.3 wt.% [82,83]. Additions of copper, sulfur, or selenium to lead-antimony storage battery grid alloys refines the grain structure and improves castability. Coring can lead to the presence of the eutectic phase in low-Sb alloys (2 wt.%).

Properties andof Lead

Its Alloys

41

Atomlc Percent Lead

Figure 9

Pb-Cuphasediagram Park, Ohio.)

[79]. (Courtesy of ASM International,Materials

Even on air cooling, considerable soluteis retained in solution [84]. Sluggish precipitation allowseven air-cooled alloys to be agehardened.Shrinkage on solidification decreases with Sb content (Tables 3 and 4). Shrinkage on solidification of near-eutectic Pb-Sballoys is about 2.4 vol.%,which is lower than the value of 3.85 vol.% for lead [85,86]. There is a strong tendency of hypereutectic alloys to segregate as Sb floats to the top. The upper parts of the casting could therefore be richer in Sb. The rate of cooling and the viscosity influence the extent of segregation. Viscosity varies with Sb content and drops from lead side to a minimum in the composition range of 40-60 wt.% Sb [87]. The hardness increases with Sb content. In the composition range of 0.5-3 wt.%, strength and hardness values are sensitive to thermal history. As is evident from the phase diagram, a significant age hardening can be obtained in Pb-Sb alloys, and as is to be expected, the maximum amount

42

Chapter 2 AtomlcPercentAntlmony 0

LO

20

30

40

50

80

60

L

i

- .4

-.-.

0

0

Pb

10

20

30

40

50

W

70

WeightPercentAntimony

80

I

90

loo

Sb

-liquid -Liquid+ a

Figure 10 Pb-Sbphasediagram [2,81]. (Courtesy of ASM International,Materials Park, Ohio, and Springer Verlag, New York.)

Properties andof Lead

43

Its Alloys

Table 3 Variation of Solidification Shrinkage with Sb Content in Pb-Sb Alloys [46] Sb (wt.%) Solidification shrinkage (vol.%)

0 2.3 3.85

IO

12

I

2.47

16 2.06

i00

1.45

Table 4 Variation of Longitudinal Shrinkage of Pb-Sb Alloys [85,86]

19.2 19.2 14.68 06.9 3 Sb (wt.%) Casting temp. ("C) 0.65 0.64 0.56 0.56 0.54 0.54 Longitudinal shrinkage (vol.%) 0.97

"

750 650 500 450

-

of age hardening is obtained in an alloy with Sb content corresponding to the maximum solubility (Figure 1 1 ) [46,84]. Small additions of As, Cu, and Ag influence the age hardening behavior [ 2 ] .Lead of 99.994% purity does not show any significant age hardening, but with As additions of 0.05-0.1%. the rate and extent of hardening are

Figure 11 Hardness of lead-antimony alloys: ( I ) heattreated and quenched, (2) quenched from 225"C, and (3) quenched from 225°C and stored [2,46,84].(Courtesy of Springer Verlag, New York.)

Chapter 2

44

increased(Figure 12) [2,88]. An arsenic-free 2% Sb alloy hasa Brinell hardness of 10.4 comparedto 22 for a 2% Sb-O.OS% As alloy. The Cu contents of 0.005-0.05% markedly accelerate the age hardening in alloys with 1 % Sb and 0.02%-0.05% As. At As contents above 0.05%, no significant change in the extent of age hardening is observed. No age hardening is observed in an alloy with 0.85% Sb made from high purity 99.999+% lead. However, with an As addition of O.OOl%, considerable hardening is introduced (Figure 13). With an increase in As content to 0.02%, the rate of increase and the amount of increase does not change, but the base level is shifted to a higher hardness level. Apart from As, the effect is also induced by 0.01%Ag.The effect of Cu is not observed in this alloy made from high-purity alloy. In alloys with greater than 3.5% Sb, a heat-treatment temperature just below the eutectic and high cooling rates to room temperature are needed for maximum age hardening (Figure 14). An increase in aging temperature accelerates the aging process and the peak hardness achieved is higher at lower aging temperatures. The heat-treatment temperature has an influence on the role played by secondaryadditions in increasingagehardening. Quenching from a temperature of 160°C shows a less pronounced effect on age hardening than that from a temperature of 300°C. The reason for this behavior is that at 160"C, Sb is in solution but not As. Prior deformation before age hardening accelerates the age hardening process 1461.

Storage time (days)

Figure 12 Hardnessvariationwithagingtimeatroomtemperature.Lead 99.961%Pb-0.022%Bi-0.014% Cu; LeadB:99.994%Pb;Lead 12,881. (Courtesy of Springer Verlag, New York.)

A:

C: 99.99%Pb

Properties of Lead andIts Alloys

45

Sb (wt.%) Figure 14 Tensile strength change in Pb-Sb alloys at differentquenchingtemperatures. Storage time 1 day 12,461. (Courtesy of Springer Verlag, New York.)

Chapter 2

46

Lead-antimony alloys have high corrosion resistance in most environments. They form a protective, impermeable film even faster than pure lead and, in some cases, even faster than chemical lead. At some of the current densities usedin metal plating processes, 6% antimonial lead anodes have excellent corrosion resistance. Most of the antimonial lead produced is used for storage battery components and contains 2.5-8% antimony. The alloys with compositions of from 1% to 13% antimony are used to provide corrosion resistance, with antimony levels of 0.80- 1.15% and 6-8% used most frequently in nonbattery applications. The 0.80-1.15%alloys are used to make cable sheathing and the 6-8% antimony alloys are used to fabricate linings, pipe,andonetype of awide variety of equipmentsuchastank anodeused in chromium plating. Leadalloyswithhigherpercentages of antimony, such as 13%, are used to make castings when hardness is of key importance. Lead alloys with more than 13% antimony are rarely used because they are very brittle and do not have high corrosion resistance.

9.

Pb-Sn Alloys

The Pb-Sn alloys share with Pb-Sb alloys the status as the most important alloy groups of lead. Pb-Sn alloys containing up to 3% Sn are used in cable sheathing. Higher-Sn-content alloys are used principally as solders and, to some extent, for pressure die casting of Pb-Sn parts. Organ pipes use 45% Sn and 75% Sn alloys. Sn is also used along with other alloying elements principally Sb in bearing and type metals. 15) has an eutectic at a ThePb-Snbinaryphasediagram(Figure temperature of 183°C and a composition of 61.9 wt.% Sn [2,89]. The solid solubility of Sn i n Pb at 183°C is about 19 wt.%, which decreases to 1.3 2 0.5 wt.% at room temperature. Similar to Pb-Sb alloys, significant age hardeningcan be obtained in these alloys. On coolingfrom the single-phase region to room temperature, streaky and granularSn precipitates are obtained in a matrix of Pb in alloys containing from 1.3 to 19.2 wt.% Sn [2]. Coring can lead to the presence of the eutectic phase in low-Sn-content alloys. PbSn alloys do not assume the gray appearance of pure lead, even on storage. In the case of eutectic alloy, the eutectic lamellae thickness is proportional to V".5,where V is the solidification rate (interface velocity) [go]. The strength and hardness increase with decreasing lamellar thickness. The Brinell hardness increases rapidly from a value of about 4 in pure lead to around 12 at the solid solubility limit and then increases less rapidly to a maximum in the range 14-18 at the eutectic composition [91]. Tinalloyswith lead overamuchwiderrangeofcompositionthan antimony. Tin alloys of lead have much lower densities and melting points than pure lead [92]. Both density and liquidus temperature decrease as more

Properties andof Lead

330

o

Its Alloys

47 Sn (at.%)

10

20

30

eo

50

40

70

eo

80

0

0

Pb

10

20

30

40

50

Sn (wt.%)

00

70

00

100

so

100

Sn

Figure 15 Pb-Sn phase diagram [ 8 9 ] . (Courtesy of ASM International, Materials Park, Ohio.)

tin is added, until the eutecticcomposition(approximately 63% Sn, 37% Pb) is reached. Their lower melting point and increased strength have made the high tin alloys especially important as solders. However, the alloys used primarily forcorrosion resistance are low in tin, with the most important alloy. terne, usually having a composition of 12-20% Sn. Terne is used to coat steel to make what is called terneplate or terne metal. The tin “wets” the steel, allowing the fonnation of a metallurgical bond between lead and steel. Other lead-tin alloys are used as coatings on copper building flashings and on both copper and steel electronic components. Anodes made of a 7% tin alloy are used in chromium-plating operations. The combined effect of adding both tin and antimony to lead is to create ternary alloys, some of which have very low coefficients of friction. These strong, low-friction alloys have found use in special situations such as steam spargers in chemical

Chapter 2

48

reactors. Antimony is also added to lead-tin alloy coatings, where a harder or, in a few cases, a more corrosion-resistant coating is required.

10.

Pb-Te Alloys

The Pb-Te alloys have a very high fatigue strength and are usedin cable sheathing and radiation shielding applications. These alloys also have good resistance to sulfuric acid. The optimal addition in pure binary alloys is about 0.01% and with Cu addition, optimal Te content is 0.04-0.05%. Additions of Cu of about 0.04% to Pb-Te alloys with 0.04-0.05% Te stabilize the grain size. The refined grain size and work hardening in these alloys results in increased resistance to distortion and fatigue failure. Besides cable sheathing, this alloy is useful in making steam-heating coils. Similar to Pb-Cu alloys, the Pb-Te binary system has an eutectic very [93]. The eutectic occurs at avery lowTe close to purelead(Figure16) level of 0.025 wt.% Teand a temperature of 326.7"C. The eutectic phase AtomicPercentTellurlum 1000

0

10

Pb

20

30

40

50 I

BO

Tellurium Weight Percent

70

80

90

LOO

Te

Figure 16 Pb-Tephase diagram 1931. (Courtesy of ASM International,Materials Park, Ohio.)

Properties andof Lead

Its Alloys

49

consists of a nearly pure lead-phase matrix and cuboidal precipitates of PbTe. The maximum solubility of Te in solid lead is around 0.004-0.005%. Supersaturation to levels of 0.2 wt.% has been obtained by rapid cooling. Pb0.06 wt.% Te alloys, cold worked and recrystallized at 2SO"C, are very fine grained (941. Significant age hardening can be obtained from supersaturated solid solutions containing 0.1 wt.% Te [94,95].

11. Pb-Zn Alloys The Pb-Zn alloys exhibit a miscibility gap i n liquid state at a temperature above 417.8"C (Figure 17) 1961. Themaximumtemperature to which this persists is 798°C. This miscibility gap is utilized in the desilverization of lead by zinc. The solubility of Zn in solid lead at 318°C is 0.05-0.06%. A solubility limit at the eutectic temperature has been suggested up to -0.1 wt.% Zn. The principal interest in Pb-Zn system is in the desilverization of

800

Y

700

W

L

3 e)

0

L1 +

600

L

L2

W R

E

+W

500

417.8.C 98

31e.z-c

327.502T 98.1

300

(Pbb 200

0

Zn

IO

20

30

"r-"""~

40

50

60

Welght P e r c e n t Lead

70

80

90

0

Pb

Figure 17 Pb-Zn phasediagram [96]. (Courtesy of ASM International,Materials Park, Ohio.)

Chapter 2

50

Pb. These alloys have also been considered in the past for cable sheathing applications. Pb-Zn alloys with 0.5- 1 % Zn have a lower extrusion pressure during cable sheathing compared to Pb-0.6% Sb alloys and have a similar fatigue strength. The addition of 0.8% Zn increased the Brinell hardness (H!,) from 43 to 53 MPa and the tensile strength of extruded pipe increased from 15 to 18 MPa 1971. Thecreep strength with zinc is also better than that of pure lead.

12.

Pb-Li Alloys

The addition of 0.01 wt.% Li increased the tensile strength by 20MPa. Alloys with up to 2.15 wt.% Li are stable in air, even on long standing [98]. Alloyswith Li and Sn can be strengthenedto 15 ksi by quenchingfrom melt [99]. The ability to thermalize neutrons in shielding applications makes the Pb-Li alloy attractive in somenuclearshielding applications. Binary alloys are not common, but ternary alloys find use in cable sheathing and bearing applications. The phase diagram for the Pb-Li system is shown in Figure 18 [ 1001. Solubility of Li in lead is 0.1 I wt.%at 235°Cand 0.03 wt.%at 120°C. Lower solubility values of 0.09, 0.07, 0.06, 0.04, and 0.01 at 235"C, 200°C 170"C, 120"C, and 20"C, respectively, have also been reported by Pogodin andShpichinetsky 101I. The Pb-0.01 wt% Li alloy shows significant age hardening [ 1021.

13. Pb-In alloys Lead containing more than 0.5 wt.% In wets glass, and lead-indium alloys with up to 5% In can be used for soldering glass over a n;u-row temperature range [ 1031. Sn-In alloys are better but require more than 40% In. Additions of In of over 25% to lead-tin solders increase their alkali resistance [ 1041. In in Pb-Ag solders increases their strength. Various Addition of1-2% low-melting-point alloys have In additions to lower the melting point further. Indium can be made to diffuse to the lead surface and increase its corrosion resistance to certain lubricants in bearings. Figure 19 [104a]presents the binary phase diagram of Pb-In system. The system exhibits extensive solid solubility of Pb in In and In in Pb. Solubility of In in lead at room temperature is about 52 wt.%.

14. Ternary Alloys Among the ternary alloys,Pb-Sn-Ca,Pb-Sb-Sn,Pb-Sn-Ag,andPbSb-Ag systems are of greatest interest. Theirphasediagrams are shown

51

Propertiesof Lead and ItsAlloys

A t o m ~ cPercent Lead 5

0

0 L1

IO

20

30

40

50

60

Weight Percent Lead

IO

70

30 50 100

20

80

90

100

Pb

Figure 18 Pb-Li phase diagram [2,100]. (Courtesy of ASM International, Materials Park, Ohio, and Springer Verlag, New York.)

52

Chapter 2 A t o r n l c Percent Lead 20

10

350 0

30

50

40

60

70

80

90

100 f

!

1

i 1

1 50

1

0

Welght

In

10

20

30

40

50

60

70

P e r c e n t Lead

80

90

i "L 100 Pb

Figure 19 Pb-In phase diagram [ 104a1 (Courtesy of ASM International. Materials Park, Ohio.)

Figures 20-23 [2,105- 1 121. Figure 24 shows the lattice parameter variation with Sn content in the Ca(Pb,Sn), phase.

B. Composition, Electrical, Mass, and Thermal Properties of Lead and LeadAlloys In this section, various physical properties of lead alloys are presented ac(UNS) number. The assigned cordingto their UnitiedNumberingSystem number ranges for lead and its alloys are shown in Table S [28]. The UNS number, description of the alloy, its nominal compositions, and equivalent specifications in ASTM, DIN, BS, FED, and SAE specifications are listed for each alloy i n Table 6 [28]. A listing of basic ANSI/ASTMB29-92 specifications covering chemical compositions of refined lead i n pig, block, or hog and that of ASTM 749-85 (Reapproved 1991) chemical requirements for lead-alloy strip, sheet, and plate products are presented in Tables 7 and

Properties of Lead and Its Alloys

53

Figure 20 Pb-Sb-Ag phase diagram: projection of eutectic valleys and isotherms of liquidus surfaces [2,105]. (Courtesy of Springer Verlag, New York).

54

Chapter 2

Sn

f0D

Q

Fb

Giver

Figure 21 Pb-Sn-Ag phase diagram; projection of eutectic valleys and isotherms of liquidus surfaces [2,106,107]. (Courtesy of Springer Verlag, New York.)

55

Properties of Lead and Its Alloys

Pb

Tin

Sn

Figure 22 Pb-Sb-Sn phase diagram; projection of eutectic valleys and isotherms of liquidus surfaces [2,108,109]. (Reprinted with permission from Springcr Verlag, New York.)

56

Chapter 2

Sn (wt.%)

Mole fraction Sn

sn (M%)

Pb

20

40

Figure 23 Suggestcd Pb-Ca-Sn

60

80

100

phasediagrams.(a)

At room temperature,Ref.

1 IO, (b) At room temperature, Ref. 1 1 I , (c) Isothermalsection at 127°Cnear Pb corner. Ref. 1 12, (d) Isothermal section at 127°C for X,,, < 0.25, Rcf. I 12, and (c)

Projectionof eutectic valleys,Ref. 112. (Reprinted with pennissionfrom Prengaman (a) and Elsevier Science, Oxford, UK (b-e).)

R. D.

57

Propertiesof Lead and itsAlloys 0.492 0.49 0.400

{

0.406

.$

0.404

5

m

2

U ._

g

0.402 0.40 0.470

2

0.476 0.474 0.472 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Mole fraction Sn

Figure 24 Latticeparametervariation of Ca(Pb,Sn),-L12 phase with Sncontent [ 1 121. (Reprinted with permission from Elsevier Science, Oxford, UK.)

8 [ I 13,1141. Chemical requirements of alloys are also listed according to their application in Tables 9- 17 [28]. The electrical, electrical resistivity, mass, and thermal properties are listed in Tables 18, 19, 20, and 21, respectively [28,1151.

II. MECHANICAL PROPERTIES OF LEAD AND LEAD ALLOYS

A.

Deformation Mechanisms Operative in Lead and Lead Alloys

The mechanisms by which plastic flow of ametal or materialoccurs involve processes occurring on the atomic scale that include the glide motion of dislocation lines, the coupled glide and climb of dislocations, the diffusive flow of individual atoms, the relativedisplacement of grains by grainboundary sliding, and mechanical twinning that involves the motion of twinning dislocations. At all temperature above 0 K, thermally activated movement of atoms and dislocations is present. The extent of thermal activation increases with the homologous temperature (T/T&,),where T is the temperature of interest and T, is the melting point. The low melting point of lead and lead alloys makes the contribution of thermal activation to plastic flow very significant, even at room temperature, which corresponds to a homologous temperature of around 0.5 K. The evaluation of mechanical property data on lead and lead alloys requires an appreciation of the different mech-

Chapter 2

58

Table 5 AssignedNumberRanges for Lead and Its Alloys [28]. (Courtesy of Lead Industries Association, New York.)

Designated No. Lead-alloy system Designated No. Lead-alloy system LS0000-L50099 Pure leads L50100-L50199 Pb-Ag LS020O-LS0299 Pb-AI LS0300-LS0399 Pb-As L50400-L50499 Pb-Au LS050O-L5OS99 Pb-Ba L50600-LS0699 Pb-Bi L50700-L50799 Pb-Ca LS0800-LS0899 Pb-Ca LS0900-LS0999 Pb-Cd L5 1000-L5 1099 Pb-CO L5 I IOO-LS 1 199 Pb-Cu L5 1200-L5 I299 Pb-Fe L5 1300-LS 1399 Pb-Ga L5 1400-L5 1499 Pb-Hg L5 1 500-L5 I599 Pb-In L5 1600-L51699 Pb-K L5 1700-L5 1799 Pb-Li L5 1800-L5 1899 Pb-Mg L51900-L5 1999 Pb-M11 LS2000-LS2099 Pb-Na LS2100-LS2199 Pb-Ni L52200-LS2299 Pb-0 LS2300-L52399 Pb-P L52400-LS2499 Pb-S LS2500-LS2599 Pb-(
L53000-L53099 Pb-(S.0-5.99)Sb L53 100-LS3199 Pb-(6.0-6.99)Sb L53200-L53299 Pb-(7.0-8.99)Sb LS3300-LS3399 Pb-(9.0-10.99)Sb LS3400-L53499 Pb-( I 1 .O- 12.99)Sb L53500-LS3599 Pb-( 13.0- 15.99)Sb LS3600-LS3699 Pb-( 16.0-19.99)Sb L53700-LS3799 Pb-(>20%)Sb LS3X00-LS3899 Pb-Se LS3900-LS3999 Pb-Si L54000-LS4099 Pb-(58%)Sn L55200-LSS299 Pb-Sr LSS300-LSS399 Pb-Te L55400-LSS499 Pb-TI LS5500-LS5599 Pb-Zn LSS600-L55699 Pb-Zr LSS700-LSS799 Miscellaneous alloys not included above.

anisms of plastic flow that are operative at room temperature and at elevated temperatures, to which lead alloys will be subjected. In a perfect crystal, the plastic deformation can occur by a slip process in which simultaneous translation of one plane of atoms over another occurs. No dislocations are involved in this case. This occurs at a stress level that is refened to as the ideal strength above which the deformation is no longer elastic and becomes catastrophic. The ideal shear strength is about 0.06 F

Table 6 York.) Unified No.

Listing of Lead Alloys as per the Unified Numbering System [ 2 8 ] . (Courtesy of Lead Industries Association, New

3

U

2 g

Description

Chemical composition"

Cross-referenced specifications

u)

s

r

L50001 L50005 L50010

Zone Refined Lead Refined Soft Lead Refined Soft Lead

Pb 99.9999 min Pb 99.999 min Pb 99.99 min

L500 11 L500 12 L500 13

Refined Soft Lead Refined Soft Lead Refined Soft Lead

Pb 99.99 min Pb 99.99 min Pb 99.99 min

L50014 L50020 L50025 L50035 L50040 L5004 1 L.50042

Refined Soft Lead Refined Soft Lead LME Grade Pure Lead Refined Soft Lead Refined Soft Lead Refined Soft Lead Corroding Lead

L50045

Common Lead

L50050

Grade A Lead

Pb 99.99 min Pb 99.985 Pb 99.97 Pb 99.95 min Pb 99.94 min Pb 99.94 min Ag 0.0015 max Bi 0.050 max Cu 0.0015 max Fe 0.002 max Pb 99.94 min Zn 0.001 max (Cu + Ag) 0.0025 max. (As + Sb + Sn) 0.002 max Ag 0.005 max Bi 0.050 max Cu 0.0015 max Fe 0.002 max Pb 99.94 rnin Zn 0.001 max. (As + Sb + Sn) 0.002 max Pb 99.90 min Total other elements 0.10 max

b Ql n

Canadian CSA HP21958 Type 1 Australia AS-8 1975 Soft Pb India 99.99 IS-27-1965 UK BS 334 Chemical A Germany Pure Pb DIN 17 19 Germany Pure Pb DIN 17 19 LME Australia AS-1812-1975 Soft India 99.94 IS-27-1975 Germany Smelter Lead DIN 1719 ASTM B29 (Corroding Lead); FED QQL- 17 1

ASTM B29 (Common Lead)

FED QQL- 17 1 Grade A

5

-n B e-

0 U u)

Table 6

Continued

Unified No.

Description

L50060 L50065

Type 111 Lead Grade AA Lead, Grade C Lead

Pb 99.85 min Pb 99.7 min Sb 0.02 max

L50070 L50080 L50090 L50101 L50110 L50113 L50115 L50 120 L50121 L50 122 L50131

Grade B Remelted Lead Grade B Lead Chemical B Grade Lead Cable Sheathing Alloy Electrowinning Anode Alloy Solder Alloy Electrowinning Anode Alloy Electrowinning Anode Alloy Solder Alloy Electrowinning Anode Alloy Solder Alloy-Grade 1.5s

L50132

Solder Alloy-Grade

L50 134 L50 140

Solder Alloy-Grade 5s Cathodic Protection Anode Alloy

Bi 0.025 max (optional) Pb 99.5 min Pb 950 min. Total other elements 5.0 max Pb N.S. Ag 0.2 nom Pb 99.8 nom Ag 0.5 nom Pb 99.5 nom Ag 0.5 nom Pb 97.0 nom Sn 2.5 nom Ag 0.75 nom Pb 99.25 nom Ag 1.0 nom Pb 99.0 nom Ag 1.0 nom Pb 98 nom Sn 1.0 nom Ag I .O nom As 1 .O nom Pb 98 nom Ag 1.3- 1.7 A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 97.5 nom Sn 0.75-1.25 Zn 0.005 max Ag 1.3-1.7 A1 0.005 max As 0.02 max Bi 0.25 max Cd 0.001 max Cu 0.30 max Fe 0.02 max Pb rem Sb 0.40 max. Total of all others 0.08 max Ag 1.5 nom Pb 93.5 nom Sn 5.0 nom Ag 2.0 nom Pb 98.0 nom

Chemical composition"

Ag 1.5

Cross-referenced specifications Canada CSA-HP2-1958 Type 1 I I FED QQ-C-40 (Grade AA and Grade C) FED QQ-L-201 Grade B Remelt FED QQ-L- 17 1 Grade B UK BS 334 Chemical B

AMS 4756; ASTM 0 3 2 (1.55); BS 219; Grade IS DIN 1707 FED QQ-S-57 1 (AgI-5)

BS19; Grade 5 s

L50150

Solder Alloy-Grade

Ag2.5

L5015 1

Solder Alloy-Grade

Ag2.5

L50 152 L50170 L5017 1 L50172 L50180

Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy-Grade

Ag 5.5

L503 10

Arsenical Lead Cable Sheathing Alloy Lead-Barium Alloy Lead-Tin Barium Alloy Lead-Tin Barium Alloy Lead-Tin Barium Alloy Lead-Tin Barium Alloy Lead-Tin Barium Alloy

L505 10 L50520 L5052 1 L50522 L50530 L50535

Ag 2.3-2.7 Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 97.5 nom Sn 0.25 max Zn 0.005 max Ag 2.3-2.7 Al 0.005 max As 0.02 max Bi 0.25 max Cd 0.001 max Cu 0.30 max Fe 0.02 max Pb rem Sb 0.40 max Sn 0.25 max Zn 0.005 max. Total of all others 0.03 max Ag 2.5 nom Pb 95.5 nom Sn 2.0 nom Ag 5.0 nom Pb 95.0 nom Ag 5.0 nom Sn 5.0 Pb rem Ag 5.0 nom In 5.0 nom Pb 90.0 nom Ag 5.0-6.0 Al 0.005 max As 0.02 max Bi 0.25 max Cd 0.001 max Cu 0.30 max Fe 0.002 max Pb rem Sb 0.40 max Sn 0.25 max Zn 0.005 max. Other total of all others 0.03 max As 0.15 nom Bi 0.10 nom Pb 99.6 nom Sn 0.10 nom Pb 99.9 nom. Ba 0.05 nom Pb 99.0 nom Sn 1.0 nom. Ba 0.05 nom Pb 98.5 nom Sn 1.5 nom. Ba 0.05 nom Pb 98.0 nom Sn 2.0 nom. Ba 0.05 nom Pb 98.9 nom Sn 1.O nom. Ba 0.10 nom Pb 97.9 nom Sn 2.0 nom. Ba 0.10 nom

ASTM B32 (2.5s); DIN 1707: L-Pb Ag3

s

0 -0

?!

$.

FED QQ-S-571 (Ag 2.5)

( F 3 Cable Sheath)

u)

s

Table 6 Unified No.

Continued Description

L50540 L5054 I L50542 L50543 L50605 L506 10

Frary Metal Frary Metal Frary Metal Frary Metal Fusible Alloy Fusible Alloy

L50620 L50630 L50640 L50645 L50650 L50660 L50665 L50680 L507 10 L507 12 L507 13 L50720

Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Lead-Calcium Alloy Cable Sheathing Alloy Cable Sheathing Alloy Lead Calcium Alloy

Chemical composition'' Pb 98.8 nom. Ba 0.4 nom. Ca 0.8 nom Pb 98.5 nom. Ba 1.0 nom. Ca 0.5 nom Pb 98.0 nom. Ba 1.2 nom. Ca 0.8 nom Pb 97.2 nom. Ba 2.0 nom. Ca 0.8 nom Bi 42 Cd 9 Sn 11 Pb rem Bi 42.9 Cd 5.1 Sn 7.9 Hg 4 In 18.3 Pb rem Bi 44.7 Cd 5.3 Sn 8.3 In 19.1 Pb rem Bi 48 Sn 14.5 Sb 9 Pb rem Bi 49 Sn 12 In 21 Pb rem Bi 50 Cd 6.2 Sn 9.3 Pb rem Bi 50 Cd 10 Sn 13.3 Pb rem Bi 5 1.7 Cd 8.1 Pb rem Bi 52.5 Sn 15.5 Pb rem Bi 55.5 Pb rem Pb 99.9 nom. Ca 0.008 nom Pb 99.9 nom. Ca 0.025 nm Pb 99.7 nom Sn 0.3 nom. Ca 0.025 nom Pb 99.9 nom. Ca 0.03 nom

Cross-referenced specifications

tu

L50722 L50725 L50728 L50730 L50735 L50736 L50737 L50740 L50745 L50750 L50755 L50760 L50765 L50770 L50775

Lead-Copper Calcium Alloy Cable Sheathing Alloy Battery Grid Alloy. LeadCalcium-Tin Electrowinning Anode Alloy Battery Grid Alloy. LeadCalcium Battery Grid Alloy. LeadCalicum-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium Battery Grid Alloy. LeadCalcium-Tin

Cu 0.06 nom Pb 99.9 nom. Ca 0.03 nom Cu 0.06 nom Pb 99.9 nom. Ca 0.035 nom Pb 99.5 nom Sn 0.5 nom. Ca 0.04 nom Ag 0.5 nom Pb 99.4 nom. Ca 0.05 nom Pb 99.9 nom. Ca 0.06 nom Pb 99.7 nom S n 0.2 nom. Ca 0.065 nom Pb 99.4 nom S n 0.5 nom. Ca 0.065 nom Pb 99.2 nom Sn 0.7 nom. Ca 0.065 nom Pb 98.9 nom Sn 1.0 nom. Ca 0.065 nom Pb 98.6 nom Sn 1.3 noni. Ca 0.065 nom Pb 98.4 nom Sn 1.5 nom. Ca 0.065 nom Pb 99.9 nom. Ca 0.07 nom Pb 99.2 nom Sn 0.7 nom. Ca 0.07 nom Pb 99.9 nom. Ca 0.10 nom Pb 99.6 norn Sn 0.3 nom. Ca 0.10 nom

Table 6 Continued Unified No.

Description

L508 10

Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Battery Grid Alloy. LeadCalcium-Tin Bahnmetal, Bearing Metal

L50820

Bahnmetal, Bearing Metal

L50840 L50850 L50880 L50940

Lead-Calcium Alloy Lead-Calcium Master Alloy Lead-Calcium Alloy Lead-Cadmium AlloyEutectic Copperized Lead Chemical Lead

L50780 L50790 L50795 L50800

L51110 L51120

Chemical composition" Pb 99.4 nom Sn 0.5 nom. Ca 0.10 nom Pb 98.9 nom Sn 1.O nom. Ca 0.10 nom Pb 99.6 nom Sn 0.3 nom. Ca 0.12 nom

Pb 99.6 nom Sn 0.3 nom. Ca 0.12 nom Al 0.02 nom Li 0.04 norn Pb 98.7 nom.

Ca 0.7 nom, Na 0.6 nonl Al 0.2 nom Li 0.04 nom Pb 98.7 nom. Ca 0.7 nom, Na 0.2 nom, Ba 0.4 nom Pb 99.0 nom. Ca 1.0 nom Pb 98 nom. Ca 2.0 norn Pb 94.0 nom. Ca 6.0 nom Cd 17.0 nom Pb 83.0 nom Cu 0.05 nom Pb 99.9 nom Ag 0.002-0.02 Bi 0.005 max Cu 0.040.08 Fe 0.002 max Pb 99.90 min Zn 0.001 max. (As + Sb + Sn) 0.002 max

Cross-referenced specifications

L5 1 12 1

L5 1 123

L5 1124

L5 1 125

Copper Bearing Lead

Grade D per QQ-L-20 1

Grade D per QQ-C-40

Pure Copper Lead, Copperized Soft Lead

L5 1 180

Copper-Lead Bearing Alloy

LS1510

Lead-Indium-Silver Solder Alloy Lead-Indium Solder Alloy Lead-Indium-Silver Solder Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy

LS1511 LS1512 L5 1530 L51532 L5 1535 L5 1540 L5 154s L5 1550

Ag 0.020 max Bi 0.005 max Cu 0.040.08 Fe 0.002 max Pb 99.90 rnin Zn 0.001 max. (As + Sb + Sn) 0.002 max Ag 0.02 max Bi 0.025 max Cu 0.04-0.08 Fe 0.002 rnax Pb 99.85 min Te 0.0350.060 Zn 0.001 max. (As + Sh + Sn) 0.002 max Ag 0.02 max Bi 0.025 max Cu 0.04-0.08 Fe 0.002 max Pb 99.82 rnin Sn 0.016 max Te 0.035-0.055 max Zn 0.001 (Sb + As) 0.002 max Cu 0.06 Pb 99.9 rnin

Cu rem Fe 0.35 max Pb 44.0-58.0 Sn 1.O-5.0. Others: Total 0.45 max, each 0.15 max Ag 2.38 nom In 4.76 nom Pb 92.8 nom

In 5.0 nom Pb 95.0 nom Ag 2.5 nom In 5.0 nom Pb 92.5 nom In In In In In In

19.0 nom 20.0 nom 25.0 nom 40.0 nom 40.0 nom 50.0 nom

Pb Pb Pb Pb Sn Pb

8 I .O nom 80.0 nom 75.0 nom 60.0 nom 40 Pb rern 50.0 norn

ASTM B29 (Copper Bearing Lead); FED QQ-L-171 (Grade C); QQ-L-201 (Grade C) FED QQ-L-201 (Grade D)

T

0

'0

4 s. (D v)

0, r 0 0)

Q

FED QQ-C-40 (Grade D)

P)

3

n

zf Australia AS 1812 Copperized soft: DIN 17 19 Pure Copper Pb; Canada CSAHP2 Type 1 1 SAE 5460. No. 485

e-

0 Y v)

Q, Q,

Table 6 Continued ~~

Unified No. L5 IS60 L5 1570 L5 158.5 L.5 170.5 L5 I708 L.51710 L51720 L.51730 L5 1740 L.5 1748 L5 1770 L.5 177.5 L.5 1778 L.5 1780 L5 1790 L52.505 L52.510 LS25 15 L52.520 L.52.525

~

~

Chemical composition"

Description Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Lithium Alloy Lead-Lithium Alloy Lead-Lithium Alloy Lead-Lithium Alloy Lead-Lithium Alloy Lead-Tin-Lithium Alloy Lead-Tin-Lithium Alloy Lead-Tin-Li thiurn-Calcium Alloy Lead-Tin-Lithium-Calcium Alloy Lead-Tin-Lithium-Calcium Alloy Lead-Tin-Lithium-Calcium Alloy Lead-Tin-Li thiurn-Calcium Alloy Lead-Antimony Alloy 99.8 Pb Cable Sheathing Alloy Cable Sheathing Alloy Cable Sheathing Alloy

Cross-referenced specifications

In In In Li Li Li Li Li Li Li Li

60 nom Pb 40 70 nom Pb 30 80 Ag 5 Pb 15 0.01 nom Pb 99.9 nom 0.02 nom Pb 99.9 nom 0.03 nom Pb 99.9 nom 0.06 nom Pb 99.9 nom 0.07 norn Pb 99.9 nom 0.02 nom Pb 99.9 nom Sn 0.3.5 nom 0.04 nom Pb 99.2 nom Sn 0.7 nom 0.08 nom Pb 98.8 nom Sn 1.0 nom. Ca 0.03 nom Li 0.12 nom Pb 98.8 nom Sn 1.0 nom. Ca 0.03 nom Li 0.15 norn Pb 97.8 nom Sn 2.0 norn. Ca 0.04 nom Li 0.15 nom Pb 99.6 norn Sn 0.1 nom. Ca 0.15 nom Li 0.6.5 nom Pb 98.3 nom Sn 1.0 nom. Ca 0.02 nom Pb 99.9 nom Sb 0.1 nom Cu 0.06 Pb 99.8 nom Sb 0.1 Sn 0.1 As 0.015 nom Pb 99.8 norn Sb 0.2 nom Pb 99.4 Sb 0.2 Sn 0.4 As 0.035 nom Pb 99.7 nom Sb 0.3 nom Te 0.035 nom

BS 801 99.8 Pb

BS 801 Alloy E

L52530 L52535 L52540 L52545 L52550

Lead-Antimony Alloy Cable Sheathing Alloy Cable Sheathing Alloy Lead-Antimony Alloy Cable Sheathing Alloy

L.52555 L52560 L52565 L.52570 L.52595 L52605 L526 15

Alloy B per DIN 17640 Bullet Alloy Overhead Cable Alloy Cable Sheathing Alloy Cable Sheathing Alloy 1 % Antimonial Lead Lead-base Die Casting Alloy

L526 18 L52620 L52625

Lead- Antimony-Gallium Alloy Battery Alloy Shot Alloy

L52630

Battery Alloy

L52705 L52710

2% Antimonial Lead Battery Alloy

L527 15

Battery Alloy

L52720

Battery Alloy

L52725 L52730

Bullet Alloy Electrotype-General

Pb 99.6 nom Sb 0.35 nom As 0.03 nom Pb 99.6 nom Sb 0.4 nom Cd 0.25 nom Pb 99.2 nom Sb 0.5 nom Pb 99.4 nom Sb 0.6 nom Cu 0.04 nom Pb 99.3 nom Sb 0.6 nom Te 0.04 nom Pb 99.3 Sb 0.7 Pb 99.2 nom Sb 0.75 nom Pb 99.2 nom Sb 0.75 nom Cu 0.06 rnax Pb 99.1 Sb 0.85 Pb 99.0 nom Sb 0.95 nom Pb 99.0 nom Sb 1.0 nom As 0.1 nom Pb 98.6 nom S 0.003 nom Sb 1.0 nom Sn 0.3 nom Pb 98.0 nom Sb 1.2 nom. Ga 0.8 nom Cd 1.45 nom Pb 97.0 nom Sb 1.5 nom As 0.45 nom Pb 98.0 nom Sb 1.55 nom Sn 0.0005 max As 0.3 Pb 98 nom S 0.005 Sb 1.6 Se 0.02 Sn 0.1 Pb 98.0 nom Sb 2.0 nom As 0.15 Pb 97.5 nom S 0.003 Sb 2.0 Sn 0.3 As 0.25 Pb 97.4 nom Sb 2.25 Se 0.02 Sn 0.1 As 0.3 Pb 97.2 nom S 0.008 Sb 2.25 Se 0.02 Sn 0.2 Pb 97.5 norn Sb 2.5 nom Pb 95 nom Sb 2.5 nom Sn 2.5 nom

BS 801 Alloy D

DIN 17640 Alloy B

BS 801 Alloy B

Table 6

Q,

Continued

03

~

~~

Unified No.

~~

~

Description

L52750

Battery Alloy

L52755

Battery Alloy

L52760

Battery Alloy

L52770

Battery Alloy

L52775

Battery Alloy

L52805 L528 10

3% Antimonial Lead Battery Alloy

L528 15

Shot Alloy

L52830 L52840

Electrotype-General Battery Alloy

L52860

Lead-base Bearing Alloy No. 16 (Overlay)

L52901 L52905 L529 10

4% Antimonial Lead Battery Alloy Lead-Antimony-Tin Alloy

Chemical composition' As 0.4 Pb 96.5 nom S 0.005 Sb 2.75 Sn 0.3. Ca 0.075 As 0.5 Pb 96.4 nom S 0.007 Sb 2.75 Sn 0.3. Ca 0.075 AS 0. I8 Cu 0.075 Pb 96.8 nom S 0.008 Sb 2.75 Sn 0.2 As 0.15 Cu 0.04 max Pb 96.6 nom S 0.004 Sb 2.9 Sn 0.3 As 0.15 Cu 0.05 max Pb 96.6 nom S 0.004 Sb 2.9 Sn 0.3 Pb 97 nom Sb 3.0 nom As 0.15 Pb 96.5 nom S 0.003 Sb 3.0 Sn 0.3 As 0.6 Pb 96.4 nom Sb 3.0 Sn 0.0005 max Pb 94 nom Sb 3 nom Sn 3 norn As 0.5 Cu 0.12 Pb 95.7 nom Sb 3.25 Sn 0.4. Ca 0.06 A1 0.005 max As 0.05 max Bi 0.10 max Cd 0.005 max Cu 0.10 max Pb rem Sb 3.0-4.0 Sn 3.5-4.7 Zn 0.005 max. Other total of others 0.40 max Pb 96 nom Sb 4 nom As 0.15 Pb 95.5 S 0.003 Sb 4.0 Sn 0.3 Pb 95 nom Sb 4 nom Sn 1 nom

Cross-referenced specifications

L529 15 L52920 L52922 L52930

Type Metal Alloy 4.5% Antimonial Lead Anode Alloy Battery Alloy

L52940

Battery Alloy

L53020 L53 105 L53110 L53115 L53 120 L53 122 L53 125

L53 I30

Bullet Alloy 6% Antimonial Lead Lead Alloy Rolled Sheet Alloy Electrowinning Anode Alloy High Strength Sheet Lead Creep Resistant Pipe and Sheet Alloy Lead Alloy

L53131 L53 135

Lead Alloy Battery Alloy

L53 140

Hard Shot Alloy

L53210 L53220 L53230 L53235

Type Metal Alloy Lead Alloy 8% Antimonial Lead Hard Shot Alloy

L53238

Hard Shot Alloy

Pb 93 nom Sb 4 nom Sn 3 nom Pb 95.5 nom Sb 4.5 nom Pb 95 nom S 0.5 nom Sb 4.5 nom As 03 Cu 0.05 Pb 94.6 nom S 0.007 Sb 4.75 Sn 0.3 As 0.15 Cu 0.05 Pb 94.8 nom S 0.004 Sb 4.75 Sn 0.3 Pb 90.0 nom Sb 5.0 nom Sn 5.0 nom Pb 94 nom Sb 6.0 nom Pb 94 nom Sb 6 nom Pb 93.7 nom Sb 6.0 nom Sn 0.3 nom As 0.4 nom Pb 93.6 nom Sb 6.0 nom As 0.4 nom Pb 93.6 nom Sb 6.0 nom As 0.65 nom Pb 93.3 nom Sb 6.0 nom

As 0.6 nom Pb 92.8 nom Sb 6.0 nom Sn 0.6 nom Pb rem Sb 6.0-7.0 Sn 0.25-0.75 As 0.3 Cu 0.07 Pb 93.4 norn S 0.006 Sb 6.0 Sn 0.3 As 1.2 nom Pb 92.6 nom Sb 6.2 nom Sn 0.0005 max Pb 89 nom Sb 7 nom Sn 4 nom As 0.6 Pb 91.8 nom Sb 7.0 Sn 0.6 Pb 92 nom Sb 8 nom As 1.25 nom Pb 90.7 nom Sb 8.0 nom Sn 0.0005 max As 2 nom Pb 90.0 nom Sb 8 nom Sn 0.0005 max

DIN 16512

r sl n

(P

AMS 7720:772 1

-l 0

Table 6 Continued Unified No.

Description

L53260 L53265 L53305 L533 10 L53320 L53340

Spin Casting Alloy Type Metal Alloy 9% Antimonial Lead Lead Alloy White Metal Bearing Alloy Lead-base Die Casting Alloy

L53343

Lead-base Bearing Alloy

L53345

Lead-base Bearing Alloy

L53346

Lead-base Bearing Alloy

L53405 L53420 L53425 L53454 L53455 L53456

11% Antimonial Lead Linotype Alloy Linotype-Special Alloy Type Metal Alloy Linotype B (Eutectic) Alloy Type Metal Alloy

Chemical composition" Pb 88.9 nom Sb 8.0 nom Sn 3.1 nom Pb 88 nom Sb 8.0 norn Sn 4.0 nom Pb 91 nom Sb 9.0 nom Pb 90 nom Sb 9 nom Sn 1 nom Pb 86 nom Sb 9 nom Sn 5 nom As 0.15 max Cu 0.50 max Pb 89-91 Sb 9.25-10.75 Zn 0.01 max A1 0.005 max As 0.25 max Bi 0.10 max Cd 0.05 max Cu 0.50 max Fe 0.1 max Pb rem Sb 9.5-10.5 Sn 5.5-6.5 Zn 0.005 max Al 0.005 max As 0.25 max Bi 0.01 max Cd 0.05 max Cu 0.50 max Pb rem Sb 9.0-1 1.0 Sn 5.0-7.0 Zn 0.005 max. Other total of others 0.20 max A1 0.005 max As 0.25 max Bi 0.10 max Cd 0.05 max Cu 0.50 max Fe 0.10 max Pb rem Sb 9.5-10.5 Sn 5.5-6.5 Zn 0.005 max Pb 89 nom Sb 11 nom Pb 86 nom Sb 1 1 nom Sn 3 nom Pb 84 nom Sb 11 nom Sn 5 nom Pb 85 nom Sb 12 nom Sn 3 nom Pb 84 nom Sb 12 nom Sn 4 nom Pb 83 nom Sb 12 nom Sn 5 nom

Cross-referenced specifications

ASTM B102 (YlOA)

SAE 5460. Alloy 13

ASTM B23 (Alloy 13)

DIN 16512

DIN 16512

L53460 L53465

Type Metal Alloy Lead Alloy

L53470

CT Metal

L53480

Arsenical Lead-G Babbitt

L53505

CT Metal

L535 10 L53530 L53550 L53555 L53558 L53560

Stereotype-General Alloy Stereotype-Flat Alloy 15% Antimonial Lead Lead Alloy Type Metal Alloy Lead-base Die Casting Alloy

L53565

Lead-base White Metal Bearing Alloy

L53570 L53515 L53580 L53585

Monotype-Ordinary Alloy Stereotype-curved Alloy Rules Monotype Alloy Lead-base White Metal Bearing Alloy

Pb 82 nom Sb 12 nom Sn 6 nom Cu 0.05 Pb 77.5 nom Sb 12.5 nom Sn 10.0 nom As 0.4 nom Pb 86 nom Sb 12.75 nom Sn 0.75 nom As 3.0 nom Pb 83.5 nom Sb 12.75 nom Sn 0.75 nom As 1 nom Pb 85 nom Sb 13 nom Sn 1 nom Pb 80.5 nom Sb 13 nom Sn 6.5 nom Pb 80 nom Sb 14 nom Sn 6 nom Pb 85 nom Sb 15 nom Pb 83 nom Sb 15 nom Sn 2 nom Pb 81 nom Sb 15 nom Sn 4 nom Al 0.01 max As 0.15 max Cu 0.50 max Pb 79-81 Sb 14-16 Sn 4-6 Zn 0.01 max Al 0.005 max As 0.30-0.60 Bi 0.10 max Cd 0.05 max Cu 0.50 max Fe 0.10 max Pb rem Sb 14.0-16.0 Sn 4.5-5.5 Zn 0.005 max Pb 78 nom Sb 15 nom Sn 7 nom Pb 77 nom Sb 15 nom Sn 8 nom Pb 75 nom Sb 15 nom Sn 10 nom Al 0.005 max As 0.30-0.60 Bi 0.10 max Cd 0.05 max Cu 0.50 max Fe 0.10 max Pb rem Sb 14.0-16.0 Sn 9.3-10.7 Zn 0.005 max

ASTM E l 0 2 (YT155A)

ASTM B23 (Alloy 8); FED QQT-390 Grade 6

ASTM B23 (Alloy 7) FED QQ-T-390-Grade 1 1

Table 6 Unified No.

-4

Continued

N

Description

L53620

Lead-base Bearing Alloy

L.53650 L53655 L53685 L537 10

Display Monotype Alloy Type Metal Alloy Lanston Standard Case Type Monotype Alloy Hard Foundry Type Alloy

L53740 L537.50 L53780

Monotype Case Type Alloy Monotype Case Type Alloy Hard Foundry Type Alloy

L53790 L5379.5 L54030 L54050 L542 10

Type Metal Alloy Type Metal Alloy Alloy 1/2C-Cable Sheathing Alloy Alloy C-Cable Sheathing Alloy 2% Tin Solder

LS42 1 1

2% Tin Antimonial Solder

Chemical composition" Al 0.005 max As 0.8-1.4 Bi 0.10 max Cd 0.05 max Cu 0.6 max Fe 0.10 rnax Pb rem Sb 14.5-17.5 Sn 0.8-1.2 Zn 0.005 max Pb 75 nom Sb 17 nom Sn 8 norn Pb 74 nom Sb 17 nom Sn 9 nom Pb 72 nom Sb 19 nom Sn 9 nom

Cu 1.5 nom Pb 58.5 nom Sb 20 nom Sn 20 nom Pb 67 nom Sb 24 nom Sn 9 nom Pb 6 4 nom Sb 24 nom Sn 12 nom Cu 1.5 nom Pb 60.5 nom Sb 25 nom Sn 13 nom Pb 67 nom Sb 28 nom Sn 5 nom Pb 65.5 nom Sb 29 nom Sn 5.5 norn Cd 0.075 nom Pb 99.7 nom Sn 0.2 nom Cd 0.15 nom Pb 99.4 nom Sn 0.4 nom Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 98 nom Sb 0.12 max Sn 1 .5-2.5 Zn 0.005 max A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 98 nom Sb 0.20-0.50 Sn 1.5-2.5 Zn 0.005 max

Cross -referenced specifications ASTM B23 (Alloy 15)

DIN 16512

DIN 16512 DIN 16512

ASTM B32 (Alloy 2A): DIN 1707L-PbSn2 ASTM B32 (Alloy 2B)

L54250

SAE Solder Alloy 9B

L54280 L543 10 L54320

Solder Alloy Electrotype Curved Plate Alloy 5/95 Solder

L5432 1

5% Tin Antimonial Solder

54322

SN5 Solder

L54360

Solder Alloy

L54370 L54410 L545 10 L54520

Plated Overlay for Bearings 8% Tin Solder Plated Overlay for Bearings 10190 Solder

L54525

88- 10-2 Solder

Al 0.005 max As 0.40-0.60 Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb rem Sb 4.90-5.40 Sn 2.50-2.75 Zn 0.005 max. Other elements total 0.08 max Pb 91.9 nom Sb 5.1 nom Sn 3.0 nom Pb 93 norn S b 3 nom Sn 4 nom A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 95 nom Sb 0.12 max Sn 4.5-5 Zn 0.005 rnax Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 95 nom Sb 0.20-0.50 Sn 4.5-5.5 Zn 0.005 max Ag 0.015 max Al 0.005 max As 0.02 max Bi 0.25 max Cd 0.001 max Cu 0.08 max Fe 0.02 max Pb rem Sb 0.50 max Sn 4.5-5 Zn 0.005 max. Others: Total 0.08 max As 0.5 nom Pb 90.5 norn Sb 4.0 nom Sn 5.0 nom Pb rem Sn 5.0-9.0. Others: total 3.5 max Pb 92 nom S b 0.3 nom Sn 8 nom Pb rem Sn 8.0-12.0 Others: total 3.5 max Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 90 nom Sb 0.20-0.50 Sn 10 nom Zn 0.005 max Ag 1.7-2.4 AI 0.005 max As 0.02 max Bi 0.03 max Cd 0.001 max Cu 0.08 max Pb rem Sb 0.20 max Sn 9.0-1 1.0 Zn 0.005 max. Others: total 0.10 max

SAE 5473 (Alloy 9B)

BS AU 90. Grade 3AX ASTM B32 (Alloy 5A)

ASTM B32 (Alloy 5B)

FED QQ 5-571 (Sn5)

BS AU 90. Grade 5AX SAE 5460. No. 190 DIN 17017: L-Pb Sn 8(Sb) SAE 5460. No. 19 ASTM B32 (Alloy 10B)

FED QQ-S-571 (Sn 10)

-4 P

Table 6 Continued ~~~~~

Unified NO.

Description

L54530

Solder Alloy

L54540 L54555

Solder Alloy Solder Alloy

L.54560

15/85 Solder

L54.570

Solder Alloy

L54580 LS46 10

Type Metal Alloy Solder Alloy

L547 10 L547 1 1

20% Tin Solder Solder Alloy 20B

L547 12

Solder Alloy 20C

Chemical composition" As 0.5 nom Pb 85.5 nom Sb 4 nom Sn 10 nom Pb 87.5 nom Sb 0.45 nom Sn 12 nom A1 0.005 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb rem Sb as specified 2.75 max Sn 14.0-15.0Zn 0.005 max. Other elements total 0.08 max A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 85 nom Sb 0.20-0.50Sn 15 desired Zn 0.005 max Pb 82.5 nom Sb 2.5 nom Sn 15 norn

Pb 80.5 nom Sb 4.5 nom Sn 15 nom Al 0.005 max Bi 0.25 rnax Cu 0.08 max Fe 0.02 max Pb rem Sb 1.25-1.75Sn 19.0-20.0 Zn 0.005 max Other elements total 0.08 max Pb 80 nom Sb 0.2nom Sn 20 nom A1 0.005 max As 0.02max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 80 nom Sb 0.2-0.5 Sn 20 desired Zn 0.005 max A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02max Pb 79 nom Sb 0.8-1.2 Sn 20 desired Zn 0.005 max

Cross-referenced specifications

BS AU 90. Grade lOAX DIN 1707: L-Pb Sn 12Sb SAE 5473. No. 6B

ASTM B32 (Alloy 15B)

SAE 5743, No. 6B;BSAU9, Grade 16AX DIN 16512 SAE 5743, No. 5B

BS 219. Grade V ASTM B32 (Alloy 20B) FED QQ-S-571 (Pb 80)

9 p1

ASTM B32 (Alloy 2OC) FED QQ-S-571 (Sn 20)

P,

cN

L547 13 L547 I5 L54720

L54721

Solder Alloy Solder Alloy 25/75 Solder

Solder Alloy 25B

L54722

Solder Alloy 25C

L54727

Lead-base Bearing Alloy

L54750 L54755 L54805 L548 10 L548 15

Silver-loaded Solder Fusible Alloy Solder Alloy Fusible Alloy Solder Alloy

L54820

30170 Solder

L5482 1

Solder Alloy

Pb 77 nom Sb 1.2 nom Sn 22 nom Pb 74 nom Sb 3 nom Sn 23 nom A1 0.005 max As 0.02 max Bi 0.25 rnax Cu 0.08 max Fe 0.02 max Pb 75 norn Sb 0.25 max Sn 25 nom Zn 0.005 max Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 75 nom Sb 0.20-0.50 Sn 25 desired Zn 0.005 max Al 0.005 max As 0.02 max Bi 025 max Cu 008 max Fe 0.02 max Pb 73.7 nom Sb 1.1-1.5 Sn 25 desired Zn 0.005 max Cu 3 nom Pb 59 nom Sb 13 nom Sn 25 nom Ag 3 nom Pb 70 nom Sn 27 nom Bi 21.5 nom Pb 51.5 nom Sn 27 nom Pb 70.5 nom Sb 1.5 nom Sn 28 nom Bi 28.5 nom Pb 43 nom Sn 28.5 nom A1 0.005 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb rem Sb 0.75-1.25 Sn 29.0-30.0 Zn 0.005 max Other elements total 0.08 max A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 70 nom Sb 0.25 max Sn 30 desired Zn 0.005 max Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 70 nom Sb 0.20-0.50 Sn 30 desired Zn 0.005 max

SAE No. 48 BS441. Grade 22A ASTM 7332 (Alloy 25A)

9

0

'CI

?!=. (D

u)

ASTM B32 (Alloy 25B)

2 F P)

P

ASTM B32 (Alloy 25C)

DIN 1741

SAE 5473. No. 3B

ASTM B32 (Alloy 30A); BS219 Grade J

ASTM B32 (Alloy 30B) FED QQ-S-571 (Pb 70)

Table 6

2

Continued

~

Unified No.

Description

L54822

Solder Alloy

L54827 L54829 L54830 L54832 L54833 L54835 L54840 L54850

Type Metal Alloy Fusible Alloy Fusible Alloy Solder Alloy Solder Alloy Fusible Alloy Fusible Alloy 35/65 Solder

L5485 1

Solder Alloy

L548.52

Solder Alloy

L54855 L54860 L54865 L54905

Silver-loaded Solder Alloy Fusible Alloy Fusible Alloy Antimonial Solder Alloy

Chemical composition"

Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 68.4 nom Sb 1.4-1.8 Sn 30 desired Zn 0.005 max Pb 64 nom Sb 6 nom Sn 30 nom Bi 20 nom Pb 50 nom Sn 30 nom Bi 30.8 nom Pb 38.4 nom Sn 3 0 . h m Pb 66.7 nom Sb 1.8 nom Sn 3 1.5 nom Pb 65 nom Sb 3 nom Sn 32 nom Bi 33.3 nom Pb 33.4 nom Sn 33.3 nom Bi 32 nom Pb 34 nom Sn 34 nom Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 65 nom Sb 0.25 max Sn 35 nom Zn 0.005 max A1 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 65 nom Sb 0.20-0.50 Sn 35 nom Zn 0.005 max Al 0.005 max As 0.02 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 63.2 nom Sb 1.6-2.0 Sn 35 nom Zn 0.005 max Ag 3.0 nom Pb 61.5 nom Sn 35.5 nom Bi 21 nom Pb 43 nom Sn 36 nom Bi 21 nom Pb 42 nom Sn 37 nom A1 0.005 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb rem Sb 1.5-2.0 Sn 38.0-38.5 Zn 0.005 max. Other elements total 0.08 max

Cross-referenced specifications

ASTM B32 (Alloy 30C) FED QQ-S-571 (Sn 30) DIN 16512

BS 219. Grade L

ASTM B32 (Alloy 35A)

ASTM B32 (Alloy 35B) FED QQ-S-571 (Pb 65) ASTM B32 (Alloy 35C) FED QQ-S-571 (Sn 35)

SAE 5473. No. 2B

L54910 L549 15

Fusible Alloy 40160 Solder

L549 16

Solder Alloy

L549 18

Solder Alloy

L54925

Lead-base Bearing Alloy

L54930 L54935 L54940

Fusible Alloy Fusible Alloy Solder Alloy

L54945 L54950

Silver-loaded Solder 45/55 Soldeer

L5495 1

Solder Alloy

L54955 L55005 L55030

Solder Alloy Solder Alloy 50150 Solder

Bi 12.6 norn Pb 47.5 norn Sn 39.9 norn Al 0.005 max As 0.02 rnax Bi 0.25 max Cu 0.08 max Fe 0.02 rnax Pb 60 nom Sb 0.12 rnax Sn 40 norn Zn 0.005 rnax Al 0.005 rnax As 0.02 rnax Bi 0.25 rnax Cu 0.08 rnax Fe 0.02 rnax Pb 60 nom Sb 0.2-0.5 max Sn 40 norn Zn 0.005 rnax A1 0.005 rnax As 0.02 rnax Bi 0.25 rnax Cu 0.08 rnax Fe 0.02 rnax Pb 58 norn Sb 1.8-2.4 Sn 40 norn Zn 0.005 max Cu 2 nom Pb 46 nom Sb 12 nom Sn 40 nom Bi 4 norn Pb 55.5 norn Sn 40.5 norn Bi 14 norn Pb 43 nom Sn 43 nom Al 0.005 rnax Bi 0.25 rnax Cu 0.08 rnax Fe 0.02 rnax Pb rern Sb 1.5-2.0 Sn 43.0-43.5 Zn 0.005 rnax. Other elements total 0.08 rnax Ag 1 norn Pb 55 nom Sn 44 norn Al 0.005 max As 0.03 max Bi 0.25 rnax Cu 0.08 rnax Fe 0.02 rnax Pb 55 norn Sb 0.12 max Sn 45 nom Zn 0.005 rnax Al 0.005 rnax As 0.03 max Bi 0.25 rnax Cu 0.08 rnax Fe 0.02 max Pb 55 nom Sb 0.20-0.50 Sn 45 norn Zn 0.005 rnax PB 52.5 norn Sb 2.5 nom Sn 45 norn Pb 52 norn Sn 48 norn Al 0.006 rnax As 0.03 rnax Bi 0.25 rnax Cu 0.08 rnax Fe 0.02 rnax Pb 50 nom Sb 0.12 max Sn 50 norn Zn 0.005 rnax

7

ASTM B32 (Alloy 40A); DIN 1707: L-Pb Sn 40 ASTM B32 (Alloy 40B); FED QQ-S-571 (Sn 40)

=0 !! 0cn 0, r

(D

b

ASTM B32 (Alloy 40C)

Q D 3 Q

-

D DIN 1741

P 0

U v)

SAE 5473. Grade 1B

AMS 4750; ASTM B32 (Alloy 45A) ASTM B32 (Alloy 45B)

BS 219 Grade M ASTM B32 (Alloy 50A) DIN 1707: L-Sn 50 Pb

4 4

Table 6

Continued

4

Q)

Unified No.

Description

L5503 1

Solder Alloy

L55033 L55035 L55036 L55038 L55040 L55045 L55065 L55070 L55110

Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Tine-Lead Solder

L55111

Tin-Lead Solder

L55113 L55514 L55116 L55 120 L55 122 L55 124 L55 133 L55 I40

Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder

Chemical composition” A1 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 50 nom Sb 0.20-0.50 Sn 50 nom Zn 0.005 max Sn 50 Sb 1.8 Pb rern Sn 50 Sb 2.8 Pb rem Sn 50 Sb 5 Pb rern Sn 50 Ag 3 Pb rern Sn 50 Cu 1.1 Pb rem Sn 50 Cu 4.0 Sb 13.0 Pb rem Sn 50.7 Sb 3.3 Pb rern Sn 55 Pb 45 A1 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 40 nom Sb 0.12 max Sn 60 nom Zn 0.005 max A1 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 40 nom Sb 0.20-0.50 Sn 60 nom Zn 0.005 max Sn 60 Cu 0.2 Pb 40 Sn 60 Cu 1.3 Pb 39 Sn 60 Ag 3.5 Pb 36.5 Sn 60 Cu 3.0 Sb 10 Pb rem Sn 60 Cu 4.0 Sb 13 Pb rem Sn 60 Bi 25.5 Pb 14.5 Sn 62 Ag 2 Pb 36 A1 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 37 nom Sb 0.12 rnax Sn 63 norn Zn 0.005 max

Cross-referenced specifications ASTM B32 (Alloy SOB) FED QQS-571 (Sn 50) DIN 1707: L-Sn 50 Pb Sb BS 219 Grade B Similar to DIN 1707 DIN 1707: L-Sn 50 Pb Cu DIN 1742 DIN 1707 ASTM B32 (60A) B486 (60A) FED QQ-S-571 (Sn 60) ASTM B32 (60B) B486 (60B) DIN 1707: L-Sn 60 Pb Cu DIN 1707: L-Sn 60 Pb Cu Z DIN 1707: L-Sn 60 Pb Ag BS 3332 DIN 1742 QQS-571 (Sn 62) AMS 4751; ASTM B486 (grade 53A) B32 (Grade 63A); FED QQ-S-571 (Sn 63); DIN 1707; L-Sn 63Pb

8

3

L55141

Tin-Lead Solder

L55 145 L55150 L55160

Solder Alloy Solder Alloy Tin-Lead Solder

L55 161

Tin-Lead Solder

L55195

Tin-Silver Solder

L55 196

Tin-Silver Solder

L55 197

Modem Pewter

L55 198

Tin-Silver Solder

L55210

Battery Alloy

L55230

Battery Alloy

L55260 L55290

Battery Alloy Lead-Strontium Alloy

Al 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 37 nom Sb 0.20-0.50 Sn 63 nom Zn 0.005 max Sn 63 Ag 1.4 Pb 35.6 Sn 65 Sb 0.6 max Pb rem Al 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 30 nom Sb 0.20 nom Sn 70 nom Zn 0.005 max AI 0.005 max As 0.03 max Bi 0.25 max Cu 0.08 max Fe 0.02 max Pb 30 nom Sb 0.20-0.50 Sn 70 nom Zn 0.005 max Ag 3.6-4.4 A1 0.005 max As 0.05 max Bi 0.15 max Cu 0.08 max Fe 0.02 max Pb 0.20 max Sb 0.20-0.50 Sn 96 nom Zn 0.005 max Ag 3.6-4.4 As 0.05 max Cd 0.005 max Cu 0.20 max Pb 0.10 max Sn rem Zn 0.005 max As 0.05 max Cu 1.0-2.0 Fe 0.015 max Pb 0.05 max Sb 1.0-3.0 Sn 95-98 Zn 0.005 max Ag 3.3-3.7 A1 0.005 max As 0.05 max Bi 0.15 max Cu 0.08 max Fe 0.02 max Sb 0.20-0.50 Sn 96.5 nom Zn 0.005 max Pb 99.6 nom Sn 0.3 nom. Ca 0.06 nom, Sr 0.06 nom A1 0.03 nom Pb 99 nom Sn 0.8 nom. Sr 0.16 nom A1 0.03 nom Pb 99.8 nom. Sr 0.2 nom Pb 98 nom. Sr 2 nom

ASTM B32 (63s); B486 (63B)

DIN 1707: L-Sn 63 Pb Ag BS219 Grade A ASTM A32 (70A) FED QQ-S571 (Sn 70) ASTM B32 (70B); B486 (70B)

ASTM B486 (96 TS)

FED QQ S-571 (Sn 96)

ASTM B560(3)

ASTM B32 (96.5 TS)

"The chemical compositions listed are for identification purposes and should not be used in lieu of cross-referenced specifications.

4 (0

Chapter 2

80

Table 7 ANSI/ASTM B29-92 Specification of Chemical Requirements of Retined Lead [ 1 13 I. (Courtesy of American Society for Testing Materials, West Conshohocken, PA.) Composition (wt.%) Grade

Low Bi, low Ag, max" Pb; max" purePb;

Refined pure

Pure Pb; lead' max L50049 0.001 0.001 0.00 1 0.002 0.00 15 0.005 0.05 0.001

UNS No. Sb As Sn Sb, As, and Sn

L50006 0.0005 0.0005 0.0005

L5002 1 0.0005 0.0005 0.0005

-

-

cu

0.00I O 0.0010 0.00 1 5 0.0005 0.0001 0.0002 0.0002 99.995

0.00I O 0.0025 0.025 0.0005 0.0001 0.0002 0.00 1 99.97

Ag Bi Zn Te Ni Fe Pb (min) by difference

-

0.00 I 0.00 I 99.94

Chemical-copper L51121 0.001 max 0.001 max 0.001 max 0.002 max 0.040-0.080 0.020 max 0.025 max 0.001 max -

0.002 max 0.002 max 99.90

"This grade is Intended for chemical applications where low silver and low bismuth contents are required. hThis grade I S intended for lead-acid batter applications. 'This grade IS Intended for applications requiring corrosion protection and formability.

in fcc metals such as lead. However, it is rare that one finds a perfect crystal with no defects, and deformation occurs in real materials before the ideal strength level is reached through the movement of dislocations or vacancies. At low temperatures, the plastic deformation can occur by dislocation glide that is limited by a lattice resistance (or Peierls' stress), discrete obstacles, and phonon or other drags. The shear-strain rate can be given by 11 161

where u,,~is the density of mobile dislocations, h is the Burgers vector, and v is the average dislocation velocity. The dislocation density varies with stress level andtemperatureand is proportional to (u/F)?at steadystate, where U is the stress and p is the shear modulus. The velocity of dislocation depends on the mobility, which is a function of the temperature, frictional

Properties andof Lead

Its Alloys

81

Table 8 ASTM 749-85 (Reapproved 1991) ChemicalRequirements for Lead-Alloy Strip, Sheet, and Plate Products [ 1 141. (Courtesy of American Society for Testing Materials, West Conshohocken, PA.) Composition (wt.%)

L50042 corroding lead

L5 I 120 common chemical

L50049

L51121 copperbearing

L5 1 123 tellurium

-

-

... 0.002 0.00 I

__

Element Ag,0.020 max0.020 0.020 0.0150.0015 0.020 Ag, min Cu, max 0.080 0.080 0.0800.0015 0.0015 Cu, min - 0.040 0.040 0.040 Ag + Cu, max 0.0025 As + Sb + Sn, max 0.002 0.002 0.002 0.002 maxZn, 0.00 I 0.00 0.001 1 0.002 Fe, max 0.002 0.002 0.002 0.002 0.025 Bi, max 0.025 0.005 0.050'' 0.050 Pb difference), (by 99.94 99.94 99.90 99.90 0.035-0.060 min

0.00 1

Te

"By agreement between the purchaser and supplier, Bi levels of up to O.lS% Inay be allowed.

resistance on the slip plane due to the lattice, and resistance due to obstacles such as solutes, precipitates, forest dislocations, and other defects. AG(o,,), the activation energy to overcome the obstacle at a stress level U,, is given by [l171

AG(a,) = AF

[ (!q 1 -

where AF is the activation energy required to overcome the obstacle in the absence of external stress, T is the stress required to overcome the obstacle without assistance from thermal energy, and p and q are constants between 0 and 1 and between l and 2 , respectively. Another mechanism operative at low temperatures that could result in a limited amount of plastic strain is twinning. The tendency to twin increases with decreasing stacking fault energy and Pb has a reasonably low stacking fault energy. At higher temperatures, the materials show time-dependent plastic destress. This could occur by thermally formation or creep under an applied activated movement of dislocations under an applied stress (the region of grainpower-lawcreep) or by the diffusional transport of atomsfroma

Table 9

Some of the Telephone and Power Cable Alloys as per UNS number [28]

Nominal composition (wt.%)

UNS No.

Alloy designation

L52605

1% Antimony Lead

L50310

F-3 Gencalloy “A”

Tellurium Cable Alloy L54050 L54030 L52570 L52540

BS801 BS801 BS801 BS801

Alloy Alloy Alloy Alloy

C 1/2C B D

As

Sn

Bi

Te

0.04 0.15 0.10

to 0.17 0.18 to 0.20

0.10 0.09 to 0.13 0.13 to 0.14 0.4 0.2

0.10 min.

0.06 to 0.08

0.07 to 0.10

Sb

cu

Ag

1 .o

0.0015

0.005 max.

min. min.

max. min. 0.04 to 0.06

min.

min.

Other

Balance Balance Balance

0.01 max.

min

Balance

Cd 0.15 Cd 0.075 0.85 0.5

Pb

0.06 Cd 0.25

Balance Balance Balance Balance

Properties andof Lead

Its Alloys

83

Table 10 Antimonial Lead Storage Battery Alloys Industries Association, New York.)

1281. (Courtesy of Lead

Nominal or preferred composition (wt.%) UNS Lead Copper No. Arsenic Tin Antimony 0.2 L52760 0.3 L52765 L52770 L52840

2.75 2.75 2.9 2.9

0.075

0.18

0.075

0.3

0.3 0.3

0.04 0.05

0.15 0.15

Table 11 Calcium-LeadStorageBatteryAlloys [28]. (Courtesy of Lead Industries Association, New York.)

Nominal or preferred composition (wt.%) No.

UNS L50760 L50770 L50736 L50737 L50775 L50780

0.075 0. I O

-

0.065 0.065

0.2 0.5

0.10 0.10

0.3

Balance Balance Balance Balance Balance Balance

0.5

Table 12 Type Metal Alloys 1281.(Courtesy of Lead Industries Association, New York.)

Nominal or preferred composition (wt.%) Antimony Lead Designation TinNo.UNS L53425 L52830 L53530 L53570 L53750

Linotype Electrotype Stereotype Monotype Foundry 24 Type

5

11

3

3

84 94

6 7

14

82

15

78 64

12

Balance Balance Balance Balance

Chapter 2

84

Table 13 Casting Alloys 1281. (Courtesy of Lead Industries Association, New York.) ~

~~

~~~

Nominal or preferred composition (wt.%) Antimony Tin No. UNS Arsenic L53560 L53340 L53470

(max.) Copper (max.) Lead 4-6

0.5 14-16 0.5 9.25- 10.75 0.75 12.75 -

0.15 0.15 0.4

79-x 1 89-9 1 86

0

boundary region normal to compressive stress to a boundary region that is normal to the applied stress (in the diffusional creep region). Diffusion can become significant at temperaturesabove 0.37" for metals and 0.47" for alloys. At higher stress levels, creep that occurs still involves dislocation movement and the steady-state creep rate is proportional to U". Hence, the creep under these conditions is referred to as power-law creep. Power-law creep could occur by dislocation glide on the slip planes or glide-plus-climb. When it is controlled by lattice-diffusion-controlled climb, it is referred to as "high-temperature creep." This occurs at temperatures >0.6TM.The strain rate i n this region is given by an empirical relationship [ 1181

Here D,, is the lattice diffusion co-efficient and A is an empirical constant. The value of observed IZ varies from 3 to about 10. These equations should be treated as empirical because of uncertainties in the relationship

Table 14 Lead-BasedBearingMetals12x1.(Courtesy Association, New York.)

of LeadIndustries

Nominal or preferred composition (wt.%)

onyTin

No.

UNS ~~

13

L54727 L53560 L53620 L53320

-

25 5 I 5

15

15

9

59

x0 0.15 I .4

0.5

-

-

0.6

x2 86

aUTI

Table 15 Lead-Tin Solder Alloys [28]. (Courtesy of Lead Industries Association, New York.) Composition (wt.7c) UNS No.

L542 10 L54320 L54520 L54560 L547 10

Tin

2 5 10

15 20

?! $ v)

Temperature ("C)

Lead

Solidus

Liquidus

Pasty range

98 95 90 85 80

316 305 267 226 182

32 1 312 302 288 277

5 7 35 62 95

L54720 L.54820 L54850 L549 15

25 30 35 40

75 70 6.5 60

182 182 182 182

266 255 247 237

84 73 65 55

L549.50

45

55

182

227

45

L55030

50

50

182

216

34

L 13600

60

40

182

190

8

L13630

63

37

182

182

0

Uses Side seams for can manufacturing For automobile radiators For coating and joining metals

For coating and joining metals; for filling dents or seams in automobile bodies For machine and torch soldering General purpose and wiping solder Wiping solder for joining lead pipes and cable sheaths; for automobile radiator cores and heating units For automobile radiator core and roofing seams For general purpose use; use most popular of all Primarily used in electronic soldering applications where low soldering temperatures are required Lowest melting (eutectic) solder for electronic applications

0, r (D m m

3 P

-

D

2 b

5

86

Chapter 2

Table 16

Most CommonSilver-ContainingSolders [28]. (Courtesy of Lead Industries Association, New York.) Composition (wt.%)

Temperature ("C)

Solidus Liquidus Lead Silver TinNo. UNS ~ _ _

L50131 L55 133 L50151

1

I .5

62

2.0 2.5

-

97.5 36.0 97.5

~~~~

309 179 304

309 189 304

between applied stress and dislocation densities, and theoretical models of flow. The region where creep is limited by core-diffusion-controlled climb is referred to as the "low-temperature-creep" region. Here, the lattice diffusion coefficient is replaced by D,,,,, which varies as (a,Jp)' and, therefore, In some materials, at very low stress levels, the creep rate varies as (a,,/p)'i'2. the strain rate varies linearly with u,,/p,suggesting that the dislocation density under these conditions remains constant. This region, referred to as the Harper-Dorncreep [ 1 19, 1201 regime, is observed in verylarge-grained material, when diffusional creep fields are suppressed. There is a region at In this high stress levels (>lo-.' p) where the powerlawbreaksdown. region, the controlling mechanism transitions from climb-plus-glide to glide alone. At low stress levels (stress < 5 X lo-" p), linear viscous creep occurs at rates higher than that from diffusional creep. The dislocation creep mechanism that results in this linear viscous creep is referred to as Harper-Dom creep and occurs under conditionsthat maintain constant dislocation density. At very high temperatures (>0.6TM)and stress levels, power-law creep may be accompanied by repeated recrystallization. Following each recrystallization step, the dislocation density drops allowing for a period of pri-

Table 17 Typical Solder Alloys with Their Melting Points 1281. (Courtesy of Lead Industries Association, New York.) point ("C)

Composition Melting (wt.%)

UNS No. ~

47 21

~~~

Tin

Bismuth Indium Cadmium

Lead

Solidus Liquidus

~~~~~

22.6L50620 5.3 49.9 12.0 L50640 L50645 50.0 L50665 L56680

8.3 19.1

44.7

9.3 15.5 -

52.5 55.5

.o

-

-34.5 - 95 -

6.2 -95 124 -124

18.0

32.0 44.5

58 70

58

78

U

a '0

Table 18 Electrical Properties of Lead Alloys [28]. (Courtesy of Lead Industries Association, New York.) Alloy composition" Pb >99.94 Pb-( 1.3- 1.7)Ag Pb-1.5 Ag-5 Sn Pb-(2.3-2.7)Ag Pb-(2.3-2.7)Ag Pb-2.5 Ag-2 Sn Pb-5 Ag Pb-5 Ag-5 Sn Pb-5 Ag-5 In Pb-(5-6)Ag Pb-0.15 As-0.1 Sn-0.1 Bi Pb-42 Bi-11 Sn-9 Cd Pb-42.9 Bi-5. I Cd-7.9 Sn-4 Hg- 18.3 In Pb-44.7 Bi-5.3 Cd-8.3 Sn-19.1 In Pb-48 Bi-14.5 Sn-9 Sb Pb-49 Bi-21 In-I2 Sn Pb-50 Bi-10 Cd-13.3 Sn Pb-5 1.7 Bi-8.1 Cd Pb-52.5 Bi-15.5 Sn Pb-55.5 Bi Pb-0.065 Ca-0.7 Sn Pb-0.065 Ca-1.3 Sn

4 g

Conductivity (%IACS)

Resistivity

L50OOI -L50042 L50132 L50 134 L50 150 L50151 L50152 L50 170 L19171 L10172 L50 180 L503 10

8.3%

206.43

5

L50605 L506 10

4%

Fusible Alloy

L50620

4.5%

Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Battery Grid Alloy Battery Grid Alloy

L50630 L50640 L50650 L50660 L50665 L50680 L50740 L50750

3% 3% 4 Yo

219 220

03

UNS No.

Common name Corroding Lead Solder Alloy-Grade Ag Solder Alloy-Grade 5s Solder Alloy-Grade Ag Solder Alloy-Grade Ag Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy-Grade Ag Arsenical Lead Cable Sheathing Alloy Fusible Alloy Fusible Alloy

1.5 2.5 2.5

5.5

(nn-m)

u)

3% 4

a3 a3

Table 18 Continued Alloy composition Pb-0.07 Ca Pb-0.1 Ca-0.3 Sn Pb-0.1 Ca-0.5 Sn Pb-0.1 Ca-1 Sn Pb-17 Cd

Pb-4.76 In-2.38 Ag Pb-5 In Pb-5 In-2.5 Ag Pb- 19 In Pb-20 In Pb-25 In Pb-40 In Pb-40 In-40 Sn Pb-50 In Pb-60 In Pb-70 In Pb-80 In-5 Ag Pb-I S b Pb-1.2 Sb-0.8 Ga Pb-2 Sb

Common name Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Lead-Cadmium AlloyEutectic Copperized Lead Lead-Indium-Silver Solder Alloy Lead-Indium Solder Alloy Lead-Indium-SiIver Solder Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy 1% Antimonial Lead Lead-Antimony-Gallium Alloy 2% Antimonial Lead

UNS No.

Conductivity (YoIACS)

Resistivity (nR-m)

L50760 L50775 L50780 L50790 L50940

218 219 219 212

L51110-L51123 and L5 1125 L51510

206 5.5%

L51511 L51512

5.5%

L51.530 L5 1532 L51535 L5 1540 L5 1545 L5 15.50 L5 1560 L5 1570 L5 1585 L.52605 LS26 18 L52705

5.1%

4.5% 4.6% 5.2%

7.0% 8.8% 13%

Pb-2.5 Sb-2.5 Sn Pb-3 Sb-3 Sn Pb-4 Sb Pb-6 Sb Pb-8 Sb Pb-9 Sb Pb-(9.5- 10.5)Sb-(5.56.5)Sn Pb-ll Sb-3 Sn Pb-l 1 Sb-5 Sn Pb-12 Sb-4 Sn Pb-13 Sb-6.5 Sn Pb-14 Sb-6 Sn Pb-( 14- 16)Sb-(4.5-5.5)Sn Pb-15 Sb-7 Sn Pb-15 Sb-8 Sn Pb-15 Sb-10 Sn Pb-( 14-16)Sb-(9.3- 10.7)Sn Pb-( 14.5-1 7.5)Sb-(0.81.2)Sn Pb-17 Sb-8 Sn Pb-19 Sb-9 Sn Pb-24 Sb-12 Sn Pb-( 1.5-2.5)Sn Pb-3 Sn-5.1 Sb

Electrotype-General Electrotype-General 4% Antimonial Lead 6% Antimonial Lead 8% Antimonial Lead 9% Antimonial Lead Lead-base Bearing Alloy

L52730 L52830 L52901 L53105 L53230 L53305 L53346

Linotype Alloy Linotype-Special Alloy Linotype B (Eutectic) Alloy Stereotype-General Alloy Stereotype-Flat Alloy Lead-base White Metal Bearing Alloy Monotype-Ordinary Alloy Stereotype-Curved Alloy Rules Monotype Alloy Lead-base White Metal Bearing Alloy Lead-base Bearing Alloy

L53420 L53425 L53455 L53510 L53530 L53565

6.1%

282

L.53570 L.53575 L53580 L5358.5

6.0% 6.070

286

Display Monotype Alloy Lanston Standard Case Type Monotype Alloy Monotype Case Type Alloy 2% Tin Solder Solder Alloy

L.53650 L53685

L53620

L53750 LS42 10 L54280

7.7% 7.6% 7.5% 7.4% 6.0%

2.53 26.5 27 1 287

=i v)

2 -

0 Y v)

Table 18 Continued ~

Alloy composition Pb-4 Sn-3 Sb

Pb-(4.5-5.5)Sn-(O.2-O.S)Sb Pb-5 Sn-4 Sb-0.5 As Pb-8 Sn-0.3 Sb Pb-10 Sn-(0.2-0.5)Sb Pb-(9- 1 1)Sn-( 1.7-2.4)Ag<0.2 Sb Pb-I0 Sn-4 Sb-0.5 AS Pb-12 Sn-0.45 Sb Pb-15 Sn-(0.2-0.5)Sb Pb-15 Sn-2.5 Sb Pb-20 Sn-(0.2-0.5)Sb Pb-20 Sn-(0.8-1.2)Sb Pb-22 Sn-1.2 Sb Pb-25 Sn-(0.2-0.5)Sb Pb-25 Sn-( 1.1-1 S)Sb Pb-28 Sn-1.5 Sb Pb-30 Sn-4.25 Sb Pb-30 Sn-( 1.4- 1.8)Sb Pb-31.5 Sn-1.8 Sb Pb-35 Sn-~0.25 Sb

Common name

~

UNS No.

Electrotype Curved Plate Alloy 5% Tin Antimonial Solder Solder Alloy 8% Tin Solder 10/90 Solder 88- 10-2 Solder

L5432 1 L54360 L544 10 L54520 L.54525

Solder Alloy Solder Alloy 15/85 Solder Solder Alloy Solder Alloy 20B Solder Alloy 20C Solder Alloy Solder Alloy 25B Solder Alloy 25C Solder Alloy 30170 Solder Solder Alloy Solder Alloy 35/65 Solder

L54530 L54540 L54560 L54570 L547 11 L547 12 L547 13 L5472 1 L54722 L54805 L54820 L.54822 L54832 L548.50

~~

~

~~

Conductivity (%IACS)

~

~~

Resistivity (nR-m)

L543 10 8.8%

19.5

8.2%

9.8%

9.3%

175

Pb-40 Sn-c0.12 Sb

40/60 Solder

Pb-45 Sn-<0.12 Sb Pb-45 Sn-2.5 Sb

45/55 Solder Solder Alloy

Pb-50 Pb-50 Pb-50 Pb-50 Pb-60 Pb-60 Pb-60 Pb-60 Pb-62 Pb-63 Pb-63 Pb-65

50/50 Solder Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder Solder Alloy Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder Solder Alloy Solder Alloy

Sn-<0.12 Sb Sn-2.8 Sb Sn-3 Ag Sn-1.1 Cu Sn-<0.12 Sb ,511-0.2 Cu Sn- 1.3 Cu Sn-3.5 Ag Sn-2 Ag Sn-(0.2-0.5)Sb Sn-1.4 Ag Sn-<0.6 Sb

Pb-70 Sn-(0.2-0.5) Sb

Tin-Lead Solder

Pb(<0.2)-96 Sn-(3.64.4)Ag-(0.2-0.5 Sb)

Tin-Silver Solder

L549 15 L549 18 L54950 L54955 L55015 L55030 L55035 L55038 L55040 L55110 L55113 L55114 L55116 L55 133 L55141 L55145 L55 150 L55 157 L55161 L55 176 L55 195

"Only main alloying elements are given here. For detailed composition information, see Table 6.

10.1%

11%

156

0,

r

8P 3

0 P

11.5%

149.9

L 5

6

1 1.9%

145

11.8%

146

12.7%

135

50001

92

Chapter 2

Table 19 Electrical Resistivity of Dispersion-Strengthened Lead (D.S.L.) Alloys [ 1 151. (Courtesy of Lead Development Association, London.)

Material Lead D.S.L. 0.8% PbO D.S.L. 3.5% PbO D.S.L.(0.2’70 Sb) 1.0% PbO D.S.L. (0.5% Sb) 1.0% PbO Alloy E (0.4% Sn 0.2% Sb) Pb-10%Sb

UNS No.

Electrical resistivity (dl.m)

Test temp. (“C)

206

17 17 20 17 17 17 20

21 1 235

214 218 210 27 6

marycreep.The strain rate oscillates by a factor of 10. This situation is frequently observed in lead. Dynamic recrystallization makes it difficult to predict the creep rates. However, the creep rates willbe higher than that predicted by power-law-creepequations.Alloyingelements that decrease diffusional rates reducecreep rates. Dispersed particles stabilize the cell structure to temperatures as high as 0.8-0.9TM and help suppress dynamic recrystallization at lower temperatures. Whencreepoccurs by the diffusional flowof atomsawayfroma compressive stress region, two possibilities exist. The flow could be limited by lattice diffusion, in whichcase it is referred toas“Nabarro-Herring (NH) creep.” The creep rate in the case of NH creep is given by [ 121 -1231

where d is the grain size and Cn is the atomic volume. At lower temperatures and smaller grain sizes, the diffusional creep may also be limited by grainboundary diffusion and creep under these conditionsis referred to as “Coble creep.” The creep rate for Coble creep is given by [ 123,1241

where Dgh is the grain-boundary diffusion coefficient and 6 is the grain boundary thickness. Equations (4) and ( 5 ) show that a larger grain size reduces both NH and Coble creep. Whenin solid solution, alloying additives that haveahighermeltingpointthan lead wouldtend to adecrease in

3

Table 20 Mass Characteristics of Lead Alloys [28]. (Courtesy of Lead Industries Association, New York.)

m Alloy composition" Pb >99.94 Pb-( 1.3-1.7)Ag Pb-1.5 Ag-5 Sn Pb-(2.3-2.7)Ag Pb-(2.3-2.7)Ag Pb-2.5 Ag-2 Sn Pb-5 Ag Pb-5 Ag-5 Sn Pb-5 Ag-5 In Pb-(5-6)Ag Pb-0.15 As-0.1 Sn-0.1 Bi Pb-42 Bi-I 1 Sn-9 Cd Pb-42.9 Bi-5.1 Cd-7.9 Sn-4 Hg-18.3 In Pb-44.7 Bi-5.3 Cd-8.3 Sn-19.1 In Pb-48 Bi-14.5 Sn-9 Sb Pb-49 Bi-21 In-I2 Sn Pb-50 Bi-10 Cd-13.3 Sn Pb-51.7 Bi-8.1 Cd Pb-52.5 Bi-15.5 Sn Pb-55.5 Bi Pb-0.065 Ca-0.7 Sn Pb-0.065 Ca- 1.3 Sn

Density, (g/cm')

Volume change on freezingh

Common name

UNS No.

Corroding Lead Solder Alloy-Grade Ag 1.5 Solder Alloy-Grade 5s Solder Alloy-Grade Ag 2.5 Solder Alloy-Grade Ag 2.5 Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy-Grade Ag 5.5 Arsenical Lead Cable Sheathing Alloy Fusible Alloy Fusible Alloy

L50001 -L50O42 L50132 L50 134 L50150 L50151 L50152 L50 170 L19171 L10172 L50 180 L503 10 L50605 L506 10

9.45 9.28

-2%

Fusible Alloy

L50620

8.85

- 1.4%

Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Fusible Alloy Battery Grid Alloy Battery Grid Alloy

L50630 L50640 L50650 L50660 L50665 L50680 L50740 L50750

9.50 8.60 9.40 10.25 9.7 1 10.30 11.34 11.34

- 1.5% - 1.5% - 1.7%

4=. (P v)

11.34

11.33 11.28 11.30 11.00 1 1 .oo 11.33

- 1.5% (0

w

Table 20

(0

Continued

P

~

Alloy composition" Pb-0.07 Ca Pb-0.1 Ca-0.3 Sn Pb-0.1 Ca-0.5 Sn Pb-0.1 Ca-1 Sn Pb-17 Cd

Pb-5 In Pb-5 In-2.5 Ag Pb-19 In Pb-20 In Pb-25 In Pb-40 In Pb-40 In-40 Sn Pb-50 In Pb-60 In Pb-70 In Pb-80 In-5 Ag Pb-1 Sb Pb- I .2 Sb-0.8 Ga Pb-2 Sb Pb-2.5 Sb-2.5 Sn

Common name Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Lead-Cadmium AlloyEutectic Copperized Lead Lead-Indium Solder Alloy Lead-Indium-Silver-Solder Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy Lead-Indium Alloy 1% Antimonial Lead Lead- Antimony -Gallium Alloy 2% Antimonial Lead Electrot ype-General

UNS No.

Density, (g/cm')

L50760 L50775 L50780 L50790 L50940

11.34 11.34 11.34 11.34

L5 1 1 IO-L51123. L51125 L51511 L51512

11.34 11.06 1 1.02

L5 1530 L51532 L5 1535 L5 1540 L5 1545 L5 1550 L5 1560 L5 1570 L51585 L52605 L526 18

10.27 10.16 9.97 9.29 7.86 8.86 8.52 8.19 7.85 11.27 11.20

L52705 L52730

11.19

Volume change on freezingh

Pb-3 Pb-4 Pb-6 Pb-8 Pb-9

Sb-3 Sn Sb Sb Sb Sb

Pb-(9.5-10.5)Sb-(S.5-6.5)Sn Pb-11 Sb-3 Sn Pb-1 1 Sb-5 Sn Pb-12 Sb-4 Sn Pb-13 Sb-6.5 Sn Pb-14 Sb-6 Sn Pb-( 14- 16)Sb-(4.5-5.5)Sn Pb-15 Sb-7 Sn Pb-15 Sb-8 Sn Pb-15 Sb-10 Sn Pb-( 14- 16)Sb-(9.3- 10.7)Sn Pb-( 14.5- 17.5)Sb-(0.81.2)Sn Pb-17 Sb-8 Sn Pb-19 Sb-9 Sn Pb-24 Sb-12 Sn Pb-( 1S-2.5)Sn Pb-3 Sn-5.1 Sb Pb-4 Sn-3 Sb

Electrot ype-General 4% Antimonial Lead 6% Antimonial Lead 8% Antimonial Lead 9 9 Antimonial Lead Lead-base Bearing Alloy Linotype Alloy Linotype-Special Alloy Linotype B (Eutectic) Alloy Stereotype-General Alloy Stereotype-Flat Alloy Lead-base White Metal Bearing Alloy Monotype-Ordinary Alloy Stereotype-Curved Alloy Rules Monotype Alloy Lead-base White Metal Bearing Alloy Lead-base Bearing Alloy Display Monotype Alloy Lanston Standard Case Type Monotype Alloy Monotype Case Type Alloy 2% Tin Solder Solder Alloy Electrotype Curved Plate Alloy 5% Tin Antimonial Solder

L52830 L5290 1 L53105 L53230 L53305 L53346 L53420 L53425 L53455 L535 10 L53530 L53565

11.02 10.88 10.74 10.60 10.50

am'21 3.1 1% 2.88% 2.76% 2%

c

z

v)

0,

r (D (u

P (u

2%

3

a =i v)

9.96

2

270

b U u)

LS3570 L53575 L53580 L53585

9.70

2.3%

L53620

10.10

2.5%

1 1 .OO

3.6%

L53650 L53685 L53750 L542 10 L54280 L543 10 L.54320

(0

VI

Table 20

Continued

Alloy composition" Pb-5 Sn-4 Sb-0.5 As Pb-8 Sn-0.3 Sb Pb- 10 Sn-(0.2-0.5)Sb Pb-(9- I 1)Sn-( 1.7-2.4)Ag<0.2 Sb Pb-10 Sn-4 Sb-0.5 As Pb-12 Sn-0.45 Sb Pb- 15 Sn-(0.2-0.5)Sb Pb-15 Sn-2.5 Sb Pb-20 Sn-(0.2-0.5)Sb Pb-20 Sn-(0.8-1.2)Sb Pb-22 Sn- I .2 Sb Pb-25 Sn-(0.2-0.5)Sb Pb-25 Sn-( 1.1 - 1S)Sb Pb-28 Sn-1.5 Sb Pb-30 Sn-~0.25 Sb Pb-30 Sn-( 1.4- 1.8)sb Pb-3 1.5 Sn- 1.8 Sb Pb-35 Sn-<0.25 Sb Pb-40 Sn-c0.12 Sb

Common name

UNS No.

Solder Alloy 8% Tin Solder 10/90 Solder 88-10-2 Solder

L54360 L54410 L.54520 L54525

Solder Alloy Solder Alloy 15/85 Solder Solder Alloy Solder Alloy 20B Solder Alloy 20C Solder Alloy Solder Alloy 25B Solder Alloy 25C Solder Alloy 30170 Solder Solder Alloy Solder Alloy 35/65 Solder 40160 Solder

L54530 L54540 L54560 L54570 L547 1 1 L547 12 L547 13 L5472 1 L.54722 L54805 L54820 L54822 L54832 L54850 L549 15 L.549 18

Density, (g/cm')

10.50

10.20

9.66 9.60

9.28 7.10

Volume change on freezingh

P-45 Sn-
45/55 Solder Solder Alloy

Pb-50 Pb-50 Pb-50 Pb-50 Pb-60 Pb-60 Pb-60 Pb-60 Pb-62 Pb-63 Pb-63 Pb-65

Sn-<0.12 Sb Sn-2.8 Sb Sn-3 Ag Sn- 1.1 Cu Sn-<0.12 Sb Sn-0.2 Cu Sn- 1.3 Cu Sn-3.5 Ag Sn-2 Ag Sn-(0.2-0.5)Sb Sn-1.4 Ag Sn-<0.6 Sb

50/50 Solder Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder Solder Alloy Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder Solder Alloy Solder Alloy

Pb-70 Sn-(0.2-0.5)Sb

Tin-Lead Solder

Pb(<0.2)-96 Sn-(3.64.4)Ag-(0.2-0.5)Sb

Tin-Silver Solder

L54950 L54955 L550 15 L55030 L5.5035 L55038 L.55040 L551 10 L55113 LS5114 L55116 L55 133 L5.5141 L55 145 L55 150 L55 157 L55161 L55 176 L55 195

"Only main alloying elements are given here. For detailed composition information. see Table 6 . hNegative values show expansion.

8.89 8.70

2.3%

8.50

2.4%

2

b

8.42

7.75 8.32 7.33

U v)

(D

Table 21

03

Thermal Properties of Lead Alloys [28]. (Courtesy of Lead Industries Association, New York.) -~

Alloy composition" Pure lead Pb >99.94 Pb-Ag alloys Pb-( 1.3- 1.7)Ag Pb-1.5 Ag-5 Sn

Common name

UNS No.

Coefficient of Specific Liquidus Solidus expansion heat ("C) ("C) ( X I W 6 / K ) (Jkg/K)

Corroding Lead

L5000 1L50042

327.4

327.4

Solder Alloy-Grade Ag 1.5 Solder Alloy-Grade

L50 132

3 10

309

L50134

30 1

296

L50 150

304

304

L50151

303

-

L50152 L50 170 L50171 L50172 L50180

304 364 292 310 366

299 305

Arsenical Lead Cable L503 10 Sheathing Alloy

327

302

L50605

88

70

29.3

129

Latent heat of fusion Wkg)

23

Thermal conductivity (w/m K) 35

5s

Pb-2.5 Ag-2 Sn Pb-5 Ag Pb-5 Ag-5 Sn Pb-5 Ag-5 In Pb-(5-6) Ag Pb-As alloys Pb-0.15 AS-0. 1 Sn-0.1 Bi Pb-Bi alloys Pb-42 Bi-1 1 Sn-9 Cd

Solder Alloy-Grade Ag 2.5 Solder Alloy-Grade Ag 2.5 Solder Alloy Solder Alloy Solder Alloy Solder Alloy Solder Alloy-Grade Ag 5.5

Fusible Alloy

-

290 304

25

27

24

168

23

21

Pb-42.9 Bi-5.1 Cd-7.9 Sn-4 Hg-18.3 In Pb-44.7 Bi-5.3 Cd-8.3 Sn-19.1 In Pb-48 Bi-14.5 Sn-9 Sb Pb-49 Bi-21 In-I2 Sn Pb-50 Bi-10 Cd-13.3 Sn Pb-51.7 Bi-8.1 Cd Pb-52.5 Bi-15.5 Sn Pb-55.5 Bi Pb-Ca alloys Pb-0.065 Ca-0.7 Sn Pb-0.065 Ca-1.3 Sn Pb-0.07 Ca Pb-0.1 Ca-0.3 Sn Pb-0.1 Ca-0.5 Sn Pb-0.1 Ca-1 Sn Pb-Cd-alloys Pb-17 Cd Pb-Cu alloys Pb-(0.04-0.08)Cu

Pb-In alloys Pb-4.76 In-2.38 Ag Pb-5 In Pb-5 In-2.5 Ag

Fusible Alloy

L506 10

43

38

Fusible Alloy

L50620

47

47

Fusible Alloy

L50630

227

103

Fusible Alloy Fusible Alloy

L50640 L50650

58 70

58 70

Fusible Alloy Fusible Alloy Fusible Alloy

L50660 L50665 L50680

92 96 124

92 96 124

Battery Battery Battery Battery Battery Battery

L50740 L50750 L50760 L50775 L50780 L50790

338 336 332

327 323 328 328 327 325

Lead-Cadmium Alloy-Eutectic

L50940

248

248

Copperized Lead

L51110L51123, L51125

325.6

325.6

29.3

Lead-Indium-Silver Solder Alloy Lead-Indium Solder Alloy Lead-Indium-Silver Solder Alloy

L51510

300

300

25

25

L51511

314

292

29

21

L51512

305

285

25

25

Grid Grid Grid Grid Grid Grid

Alloy Alloy Alloy Alloy Alloy Alloy

9

147 22

0 '0

14

?!

3

189

126

v)

16

16.8

26.6 30.2

22.9-26.2

35

(0 (0

Table 21

Continued

Alloy composition" Pb- 19 In Pb-20 In Pb-25 In Pb-40 In Pb-40 In-40 Sn Pb-50 In Pb-60 In Pb-70 In Pb-80 In-5 Ag Pb-Sb alloys Pb-I Sb

A

0 0

Common name Lead-Indium Lead-Indium Lead-Indium Lead-Indium Lead-Indium Lead-Indium Lead-Indium Lead-Indium Lead-Indium

Alloy Alloy Alloy Alloy Alloy Alloy Alloy Alloy Alloy

I % Antimonial Lead

UNS No.

Coefficient of Specific Liquidus Solidus expansion heat ("C) ("C) ( X IO-'/K) (J/kg/K)

Latent heat of fusion (kJ/kg)

Thermal conductivity (W/m K) 17

L51530 L51532 L51535 L5 1540 L5 1545 L5 1550 L51560 L5 1570 L5 1585

280 270 264 225 130 209 185 174 149

270 180 250 195 121 180 174 160 -

26 26

18 19

27 28 10

29 38 43

L52605

322

312

28.8

131

33

(solid) Pb-1.2 Sb-0.8 Ga Pb-2 Sb Pb-2.5 Sb-2.5 Sn Pb-3 Sb-3 Sn Pb-4 Sb Pb-6 Sb

Lead-AntimonyGallium Alloy 2% Antimonial Lead ElectrotypeGeneral ElectrotypeGeneral 4% Antimonial Lead 6% Antimonial Lead

L52618

315

L52705 L52730

317 303

300 246

L52830

298

246

L52901

299

252

L53105

185

-

252

27.8 27.2

133 (solid) 135 (solid)

31

3

D)

29

2 ?!

h3

Pb-8 Sb

8% Antimonial Lead

L53230

27 1

252

27.2

Pb-9 Sb

9% Antimonial Lead

L53305

265

252

26.4

Pb-(9.5-10.S)Sb-(5.56.5)Sn Pb-11 Sb-3 Sn Pb-l 1 Sb-5 Sn

Lead-base Bearing Alloy Linotype Alloy Linotype-Special Alloy Linotype B (Eutectic) Alloy Stereotype-General Alloy Stereotype-Flat Alloy Lead-base White Metal Bearing Alloy Monotype-Ordinary Alloy Stereotype-Curved Alloy Rules Monotype Alloy Lead-base White Metal Bearing Alloy Lead-base Bearing Alloy

L53346

256

240

L53420 L53425

247 246

239 239

L53455

239

239

L535 10

252

239

L53530

256

239

L53565

272

240

Pb-12 Sb-4 Sn Pb- 13 Sb-6.5 Sn Pb-14 Sb-6 Sn Pb-( 14-1 6)Sb-(4.55.5)Sn Pb-15 Sb-7 Sn Pb-15 Sb-8 Sn Pb-i5 Sb-10 Sn Pb-( 14-16)Sb-(9.310.7)Sn Pb-( 14.5- 17.5)Sb(0.8- 1.2)Sn

24

135 (solid) 137 (solid) 150 (solid)

150

29 27 0.9

0.1

(solid) L53570

262

239

L53575

263

239

L.53580

270

239

19.4

L53585

268

240

19.6

L53620

353

247

160 (solid)

24

A

Table 21

E.-

Continued

Alloy composition" Pb-17 Sb-8 Sn Pb-19 Sb-9 Sn

Pb-24 Sb- 12 Sn Pb-Sn alloys Pb-( 1S-2.S)Sn Pb-3 Sn-5.1 Sb Pb-4 Sn-3 Sb Pb-(4.5-5.5)Sn-(0.20.5)Sb Pb-5 Sn-4 Sb-0.5 As Pb-8 Sn-0.3 Sb Pb-10 Sn-(0.2-0.5)Sb Pb-(9- I l)Sn-( 1.72.4)Ag-<0.2 Sb Pb-10 Sn-4 Sb-0.5 As Pb-12 Sn-0.45 Sb Pb-15 Sn-(0.2-0.5) Sb Pb-15 Sn-2.5 Sb Pb-20 Sn-(0.2-0.5) Sb

Common name

UNS No.

Coefficient of Specific Liquidus Solidus expansion heat ("C) ("C) ( X lO-'/K) (J/kg/K)

L536.50 Display Monotype Alloy L53685 Lanston Standard Case Type Monotype Alloy Monotype Case Type L53750 Alloy

27 1

239

286

239

330

239

L542 10 L54280 L543 10

325 284 294

320 245 245

2% Tin Solder Solder Alloy Electrotype Curved Plate Alloy 5% Tin Antimonial Solder Solder Alloy 8% Tin Solder 10/90 Solder 88- 10-2 Solder

L54321

312

270

L54360 L54410 L54520 L54525

284 305 299 299

240 280 268 268

Solder Alloy Solder Alloy 15/85 Solder Solder Alloy Solder Allo; 20B

L54530 L54540 L54560 L54570 L547 1 1

276 295 288 272 276

222 250 227 204 183

Latent heat of fusion (kJ/kg)

Thermal conductivity (W/m K)

28.7

36

27.9

35.8

26.5

Pb-20 Sn-(0.8-1.2) Pb-22 Sn-1.2 Sb Pb-25 Sn-(0.2-0.5) Pb-25 Sn-( 1.1-1.5) Pb-28 Sn-1.5 Sb Pb-30 Sn-<0.25 Sb Pb-30 Sn-( 1.4-1.8) Pb-3 1.5 Sn-1.8 Sb Pb-35 Sn-<0.25 S b Pb-40 Sn-<0.12 Sb

Sb Solder Alloy 20C Solder Alloy Sb Solder Alloy 25B Sb Solder Alloy 25C Solder Alloy 30170 Solder Sb Solder Alloy Solder Alloy 35/65 Solder 40160 Solder

Pb-45 Sn-<0.12 Sb Pb-45 Sn-2.5 Sb

45/55 Solder Solder Alloy

Pb-50 Pb-50 Pb-50 Pb-50 Pb-60 Pb-60 Pb-60 Pb-60 Pb-62 Pb-63 Pb-63 Pb-65

50150 Solder Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder Solder Alloy Solder Alloy Solder Alloy Solder Alloy Tin-Lead Solder Solder Alloy Solder Alloy

Sn-
Pb-70 Sn-(0.2-0.5) Sb Tin-Lead Solder Pb(<0.2)-96 Sn-(3.64.4) Ag-(0.2-0.5)Sb

Tin-Silver Solder

L54712 L547 13 L5472 1 L54722 L54805 L54820 L54822 L54832 L54850 L549 15 L54948 L54950 L54955 L55015 L55030 L55035 L55038 L55040 L55110 L55113 L55114 L.55116 L55 133 L.55141 L55 I45 L55 150 L55 157 L55161 L55 176 L55195

275 265 266 263 250 255 248 243 244 234 23 1 224 215 I45 216 204 210 280-340 189 190 280-340 180 178 183 178 185 296 192 306 215

185 184 183 184 185 183 185 185 183 183 185 183 185 145 183 185 178 183 183 183 183 178 178 183 178 183 181 183 184 183

25.6

40

24.7

23.5

210

24

150

24.7

0.4

37

46.5

50

50

21.6

-L

"Only main alloying elements are given here. For detailed composition information. see Table 6.

0

0

104

Chapter 2

interdiffusion coefficients. Dispersionsalsotendtoinfluencediffusional creepthrough their influence on the ability of grain boundariesto act as sinks and sources of vacancies. Minimization of diffusional creep could be accomplished by alloying that reduces diffusional coefficientsand by increasing grain size. The mechanisms may superimpose in complicated ways. The contribution of each deformation mechanism can be described by a rate equation which relates strain rate to the stress, the temperature, the structure of the material at that instant and material properties. The stress and temperature range of dominance of each of the mechanisms of plasticity and the rates offlow theyproducecan be summarizedusingdeformationmechanism maps developed by Frost and Ashby [ 1 171. These maps allow the determination of the operative deformation mechanism and the creep strain rate as (T/T,) afunction of normalized stress (u/k) andnormalizedtemperature (where is the shearmodulusand T , the meltingtemperature).The stress term used here is the effective shear stress that is responsible for plastic flow. The map is divided into fields which show the regions of stress and temperature over which each of the deformation mechanisms is dominant. Superimposed on the fields are contours of constant strain rate: These show the net strain rate (due to an appropriate superposition of all the mechanisms) that agivencombination of stressandtemperature will produce.Pband other fcc metals have almost identical maps when plotted using normalized stress and temperature. In general, metals having similar atomic bonding and crystal structure have similar mechanical properties expressed in normalized form, and they are said to belong to a specific isomechanical group. Deformationmechanismmaps for pure lead witha grain size of I O km is shown in Figure 25 [ 1171. The diagram shows three principal fields: low-temperature plasticity, power-lawcreep,and diffusional flow regions. At a large grain size of about 1 mm, the diffusional creepregion is suppressed and the Harper-Dorn creep region is observed. The fcc metals have an extremely low lattice resistance (less than lo-' p); as a result, their yield strength is generally determined by the density of discrete obstacles or defects they contain. When pure, it is the density and arrangement of dislocations that determines the flow stress, which, therefore, dependson the state of work hardening of the metal. In the low-temperature plasticity region, most of the maps describe work-hardened material, with a dislocation density of 6.25 X IO'"/m'. Annealing lowers the yield strength to about a/k = IO" for typical commercial-purityfcc metals. The activation energyfor forest cutting is takenas AF = 0.5 pb' leading to a flow strength which depends only weaklyon temperature. Power-law creep sets in at about 0.37". Diffusion that controls the creep in both power-law and diffusional creep regions is slower in the fcc structure than in the more open body-centered

Properties of Lead andIts Alloys

105

Temoerature ("C\

I

I

Plasticitv

02

at,

.

I

yd'

(Boundary Diffusion)\ 0.6

Homologous temperature

0.8

1.0

T/T~

Figure 25 Deformationmechanismmaps for pureleadwith a IO-pm grain size [ 117). (Courtesy of Prof. H.J. Frost, Dartmouth College, NH.)

cubic (bcc) structure, and among the fcc metals, lead has much lower diffusional rates at the same homologous temperature. Thus, creep rates in lead is less than other fcc metals at the same homologous temperature and normalized stress levels. The power-law-creep field is subdivided into a region of low-temperature, core-diffusion-controlled creep in which the stress exponent is about n+2, and a region of high-temperature, lattice-diffusioncontrolled creep in which the stress exponent is 17. In the high-temperaturecreep region, a value of 17 = 5 and A = 2.5 X 10' [ 1251 is used in estimating creep rates in these plots. The diffusion activation energy of 109 kJ/mol [ 1261is used. Higher 17 values and lower activation energy values are observed at low temperatures [ 127,1281. An apparent activation energy of 92 kJ/mol with IZ 2 7 (compared with 109 kJ/mol and 5 at high temperature) [l281 is used in the low-temperature-creep regime of Figure 25. The dislocation core-diffusion coefficient used corresponds to the boundary-diffusion data of Okkerse [ 1291, which gives an activation energy for core diffusion, Q
106

Chapter 2

Homologous temperature TTI, Figure 26 Pure lead of grain size 1 mm. Harper-Dorn creep has displaceddiffusional flow [ l 171. (Courtesy of Prof. H.J. Frost, Dartmouth College, NH.)

rate and one in which lattice diffusion is controlling. As mentioned earlier, diffusion in lead at a given TIT, is exceptionally slow. When the grain size is large, this field may be replaced by one of Harper-Dorn, as is shown in Figure 26. In the case of antimonial lead, even at a l-mm grain size, diffusional creep is dominant and the Harper-Dorn creep field is absent (Figures 27 and 28) [ l 171.

B.

Deformation, Recovery, Recrystallization, and Grain Growth in Lead and Lead Alloys

1.

Deformation of Single-Crystal and Polycrystalline Lead and Lead Alloys

Deformation of face-centered-cubicmetal like lead occurs by the slipon ( 11 I ] planes in the (1 10) direction. The shear stress necessary to move the dislocation and initiate the slipprocess is referred to as critical resolved shear stress (CRSS). CRSS depends on the temperature and the concentrationof impurities or solute elements. In high-purity lead with less than 2

107

Properties of Lead andIts Alloys

II

I

I

I

0.2

0.4

0.6

d='mrn

1

*

\

0.8

1.0

Homologous temperature T / T ~ Figure 27 A mapforantimonial leadwitha grainsize of 1 mm,showing the conditions of operation of the pipes. Both deform by diffusional flow [ 1171. (Courtesy of Prof. H.J. Frost, Dartmouth College, NH.)

ppm of impurities, CRSS is about 0.5 MPa at 4.2 K and 0.3 MPa at 77 K [ 1301. Figure 29 shows the variation of CRSS at 4.2 and 77 K as a function of Sn in lead. In lead with purity levels of 99.99% or less, higher values of CRSS are reported. Forexample,avalue of 1 ? 0.08 MPa at 77 K and 0.5-0.7 MPd at 293 K have been reported [ 13 l]. There are 12 equivalent { 1 1 I } (1 10) slip systems in fcc metals. Depending on the orientation of the single crystal of the metal, the externally applied shear stress can result in the resolved shear-stress level on one or more { 1 1 1 ]( 110) slip systems to exceed the CRSS level. In a simple case in which the single crystal is initially oriented for slip in only one of the slip systems, the slip is initiated when the critical resolved shear stress is exceeded. This stage where dislocation movement is confined to a single set of crystal planes and their movement is generally unimpeded by dislocations on other crystal planes is referred to as the easy-glide region. If the crystal is free of dislocations, the dislocations are nucleated from the surface region or at a dislocation source within the crystal and move generally unimpeded

108

Chapter 2

Figure 28 Antimonial lead with a grain size of 50 pm. If the pipes had this grain size, they would deform much more slowly than they do [ I 171. (Courtesy of H.J. Frost, Dartmouth College, NH.)

by other dislocations. However, annealed metals, in general, contain dislocation densities of around 106/cm2distributed on various slip systems. Thus, even in the easy-glide region, some interaction of moving dislocations in the active slip system with a stationary forest of dislocations in other slip systems does take place. Dislocation density does increase during this stage and some work hardening occurs. The stress increases slightly with increasing strain in this easy-glide region. As slip occurs, the crystal is rotated with respect to the applied load direction so as to move the slip direction toward the loading direction if the stress was tensile or away from it and if it was compressive. This changesthe resolved shear stress on different slip systems and a second slip system will be activated. As dislocations on this slip move, they interact withdislocations in the primaryslipsystem,leading to an increase in the stress level for dislocation movement on either slip system. Rapid strain hardening takes place in this second stage. The rate of strain hardening is typically about one-thirtieth of the shear modulus. The dislocation density increases rapidly from 10X/cm2 to 10''/cm2 during this stage.

Propertiesof Lead andIts Alloys

109

Figure29 CRSS versus solute content [2,130]. (Courtesy of Springer Verlag. New York.)

With further deformation (stage Ill), dynamic recovery due to either crossslip or dislocation climb leads to a decrease in the work-hardening rate and the stress level reaches a plateau. Fleischer had determined strain hardening in single crystals of pure lead and polycrystalline lead at 77 K (Figure 30) [ 1301. Figure 30 alsoshows the influence of Sn andCuaddition on the hardening of lead. Interactions of the elastic fields of the dislocations and solute elements leads to an increase in the shear stress required for dislocation movement and this strengthening by the solute elements is referred to as solid-solution strengthening.Dislocationsalso interact with precipitates and inclusions. The strengthening due to precipitates and inclusions is higher, the finer their size and the larger their number density. As seen in Figure 6, addition of Cu and Sn hasincreased flow stress levels compared to pure lead single crystal. The results for polycrystalline lead are also compared in this figure with single crystalsof lead oriented initially for single slip. In polycrystalline alloys, the need for compatibledeformation of adjacentgrain requires at least five different slip systems to be active in a grain. Thus, the easy-glide region is absent in flow stress-strain curves corresponding to polycrystalline samples. The deformation of a single grain can take place only by the initiation of flow adjacent to the grain boundaries. The dislocations moving on a slip system are stopped at the grain boundary until a compatible slip is

110

Chapter 2

Figure 30 Stress-strain curves for deformation of lead and lead alloy single crystals [2,130]. (Courtesy of Springer Verlag, New York.)

initiated in the adjacent grain. Dislocations tend to pile up at the grain boundary and this dislocation pileup imposes a back stress on the dislocation source. More stress is required to nucleate dislocations and move them toward the already piled-up dislocations. As the number of dislocations piled up increase, the stress at the head of the pileup increases until such time that the slip systems in the adjacent grain are activated. With decreasing grain size, the applied stress required to cause yielding increases. Yield stress for polycrystalline material is the sum of the stress required for flow in individual dislocation-free and pure crystals, and stress increases needed to overcome dislocation interactions with solute, precipitate, other dislocations, grain boundary, and other defects. As the room temperature corresponds to a high homologous temperature of around 0.5 K, diffusional rates at room temperature are very significant. This leads to marked changes in microstructure. Such changes could involve recovery, recrystallization, and grain growth, and age hardening followed by age softening. Thus, even at room temperature, mechanical prop-

Properties andof Lead

Its Alloys

111

erties could change significantly with storage. Thus, it is important to understand the deformation,recovery, recrystallization, andgraingrowth in lead alloys and how they are influencedby solute elements, temperature, and prior strain.

2.

Recovery, Recrystallization, andGrain Growth

As described earlier, on deforming lead and lead alloys, dislocation densities increase and the material strain hardens. Alloying, complex deformation processes, lower temperature, and smaller grains tend to increase the dislocation density. On heating the deformed material, the energy stored in the material in the form of strain energy associated with dislocations, vacancies, grain boundaries, and other defects is released by the annihilation of these defects through three sequential thermally activated processes, namely recovery, recrystallization, and grain growth. The recovery process at low temperature involves point-defect migration to sinks such as dislocations and grain boundaries. At intermediate temperatures, recovery involves dislocation motion without climb. Rearrangement of dislocationswithin tangles, annihilation by combinationwith dislocations of opposite sign, and subgrain growth can occur, leading to a reduction of defect density. At high temperatures, it involves subgrain coalescence and polygonization that involve dislocation climb. During recovery, resistivity decreases, the cell size of dislocation tangles increases, and the density increases. No drastic change in hardness is observed.Fora firstorder defect-removal kinetics (meaning the rate of removal of defects varies linearly with defect concentration), the variation of property P with time t at temperature T is given by [ 1321 In(P

-

F‘,,)

-

constant = - A

(31

exp -

f

where A is a constant and Q is the activation energy characteristic of the process. The activation energy is found to be approximately the same as the activation energy for self-diffusion. The recrystallization process that follows the recoveryprocess involves, as the name suggests, the formation of new grains, but without the high dislocation densities caused bythe deformation process. The volume fraction of recrystallized grains, X , , is given by [ 1331 X , = 1 - exp(-kr”)

(7)

where k is a function of growth rate and nucleation rate, t is the annealing

112

Chapter 2

time, and n is a constant. The nucleation rate increases with stored energy and, therefore, depends on the amount of strain, grain size, and impurities. A critical amount of strain is required for the recrystallization to occur. The growth rate depends on the stored energy and the grain-boundary mobility. on grain-boundary The impurities and temperature have a strong influence mobility. Recrystallization temperature is definedasthetemperature at which recrystallization occurs within a specified time, usually 1 h. Completion of recrystallization is usually when the volume fraction of recrystallized grain region is 99% (or a lower fraction that is explicitly specified). High strains, small prior grain size, impurities, and lower deformation temperature decrease recrystallized grain size. Once the recrystallization is complete, the growth of larger grains occur at the expense of smaller grains. This process, known as grain growth, occurs in order that the system energy can be lowered by the reduction of grain-boundary area. The grain boundaries of the larger grains are concave outward toward the smaller adjoining grain. The driving force for the grainboundary migration is the force resulting from the grain-boundary curvature and decreases with the increase in the radius of curvature accompanying grain growth. The presenceof dispersions and precipitates opposes the grain-boundary migration and a limiting grain size is reached when D = 2r.K where I' is the radius of the dispersion and f' is the volume fraction of dispersion [ 1331. A typical energy-release rate as a function of temperature as the deformed metal is heated at a constant rate is shown i n Figure 31. The first, smaller, peak corresponds to the recoveryprocess and the second, large, peak corresponds to the recrystallization process. Grain growth follows recrystallization and no peaks are expected for this process. In commercial lead, the recovery stage was measured to be between - 130 and - 100°C with an activation energy of 46.5 kJ/mol and recrystallization was observed between -40 and - 10°C with an activation energy of 96.5 kJ/mol [ 1341. In pure lead, the stages are not clearly separated. Using interrupted creep tests, Kennedy [ 1351 obtained an activation energy value for grain growth as 129.8 kJ/mol and the activation energy for recovery as 82.9 kJ/mol, which are high compared to other data. [ 1361 have carried out recrystallization meaBollingandWinegard surements on zone-refined lead. In their work. the specimens were deformed by drophammerandannealed at varioustemperatures.Grainsizeswere measured optically. They obtained a value of r7 = 0.4 for the expression D = Kt", which relates grain diameter with time of annealing. Here, K = K,, exp( -Q/RT), where K,, is a constant and Q is the activation energy for grainboundarymigration.The activation energy, Q, measured in these experiments was 28 -C 3 kJ/mol. Aust and Rutter [ 1371 also report a similar value of 25 kJ/mol. The grain-boundary velocities in Pb-Sn alloys were observed

Propertiesof Lead andIts Alloys

I

1 Recryst. Recovery f

- _

113

.I

I

Temperature

Figure 31 Energy-release rate and physical properties versus temperature [2,132]. (Courtesy of John Wiley, New York.)

to vary with concentrationas C 5''. By increasing the tin content from 0.0004% to 0.006%, the velocity decreased by 1/1000. The activation energy increased from 62.8 kJ/mol at 0.0001% Sn to 43 kcal/mol at 0.001% Sn. In the case of special orientation relationships, the impurity segregation to grain boundary was minimal and the activationenergywas not affected by the solute content (in the range of0.0005-0.02%) and was measured to be about 25 kJ/mol.Solutes with lowersolubilitylimits tend to drasticallyreduce grain-boundary mobilities. At all temperaturesabove-40°C. the rate of strainhardeningdecreased with temperature [l381 due to the softening caused by the recrystallization process. Although strain hardening occurred even at SO'C, it disappeared after S- I O min. At room temperature, softening required about 25-64 h. At -20"C, it was incomplete, even after 96 h. The rate of tests and interruptions considerably affect tensile strength after deformation because of the occurrence of recrystallization. I n 99.99% purity lead, softening occurs more readily at room temperature (e.g., in 25 min after 25% compression). As alreadymentioned,recrystallization is sensitive to the purity of lead, the amount of prior deformation, and deformation temperature [ 139). Loofs-Rassow [ 1401 determined the temperature-deformationcombinationsabove which recrystallization was observed in lead, using lead that is not of high purity (Figure 32). Very high-purity electrolytic lead given a 2.5% deformation recrystallized at 35°C

114

L'

-

Chapter 2

I

,

l

70 j 0 30 90 50 60 70 80

07 !i

Deformation (%)

Figure 32 Temperature-deformation combination [2,140]. (Courtesy of Springer Verlag, New York.)

limits for recrystallization

in 5- 10 min and at 12°C within 45- 120 min after rolling [59]. Recrystallization was complete in 5 min after rolling at a rolling reduction of 5%. An Sb content of 0.05% delayed the recrystallization to 21 days. As in other metals,adecrease of grain size lowers the recrystallization temperature. Jenckel and Hammes [l411 observed that in alloys rolled to 61%, a 0.1% addition of elements that formed intermetallic compounds, namely Pt, Pd, the recrystalliSe, Au, Ba, Li, K, Na, Mg, Ca, and Te, markedly increased zation temperature. The effect was stronger the higher the melting point of the intermediate phase or compound. The effect was not increased further by contents above the solubility limit. Additions of Zn, Hg, T1, Sn, Sb, and Bi at the level used in their experiments did not have a significant effect. BollingandWinegard [l421 showed that the activation energy for grainboundary migration in zone-melted lead increased from 28 to 40.1 kJ/mol by a Ag content of 0.005 (Figure 33). Rutter and Aust [l431 show that the activation energy increases from 25 kJ/mol for purest lead to 138 kJ/mol for Au and Ag contents of -1 ppm. The addition of Sb at high levels, >2% Sb, inhibited recrystallization. Fora50%reduction at roomtemperature, the worked structure was visible after 2 h, recrystallization began after a day, and complete recrystallization was observed after 12 days. A very high-purity (99.9999%) lead recrystallizes at -59°C [144]. The addition of Ag and Te and, to a smaller extent, Sn slowsthe recrystallization process. The addition of Bi has no effect. With Ca addition, the alloy age hardens after working at -73°C. In alloysdeformed in the age-hardened condition, a pronounced delay in recrystallization occurs. Dynamic recrystallization that takes place during rolling leads to softening and the softening is more pronounced with the increase of deformation (Figure 34). Pb-Sb

115

Properties of Lead andIts Alloys

.4

I

I

I

I

350

321

3%

250

I 200

I 175.

1

Temperature (“C)

Figure 33 Grain growth rate versus l/T for Pb, Pb-0.005 Ag, and Pb-0.005 12,1421. (Courtesy of Springer Verlag, New York.)

Reduction in thickness (%)

Figure 34

Hardnessversus rollingreduction (Courtesy of Springer Verlag, New York.)

in age-hardened Pb-Ca alloys 121.

116

Chapter 2

and Pb-Ca alloys given a 99.9% reduction are stable with regard to recrystallization on storage for days and months, respectively. The behavior of Pb-Te, Pb-Li, and Pb-Na are similar but not as pronounced [84,145,146]. If supersaturation was avoided by slow cooling to room temperature, recrystallization sets in immediately upon rolling the alloy. In supersaturated alloys, precipitate formation could lead to a reduction in strength. The data on grain growth and the limiting grain size at different annealing temperatures and for different deformation strains could be presented in the form of recrystallization diagrams. Such diagrams have been prepared for purest lead, technical lead with Cu, Fe, Sb, As, Zn, and Ag (1471, electrolytic lead, Parkes lead, and Pattinson lead [ 1401. Figure 35 shows that for Pattinson lead (containing about 0.06% Cu), no grain growth occurred until an annealing temperature of 200°C and that the differences between three types of lead disappear at 310°C. The grain-refining action of Cu additions of 0.04-0.05% i n refined lead and Bi-containing lead is also well demonstrated [6X]. Limiting grain sizes in lead and lead alloys after 50% and 60% deformation and after annealing at 160-200°C has been examined by a number of investigators [57,140,141,148]. Cast grains are generally coarse for moderate alloying additions. In rolled and room-temperature recrystallized alloys of Pb-Ca and Pb-Li, grain sizes are below 0.1-0.2 mm, and in Pb-Au alloys, the grain sizes exceed 0.2 mni. On heat treatment at 160-200"C, greater differences are observed. A grain diameter much larger than 1 mm is obtained in purest lead, and in many technical leads, it could be around 1 mm. Bi, few multiples of 0.1% Sb, small amounts of Sn, TI, and Cd affected the grain size only slightly. At high concentrations of these elements, some grain refinement occurs.

Figure 35 Recrystallization diagrams for Pb: (a) Electrolytic lead, (b) Parkes lead, and (c) Pattinson lead [2,1401. (Courtesy of Springer Verlag, New York.)

117

Propertiesof Lead and Its Alloys

V

Figure 36 Grain diameter versus tensile strain after recrystallization [2,149]. (Courtesy of Springer Verlag, New York.)

When inclusions or precipitates are present, the average grain size is limited by the size and number density of inclusions. With elements that have limited solubility, the limiting grain size is well below 1 mm. With a few hundredths of 1% of Cu, Ca, Te, and Ni, strong grain refinement is observed (Figure 36) [l49]. Sb and Sn also have a grain-refining effect at larger concentrations.

C. Short-Term MechanicalTest Data on Lead and Lead Alloys

1 . Tensile Tests Because of creep, a permanent plastic deformation occurs in lead and lead alloys at stress levels well below the yield point at room temperature. Thus, the measured yield points of lead and lead alloys depends on the duration of the test or strain rate. Therefore, the interpretation and use of these yieldpoint data needs some caution. Faust and Tammann [lSO] determined the compressive yield strength by determining the stress level at which surface steps were formed on an initially well-polished surface by slip on crystal

Chapter 2

118

planes. The yield point thus determinedwas2.45MPa -+ 8%.Chalmers [38] determined the limit of proportionality in lead usingan interference method at 0.882 MPa and this value is similar in magnitude to the creep strength of pure lead. The tensile strengths of lead and lead alloys fall with a decreasing rate of strain, and with longer durationtests, the tensile strength approaches the creep strengthkreep limit. Tensile strengths of lead and PbSb and Pb-Sn alloys as a function of strain rate are shown in Figure 37 [151]. The tensile strength as a function of T is given in Figure 38 for Pb and Pb-Sb alloys [ 1521. The variation of tensile strength of lead with grain size is shown in Figure 39 [29]. The data for tensile strength and elongation at room temperature and 265°C is given in Table 22. Data from various investigations on elongation at failure is unsatisfactory, because of variations in specimengeometryand variations in grain size, strain rates, and impurities. Data on commercial lead show values from 2 1% to 73%, with corresponding tensile strengths from 1 l to 21.8 MPa. In commercial lead, the reduction of area is taken as 100%. The necking occurs to a point even at - 1OO"C, indicating the high workability of lead [ 1531. No marked dependence on temperature is observed in the elongation and reduction in area in the temperature range - 100°C to 150°C. However, lead alloys show a marked drop below 0°C. In general, an increase in concentration of solutes increases the strength and decreases the elongation 1291. Figure 40 [ 153al shows a relationship between breaking strain (elongation) and UTS for refined Pb and Pb-Te and Pb-Sb-As alloys. The Pb-Sb-As alloy with high elongation at fracture was extruded at 240°C and quenched immediately in water, and the alloy withlowerelongation at fracturewas homogenized at 250°C(leadingto grain coarsening)andquenched.The

I

0

l

P

I

I

I

8 72 1 Rate of extension (x0.1 I min.)

I

zu

Figure 37 Tensile strengths of lead and Pb-Sb andPb-Sn alloys as a function strain rate [2,151]. (Courtesy of Springer Verlag, New York.)

Of

Properties of Lead and Its Alloys

I

- 1w

l -50

119

l

I

-20

0

Temperature ("C)

Figure 38 Tensile strength of Pb and Pb-Sb alloys as a function of temperature [2,152]. (Courtesy of Springer Verlag, New York.)

Figure 39 The variation of tensile strength of lead with grain tesy of Springer Verlag, New York.)

size [2,29]. (Cour-

Chapter 2

120

Table 22 Variation of Tensile Strength and Elongation of Lead with Temperature 1021 ~

Temperature (“C) Tensile strength (MPa) Elongation (6) (%)

20 13.2 31

82 7.8 24

1 so

4.9 33

19.5 3.9

20

265 2 20

breaking strain in Figure 40 includes both the uniform elongation (that which occurs before necking) and the elongation that arises from the necking.

2. Hardness Tests The hardness of lead on Moh’s scale is about 1.5 [23,154]. However, the Brinell hardness and Rockwell “ R ” hardness scales are more widely used for lead. Hardness is an excellent probe of the strength of a material. The yield strength of a rigid-plastic materials is expected to be one-third the hardness value. Such a relationship is observed in the case of lead, where the plot of hardness of a number of uncorrelated lead alloys were plotted versus their UTS, and the H,{ was found to be three times the UTS 121. In Brinell tests, it is recommended that a 10-mm ball be used and the diameter of the impression to the diameter of the ball be kept between 0.2 and 0.7 by choosing the loads depending on the hardness expected. Loads of 15.6, 31.2, 62.5, 125, and 250 kg are used. Loads to be used in different hardness ranges are given in Table 23.

Figure 40 A relationship between breaking swain (elongation) and UTS for retined Pb and Pb-Te and Pb-Sb-As alloy [2.153a]. (Courtesy of Springer Verlag, New York.)

Properties Its andof Lead

Alloys

121

Table 23 Recommended Loads for DifferentBrinell Hardness Ranges [2] Test Load (kg) Hardness range (H,,), kg/mm'

62.5 1.5-19.5

31.2

15.6 0.38-4.9

0.75-9.75

125

250

3-39

5.6-78.8

The hardness values in lead and lead alloys are sensitive to the duration all tests is recommended and a 30-S of loading. A standarddurationfor duration is commonly used. The hardness values are accompanied by information on the ball diameter (mm), load or load/diameter squared (kg or kg/ mm2), and time. The dependence of hardness on theduration of testing depends on the operative creep mechanism, the nature of the alloy, and the grain size. In general, there is a greater dependence for fine-grained material than coarse-grained material (Figure 41) [ 1551. The Brinell hardness (H10/100/30) of high-purity (Cominco) lead of 99.9999% is 27 2 0.4 MPa at 20°C for a grain size of 0.2 mm'. The grain sizes are given here in terms of cross-sectional area of the grains [ 1561. For a 99.99% purity lead, the Brinell hardness is determined to be 35 2 0.5 MPa at 20°C for a grain size of 0.5 mm'. The hardness of commercial lead is typically in the range 2.5-3H,, at room temperature and is corrected by

1

o fine groin, extruded

22 0

zoo

af 80 C

400

I

2 600

Time (sec.)

Figure 41 Dependence of hardnessonduration Springer Verlag, New York.)

of testing [2,155]. (Courtesy of

Chapter 2

122

0.5% for everydegreechange [84]. Thehardness of polycrystalline lead falls by 0.027 for every 1°C rise from 0 to 60°C [ 1571. H . has been measured from -253°C to 125°C [lS8,159]. At -183"C, the H,, value was 2.1 times the value at 20°C. With a decrease in duration of testing, H" increases, and at a duration of < l ms, a maximum value of 78 MPa is obtained. A similar value is obtained in liquid air independent of the duration of test [ 1601. Thedynamichardness of lead,annealed at 270"C,overarangeof temperatures for different metals was determined by Sauerwald and Knehans [ 1611. These hardness tests may be used for a comparative evaluation of materials. A linear decrease with temperature was observed with the dynamic hardness value decreasing from 7.44 X 10' m kg/m3 at 25°C to 4.24 X 10' m kg/m' at 267°C [ 1621. 3.

Compression Tests in Static and Dynamic Conditions

Deformation of 20-mm-diameterand17.7-mm-high lead pieces by static compression and by dynamic blow has been examined by Heyn and Bauer [ 1631. Compressive stress or the average specific work of impactversus percentage compression in these tests is shown in Figure 42. Specific work of impact/blow amounted to 37.4 cm kg/cm3. The influence of the amount of alloying element on specific work of impact was examined using 16-mmdiameter X 16-mm-high specimens at room temperature [ 1641. Comparison at 50% reduction is shown in Figure 43. It can be seen that Ag and Te have large strengthening effects. Bailey and Singer [ 1651 developed a constant-

l

Figure 42 Compressive stress or theaverage specific work of impact for lead versus percentage of compression [2,163]. (Courtesy of Springer Verlag, New York.)

123

Properties of Lead andIts Alloys

Figure 43 Resistance to impactversuspercentage (Courtesy of Springer Verlag, New York.)

of alloyingelement

[2,164].

strain-rate plane strain plastometer which can apply very high compression rates (0.4-31 l S" strain rates) and, thus, simulate practical working processes.Between 22°C and300°C,theyobserved that stress-strain data obeyed the relationship U = (T,,E"'. The strain-rate sensitivity, m, varied from 0.04 (E = 0.1 at 22°C) to 0.26 (E = 0.5 at 300°C). Notched-bar impact tests oncoarse-and fine-grained specimens, 15 X 15 X 180 mm3 andnotched to a depth of as much as 10 mm, resulted in brittle fracture [29] which is in contrast with ductile fracture generally observed in lead. Coarse-grained specimens had a lower value. The impact resistances of commercial lead at >3.7, and >4.4 m kglcm', respec20"C, - 183"C, and -253°C were >2.3, tively [ 1661. Ductile fracture was observed in these tests at all temperatures of this test. Tables 24-29 present the yield strength, ultimate strength, elongation, shear strength, hardness, impact, fatigue or endurance strength, and creep strength data for different lead and lead alloys [ 167-1761.

Ill. CREEP BEHAVIOR Creep refers to the time-dependent progressive deformation (flow) of a metallic or nonmetallic material under load. It gains significance as the tem-

A

g

Table 24

Mechanical Properties of Lead Alloys 1281. (Courtesy of Lead Industries Association, New York.) Ultimate tensile strength

Nominal alloy composition

Common name

(MPa)

Pure lead Pb >99.94

Corroding Lead

12-13

Pb-Ag alloys Pb-( 1.3- I .7)Ag

Pb- 1 .5 Ag-5 Sn

Pb-5 Ag-5 In Pb-(S-6) Ag Pb-As alloys Pb-0. I5 As-0. I Sn-0.1 Bi

Pb-Bi alloys Pb--42 Bi-l I Sn-9 Cd Pb-44.7 Bi-5.3 Cd-8.3 Sn 19.1

Solder AlloyGrade Ag 1.5

Solder AlloyGrade 5s

Solder Alloy Solder AlloyGrade Ag 5.5 Arsenical Lead Cable Sheathing Alloy

Elongation

30

Yield strength (MPa)

Shear strength (MPa)

Hardness Brinell/ Rockwell R

Impact energy

53

12.5

3 2-4.5

14.1 Charpy V

35 1.8 @ 100°C 30

28

19 @

25

100°C 40 32

16-30

Fusible Alloy

38

Fusible Alloy

37

13

(J)

Creep strength

19.5 MPa (1000 h) 7.5 MPa (1000 h )

Fatigue strength

UNS No.

3.2 MPa@ 10’ cycles

50042

50132

50134

20

50172 SO I80

28

0. I3Wyr @ 2.1 MPd

50310

25-40

5-10

220

9

50605

12

50620

Pb-48 Bi-14.5 Sn-9 Sb Pb-49 Bi-21 In-I2 Sn Pb-50 Bi-I0 Cd-13.3 Sn Pb-55.5 Bi Pb-Ca alloys Pb-0.065 Ca0.5 Sn Pb-0.065 Ca0.7 Sn Pb-0.065 Ca1.3 Sn Pb-0.07 Ca Pb-0.07 12-0.7 Sn Pb-0.1 Ca Pb-0. I Ca-0.3 Sn Pb-0. I Ca-0.5 Sn Pb-0.1 Ca-1 Sn Pb-1 Ca Pb-Cu alloys Pb-(0.01-0.08) 4

N

ul

cu

Fusible Alloy

90

I

50630

Fusible Alloy

43

50

50640

Fusible Alloy

41

140-200

50650

Fusible alloy

44

61

50680

Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Battery Grid Alloy Lead-Calcium Alloy

45 48 62

15 15 10

55

50737 50738 50740

70

10

66

36-39

35-40

45

25

50765

38

30-45

50770

4 1-45

20-35

90-95"

50775

44.8-5 1.7 48.3 52-55

25-35 20-30 20-35

85-90"

50780 50785 50790

Lead-Copper Alloy

38

30-45

16-19

30-60

21 MPa (500 h) 28 MPa (500 h)

50750

70-80"

50760

90-95'

50840

6-8

4-6

11-16 Charpy V

3% per year @ 2.07 MPa

4.3 MPa for 10' cycles

51 I10 5 I 120 51 121

4

g

Table24 Continued

Nominal alloy composition Pb-(0.04-0.08) C~-(0.0350.055) Te

Ultimate tensile strength Common name Grade D per QQ-C-40

(MPa) 21

Elongation (o/.)

40

Yield strength (MPa)

Shear strength (MPa)

Hardness Brinell/ Rockwell R

1-5

Impact energy (J)

Creep strength

Fatigue strength

UNS NO.

6.9 MPa for 10’ cycles

51 123 5 I 124 51125 51 126 51127

Same as 5111051 121

above

Ph In alloys Pb-4.76 In2.38 Ag Pb-5 In-2.5 Ag

Ph-25 In Pb-40 In

Pb-60 In Pb-70 In Pb-Sb alloys Pb-0.2 Sb-0.4 Sn

Lead-lndiumSilver Solder Alloy Lead-IndiumSilver Solder Alloy Lead-Indium Alloy Lead-Indium AlIoy Lead-Indium Alloy Lead-Indium Alloy Cable Sheathing Alloy

32

51510

31.4

$1512

37.6

5 I535

34.5

5 I540

28.6

51560

23.8

51570

6.3 MPa @ 10’ cycles

52520

Pb-0.5 Sb-0.25 Cd Pb-0.85 Sb<0.06 Cu

5.3 MPa (1200 h)

Cable Sheathing Alloy Cable Sheathing Alloy. Alloy

B Pb-l Sb

1 % Antimonial

20

50

7

Lead Pb-3 Sb-3 Sn Pb-4 Sb

ElectrotypeGeneral 4% Antimonial Lead

27.6

48

13

47

24

Pb-8 Sb

8% Antimonial Lead

32. I

31.3

9.5

Pb-9 Sb

9% Antimonial Lead

52

17

15.4

Lead-base Bearing Alloy Linotype Alloy LinotypeSpecial Alloy

69

5

19

19 22

52570

52830

8.1

6 6 Antimonial Lead

52540

52605

2.4 MPa (lo-‘/ year)

12.4

Pb-6 Sb

Pb-Sb-Sn alloys Pb-(9.5-10.5) Sb-(S.5-6.5) Sn Pb- I 1 Sb-3 Sn Pb-1 I Sb-5 Sn

11.5 MPa @ lo7 cycles 9.6 MPa @ 10’ cycles

2.8 MPa (lo-5/ year) 2.93 MPa (lo-$/ year)

10.3 MPa for 10’ cycles 17.2 MPa for 2 X 10’ cycles 12.1 MPa for 2 X 10’ cycles 19 MPa for 2 x 10’ cycles

52901

26 MPa for 2 x 10’ cycles

53346

53105

53230

53305

53420 53425

A

N 0)

Table24

Continued

Nominal alloy composition Pb-12 Sb-4 Sn

Pb-13 Sb-6.5 Sn Pb- I4 Sb-6 Sn Pb-( 14- 16) Sbb(4.5-5 5 ) Sn Pb- I5 Sb-7 Sn

Pb-15 Sb-8 Sn Pb-15 Sb-I0 Sn Pb-( 14- 16) Sb-(9.310.7) Sn

Common name Linotype B (Eutectic) Alloy StereotypeGeneral Alloy Stereotype-Flat Alloy Lead-base White Metal Bearing Alloy MonotypeOrdinary Alloy StereotypeCurved Alloy Rules Monotype Alloy Lead-base Whitemetal Bearing Alloy

Ultimate tensile strength (MPa)

69

72

Elongation (”/.)

5

4

Yield strength (MPa)

Shear strength (MPa)

Hardness Brinell/ Rockwell R”

Impact energy (J)

Creep strength

Fatigue strength

UNS No.

22

53455

22

53510

23

53530

20

27 MPa for 2 x 10’ cycles

53565

24

53570

25

53575

26

53580

22

28 MPa for 2 x 10’ cycles

53585

Pb-( 14.5-17.5) Sb-(0.8-1.2) Sn Pb-17 Sb-8 Sn

Pb-19 Sb-9 Sn

Pb-24 Sb-12 Sn Pb-Sn alloys Pb-0.2 Sn0.075 Cd

Pb--0.4 Sn-0.15 Cd Pb-( 1.5-2.5) Sn

Pb-4 Sn-3 Sb

Pb-(4.5-5.5) Sn-(0.2-0.5) Sb

Lead-base Bearing Alloy

71

30 MPa for 2 x 10’ cycles

20

7

I

Display Monotype Alloy Lanston Standard Case TYPe Monotype Alloy Monotype Case Type Alloy

27

53650

28.5

53685

33

53750

Alloy 1/2CCable Sheathing Alloy Alloy C-Cable Sheathing Alloy 2% Tin Solder Electrotype Curved Plate Alloy 5% Tin Antimonial Solder

55

10

8

5.0 MPa for 1200 h

4.2 MPa for 10’ cycles

54030

5.0 MPa for 1200 h

5.4 MPa for 10’ cycles

54050

4.7 MPa for 10’ cycles

54210 54310

12.5

28

53620

9.5 lzod

54321

Table 24 Continued

Nominal alloy composition

Pb-10 Sn(0.2-0.5) Sb

Common name

10/90 Solder

Ultimate tensile strength (MPa)

Elongation

6)

30

10

8@ 100°C

30

Yield strength (MPa)

Shear strength (MPa)

Hardness Brinell/ Rockwell R"

Impact energy (J)

10

10.8 h o d

32.5

11.3

Pb-20 Sn(0.2-0.5) Sb Pb-30 Sn<0.25 Sb

Solder Alloy 20B 30/70 Solder

40

16

34

18

28

12

16.5 Charpy V 16.3 Izod

Pb-40 Sn<0.12 Sb

40/60 Solder

37 6@ 100°C

25 130

32

12

19 Izod

Pb-40 Sn(1 2-2.4) Sb

Solder Alloy

23

78

7@ I0o"C

100

25

Creep strength

3.5 MPa for loo0 h 1.1 MPa for loo0 h

Fatigue strength

UNS No.

54520

5471 1 0.79 MPa for 0.01% per day

54820

54915 2.1 MPa for loo0 h 4.9 MPa for 1000 h 0.6 MPa for loo0 h

54918

Pb-50 Sn<0.12 Sb Pb-60 Sn(0.2-0.5) Sb

Pb-60 Sn-0.2

60

50/50Solder

41

Tin-Lead Solder

52.5

30-60

19 @ I00"C

100-135

Solder Alloy

33

36

I4

16

43

cu

Pb-63 Sn-

(0.2-0.5)Sb

Tin-Lead Solder

19 @ 100°C

7

51.7

32

14

55030

2 1.6 Izod

20 Izod

2.9 MPa for loo0 h 0.45 MPa for loo0 h 16 MPa for loo0 h 2.7 MPa for 1000 h 2.3 MPa for 3 X

55111

55133

55141

1o-'is

54 Pb-70 Sn(0.2-0.5) Sb "Rockwell R values.

Tin-Lead Solder

46.9

1.5

23 12-17 24-27

55157 55161 55176

-L

0

Table 25 Mechanical Properties of Commonly Used Lead Alloys

h)

Lead or lead alloy" (ConG. in wt.%) Pure lead [c] Pb 99.985 Pb 99.95 DSL Corroding [el Refined [r] Chemical [c] Chemical [r] Undesilverized [el Undesilverized [r] 0.47 Ag + 0.18 Ca [el 0.47 Ag + 0.18 Ca [a] 0.15 As + 0.1 Sn + 0.1 Bi 0.77 Ba + 0.30 Ca [el 0.77 Ba + 0.30 Ca [a] 0.88 Ba + 0.94 Ca [el 0.88 Ba + 0.94 Ca [a] 0.1 Bi 0.2 Bi 0.025 Ca

Tensile strength (MPa)

13.1

Elongation (%o)

Hardnessh

'4.0

45

18.4 18.2 41.4

33 35 18.5

12.1 17.9 19.3 17.2 16.5 41.1 43.8

53 45 47 50 51 40 38

@28S @28.5 '13.5

Compression strength (25%) (MW

15.2

Yield strength (MPa)

5.9

44.8

3.1 40.0

'3.8 '5.2 Y.5

20.0

11.3

'4.7

17.9

Fatigue strength (MPa)

Creep strength (0.2%/year) (MPa)

modulus (10 GPa)

2.7'

2.0-2.2 3.2

1.2

2.0

15.8

2.5

6.9 8.6

5 .O 10.0'

51.2 58.5 61.1 55.5 21.6 20.6 25.1

Young's

38 32 44 40 45 33 17.7

0.050 Ca

37.2

29.0

0.065 Ca

42.5

31.8

1 hr at 20.7 MPa 30 h at 20.7 MPa 50 h at 20.7 MPa

Ref.

167, 168 169 169 170 167 167 167 167 167 167 171 171 168 171 171 171 171 169 169 172 172 172

0.075 Ca

46.4

35.3

0.090 Ca

47.0

32.9

0.100 Ca

47.5

32.5

0.1 10 Ca

46.3

30.5

0.120 Ca

43.2

27.6

0.140 Ca

39.2

24.7

+ 0.5 Sn 0.025 Ca + 1.0 Sn 0.025 Ca + 1.5 Sn 0.025 Ca + 2.5 Sn 0.050 Ca + 0.5 Sn 0.050 Ca + 1.0 Sn 0.050 Ca + 1.5 Sn 0.050 Ca + 2.5 Sn -, 0 0.025 Ca

0

40.0

30

31.1

57.9

20

47.5

58.6

20

50.2

51.7

20

41.8

55.2

30

45.3

61.4

25

52.8

63.8

15

51.4

68.9

15

61.3

40 h at 20.7 MPa 20 h at 20.7 MPa 100 h at 13.8 MPa 10 h at 20.7 MPa 40 h at 13.8 MPa 7 h at 20.7 MPa 5 h at 20.7 MPa 2 h at 20.7 MPa 10 h at 27.6 MPa 20 h at 27.6 MPa 30 h at 27.6 MPa 10 h at 27.6 MPa 10 h at 27.6 MPa 150 h at 27.6 MPa 300 h at 27.6 MPa 400 h at 27.6 MPa

172 172

172

172 172 172 173 173 173 173 173 173 173 173

A

g

Table25 Continued Tensile strength (MPa)

Lead or lead alloy” (ConG. in wt.%)

0.065 Ca

+ 0.5 Sn

(%I

+ 1.5 Sn 0.070 Ca + 0.5 Sn 0.070 Ca + 1.0 Sn 0.070 Ca + 1.5 Sn 0.070 Ca + 2.0 Sn

49.4

58.6

+

Hardnessh

Yield strength (MPa)

40.0

48.2

0.065 Ca

0.070 Ca + 2.0 Sn 0.050 Ag 0.075 Ca + 0.5 Sn

Elongation

Compression strength (25%) (MPa)

62.1

30

45.0

68.9

15

64.0

71.0

L4

65.3

74.4

12

68.9

80.0

10

76.8

50.3

40.2 49.2

0.075 Ca

$.

1.5 Sn

60.1

0.080 Ca

+ 0.5 Sn

41.4

35

29.6

0.080 Ca

+

58.7

25

52.8

1.0 Sn

Fatigue strength (MPa)

Creep strength (0.2%/year) (MPa) 200 h at

20.7 MPa 750 h at 20.7 MPa 20 h at 21.6 MPa 400 h at 27.6 MPa 1,000 h at 27.6 MPa 8,000 h at 20.7 MPa >20,000 h at 13.8 MPa .20,000 h at 27.6 MPa 300 h at 20.7 MPa 1,000 h at 20.7 MPa 2,000 h at 13.8 MPa 8 h at 27.6 MPa 250 h at 27.6 MPa

Young’s modulus (10 GPa)

Ref.

I72 172 173 173 173 173

173 172

172

173 173

0.080 Ca

+

1.5 Sn

71.8

20

66.0

0.080 Ca

+ 2.0 Sn

73.7

20

69.3

0.090 Ca

+ 0.5 Sn

51.3

40

+ 1.5 Sn 0.100 Ca + 0.5 Sn 0.100 Ca + 1.5 Sn

58.6

46.9

51.7

38.7

57.9

43.7

+ 0.5 Sn 0.120 Ca + 1.5 Sn 0.140 Ca + 0.5 Sn 0.140 Ca + 1.5 Sn

45.8

31.1

57.2

41.7

46.5

31.2

56.5

39.5

0.33 Ca + 0.32 Ba [el 0.33 Ca + 0.32 Ba [a] 0.08 Ca + 0.2 Ag + 0.5 Sn 1.77 Cd + 0.45 Ba [el 1.77 Cd + 0.45 Ba [a] 0.06 Cu

53.6 62.3 62.7

37 32

61.2 34.8 20.9

37 57 41

0.04 Cu + 0.03 Te 0.63 Li [4] 0.63 Li [o]

26.4

34 52

24.1

55

0.090 Ca

0.120 Ca

~

600 h at 27.6 MPa 850 h at 27.6 MPa 100 h at 20.7 MPa 600 h at 20.7 MPa 70 h at 20.7 MPa 250 h at 20.7 MPa 280 h at 13.8 MPa 20 h at 20.7 MPa 140 h at 20.7 MPa 15 h at 20.7 MPa 120 h at 20.7 MPa >17,600 h at 13.8 MPa

@40.2

6.9

@60.8

8.8

5.2

173 173 172 172 172 172

172 172 172 172 171 171 172 171 171 169, 174 169 175 175

d

0 Q,

Table25 Continued

Lead or lead alloy" (ConG. in wt.%) 0.64 Li [o] 0.65 Li [ l ] 0.65 Li [2J 0.66 Li [7] 0.66 Li [o] 0.67 Li [3] 0.67 Li [I] 0.67 Li 121 0.68 Li [el 0.68 Li [a] 0.68 Li [S] 0.68 Li [2] 0.70 Li [2] 0.71 Li [6] 0.71 Li [2] 0.72 Li [2] 1.15 Na [el 1.15 Na [a] 0.9 PbO [eo] 1.4 PbO [eo] 1.9 PbO [eo] 3.7 PbO [eo] 0.9 PbO [el] 1.9 PbO [el] 2.2 PbO [el] 3.9 PbO [ell

Tensile strength

Elongation

(MPd

(%)

20.8 37.8 52.8

56 39 22 26.6 55 1.8 22 16 99 67

24.5 43.5 44.8 37.8 38.4

10

47.4 47.3 54.4 49.9 54.5 53.6 29.8 32.8 35.4 40.5 25.6 28.3 30.1 34.3

14 11

30.3 29 23 36 36

Hardnessh

Compression strength (25%) (MPa)

Yield strength (MPa)

Fatigue strength (MPa)

Creep strength (0.2%/year) (MPa)

Young's modulus (10 GPa)

Ref. 175 175 175 175 175 175 175 175 171 171 175 175 175 175 175 175 171 171 168 168 168 168 168 168 168 168

0.9 PbO [e2] 2.1 PbO [e2] 2.6 PbO [e2] 5.3 PbO [e2] 0.9 PbO [ero] 1.4 PbO [ero] 1.9 PbO [ero] 3.7 PbO [ero] 0.9 PbO [erl] 1.9 PbO [erl] 2.2 PbO [erl] 3.9 PbO [erl] 0.9 PbO [er2] 2.1 PbO [er2] 2.6 PbO [er2] 5.3 PbO [er2] 0.13 Sb + 0.04 Cu 0.2 Sb + 0.015 As 0.2 Sb + 0.4 Sn

19.9 21.0 21.9 26.3 29.4 31.9 35.3 40.9 28.9 33.6 30.6 37.1 26.3 27.2 29.4 34.6 21.2

0.23 Sb + 0.03 Cu 0.4 Sn 0.4 Sb + 0.03 As

23.7

0.40 Sb + 0.05 Cu + 0.04 Te 0.45 Sb 0.5 Sb 0.5 Sb + 0.15 As 0.5 Sb + 0.25 Cd 0.5 Sb + 0.04 Cu + 0.25 Cd 0.5 Sb + 0.02 Na

27.1

40

@71.6

23.6 26.5

48 43

@41.2

26.6

43

@63.8

27.5

42

+

~

W

-4

44

@40.2

5.2 8.1' 6.3'

53

@40.2

5.5

9.8'

168, 174 169

7.2'

168 169 169 168 169

7.9

11.4 8.3

168 168 168 168 168 168 168 168 168 168 168 168 168 168 168 168 169 168 168, 174 169

169

-L

w

03

Table25

Continued

Lead or lead alloy" (ConG. in wt.%)

Tensile strength (MPa)

Elongation

(%I

Hardnessb

Compression strength (25%) (MPa)

Yield strength (MPa)

0.5 Sb + 0.05 Te 0.5 Sb + 0.05 Se 0.5 Sb + 0.1 Se 0.58 Sb + 0.06 Cu 0.59 Sb + 0.04 Cu 0.6 Sb 0.78 Sb + 0.03 Cu 0.8 Sb 0.08 Sb + 0.5 Sn 0.08 Sb + 0.5 Sn + 0.06 Cu 0.84 Sb 0.05 Cu 0.9 Sb + 0.06 Cu 1 Sb [c]

26.5 24.5 24.5 24.5 24.1 19.3 24.7 25.2 21.6 22.6

42 48 45 43 44 35 46 44 47 47

25.4

46

37.9

20

19.3

2 Sb [c]

46.9

15

37.9

2.9 Sb + 2.9 Sn [el 2.9 Sb + 2.9 Sn [a] 3 Sb [c]

39.6 27.0 65.5

43 59 10

3 Sb [r] 4 Sb [c] 5 Sb [c] 6 Sb [c] 6 Sb [el

24.6 37.2 42.1 45.5

40 25 23 22 31.0

+

@41.2 @42.2 #10.0 @51.0 @52.0

6.6 5.9

@49.1

7.4

Fatigue strength (MPa)

2.8

Young's modulus (10 GPa)

2.4-3.6

6.8

9.2' 7.6d

49.6 55.2 59.3 167

16.3 18.6 19.3 20.7

14.5 15.9 17.2

3 h at 27.6 MPa 190 h at 27.6 MPa

1.6 1.6 1.7

Ref.

169 169 169 169 169 170 169 169 169 169 169 168 173 173 171 17 1 173

630 h at 27.6 MPa

55.2 "0.0 *10.8 "1 1.6 41

Creep strength (0.2%/year) (MPa)

3.0 3.3 3.5

173 167 167 167

~

6 Sb [r] 10 Sb [c] 11 Sb [c]

29.6 51.0 75.9

42 16 5

11 Sb [r]

23.8

35

0.0225 Sn [el 0.05 Sn + 0.03 As [el 0.055 Sn 0.1 Sn + 0.03 As [el 0.1 Sn + 0.1 Bi + 0.15 As 0.2 Sn + 0.03 As [el 0.2 Sn + 0.07 Cd 0.2 Sn + 0.075 Cd + 0.03 As 0.4 Sn + 0.2 Sb (Alloy E Shealth) 0.5 Sn 0.89 Sn + 0.88 Ba [el 0.89 Sn + 0.88 Ba [a] 0.93 Sn + 0.07 Ca [el 0.93 Sn + 0.07 Ca [a] 0.0975 Sn 1.72 Sn + 0.35 Ba [el 1.72 Sn + 0.35 Ba [a] 1.75 Sn + 0.21 Ca + 0.20 Ba re1 1.75 Sn + 0.21 c a + 0.20 Ba [a]

27.5

*8.7 "13.8

67.6

15.2 22.1 74.4

10.3 18.6

4.0 1,200 h at 27.6 MPa 8,000 h at 20.7 MPa 4.5 h at 20.7 MPa

23.8

167 167 173

173

3.4 6.6 4.4 1.2

174 174 174 174 169

7.6 6.5' 7.7

174 168 174

8.7

40

18.6-20.1

32-49

19.6 71.15 68.33 42.5 56.3

39 31 23 36 46

61.2 30.5 60.0

47 46 46

173, 174 169 171 171 171 171 69 171 171 171

62.3

42

171

3.8

Table 25 Continued

Lead or lead alloy" (ConG. in wt.%) 1.91 Sn + 0.71 Ca [el 1.91 Sn + 0.71 Ca [a] 1.93 Sn + 0.61 Li [el 1.93 Sn + 0.61 Li [a] 2.5 Sn + 0.04 Cu 0.03 Te 0.4 Te [c] 0.05 Te 0.1 Te 2.0 T1 1.06 Zn f 0.66 Li [el 1.06 Zn f 0.66 Li [a]

Tensile strength (MPa) 52.8 60.0 61.6 54.4 27.5 23.6 20.7 25.5 28.5 20.6 35.9 37.6

Elongation (%)

29 29 65 54 50 35 45 34 29 85 57

Hardnessh

Compression strength (25%) (MPa)

@48.1 9.7

Yield strength (MPa)

7.0 22.1

13.8

Fatigue strength (MPa)

Creep strength (0.2%/year) (MP4

Young's modulus (10

GPa)

Ref. 171 171 171 171 169 169 167 169 169 169 171 171

"[a] = annealed, [c] = cast, [el = extruded, [eo] = extruded at room temperature, [el] = extruded at lOO"C, [e2] = extruded at 200°C. [ero] = extruded and rolled at room temperature, [erl] = extruded and rolled at lOO"C, [er2] = extruded and rolled at 200"C, [r] = rolled, [o] = tested at 110°C in oil with stain rate of 0.17 m-', [ I ] = strain rate of 0.05 min-', [2] = strain rate of 0.25 min-', [3] = stress 9.89 MPa (1.0 ksi), [4] = stress 14.84 MPa (1.5 ksi), [ 5 ] = stress 19.79 MPa (2.0 ksi), [6] = stress 24.74 MPa (2.5 ksi), [7] = stress 29.68 MPa (3.0 ksi). b# = Brine11 hardness number and @ = value shown in MPa. 'Fatigue strength BS801.1938: sample cut from rod and tested at lo7 cycles. 'Fatigue strength AEI: sample cut from extruded strip and tested at 2 X lo7cycles with 3000 cycledmin. 'Fatigue strength BICC: sample cut from shealth and tested at 2 X lo7 cycles with 3000 cycles/min.

Properties andof Lead

Its Alloys

141

Table 26 Hardness of Three Dispersion Strengthened Lead Alloys After Annealing at Different Temperatures [ 1751. (Courtesy of Lead Development Association, London.)

Temperature of l-h anneal (“C) 16

Hardness, H , . 1% PbO

12.2

50 12.5

100 150 200

11.9 11.6

9.6 9.6 9.4 9.4 9.2

2% PbO

3% PbO

12.2

13.1 13.0 12.8

11.0

12.1

perature increases, and thermally activated movement of atoms and dislocations become appreciable. As the homologous temperature of lead at room temperature is around 0.5, the creep behavior is of particular importance for 44, appreciablecreep leadandlead alloys. As can be seenfromFigure deformation occurs in Pb and Pb alloys subjected to loading at room temperature [ 1771. The different mechanisms of creep that are operative in lead and lead alloys were discussed earlier. These operative mechanisms are sensitive to stress level, the homologous temperature, and grainsize of the alloy. Besides the interest from the viewpoint of engineering applications of lead alloys, the creep behavior of lead at room temperature is of interest because of its similarity with the deformation behavior of high-melting fcc metallic materials such as Ni-base superalloys in a much higher temperature range [ 117,1781. In this section, a brief discussion of parameters used for the evaluation of creep and the experimental measurement of creep is presented first. This is followed by a presentation of creep and stress rupture data in lead and lead alloys.

A.

Different Stages of Creep

Creep tests are usually carried out under constant load by weights or springs. The increase of stress which occurs due to the reduction of cross section with time can be neglected for small amounts of elongation. Constant stress creep tests require the use of feedback control systems and these may be used at high strain rates. Relaxation tests are of less significance for lead. The general procedures for creep testing are covered in ASTM Specifications E 139.

Table 27 Variation of Mechanical and Technological Properties of Some of the Lead Cable Sheathing Alloys on Storage [176]. (Courtesy of Lead Development Association, London.) Alloy No.

Tensile strength (MPa)

Yield point uoz (MPa)

Elongation (%) Lo = 70 mm

A B C D E A B C D E A B

c D E

1

2

3

4

5

6

7

8

9

10

11

12

13

14.9 14.8 14.2 14.4 14.0 8.3 7.3 6.9 7.2 6.9 38.5 44.5 45.5 43.0 44.0

16.1 15.9 15.8 15.9 15.7 8.7 7.8 7.4 7.9 7.2 43.0 43.0 45.0 45.5 44.0

21.8 21.6 21.8 22.5 21.8 14.7 12.5 10.9 11.6 10.6 33.0 40.0 40.5 41.0 40.0

17.0 17.7 19.0 19.1 19.3 11.7 11.0 12.1 12.5 11.4 36.0 36.5 34.0 32.5 30.0

17.2 18.7 19.4 19.1 19.2 11.4 12.1 11.7 12.6 12.4 39.0 37.0 35.0 36.0 32.0

17.6 17.8 19.2 19.3 19.1 11.8 12.1 12.2 12.2 11.8 37.5 39.0 35.5 35.5 36.0

17.8 19.6 21.8 23.5 23.5 11.9 12.8 13.8 15.2 15.0 31.5 31.5 26.5 24.0 24.0

18.7 18.1 18.8 19.4

18.1 18.2 19.0 21.3 21.9 11.9 11.1 11.8 13.7 14.0 37.5 38.5 35.0 30.0 29.0

27.5 30.8 30.5 28.1 37.5 20.3 22.3 21.5 20.7 19.5 21.5 22.0 24.0 25.5 24.0

17.4 17.3 17.2 17.2 17.0 10.4 9.5 9.1 9.6 8.6 39.5 42.0 41.5 42.0

19.4 19.6 20.0 19.9 20.2 14.1 14.3 14.2 14.8 14.1 28.0 30.0 30.0 29.5 30.0

19.7 20.3 21.0 20.8 21.0 13.9 13.9 14.2 14.1 14.5 29.5 31.5 31.0 32.0 27.5

-

11.5 11.3 10.8 11.2 38.0 39.0 38.0 37.0 -

44.0

Brine11 hardness A 44 (MP4 B 42 H, 0.62515-60 C 41 D 42 E 41 No. of reverse A 38 bends through B 36 180" C 42 r = 7.5 mm D 44 E 50 No. of stress A 96 cycles X 10' B 118 (Fatigue test) C 89 s = 11 MPa D 74 E 74 Creep % after 2000 h s = 4 MPa

44 43 43 41 41 42 44 50 52 48 1 I7 130 103 89 118 1.19

61 58 55 51 49 23 25 26 24 32 875 725 600 520 42 1 1.oo

48 54 58 57 59 36 35 42 36 43 450 800 750 700 650 0.51

48 53 52 57 57 42 35 41 44 43 600 790 730 550 650 0.60

48 53 52 56 56 68 55 71 56 73 36 31 37 30 46 32 36 30 44 31 450 328 680 530 760 625 550 1600 600 1685 0.22 1.50

54 53 56 57 31 34 35 35 3 10 412 395 537

49 48 55 60 61 29 30 31 33 35 350 450 400 400 - 650 1.79 1.92

Note: A: after extrusion; B: after 6 months: C: after 18 months; D: after 36 months; E: after 72 months.

84 98 96 97 91 22 21 23 27 26 2300 4070 3350 4480 5225 0.61

47 45 45 43 44 36 36 35 37 37 180 252 144 215 180 1.16

60 61 60 61 61 37 36 40 37 37 970 1480 1200 1830 1400 0.08

60 64 65 64 66 38 37 40 38 36 1140 1900 1600 2270 2713 0.23

Table 28 Chemical Compositions of Cable Sheathing Alloys Referred to in Table 27 [ 1761. (Courtesy of Lead Development

A

Association, London.)

P P

Alloy No.

Alloy type

Sn

Te

Sb

Cd

As

cu

Bi

Ag

Pb Pb-Cu

-

-

-

2

-

-

0.05

<0.001

3

Pb-Sn-Cu

2.5

-

0.034

<0.001

4

Pb-Te

-

0.057

<0.01

<0.01

<0.001

5

Pb-Te-Bi

-

0.06

6

Pb-Te-Cu

-

0.07

0.05

<0.001

7

Pb-Sb

<0.01

-

<0.01

<0.01

8

Pb-Sb-Cu

-

-

0.05

<0.01

9

Pb-Sn-Sb

0.45

-

<0.01

10

Pb-Sb-Cd-Cu

-

-

0.04

<0.01

<0.001

11

Pb-Sn-Cd

0.19

-

-

<0.01

12

Pb-Sn-As-Cu

0.1

-

0.04

-

13

Pb-Sn-Te-

0.14

<0.001

1

As

0.1

<0.01

“Lead of 99.99% purity (Material No. 1) was used for the preparation of all alloys. hBismuth content of the standard alloy: 0.06-0.089’0.

Traces

0.032

-

Remarks” Purity 99.99% Kb-Pb DIN 17640 (1959) Kb-PbSn 2.5 DIN 17640 (1959) Kb-PbTe 0.04 DIN 17640 (1959) Kb-PbTe 0.04 DIN 17640 (1959) Kb-PbTe 0.04 DIN 17640 (1959) Kb-PbSb 0.5 DIN 17640 (1959) Kb-PbSb 0.5 DIN 17640 (1959) Alloy E B.S.S.801 (1959) Alloy D B.S. 801 (1959) Alloy C B.S. 801 (1959) Gencalloy A (General Cable Corp.) Tellurium Alloyh (General Electric Comp.)

3

4

Tc

%

Iu

Properties andof Lead

Its Alloys

145

Table 29 MechanicalProperties of the Alloy Pb + 1.93% Sn + 0.6 1 % LiAfter Annealing [ 1751. (Courtesy of Lead Development Association, London.)

Mechanical es treatment

Heat

Temp. ("C)

Time Temp. at UTS (min.)

300 230h 227h 215 204 204 150 100 -25

(Melt & cast)"

UTS (psi)

% Elongation

15,070 15,370 14,470 38 13,170 13,740 40 12,200 43 9,020 7,890 65 8,940

45 45 45 45 45 45 60

(As extruded)

(MP4

(in 1 in.)

103.95 106.02 99.8 1 90.84 94.78 84.15 62.22 54.42 61.67

41 44 31 40

54

"Melted and cast in 6 mm Vycor tublng; water-quenched from 300°C. hhcipient melting of specimen.

An idealized creepcurve for the caseconstantloading is shown in Figure 45 [ 1791 to illustrate the different stages of creep. The slope of this curve gives the creep rate. Following the instantaneous strain on the application of the load, one observes a time-dependent flow with three stages. In stage I, called the primary creep, the creep rate decreases with time. The creep resistance of the material in this region increases due to its own deformation. This stage is followed by a secondary creep region, a stage in

l000

S

-

800

L 600 x

.E 400

F

m

200

0

5

20 10

15

35 25

30

40

45

Time (Days) Figure 44 Creep curves of antimonialleadwith (Courtesy of Springer Verlag, New York.)

1.0% Sb and 0.04% As 12,1771,

Chapter 2

146 , Primary creep

Secondory c m 0

Tertiow crew

Time (t)

Figure 45 Idealized creep curve [ 1791. (Reprinted with permission from McGraw Hill Companies, New York.)

which the creep rate is nearly constant (quasi-steady-state region) and is a minimum. The constant creep rate results from the balance of strain hardening and recovery processes. The secondary creep region is followed by a region of increasing strain rate, referred to as tertiary creep, that terminates with the fracture of the sample. The increase in creep rate is due to a reduction in effective cross-sectional area. In the creep tests that take place under constant load, the stress grows perceptibly at high strains as a result of the reduction of area (necking). In addition, there is a true tertiary creep which is characterized by an increase in strain rate at constant stress. This is attributed to the damage associated with the formation of microcracks or voids at the grain boundaries. The intercrystalline cracks exert an internal notch action, leading to the occurrence of fractures at comparatively small of precipitates anddystrains. Metallurgicalchangessuchascoarsening namic recrystallization may occur during this tertiary stage. Andrade fitted the creepcurve to the expression I = ,,,(l + exp(k/), where I and I,, are the final and initial lengths of the sample, respectively, p and k are constants, and t is the time [ 1801. An expression for creep curve in its current form can be derived for small t by [ 18 l ]

= &) = El,

+ In(1 + p/"') + kt + pt"' + kt

(8)

Thus, the total strain is a superposition of primary transient creep that varies

Properties andof Lead

Its Alloys

147

asandsteady-statecreepwithacreep rate of k . It is foundto fit most materials, including lead, copper, cadmium, tin, and lead-tin alloys. In lead single crystals at low temperatures [ 1821, one observes only of transient creep is the transient creep.On the otherhand,anabsence (0.001%) alloys [ 1831. observed in age-hardened lead-antimony-arsenic Here, the instantaneous creep is immediately followed by secondary creep. In the creep curves shown in Figure 44, the transient creep is seen to end after about 7 days and the steady-state creep then takes up a greater part of the creep curves. On the basis of years of experience with lead, at least 80 days are suggested as the duration of practical creep tests [ 1841.

B.

Structural Changes During Creep

Because the temperature and stress are constant, the variation in creep rate during primary creep is a result of changes in the internal structure of the material with creep strain and time. In addition to grain growth and secondphase precipitation that occur during creep, one of the important structural change that can occur is the formation of subgrain structure and grain-boundary sliding. The creep deformation is inhomogeneous and this can cause the lattice bending to occur, especially near grain boundaries [ 1851. This bending results in the formation of excessdislocations of onesign,andbecause dislocation climbcanoccur readily at hightemperature, the dislocations arrange themselves into a low-angle grain boundary, forming subgrains. The formation of a subgrain structure or cell structure during primary creep has been studied by x-rays, metallography, and thin-film electron microscopy. Such studies have shown that the dislocation density of the subgrain network increases during primary creep to a level that remains essentially constant during steady-state creep. The size of the subgrain depends on the stress and the temperature. Large subgrains are produced by high temperature and a low stress or creep rate. The formation of a subgrain structure occurs most readily in metals of high stacking-fault energy. The formation of subgrain structure is observed in lead during creep [ 1861, although the reported stacking fault energy of 25 mJ/m’ for lead is not high. The low stacking-fault energy materials tend to recrystallize rather than form a cell structure during primary creep [ 179,1861. Another process that leads to structural changes during high-temperature creep is grain-boundary sliding. At elevated temperatures, the grains in polycrystalline metals can move relative to each other. This grain-boundary sliding is a shear process that occurs parallel to the grain boundary and is promoted by high temperatures and low strain rates. It occurs discontinuously with time, and the amount of shear displacement is not uniform along the grain boundary. The grain-boundary sliding plays an important role in

Chapter 2

148

the initiation of grain-boundary fracture. Measurements of the grain-boundary sliding in lead in comparison with the general creep have been carried usinga bicrystal withasmall-anglegrainboundary[187].Theboundary was inclined at 45" to the direction of tension. The energy of activation for grain-boundary sliding was determined from this bicrystal work to be between 53.6 and 64.9 kJ/mol,and the energy of activation of the general creep to be between 74.5 and 92.1 kJ/mol. C.

Activation Energy for Steady-State Creep

Steady-state creep predominates at temperatures above about 0.5TM.An assumption that is often made is that creep is a singly activated process which can be expressed by an Arrhenius-type rate equation [ 1791,

6, = A exp

(g)

where Q is the activation energy for the rate-controlling processes, A is the pre-exponential complex constant containing the frequency, vibration of the flow unit, the entropy change, and a factor depending on the structure of the material, T is the absolute temperature, and R is the universal gas constant. If we plot log i: versus 1/T, a series of parallel straight lines, one for each stress level, will be obtained. The slope of these lines is Q/2.3R. A temperature-differential creep test in which the change in creep rate with an abrupt change in temperature is often used to measure the activation energy for creep. If the temperature interval is small so that the creep mechanism would not be expected to change, then

R ln(&,/&) = l/Tz - 1/T, Dorn [l881 found a surprising similarity of energy of activation for creep and for self-diffusion for most metals (Figure 46). This suggested that the process which controls creep rate at high temperatures must be a diffusioncontrolled process [ 188,1891. Butcher and Ruoff [ 1901 carried out measurements of the activation energy for creep in 99.9999% purity Pb. The value 1 .l 8 5 0.03 eV and the value for of the activation energy obtained was cm'. activation volumewasfound to be (24.2 % 0.6) X

Properties of Lead and Its Alloys

149

Figure 46 Comparison of activation energy for creep and for self-diffusion in various metals [2,188]. (Courtesy of Springer Verlag, New York.)

D. Performance and Evaluation of Creep Tests In general, creep measurements are carried out on lead rods under tensile load. The stress is referred to the initial cross section. If a sufficiently long gauge length, such as 200 mm, is used, then the elongation is determined with a cathetometer or a vernier caliper with sufficient accuracy for practical purposes. If a traveling microscope is available, a gauge length of any desired size is used by clamping a stiff measuring bar on the rod and measuring the small distance between the mark on the end of the bar and a mark on the rod (Figure 47). A sufficiently high accuracy of measurement of about is obtained for a shorter-duration of test by using a Martens mirror extensometer in the arrangement shown in Figure 48. Much of the old creep data for lead are based on creep setups similar to that shown in Figures 47 and 48. More sensitive and simpler displacement sensors based on Linear Voltage Differential Transducer (LVDT) and capacitance gauges have become available in recent years. The minimum creep rate or the steady-state creep rate is the important design parameter derived from the creep curves. The steady-state strain rates on a logarithmic scale determined from various creep tests are plotted against stress on a linear or logarithmic scale, and in both cases, approximately

150

Chapter 2

Figure 47 Simple measuringarrangement for creep tests on lead rods 121. (Courtesy of Springer Verlag, New York.)

straight lines are obtained. From the plot, the limiting creep stress (creep strength) relating to a permissible rate of strain can be obtained. The permissible creep rates used in the design of components are typically 1 % strain in 10,000h (2.8 X 10."" S") or 1% strain in 100,000 h (2.8 X 10"' S - ' ) (ASTM E139-70). As a permissible creep rate (for instance, in water pipe applications), the value of (0.1-1) X IO-'%/h could be used for lead [191]. A creep rate of 10-4%/hclosely corresponds to a strain of 1% per year. If only one bar or one testing apparatus is available, the test is begun at the lowest load, and the latter is increased from time to time when a minimum creep rate has occurred. Instead of a creep rate versus stress plot, often a plot of stress versus the time in which the strain reaches a fixed amount (say, 1%) is plotted. In the determination of the limiting creep rate, the instantaneous creep and the

Properties of Lead and Its Alloys

151

To

Figure 48 Measuringarrangement with aMartensmirror extensometer for creep tests [ 2 ] . (Courtesy of Springer Verlag, New York.)

initial strain are neglected. Often, the instantaneous creep and initial strain are included in the limiting strain [184]. Another type of test used to assess creep resistance is the stress-rupture test. In this test, time to cause failure at a given nominalstress and a constant temperature is determined. Elongation and reduction in area (RA) at fracture are also measured. The stress is plotted against rupture time on a log-log scale. The structural changes cause the changes in the slope of the curve. It is similar to creep tests, except that the tests are carried out to failure. The tests usually are of shorter duration, 1000 h or less, and the stress levels are higher than in creep tests. The rupture strength is the stress to produce a time to rupture of a fixed amount, usually 1000, 10,000, or 100,000 h. When creep and stress-rupture data need to be extrapolated to higher temperatures or times, the Sherby-Dom temperature-compensated time parameter (e) approach provides a rational basis on which it could be done, provided no structural changes or changes in mechanism occur [179]. The parameter 8 is given by 0 = t exp

(2)

Taking a natural logarithm on both sides gives

152

Chapter 2

ln0=Int--

Q RT

Q

lnt=ln0+RT The plot of In t versus 1/T for different stresses converged at 1/T = 0 and In t = -C,, showing that 0 is independent of stress:

Q

l n t + C -I - R T

T(ln t

Q = P, + C,) = R

(14)

P , is the Larsen-Miller parameter [ 1921, which varies with stress for a given alloy. C, is often assumed to be 46. P , versus stress curves are established experimentally for different alloysandused in the extrapolation of data. Manyotherparametersalsohavebeenusedtoextrapolatecreepdatato longer times and higher temperatures.

E. Factors That Influence Creep Rate in Lead Alloys 1.

Creep in Pure Lead Single Crystals and the Influence Solute Elements

of

Ley and Hoffman [ 1931 carried out creep tests on 10- 1 l-mm-thick zonerefined crystals with a purity of 99.99%. The strain was measured at 25°C by a Martens mirror apparatus (Figure 48). The creep curves of six different carefully centeredcrystalsshowedaveryspeedyreductionofcreeptoa complete standstill on loads which were above the creep limit of polycrystalline lead. Afterexceeding the creeplimit,creepcurves of normalappearance were obtained so that the initially rapid flow changed into one with a constant strain rate. The resulting critical shear stresses in the octahedral slip system amounted, on an average, to 0.6 MPa. In lead single crystals of 99.999% purity at - 190°C the increase of no steady-state creepwas lengthonloadingceases after 10-20minand observed. The critical shear stress (creep limit) estimated in the octahedral slip system amounted to 0.96 t 0.08 MPa. At 25"C, critical shear stress was found to be 0.69 MPa in the non-heat-treated specimens and 0.33 MPa in those which had been heated to 90- 120°C. This and other observations show that at room temperature, lead can retain some of the strain hardening for

Properties andof Lead

Its Alloys

153

weeks. At 1 IO'C, the creep strength was 0.18 ? 0.04 MPa. At higher stress levels, a single-crystal specimen creeps faster than a polycrystalline one of the same dimensions under the same tensile stress [ 194,1951. At very low stresses levels, the reverse is true as the creep mechanism changes to difCu, Te, Ag, In, fusional creep. The addition of alloying elements such as Bi, and Sn that either go into solution or present as second-phase dispersion in the single-crystal matrix tend to increase the creep resistance. The alloy single crystals with indium, bismuth, or tin contained 1 at.% of these element. Other single crystals contained 0.035 wt.% Te, 0.01 wt.% Ag, or 0.035 wt.% Cu. Figure 49 shows the creep curves for high-purity binary alloys of Ag, Te, and Cu with Pb[190]. In all the alloy singlecrystals, the creep strength was increased as compared with that of unalloyed lead-leastin [ 1961. those containing copper,greatest in those containing silver (Figure 49) The power-law exponent, t?, varies from a value of 4.5 for pure lead single crystals to a value approaching 3 for solid solutions with higher concentrationsofalloyingelements. An exceptiontothistrend is the leadbismuth solid solution, which behaves like pure lead [196-1981.

0

Im

15UO

m

Z5W Time (h)

3000

.%W

4KV

Figure 49 Creep of single crystals of alloyed lead [2,196]. (Courtesy Verlag, New York.)

Springer

Chapter 2

154

Polycrystalline Lead: Influence of Grain Size, Stress, and Temperature on Creep

2.

The influences of grain size on creep rate at different temperatures and stress levels in pure lead (99.99%) are shown in Figures 50-52 [191,199]. In these experiments, the temperature was altered at constant load and the load at constanttemperature.All the curves in Figures 50 and 51, in which the creep rate is plotted against the stress or against the temperature, show a break after passing which the rates of strain rise very steeply. In addition, the curves for coarse- and fine-grained lead intersect so that at low stresses andtemperatures, the creep rate of fine-grained lead is higher. At high stresses and temperatures, the coarse-grained lead creeps faster. This transition occursas the rate-controlling mechanismchangesfrompower-law creep to diffusional creep. The influence of grain size on creep rate in Pb-Cu alloys at a stress level of 2.06 MPa is shown in Figure 53 [200]. The Pb-Cu alloys have a two-phase structure consisting of nearly pure lead and pure Cu. The Pb-Cu alloyswith different grainsizeswereobtained by extrusionof the alloy

20

. E-

Q

W

38 4

155

Properties of Lead andIts Alloys

U

20

40

60

80

100

I20

Temperature ("C)

Figure 51 Effect of grain size on the creep strength of recrystallized lead-copper alloys at a stress of 2.1 MPa [2,191]. (Courtesy of Springer Verlag, New York.)

billets at various temperatures and speeds. The minimum in the creep rate for the lead-copper alloys is observed at a certain grain size. Such a minimum indicates that both diffusional-creep and power-law-creep contributions are significant at this temperature and stress level. The grain size at which the minimumcreep rate is observed shifted to lowervalueswith increasing Cu content. The creep rate decreases with increasing Cu content at a given grain size (Figure 54) [2,200]. The comparison of the creep behavior of wrought and cast alloys of the same composition deserves special interest. The higher creep strength of cast alloys than wrought alloys can, in general, be attributed to the coarser structure of the cast state (Figure 5 5 ) [2,201]. The Pb-Cu alloys extruded at low rates tend to have greater amount of polygonization and lower creep rates 12001.

3.

Influence of Alloying Additives in Solid Solution

Soluteelements that decrease the interdiffusion coefficient in leadalloys decrease the creep rate, as illustrated by the decrease in creep rate with tin additions(Figure 5 6 ) [2,199].Additions of 0.09%cadmium,indium, tin, thallium, and antimony to lead reduced the creep rates at a stress level of 2.06 MPa. Among these elements, cadmium and indium have a larger dif-

156

Chapter 2

Figure 52 Variation of creep rates of commercial lead with I/T [2,199]. (Courtesy of Springer Verlag, New York.)

ference in atomic radius with lead, and their addition leads to a decrease in interdiffusion coefficients. Thus, the lead-cadmium and the lead-indium alloys had a greater effect on creep rate and also show a greater resistance to recrystallization. 4.

influence of Age Hardening

The fine precipitates present in the age-hardened condition tend to increase the creep resistance. Creep curves of alloys with 0.9% Sb and 0.001% As in a solution-treated condition and after age hardening by storage at 20°C and 50°C are shown in Figure 57 [194]. The age hardening in particular resulted in a reduction of the amount of transient creep. A considerable increase of the creep strength is obtained in age-hardened lead-antimonyarsenic alloys and other age-hardened alloys, such as lead-calcium.

Properties of Lead and Its Alloys

157

Average grain cross-section (rnrn2) Figure 53 Effect of grain size on creep rate of lead-copper alloys at a stress of 2.06 MPa [2,200]. (Courtesy of Springer Verlag, New York.)

5.

Influence of Prestrain

The influence of prestrain on the creep behavior of a very pure lead-copper (0.1%) and lead-tin (1%) alloys has been examined by Hopkins and Thwaites [200]. The instantaneous creep after prestraining was very low at first and then gradually increased to a value observed in specimens without

Average grain cross-section (mm2) Figure 54 Effect of grain size on creep rate of recrystallized lead-copper alloys at a stress of 2.06 MPa (2,2001. (Courtesy of Springer Verlag, New York.)

Chapter 2

Time (h) Figure 55 Lead with 64.5% Sn. Creep curves of cast and rolled sheets under tensile stress [2,201]. (Courtesy of Springer Verlag, New York.)

0

0.1

0.

03

0.Y

0.5

Ol

0.7

Oh'

09

10

I1

Sn content (%) Figure 56 Effect of tin content on creep strength of specimens of similar grain size under a stress of 2.06 MPa [2,199]. (Courtesy of Springer Verlag, New York.)

Properties andof Lead

Its Alloys

159

Time (h) Figure 57 Effect of age hardening on creep behavior of leadwith 0.9% Sb and 0.001%As [2,200]. (Courtesy of Springer Verlag, New York.)

prestrain. At the end of the tests, all the rods had the same creep rate, but the total strain was lower, the higher the amount of prestraining. The creep strength is also influenced by a superposed dynamic stress. The increase in creep rate with superposed alternating stress on a static stress is mainly attributed to an increase in specimen temperature as a consequence of damping. The rate of creep in the static test is lower than in the dynamic test with the same upper stress [ 2 ] .

F. Creep Under Multiaxial Stress States Most creep tests are carried out under uniaxial tensile stress. However, in the use of lead as a construction material, multiaxial loading conditions are common. The treatment of creep under multiaxial stress is treated by the use of effective stress and strain rates:

Ueff=

c:

1

- [(Ul -

v5 1

.

v'f

U$

- - [(El - E$

- fi

+

(U*

- U$

+ (U3 - u1)2]"2

+ (E? - E$ +

(E3

-

&$]ID

Chapter 2

160

If ucffand are related by &* = &U*>”, then the stress distribution in multiaxial tension can be calculated. If the stress distribution is known, then the creep rate can be calculated. The equations for creep rates are given by ECff

[202,203]

E,

= B(u*)”’[u,

-

0.5(u2 + U,)]

E2

= B(u*)”’[u,

-

0.5(0,

E3

= B(D*)”’[u,

-

+ U,)] 0 . 5 ( ~+, a2)]

(16)

Thequantities B and n are determinedfrom the steady-state part of the uniaxial creep test. An illustration of the use of the effective stress and effective strain is given in the creep design of lead pipes subjected to an internal pressure p (Figure 58). For the calculation of stresses in aleadpipeunder internal pressure, equations for completely plastic conditionsneedto be used. OdqvistandHult [204] haveevaluated the stress distribution in the pipe under internal pressure. Rieche [205] has derived corresponding equations for the case of simultaneous stressing by internal pressure and tension. From the stress distribution that was calculated, it was shown that increasing the ratio of internal pressure to axial load increases the gradient of the equivalent stress D* over the cross section. In all cases, the maximum value for the equivalent stress was on the inner wall of the pipe. The steady-state creep rates were determined using creep tests on various lead-alloy pipes under combinedstressesdueto internal pressureand tension. If the equivalent stress U* at a point on the pipe wall, calculated for the various stress conditions, is plotted on a log-log scale against the reference elongation rate E* determined at this point in the test, then, in accordance with the equation &* = B(u*)”, the points must lie on a straight line of slope 1 2 . Figure 58 [2] shows that this relationship is followed in the case of Pb-0.05 wt.% Cu. A correlation of a specific stress in the uniaxial tension test with the internal pressure which led to a creep rate of the same magnitude showed is given by that the maximum allowable internal pressure, P,,nllowLlhle

where upis the creep rate limit from the uniaxial creep test, r , , is the outer radius, and I., is the inner radius [196,205]. When lead is used as a pressure-equalizing material, lead should transfer the pressure forces (e.g., the weight of a structure) uniformly onto the

Properties of Lead and Its Alloys

161

Figure 5? Dependence of effective stress on effective straininthe creep of lead pipes in Pb-0.05 Cu pipes under various stress conditions [ 2 ] . (Courtesy of Springer Verlag, New York.)

foundation. It is expected that the lead will How at the points at which the surface pressure would be inconveniently high for the foundation and will accommodate itself in the regions of low pressure. In this way, a uniform the lead surfacepressure is imposed on the entirefoundation.However, should not be pressed out completely from the equalizing joint during the service life of the pad; that is, the creep of the lead should come to a halt after the uniform surface pressure has been set up. However the load-carrying capacity of lead under stresses of this type depends on the effect of the frictional forces between the inserted lead and the contact surfaces. A reference creep test data for pressure-pad applications [206] using lead sheets of various wasobtained by HofmannandMaltki thicknesses and having a size of 40 mm X 60 mm at a constant pressure of

Chapter 2

162

9.8 MPa. It was shown that the creep rate drops drastically with the decrease in thickness as the influence of frictional forces become dominant.

G.

Creep Data for individual Lead Alloys

1.

Stress-RuptureData

The stress-rupture curves of lead alloys obtained by different investigators are shown in Figure 59 [ 184,207-2101. Here, the stress referred to the initial cross section is plotted against the time for failure on a logarithmic scale. of different lead alloys Tables 30-33 present the stressrupturedata [168,17S].

2. Creep Strain Rate Data of Commercial Alloys In this section, stress versus strain rate curves for various commonly used alloys are presented. Some of the creepdatafor different lead alloys is presented in Table 24 in Section 11. Figures 60 and 61 show the stress versus creep strain rate plots for various commercial lead alloys and lead antimony alloys [2,177,184,199,208,210-2 1 S]. The data are from various sources and variations in material compositions and processing conditions, and the sample sizes lead to a large scatter in the data. The results for commercial lead (see Figure 60) fall on a band. Pipes made of lead-antimony alloys containing about 1% antimony in a soft or slightly age-hardened condition show a superior creep resistance compared to commercial lead at higher stresses, but not at lower stresses. In age-hardened lead-antimony, particularly when arsenic is present, creep resistance is superior to commercial lead even at low stresses [85,2 12,216,2171. Figure 61 shows clearly that the two groups of alloys and their creep rates differ almost by an order of magnitude. The superiority of antimonial lead over commercial lead is lost at higher temperatures (Figure 62) [218]. Thelead-arsenicalloysandmulticomponent alloys containing As have significant creep strength (Figure 63) [207]. This behavior is related to the marked difference between atomic radii of lead and arsenic, and to the effect of the precipitates of arsenic in lead. The alloys considered in Figure 63 in part have As contentsfarbeyond the solubility limit at room temperature. Considerable superiority of lead-calcium alloys over commercial lead for all stresses can be seen in Figures 64 and 65 [76,184,207,208,211,219]. The range of values on the right in Figure 64 contains those corresponding to cast alloys of higher calcium content. The values on the left correspond to extruded alloys of lower calcium content. The data in Figure 65 include

Properties of Lead and Its Alloys

163

Time to failure (h) 0

Lend (90.89%) with 0.09?&B!

+ Commercial Lead 25.8"C

i

CommercialLead 21.1'C Cable Sheathing 2 % Sn (According to JIOORE and co-workers 11841 ). C3 Cable Sheathing 0.75% Sb H Cable Sheathing 0.03%0 Cn 0 O.Oi%o Cn Matcrini 1 Material 2 0 0 Cable Sheathing 0.18% As + 0.113% Sn. (According to DOLLINS 12071 ). Refined Lrad (stamped) 0 Refined Lead i0.06%! Te (stamped) (According to GoHs and co-workers (2081). m Chemical Lead 0.059% Cu @ Chemical Lend 0.05% Ca x Lead Pipe 0.018% Ag (According to QOHN and ELLIS 12091). A CommercialLend,CoarseGrained (Accord,ng to MCKELLAR 12101 ). A Comnlercial Lead, Fine Grsincd o

0

}

Figure 59 Creep-to-rupture of lead and lead alloys [2,184,207-2101. (Courtesy of Springer Verlag, New York.)

those for some cable sheathing alloys. The superiority of lead-calcium alloys (Figure 66) is seen even at 65°C [219]. The copper addition does tend to increase the creep strength of lead, but the effect is neutralized by the finer grain of the specimens containing copper (Figure 67) [2,184,200,21 1,222,2231. Creeptests on commercial lead and on lead-copper alloys that have been extruded at two different temperaturesshow that lead-copperextruded at 120°Cis markedlysuperior to

Table 30 Stress-Rupture Lives of Various Lead Alloys at Room Temperature [ 1681. (Courtesy of Lead Development Association, London.)

Material Tadanac lead Tadanac lead Pb-0.06% Cu Pb-O.O15% Te Pb-2% Sn Alloy E (0.4% Sn, 0.2% Sb) Alloy E (0.4% Sn, 0.2% Sb) Pb-0.4% Sb Pb-0.4% Sb-As Pb-1% Sb Alloy B (0.85% Sb) Alloy B (0.85% Sb) Pb-0.03% Ca Alloy F-3 (0.15% As; 0.1% Sn; 0.1% Bi) Alloy F-3 (0.15% As; 0.1% Sn; 0.01% Bi)

Details of extrusion" C P P C C Rh 200°C 200°C Ch Rh

160°C 200°C

Stress-rupture life (h) at a stress of 10.3 MPa

0.75 3.5 -160

>29 to .t93 185 -270 -800 -500 -2,000

8.6 MPa

6.9 MPa

5.2 MPa

0.75- 1.O 2.25 9.5 21 -400 130 -500 c26 1 744 -950 1,200 -800

4-8 24-28 78-100 150-175 -950 390-440 1,440 816 3,360 -3,000 1,700 -1,150

110-1 16 348-700 1,050- 1,126 1,512

-

326 288

-

1,680 -4,000 2,784 15,165

-

- 12,000

- 1,400

4,034 5,714

"C = continuous extrusion pressure; temperature of extrusion approx. 250°C; P = pipe pressure; temperature of extrusion 100-120°C; R = commercial Ram pressure; temperature of extrusion approx. 160°C. h5% prestrain before testing.

3

nl

2 2 h)

Rupture

165

Properties of Lead and ItsAlloys Table 31

Stress-RuptureLives of Lead-0.69% Lithium Alloy in Air at 110°C 11751. (Courtesy of Lead Development Association, London.) Stress (MPa)

0.69 1.38 2.07 2.76 3.45 4.14

0.69

life

Elongation 7.5 cm)

(h)

(% in

9.6 39.0 36.4 28.0 19.3 39.9 9.6

> 12,382 6,354 2,276 1,400 S98 I98 >20,885

~~

Table 32 Stress-Rupture Properties of Dispersion Strengthened Lead Materials at Ambient Temperature [ 1681. (Courtesy of Lead Development Association, London.) Extrusion Oxide Time Stress temp.content Material (% Pb)

("C)

(MPa)

Cast and wrought lead D.S.L.

R.T." R.T. R .T.

200

4.55 2.96 16.55 13.79 10.34 16.55 13.79 10.34 16.55 13.79 10.34 16.55 13.79 10.34 16.55 10.34

R.T.

16.55

200

10.34

0.9 0.9

0.9 2.0 2.0 2.0 3.7 3.7 3.7 D.S.L.

0.2% S b Alloy D.S.L.

0.5% Sb Alloy

Elongation

100 200 R .T. 100

200 R.T. 100

200

1.1 1.1 1.1

R.T.

0.4 0.4 2.1 2.1

R.T.

"R.T. = room temperature. hdenotestest continumg.

100

200

(h)

(% on 1 in.)

91 5,185 1,030 3,404 8,992 3,380 17,000' 17,000h 17,OOOh 1 7,000h 17,000' 4,968 17,000h 17.000' 8

6,400h 6,400h 6,400h

49 50 16 8

6 6

-

42

Chapter 2

166

Table 33 Stress-RuptureProperties of DispersionStrengthenedLeadMaterials Elevated Temperatures [ 1681. (Courtesy of Lead Development Association, London.) Material

at

Oxide content Stress temp. Test (% Pb)

Time

Elongation

("C)

(MPa)

(h)

(% on 1 in.)

2.07 13.79 13.79 10.34 10.34 15.51 27.58 13.79 24.13 13.79 27.58 10.34 24.13

470 75 310 288 344 49 23 278 38 12 14 15 23

35

Lead D.S.L.

-

80

0.9

ss

3.7

S5

0.9

80

3.7

80

1.1

S5

0.2% Sb

4.0

ss

Alloy

1.1

80 80

D.S.L.

4.0 0.4 4.6 0.4 4.6

D.S.L.

0.5% Sb Alloy

55 55 80 80

IO

3 IO

4 3" 2 4

2 21

2 14 2

"Fractured outslde gauge.

Rate of strain ( x m 4 % I h) (According to PHILLIPS 12131 ). coarse-grainedPurelead (99.99O,:). (According to v. HANYFSTENGEL fine-grained and I ~ A N E M A [l991 N N1. + determined 1935 [212j A U-lend (99.99%). (According t.0 GREENWOODand \VOltNEH 12111 ). o coarse-grained (According to ~ c ~ s o w [2101 x ).

rr&

.

}

,

]

A

(According to M O O R E nlnong others [l841) at 30°C. (According to GOIIN and others [208]).

Figure 60 Creep rates of commercial lead [2,184,199,208,210-2 13I. (Courtesy of Springer Verlag, New York.)

167

Properties of Lead and Its Alloys

h 0 5 0.01 0.0f

+

0.75% Sb 0.76% Sb A 1.0% Yh 0

0.05

1

0.1

0.2 0.5 Rate of straln

(Accordingto

MOORE,

7

2

5

l0

50

I h) BETTYand 1)OLLINS[1848.

Antimoniallead A, determined 1935. B 1% Sb + 0.05% As, determined 1057[214] x 0.8% Sh + 0.0296 As 5 1.0% Sh + 0.02% As(According tu Stocktneyer)[215]. [I] 1.2% Sb + 0.02% As A Arsenicalleadfrom nlciind. A. G . B Antlmonlal lead A, tested after 4'/, years storage[l77] 0 1% Bb, artificially aged. (According to PHILLIFS[213]). o 1% Sb at 30°C (According t o GOHN alnong otheru[208]). W

1

Figure 61 Creep rates of antimonial lead [2,177,184,208,213-2 151. (Courtesy of Springer Verlag, New York.)

commercial lead (Figure68).On the otherhand, the effect of the added copper is precisely reversed after extrusion at 180°C. In contrast to leadcopper, commercial lead becomes very coarse grained at this extrusion temperature. Coppercontentonlyincreases the creep strength of lead if the copper is present as a fine dispersion, and in a coarser distribution, it has no effect on the creep strength [220]. The high creep strengths for an alloy of very pure lead with 0.005% silver and 0.005% copper and other leadsilver-copper alloys (Figure 69) [2,208,209,211,223,224] are mainly attributed to the action of silver [221]. Room-temperature creep strength of antimonial is high for antimony contents up to 5.4% [184,225]. However, this superiority weakens with increasing temperature (Figure 70) [226]. For practical purposes, the temperaturedependence of the creep strength of lead and its alloys isof great significance. Three-dimensional creep strength-temperature-stress plots for five grades of commercial lead and four alloys are shown in Figures 7 la-7 li [2,184,2 16,2271. The relatively small effect of temperature is observed in both lead-calcium-copper alloys (Figures 71a and 7 lb). Sohota [228] has examined the work-hardening and creep behavior of pure lead and binary alloys of lead with Cu, Te, and Sb in the temperature

Chapter 2

Figure 62 Creep curves of commercial lead and antimonialleadwith 1.16%Sb and 0.04% As at 85°C [2,218]. (Courtesy of Springer Verlag, New York.)

range 5 6 0 ° C and a stress range of 1- 12.5 MPa. Creep rates at different temperature and stress levels for these alloys are presented in Figures 7275 and Tables 34-37. Power-law exponent and activation energy values for creep are also given in Tables 38 and 39, respectively.

IV.

FATIGUE STRENGTH

Fracture of metalsubjectedto repetitive or fluctuating stress occursata much lower stress compared to the stress required for fracture on a single application of load. Such failures are referred to as fatigue failures and constitute a major fraction of service failures of engineering components. In the case of lead and lead alloys in engineering applications, fatigue is of particular concern in lead cables that are subject to repetitive reverse loading. In cable sheathing made from commercial lead (“soft lead”), cracks were frequently observed and the origin of these cracks were first attributed to fatigue by Haehnel [229]. BeckinsaleandWaterhouse [230] examined over 48 fractured cables installed near railways or bridges, a few underground cables, overhead cables, and cables which had been carried by ship or pro-

Properties andof Lead

Its Alloys

169

As (wt.%)

Figure 63 Creep strain of lead alloys after 5000 h at 43.3"C under various stresses, plotted in relation to theantimony and arseniccontents 12,2071. (Courtesy of Springer Verlag, New York.)

longedrailway transport, and in allcases, the failureswere attributed to fatigue. Although extensive research has been carried out on a number of alloys in different environments, no complete understanding of what causes fatigue exists today. However, extensive engineering data have been accumulatedanddesigncriteriahavebeenestablished that arebasedon the empirical relationship among variables that have been identified to influence cracknucleationandgrowth. These variables includemaximum tensile stress,amplitude of stress fluctuation andfrequencyof stress fluctuation, number of cycles, temperature, metallurgical structure,residual stresses, and chemicalenvironment.Forcomponentsoperating at hightemperatures where creep could occur, the influence of creep-fatigue interaction on the fracture process has been recognized in the recent years. Their understanding is, however, far from satisfactory. In the case of lead alloys, which operate at room and higher temperatures, the creep-fatigue interaction is important. However, most earlier studies did not explicitly recognize such interactions. Use of caution in using such data is warranted.

Chapter 2

170

J’

M05 OJI

OJZ Creep rate (1 0-4 % I h)

0.03% Ca A 0.03% Ca @

#

,. A

X

0

[I]

0

I1

ca (According to MOOREandothers [184]). special 0.01% Ca 0.05% Ca (According toGREENWOODandWORNER[211]). 0.1% Cn 0.10% Ca quenched 0.10% Ca alrcooled 0.12% ca quenchedCast.Bleiforschungsstelle [ 76 1. 0.13% Ca aircooled 0.027% Ca at 30°C. (According to GOHN among others [208]).

a 0.04%

+ o.037% 0.03% Ca Ca } Ca A ,,lo5%ca 0 0.055%

l

(According t o DOLLINS[207]).

} (According to GREENWOOD andCOLE [219]

),

Figure 64 Creeprates of lead-calcium alloys [2,76,184,207,208,211,2191. (Courtesy of Springer Verlag, New York.)

A.

Presentation of Fatigue Data

The general types of fluctuating stress could be described using Figure 76 [ 1791. In a completely reversed stress cycle, the mean stress is zero and the maximum and minimum stresses are equal and of opposite sign. An idealized situation as illustrated in Figure 76a is produced by a rotating bending machine. A repeated stress cycle refers to the case in which the mean stress is not zero. As opposed to the completely reversed and repetitive stress cycles, one may have a random fluctuation of load. The stress cycle consists of two components a steady or mean stress c,,, on which an alternating or variable stress c<, is imposed:

171

Properties of Lead and Its Alloys

Time to reach 1% extension (h) 0

o

x

# 8 0

e 0

+ + +

Pure lead 0.027% Ca Chemical lead 1% Sb Pure lead 0.06% Te Extruded in laboratory. Chemical Lead Pure Lend Chemical Lead 0.9% Sb Secondary Lead 37" Sn Cable Sleevcs. Secondary Lead 0.7% Sb

11

+

+ +

Figure 65 Stress versus time for 1 % creep in lead and lead alloys (2,2081. (Courtesy of Springer Verlag, New York.)

where u,,,;,,is the maximum stress, u,,, is the minimum stress, and u, is the stress range; Mean stress:

u,,, =

urnax

+ 2

urn,,,

Two more parameters, the stress ratio R and amplitude ratio A , are used in the description of stress cycles. These are defined as follows: Stress ratio:

R

Amplitude ratio:

A

Engineering fatigue data are usually presented in the form of S-N

172

Chapter 2

Temperature ("C) Figure66 Temperaturedependence of stress which causes 1% strain per year [2,219]. (Courtesy of Springer Verlag, New York.)

curves, a plot of stress S against the logarithm of the number of cycles to failure at that stress level (Figure 77) [179]. The value of stress could be Each curve is for a specified value of R , A , or unl. either U(,,U,,,,or urnax. Highcyclefatigue is concernedwithfractures at N > 10' cycles.Under these conditions, the strains are predominantly elastic. In the low cycle fatigue, N < lo4 cycles, the stresses are higher and the fraction of total strain that is due to plastic strain becomes appreciable. Low cycle fatigue tests are usually carried out under strain cycle control. at The S-N curves for steel and few other metals become horizontal a limiting stress. Below this limiting stress, they endure infinite cycles without failure. This limiting stress is known as endurance limit or fatigue limit. In many nonferrous metals, including lead and lead alloys, S - N curves show amonotonicdecreasewithincreasing stress cycles. In thesecases, it is common practice todefinefatiguestrengthas the stress at whichfailure occurs after an arbitrary number of cycles,usually 1 X IO8 or 5 X lo8. Even at the highest number of cycles (100 million), a horizontal asymptote

173

Properties of Lead and ItsAlloys

Creep rate (l 0-4% I h) 0'04'0 0 0.055% CU

0.05% Cu

o.l

m 0.014% Cu Cu 0.042% Cu

} (According t.o MOORE amongothers [l841). ] (According t o GREENWOODand WORNER[21

l ] ).

(According to GREENWOODand COLE 12221).

B 0.037% 0

A 0.059% Cu A 0.1% Cu

(According to DOLLINS [223] ). (According to HOPRIN and THWAITES [200] ).

Figure 67 Creeprates of copper-alloyed lead [2,184,200,211,222,223]. (Courtesy of Springer Verlag, New York.)

Figure 68 Effect of extrusion temperature on creep strain of commercial lead and of copper-alloyed lead, at a tensile stress of 1.5 MPa [ 2 ] . (Courtesy of Springer Verlag, New York.)

Chapter 2

174

3

a005

..

Creep rate

0.018% Ag -1- 0.004% Cu 0.005% Cu

I h)

j

+ } (According to MCKEOIVN andHOPKIN 12241 ). # 1%Ag 0.0024%Ag + 0.06% CU (According to DOLLINS [223]). A 0.005% Ag + 0.064% Cu A 0.0054% rig + 0.061% C,) (According to GOIIh- among others (at 30°C) [208]). 0 0.005% Ag

0.01% Ag [211] ). (According t o GREENWOODand U'ORNEK

0.05% Ag

Figure 69 Creep rates of silver-alloyed lead and of copper-alloyed lead [2,208,209,211,223,224].(Courtesy of Springer Verlag, New York.)

Figure 70 Comparison of creepstrainsin some lead alloys (cable sheathings) at various temperatures after 10,000 h under 1.37 MPa tensile stress; extrapolated from tests of 2000 h duration 12,2261. (Courtesy of Springer Verlag, New York.)

175

Properties of Lead andIts Alloys

d

b

C

e

f

h

Figure 71 Temperaturedependence of creeprate of lead and leadalloys: (a) 0.03% Ca + 0.04% Cu; (b) 0.03% Ca + 0.05% Cu; (c) 1.0% Sb; (d) 2.0% Sn; (e) ASTM Grade I11 with 0.07% Bi; (f) Grade I1 with 0.06% Cu + 0.04% Bi; (g) Grade I11 with 0.09% Bi; (h) Grade I1 with 0.04% Cu + 0.03% Bi; (i) U-Lead (Port Pirie) with a total of 0.009% impurities. (a) to (i): [2,184,216,227]. (Courtesy of Springer Verlag, New York.)

176

Chapter 2

-9.5 -10

-0.2

0

0.2

0.4

0.6

08

1

1.2

Log (Stress, MPa)

Figure 72 Thestressdependence of thesecondarycreepratefor 99.99% pure lead at various temperatures [ 2 2 8 ] .(Courtesy of ILZRO, Dr. M. K. Sohoto and Prof. J. R. Riddington, Univ. of Sussex, Brighton, UK.)

-5.5 6

"6 . 5 v)

@I

-7

2

.-c -1.5

g

2 "

E? -8.5

J

-Q -9.5 -10 -0.2

0

0.2

0.4

0.6

0.8

1

l.2

Log (Stress, MPa)

Figure 73 Thestress dependenceof thesecondarycreeprate

for Pb-0.06 Cu-

0.04 Te alloy at various temperatures [228]. (Courtesy of ILZRO, Dr. M. K. Sohoto

and Prof. J. R. Riddington, Univ. of Sussex, Brighton, UK.)

177

Properties of Lead andIts Alloys

0.2

0

0.2

0.8 0.4

1

0.0

1.2

Log (Stress,MPa)

Figure 74 The stress dependence of thesecondarycreeprate for Pb- 1.2% Sb alloy at varioustemperatures [ 2 2 8 ] . (Courtesy of ILZRO, Dr. M. K. Sohoto and Prof. J. R. Riddington, Univ. of Sussex, Brighton, UK.)

-IO J -0.2

0

0.2

0.4

0.6

0.8

1

1.2

Log (Stress, MPa)

Figure 75 The stress dependence of thesecondarycreeprate for Pb-0.06% Cu alloy atvarioustemperatures [228]. (Courtesy of ILZRO, Dr. M. K. Sohoto and Prof. J. R. Riddington, Univ. of Sussex, Brighton, UK.)

Chapter 2

178

Table 34 Summary of Tests Carried out on 99.99% Lead at Various Stresses and Temperatures 12281. (Courtesy of ILZRO, Dr. M. K. Sohoto, and Prof. J. R. Riddington, University of Sussex at Brighton, UK.) 5°C Stress (MPa) 1.0 2.5 5.0 7.5 10.0 12.5

40°C

20°C &>

(s

.I)

6.02E-10 1.30E-09 2.27E-09 4.48E-09 1.838-08

Stress (MPa) 1 .o

2.5 5.0 7.5 10.0 12.5

b, (s-')

2.628-09 3.53E-08 6.34E-08 9.23E-08 1.43E-07

60°C

Stress (MPa)

6, (s-I)

Stress (MPa)

1.0 2.5 5.0 7.5 10.0 12.5

7.77E-10 3.14E-09 7.91E-08 1.328-07 5.60E-07 8.65E-07

2.5 5.0 7.5 10.0 12.5

e.> (s-')

1 .o

-

Table 35 Summary of Tests Carried out on Pb-0.06% Cu-0.04% Te Alloy at Various Stresses and Temperatures 12281. (Courtesy of ILZRO, Dr. M. K. Sohoto, and Prof. J. R. Riddington, University of Sussex at Brighton, UK.) 5°C Stress (MPa) 1 .o 2.5 4.0 5 .o 6.5 7.5

10.0 12.5

20°C

6, (s-I)

-

7.02E-10 -

3 . I9E-09 7.ME-09 1.16E-08 2.33E-08

Stress (MPa) 1 .o

2.5 4.0 5 .O 6.5 7.5 10.0 12.5

40°C 8, (s

I)

7.55E-10 2.568-09 3.7 1 E-09 5.43E-09 1.81 E-08 3.53E-08 7.32E-08 I .37E-07

Stress (MPa)

60°C E\ (s I )

1 .o

-

2.5 4.0 5.0 6.5 7.5 10.0 12.5

2.82E-09

-

1.43E-08 -

4.53E-08 8.80E-08 1.688-07

Stress (MPa) 1 .o

2.5 4.0 5.0 6.5 7.5 10.0 12.5

e, (s

I)

4.34E-09 7.9 1E-09 I . 12E-08 6.34E-08 8.85E-08 1.62E-07 1.76E-07

Properties of Lead and Its Alloys

179

Table 36 Summary of Tests Carried out on Pb-1.2% Sb Alloy at Various Stresses and Temperatures 12281. (Courtesy of ILZRO, Dr. M. K. Sohoto, and Prof. J. R. Riddington, University of Sussex at Brighton, UK.) 20°C

5°C Stress (MPa)

6, (s-I)

I .o 2.5 4.0

2.898-09

5.0 7.5 10.0

8.688-09 8.218-08 -

-

-

Stress (MPa) 1.0 2.5 4.0 5.0 7.5 10.0

40°C

t, (s

I)

1.368-09 1.868-08 4.908-08 8.51E-08 3.838-07 -

60°C

t,

Stress (MPa)

(s-l)

3.858-08

1.0 2.5 4.0 5.0 7.5 10.0

-

1.19E-07 2.698-07 3.078-07

e,

Stress (MPa)

(s-')

I .o 2.5 4.0 5.0 7.5 10.0

1.148-07 3.96E-07 9.OIE-07 -

-

Table 37 Summary of Tests Carried out 011 Pb-0.06% Cu Alloy at Various Stresses and Temperatures [228]. (Courtesy of ILZRO, Dr. M. K. Sohoto, and Prof. J. R. Riddington, University of Sussex at Brighton, UK.) 5°C

e,

Stress (MPa) 1.o 2.5 4.0 5.0 7.5 10.0

20°C (s-')

2.85E-09 1.038-08

2.288-08 5.938-08

Stress (MPa) 1.0

2.5 4.0 5.0 7.5 10.0

40°C

t, (s

I)

7.858-10 2.748-09 7.07E-09 1.768-08 6.758-08 I .60E-07

Stress (MPa) 1.0 2.5 4.0 5.0 7.5 10.0

60°C 6,

(s

I)

2.778-09 6.988-09 -

1.54E-08 1.048-07 -

Stress (MPa) 1.0 2.5 4.0 5.0 7.5 10.0

E,

(s-l)

2.50E-09 8.748-09 -

2.568-08 1.1 IE-07 -

Table 38 Summary of Norton's Values for Pure Lead and Three Lead Alloys [228]. (Courtesy of ILZRO, Dr. M. K. Sohoto, and Prof. J. R. Riddington, University of Sussex at Brighton, UK.) Materials

5°C

20°C

40°C

60°C

99.99% lead Pb- 1.2% Sb Pb-0.06% CU Pb-0.06% Cu-0.04% Te

1.26 2.89 2.12 2.12

2.4 1 2.70 2.34 2.10

2.93 1.57 I .63 1.57

1.87 1.78 1.87

Chapter 2

180

Table 39 Summary of Activation Energies Q, (kJ/mol) Values for Pure Lead and Three Lead Alloys [228]. (Courtesy of ILZRO, Dr. M. K. Sohoto, and Prof. J. R. Riddington, University of Sussex at Brighton, UK.) 1.0 MPa 2.5 MPa

Materials

5.0 MPa ~

99.99% lead 72.1 1.2% PbSb 44.8 Pb-0.06% 21.4 CU 10.6 331.441.330.335.5Pb-0.06% Cu-0.04% Te

17.9

5.3 27.9 -48.5 18.1 24.0

7.5MPa 10.0 MPa ~

~~~~

68.6 48.5

68.7 -

to S-N curve of lead is not reached [23l]. In determining the fatigue strength of lead, the number of cycles is set high and is stated in the results. In the case of low cycle fatigue, the plastic strain range, AE,,, during a fatigue cycle is plotted against N, and usually a straight line is obtained (Figure 78) [232].Such behavior, known as the Coffin-Manson relationship, is described by [233]

where A E , , / ~is the plastic strain amplitude, E;.- is the fatigue ductility coefficient and is equal to the strain intercept at 2N = 1, 2N is the number of strain reversals to failure, andc is the fatigue ductility exponent which varies from -0.5 to -0.7. Under varying conditions of fatigue loading, one can estimate the linear cumulative damage and the remaining part life using Miner's rule. If n,, n2, . . . , n, represent the number of cycles of operation at a specific stress level and N , , N 2 , . . . , N k represent the life in cycles at these stress levels, then failure will occur when

This rule is empirical in nature and does not have a is, however, widely used [234].

B.

firm physical basis. It

Structural Features of Fatigue

Two structural features that are observed to develop on the surface of the component during fatigue deformationare the ridges and grooves called slip-

181

Properties of Lead and Its Alloys

+

+ I

+ In

In

E

G I

Cycles-

V

Figure 76 Thegeneraltypes of fluctuatingstress [179]. (Reprintedwithpermission from McGraw Hill Companies, New York.)

Number of cycles to failure, N Figure 77 Typical S-N curves inmetals [1791. (Reprintedwithpermissionfrom McGraw Hill Companies, New York.)

Chapter 2

0

" L

-400.0 0.1

1

IO0

10

1,000

10,000

Cycles to Failure Figure 78 Plot of plasticstrainrange,

AE,,, versus N for Type 1020 steel [232].

(Courtesy of TMS, AIME, Warrendale, PA.)

band extrusions and slip-bandintrusions. The fatigue cracks has been shown to initiate at intrusions and extrusions. A mechanism for producing slip-band extrusions and intrusions has been suggested by Wood 1235,2361. Based on microscopic observations of slip produced by fatigue, it was suggested that the slip bands are the result of a systematic buildup of fine slip movements, corresponding to movements of the order of 1 nm. Slip produced by static deformation would produce a contour at the metal surface similar to that In contrast, the back-and-forth fine-slip shown in Figure79a[235,236]. movements of fatigue could build up notches (Figure 79b) or ridges (Figure 79c) at the surface[235,236].Thenotchwouldbea stress raiser witha notch root of atomic dimensions. Such a situation might well be the start of

Figure 79 Development of intrusions and extrusions by fatigue loading (a) surface steps, (b) intrusions, and (c) extrusions.

Properties andof Lead

Its Alloys

183

a fatigue crack. This mechanism for the initiation of a fatigue crack agreement with experimental observations.

C.

is in

Fatigue Strength of Lead and Lead Alloys

An S-N curve for lead in air and in vacuum is shown in Figure 80 [2,231]. The data were obtained using a Haigh direct stressing machine in vacuum. in this case.The The S-N curve is a straight line withanegativeslope fatigue strength (at IO' cycles) is higher in vacuum than in air. Tests in oil and even acetic acid also show higher fatigue strength than that in air [237]. The difference in strength increases with the duration of the test. Table 40 presents data on fatigue strength of lead and lead alloys in different enviin air tendsto be intergranular, whereas that in ronments[238].Fracture vacuum exhibit 45% shear fracture. [ 184). The The fatigue strength of lead has a frequency dependence stress fluctuations in cablesheathingand outdool. installations frequently arise fromtemperaturechanges that occurover the day, andfrequencies commonlyencountered[239] will have - 1 cycles/dayas the lowestfrequency. Another source of themla1 stress is the variations in current in the case of high-voltage power transmission cables. Fatigue behavior of Pb and 1650 per the Pb-l wt.% Sb alloy at frequencies of 0.25perminuteand minute are compared in Figure 81 [239]. At an alternating strain of +-0.2%, 80

1

'b

5 Figure80 S-N curves for lead in air and in vacuum [2,231 1. (Courtesy of Springer Verlag, New York.)

Chapter 2

184

Table 40 Effect of Surrounding Media and Protective Coatings on the Fatigue Resistance of Lead and Lead Alloys [2,238). (Courtesy of Springer Verlag, New York.)

Materials Pb

+ 1.5% Sn + 0.25% Cd Pb + 0.5% S b

Pb

+ 0.25%

Cd

Surrounding medium or protective coating

Semirange of stress ( 2 MPa)

Air Normal acetic acid Rape oil Vaselin Air Petroleam bitumen Air Rape oil Vaselin

0.54 0.54 0.54

0.62 1.o

1.2 1.2

1.4 1.4

Endurance cycles ( 10")

1.3 8.5 u 7.9 9.8 U 1.6 9.3 u 1.3 9.6 6.4

"U = unbroken.

708 Cycles to failure Figure 81 Effect of frequency on number of cycles to failure [2,239]. (Courtesy of Springer Verlag, New York.)

Propertiesof Lead and Its Alloys

185

pure lead withstands10,000and20,000cycles respectively (lives of 700 and 2 h). In lead with 1 wt.% Sb, the corresponding number of cycles are 130,000and2million(lives of 8670 and 20 h). If the duration of the vibration cycle exceeds 4-6 min, then fatigue strength does not seem to depend on frequency [240]. It seems that with harder alloys, the dependence of fatigue strength onfrequency is less marked. On the contrary, the life expressed in units of time decreases in all known cases at constant amplitude withincreasingfrequency of vibration (Table 41) [2,238]. The frequency dependence arises from the creep-fatigue interaction and environmental effects. Figure 82 presents the fatigue life of lead in units of time as a function of frequency at two different alternating strain levels [2,241]. The data from McKeller [2,238] on pure Pb and Pb-Sb-Sn and Pb-Sb alloys are shown in Table 42. The yield strength increases with decrease in grain size and a similar trend is expected for high cycle fatigue strength. Effect of grain size on the fatigue strength of lead was examined by Hopkins and Thwaites [200] on an alloy with 0.85% Sb which did not recrystallize during the tests. The SN curves were obtained using a rotating bending fatigue specimens at 3000 stress cycles per minute. In this study, the endurance limit was designated as a stress that causes failure in 20 million cycles. A superiority offinegrained material can be seen from these data presented in Table 43 [2,200]. The curves obtained with Pb-Sn alloys show the effect of alloy concentration and grain size simultaneously (Figure 83) [2,200]. The stability of microstructure during fatigue is important in the assessment of fatigue strength. Recrystallization and grain growth during testing leads to a reduction of fatigue strength. In fine-grained Pb and Pb-Sn alloys with less than 1 wt.% Sn, recrystallization is observed at a stress level just above fatigue strength. Tests with a single cycle per day are of significance for evaluating the effect of daily temperature fluctuations on the durability of lead-sheathed

Table 41 Effect of Cyclic Speed on Endurance of Lead Alloy Under Conditions of Rotating Flexure [2,238]. (Courtesy of Springer Verlag, New York.) Cyclestofailure Strain

at

3000 1.35 cycles/min cycles/min cycles/min cycles/min

Material

(%)

Pure lead Pb-0.2% Sn Pb-0.2% Sn-0.85% Sb

0.1 0.09 X IO6 0.1 0.2 X 10* 0.1 1.0 X IO*

4,700 16,600 100.000

Timetofailure

(h) at

3000

1.35

0.5 1.1

58 205 1,230

S .S

186

Chapter 2

I

100

1000

ro

9

Number of cycles per day

Figure 82 Relation between fatigue life in units of time and the frequency at two different alternating strain levels [2,241]. (Courtesy of Springer Verlag, New York.)

telephonecables, lead pipes, and so forth.The nightly coolingcausesa contraction,followed by the expansion of lead duringwarming. In highvoltage cables, longitudinal movements result from fluctuations in current day. However, both are much load. It is more frequent than one cycle per smaller than the frequency of fatigue testing machines. A frequency of 15 cycles/h has been used for cable sheaths [239]. For comparison of the fatigue strength of different alloys, the use of simple test pieces in the form of

Table 42 Fatigue Resistance of Extruded Lead and Lead Alloys in Direct-Stress Tests 12,2381. (Courtesy of Springer Verlag, New York.) Endurance limit at IO7 cycles, ?MPa Material

Pure lead Lead + 0.06% Te Lead + 1.5% Sn + 0.25% Cd Lead + 0.5% Sn + 0.25% Cd

At room temperature 2.8 7.6 8.8 11.5

At 100°C 1.2 5.1 4.3 6.2

187

Properties of Lead and Its Alloys Table 43 Effect of Grain-Size on the Fatigue-Resistance of the Lead-0.85% Antimony Alloy 12,2001. (Courtesy of Springer Verlag, New York.) Extrusion temp. ("C) 160 200 250 300

Average grain area (mm')

Endurance limit ( 2MPa)

0.0039 0.012 0.043 0. I9

9.7

8.6 8.1 7.1

extruded flat bars are recommended. However, in predictions of actu' 1 service performance, test piece geometry and testing conditions should be simulated as closely as possible. Pfender and Schulz [97] consider alternative bending strain as more significant than bending stress for cable sheath applications. They compared the fatigue behavior of soft lead containing 0.025% Sb, 0.046% Sn, 0.001% As, 0.002% Zn, 0.006% Cu, 0.001% Ag, 0.02% Si, and traces of Cd with a series of lead and lead alloys. Figure 84 presents data for soft lead and Pb containing 0.1% Sb, 0.1% Sn, and 0.08% As [2,97]. The data were

Average grain size (mm2) Figure 83 Effect of grain size on fatigue strength of Pb-Sn alloys. The grain size is expressed in terms of average projected grain area 12,2001. (Courtesy of Springer Verlag, New York.)

188

Chapter 2

Figure 84 S-N curves of commerciallead (Pb-0.025% Sb-0.046%Sn-0.001% As-0.002% Zn-0.006% Cu-0.001% Ag-0.02% Si-traces of Cd) and Pb-0.1% Sb0.1% Sn-0.08% As [2,97]. (Courtesy of Springer Verlag, New York.)

obtained using flat test pieces in a plane-bending fatigue machine. Figure 85 presents the data for all alloys [2,97]. The 5.5% Sb alloy shows good fatigue resistance when plotted in terms of either alternating stress or strain. However, when plotted in terms of stress, it is more marked. The decrease of stress with cycles suggests the beginning of damage to the material. With the use of alternating strain behavior as the criterion, the differences between unalloyed and alloyed lead becomes progressively smaller with increasing amount of strain. The curves for various alloys intersect at a strain of 0.1% and a number of cycles of 5 X 10' (Figure 85). This is the transition from a high cycle fatigue regime to the low cycle fatigue regime.In the low cycle fatigue regime, the ductility of lead alloy is important, whereas in the high cycle regime, the strength and hardness of the material is important. This is confirmed by the observations of Gohnand Ellis [239] (Figure86),who suggest a leveling of the different types of lead with respect to alternating strain behavior at -1% and a number of cycles at 2 X lo4. At alternating strains below 0.4% (high cycle fatigue regime) such as that in cable sheaths, the fatigue life of the cable can be increasedby alloying. The fatigue behavior of alloys with (1) 1% Sb, 0.15% As, 0.1% Sn, and 0.1% Bi and (2) that with 0.65% Sb and 0.25% Zn can be regarded as very similar (Figure 84). Then, behavior of very impure lead is similar to that of Pb with 0.64% Sb.

Properties of Lead and Its Alloys

189

Cycles to failure Figure 85 S-N curves for leadalloys: (A) commerciallead; (B) Pb-0.08% As; (C) 0.8% Zn; (D) 1.5% Zn; (E) 0.6470Sb; (F) 0.47% Sb + 0.18% Cd; (G) 5.5% Sb [2,97]. (Courtesy of Springer Verlag, New York.)

The temperature dependence of fatigue strength is important because of the increasing impact of creep-fatigue interaction. A decrease of fatigue strength with temperature is expected in all cases, as can be seen from Table 42. Comparisons are usuallymadeon the basis of alternatingstress. According to Hopkins and Thwaites [200], antimony in lead increases the fathe Sb tigue strength as long as the alloys are single phase. However, as increases from 0.5 to 0.85 into the two-phase region, the fatigue strength

190

Chapter 2

0.010

+H t ";--

0.008

At m0 c y k perminute

Q)

K 0

g 0.006

& l

--

"

F v)

m

1

0 k

0.004

0.002

0

' 2 Cycles to failure

Figure 86 S-N curves of some cable sheathing alloys [2,239]. (Courtesy of Springer Verlag, New York.)

increase is not very significant (from 6.89 to 7.74 MPa). Additions of Sn 0.001% As,afurther showa similar effect. In alloyswith0.9%Sband increase in fatigue strength is obtained.Thefatigue strength increase in direct-tension compression tests in lead was obtained with small additions of c u 12421. Alloying of lead with Cd, Sb, or Sn alone or combined considerably increased the fatiguestrength,asdoesalloyingwith Te, Li, Ca, andCu. exMany alloys with high fatigue strength also exhibit high hardness, as pected. Pb-0.5 Sb-0.01 Te, Pb-0.5 Sb-0.15 As, and Pb-As-0.1 Sn-0.1 Bi show good fatigue strength among the 19 alloys examined by Hanffstengel and Hanemann [243]. In particular, the alloy with Te had a finer grain size and showed higher fatigue strength. Figures 87a and 87b illustrate the intergranular fracture of commercial lead and of arsenical Pb-antimony alloys in fatigue [2,243]. Pb-Ca alloys, however, show intragranular fracture (Figure 87c) [2,243].

Properties andof Lead

Its Alloys

191

Figure 87 The intergranularfracture of (a)commerciallead,(b) arsenical Pbantimony alloys, and (c) Pb-Ca alloys in fatigue [2,243]. (Courtesy of Springer Verlag, New York.)

192

Chapter 2

A summary of fatigue strength of alloys with different thermomechanical history under different loading conditions are summarized in Tables 4446 [2,169,244].

V.

CORROSION PROPERTIES

Lead has an excellent record of service in the four major types of environments: chemical, atmosphere, water, and underground [2,61]. Resistance of lead to corrosion in contactwith sulfuric acidhasbeen critical in many chemical industries, including paper, petroleum, plastics, and photographic materials. Of particular importance in recent years has been the use of lead in the protection of devices for the removal of sulfur from industrial waste gases. Several industrial processes, such as ore roasting or burning of fossil fuels for power generation and industrial heating, produce large volumes of waste gases from which sulfur-containing species must be removed. Because of its excellent corrosion resistance in different water environments, lead has shown a long and reliable service in lead pipes for transporting water and in applications such as a water barrier in pools and showers, waterproofing, and flashings. Although current environmental regulations do not permit its use in the drinking-water supply system, lead or lead-lined components continue to be used in the handling of alum used in industrial-water-treatment systems. Thousands of kilometers of lead water service pipes and lead-sheathed cables have shown reliable long-term performance worldwide because of the extraordinary corrosion resistance of lead alloys to a variety of soil types. Using lead-covered copper for grounding systems, as for power plants, reprotection. The use of lead in duces or eliminates the needforcathodic nuclear-waste burial arises from its excellent resistance to corrosion in soil in addition to radiation shielding characteristics. Lead roofs, whether sheet lead, lead-coated copper, or perhaps terne-coated steel, have provided a superior performance in a variety of atmospheres in different partsof the world. The excellent corrosion performance of lead and its alloys is attributable to the formation of a strong, adherent, and impermeable protective film that is stable orinsoluble in the solution withwhich it is in contact. An appreciation for the ability for and the limits of corrosion protection afforded by lead can be gained by a brief examination of the film formation process and its stability. In the next sections, the nature of lead corrosion in aqueous solutions, the experimental corrosion rate data in several industrial chemical solutions of interest, and corrosion behavior under atmospheric exposure, soil exposure, and exposure to natural and industrial waters are presented.

9

0

Table 44

P

Fatigue Strength of Lead

Grade 99.99% Lead

Treatment Extruded Extruded, 100 h, 250°C Cold rolled Cold rolled 1 h,

T

Machine Haigh Push Pull Haigh Push Pull Haigh Push Pull Haigh Push Pull

No. of cycles

Frequency (min-')

Fatigue strength (MPa)

1o7 1o7

2000 2000

22.7 2.7

1o7 1o7

2 v)

5 Ref.

6 m

2 2

m 3 P

P

2000 2000

2.6 3 .O

2 2

2200 2200 700 700 2500

2.5 5.7 1.5 4.8 4.5

2 2 2 2 2

2000 3000 740 800 800

2.1-2.9

250°C

Broken Hill (99.99%) Commercial lead Commercial lead with 0.09% Bi Commercial lead 99.99% Lead

Commercial lead ~

"Extrapolated value.

Extruded Extruded Extruded Extruded Extruded -

Extruded Extruded Extruded Extruded Extruded

-

P

2 9 v)

Haigh Push Pull in air Haigh Push Pull in vacuum Rotating Illinois Plane Bending Illinois Plane Bending

3 x lo7 3 x 107 5 x lo7

Haigh Push Pull Haigh Push Pull DVL Plane Bending Rotating Rotating Rotating

1o7 3.6 x lo7 lo7" 3.6 x lo7 3.6 x lo7 2 x 10'

1 o7 1o7

2.8

3.1 1.3 2.2 2.0

Table 45

Fatigue Strength of Lead Alloys

Addition

Wt. %

Ca

0.026 0.038 0.04

0.03 0.028-0.039 0.06 0.07 0.04

0.06

Treatment

Solid solution + aging precipitation aging Solid solution + precipitation Extruded Extruded Solid solution + aging + precipitation

+

Machine

1o7

+

-

Extruded Solid solution + aging + precipitation Extruded and age hardened Extruded and stored 2 weeks Extruded and stored 6 months Extruded and stored 6 months

No. of cycles

Frequency (min-.')

I o7 lo7 10'

2500 700 2000

-

10'

s

s

x 10' x lo7

244 -

2 2 2 244

10.0

-

4.6-5.8 7.7

18.7-23.8

2 2 244

10.7 10.3 11.0-1 1.4

5.6- 10.3 2000 700

Ref.

244

4.7-5.7

5 x 107 Haigh Push Pull Rotating

UTS (MPa)

7.1

s x 107 Haigh Push Pull

Fatigue strength (MPa)

-

I o7

740

9.8

Rotating

5 x lo7

800

5.9

23.9

2

Rotating

sx

lo7

800

7.2

28.6

2

Rotating

s

x lo7

800

7.9

30. I

2

DVL Plane Bending

2

0.04

Extruded Extruded

Cd

0.3 0.3 0.5

cu

0.06

Sb

0.25 0.50 0.75

I .o

Rolled 1 h, 250°C Rolled 1 h, 250°C Extruded Precipitation Extruded in laboratory Extruded in laboratory Extruded in laboratory Extruded Extruded Extruded Rolled 1 h, 250°C Extruded and stored 6 months Extruded Extruded in laboratory Aging

Illinois Plane Bending Illinois Plane Bending

-

Haigh Push Pull Haigh Push Pull Haigh Push Pull Haigh Push Pull

-

Rotating Illinois Plane Bending Haigh Push Pull

1700

10.3

31.0

2

lo7"

1700

8.3

26.3

2

6.3 x lo7" 1o7 1o7

-

Haigh Push Pull

lo7"

s

I o7 I o7 I o7 I o7 I o7 x lo7 -

2200 2200 2200 2500 700 2000 700 -

7.0 6.3 9.7 8.8 4.3 6.9 5.8 7.6 9.1 9.0 8.3 8.1 2.1-3.1 9.7 9.3 3.6

5 x lo7

800

I o7

1700

6.9

I o7 5 x lo7

2200

9.6 2-7

-

20.7

2 2 2 2 2 244 2 2 2 2 2 2 2 2 2 2

22.1

2

-

-

-

-

-

19.0-27.6 -

-

2 244

Table 45

Continued ~~~~

Addition Sn

~

Wt. % 1.o

2.0

Treatment Extruded in laboratory Extruded in laboratory Extruded Extruded -

3.0

Te

0.05

Cd with Sn Cd with Sb Sn with Cd + Sb Sb with As

0.25 1.5

0.25 0.5 1.2 0.2 0.1 1.o 0.05

"Extrapolated value.

Aging Rolled 1 h, 250°C Extruded in laboratory Extruded

Machine Haigh Haigh Haigh Haigh Haigh

Push Push Push Push Push

-

Pull Pull Pull Pull Pull

Haigh Push Pull Haigh Push Pull Haigh Push Pull Haigh Push Pull Rotating -

Extruded 1 h, 250°C Extruded 1 h, 250°C Extruded

DVL Plane Bending

Extruded

DVL Plane Bending

No. of cycles I o7 1 o7

I o7 10'

I o7

Frequency (rnin-') 2200 2200 2500 700 2000

5 x lo7

Fatigue strength (MPa)

UTS (MPa)

Ref.

5.1 6.8 6.6

4.8 6.1 5.5 8.1

1o7 2 x 107

2200

740

7.2 7.4 7.7 5.9 8.5 7.6 11.1 10.6 6.9

740

12.3

2 x lo7

-

1074

-

2

Properties andof Lead Table 46

Its Alloys

Fatigue Properties of Russian Cable Sheathing Alloys [ 1691

N

IO-'" (unannealed)

compositions Alloy Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb Pb

197

+ 0.05% Cu

+ 0.3% Sb + 0.5% Sb + 0.7% Sb + 1.0%Sb

+ 0.03% Te

+ 0.05% Te + 0.1% Te + 0.3% Sb + 0.03% Te + 0.5% Sb + 0.03% Te + 0.5% Sb + 0.05% Te + 0.5 Sb + 0.1 Te + 0.5 Sb + 0.1 Se + 0.5 Sb + 0.08 Cu + 0.3 Sb + 0.03% Te + 0.05% c u Pb + 0.5 Sb + 0.03% Te

+ 0.05% c u

X

0.8

5.9 1.7 1.2

2.4 2.1 5.7

7.9 12.8 12.0 14.5 15.7 6.6 4.2 1.6 2.5 15.5

N ,X IO-'" (after annealing at 100°C)

N z X IO-'" (after annealing at 250°C)

1.2 1.8 3.6 6.7 7.5 9.5 6.6 9.0 14.8

9.9 10.3 14.6 16.7 6.9 7.4 10.8

12.5

9.9

"Cycles to failure in alternating bend tests at an amplitude of t0.5 mm and a frequency of 7 Hz.

In presenting this information, the LeadIndustryAssociationmanual corrosion behavior of lead and its alloys has been consulted.

A.

on

The Nature of Lead Corrosion in Chemical Solutions

The corrosion of lead in aqueous electrolytes is an electrochemical process. In the case of lead, the Pb is oxidized to Pb'+ at the anode. The Pb'+ ions either enters the solution at the anodic sites as metallic cations or form solid insoluble compound films. The reaction at the anode could be represented by Pb

+ Pb2' + 2e-

(24)

This oxidation reaction that takes place at the anodic sites is accompanied by a reduction of some constituent in the electrolyte at the cathodic sites. In neutral salt solutions, the cathodic reaction is the reduction of dissolved oxygen:

Chapter 2

198

In acid solutions free of oxygen, the corresponding cathodic reaction is

2H'

+ 2e + H2

During the corrosion of a material such as lead, local anodes and cathodes the surface of lead that may havea may be set up on adjacentsiteson different chemical activity because of differences in composition, crystalline orientation or structure, stress variations, and temperature. Structural inhomogeneities of importance include inclusions and grain boundaries. In the case in which two metals are coupled, one of the metals takes on a net anodic behavior and corrodes in preference to the more noble metal that has become a net cathode as a result of the coupling of the two metals. In most environments, lead is cathodic to steel, aluminum, zinc, cadmium, and magnesiumand, thus, will accelerate corrosion of these metals. In contactwith titanium and passivated stainless steels, lead will serve as the anode of the cell and will sufferacceleratedcorrosion. The corrosion rate in both the casesdepends on the difference in potential between the twometals, the ratio of their areas, and their polarization characteristics. As the net charge transferred at the anode should be the same as that at the cathode, the corrosion rate could be controlled by retarding either the anodic or the cathodic reaction. In the case of lead and its alloys, the solubility and physical characteristics of the corrosion product film formed at the anode is the rate-determining factor; thus, the corrosion rate of lead is usuallyunderanodic control. Thecorrosionproduct films formedon the surface of lead in many corrosion environments are relatively insoluble and impervious salt films that tend to retard further attack. The formation of such protective films is responsible for the high resistance of lead to corrosion by sulfuric, chromic, and phosphoric acids. Leadformsadherent protective films overabroadrange ofpHin aqueous solutions except at very high and very low pH levels. The exceptions at the low pH level include sulfuric and phosphoric acids. Soft water will cause some corrosion of lead, but in water containing mineral salts such as carbonates and sulfates, aprotective lead-salt film forms, limiting further attack. The solubility of the protective film depends on factors such as concentration and temperature. Table47 presents solubility data for various lead compounds in water (pH = 7) [61]. Table 48 shows the variation of the solubility of PbSO, film in sulfuric acid with concentration and temperature 1611. It is seen that lead sulfate is less soluble in sulfuric acid solution than in water. At intermediate concentrations, it is negligible. With an increase

C)

Properties andof Lead

Its Alloys

199

Table 47 Solubility of Lead Compounds 1611. (Courtesy of Lead Industries Association, New York.)

Lead Formulacompound

water

cm' of

~~~

Acetate Bromide Carbonate Basic carbonate Chlorate Chloride Chromate Fluoride Hydroxide Iodide Nitrate Oxalate Oxide Orthophosphate Sulfate Sulfide Sulfite

Pb(C2HIOZ)2 PbBr, PbCO, 2PbCO,, Pb(OH), Pb(CIO,), . HZO PbClz PbCrO, PbF, Pb(OH), Pb12 Pb(N0,)2 PbC20, PbO PbdPO,), PbSO, PbS PbS03

20 20 20

44.3 0.844 1

-

Insoluble 151.3

0.000 1 1

18 20 25 18 18 18 18 18 18 18 25

0.99

0.0000058 0.064 0.0 I55 0.063 56.8 0.00016 0.00 17 0.000014 0.00425 0.0 1244 Insoluble

18

Table 48 Solubility of Lead Sulfate in Sulfuric Acid at Various Concentrations and Temperatures [61]. (Courtesy of Lead Industries Association, New York.)

Sulfuric acid concentration (wt %) 25°C 0

Lead sulfate dissolvcd mg in 1 L of' solution at 0°C 33

0.005

X

0.0 1

7 4.6 1.8 1.2 0.5 0.4 0.4 1.2 2.8 6.5

0.1 1 10

20 30 60

70 75

80

44.5 10

8 5.2 2.2 1.6 -

1.2 1.2 1.8 3 11.5

57.7 24.0 21 .o 13.0 11.3 9.6

8 4.6 2.8 3 6.6 42

Chapter 2

200

in temperature, the solubilities increase and the corrosion rate will be expected to increase. In the case of lead in nitric acid, the lead nitrate film is soluble in dilute and intermediate strengths but not at high concentrations, and lead is quite resistant to attack in concentrated nitric acid (Figure 88). The dissolved oxygen in the solution and the velocity of corrosive medium across the metalfacealsoimpact the corrosion rates. In addition to the solubility of the surface film, other factors that influence the corrosion rate include the extent of mechanically disruptive influences such as the agitation of solution or the creep of lead that damage the film and expose a fresh surface to the corrosive medium. Depending on the corrosion environment, one usually deals with different forms of corrosion. Uniform corrosion of the material is experienced when lead is exposed to atmosphere. Pitting corrosion, which is very localized to the pit region, will be experienced when conditions of partial passivity or cavitation exists. Intergranular corrosion is experienced when the grain-boundary region has a higher relative chemical activity. Accelerated corrosion can occur when erosion, fatigue, and fretting are synergistically coupled with corrosion.

HNOB concentration (YO) Figure 88 Solubility of leadnitrateinnitricacid tries Association, New York.)

[61]. (Courtesy of LeadIndus-

Its Alloys

Properties andof Lead

201

B. Corrosion Rates of Lead in Acids Lead has high corrosion resistance to chromic, sulfurous, sulfuric, and phosphoricacidsand is widelyused in their manufactureandhandling.Lead satisfactorily resists all but the most dilute strengths of sulfuric acid (Figure to 95% at ambient tem89) [61]. It performs well with concentrations up peratures, up to 85% at 220°C and up to 93% at 150°C. Below a concentration of 5%, the corrosion rate increases, but it is still relatively low. In the lower range of concentration, antimonial lead is recommended. Similar corrosion behavior is observed with higher concentrations of chromic, sulfurous, and phosphoric acids at elevatedtemperatures.Lead finds awide application in the manufacture of phosphoric acid from phosphate rock when sulfuric acid is used in the process. Corrosion rates of lead are low for 49) [61]. However,when in purephosconcentrationsupto85%(Table phoric acid manufactured from elemental phosphorus, lead shows a higher corrosion rate due to the absence of sulfates. Lead has a fair corrosion resistance to dilute hydrochloric acid up to 15% at 24°C. The corrosion rate increases at higher concentrations and at

e l-

500

-

400

-

200

-

(U

175

-

125

-

0-5 mpv

Less than 5 mpv below 50% conc

50

60

70

80

90

Sulfuric acid (wt.%) Figure89 Corrosion rate of lead in sulfuric acid [61]. (Courtesy of Lead Industries Association, New York.)

Chapter 2

202

Table 49 Corrosion of ChemicalLeadin Phosphoric Acid at 21°C [61]. (Courtesy of Lead Industries Association, New York.)

Corrosion rate Solution

(mpy).' 3.4 4.9 5.7 6.4

20% H,PO, (commercial) 30% H,PO, (commercial) 40% H,PO., (commercial) 50% H,PO, (commercial) 85% H,PO, (commercial) 85% H,POJ (pure)

1.6

12.8

"Mils per year (= mdd X 0.127). mdd = milligrams/declmeter/day, I mil = 25.4 km.

higher temperatures (Table 50) [61]. The presence of 5% ferric chloride also accelerates the corrosion rate (Table 51) [61]. Most concentrations of nitric, acetic, and formic acids corrode lead at a rate high enough to preclude its use. However, although dilute nitric acid rapidly attacks lead, at strengths of 52% to 70% it has little effect (Table 52) [61]. This pattern of action is also true of hydrofluoric acid, acetic acid, and acid sodium sulfate. The resistance of lead to attack by hydrofluoric acid is fair. However, the corrosion rate in this acid if it is free of air is less than 20 mpy for a wide range of temperatures and concentrations (Figure 90) [61 I. In general,

Table 50 Corrosion of Lead in HydrochloricAcidat24°C Lead Industries Association. New York.)

Solution

Chemical lead (mPY)

1611. (Courtesy of

6% Antimonial lead (mpy)" 33

1% HCI 5% HCI 10% HCI

24 16 22

IS% HCI 20% HCI 25%HCI 35% HClh

31

I S0

72 170 350

160 200 540

"Mils per year (= mdd X 0.127). "Concentrated HCI commercially available.

20 43

Properties andof Lead

Its Alloys

203

Table 51 Corrosion of LeadinHCI-FerricChlorideMixturesat24°C[61]. (Courtesy of Lead Industries Association, New York.)

Antimonial Chemical 6% lead lead Solution 76

5% HCI 10% HCI 15% HCI 20% HCI

+ 5% FeCI, + 5% FeCI, + 5% FeCI, + 5% FeCI,

“Mils per year (= mdd

X

37

28

41 160 190

88 150

0.127).

lead is used with hydrofluoric acid because it is the only material in its price range that has any significant corrosion resistance. In mixed acids. the presence of sulfuric acid tends to retard corrosion rates, as illustrated in Figure 91 and by the data of Tables 53-56 [61].

C.

Corrosion Rates of Lead and Lead Alloys in Chemical Solutions

The many different chemicals and thermodynamic conditions normally encountered in the chemical environment make it difficult to present a complete set of corrosion rates for any material of construction. The corrosion data for lead under a variety of environments are presented in Tables 5759 [61]. The grade or alloy of lead to which some data apply is not specified. or copper-bearing lead. The Most tests, however,correspondtochemical data for nuclear repository applications are presented in Chapter 4.

Table 52 Corrosion of Lead in Nitric Acid [61]. (Courtesy of Lead Industries Association, New York.)

Corrosion rate (mpy)“ Solution 1% HNO,

3490

5% HNO, 10% HNO, “Mils per year (= mdd X 0.127).

140 1650 3400

600 1850

204

Chapter 2

Figure 90 Corrosion resistance of lead in air-free hydrofluoric acid[611. (Courtesy of Lead Industries Association, New York.)

D. Corrosion of Lead in Atmosphere Lead in most of its forms exhibits excellent corrosion resistance in different types of atmospheric exposure, including industrial, rural, and marine. The primary causes of corrosion in the three atmospheric environments are different. In rural areas, which are relatively free of pollutants, the only important environmental factors influencing corrosion rate are humidity, rainfall, and airflow. However, near or on the sea, chlorides entrained in marine air often exert a strong effect on corrosion. In industrial environments, sulfur oxide gases and the minerals in solid emissions considerably change patterns of corrosion behavior. Pure lead does not tarnish in dry air. In moist air, a dull oxide film forms on its surface. The studies of the mechanism of lead oxidation indicates that the film formed on the lead is extremely thin and impervious and,

205

Properties of Lead andIts Alloys 100% HNO,

Figure 91 Corrosionresistance oflead Industries Association. New York.)

tomixedacids

1611. (Courtesy of Lead

thus, protective. The character of the film and its rate of formation are determined by the adsorption of oxygen and water vapor on the lead. Althoughfactorssuchas industrial andmarinepollution,humidity, temperature, and rainfall profoundly affect the aggressiveness of the atmosphere, the protective films formed on lead are so effective that corrosion is insignificant in most natural atmospheres. The extent of this protection is demonstrated by the survival of lead roofingand auxiliary products after hundreds of years of atmospheric exposure. Table 60 shows very low corrosion rates that do not vary significantly among different locations [61].

Table 53 Effect of Nitric Acid-Sulfuric Acid

Mixture on the Corrosion of Lead at 118°C 1611. (Courtesy of Lead Industries Association, New York.) Solution ~~

~

54% H,SO, 54% H,SO, 54% H,SO,

~~

Chemical lead WPY)

6% Antimonial lead (mPY)

7.4 5.9 8.4

14 22 114

~~

+ 0% HNOz + 1% HNO, + 5% HNOz

Chapter 2

206

Table 54 Corrosion of Chemical Lead in Sulfuric Acid-Nitric Acid Mixtures [61]. (Courtesy of Lead Industries Association, New York.)

Corrosion rate (mpy) ~

Solution HISO,

50°C

HNO, + 78% 78%HZSO, + 78% H2S0, + 78% 35 H,SO, +

~~~

~~

24°C

0% 1%HNO, 3.5% HNO, 7.5%HNO,

2 12 18

l

3 3.6 4

Antimonial lead exhibits approximately the same corrosion rate in atits greater hardness, mosphericenvironments as chemicallead.However, it moredesirable for usein strength,and resistance tocreepoftenmake roofs and reflecting pools. The ability of some antimonial leads to retain this greater mechanical strength in atmospheric environments has been demonstrated in exposure tests. Lead sheets containing 4% antimony and smaller

Table 55 Corrosion of Lead in Hydrochloric Acid-Sulfuric Acid Mixtures (Courtesy of Lead Industries Association, New York.)

Antimonial 6% Chemical lead lead (mpyY’ 66°C Solution 24°C 1 % HCI

3% HCI 5% HCI

7%HCI 9% HCI 5% HCI 10%HCI 15% HCI 20%HC1 25%HCI 5% HCI 10%HCI 15% HCI 20%HCI 25%HCI

66°C

+ 9% H2S0, + 7% H2S0, + 5% H,SO, + 3% HISO,

+ 1% H$O, + 25% H2S0, + 20%HZSO, + 15% HZSO, + 10% H,SO, + 5% H2S0, + 45% H2SOJ + 40% H2S0, + 35% H2S0, + 30%H$O,

+ 25%H$OJ

“Mils per year (= mdd

X

0.127).

[61].

(mpy)“

24°C 5

9

5

14 14

32 42 45 47 22 42 74 120 I60

21 21 22

16 18 10 17

41 86 I40 62 65

30

22 80 90 I 10 150

53 x4

66

I20

x4 I20

130 210

12 41 65 74 84 34 58 180

180 210

Properties Its andof Lead

Alloys

207

Table 56

Effect of Sulfuric Acid on the Corrosion of Lead in Fluosilicic Acid at 45°C (611. (Courtesy of Lead Industries Association, New York.)

(mPY)Solution

9

5% H,SiF, 5% H,SiF, + 5% H2S0, 10% H2SiF, 10% H,SiF, + 1% H,SO, 1% H,SiF, + 10% H,SO,

Chemical lead (mPY)

6% Antimonial lead

53

77 14 1 l5 76

9 64 88 4

amounts of arsenic and tin wereplaced in semirestricted positions for 3 years. They showed less of a tendency to buckle than chemical lead indicating that their greater resistance tocreepwas retained. In the case of electrodeposited lead coatings, the porosity and pinholes present in the coating make the corrosion data suspect and misleading.

Corrosion of Lead in Various Chemical Solutions 16 1 1. (Courtesy of Lead Industries Association, New York.)

Table 57

rateCorrosion Temperature ("C)

Solution 33% Sulfuric acid sodium chloride

+ 6.7%

Sulfurous acid (3% SO,) Sodium sulfate (saturated) Sodium sulfide (10%) Triethanolamine Phthalic anhydride Calcium acid sulfite Sodium chloride (0.25-6%) Potassium nitrate (0.5- 10%) Calcium carbonate Calcium bicarbonate Sodium carbonate Magnesium sulfate "Mils per year (= mdd X 0.127).

24 60 80 24 24 24 60 88 24 8 8 X

8 8 8

(mpy 6 12 36 1 1

1 18 17 I 0.2- 1.2

0.9-3.0 0.3 0.2 0.6 0.3

N

Table 58 Corrosion of Lead in Chemical Processes [61]. (Courtesy of Lead Industries Association, New York.) Process Sulfation of oils with 25% sulfuric acid (66" Be)-14O0F (60°C) Castor Tallow Olive Cod liver Neatsfoot Fish Vegetable Peanut Sulfonation with 93% sulfuric acid (66" Be) Naphthalene Phenol Washing and neutralization of sulfated and sulfonated compounds Sulfated vegetable oil + water wash-neutralized with sodium hydroxide Naphthalene sulfonic acid + water wash-neutralized with caustic soda pH 3 Washing tallow with 2% by weight 60" Be sulfuric acid Storage of liquid alkyl detergent Storage of 50% chlorosulfonic acid-50% sulfur trioxide Mixing tank and crystallizer-saturated ammonium sulfate-5% sulfuric acid solution Splitting Olive oil and 0.5% sulfuric acid (66" Be) Storage of split fatty acids Storage of split fatty acids Extraction of aluminum sulfate from alumina Bauxite + sulfuric acid-boiling Bauxite + sulfuric acid-boiling

Temp ("C)

0 03

Corrosion rate (mpy)"

3 12 3 6 11 11

23 18 166 120

45 3

60 70 121

9 39 5 0.3 0.6 1-5

47

88

11

Liquid 0.8 Liquid level 12 Liquid 16 Vapor 5

3 p)

-2

2

h)

Alum evaporator Tank for dissolving alum paper mill Storage of 24% alum solution Dorr setting tank 19.5 Sulfuric acid, 20% ferrous sulfate, 10% titanium oxide as TiSO, Evaporator Nickel sulfate solution Zinc sulfate solution Ammonium sulfate production Solution-saturated ammonium sulfate + 5% sulfuric acid Solution-saturated ammonium sulfate + 5% sulfuric acid Acid washing Lube oil-treatment with 25% sulfuric acid Sludge oil + 15% sulfuric acid-stream treatment Benzol (crude)-treatment with 3% sulfuric acid washed with water, neutralized with lime Tar oil-treatment with 25% sulfuric acid, washed with water, neutralized with sodium hydroxide Wet acid gases from regeneration of sulfuric acid Polymerization Polymerization of butenes with 72% sulfuric acid Polymerization of butenes with 72% sulfuric acid Viscose rayon spinning bath Evaporator-6% sulfuric acid, 17% sodium sulfate, 30% other inorganic sulfates Evaporator-concentrated bath of 20% sulfuric acid, 30% sodium sulfate Vapors from spin bath evaporator Spinning bath drippings Storage-reclaimed spinning bath liquor Pickling solution Brass and copper-sulfuric acid + 5% cupric sulfate "Mils per year (= mdd

X

0.127).

116 49

3 16 0.6

70

10

100 107

6

47 47

Mixing tank 1 Crystallizer 5

104

25 20

60 77 121 80 80

6

6

24 6

0.5 14 pits

40 55 49 46

4 5

71

5

5

8 2

Chapter 2

210

Table 59 Classifying Corrosion Behavior of Lead in Different Environments 1611 (See Footnote). (Courtesy of Lead Industries Association, New York.)

Chemical Abietic acid Acetaldehyde Acetaldehyde Acetanilide Acetic acid Acetic acid Acetic anhydride Acetoacetic acid Acetone Acetone cyanohydrin Acetophenetidine Acetophenone Acetotoluidide Acetyl acetone Acetyl chloride Acetyl thiophene Acetylene, dry Acetylene tetrachloride Acridine Acrolein Acrylonitrile Adipic acid Alcohol, ethyl Alcohol, methyl Alkanesulfonic acid Alkyl aryl sulfonates Alkyl naphthalene sulfonic acid Allyl alcohol Allyl chloride Allyl sulfide Aluminum acetate Aluminum chlorate Aluminum chloride Aluminum ethylate Aluminum fluoride Aluminum fluorosulfate Aluminum fluosilicate Aluminum formate Aluminum formate Aluminum hydroxide Aluminum nitrate Aluminum potassium sulfate

Temp. ("C) 24 24 24- 100 24 24 24 24 24 24- IO0 24- 100 24 24- 100 24 24- 100 24 24- 100 24 21 24-52 24-52 24- 100 24- 100 24- 100 24- 100 24 24- 100

93 24 24 24 24- 100 24- 100 24 24- 100 24- 100 24 24- 100 24 100 24- 100 24 24- I00

Concentration Corrosion (%o)

class

D A B A B C A B A B B B B B A B A B B B A A A A D B C B C D A B B B B A B B D B B A

Properties and of Lead

Its Alloys

21 1

Table 59 Continued Concentration Temp. Corrosion ("C) (%)

Chemical Aluminum potassium sulfate Aluminum sodium sulfate Aluminum sulfate Aminoazobenzene Aminobenzene sulfonic acid Aminobenzoic acid Aminophenol Amniosalicyclic acid Ammonia Ammonium acetate Ammonium azide Ammonium bicarbonate Ammonium bifluoride Ammonium bisulfite Ammonium carbamate Ammonium carbonate Ammonium chloride Ammonium citrate Ammonium diphosphate Ammonium fluoride Ammonium fluosilicate Ammonium formate Ammonium hydroxide Ammonium hydroxylamine Ammonium metaphosphate Ammonium nitrate Ammonium oxalate Ammonium persulfate Ammonium phosphate Ammonium picrate Ammonium polysulfide Ammonium sulfamate Ammonium sulfate Ammonium sulfide Ammonium sulfite Ammonium thiocyanate NH,OH Ammonium tungstate Amyl acetate Amyl chloride Amyl laurate Amyl phenol Amyl propionate

+

24- 100 24- 100 24-1 18 24 24- I00 24-93 24- 100 100- 149 24- I00 25 24 24- 100 24 24-52 24- 149 24- 100 24 I00

24- 100 24 24-52

20- 100 10 -

__ -

10-30 3.85 -

10 10 10 0- 10 10

0-20 20

100

10

27 20- 100 24 20-52 24 24- 100

3.5-40 34

66

24- 100 24- 100 24- 100 24 24- 100 24- 100 24 24 24 24 24- 100 200 24- 100

10 10-30 10-30 10-30 -

10 10 10 -

10

10-40 -

IO 80- 100 -

class

B B A C B B B C B B B B B A A B B D B B B C A B B D D B A B B B B C B A D B D B D B

Chapter 2

212

Table 59 Continued Chemical Aniline Aniline hydrochloride Aniline sulfate Aniline sulfite Anthracene Anthraquinone Anthraquinone sulfonic acid Antimony chloride Antimony pentachloride Antimony sulfate Antimony trifluoride Arabic acid Arachidic acid Arsenic acid Arsenic trichloride Arsenic trioxide Ascorbic acid Azobenzene Barium carbonate Barium chlorate Barium chloride Barium cyanide Barium hydroxide Barium nitrate Barium peroxide Barium polysulfide Barium sulfate Barium sulfide Benzaldehyde Benzaldehyde sulfonic acid Benzamide Benzanthrone Benzene Benzene hexachloride Benzene sulfonic acid Benzene sulfonic acid Benzidine Benzidine disulfonic acid 2.2 Benzidine 3 sulfonic acid Benzilic acid Benzobenzoic acid Benzocathecol

Concentration Temp. Corrosion ("C) (%l

20 24 24- 100 24- 100 24- 100 24- 100 24- 100 24 24- 100 100

24- 100 24- 100 24 24 100-149 24- I O 0

24 24- 100 24 24- 100 24- 100 24 24 24- 100 24 100

24- 100 24 24 24- 100 24- 100 24- 100 24 24 24 100

100

24- 100 24-100 24- 100 24- 100 24- 100

class A D B B B B B C B C A B B B B B

D B D B B D D B D D B B D B B B B B B D B B B B B B

Properties of Lead and Its Alloys

213

Table 59 Continued Chemical Benzoic acid Benzol Benzonitrile Benzophenone Benzotrichloride Benzotrifluoride Benzoyl chloride Benzoyl peroxide Benzyl acetate Benzyl alcohol Benzylbutyl phithalate Benzyl cellulose Benzyl chloride Benzyl ethyl aniline Benzylphenol Benzylphenol salicylate Benzylsulfonilic acid Beryllium chloride Beryllium fluoride Beryllium sulfate Boric acid Bornyl acetate Bornyl chloride Bomyl formate Boron trichloride Boron trifluoride Bromic acid Bromine Bromobenzene Bromoform Butane Butanediols Butyl acetate Butyl benzoate Butyl butyrate Butyl glycolate Butyl mercaptan Butyl oxalate Butyl phenols Butyl phthalates Butyl stearate Butyl urethane

Concentration Temp.Corrosion W) ("C)

24 24 24- 100 24- 100 24- 100 24- 100 100

24242424242424242424-

l00 100 100 100 100 100 100

I00 100 100 100 24- 100 24- I00

24- 149 24- 100 24- 100 24- 100 24- 100 24-204 24- 100 24 24- 100 24- 100 24 24 24 24- 100 24- 100 24- 100 24 24 24 24- 100 24- 100 24- 100

class

D A A A B B C B B B B B B B B B B D B B B B B B B A B B B B A B B B B B C B C B B B

Chapter 2

214

Table 59 Continued Concentration Temp.Corrosion ("C) (%)

Chemical Butyric acid Butyric aldehydes Butyrolactone Cadmium cyanide Cadmium sulfate Calcium acetate Calcium acid phosphate Calcium benzoate Calcium bicarbonate Calcium bisulfite Calcium bromide Calcium carbonate Calcium chlorate Calcium chloride Calcium chromate Calcium dihydrogen sulfite Calcium disulfide Calcium fluoride Calcium gluconate Calcium hydroxide Calcium lactate Calcium nitrate Calcium oxalate Calcium phosphate Calcium pyridine sulfonate Calcium stearate Calcium sulfaminate Calcium sulfate Calcium sulfide Calcium sulfite Camphene Camphor Camphor sulfonic acid Capric acid Caprolactone Capronaldehyde Capronaldehyde Cabozole Carbitol Carbon disulfide Carbon fluoride Carbon tetrabromide

+ SOz

24 24- I O 0 24- 100 24 24- 100 24 24 24- 100 24 24 24- 100 24 24 24 24- 100 24 24 24- 100 24- 100 24 IO0

24 24- 100

+ H?SOJ

IO-l00 10-30

10-30

20

A

10-30 -

-

30

20

IO S IO 10 IO IO 10

24 24- 100 24- 100 24- 100

20

100

100

24 24- 100 24- 100 24 52- 100 24- 100 24- 100 24- 100 24- 100 100

D B B D A B B B C B B D B

20

100

24- 100 24- IO 0

class

IO IO IO 20- 100

-

-

-

B A

B B B

D B D B B A B A B C B B A C B B A B B B A

B C

Properties and of Lead

Its Alloys

215

Table 59 Continued Chemical Carbon tetrachloride (dry) Carbonic acid Carnallite Carotene Cellosolves Cellulose acetate Cellulose acetobutyrate Cellulose nitrate Cellulose tripropionate Cerium fluoride Cesium sulfate Cesium chloride Cesium hydroxide Cetyl alcohol Cetyl alcohol Chloroacetic acid Chloral Chloramine Chloranil Chloranthraquinone Chlordane Chlorethane sulfonic acid Chloric acid Chlorine Chlorine dioxide Chloroacetaldehyde Chloroacetone Chloroacetyl chloride Chlo-alkyl ethers Chloroanlinobenzoic acid Chloroaniline Chlorobenzene + SO, Chlorobenzotrifluoride Chlorobenzoyl chloride Chlorobromomethane Chlorobromopropane Chlorobutane Chloroethylbenzene Chloroform Chlorohydrine Chloromethonic ester Chloronaphthalenc

Concentration Temp.Corrosion ("C) (%) BP 24 24- 100 24- I00 24- I00 24 24- 100 24- 100 24- I00 24- 100 100

24- 100 24 24 100 24 24- 100 24 24- 100 24- 100 24- 100

class A

D A A A A B B B B C B D

24 38 6 24 24- 100 24 24- 100 24- I00 24- 100

B C B B B B B B C D B B B B B B B B

18

A

24- 100 24- IO0 24 24- 100 24 24- 100 24-BP 24- 100 24- 100 24- 100

B B B B

100

B

B B B B B

Chapter 2

216

Table 59 Continued Temp. ("C)

Chemical Chloronitrobenzene Chlorophenohydroxy acetic acid Chlorophenol Chloroquinine Chlorosilanes Chlorosulfonic acid Chlorosulfonic acid + 50% SO, Chlorotoluene Chlorotoluene sulfonic acid Chlorotoluidine Chlorotrifluro ethylene Chloroxylenols Chloroxylols Cholesterol Chromic acid Chromic chloride Chromic fluoride Chromic hydroxide Chromic phosphate Chromic sulfate Chromium potassium sulfate Chromium sulfate (basic) Chromyl chlorides Citric acid Citric acid Cobalt sulfate Copper chloride Copper sulfate M-cresol + 10%water M-cresol 10% water 0-cresol + 10%water 0-cresol + 10%water Cresote Cresylic acid Cresylic acid Crotonaldehyde Crotonic acid Cumaldehyde Cumene Cumene hydroperoxide Cyanamide Cyanoacetic acid

+

24- 100 24- 100 24 24 24- 100 24 19

24- 100 24 24- 100 24- 100 24 24- I O 0 24- 100 24 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24-79 24 24 24 24- 100 25

Concentration Corrosion W)

class

-

B B C C B C C B C B B C B B B B B B B B B B B B D B D B B D B D D D B B D B B D B D

-

-

40 -

-

IO 10

20-50 -

10-30 50- l00 10-30

10-40 10-70 Liquid

BP

Vapor

25

Liquid Vapor 90 90

BP

24 24 24 24- 100 24 24- 100 24- 100 24 24- 100 24

100 -

__

-

217

Properties of Lead and Its Alloys

Table 59 Continued Chemical Cyanogen gas Cyclohexane Cyclohexanol Cyclohexanol esters Cyclohexanone Cyclohexene Cyclohexy lamine Cyclopentane DDT Dialkyl sulfates Dibenzyl Dibutyl phthalate Dibutyl thioglycolate Dibutyl thiourea Dichlorobenzene Dichlorodifluro-methane (Freon- 12) Dichlorodiphenyldichloroethane (DDD) Dichloroethy lene Diethanolamine Diethyl ether Diethylamine Diethy laniline Diethylene glycol Difluoroethane Diglycolic acid

Dihydroxydiphenylsulfone Diisobutyl Dimethyl ether Dioxane Diphenyl Diphenyl chloride Dipheny lamine Diphenylene oxide Dipheny lpropane Epichlorohy drin Ethane Ether Ethyl acetate Ethyl benzene Ethyl butyrate Ethyl cellulose Ethyl chloride

Temp. ("C)

24 24 24 24- 100 24 24- 100 24 24- 100 24 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24 24 24 24- 100 24-52 24- 100 24 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24- 100 24 24-100 24 24-19 24- 100 24- 100 24- 100 24- 100

Concentration (700)

Corrosion class

D B B B B B D B B B B

B B B B A B A B B D B

I? B D

B B B B

B B A B B A A

B B B B B B

Chapter 2

218 Table 59

Continued

Chemical Ethyl ether Ethyl formate Ethyl lactate Ethyl mercaptan Ethyl stearate Ethyl sulfonic acid Ethyl sulfonic acid Ethylene Ethylene bromide Ethylene chlorohydrin Ethylene chlorohydrin Ethylene cyanohydrin Ethylene cyanohydrin Ethylene dibromide Ethylene dichloride Ethylene glycol Ethylene oxide 2-Ethylhexoic acid Ferric ammonium sulfate Ferric chloride Ferric ferrocyanide Ferric sulfate Ferrous ammonium sulfate Ferrous chloride Ferrous sulfate Fluoboric acid Fluocarboxylic acid Fluorine Fluosilicic acid Formaldehyde Formamime Formic acid Furfural Gluconic acid Glutamic acid Glycerol Glycerophosphoric acid Glycol monoether Glycolic acid Glycolic acid Heptachlorobutene Heptane

Concentration Temp.Corrosion (TOO) (“C)

24- 100

-

100 24- I O 0 100 24- 100

-

24

-

100 24- 100 100

-

24 52- 100 24 52- l00 24 24- 100 -

24 71 24- 100 24 66-93 24-79 24 24 24- I O 0 24 24 24- I O 0 45 24-52 24- 100 24- 100 24- 100 24 24 24 24 24- 100 24 100

24 24- 100

-

-

-

90 100 100

90

class

B C B D B B C A B A

B A B D

-

B B B C A D A A B C B C D A D B B D B B D B B B B D B

-

A

-

50 -

96 10-20 20-30 -

10-20 10 10-30 IO 30 -

10 20- 100 -

IO-l00 -

10-100 -

10-100 10

219

Properties of Lead and Its Alloys Table 59 Continued Chemical Hexachlorobutadiene Hexachlorobutene Hexachloroethane Hexamethylene tetramine Hydrazine Hydriodic acid Hydrobromic acid Hydrochloric acid (see Table IO) Hydrofluoric acid Hydrogen bromide (Anh HBr) Hydrogen chloride (Anh HCI) Hydrogen peroxide Hydrogen sulfide Hydroquinine Hydroxyacetic acid Hypochlorous acid Iodine Iodoform Isobutyl chloride Isobutyl phosphate Isopropanol Lactic acid Lead acetate Lead arsenate Lead azide Lead chloride Lead chromate Lead dioxide Lead nitrate Lead oxide Lead peroxide Lead sulfate Lithium chloride Lithium hydroxide Lithium hypochlorite Lithopone Magnesium carbonate Magnesium chloride Magnesium chloride Magnesium hydroxide Magnesium sulfate Magnesium anhydride

Concentration Temp. Corrosion ("C) (%)

24- 100 24 24- 100 24- 100 24 24 24 24 24 100

24 24 24 24- IO0 24 24 24 24- I O 0 24 24 24 24 24 24- 100 24- 100 24- 100 24- I00 24- IO0 24- 100 24- IO0 24- I00 24- IO0 24- I O 0 24 24-79 24 24 24 24 24 24- 100 27

-

10-40 20- 100 10-50

10-70 0- 10

2-10 -

100 10-30 90- 100 10 -

-

IO -

-

IO-l00 10-30 -

-

10 -

10 -

IO 0- 10

IO-IO0 10-30 10-60 IO

class A B B B D D D C B D A D B B A

D D B B B A D D B B B B B B B B B B

D A A D C D D B C

Chapter 2

220

Table 59 Continued Chemical Malic acid Mercuric chloride Mercuric sulfate Mercurous nitrate Mercury Methanol Methyl ethyl ketone Methyl isobutyl ketone Methylene chloride Monochloroacetic acid Monochlorobenzene Monoethanolamine Naphthalene Naphthalene sulfonic acid + HZSO, Nickel ammonium sulfate Nickel nitrate Nickel sulfate Nitric acid (see Table 5 ) Nitrobenzene Nitrocellulose Nitrochlorobenzene Nitroglycerine Nitrophenol Nitrosyl chloride Nitrosylsulfuric acid Nitrotoluene Nitrous acid Oleic acid Oxalic acid Oxalicacid + 1.5-3% H2S0, Pentachloroethane Perchloroethylene Persulfuric acid Phenol Phenolsulfonic acid Phenyl isocyanate Phosgene Phosphoric acid Phosphorous acid Phosphorous chloride Phosphorous oxychloride Phosphorous pentachloride

Concentration Temp.Corrosion ("C) (%) 100

24 24- 100 24 24 30 24- 100 24- 100 24- 100 24 24 171

24 88

24- 100 24- 100 24- 100 24-52 24 24 24 24 24 24-79 24 24 24 24 S2 79 24 100

24 24- 100 24 24- 100 24-93 27 24- 149 24 24

class

B C B D D B B B B D D C B B B B B B A

D C D B B B D D D A

B B C B B B B B A

B B A

Properties Its and of Lead

Alloys

22 1

Table 59 Continued ~~

Chemical Phosphorous pentachloride Phosphorous tribromine Phosphorous trichlorine (dry) Phthalic anhydride Picric acid Potassium aluminum sulfate Potassium bicarbonate Potassium bifluoride Potassium bisulfate Potassium bisulfite Potassium bromide Potassium carbonate Potassium chlorate Potassium chlorate Potassium chloride Potassium chromate Potassium cyanide Potassium dicromate Potassium ferricyanide Potassium fluoride Potassium hydroxide Potassium hypochlorite Potassium iodate Potassium iodide Potassium metabisulfite Potassium nitrate Potassium permanganate Potassium peroxide Potassium persulfate Potassium sulfate Potassium sulfite Propionic acid Pyridine Pyridine sulfate Pyridine sulfonic acid Pyrogallic acid Quinine Quinine bisulfate Quinine tartrate Quinizarin Quinoline Quinone

Temp. ("C)

Concentration Corrosion class -

52- l49 24 24 82 20 26 24 24-79 24- 100 24- 100 24- 100 24 24

10 10

B B

10-20 10-50 10-50

C

100

10

8 24- 100 24 24- 100 24- 100 24-79 24-60 24 24-BP 24 79 8

24 24 24 24- 100 24 24 24- 100 24 24 24 24- 100 24- l00 24- 100 24- 100 24- 100 24- 100

B A

5.25 25

B B C

-

A

10-30

D

10

10

0.25-8.0 10-40 10-30

10-60 10-60 20 0-50 10 2- I O 30 10-30

0.5- 10 10-40 IO 10

10-20

B C B D B B D B

B B B B B D

B B C D D B

10

B

10-70 IO IO

D

20

A

-

IO -

IO

B B B B B B

B B B

222

Chapter 2

Table 59 Continued Chemical Saccharin solutions Salicylic acid Selenious acid + H,SO, + HNO, Silver nitrate Sodium acetate Sodium acid fluoride Sodium aluminate Sodium bicarbonate Sodium bifluoride Sodium bisulfate Sodium bisulfite Sodium carbonate Sodium carbonate Sodium chloride Sodium chlorite Sodium chromate Sodium cyanide Sodium hydrogen fluoride Sodium hydrosulfite Sodium hydroxide Sodium hypochlorite Sodium hyposulfite Sodium nitrate Sodium nitrite Sodium perborate Sodium percarbonate Sodium peroxide Sodium persulfate Sodium phosphate Sodium phosphate (tri-basic) Sodium silicate Sodium sulfate Sodium sulfide Sodium sulfite Sodium tartarate Stannic chloride Stannic tetrachloride (dry) Stannous bisulfate Stannous chloride Succinic acid Sulfamic acid Sulfur dioxide

Concentration Temp. Corrosion (%) ("C)

24- 100 24- 100 93 24 25 24 24 24 24 24- 100 24- 100 24 52 25 24 24- 100 24 71

24 26 24 24 24 24- I00

24 24 24 24 24- 100 24 24 24 24- 100 24- 100 24 24 24 24- 100 24 24- 100 22 24-204

class

-

B B

-

A

10-60 4 10

IO IO -

10-30 10 10

20 0.5-24 IO 10 IO 8

10-20

D B B D B B B B B D A

B B B B A

-

B C B D B D D D B B D B

2-20 10-30

A A

10-30

B D D B B D B B B

0-30 1 10 10 10-60 IO -

IO IO 10-100

10-20

-

20 100 10 10-50

10-50

3-20 90

Properties of Lead and Its Alloys

223

Table 59 Continued Concentration Temp. Corrosion ("C) (%)

Chemical Sulfur trioxide Sulfuric acid (see Figure 4) Sulfurous acid Sulfuryl chloride Tanning mixtures Tannic acid Tartaric acid Tetraphosphoric acid Thionyl chloride Thiophosphoryl chloride Tetrachloroethane Titanium sulfate Titanium tetrachloride Toluene Toluene-sulfochloride Thrichloroethylene Thrichloronitromethane Triethanolamine Triphenyl phosphite Turpentine Vinyl chloride Zinc carbonate Zinc fluosilicate Zinc hydrosullite Zinc sulfate Zinc chloride

24

90

60 24 21 24 100 2024 30-70 24 10-100 24- 149 24 63 24- I00 10-30 24 24- 100 24 27 24 60 0.4 27 24 24 10 24 21 30-36 24

35

79

-

25

class

B A

B B D B D B B A

B B A A

B C B A B D B D B B B

Notc,: Data mostly correspond t o chemical lead. The corrosion rates of different grades of lead In contact with the same chemical a l l normnlly fall within the same category. Thereforc, no mention is made of any variatlon ~n the corrosion rate for other grades of lead. The four corrosmn pcrfonnnncc categorles are a s follows:

A < 2 mils/year; negligible corrosion; lead recommended for use. B < 2O/mpy; practically resistant; lead recommended for use. C is 20-SO mpy. Lend may be used where this effect on service lifc can he tolerated. D > SO mpy. Corrosion rate too hlgh t o merlt any consideration of lead. The absence

01 concentrat~on

data IS indicated by a dash.

224

Chapter 2

Table 60 Corrosion of Lead in Various Natural Outdoor Atmospheres [61]. (Courtesy of Lead Industries Association, New York.)

Location Altoona, Pennsylvania New York Sandy Hook, New Jersey Key West, Florida La Jolla, California State College, Pennsylvania Phoenix, Arizona Kure Beach, North Carolina, 80 ft. side Newark, New Jersey Point Reyes, California State College, Pennsylvania Birmingham, England Wakefield, England Southport, England Bourneville, England Cardington, England Cristobal, C Z Miraflores, C Z

Type of atmosphere

Material

Industrial Industrial Industrial Industrial Seacoast Seacoast Seacoast Seacoast Seacoast Seacoast Rural Rural Semiarid Semiarid East coast, marine East coast, marine Industrial Industrial West coast, marine West coast, marine Rural Rural Urban Urban Industrial Marine Suburban Rural Tropical, marine Tropical, marine

Chem Pb 1% Sb-Pb Chem Pb 1% Sb-Pb Chem Pb 1% Sb-Pb Chem Pb 1% Sb-Pb Chem Pb 1% Sb-Pb Chem Pb I % Sb-Pb Chem Pb 1% Sb-Pb Chem Pb 6% Sb-Pb Chem Pb 6% Sb-Pb Chem Pb 6% Sb-Pb Chem Pb 6% Sb-Pb 99.96% Pb 1.6% Sb-Pb 99.995% Pb 99.995% Pb 99.995% Pb 99.995% Pb Chem Pb Chem Pb

"mdd = milligrams/square decimeters/day. hmpy = mils per year.

Duration (years) 10

10 20 20 20 20 10 10

20 20 20 20 20 20 2 2 2 2 2 2 2 2 7 7 1 I 1 1

8 8

Corrosion Rate mdd

mpyb

0.23 0.18 0.12 0.10 0.17 0.16 0.18 0.17 0.16 0.18 0.10 0.11 0.03 0.09 0.4 1 0.32 0.46 0.33 0.28 0.20 0.43 0.3 1 0.29 0.03 0.58 0.55 0.61 0.44 0.42 0.24

0.029 0.023 0.0 15 0.013 0.02 1 0.020 0.023 0.022 0.02 1 0.023 0.013 0.014 0.004 0.012 0.052 0.041 0.058 0.042 0.036 0.026 0.055 0.039 0.037 0.004 0.074 0.070 0.077 0.056 0.053 0.030

Propertiesof Lead and Its Alloys

225

E. Corrosion of Lead in Water Distilled water free of oxygen and carbon dioxide does notattack lead. Pure water containing carbon dioxide butnot oxygen also has little effect on lead. However, when lead comes into contact with pure water through which air free of carbon dioxide is being bubbled, it quickly oxidizes to form a film of white lead hydroxide. This film is nonadherent and allows the attack on the lead to continue. Because the lead hydroxide is low in solubility, it settles out. This is one case in which even though the corrosion product is insoluble, its nonadherent characteristic fails to prevent lead corrosion. A yellow crystalline lead oxide forms on the lead surface at or near the waterline. In pure or distilled water containing both oxygen and carbon dioxide, a basic lead carbonate film forms at ahigherratio of carbondioxide to dissolved oxygen, protecting the lead from further attack. However, once a certain ratio of CO, to 0, is reached, further increases in the carbon dioxide level cause the insoluble lead carbonate film to convert to soluble lead biattack carbonate.When this occurs, the film dissolvesandcorrosive commences. Thus, the corrosion behavior of lead in water containing carbon dioxide and oxygendependson the concentration of the former gas. This dependency, which causes many reactions to take place in a narrow range of concentration, explains the contradictory nature of much of the corrosion data reported in the literature. The influence of carbondioxidealsoshowswhy lead steam coils which handle pure water condensate are not severely corroded. In the case where all the condensate is returned to the boiler and negligible makeup is used, there is an absence of oxygen and often of carbon dioxide. Sometimes, there is some carbon dioxide present. This is from the breakdown of carbonates and bicarbonates in the boiler water. In either case, lead will not significantly corrode. If a substantial amount of condensate is discarded and fresh water is continually fed to the boiler, corrosion of lead can occur. This is usuallyprevented by keeping the oxygen level low by addingoxygen scavengers, such as sodium sulfite or hydrazine, to the makeup water. In the case of dimineralized water, corrosion rates are very low for chemical lead and Pb-6% Sb and Pb-2% Sn alloys (Table 61) [61]. Most natural waters contain silicates, sulfates, and carbonates which can form lead-salt surface films stifling further attack. In general, the corrosion rate will dependon the hardness of the water. Naturalwaters of moderate hardness (i.e., greater than 125 ppm as calcium carbonate) form adequate protective films on the lead; thus, attack is negligible. The presence of salts, such as silicates, increases the hardness and the protective nature of the film. In contrast, nitrates interfere with the formation of the protective film, causing increased corrosion.

Chapter 2

226

Table 61 Corrosion of Lead in DemineralizedWater 1611. (Courtesy of Lead Industries Association, New York.)

Lead Chemical (ASTM) 6% Antimonial lead 2% tin-lead

mpy"

mdd"

2.3 0.2 0.6

18 I .6

4.8

"Mils per year. "Milligrams/square decimeter/day.

In soft aerated waters, the corrosion rate depends both on the hardness level of the waterand its oxygen content. The corrosivity of soft waters with a hardness level of less than 125 ppm depends on the same factors that govern the action of distilled water. This often eliminates lead as a material that can be used in piping or containers for handling potable waters, in which no more than 0.10 ppm (see Chapter 5 ) of lead is permissible. This issue of contamination also affects the use of lead even in situations where, from a service point of view, the corrosion rate is negligible. Other waters corrosive to lead include those containing enough carbonic acid to convert calcium carbonate deposits into soluble calcium bicarbonate. The presence of organic acids whose lead salts are soluble also promotes corrosion. Conversely, film-forming lime or sodiumsilicate can be added to the water to lower the corrosion rate. The corrosion rates of lead in some industrial and domestic waters are shown in Table 62 [61]. It shouldbenoted that in all cases, even where hardness was below 125 ppm, the corrosion rate is relatively low. A corrosion rate forfreshwater is alsoincludedamong the data for seawater in Table 63 [61]. The maincomponentdissolved in seawater is sodiumchloride,but there are also several other major constituents and at least a trace of almost all of the elements. The proportions of the major constituents in ocean water are quite uniform, and their total concentration influences many properties of the water. This total concentration, called the salinity, is defined as the to total amount of solid materialwhen all carbonatehasbeenconverted oxide, the bromine and iodine replaced by chlorine, and organic matter completely oxidized. The salinity of natural seawaters varies between 33 and 37 parts per thousand, with the average being approximately 35. This is equivalent to a salt content of about 3.4%. Coastal waters and tide-swept harbors may have lower salinity. In enclosed seas, the level depends on the relative rates of evaporation and land drainage.

Properties andof Lead

Its Alloys

227

Table 62 Corrosion Rates of Lead in Some Industrial and Domestic Waters 1611. (Courtesy of Lead Industries Association, New York.)

Type of water Condensed stream, traces of acid Mine water, pH 8.3, 110 ppm hardness Mine water, 160 ppm hardness Mine water, 1 I O ppm hardness Cooling tower, oxygenated Lake Erie water Los Angeles aqueduct water, treated by chlorination and copper sulfate Spray cooling water, chromate treated 16

Corrosion rate"

Temp. ("C)

Aeration Agitation mdd

21-38 20

None Yes

Slow Slow

6.75 0.26 2.08

0.85

19 22 16-29

Yes Yes Complete

Slow Slow None

2.2 1.98 41.7

0.28 0.25 5.3

Ambient

-

0.5 ft/s

0.38 2.95

Yes

mpy

-

2.9

0.37

"Total immersion.

Table 63 Corrosion Rate of Lead in Natural Waters 1611. (Courtesy of Lead Industries Association, New York.) Corrosion rate Location type and

of water

Type of Agitation test mdd

mpy

about Immersion Bristol seawater Channel, Southampton, seawater docks,

CZ, Lake, Gatun tropicalImmersion water fresh Fort Amador, CZ, tropical Pacific Ocean San Francisco Harbor, seawater Port Hueneme Harbor, California, seawater Beach, Kure seawater "150 mm/s. "60 mm/s.

3.9 93% of time 0.1At0.86 half tide level Immersion Mean tide level Mean tide level Immersion

0.50 1

Still 0.5 ft/s flow" 0.5 ft/s flow" Flowing 0.2 ft/s flowh

0.66 2.7 1.6 3.31 1.7

0.08 0.36 0.20 0.42 0.22

228

Chapter 2

The corrosion of lead in seawater is relatively slight and may be retarded by incrustations of lead salts. Data that represent the performance of lead in seawater at several locations are given in Table 63 [61]. This table shows that at the same tropical location, lead corrodes in freshwater at about one-fourth the rate it does in ocean water. The factors that can affect the corrosiveness of ocean harbor waters are salt content, pollution, rate of flow, wave action, sand or silt content, temperature, and marine growth.

F. Corrosion of Lead in Soil Lead is used extensively in the form of sheathing for power and communications cables because of its impermeability to water, ease of forming, and its excellent resistance to corrosion in a wide variety of soil conditions. The incidence of corrosion failure of lead-sheathed cables is low in relation to the total mileage of cables in undergroundservice.Lead is also usedin nuclear-waste burial in underground repositories. Serious corrosion of lead in the underground is an exception rather than the rule. Cables are either installed in ducts or buried directly in the ground. IntheUnited States, the preferred method is to put the cable in ducts or conduits made of materials such as cement, vitrified clay, wood, and so forth. Theenvironmental factors generallyhavea greater effect onunderground corrosionthan differences in leadcomposition,and there is a significant difference in the environments of lead buried in ducts and directly in soils. The environment within ducts is often quite complex. It can include combinationsofhighlyhumidmanholeandsoilatmospheres,freelime leached from concrete, and alkalis formed by the electrolysis of salts in the water which seeps into ducts. The galvanic coupling, differential aeration, alkalinity, and stray currents are major factors that influence the corrosion of lead sheaths in ducts. When the surface of the lead is scratched, exposing bright, activemetal, the freshmetalsurface will be the anodeand will corrode. The amount of air able to penetrate the silt and reach the crevice where the cable sheath and duct meet is less than the amount available at the upper surface of thecable sheath. Such differential aerationconditionsleadto corrosion of the lead sheath. Cable sheaths installed in continuous concrete or asbestos cement ducts in concrete tunnels under waterways could sometimesbe exposed to alkaline water (pH 10.9-12.2) containing mainly calcium hydroxide and sometimes sodium hydroxide. The source of the calcium hydroxide is traced to incompletely cured concrete. Electrolysis of solutions of deicingsalts that had seeped into the tunnels could be a source of sodium hydroxide. The buildup in concentration can occur if seepage water is not drained.

Properties Its andof Lead

Alloys

229

Stray currents can cause serious corrosion of lead pipe or lead cable sheathing.Sources of stray currentsincludeelectricrailwaysystems, grounded electric direct current power, electric welders, cathodic protection systems and electroplating plants. Alternating currents are much less damaging than direct currents. Corrosion is at a minimum when the sheath potential is cathodic to the ground. Other factors that can initiate corrosion of lead sheaths include contact with acetic acid in wood ducts, microorganisms, and corroded steel tapearmor. Bacterial corrosionusuallyoccursunder poorly aerated conditions in the presence of mud, water, and organic matter. Bacteria capable of reducing sulfate to sulfides are the principal cause of the attack on lead. Microbial decomposition of the hydrocarbons present in cable coatings may also produce organic acids corrosive to lead. Corrosion of lead by corroded steel tape armor can occur when the oxide-coated steel formed is cathodic to lead. When the lead is buried directly in soil, the extent of corrosion varies widely as the physical and chemical characteristics of the soils differ over a wide range. The physical properties of soils which are of most interest in corrosion are those that influence the permeability of the soil to air and water. This is because good drainage tends to minimize corrosion. Soils with a coarse texture such as sands and gravels permit free circulation of air. The corrosion in such soils is approximately the same as that occurring in the atmosphere. Clay and silt soils are generally characterized by a fine texture and high water-holding capacity, which results in poor aeration and drainage. Numerous chemical compounds are present in soils, but the ones that play an important role in corrosion are those soluble in water. The presence of base-forming elements, such as sodium, potassium, calcium, and magnesium, and the acid-forming groups, such as carbonate, bicarbonate, chloride, nitrate, and sulfate,caninfluence the progress of corrosion, as was discussed earlier. Another factor which directly affects the corrosion of leadsheathed cable is the differences among the soils through which the cable passes. Corrosion can be caused by soils which differ in ionic content, moisture level, and degree of aeration. These differences can set up anodic and cathodic areas separated by large distances. Tables 64 and 65 present the corrosion data of lead and lead alloys in a variety of soil conditions [61]. The forms of lead used for their corrosionresistant properties are castings, extrusions, androlled products. The castings used for corrosion resistance include filter grids, anodes, valves, pipe fittings and flanges, pumps, and a few types of vessels like evaporators. Some of the lead and lead-alloy extrusions used in applications requiring corrosion resistance are battery anodes, seamless pipe, heating and cooling coils and tubes, cable sheathing and sleeves, and burning bars. The rolled lead sheets may be used as Supported Lead, Bonded Lead, and Brick Lead.

230

Chapter 2

Table 64 Corrosion Data of Lead Alloys in Various Soils after I 1 Years [61]. (Courtesy of Lead Industries Association, New York.) Chemical le a d Type of soil Cecil clay loam Hagerstown loam Lake Charles clay Muck Carlisle muck Rifle peat Sharkey clay Susquehanna clay Tidal marsh Docas clay Chino silt loam Mohave tine gravelly clay Clinders Merced silt loam

Corrosion rate (mPY)

Max pit depth (mils)

18 31

0.3 0.3 0.2

100

52 20 33 70 34 12 25

0.3

1s

24

0.3

85

24

~

~

-

~~~

Tellurium leadh

Hagerstown loam Lake Charles clay Muck Carlisle muck Rifle peat Sharkey clay Susquehanna clay Tidal marsh Docas clay Chino silt loam Mohave fine gravelly clay Clinders Cecil clay loam Merced silt loam

Corrosion rate (mPY)

Max pit depth (mils)

30 107 53 21 23 73 40 8

0.4 0.3 0.2

0.3

17

20 23 61 16 16

Properties of Lead and Its Alloys

231

Table 64 Continued Antimonial lead' Corrosion Max rate (mPY)

Type of soil 104 Charles clay Lake Muck Carlisle muck Rifle peat 89 Sharkey clay Susquehanna clay Tidal marsh Docas clay Chino silt loam Mohave fine gravelly clay 46 Clinders Merced silt loam Cecil clay loam Hagerstown loam

pit depth (mils)

0.4 0.3

SI

0.1
12 28

0.4 0. I <0.01

14 6

<0.1
19

7 16

0.4 4.1 <0.1 4.1

9 9 16

"Chemical lead: 0.0S6% copper, 0.002% bismuth, 0.001 antimony. "Tellurium lead: ().OX% copper, 0.001% antimony, 0.043% tellurium. 'Antimonial lead: 0.036% copper, 5.3% antimony, 0.016% bismuth.

Table 65 Corrosion Data of' Lead Buried in British Locations for S Years 1611. (Courtesy of Lead Industries Association, New York.) Average metal lose mPY Location Type Benfleet Pitsea Rothamsted Gotham Corby

Maximum Maximum depth depthattack of (mils)

(70of thickness)

16-41 16 18-35 nil" nth

7-17 7 8- IS nil.' nth

of pitting

of'Sheet soil Pipe Sheet Pipe Sheet Pipe

Reclaimed salt marsh London clay Moist, neutral clay Keuperrnarl Clinders

"nil = no pit deeper than 4 mils. "111 = not tested.

0.157 0.018 0.060 0.034 nth

0.084 0.040 0.043 0.023 0.017

18

14 22-30 nil" 20-33

15 13 17-24 nil" 16-26

Chapter 2

232

The corrosion resistance of lead or its alloys depends ontheir chemical composition. As presented in earlier sections, a large number of lead and its alloys exhibit corrosion behavior similar to chemical lead in many environof these alloys in a ments. It is difficult to obtain corrosion data for each wide range of operating conditions. Many applications use chemical lead or copper-bearing lead. The chemical lead contains a small amount of copper, which improves corrosion resistance and has a higher mechanical strength. An even smaller silver content further improves the corrosion resistance in some applications. These facts account for the frequent use of chemical lead for corrosion-resistant applications. Copper-bearing lead has a composition similar to chemical lead, but the levels of Ag and Bi are lower. Alloying additions to lead may be required to obtain additional mechanical strength, hardness, or resistance to creep of the part. An alloying addition may also improve the corrosion resistance of the material. Increasing the creep resistancemayalsobeameans for increasing the corrosionbehaviorsimply because the surface of the lead alloy will not be exposed rapidly to the corrodingmedium.Thealloys of lead mostoften selected forcorrosion resistance contain one or more of the elements antimony, silver, tin, calcium, and copper. Lead-antimony alloys have high corrosion resistance in most environments and they form a protective, impermeable film even faster than pure leadand, in somecases,even faster thanchemical lead. At some of the current densities used in metal-plating processes, a 6% antimonial lead anode has excellent corrosion resistance. The major advantages of antimony alloys overchemicalandacid-copperlead are greater hardnessand strength at temperatures below 120°C, the ability to be metallurgically joined to steel, and greater fluidity.

VI.

ACOUSTIC PROPERTIES OF LEAD AND LEAD COMPOSITES

Lead and lead-alloy sheets and composites have been used as a barrier to acoustic noise. Acousticnoise is unwantedsound.Acousticnoise in the environment that arises from automobiles, ships, aircraft, machinery, sound systems, home appliances, and other sources is often discomforting to human beings. Sound is the sensation produced through the stimulation of the ear and brain resulting from variations in sound pressure. It consists of alternate compression and rarification superposed on constant atmospheric pressure. Sound levels are usually measured on a scale that corresponds to the way the ear responds to loudness. Sound levels are measured in units of decibel, given by

Properties Its andof Lead

Alloys

233

N = log(I/[,)) Bels

(27)

where I is the intensity of sound, I,, is the intensity level that the human ear N is the sound level in units of Bel [245,246].A canbarelysense,and decibel is one-tenth of Bel. The intensity is proportional to square of sound is 2 X lo-’ pressure, p , and the lowest pressure the human ear can sense Pa. In units of decibels (dB), the sound level is expressed as

Table 66 lists the sound levels fromcommonnoisesources[246]. loss. AlExtended exposure to high decibels of sound can lead to hearing lowable noise exposure levels by Occupational Safety and Health Administration (OSHA) standards are shown in Table 67 [246]. The response of the human ear to sound depends alsoon the frequency. The human ear responds to frequencies in the range of 20-20,000 Hz. The voice range is 500-2000 Hz. Most of the sounds we encounter are in the range of 125-4000 Hz. Architectural acoustic test standards cover test frequencies in this range [246]. Noise levels may be reduced by absorption or by transmission loss in a material that can insulate the source of noise. In absorption, large areas of the exposed surface area are treated with absorbent materials. In transmission, a barrier is placed between the source of noise and the area that needs to be quieter. This barrier is made of materialwhichefficientlyconverts sound into heat. For frequencies in the upper portion of the range audible to humans, felts of glass fibers provide a very good reductionof sound levels by both absorption and transmission loss. At the lower frequencies, however,

Table 66 Sound Levels of Common Sounds [246]. (Reprintedwithpermission from McGraw Hill Companies, New York.) Sound Sound level (dB)

Apparent loudness

Relative loudness (psi)

Deafening Very loud Loud Moderate Faint Veryfaint

128

130

32 2

I IO

‘12

‘/x

0

70

50 30 10

pressure sounds Common

0.01 0.001 0.00001 0.000001 0.0000001 0.00000001

Threshold of pain, jet plane taking off Thunder, artillery, nearby riveter Noisy oftice, street noise, radio, TV Average home/oftice Quiet home/oftice Rustle of leaves, whisper, threshold of hearing

234

Chapter 2

Table 67

OSHA Limits on Allowable Sound Levels 12461. (Reprinted with permission from McCraw Hill Companies, New York.) Noise level (dB)

exposure Allowable

85 (audiometric required) testing

90 92 95 100 102 105 106 I20

(h) 8 8 6 4

2 1.S 1

0.5 <0.0 17

good results are achieved only by the use of heavy and low bending stiffness materials. Lead satisfies all the criteria for satisfactory insulation performance (i.e., high density, fairly high internal damping,and low bending stiffness). Lead metal in sheet form has been used as the heavy and low bending stiffness layer with remarkable success for many years. However, lead canonly be made economically at areal densities of onepoundper square foot and more, and this weight is excessive for many applications. Hazards to human health and the creep under load require a great deal of effort andexpense.However,composites of lead andotherlightweight sound-absorbingmaterialovercomethesedrawbacksandmake their use economicallyvery attractive [247-2501.Table 68 lists some typical leadbased noise-control materials [250]. The use of lead and lead-based composite laminates are of interest, is at apremium. particularly whenspacecoupledwithhighperformance The International LeadZincResearchOrganizationhad in the past commissioned a number of studies of the performance of lead and lead-based composites in such situations at University of Salford (U.K.) and Manville Service Corporation, R & D Center (Denver, CO) [247-2491. A brief background of airborne sound insulation followed by a summary of acoustic data for lead and lead-based laminates from these studies is now presented.

A.

AirborneSoundInsulation

Airbornenoise is produced by sources that radiate directly into air. The primary path of sound from a source to a receiver is air. The airborne noise

Properties andof Lead

Its Alloys

235

Table 68 Typical Lead-Based Noise-Control Materials 12501. (Courtesy ofLead Industries Association, New York.) Material

Description

1 to 4 ranges from Ibs/ft’ substrates Lead/foam One of more f-1 -1b lead composites sandwiched sheets between layers of polyurethane foam Leaded plastic sheetsLead-loadedsheet ofvinyl or neoprene with or without fabric reinforcement or Damping tile Lead-loaded epoxy tiles urethane Casting compounds Lead-loaded epoxy and Potting or urethane Troweling Lead-loaded and Damping epoxy and enclosures, damping urethane surfaces

Sheet lead Weight

Uses Alone or laminated with various Sound-control enclosures

As a curtain barrier to

line enclosures Damping heavy machinery tilling

resonating

transmission can be reduced using partition walls and floor structures to a level that is acceptable. Two parameters of importance in the sound insulation of a partition are the mass of the partition and the frequency of sound. The higher the mass of the partition per unit, the greater the reduction in sound or sound reduction index. The sound reduction index also increases with the frequency of the incident sound waves. The combined effects of mass and frequency for a single-layer partition are given by the mass law, which relates the sound reduction R to o and M [247]: R = 20 log

(E)

- 6 dB

where pc is the characteristic acoustic impedance of air (414 kglm’ S), o = 27rf,j’ is the frequency of sound (Hz), and M is the superficial mass (kg/m2). Figure 92 shows the dependence of sound reduction R on the product Mj’ [2471. The mass law is a theoretical prediction based on the assumption that the partition is heavy and has low stiffness. It is valid in the intermediate frequency range where R is mass controlled (Figure 93) [247]. The sound reduction versus frequency curve for a common building material consists of three regions. In region 1, the partition behaves like a rectangular thin plate supported, but not clamped, in a frame. This panel can resonate in a

236

Chapter 2

Figure92 Dependence of sound reduction on surface density and frequency [247]. (Courtesy of ILZRO and Dr. G. Keny and P. Lord, Univ. of Salford, UK.)

Region 1

Region 2

Region 3 0

--

/Stilfness controlled

Resonance:

f

critical frequency

Figure 93 Practical sound reduction versus frequency 12471. (Courtesy of ILZRO and Dr. G. Keny and P. Lord, Univ. of Salford, UK.)

Properties andof Lead

Its Alloys

237

numberofmodes.Below the lowestresonancefrequency, stiffness alone controls the panel vibration. In region 2, above the first few resonance frequencies,massbecomesimportantand the soundreduction is masscontrolled just as in the mass law. In region 3, eventually a frequency is reached where the bending wavelength A, in the panel equals the radiated wavelength A,, in air. This frequency is called the critical frequency$ [247]:

where c’ is the velocity of sound in air (340 m/s)and stiffness. B is given by

B is the bending

Eh3 B=N.m 12 where E is Young’s modulus for the material (in units of Pascal) and h is the thickness (in meters). The region beyond the critical frequency is called the coincidence region andis the regionwhere the soundwaves in air projectedonto the partition can match the bending waves. To some extent, coincidence is controlled by damping and increasing the latter reduces the “coincidence dip.” Foragiven superficial weight,reducing the bending stiffness raises the critical frequency, and if by increasing the density it is possible to maintain the superficial weight at lower thickness, the bending stiffness is reduced. Table 69 compares the surface densities of common building mate-

Table 69 Acoustic Properties of Different Sound Insulation Materials [247]. (Courtesy of ILZRO and Dr. G. Kerry, Univ. of Salford, UK.) Product of surface

Material

Damping Surface Critical density and frequency density M (kg/m’/m)

Aluminum 34,700 2,700 Brick 1,900-2,300 34,700-58,000 0.002 Glass 38,800 2,500 97,500 Steel 7,700 0.0 Plywood 12,700 S80 Lead 605,000 I 1,000

critical frequency factor at [(kg/m’) X Hz]

1000 Hz 10

0.0 1

I 0.01s

for 10 mm thickness

1,285 I,826-2,548 2,190 5.500

Chapter 2

238

rials per unit thickness, the internal damping factors, the product of surface densityand critical frequency,and the critical frequency for a variety of materials of 10 mm thickness [247]. A 10-mm-thick sheet of lead has a critical frequency over four times that of either steel or aluminum and over twice that of the brick. Its damping is also relatively high. The sound-reduction index can be increased by using a material whose density is sufficiently large so that a high superficial weight can be realized without increasing the thickness of the partition to the point where the critical frequency falls below 3000 Hz. The use of composites of a lead sheet with plasterboard, poly(viny1 choride) (PVC), and other materials allows the critical frequency to be extended to levels beyond 3000 Hz [251]. The upper frequency limit of practical noise sources likely to cause annoyance in buildings is approximately 3000 Hz. In Figure 94 [247,251],calculated results on composites in the four different configurations for various thicknesses of lead and plasterboard optimized for a critical frequency of 3000 Hz are presented. The surface weight is given by

where p, and p? are the densities of lead and plasterboard of thicknesses h , and h2, respectively. The bending stiffness B, of the composite material depends on both the layer thicknesses and the Young’s moduli of the materials, as well as the way in which they are combined (i.e., whether they are rigidly or elastically connected). B, can be expressed as

B

(33)

where B is the bending stiffness of lead as given by Eq. (31) and E , and E, are the Young’s moduli of lead and plasterboard, respectively. It is seen from the Figure 94 that there is only a small range of variation of thickness of plasterboardpossible in order to maintain = 3000 Hz. The total thickness of the composite panels were all less than 2 cm. The thickness of the lead may be varied from about 0.2 mm up to 6 mm. While maintaining the lead thickness constant, it is possible to increase the overall surface density of the composite panel and, hence, the transmission loss by changing from construction arrangement (a) to (d) of Figure 94. A combination of 1.52 mm leadand12.38 mm plasterboard with a total surface density of 26.68 kg/m’ has an average sound reduction index

239

Properties of Lead and Its Alloys 20

I

I

I

I

:

I

I

I

.

i

:

I

:

i

;

I

1

1

1

10

5 4

3

.., P

c- 2 z

? al m

U

-

c’

L

0 u1 u)

u

E l

x

0 ._

I.-c

Lead-sheet elasticly cemented

I

O.! - 15

0.4 0.:

0.;

0.’

D

2

3

4 5 10 Thickness of plasterboard h, (mm)

,

.,M=20Pa

I

20

30

I

I

40

Figure 94 Thickness dimensions of combined lead panels with a limiting frequency o f f = 3 kHz 1247,2511. (Courtesy of ILZRO.)

240

Chapter 2

of 35.2 dB (see data for partition 6 in Table 71). However, using the same quantity of lead combined with two layers of plasterboard of greater total surface density, it is possible to increase the sound-reduction index without lowering the critical frequency. The combination of lead and plasterboard when used in adouble-leafconstructiondemonstratesits potential when space is at apremium. The soundreduction of such a double-leaf lead/ plasterboard partition with mineral fiber infill is higher than a 225-mm concrete brick wall (Figure 95) [247]. Modern methods of building construction often leave potentially weak acoustic paths around the perimetersof potentially high-performance internal partitions. Such paths occur above suspended ceilings, plenum space, under computer floors, and in perimeter wall heating/cooling ductwork. Sheet lead has been used to effectively “close the gap” between the partition edge and the structural member. The lead sheet is fastened to the underside of the structural soffit and draped over the ceiling above the partition, or fastened under the partition and draped over the structural floor. The edges are sealed, and where provision has to be made for pipework to pass through, the lead

63

125

250

500

Frequency

1000

2000

4000

8000

(Hz)

Figure 95 Sound reduction in a 122-mm-thick double-leaf lead/plasterboard partition(Partition#24) with mineral fiber infill (brokenline)compared with a 225mm concretebrick wall (solid line) [247]. (Courtesy of ILZRO and Dr. G. Kerry and P. Lord, Univ. of Salford, UK.)

Properties andof Lead

Its Alloys

241

has to be fitted and sealed. The advantage of using sheet lead is that it can be readily “worked” in confined areas and will add significant mass without requiring stiffening supports and withoutrigidly connecting the partition, the structural building elements, and supporting structure. The lead-PVC sheet and lead/fiberglass/PVC sheet are alternative materials to sheet lead. Figure 96 illustrates that they have essentially the same acoustic characteristics [247]. The overall performance is dependent on surface mass and can readily be calculated using the “mass law.” A thickness giving an average Sound Reduction Index of between 20 and 25 dB will usually be adequate as a plenum barrier for lightweight partitions of average Sound Reduction Index 30-35 dB because the suspended ceiling will also contribute to the wallperformanceeven if lightweight or porous.Aprogressively heavier material will be required as the performance of the partition is increased. Alternatively, adouble-skinplenum barrier will give much greater insulation. Theuse of an absorbent infillwill improve the

63

125

250

soo

1000

2000

4000

aooo

Frequency (Hz)

Figure 96 Comparison of different composite sound-insulation materials: (a) Code 3 lead sheet (partition 2); (b) 0.5-mm lead equivalent lead/PVC (partition 1 l ) : (c) 6-mm polyeurethane foam/Code 1 lead/6-mm polyeurethane foam (partition 8); (d) Kemtech 5000 (partition 9); (e) Code I lead sheet (partition I ) ; (f) 0.175-mm lead equivalent lead/PVC (partition IO) [247]. (Courtesy of ILZRO and Dr. G. Kerry and P. Lord, Univ. of Salford, UK.)

Chapter 2

242

performance by typically 5-10 dB. Fixing the absorbent directly to the bare material will improve the performance by typically 5-10 dB.Fixing the absorbent directly to the bare material has other advantages because it providesareadymeans of sealing at jointsandedges and wherepipework penetrates.

B.

Evaluation of Sound Reduction Index

The Sound Reduction Index is defined as

where L , and L2 are the average sound pressure levels in the Source room and receiving room, respectively, S is the area of the test specimen, and A is the total absorption in the receiving room (obtained from the Sabine equation A = 0.161 V/T, where V is the volume and T is the reverberation time). In ASTM specifications, this is referred to as Sound Transmission Loss. Sound reduction tests on a number of barrier configurations involving layered lead composites have been carried out at the University of Salford in England and Manville Services Corporation, in Denver, CO, U.S.A. [2472491. The tests at the University of Salford were performed as per BS 2750; Part 3: 1980 “Recommendations for field and laboratory measurements of airborne sound transmission in buildings.” This is identical to I S 0 140/1111978 and similar to ASTM E90/85 (which has been replaced with ASTM E90/90). The tests at Manville Services Corporation followed ASTM E90/ 85, which, as just mentioned, is similar to the British Standards used at the University of Salford. One of the differences is frequencies used for measurement and evaluation. The audible frequency rangeis divided in to octave bands or one-third octave bands. In the octave bands, the higher limit of is twice the value of the lowerfrequency frequency, J!, in agivenband limit,,f;, and the center of the frequency band is defined a s f = (J,J.)”2.In the one-third octave band, the higher limit of frequency,j;/;,,in a given band times the lower frequency limit, f L . In ASTM E90 tests, the meais surement of the Sound Reduction Index were carried out at the center of octave bands in the frequency range 125-4000 Hz, namely 125, 250, 500, 1000, 2000,and4000 Hz. In the University of Salford tests doneasper British Standard 2750, the measurements were made at the center of onethird octave bands in the frequency range 100-3150 Hz, namely 100, 125, 160,200,250,3 15,400,500,630,800,1000, 1250, 1600,2000,2500,3150, 4000, and 5000 Hz. The use of one-octave-band center frequencies gives a finer resolution of noisedata,but the results fromboth the laboratories presented here are comparable.

’~

243

Properties of Lead and Its Alloys

The University of Salford researchers have examined single-skin-layer and double-skin-layer lead composites involving plasterboard, PVC, rockwool, steel, chip board, and polyeurathane foam. In this work, the test partitions were built into an aperture measuring 2410 mm X 2410 mm set into the standard test aperture between two reverberant rooms. A 93-mm X 45mm timber stud frame was built across the aperture with studs set at 600mm centers (nominally). Both the single- and the double-skin partitions were fitted to this frame, the latter using the studding as a 93-mm spacer. The studs were situated inside the cavity for all double-skin partitions. Wideband random noise from a generator was amplified and reproduced in the source room using one of two alternative loudspeaker systems. The resultant sound levels were measured in both the source and receiving rooms using a one-third-octave-band real-time analyzer. The time taken for the sound to decay by 30 dB is measured and doubled to give the reverberation time. The reverberation time was obtained from the ensemble averaged decays at each frequency. The whole procedure was then repeated using the alternative loudspeaker. The Sound Reduction Index ( R ) was calculated from the averages of both sets of results. The arithmetic mean average over one-thirdoctave bands in the frequency range 100-3150 Hz were used to calculate weighted the Sound Reduction Index, R,, according to BS 5821: Part 1 1984. The Sound Transmission Class was also calculated according to ASTM E413-73 and it is the arithmetic average of the sound reduction indexes at the center of each octave bands in the frequency range 125-4000 Hz. Table 70 presents the Sound Transmission Class (STC) rankings and audibility of speech through barriers of different STC ratings [250]. Table

Table 70 Sound Transmission Class (STC) Rankings and Audibility of Speech Through Barriers of Different STC Ratings 12501. (Courtesy of Lead Industries Association, New York.) STC range

525 26-35 36-45 46-55

255

Audibility of speech through barrier Normal speech clearly understood Loud speech easily understood; normal speech 50% understood Loud speech 50% understood; normal speech faintly heard but not understood Loud speech faintly heard but not understood; normal speech inaudible Loud speech or music inaudible

Barrier ranking

Poor Fair Good Very good Exceptionally good

Chapter 2

244

Table 71 Summary of Acoustic Transmission Loss Data for Single-Skin and Double-Skin Test Partitions 12471. (Courtesy of ILZRO and Dr. G. Kerry, Univ. of Salford, UK.)

Surface Average Thickness Partition No. I

2 3 4 5 6

7 8

9 IO

11

12 13 14 15 16

17 18 19 20 21

SRI"

R,

STC (dB)

Description partition of (dB) (kg/m') (dB) (mm) test Singleskin-code 1 lead sheet Single skin-code 3 lead sheet Single skin-lead clad steel sheet Single skin- 1-mm-thick lead bonded to 9-mm plywood Single skin-code 3 lead sheet bonded to 9-mm plywood Single, skin-code 3 lead sheet bonded to 12.4-mm Gyproc plasterboard Single skin-Kemmetech 5000 bonded to 12.7-mm Redland plasterboard Single skin-code I lead sheet sandwiched between two layers of polyurethane foam Single skin-Kemmetech 5000 Single skin-0.175-mm lead equivalent lead-impregnated PVC sheet Single skin-0.5-mm lead equivalent lead-impregnated PVC sheet Single skin-Acoustec Single skin-12.4-mm Gyproc plasterboard Single skin-12.7-mm Redland plasterboard Single skin-9-mm plywood Single skin-9-mm galvanized steel Single skill- 12-mm chipboard Single skin- 18-mm medium density fiberboard Double skin- 12.4-mm Gyproc plasterboard-no infill Double skin- 12.4-mm Gyproc plasterboard-50-mm Rockwool RW3 infill Double skin"12.7-mm Redland plasterboard-no intill

l .S2 1.85 10.26

5.65 17.16 8.30 18.44

22.7 31.8 33.8 30.8

25 35 34

25 35 37 33

10.71

20.60

33.8

37

37

14.44

26. I O

35.2

38

38

14.63

15.63

29.3

32

31

12.5

6.79

25.4 28 28

1.93 0.74

5.53 2.67

24.9 18.9

27 22

27 22

2.17

7.94

27.4

30

30

1 .S2 12.38

4.33 9.52

22.6 27.2

25 30

2s 29

12.7

10.10

25.7 28 28

12.35 18.05

5.96 7.79 9.32 13.92

21.9 27 25.4 26.2

25 30 28 28

24 30 28 28

117.76

19.04

40.2

42

41

1 17.76

22.04

45.8 48 48

1 18.40

20.20

36.8

0.5

9.19 1

37

40

40

245

Properties of Lead and Its Alloys Table 71 Continued Part it ion No. 22

23

24

25

26

27 28 29

Description of test partition Double skin- 12.7-mm Redland plasterboard-50-mm Rockwool RW3 infill Double skin-code 3 lead sheet bonded to 12.4-mm Gyproc plasterboard-no infill Double skin-code 3 lead sheet bonded to 12.4-mm Gyproc plasterboard-50-mm Rockwool RW3 infill Double skin-Kemmetech 5000 bonded to 12.7-mm Redland plasterboard-no infill Double skin-Kemmetech 5000 bonded to 12.7-mm Redland plasterboard-50-mm Rockwool RW3 infill Double skin-Kemmetech 5000-no infill Double skin-Kemmetech 5000-50mm Rockwool RW3 infill Double skin-code 1 lead sheet sandwiched between two layers of polyurethane foam-no infill

Surface Average Thickness weight SRI” R,, STC (mm) (kg/m’) (dB) (dB) (dB) 118.40

23.20

42.5

45

46

121.88

52.20

51.8

52

52

121.88

55.20

57.3

59

59

122.26

3 1.26

44.5

46

46

122.26

34.26

50.3

52

53

96.86

11.06

36

35

36

96.86

14.06

44.6

44

44

70.00

13.58

36.5

34

34

“Sound Reduction Index.

7 1 presents a description of partitions used in the University of Salford tests along with the R,v and STC ratings [247]. Figures 97-125 present the onethird-octave sound reduction index curves of these partitions [247]. The sound reduction indices at one-third-octave band intervals provided are for a source room volume of 112 m’ and a receiving room volume of 225 mz. Manville Services Corporation has examined the production and sound reduction performance of composites of lead with gypsum board, fiberglass board, and other construction materials which could be used in noise control. The criteria used in these composite developments were strength, ease of installation, low areal density, and minimal environmental risk to the installer and user. These composites were tested using an ASTM E-90 Sound

Chapter 2

246 Freq. RT (Hz) (S)

SE (dB)

1008.30.7 1.0 1257.5 1607.40.6 2007.60.5 2506.70.4 315 5.70.3 400 6.00.2 0.1 5006.7 630 7.40.2 800 7.3 0.1 1000 7.2 0.1 1250 6.3 0.1 1600 5.3 0.1 2000 4.7 0.1 2500 3.9 0.1 3150 3.10.2 4000 2.40.3 5000 1.7 0.4

R (dB)

15.2 15.8 15.9 15.5 16.4 17.2 18.3 20.7 22.4 24.1 25.9 28.1 29.8 31.5 32.8 33.9 35.5 37.6

1/3 OCT SOUND REDUCTION INDEX

R (dB) .

T

'O 50 6o

1

i

lot 1WO

100

Figure 97 Sound reduction versus frequency curve for

Freq. RT

SE

(Hz)

(dB)

(S)

1009.60.9 1257.8 1.3 1607.80.6 200 7.60.7 250 6.7 0.4 315 5.60.3 400 6.00.2 5006.7 0.1 630 7.5 0.1 800 7.30.2 0.1 10007.2 12506.40.2 1600 5.5 0.1 20004.8 0.1 2500 4.1 0.1 31503.20.2 4000 2.50.3 5000 1.8 0.4

10000

Frequency ( H z )

partition 1 12471

R (dB)

21.8 21.8 24.3 23.9 25,8 26.4 27.9 30.1 31.9 33.6 35.5 37.7 39.5 41.4 42.8 44.0 45.8 47.1

t

1

04

100

1000 Frequency (Hz)

Figure 98 Sound reduction versus frequency curve for partition 2 [247].

10000

247

Properties of Lead and ItsAlloys Freq.

RT

(Hz)

(S)

SE (dB)

R (dB) 113 OCT SOUND REDUCTION INDEX

100 10.8 0.6 125 8.6 1.3 160 8.1 0.4 200 7.7 250 6.8 315 5.7 400 6.0 0.2 500 6.8 630 7.4 0.2 800 7.2 1000 7.3 1250 6.4 1600 5.6 2000 0.1 5.1 2500 4.4 3150 3.6 4000 2.8 5000 2.1

0.6 0.4 0.3 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.2

24.0 23.4 26.2 26.4 27.7 28.0 30.5 32.1 33.8 35.3 37.3 39.6 41.5 43.6 45.1 46.7 47.8 49.0

R (dB) 70

-

.~~

.~~

~

" "

-- -

RT

(Hz)

(S)

100 125 160

200 250 31 5 400 500 630 800 1000 1250 1600

SE (dB)

R (dB)

0.9 0.1 0.3 0.4 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.1 0.1

22.0 25.0 26.7 25.7 26.7 27.1 28.6 29.7 31.4 32.8 34.3 35.4 36.4 37.1 36.5 35.9 35.1 35.6

2000

0.1

2500 31 50 4000 5000

0.1 0.1 0.1 0.2

. .

~

. "

~

~

60 --

1

50

--

--

1

40

20

io

.

~

"

"

1

01 100

woo

i

1WO Frequency (Hz)

Figure 99 Sound reduction versus frequency curve for partition

Freq.

~

~

3 [247].

1i3 OCT SOUND REDUCTION INDEX R (dB)

70T - . 50 6o

i

.

04 100

1000 Frequency (Hz)

Figure 100 Sound reduction versus frequency curve

for partition 4 12471.

10000

248

Chapter 2

Freq.

RT

SE

IHz)

(s)

(dB)

100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

9.6 7.8 7.9 7.6 7.2 5.7 5.7 6.5 7.1 7.0 7.1 6.3 5.4 5.1 4.5 3.7 2.9 2.2

0.8 1.5 0.5 0.6 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

0.2 0.3 0.4

R (dB)

24.9 23.7 26.9 27.2 28.9 29.2 30.6 32.4 34.3 35.9 37.5 39.5 40.5 41.9 43.0 44.1 45.5 47.4

60

,

--

50 --

20 --

l o -0

100

1000

10000

Frequency (Hz)

Figure 101 Sound reduction versus frequency curve for partition 5 [247].

Transmission Loss facility. Table 72 presents a summary description of one of the sets of partitions studies [248]. Table 73 provides sound transmission loss values at different frequencies for these partitions (2481. The representative sound reduction data for different partitions are presented in the following sets of tables and curves of transmission loss (in dB) versus frequency (in Hz) (Figures 126-141) [248]. The Sound Transmission Class (STC) is a weighted average of the sound transmission over the audible spectrum and serves as a single index of performance of a material’s performance in noise control by transmission reduction. The construction industry has adopted “Sound transmission class determined as per ASTM E413 classification for rating sound insulation” as a single number rating system. Manville Corporation also had also examined acoustic performance of ( 1 ) lead-fiberglass mat sheet product, and (2) sandwiches of Manville’s 1in.-thick and 3-lb/ft3 fiberglass together with various thicknesses of lead sheet, expanded lead sheet, and a lead-vinyl composite sheet. The leadvinyl composite sheet was from Furukawa Electric Company. Table 74 gives a description of these composites and Figures 142-155 [249] gives the Sound Transmission Loss (STL or TL) values at different frequencies and the STC rating.

249

Properties of Lead andIts Alloys Freq. (Hz)

RT

SE

R

(S)

(dB)

(dB)

11.4 9.2 8.4 7.6 6.7 5.8 5.9 6.7 7.2 7.2 7.1 6.2 5.4 4.9 4.2 3.5 2.3 2.1

0.8

27.7 30.4 29.7 27.9 29.5 30.9 32.1 33.5 35.3 36.6 38.1 39.6 41.2 42.5 43.5 44.6 46.3 47.9

113 OCT SOUND REDUCTON INDEX

100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

1.1

0.5 0.7 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.2

R (dB) 7o

.

-

~

--

~

~

- -

I

r

10 2o 04 100

1000

I loo00

Frequency (Hz)

Figure 102 Sound reduction versus frequency curve

for partition 6 12471.

The acoustic transmission loss increases in the lead-fiberglass composites when the lead sheet thickness is increased. For the constructions with two layers of fiberglass and one middle layer of lead, increasing the lead weight from 1 to 2 lb/ft2 increased transmission loss from 4 dB at frequencies dB for the range 1000- 10,000 Hz. The between 100 and 1000 Hz and 2 results below 250 Hz are not reliable throughout this series of experiments because of the size of the test sample used. Increasing the lead sheet weight from 2 to 4 Iblft' resulted in a more uniform gain in transmission loss with a 5-dB difference measured for frequencies between 100 and 1000 Hz, but only 1-2 dB of difference for frequencies between 1000 and 10,000 Hz. In comparing the three-layer fiberglass/two-layer lead constructions to the two-layer fiberglass/one-layer lead constructions, significant gains can be seen. Comparing the two constructions which use I-lb/ft' lead, a 15-dB gain can be seen over the frequency range 250- 10,000 Hz. The gain is not as large when comparing the constructions made with 2-lb/ft2 lead; however, a 10-dB improvement still can be seen over the same frequency range. A great improvement is seen to result whenconstructionsmadewith three layers of fiberglass and two layers of the lead-vinyl composite are compared with the constructions made with two layers of fiberglasdone layer of the

Chapter 2

250 Freq.

RT

(Hz)

(S)

100 10.5 125 9.4 160 8.3 200 7.5 250 6.5 315 5.7 400 5.8 500 6.7 630 7.3 800 7.1 1000 6.9 1250 6.1 1600 5.3 2000 4.9 2500 4.3 3150 3.5 4000 2.7 5000 2.1

0.7 1.2 0.4 0.5 0.4 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2

23.1 25.9 25.8 24.6 25.1 26.0 27.6 28.6 30.3 31.0 31.8 32.0 32.7 34.4 34.9 34.3 33.1 34.7

1

6o 50

0

{

100

1000 Frequency (Hz)

Figure 103 Sound reduction versus frequency curve for

100 9.2 125 7.5 1.4 160 7.2 200 7.1 0.6 250 6.3 315 5.3 0.3 400 5.5 500 6.2 0.2 630 6.6 800 6.2 1000 6.1 1250 5.4 0.1 1600 4.8 2000 4.3 2500 3.9 0.1 3150 3.2 4000 2.6 5000 1.9

0.7 0.6 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.2 0.3 0.4

18.1 17.3 18.7 17.9 19.2 19.9 21.7 23.1 24.7 26.0 27.5 30.1 32.6 35.4 36.7 37.8 39.6 40.9

10000

partition 7 [247].

i

lo 0 100

1WO

10000

Frequency (Hz)

Figure 104 Sound reduction versus frequency curve for

partition 8 1247).

251

Properties of Lead and Its Alloys

100 11.5 125 9.8 160 8.5 200 7.8 250 6.8 31 5 5.6 400 6.0 500 6.6 630 7.3 800 7.2 1000 7.1 1250 6.4 1600 5.5 2000 5.0 2500 4.5 31 50 3.6 4000 2.9 5000 2.2

0.8 1.3 0.5 0.5 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2

16.6 16.0 18.5 16.5 17.9 19.1 20.8 22.4 24.4 26.3 28.4 30.5 32.2 34.1 35.6 36.9 38.6 40.5

113 OCT SOUND REDUCTION INDEX

t

lo

1000

100

Figure 105 Sound reductionversusfrequencycurveforpartition

Freq. RT

(Hz)

(S)

100 9.2 125 7.8 1607.9 200 8.0 250 7.0 315 5.9 400 6.1 5006.7 6307.4 8007.3 1000 7.2 1250 6.3 1600 5.4 2000 4.8 2500 4.0 3150 3.1 40002.4 5000 1.7

SE (dB)

R (dB)

0.7 1.1 0.5 0.5 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.3 0.4

11.4 12.0 12.7 11.1 12.9 13.3 14.8 16.3 18.0 19.9 21.8 24.0 25.6 27.7 29.3 30.8 32.4 33.8

10000

Frequency (Hz)

2o 10

0

9 [247].

W

100

Figure 106 Sound reductionversusfrequencycurve

1000

Frequency (Hz)

for partition 10 12471

1 10000

Chapter 2

252

113 OCT SOUND REDUCTION INDEX

100 125 160 200 250 315 400 500

9.6 7.8 7.9 7.6 7.2 5.7 5.7 6.5

0.9 18.7 1.4 17.6 0.5 19.5 0.5 20.1 0.4 21.4 0.2 21.6 0.2 23.5 0.1 25.2

800 1000 1250 1600 2000 2500 3150 4000 5000

7.0 7.1 6.3 5.4 5.1 4.5 3.7 2.9 2.2

0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.3 0.3

28.8 30.7 32.9 34.8 36.9 38.6 40.2 41.6 43.0

R(dB)

"_

70

.

" "

_~_"

~

50

40

3o

4

10

1

~

1000 Frequency (Hz)

Figure 107 Sound reduction versus frequency curve for

Freq. (Hz1

100 125 160 200 250 315 400 500

RT

(SI 8.0 6.6 7.2 7.3 7.0 5.5 5.6 6.3 7.0 7.0 7.0 6.2 5.3 4.9 4.3 3.4 2.7

630 800 1000 1250 1600 2000 2500 3150 4000 5000 2.0

SE (dB1

R (dB1

1.1 1.0 0.4 0.5 0.4 0.3 0.3 0.2 0.1 0.2 0.2 0.3 0.1 0.1 0.1 0.2

15.3 14.3 14.8 15.0 17.6 17.3 18.7 20.7 22.0 23.7 25.8 27.9 29.6 31.7 33.2 34.8 36.3 37.5

0.3 0.4

.

6o

I 10000

partition 1 1 12471.

l l 3 OCT SOUND REDUCTION INDEX R (dB)

O'

:l 6o 50

T"-

1

20

.

.

."

.

1 l

10 "

I

100

10000

1000 Frequency (Hz)

Figure 108 Sound reduction versus frequency curve for

partition 12 [2471.

253

Properties of Lead andIts Alloys Freq.

RT

SE

R

(Hz)

(S)

(dB)

(dB)

100 12.3 1.2 125 11.1 1.1 160 8.3 0.4 200 7.5 0.4 250 6.6 0.4 315 5.6 0.3 400 5.9 0.2 500 6.5 0.2 630 7.1 0.1 800 6.9 0.1 1000 6.9 0.1 1250 6.0 0.1 1600 5.3 0.1 2000 4.9 0.1 2500 4.3 0.1 3150 3.6 0.1 4000 2.9 0.1 5000 2.1 0.2

19.3 22.2 22.1 21.7 23.7 23.3 24.4 26.0 27.6 28.9 30.7 32.0 33.6 35.0 35.0 30.3 27.8 30.2

1 3 l OCT SOUND REDUCTION INDEX

R (dB)

't 'Or

"

- -

~~

~

~-

40

lot 04 100

IO00 Frequency (Hz)

Figure 109 Sound reduction versus frequency curve

100 10.7 0.7 125 9.0 1.2 160 8.2 0.6 200 7.7 0.6 250 6.7 0.4 315 5.5 0.3 400 5.7 0.2 500 6.3 0.2 630 6.8 0.2 800 6.7 0.1 1000 6.6 0.1 1250 6.0 0.1 1600 5.3 0.1 2000 4.8 0.1 2500 4.3 0.2 3150 3.6 0.1 4000 2.9 0.1 5000 2.2 0.2

19.0 21.3 22.1 21.4 22.9 22.6 24.0 25.0 26.7 28.3 29.7 31.3 32.6 32.3 26.7 25.5 29.3 32.3

for partition 13 12471.

113 OCT SOUND REDUCTION INDEX

-

R (dB) 70

60 --

--

50

40 --

i

30 - -

!

-

20 10

j l

"

O T

100

1000

loo00

Frequency (Hz)

Figure 110 Sound reduction versus frequency curve for

partition 14 [247].

Chapter 2

254

100 9.3 0.8 125 7.5 1.3 160 7.3 0.6 200 7.4 0.6 250 6.5 0.4 531 18.9 0.3 5.5 5.8 400 20.0 0.2 500 6.5 21.8 0.1 630 7.1 0.1 800 0.1 7.0 1000 6.9 25.6 0.1 0.1 12506.0 16005.1 0.1 2000 4.6 28.0 0.1 2500 3.9 0.1 31503.0 0.2 40002.4 0.3 5000 1.7 0.4

113 OCT SOUND REDUCTIONINDEX

16.2 16.4 17.9 17.4 18.9

R(dB)

70 6o "

--

40

3o

22.9 24.4 27.0 28.0

*O

-

10

~

01

I

,

1000

10000

Frequency (Hz)

24.6 22.9 23.9 26.3

Figure 111 Sound reduction versus frequency curve for partition 15 12471.

Freq. RT (Hz) (S)

SE

R

(dB)

(dB)

1009.0 1257.6 160 7.5 200 7.4 2506.4 315 5.6 400 5.9 500 6.5 6307.3 8007.2 10007.0 1250 6.1 1600 5.2 2000 4.6 2500 3.8 3150 3.0 4000 2.3 5000 1.6

0.7 1.2 0.5 0.6 0.4 0.3 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.3 0.4

17.8 18.0 20.5 19.9 20.5 21.3 23.3 24.8 26.6 28.4 30.4 32.5 34.1 36.3 37.8 39.2 40.9 42.5

1i3 OCT SOUND REDUCTION INDEX R (dB)

50

10

0 1000

100

Frequency (Hz)

Figure 112 Sound reduction versus frequency curve

for partition 16 [247].

1 10000

255

Properties of Lead and Its Alloys

100 9.90.7 1257.91.3 1607.60.5 2007.6 0.6 250 6.50.3 315 5.60.3 400 5.90.2 5006.6 0.1 630 7.1 0.1 800 6.9 0.1 1000 6.8 0.1 1250 6.1 0.1 0.1 16005.3 2000 4.8 0.1 2500 4.0 0.1 3150 3.2 0.2 4000 2.5 0.2 5000 1.9 0.4

19.8 19.8 20.8 20.9 22.4 23.1 23.9 25.7 26.7 28.2 29.6 31 .O 31.7 31 .l 26.3 25.5 28.5 31.2

"t 40

3 0 20

~

10

~

0 100

Figure 1 1 3 Sound reduction versus frequency curve for

Freq.

RT

(Hz)

(S)

10000

1000 Frequency (Hz)

partition 17 12471.

SE (dB)

100 9.1 0.9 1257.31.3 1607.60.5 2007.40.6 250 7.1 0.3 3155.70.3 400 5.90.2 5006.6 0.1 630 7.30.2 800 7.1 0.2 1000 6.9 0.1 1250 6.1 0.1 1600 5.1 0.1 20004.7 0.1 2500 4.1 0.1 3150 3.20.2 4000 2.50.3 5000 1.9 0.4

22.6 21.5 23.2 24.3 26.0 25.4 25.7 27.8 28.5 29.1 28.5 26.3 24.7 26.1 28.6 31.6 34.1 36.1

113 OCT SOUND REDUCTION INDEX

R (dB)

70T

.-

" "

~

-.

~.

-

"1

l 1

6o 50

1

~

1

210 0 04

100

1000

Frequency (Hz)

Figure 114 Sound reduction versus frequency curve for partition 18 12471

1 10000

256

Chapter 2

Freq.

RT

(Hz)

(S)

100 8.2 125 8.4 160 7.8 200 7.6 250 6.2 315 5.5 400 5.9 5006.7 630 7.3 800 7.3 1000 7.2 1250 6.4 16005.5 2000 5.0 2500 4.4 31503.5 40002.8 5000 2.1

SE (dB)

R (dB)

0.8 1.2 0.7 0.5 0.4 0.4 0.3 0.2 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.2

19.6 27.8 26.7 31.2 30.1 29.6 34.2 38.4 42.3 46.0 48.7 52.8 55.5 57.7 57.3 45.7 41.5 47.6

113 OCT SOUND REDUCTKIN INDEX

-

R (dB) 70

60 -50

--

40

-i

10

"

l

0, 100

1000

10000

Frequency (Hz)

Figure 115 Sound reduction versus frequency curve for partition 19 [247].

Freq. (Hz)

RT (S)

1008.9 125 8.6 160 8.0 2007.7 2506.4 315 5.6 400 5.9 500 6.7 630 7.3 8007.2 1000 7.1 12506.4 16005.6 20005.1 2500 4.5 3150 3.7 4000 2.9 5000 2.2

SE (dB)

R (dB)

0.8 1.1 0.5 0.5 0.4 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.2

22.4 31.6 35.5 35.9 35.6 37.8 43.0 46.9 50.3 52.3 54.9 57.0 58.5 60.6 59.9 51.2 48.3 53.5

60 --

l

50 --

, j

20 10

"

"

0 100

Figure 116 Sound reductionversusfrequency

l

1000

Frequency (Hz)

curve for partition 20 12471.

lo000

257

Properties of Lead andIts Alloys SE (dB)

R (dB)

100 10.7 0.7 125 9.0 1.1 160 8.2 0.6 200 7.7 0.5 250 6.7 0.4 315 5.5 0.3 400 5.7 0.3 500 6.3 0.2 630 6.8 0.2 800 6.7 0.2 1000 6.6 0.1 1250 6.0 0.1 1600 5.3 0.1 2000 4.8 0.1 2500 4.3 0.1 3150 3.6 0.1 4000 2.9 0.2 5000 2.2 0.2

18.5 24.1 25.3 31.4 32.4 30.1 33.4 36.1 39.9 42.7 45.8 49.3 51.6 49.8 40.0 38.4 43.3 48.5

Freq.

RT

(Hz)

(S)

113 OCT SOUND REDUCTION INDEX

R (dB) 70

.. .

..

~

..

.~

"

.. 1

-50 -40 --

1

60

1

1

10 - -

1 10000

01 100

1000 Frequency (Hz)

Figure 117 Soundreductionversusfrequencycurveforpartition2112471.

Freq.

RT

SE

R

(Hz)

(S)

(dB)

(dB)

0.7

19.1 28.2 33.8 38.3 35.8 35.6 41.5 41.9 46.2 47.6 51.9 54.7 56.4 55.8 48.9 44.6 49.1 53.7

100 7.7 125 6.6 160 7.6 200 7.5 250 6.3 0.4 315 5.4 400 5.8 500 6.6 0.2 630 7.3 800 7.2 0.2 1000 7.2 1250 6.4 1600 5.6 2000 5.1 2500 4.4 3150 3.6 4000 2.9 5000 2.2

1.2

0.7 0.6 0.3 0.2 0.2

0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2

113 OCT SOUND REDUCTION INDEX

R (dB) ...

."

..

~

~.

"

"

.. ..

60

t

lo

1

04 100

1000 Frequency (Hz)

Figure 118 Sound reduction versus frequency curve

for partition 22 12473.

1WOO

Chapter 2

258 Freq.

RT

(Hz)

(S)

100 9.8 125 8.1 1607.6 2007.8 250 6.6 315 5.6 400 5.9 5006.7 630 7.3 8007.3 1000 7.1 12506.3 1600 5.4 2000 4.8 2500 4.1 3150 3.3 4000 2.6 5000 1.9

SE (dB)

R (dB)

0.8 1.1 1.0 0.7 0.5 0.3 0.3 0.4 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.4

32.2 42.4 33.3 40.9 41.3 40.0 45.3 49.4 53.3 56.3 59.0 63.0 65.9 66.9 69.1 70.9 72.6 71.9

113 OCT SOUND REDUCTION INDEX R (dB)

80

--

70

--

..

..

1

60 --

~

1

--

50

30

1

"

20 -~

lo

1

"

1

0, 100

10000

1000 Frequency (Hz)

Figure 119 Sound reductionversusfrequencycurveforpartition

Freq.

RT

SE

R

(Hz)

(S)

(dB)

(dB)

0.7 1.0 0.6 0.6 0.4

38.3 45.3 40.9 43.6 47.9 49.1 51.6 56.2 60.8 63.6 65.5 67.8 69.5 71.4 72.5 73.5 75.1 74.2

100 10.1 125 8.5 160 7.9 200 7.9 250 6.7 5.6 315 400 5.9 500 6.7 630 7.4 800 7.3 1000 7.2 1250 6.4 1600 5.6 2000 5.1 2500 4.5 3150 3.6 4000 2.9 5000 2.1

0.2

0.2 0.2 0.2 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.3 0.4

23 [247].

1/3 OCT SOUND REDUCTION INDEX R (dB) ".

60 --

30 --

1

20 - 10

1

"

0, 100

4 1000

10000

Frequency (Hz)

Figure 120 Sound reductionversusfrequencycurveforpartition

24 (2471.

259

Properties of Lead andIts Alloys Freq.

RT

SE

R

(Hz)

(S)

(dB)

(dB)

100 10.5 0.8 125 9.4 1.1 160 8.3 0.6 200 7.5 0.5 250 6.5 0.4 315 5.7 0.3 400 5.8 0.3 500 6.7 0.2 630 7.3 0.2 800 7.1 0.2 1000 6.9 0.1 1250 6.1 0.1 1600 5.3 0.1 2000 4.9 0.1 2500 4.3 0.2 3150 3.5 0.2 4000 2.7 0.1 5000 2.1 0.1

26.6 36.4 31.4 34.4 33.7 34.7 38.0 42.9 46.5 49.1 51.6 54.9 57.6 59.4 58.2 56.7 55.8 61.7

1/3OCT SOUND REDUCTION INDEX R (dB) . ..

.

-~

.

RT

SE

(S)

(dB)

100 8.40.8 125 8.0 1.3 1607.80.6 200 7.80.5 250 6.60.5 315 5.5 0.2 400 5.90.3 500 6.9 0.1 630 7.40.2 800 7.4 0.2 1000 7.2 0.1 12506.5 0.1 1600 5.7 0.1 20005.2 0.1 2500 4.5 0.1 31503.6 0.1 4000 2.80.2 5000 2.10.2

.

.

.

t

lo

100

1000

10000

Frequency (Hz)

Figure 121 Sound reduction versus frequency curve

Freq. (Hz)

.. .

for partition 25 [247].

R (dB)

28.7 38.8 42.4 38.5 39.0 43.4 44.9 50.7 53.2 56.6 57.9 59.7 61 .l 63.1 63.9 63.5 62.1 66.8

113 OCT SOUND REDUCTION INDEX R (dB)

40 30 2o lo

t t

04 100

1 1000 Frequency (Hz)

Figure 122 Sound reduction versus frequency curve for partition 2612471.

10000

260

Chapter

Freq.

RT

SE

R

(Hz)

(S)

(dB)

(dB)

100 9.2 0.8 125 7.8 1.2 160 7.8 21.9 0.7 200 7.7 0.6 250 6.5 0.4 315 5.6 0.3 400 5.8 28.7 0.3 5006.7 0.5 630 7.1 36.7 0.2 800 7.1 0.2 1000 7.0 0.2 1250 6.3 0.1 1600 5.5 0.1 0.1 2000 5.0 2500 4.4 0.1 3150 3.6 0.1 4000 2.9 0.2 5000 2.2 0.2

13.6 15.1 22.6 23.6 25.7 32.5

113 OCT SOUND REDUCTION INDEX R(dB) 7 o T ~~.

.

~

."

"_

~

" "

~

.

-

6o 50.-

40

..

3o

20-

40.2 43.6 49.1 52.7 54.8 56.3 58.4 60.0 61.0

__ 1000

1 1woo

Frequency (Hz)

Figure 123 Sound reduction versus frequency curve for partition 27 [247]

Freq.

RT

(Hz)

(S)

100 7.8 0.8 125 7.3 160 7.5 200 7.5 250 6.2 0.4 315 5.6 400 5.9 500 6.7 0.2 630 7.4 0.2 800 7.3 1000 7.2 1250 6.4 1600 5.6 2000 0.1 5.1 2500 4.5 3150 3.7 4000 3.0 5000 2.2

SE (dB)

1.2 0.6 0.6

0.3 0.2

0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.2

R

(dB) 14.9 20.4 24.7 30.4 34.8 39.1 44.1 49.0 52.8 55.0 56.7 58.0 58.5 58.2 58.2 59.1 61.2 62.0

10

0 100

1WO

Frequency (Hz)

Figure 124 Sound reduction versus frequency curve for partition 28 [2471.

1 10000

261

Properties of Lead andIts Alloys Freq. (Hz)

UT

100 125 160 200 250 315 5.0 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

8.4 0.9 6.7 6.4 0.6 6.4 0.5 5.6

(S)

5.4 6.1 6.7 6.4 0.1 6.3 5.6 4.9 4.4 3.8 3.1 2.5 1.9

SE (dB)

0.9

0.4 0.4 0.2 0.1 0.1 0.2 0.1 0.1 0.1 0.2 0.2 0.2 0.3

R (dB)

16.1 16.0 16.5 17.3 20.9 24.0 29.2 34.9 39.8 44.1 46.6 49.1 51.5 55.2 59.8 63.0 64.6 63.6

113 OCT SOUND REDUCTION INDEX R (dB) 70

~~

~~

..

~

~. .

~~

”. . .

j

--

60

l

50 - -

~

--

40

30 --

20 10

l

l

”

”

l

07 1000

100

Frequency (Hz)

Figure 125 Sound reduction versus frequency curve

composite. A 20-dBimprovementcan

10000

for partition 29 [247].

be seen for frequenciesover 1000

Hz. Similar sandwich constructions were made using the lead-tiberglass mat composites. The weight of the fiberglass mat composite for all of the sandwiched constructions was 0.25 lb/ft’. The tiberglass mat composite was produced by Doe Run using their patented process for lead-coated fiberglass mat. A 15-dB improvement was seenin the measurements made on the three layers of fiberglass/two layers of lead/fiberglass mat compared with the two layers of fiberglass/one layer of lead/fiberglass mat construction. Figures 156-158 show the variation of STC rating with the sheet areal density for composites of fiberglass mat with lead mat, lead vinyl, and lead sheets, respectively [249]. The effectiveness of the constructions in reducing sound transmission decreases with increasing areal weight. It is very interesting to observe that the 0.5-lb/ftz fiberglass mat provides the same transmission loss results as the I-lb/ft’ lead sheet.

C.

Internal Friction Behaviorof Lead and Lead Alloys

When no additional energy input is given to an oscillating system, the energy of oscillation (proportional to the square of amplitude A ) decreases during

Table 72 Identification of Basic Panel Constructions [248]. (Courtesy of ILZRO.) Specimen

L I A Bul. curve No.

Type

Ref. Fig. No.

A2 B1

5 5 6

Wall Wall Wall

B2

6

Wall

1

c1 D1 El

7 33 34

Wall Wall Wal I

2 3

F1

14

Wall

4

GI H1

15 16 and 30

Wall Wall

4 5

H2 I1

16 and 30 17

Wall Wall

5 6

J1

18 31

Wall Wal I

6

KI L1

28

Wall

8

A1

1

7

tu Q, tu

Description Four-inch solid lightweight concrete block As in A1 but painted both sides As in A1 plus I-in. by 2-in. wood furring on one side with %-in. fiberglass insulation in furring cavities. I-psf lead sheet applied over furring strips with Ih-in. gypsum board applied over lead sheet As in B1 but drywall joints treated with joint compound and drywall tape in place of duct tape As in B I but with 2-in. by 2-in. furring and ll/z-in. insulation Wood stud wall with ‘/?-in. gypsum board each side As in D1 but with I-psf sheet lead attached to studs on one side and fiberglass insulation in stud cavities “Retrofit” of wall D1 consisting of I-in. by 2-in. wood fumng to one side with %-in. fiberglass insulation in furring cavities, 1 -psf sheet lead fastened over furring with 1/2-in. gypsum board applied over lead sheet As in F1 but with 2-in. by 2-in. wood fumng and 1 ‘/?-in. fiberglass insulation 35/,-in. structural steel stud wall with %-in. fire-rated gypsum wallboard on each side As in H1 but gypsum board caulked both sides “Retrofit” of wall H2 consisting of I-in. by 2-in. furring one side, %-in. fiberglass insulation in furring cavities, 1 -psf lead sheet fastened over furring with S/x-in. gypsum wallboard applied over lead sheet As in I1 but with 2-in. by 2-in. wood furring and IVz-in. fiberglass insulation As in H2 but with I-psf sheet lead applied between studs and gypsum wallboard one side and with fiberglass insulation installed in stud cavities Is/R-in. light-gauge steel stud wall with !/?-in. gypsum wallboard each side of stud

3

al

2 9 h)

MI

29

Wall

NI 01

19 20

Enclosure Enclosure

10 10

Enclosure Enclosure Enclosure

10

RI

21

9

Enclosure Enclosure Enclosure Enclosure

12 12

U1

40

Door

13

u2 v1

40 41

Door Door

13 14

v2 v3 v4 WI w2 w3 w4

41 41 41 41 41 41 41

Door Door Door Door Door Door Door

14 14 14 14 14

14 14

As in LI but with I-psf lead sheet applied between studs and gypsum wallboard one side and with fiberglass insulation in stud insulation cavities %-in. plywood applied over one side of 2-in. by 4-in. wood studs As in panel N1 but with I-in.-thick flexible urethane foam applied over plywood and I-psf lead sheet bonded to foam As in 01 but with foam-lead sheet composite butt joints sealed with duct tape h/l-in. plywood applied over one side of 2-in. by 4-in. wood studs I/,-in. plywood applied over one side of 2-in. by 4-in. wood studs with Il/>-in., 6-pcf fiberglass board bonded to plywood and second layer of %-in. plywood bonded to fiberglass “core” As in panel QI but with I-psf lead sheet between the fiberglass core and plywood skin on each side of the panel T/n-in. gypsum wallboard applied over one side of 3Vn-in. structural steel studs As in S1 but with perimeter caulked As in S2 but with I-psf lead sheet bonded to gypsum wallboard one side, lI/~-in., 6-pcf fiberglass insulation board over lead, I-psf lead sheet bonded over fiberglass insulation and %-in. fire-rated gypsum wallboard bonded over lead sheet “Hollow core,” I?/~-in.thick by 2-ft, 6-in. by 6-ft., 8-in. plywood skin door (operable door) As in UI but door sealed around perimeter both sides (inoperable door) 17/~-in.thick by 2-ft., 6-in. by 6-ft, 8-in. plywood skin door with ll/~-in.thick, 6-pcf fiberglass insulation board in cavity, I-psf lead sheet bonded to fiberglass core on both sides and plywood skins bonded over lead sheet (operable door) As in VI but door sealed around perimeter both sides (inoperable door) As in V1 but with mechanical seals around perimeter (operable door) As in V3 but with aluminum threshold at bottom (operable door) As in VI but with 1.3-pcf fiberglass core (operable door) As in WI but door sealed around perimeter both sides (inoperable door) As in WI but with mechanical seals around perimeter (operable door) As in W3 but with aluminum threshold at bottom (operable door)

Table 73 STC Values of Basic Panels Corresponding to Figures 126- 141 [248]. (Courtesy of ILZRO.) Test frequency Specimen

100 125

160 200 250

A1 A2

19 22 19 19 20 17 16 16 16 15 17 21 22 28 14 14

20 25 25 25 31 14 25 21 23 20 22 29 36 37 16 29

B1 B2 c1 D1 El F1 GI H1 H2 I1 J1 K1 L1 MI

21 25 22 22 25 14 19 16 17 19 21 25 28 31 16 21

21 27 32 33 37 23 35 30 33 26 29 39 42 40 19 35

22 28 36 37 39 26 34 35 35 27 30 45 44 43 22 42

315 400

500

630 800

1000 1250 1600 2000 2500

22 30 43 43 47 32 40 43 42 35 39 51 52 50 31 49

23 32 45 45 49 36 43 46 47 39 43 52 54 52 34 49

24 34 49 49 53 39 45 50 50 42 45 55 56 54 38 51

26 37 56 56 60 44 51 54 54 46 49 60 60 57 44 57

21 29 40 40 43 29 36 40 38 31 34 48 50 48 25 47

24 35 51 52 56 41 48 52 52 44 47 56 57 55 41 55

28 40 60 60 62 47 53 57 57 48 50 62 63 59 47 62

30 42 64 64 65 49 55 59 59 45 48 62 62 58 49

64

31 44 66 66 66 49 5s 60 59 37 38 55 55 48 48 66

33 47 65 66 67 43 50 57 55 35 36 52 52 45 42 64

3150 4000 36 51 65 66 66 39 47 55 52 37 39 56 56 48 39 58

39 5s 67 68 70 40 50 58 56 42 46 63 63 54 44 60

5000 44 59 71 71 74 46 55 63 62 44 51 67 67

3

gg

58 49 6

4

N

Nl 01 02 PI Q1 R1 s1 s2 T1 u1 u2 v1 v2 v3 v4

w1 w2 w3 w4

13 16 16 8 13 16 14 14 16 4 3 9 20 17 18 9 16 16 15

14 20 20 12 15 17 18 19 19 7 9 11

20 18 19 10 14 14 14

14 21 20 14 15 16 19 21 21 7 10 9 19 16 17 12 17 17 16

16 22 22 15 16 19 20 22 30 9 11 10 17 15 16 14 27 25 26

IS 23 22 15 I8 26 21 23 37 10 14 12 16 16 16 16 33 32 33

19 23 23 15 20 31 22 24 41 9 13 13 27 25 26 14 36 31 33

21 23 23 18 25 33 24 26 44 12 17 15 35 28 31 16 40 33 37

23 22 22 20 32 33 25 28 47 12 15 16 38 28 31 17 41 33 37

22 26 26 22 38 35 27 30 52 13 15 17 40 29 32 18 45 34 38

23 30 29 23 43 38 28 31 54 12 14 16 41 27 32 18 45 32 35

22 36 36 25 47 42 30 32 59 15 20 16 45 27 33 18 47 32 38

22 44 44

27 50 46 31 33 63 16 22 17 48 26 33 18 49 31 36

21 41 41 28 54 51 31 33 65 16 23 16 51 26 34 I8 51 30 36

21 42 42 29 57 52 26 28 64 15 24

1s 53 26 35 16 53 31 35

22 45 46 29 57 58 24 26 65 13 26 13 53 27 35 14 53 33 36

24 50 50 27 57 60 25 29 70 13 27 12 51 29 37 15 52 35 39

26 54 55 27 59 61 27 32 74 15 29 14 53 32 39 16 54 36 41

21 60 61 28

64 64 28 36 75 15 30 16 54 31 39 17 54 35 41

Chapter 2

3 .' .-

l:

"."

"""---

"_""

"""

-- "~

-"

100

"

""

IO00

10000

Frequency, Hertz 4" Solid Masonry Block Wall

__ Specimen A1: Uncoatedwall - STC=27

""_

SpecimenA 2 : WaU with two coats latex paint both sides ofwall - STC=37

Figure 126 Sound reduction index curves for panel AI and A2 in Table 7 3 [248].

m vi

.so 70

-~

3 60

--

.6 50

~-

U) U)

.-

5 E

~c~"""_--

a

-.,*

40

.

,-e-

*

"

30 20

K

v)

*.#"

10

/=-:-.. .

,**

-

~

.-

- --- -

~

-

~-

0. 100

1000

10000

Frequency, Hertz 4 Solid Masonry Block Wallwith Furred Gypsum Board Retrofit Walls SpecimenAI: Uncoatedwal - STC=27

""-

Specimen BI: Basewall with l-in. x 2-in. frrred gypsun board retrofit- STC=46 SpecimenCl:Basewallwith2-1n.x2in.fu-redgypsunboardretrofit-STC=49

Figure 127 Sound reduction index curves for panel A l , B I , and C1 in Table 73 [248].

Properties of Lead andIts Alloys

267

1000

100

10000

Frequency, Hertz Commn 2” x 4 Wood Stud, 112” Gypsum Board Wall With And Without Lead Sheet And Fiberglass Insulation Specmen D l : 2-117 x 4-in. wood stud basewall wlli2-m. gypsum each slde - STC=35

~.

””_

Specimen El:Basewal plus 1 -psf lead sheet 8 fiberglass Insulation- STC=43

Figure 128 Sound reduction index curves for panel D1 and El in Table 73 [248].

80

m v 70

3 60 g 50 3 40 -!

EE 30 : 20

a C

10

(I)

0 100

1om

10000

Frequency, Hertz Common 2 x 4 Wood Stud, 112” Gypsum BoardWall Wlth Furred Gypsum Wallboard Retrofit Walls ~

” _ ”

Specimen D l : 2-In. x 4-in. wood stud basewall wlli2-in. gypsun eachside STC=35 ~

SpeclmenF1: Basewall with l-In. x2-in. fured gypsun board retrofit - STC=40 Specimen G1:Basewall with 2-m. x 2-In. furedgypsum board retrofit- STC=41

Figure 129 Sound reductionindex curves for panel D l , F1. and G I in Table 73 [248].

Chapter 2

268

100

10000

1000 Frequency, Hertz Comnon 3-518 Steel Stud, 518' Gypsum Board WallW t h And Wlthout Caulking Around Gypsum Board Perimeter

-Specimen H1: 3-51841. steel stud basewall wlo gypsum caulked - STC=37

""_

Specimen HZ:Basewall withQ~~SIIITI board perimeter cau#ced - STC=39

Figure 130 Sound reduction index curves for panel H1 and H2 in Table 73 [248].

m

ao 70

3 60 U)

0 100

1000

10000

Frequency, Hertz Common 3-518" Steel Stud,98" Gypsum Board WallWtth Furred Gypsum Wallboard Retrofit Walls

-Speumen H2: 3-5/8-in. steelstud basewall w/gypsumboard caulked - STC.39

"_

Speamen 11: Basewall with l-in. x 2-m. furredgypsun board retrofit- STC=49

...........Specimen J l : Basewail with 2-m. x2-m. furred gypsun board retrofit- STC=52

Figure 131 [248].

Sound reductionindex

curves for panel H2, 11, and J1 in Table 73

269

Properties of Lead andIts Alloys

l00

1000

10000

Frequency, Hertz Common 3-5/8"Steel Stud, 518" Gypsum BoardWall With And Without Lead Sheet And Fiberglass Insulation -Specimen

H 2 : 3-5B-in. steel stud basewall W/gypsun board caulked- STC=39

Speclmen K1: Basewall plusl p s f lead sheet 8 fiberglass Insulation- STC=49

" "

Figure 132 Sound reduction index curves for panel H2 and K1 in Table 73 [248].

100

1000

10000

Frequency, Hertz Common 1-5/8Steel Stud, 1/2" Gypsum Board Wall With And Without Lead Sheet And Fiberglass Insulation -Specimen L1: 1-5/8-1n. --

steel stud basewallw/gypsun board caulked- STC=34

- - Specimen M1: BasewaU plusl-psf lead sheet 8 fiberglass Insulation- STC=45

Figure 133 Sound reduction index curves for panel L1 and M I in Table 73 12481.

270

Chapter 2

m 80 T) vi 70 ln

60

.-5 50 ln ;. 40

E l-

5

v)

30 20 10

0 100

1000 10000 Frequency, Hertz Enclosure Consisting of 34" Plywood Over 2" x 4" Wood Studs With And Without FoamLead Sheet Composite

-Specimen

N1:314-in. plywood basewallover wood stud - STC=22

_ _ _ _ Specimen 01: Basewall plus 1-in.fedble foamlead sheet composite - STC-30 Figure 134 Sound reduction index curves for panel N1 and 01 in Table 73 [248].

80

I

100

1000 Frequency, Hertz Enclosure: 1/4"Plywood Over 2 ' x 4" Wood Studs With Fiberglass Core-Plywood or Lead-Fiberglass Core-LeadPlywood CompositeAdded

10000

-Speumen P2: 1/4-1n.plywood basewall- STC=24 _ - _ - _Specimen Q 1 : As P I plus fiberglasscore + p)ywood - STC=31 .......... Speumen R1:As P1 plus lead-fiberglasscnre-lead-plpvuod- STC=36

Figure 135 Sound reduction index curves for panel PI, Q I , and R I in Table 73 12481.

271

Properties of Lead andIts Alloys

100

1000

10000

Frequency, Hertz Enclosure: Single Layer5/8"Gypsum Wallboard Over 3-5/8"Steel Studs S1 : Perimeterof gypsum boardnot caulked - STC=27

-Specimen

- - - - Specimen S 2 : Penmeter of gypsum board caulked - STC=29

Figure 136 Sound reduction index curves for panel S1 and S2 in Table 73 [248].

,-/' ,""" /

,M

-

-./

/'

"

/

/ /

100

1000

10000

Frequency, Hertz Enclosure: Single Layer 518" Gypsum Wallboard Over 3-518" Steel Studs8 GypsumLead Sheet-Fiberglass Core-Lead Sheet-Gypsum Over Steel Studs

-SpeclmenS 2 Gypsum board o

w steel studs - STC=29

SpeclmenTI: Gypsvn-lead-fiberglass-leadgypsum owr steel studs - STC=42

""

Figure 137 Sound reduction index curves for panel S2 and TI in Table 73 [248].

Chapter 2

272

.-g In

50

.g 40 In

5

30

L

20 C

10

=I

0

100

1000

10000

Frequency, Hertz Door: Hollow Core Wood Door With Honeycomb Internal Support

-Specimen

"_

U1: ConventionallyHung Door - STC=14

- Speclmen U2:As is U1 bul W/ penmeter sealed (inoperable door) - STC=PO

Figure 138 Sound reduction index curves for panel U1 and U2 in Table 73 [248].

m

80

v 70 ~-

ui 0

J

60

-.

50 40 30

.........;.;.

.... "

....

.F

-:'

...... - -' ./ ,." ,-, ,/

.

~

" "

2.-

-.

...>. Y

I

D

C 3

53

07 100

1000

10000

Frequency, Hertz Door: Untreated Hollow Core DoorVs. Lead Sheet Lined WoodDoors With Low DensityAnd High Density Fiberglass Insulation Core Material

-Specimen U2:Hollow core door - caulked perimeter- STC=2O

""_

............

Specimen V2: Wood doorW/ 6-pcf fiberglass - caulked perimeter- STC=31 SpecimenW 2 : Wood doorW/ 1.3-pcf fiberglass- cauked penmeter- STC=38

Figure 139 Sound reduction index curves for panel U2, V2, and W2 in Table 7 3 [248].

273

Properties of Lead andIts Alloys 80

70

2 60 S

50

:I 40 E 30 20 c

a

10

v)

0 100 Frequency, Hertz Wood Door With Double Layer,l-psf Sheet Lead And With 6 p c f Fiberglass Core; Tested WithVarious Edge Sealing Conditions -Specimen V1: Comntionaliy h n g (operable door)- STC=15 SpecimenV2: As abow W/ perimetercallked (inoperable door) - STC.31 .........Specimen V3: Mechanical seals top - bottom (L sides (operable door) - STC=27 -. .- .- .. Speamen V4:As in V3 but W/ ttreshold at door bottom (operable -door) STC=31

Figure 140 Sound reduction index curves for panel VI, V2, V3, and V4 in Table 73 [248].

m

80 70

--

60

--

.-Sv) 50

~-

UI

g

-J

.E 40

-

30

~-

gc

a

20 10

-

"_

"""

""

."

.._ _-._ . _ _k_ . 1................. ........................................................

*"

/ ; "

(I."..'.....

-._"

>F.!'

."J "-----

v)

0 1

10000

100

Frequency, Hertz Wood Door With Double Layer, l-psf Sheet LeadAnd With 6-pcf Fiberglass Core;Tested WithVarious Edge Sealing Conditions W1: Comntionalty hung (operable door) STC=16 -Specimen ""_ Specimen W :As abow W/ perimeter caulked (inoperable door) - STC=38 ........... Specimen W3: Mechanical sealslop - bottom d sldes (operable door)- STC=32 -..-. .-. Specimen W4: As in W3 but w/threshold at door bottom (operable door) - STC=35 ~

Figure 141 Sound reductionindex Table 73 [248].

curves for panelsW1,W2,W3,andW4

in

Chapter 2

274 Table 74 Description of Composites of' Glass Fiber Mat with Lead, Lead-Loaded Vinyl, and Lead-Coated Mat [249]. (Courtesy of ILZRO.) Test No.

303 304 305 306 307 12A 12B 12c 12D 12E

12F 12G LM l LM2

material Septa Lead sheet Lead sheet Lead sheet Lead sheet Lead sheet Lead vinyl (ILZRO # l ) Lead vinyl (ILZRO #2) Lead vinyl (ILZRO #3) Lead vinyl (ILZRO #4) Lead vinyl (ILZRO # l ) Lead vinyl (ILZRO #3) Lead vinyl (ILZRO #4) Lead-coated mat Lead-coated mat

Septa wt. (PS0

Total septa wt. (psf)

1

I

2

2 4 2 4 0.143 0.178 0.174 0.193 0.286 0.348 0.386 0.25 0.5

4 1

2 0.143 0.178

0.174 0.193 0.143 0.174 0.193 0.25 0.25

No. of layers 1 1 1

2 2 1 1 1

1

2

2 2 I

2

successiveoscillationsdueto internal friction, and the oscillations are dampedoutwith time. The internal friction is associatedwith different atomic level processes and the nature of the atomic level processes involved depends on the vibrational frequency,composition,andtemperature.The specific damping capacity is the fractional change in amplitude (AEIE) per oscillation, which in a first-order approximation is equal to M I A . Another more commonly used measure of internal friction is the logarithmic decrement, 6, which is defined by

In a system that is subjected to a constant vibration, the stress and strain waves lag behind by a phase angle a.An index rate of internal energy loss is Q", the coefficient of internal friction, which is defined by

The coefficient of internal friction has been measured in both single-crystal and polycrystalline lead and lead alloys. The values of Q" in the case of lead andfew of theleadalloys are summarized in Table 75 [252-2613.

275

Properties of Lead andits Alloys Test # 303

70

65

60

55 50 45

-

40

m

35 30

25 20 15 10 5 n v

10

100

Frequency (Hz) STC Rating 25

1000

10000

Figure 142 Transmission loss in composite with two layers of814 board with one l-psf lead septa (test panel #303 in Table 74) 12493.

fiberglass

Because of the variations in the purity of lead usedin the investigations, Baralis and Tangerini [262] examined the internal friction in a large number of binary polycrystalline alloys prepared from 99.9999% purity Pb and highpurity alloying additives. The impurity concentration in the alloys was less than 2 ppm. The alloying additives examined by them were Bi, Ag, Sb, Cd, Sn, T1, Cu, Ni, Te, As, Al, Li, Ca, and Ba. In addition, they also examined dispersion strengthened lead alloys as listed in Table 76 [262]. Measurements were made using specimenscutfrom0.7-mm-thick sheets. The measurements were made by subjecting the specimens to flexional vibrations, with electrostatic excitation. The vibration amplitude was kept low enough to avoid amplitude-dependent effects. The specimen length ' was determined both by measuring the width of and width were varied. Q.. the resonance peak and by recording the damping of free vibrations of the specimen after discontinuation of excitation [263]. Measurements were made at room temperature (20-25°C) in air. The velocity of sound and the dynamicmoduluswerecalculatedfromresonancefrequency [2641. Figures

Chapter 2

276 70

65 60 55 50 45 40

z-

=35

+

1

30 25 20 15 10 5 0 70

100

Frequency (Hz) STC Rating 29

1000

10000

Figure 143 Transmission loss in composite with two layers of 814 fiberglass board with one 2-psf lead septa (test panel #304 in Table 74) [249].

159 and 160 present the data for Q - ' as a function of concentration and as a function of frequency, respectively [262]. Their work suggested that the value of Q-' is influenced, although only slightly, by the alloying element concentration. A change in trend is generally observed in correspondence with the solubility limit. The value of Q - ' is slightly affected by the variation of frequency within the range 803600 Hz. Q ~ -values ' were not affected by a light prior deformation, vibration amplitude, or the surface conditions. In single-phase alloys, an increase of Q - with varying concentrations is accompanied by a decrease of hardness.

VII.

NUCLEAR PROPERTIES

Lead and some of its alloys are generally the most cost-effective shielding materials to protect against the effects of gamma rays and x-rays [265]. Lead is especially useful when minimum material weight or shielding thickness is needed or when the shielding is temporary or must be portable. In addition

277

Properties of Lead andIts Alloys 70

65

60 55 50

45

40

S 35 l-

30 25 20 15 10

5 0 10

100

Frequency (Hz) STC Rating 32

1000

10000

Figure 144 Transmission loss in composite with two layers of 814 fiberglass board with one 4-psf lead septa (test panel #305 in Table 74) [249].

to the large attenuation coefficient of lead forgamma

radiation and the stability of the nucleus of lead atoms,importantadvantages of leadfor nuclear applications are its ease of fabrication,highcorrosion resistance, good thermal conductivity, ease of decontamination, resistance to radiation damage, wide range of physical properties (with small additions of alloying elements), ready availability (abundance), and eventual ease of recycling. Thus, lead is used extensively in the nuclear-power-generating industry to protect operating personnel, the general public, and the overall environment from the potentially harmful effects of high-level radiation. Hospitals and diagnostic centers use lead bricks and lead sheets for shielding medical personnel and patients from high-x-ray- and gamma-ray-radiation sources used in radiotherapy, diagnostics, and biological research. Lead sheets weighing 2-4 lb/ft’ are often installed in or on walls around x-ray rooms and, frequently, on floors and ceilings as well. Leaded gloves, aprons, and blankets are used extensively in the operation of x-ray equipment and cobalt-60 therapy devices. In industry, radioisotopes are used for film and gamma radireactions, for oil ography to inspect metal welds, for promoting chemical

278

Chapter 2 Test # 306

70

65 60 55

50 45

40

s-

535 I-

30 25 20 15 10

5 0 10

100

1000

10000

Frequency (Hz) STC Rating 29

Figure 145 Transmission loss in composite with three layers of 814 fiberglass board with two I-psf lead septas (test panel #306 in Table 74) 12491.

exploration, for neutron activation and analysis, and for many other purposes. Cobalt-60 is commonly used for gamma radiography because of its highly penetrating gamma rays of 1.17 and 1.33 MeV. Shielding is required not only during the use of these sources but also during shipping and storage. Containers for these purposes are commonly made partly or almost entirely of lead. In many cases, the same containers serve to provide shielding during actual use of the materials. The smaller containers are generally inexpensive and often decontaminated and recycled, and the partially decayed radioisotopes are appropriately discarded. Lead is first in the materials considered in any design for gamma-radiation shielding. When other materials are considered, comparisons are usually expressed in terms of lead because it represents the best practical gamma-shield material.

A.

The Need for Radiation Protection

The term radiation refers to the process by which energy is propagated through space as particles or waves. Radiation may be emitted in the form

279

Properties of Lead andIts Alloys 70

65 M)

55 50

45

40

30

25 20 15 10

5 n

10

100

l000

Frequency (Hz)

10000

STC Rating 38

Figure 146 Transmission loss i n composite with threelayers of 814 tiberglass board with two 2-psf lead septas (test panel #307 in Table 74) 12491.

of electromagnetic waves or photons, or in the form of charged particles such as protons or neutrons moving at high velocities. Ionizing radiations are those that have sufficient energy to interact with matter in such a way as to remove the electrons from the atoms or break molecular bonds. The [266,267]: ionizing radiations commonly encountered are as follows

Alplzu particles: These consist of two protons and two neutrons, like the nucleus of a helium atom. High-energy CY particles are emitted duringradioactive decay of isotopes. Alpha radiation canalso be produced by the acceleration of He ions in particle accelerators. Beta particles: Theseareeitherelectrons with anegativecharge or positrons with a positive charge and are emitted during radioactive decay of radionuclides. Electromagnetic M~(I\VS 01' photons: Of primary concern here are gamma rays and x-rays, which are ionizing and require shielding. Although light waves and radio waves are also electromagnetic,they are generally nonionizing and, as such, do not usually require shielding. Gamma rays areproducedduringradioactive decay and are

Chapter 2

280 70 65

60

55 50 45

B

40 35

k-

30

25 20 15 10 5 0 100

1000

Frequency (Hz) STC Rating 17

10000

Figure 147 Transmission loss in composite with two layers of 814 fiberglass board with a 0.143-psf lead-vinyl septa (test panel #12A in Table 74) [249].

nuclear in origin. X-rays are generated by energy-level transitions of electrons in the atom. Rays of neutrons by themselves are not ionizing radiation, but they can be absorbed by the nucleus of some elements, which may then become radioactive and emit ionizing a,p, or y radiation. Exposure to ionizing radiation at levels above threshold levels causes predictable biological damage in humans and other living organisms which may result in either immediate or latent genetic change or in different forms of latent cancer. Even below this threshold level, there is a finite but very low probability of risk [268].The radiation exposure rate in air or biological matter is measured by the amount of energy absorbed through the ionization process in a unit volume or mass of material. The unit of radiation absorbed dose (rad) refers to 100 ergs of absorbed energy per gram of material. Equal amounts of doses from different kinds of radiation could produce different biological effects. For the same absorbed dose, the damage caused could be different in different organs. A weighting of the radiation dose for the nature of radiation and the type of organ is done to obtain an effective dose equiv-

281

Properties of Lead and Its Alloys Test # 128

70

65 60 55

50 45 40

G y 35 I-

30 25

20 15 10

5 0

100

1000

10000

Frequency (Hz) STC Rating 18

Figure 148 Transmission loss in composite with two layers of 814 fiberglass board with a 0.178-psf lead-vinyl septa (test panel #12B in Table 74) [249].

alent. The unit of effective dose equivalent is rem (Roentgen Equivalent Mammal). Maximum permissible occupational exposures for radiation workers are based on the recommendations of the International Council on Radiation Protection (ICRP) and the U.S. National Council on Radiation Protection and Measurements (NCRP) [269-2711. In the United States, the occupational exposure limits are 5 rem for whole-body exposure, 30 rem for forearms, 75 rem for hands, and 15 rem for skin and various other body organs [271]. For pregnant women, the occupational limit is 0.5 rem (500 mrem) fetal exposure during the entire gestation period. For the general public, the limit is 0.5 rem per year for whole-body exposure. A further principle recommended by the International Commission on Radiological Protection (ICRP) is known by the acronym ALARA (As Low As Reasonably Achievable), which means that exposure should be as much below the foregoing limits as reasonably achievable, taking into account the social and economic factors. As a basis for design of facilities, the U.S. Department of Energy (DOE) specifies 1 rem per year maximum for occupational wholebody exposure and 0.17 rem per year for the general public.

282

Chapter 2

70

65 60 55 50 45

k

40

2% 30 25 20

15 10

5

0 100

1000

10000

Frequency (Hz) STC Rating 18

Figure 149 Transmission loss in composite with two layers of 814 fiberglass board with a 0.174-psf lead-vinyl septa (test panel #12C in Table 74) 12491.

Besides biological damage, radiation exposure may also affect the physical and chemical properties of many materials, such as electronic components or structural materials. Thus, shielding human beings and other materials from the radiation damage is critical. Alpha particles and protons travel only a short distance in air and can be stopped by a single sheet of paper. Beta particles can be stopped by a few millimeters of metal, depending on the energy of the particles and the density of the metal. However, neutrons of high energy, as emitted by some fuels after discharge from a nuclear reactor, travel almost unchecked through most metals. However, hydrogen is effective for slowing down neutrons to low-energy levels, called the thermal region; water and polyethylene are commonly used for this purpose. In turn, thermal neutrons are readily absorbed by many elements; among the most effective are boron, cadmium, gadolinium, and lithium. Neutron attenuation and absorption are accompanied by the emission of energetic photons, so that lead or another gammashielding material is often required in conjunction with a neutron shield. Neutron absorption in the 5yCoisotope transmutes it into “’CO,which decays

Properties of Lead and Its Alloys

283 Test # 12D

70 65

60 55 50 45 40 I

c J

35

30

25 20 15 10

5 0 100

1000

too00

Frequency (Hz) STC Rating 18

Figure 150 Transmission loss in composite with two layers of 814 fiberglass board with a 0.193-psflead-vinyl septa (test panel #12D in Table 74) [249].

with emissions of 1.7- and 1.33-MeV gamma rays. X-rays normally are of lower energy and require relatively less shielding. The higher-energy gamma rays are very penetrating and, in some cases, require more than 8 in. of lead or its equivalent for adequate shielding [265]. Among the alloying elements used in lead alloys, some are prone to gamma-ray emission on the absorption of neutron [265]. Lead-antimony alloys have high tensile strength, hardness, compressive strength, fatigue strength at normal temperatures, and corrosion resistance in most environments, and, in some cases, they form a self-protective, impermeable film even faster than pure lead. Antimony is converted to radioactive forms that emit energetic gamma rays on the absorption of neutrons. Pb-Sb alloys are therefore not suitable for shielding in the presence of neutron irradiation, as the typical Sb content levels are high (about 6%). However, they are satisfactory if used only for gamma shielding. Calcium also emits gamma rays on the absorption of neutrons. However, as only a fraction of a percent is adequate in improving the creep and fatigue resistance of lead, Ca-lead is satisfactory in these applications. Silver hardens lead. It absorbs neutrons and emits strong gamma rays; the

284

Chapter 2

70

65 60

55 50

45

67

40

T)

135 I-

30 25 20

15 10 5 0 100

1000

10000

Frequency (Hz) STC Rating 22

Figure 151 Transmission loss in composite with two layers of 814 fiberglass board with two layers of a 0.143-psf lead-vinyl septa (test panel #12E in Table 74) [249].

amount of silver in chemical lead may be more than is acceptable for some applications, in which case one might use common desilverized lead. Alloys containing 0.5% silver and 2.5% tin, however, have considerably higher fatigue and creep strength than chemical lead at elevated temperatures. Copper and tellurium are used in small quantities and they do not have any problem with regards to neutron absorption. Copper improves the tensile, creep, and fatigue strengths of lead. The solubility is low and amounts greater than 0.06% segregate out. Chemical lead normally has approximately this percentage of copper, which primarily accounts for its fatigue strength being considerably higher than that of corroding lead. Thus, Pb-Cu and Pb-Cu-Te alloys are satisfactory from the view point of neutron absorption. The hardness of lead is increased significantly by the addition of 12% lithium or sodium. At the same time, the density is reduced by 5-10%. One percent lithium-lead has a hardness about four times that of pure lead, as measured by a diamond pyramid test, and a tensile strength of about 50 MPa at room temperature. Lithium and sodium leads must be protected from attack by water, which causes cracking and further increases in volume.

285

Properties of Lead andIts Alloys Test # 12F

70 65 60 55 50

45 40

B

335 l-

30 25 20 15 10

5 n 1

100

1000

10000

Frequency (Hz) STC Rating 22

Figure 152 Transmission loss in composite with two layers of 814 fiberglass board with two layers of a 0.174-psf lead-vinyl septa (test panel #12F in Table 74) [249].

Lithium has the advantage of being a strong absorber of thermal neutrons without a resulting in the emission of gamma rays. Thus, lithium-lead is useful as a component of a combined gamma-neutron shield and effectively reduces the emission of secondary gamma rays.

B.

Forms and Uses of Lead in the Nuclear industry

Lead is available in many forms, including the following: pig lead; sheet, plate, and foil; laminates; plastic composites;lead-cladmetal plate; shot; powder; wool; bricks; putty; waxes; lead epoxies; pipes and sleeves; blankets; andlead glass. A number of fabricated items,suchasvalvesand pumps, are also available. Table 77 provides a summary of the radiationshielding applications of the different forms of lead [265].

C. Shielding Thickness for Gamma Radiation Shieldingcalculations,except in simplecases,require the services of an expert in the field. Complications introducedby irregular geometry, apertures

286

Chapter 2 Test # 12G

70

65 60 55 50 45 -40

m U ,35

+ 30

25 20

15 10

5 0 100

1000

10000

Frequency (Hz) STC Rating 23

Figure 153 Transmission loss in composite with two layers of 814 fiberglass board with two layers of a 0.193-psf lead-vinyl septa (test panel #12G in Table 74)

12491.

and crevices, heterogeneous or composite shields, andscattering of radiation by the shield itself (and by the surroundings) usually necessitate the largescale numerical computation using computers. Conservative assumptions are made to allow for uncertainties in the data and for approximations in the computations so that observed radiation levels are commonlylowerthan calculated levels, sometimesbyafactoras large as 10 in complexcases with thick shields. The accuracy of calculation is of particular concern for shipping containers, where it is important to maximize the ratio of payload to gross weight. Gamma rays or photons are emitted uniformly in all directions from eachpoint in aradioactivesource,andspreadout in amanner inversely proportional to the square of the distance. Thus, imposing distance requirements is one effective way of controlling radiation exposure. Provision of shielding and limiting the time of exposure are other methods of control. Photons interact with matter in three principal ways: 1.

Pair P~.oduction.A process in which the gamma rayis usedfor the creation of a positron-electron pair is created in the vicinity

287

Properties of Lead and Its Alloys Test # LM1

70

65 60 55 50 45 40

6-

2 35 + 30 25 20 15 10

5

0 10

O0

Frequency (Hz) STC Rating 20

1000

10000

Figure 154 STC transmission loss in composite with two layers of 814 fiberglass board with one layer of lead mat septa (test panel #LMI in Table 74) [249].

of a nucleus. The excess energy appears as the kinetic energy of the particles created. However the positron will be quickly annihilated, producing two photons of 0.51 MeV each. 2. Compton Effect. The photon is deflected in its path and reduced in energy. Many of these lower-energy scattered photons emerge from the shield and account for most of the “buildup” factor described later. 3 . Photoelectric. Egect. The photons are, in effect, absorbed by atoms, by the excitation of electrons to higher-energy levels. The electrons in the excited state emit weak x-rays on subsequent transition to lower-energy levels. The probability of an interaction (or collision) within a given distance is defined by a material property called the linear absorption coefficient, designated as p. The fraction of photons escaping collision in traveling through a shield is given as e‘-”’ or c‘~”‘)“‘) , where t is the shield thickness in the direction of travel; the term p/p is called the mass absorption or mass attenuation coefficient, where p is the material density. The reciprocal of p,

288

Chapter 2

Figure 155 STC transmission loss in composite with two layers of 814 fiberglass board with one layer of lead mat septa (test panel #LM2 in Table 74) (2491.

called the relaxation length, is the distance necessary to attenuate the radiation by a factor of E , or about 2.718, neglecting buildup. The relative frequenciesofthese interactions depend on the atomic number Z , which is the number of protons in the nucleus of the material through which the photons are passing. For lead and uranium, pair produc5 MeV, photoelectric tion is dominant for photonsenergiesaboveabout effect below about 0.5 MeV, and Compton effect in the intermediate energy range. Figure 161 shows the mass attenuation coefficient (p/p) for leadfor each of the three types of interaction, and the total [265]. Figure 162 gives the values of the total coefficient for several different materials as a function of photon energy [265]. Units used here are cm" for F and &/cm' for p. Table 78 gives the values of the mass attenuation coefficient (p/p) for lead for each of the types of interaction, and for the total attenuation due to all interactions (272,2731. The required thickness and weight of lead are less thanforothercommonlyusedshieldingmaterials(excepturanium) by a large factor at gamma energies below about 1 MeV, as shown in Table 79 [265].As mentioned earlier, lead is not effective shielding material for neu-

289

Properties of Lead andIts Alloys

Figure 156 STC ratingversuslead layer composites (2491.

septaarealdensity

plot for lead-mat-based

trons (Table 80). In the presence of neutron irradiation, lead is used in conjunction with a moderator and absorber for neutrons. Heat is generated in the shield as a result of the photon interactions. For small Curie sources, the heat is usually of minor concern; but for megaCurieamounts, as withspentfuel, dissipation ofheat is amajorconsideration. In practice, radiation sources of various shapes are encountered. Measurements and calculations of radiation attenuation are often made for point or surface sources and this allows measurement data to be converted for use with other shapes [267,274,275]. In fairly straightforward cases, the point kernelmethod is used to evaluate the shieldingthicknessneeded. In this, radiation received at a detector from distributed sources is treated as a summation of radiations received from an equivalent number of point sources. The source strength I , is expressed in mrem/h at a unit distance for unit volume of source. For each location (point) in the radiation source, the the corresponding radiation level I, for areceptor at somepointoutside shield is given by

Chapter 2

290

0.0

0.1

0.2

0.4

0.3

0.5

LEAD VINYL SEPTA WT, PSF

Figure 157 STC rating versus lcad septa areal dcnsity plot for Icad-vinyl-shccthosed layer composites [ 2491.

where B is the dose buildup factor and is the distance from the source to the receptor. The value of I, for 1 Ci of the source is given by I, (mrem/h at l cm) = K X 10" FE; F is the fraction of disintegrations yielding photons of energy E (MeV). One Curic of radioactive material, by definition, decays a t the rate of 3.7 X IO"' disintegrations per second. Values of K are given in Table 81 [265]. Some radionuclides emit photons of many different energies; those with very small values of E may be neglected, and, often, thc others can be grouped so as to simplify calculations. Also. the decay process may include it chain of several different radionuclides which must be considered. Cesium- 137, which because of its half-life of about 30 years is of concern in the disposal of high-level waste, does not emit gamma rays, but its short half-life daughteremitsgamma rays of about 0.7 MeV. Mixed fission products emit a wide range of gamma rays, and the emissions change with time. In many cases, the source may be considered a point or a line rather receptor, than a volume. If several materials intervene between source and I'

Properties of Lead andIts Alloys

29 1

Figure 158 STC rating versuslead septa arealdensity plot for lead-sheet-based layer composites [249].

the weighted average values of B and p. may be used. The source itself may be large enough to provide some shielding; this is known as self-absorption. The total externaldoserate is obtained by integrating Eq. (37) over the entire source. For a relatively thin layer of attenuating material, the probability of scattered radiation particle reaching the detector are small. However, when the shielding material thickness increases, some particles that have suffered two or more scattering collisions may reach the detector. The total fluxis thus greater than the unscattered flux received. The buildup factor is a term introduced to take into account the contribution of scattered radiation to the total radiation flux at the detector. The buildup factor B is dependent on the p ) as well as the initial photon energy. number of mean freepaths(or Different empirical formulas have been used to express B as a function of p.f for a given energy, so that the integration can be performed. The Berger formula, which is described in various shielding manuals, is one of the more useful and accurate formulas.

Chapter 2

292

Table 75

Experimental Values of Q

Alloy

I

in Single-Crystal and Polycrystalline Lead

Q ’

Frequency

Pure polycrystalline lead

16-2000 H z

0.35 X 10-’-4 X 10

17-2X kHz 4-64 kHz

0.2 X 10-’-0.8

Single-crystal lead Pb-10% Sn alloy

Few hundred

1 X 10

Single-crystal Pb0.033 wt.% Sn

30 k H z

Single-crystal Pb0.0092 wt.% Cd Single-crystal Pb0.0022 wt.% In Single-crystal Pb- 1.2 wt.% In (unetched surface) Single-crystal Pb- 1.2 wt.% In (chemically etched surface)

30 k H z

’

X 10 0.2 X 10-’-0.7 X 10

Hz 30 kHz

Single-crystal Pb0.035 wt.% Bi

Ref.

’

’

0.1 1 x 1 0 ? (-deformation of 10 ’, RT) 0.22 x 10 ’ (-deformation of 10 ’, RT) 0.9 X lo-’ (-deformation of 10 ’, RT) 2 X 10 ’ (-deformation of 10 ’) 3 x IO-“ (--deformation of 10 ’)

4 kHz 4 kHz

3

4 kHz

‘’

X 1 0 ~ (-deformation

252-254 255, 256 235, 258-26 1 257 260

260

260 26 1 26 1

26 I

of lo-’)

Table 76 Composition of Dispersion-Strengthened Lead Alloys referred to in Figure 160a [2621 Concentration (wt.%)

PbO cu Bi Sn Sb Ag

MD 104

MD 201

0.7 0.0 I 0.03

0.8 0.0001 <0.005

0.02

0.0 1

0.003 0.005

0.0003

-

BX 1.1

0.05 0.03 0.05 0.01 0.0012

BXL

AX

0.8 0.003

0.55 0.03

0.002 0.0 15 0.0008

0.02 0.0 15 -

0.002

293

Properties of Lead andIts Alloys

c

A

-F

o

o Pb-Te

A

woo1

Pb- AI

mm

am

%C0'

Pb-Ba

1

10

(c) Figure 159 Q I as a function of alloying element concentration for lead and alloys prepared from 99.9999% Pb and high-purity alloying additives. Totalimpurity in the alloy <2 ppm [262]. (Courtesy of Lead Development Association, London.)

294

Chapter 2

o Pb -Cd o Pb-Ca

Values of B normally used in point kernel calculations are based on a point isotropic source in an infinite medium. Table 82 lists certain of these values 1265,273,2761. It is seen that for thick shields, more than 90% of the calculated radiation may be the result of the scattered protons. The assumption of an infinite medium should be reasonably accurate when the receptor ison or near the outer surface of the shield. However, the calculations tacitly assume that the scattered photonsleave the shield with such angular distribution that the attenuation by distance is the same as for the primary photons. Theoretical considerations lead to the conclusion that this is a conservative assumption, and actual measurements with casks of spent fuel indicate that this item alone may result in an overestimate of radiation level by a factor as large as 2 at a distance of 2 m ("6.6 ft). Various computer codesare used for shielding calculations, some based on the point kernel method, some on a discrete ordinates method, and some

Properties of Lead and Its Alloys m.

295 m3

m2 'U

'U

Figure 160 Q ' :IS a function o f frequency for lead and nlloyspreparedfrom 99.9999%)Pb and high-purity alloyingadditives 12621. (Courtesy of LcadDcvclopment Assoclation, London.)

on the "Monte Carlo" method. The choice depends largely on the geometry and the materials involved. Some of the methods of calculation and an ex'rtreers, . tensive bibliographyare given in Rccrctor Shielding jbr Nlrcleur EII~C, edited by N. M. Schaeffer 12731 and other references [272,274-2761. A few results based on the pointkerneltechnique and idealized gethe ometries are given in Figures163 and 164 [265]. Figure163shows required thickness of shield to reduce the radiation dose rate by a factor of 10 for various materials, as a function of gamma energy. Figure 164 gives the required lead shield thickness for specified external radiation levels, for point sources of cobalt-60 and cesium-137 from 0.1 to 10,000 Ci. A flat slab shield is assumed,with the source in contactwith the innersurface.The radiation levels shown are regulatory limits for transportation.

D.

Sources of Radiation in the Nuclear Fuel Cycle

I n a nuclear reactor, fission of uraniurn-235orplutonium-239producesa large number of isotopes of elements with a smaller atomic number. Many

296

Chapter 2

Table 77 Forms of Lead Used for Radiation Shielding [265].(Courtesy of Lead Industries Association, New York.) Form Pig lead Lead sheet, slab, plate Lead shot Lead wool Lead epoxy Lead putty Lead brick Lead pipe Lead-clad tubing Lead-lined/clad pipe Lead sleeves Lead powder Lead glass Lead-polyethyleneboron Lead laminates

Applications Casting; shipping containers Permanent shield installations Where solid lead is impractical due to location, shape, and accessibility Filling deep cracks in a radiation barrier In-the-tield crack tilling/patching Nonhardening, temporary seal or patch Convenicnt. easily handled; may be moved and reused Shielding of radioactive liquids Shielding of radioactive liquids Shielding of radioactive liquids Shielding of ducts and pipes carrying radioactive materials Dispersed in rubber o r plastic for flexible shielding; also mixed with concrete and asbestos cement Transparent shielding Combined gamma, neutron, and thermal neutron barrier material Doors, partitions, walls, enclosures

of these isotopes may be unstable and decay with a half-life of few seconds to several years. Thus, in the reactor core, very high levels of alpha, beta, gamma, and neutron radiation with a wide distribution in their energy levels exist. This mixture of isotopes is known as mixed fission products (MFP). For many purposes in regulations and operational controls, MFP is treated as if it were a single radionuclide. Small amounts of radionuclides with atomic weights greater than 239 are also produced (some intentional and some unavoidable) by neutron absorption. Principal among these from a shielding standpoint is curium-244, which emits neutrons because of spontaneous fission of some of the atoms. Neutron absorption also causes reactor components and piping to become radioactive. However,somemetals,includingzirconium,havevery little affinity for neutrons; for this reason, together with otherwise suitable properties, zirconium is used as the cladding material for fuel elements in nuclear power reactors. Radioisotopes are sometimeschemicallyseparatedfrom the fission products; for example, strontium-90 and cesium-l37 have been recovered. More commonly, radioisotopes for research, medical, and industrial uses are

Properties of Lead and Its Alloys

297

Figure 161 The mass absorption coefficients for lead 12651. (Courtesy of Lead Industries Association, New York)

298

Chapter 2

1.0 0.8

0.6

0.4

0.2

v)

m 0.06

0.04

0.02

0.01

Figure 162 A comparison of theInassabsorptioncocfticicntsfor lead. uranium, water. and concrete [26SJ. (Courtesy of Lead Industries Associatlon, New York.)

produced by neutron bombardment of target materials in nuclear reactors or i n machines called particle accelerators. Among those requiring a significant amount of gamma shielding are sodium-24, iron-59, cobalt-60, iodine- 13 l , and iridium-192. Energies above 1 MeV usually require a substantial thickness of the shield; below about 0.5 MeV, relatively thin shields suffice. The most energeticparticles normally encounteredare the 7.1-MeV rays from nitrogen-16. Mixed fission products emit fewgamma rays greater than 2

Table 78 Mass Coefficients (cm'/g) for Lead [273]

~~

~

~

~

L,,,

0.0 1 0.01304

0.0456 0.0549

0.000855 0.00133

L,,

0.015 0.015200

0.0596 0.0602

0.00165 0.00168

L,

0.015861

0.0616

0.00179

0.02 0.03 0.04 0.05 0.06 0.08

0.0695 0.0828 0.09 10 0.0956 0.0983

0.0025 1 0.00430 0.00608 0.00770 0.00922 0.0117

0.100

~

~~

124 61.0 158 110 107 148 132 153 83.1 28.5 13.2 7.21 4.39 1.97

I24 61.0 113 82.8 80.8 109 98.8 114 66.3 24.7 11.9 6.63 4.10 1.87

~

I24 61.0 158 110 107 148 132 153 83.1 28.6 13.3 7.30 4.48 2.07

124 61.0 158 110 107 148 132 I53 83.1 28.5 13.2 7.21 4.39 1.99

I24 61.0 113 82.8 80.8 109 98.8 114 66.3 24.7 11.9 6.63 4.10 1.88

0 0 0

K

0.088004

0.100

0.0126

0.1 0.15 0.2

0.0997 0.0965 0.09 13 0.08 14 0.0738 0.0677 0.0631 0.0555 0.0500 0.0407 0.0349 0.0274 0.0229 0.0198 0.0175 0.0143 0.0 122

0.0138 0.0175 0.0197 0.02 19 0.0225 0.0228 0.0227 0.0220 0.0208 0.0191 0.0173 0.0141 0.01 19 0.0103 0.00901 0.00718 0.00593

0.3 0.4 0.5 0.6 0.8 1

1.5 2 3 4 5 6 8 10

0.00159 0.00500 0.01 15 0.0168 0.0213 0.0248 0.0305 0.0360

0.000480 0.00229 0.00692 0.01 I 2 0.0148 0.0176 0.0217 0.0254

1.51 7.30 5.23 1.80 0.843 0.289 0.141 0.0823 0.0538 0.0285 0.0180 0.00858 0.00523 0.00282 0.00 I88 0.00 139 0.00108 0.000750 0.000570

1.44 2.30 2.08 1.08 0.590 0.23 1 0.119 0.0724 0.0483 0.0263 0.0 169 0.00823 0.00509 0.00276 0.00 185 0.00137 0.00107 0.000744 0.000567

1.61 7.38 5.32 1.90 0.933 0.369 0.215 0.150 0.177 0.0840 0.0680 0.0509 0.045 1 0.04 16 0.04 16 0.0424 0.0433 0.0456 0.0488

1.52 7.33 5.26 1.82 0.863 0.31 1 0.164 0.106 0.0773 0.05 15 0.0401 0.0305 0.0288 0.0299 0.0326 0.0352 0.0372 0.0407 0.045 1

1.45 2.31 2.09 1.10 0.610 0.253 0.142 0.0951 0.0709 0.0483 0.0378 0.0278 0.0247 0.0238 0.0250 0.0265 0.0277 0.0297 0.0320

Nore: Coherent scattering is excluded and Compton coefficients are for bound electrons. Compton (c), pair production (pp). Compron absorption (Ca), photoelectric (pe), and pair-production absorption (ppa) mass coefficients have been corrected for bremsstrahlung losses. Their total is thus I*. /P.

5a~ ‘0,

?!

ru

301

Properties of Lead and Its Alloys Table 79 Comparative Thicknesses and Weights of Materials for Gamma Shielding 12651. (Courtesy of Lend Industries Association, New York.) MeV

0.2 T W 0.4 T W 0.7 T W I T W 2 T W 4 T W 7 T W 10 T W

Lead

Water

1 1

140 13 47 4. I 22 1.9 16 1.4 12 1.04 14 1.2 19 I .7 27 2.4

I 1 1

1 1 I 1 1 1 1 1 1

1 1

2.5 Concrete 57 13

I9 4.2 9.5 2.1 7.1 1.6 5.8 1.3 6.9 I .5 9.9 2.2 I4 3.1

Steel

6.2 Lead glass

Uranium

10 7.2 4.7 3.3 2.8 1.9 2.2 I .5 I .7 I .2 1.8 1.3 2.2 1.5 2.6 1.8

1.7 0.92 1.9 1.04 1.8 1.02 I .8 0.97 I .6 0.88 1.6 0.86 1.6 0.87 1.7 0.93

0.4 1 0.68 0.43 0.72 0.47 0.78 0.49 0.8 I 0.50 0.83 0.55 0.90 0.54 0.89 0.53 0.87

Note: The values shown are based oil ii factor of 10 attenuation and would differ slightly for other factors because of variations in buildup. T and W in the table represent thickness and weight, respectively. Values for lead are taken as unity.

MeV, yet many in the range 1-2 MeV. All phases of the nuclear fuel cycle have radiation hazard problems. Obviously, most of the stronger radioactive isotopes are generated by nuclear reactors. The nuclear fuel cycle includes the following:

--

Mining, milling, and refining of uranium Enrichment to increase the percentage of uranium-235 Fabrication of fuel elements Irradiation of fuel in nuclear reactors Reprocessing of irradiated fuel to recover plutonium and remaining uranium Disposal of low-level waste from various steps in the fuel cycle Disposal of high level waste, either as unprocessed spent fuel or as a solid incorporating the radioactive material discarded from reprocessing

Gamma-shielding requirements are minor in mining and milling, and also in enrichment and fuel fabrication when fresh uranium is used. Recycled uranium, if reprocessing is resumed in the United States, may accumulate

Table 80

Thermal Neutron Capture Cross Section and Gamma-Ray Emission in the Energy Range 0- I I MeV per 100 Captures for Pb and Its Alloying Elements: the Data Correspond to the Most Common Isotopes of These Elements [272]

Photons/100 captures for energy ranges (MeV) Z

Element

3 13 20 26 27 28 29 30 47 48 49 50 51 52 82 83

Li Al Ca Fe Co Ni Cu Zn Ag Cd In Sn Sb Te Pb Bi

"For 3-5 MeV. hFor 5-7 MeV.

U".7

33 mb 235 mb 430 mb 2.62 b 38.0 b 4.6 b 3.85 b 1.1 b 63.0 b 3620 b 198 b 625 mb 5.7 b 4.7 b 170 mb 34 mb

0- 1

1-2

2-3

3-4

12.42 27.5 1 24.0 I 27.83 93.74 26. I6 8 1.75 16 68.3 1 103.99 33.57 14.1 150 >58 0 0

4.9 1 8.77 93.49 24.76 20.54 6.59 6.02 63.86 44.12 37.27 106.96 6 1.46 99

89.33 3 1.25 5 1.87 9.54 15.94 6.05 4.57 5 1.02 78.09 98.08 100.67 105.42 58

0 26.02 17.1 I 11.32 17.84 3.65 4.96 28.37 42.4 1 59.40 37.58 59.74 38"

0 0

0 0

0 0

4-5 0 37.09 23.03 11.22 15.66 3.70 10.10 21.16 25.12 30.72 18.27 32.28

0 111.70

5-6

6-7

7-8

8-9

9-10

10-11

0 8.12 12.54 10.93 33.62 7.45 10.19 19.64 19.08 24.32 7.40 18.01 12h

1.07 10.29 43.84 10.12 34.67 17.04 16.2 1 18.20 5.93 5.58 0.93 9.94

4.02 38.74 2.16 58.86 11.39 14.04 64.87 18.70 1.74 2.62 0

0 0 0 0.82 0 58.99 0 1.30 0 0.81 0 1.1

0 0 0 4.15 0 0 0 1.11 0 0.29 0 0.29

0 0 0 0.1 1 0 0 0 0 0 0 0

5.04 0

94.06 0

0 0

0 0

0 0

6.18

0 0

0

3 P)

3

4

h)

303

Properties of Lead andIts Alloys Table 81 Value of K in the Formula I = K X I O h FE (mrem/h at I cm/Ci) [265].(Courtesy of Lead Industrics Association. New York.)

E (MeV)

K

0.2 0.4

5.5

0.6

6. I 5.1,

6.1

0.8 1 .S

5.7 5.3

2

4.8

3 4

4.2

I

3.8 3.4 3.1

6 I0 ~~

~

~

enough radioactive impurities to require removal by additional processing or shielding during enrichment and fuel fabrication. Fuel must be removed is consumed. Much of the '''U and from the reactor before all of the 235U most of the 'jXU still remain i n the burnt fuel element. Decay of the fission productscauseshighgamma-radiation levels andthe generation of much heat. The spent fuel is stored in water-filled basins for several months before transfer to a reprocessing plant, or for several years before removal to storage elsewhere or for disposal as high-level waste. Nuclear reactors and reprocessing facilities have many different applications for lead shielding. Fixed or permanent shielding during initial construction, when space and weight are not critical. is commonly concrete and masteel. Applications for lead includesuchitemsascharge-discharge chines, reactor room and hot cell doors, shielding for piping and instruments, shielding of turbines, walls, hot cells, and containers for handling and storage of exhausted resin beds. Spent fuel can be chemically dissolved and processed to recover uranium and plutonium. The fission products, along with the dissolved cladding materials, are stored in large underground tanks in slurry form. Storage of this high-level waste for several years is necessary before it is feasible to prepare the material for disposal in a repository. Largevolumesofwaste containing some transuranic isotopes, and thus known as TRU waste, result from reprocessing; this waste has relatively little heat generation or gamma radiation.

Chapter 2

304

Table 82 Dose Buildup Factor for PointIsotropic Sourcc [265,273,2761. (Courtesy of Lead Industries Association, New York.)

7 14.3 Water

5.14

Iron

Lead

Uranium

0.5 1.0 2.0 4.0 6.0 10.0 0.5 1.0 2.0 4.0 6.0 10.0 0.5 1.0 2.0 4.0 6.0 10.0 0.5 1.0

2.0 4.0 6.0 10.0 3.940.5 Concrete 1.0 (ordinary, 2.33 density) 2.592.0 4.0 6.0 10.0 ~~

2 3.71 2.77 2.17 1.9 1.63 3.09 2.89 2.43 1.94 1.72 1.42 1.42 1.69 1.76 1.56 1.40 1.23 1.30 1.56 1.64 1.50 1.36 1.20

3.18 2.14 1.94 1.74

20 IO 7.68 4.88 3.34 2.76 2.19 5.98 5.39 4.13 3.03 2.58 1.95 1.69 2.26 2.51 2.25 1.97 1.58 1.48 1.98 2.23 2.09 1.85 1.51

8.58 6.22 4.49 3.35 2.90 2.50

38.8 16.2 8.46 5.13 3.99 2.97 11.7 10.2 7.25 4.91 4.14 2.99 2.00 3.02 3.66 3.61 3.34 2.52 1.67 2.50 3.09 3.2 1 2.96 2.26 18.9 12.2 7.74 5.26 4.38 3.64

15

178 77.6 50.4 27. I 19.5 12.4 9.97 6.94 7.09 5.18 4.90 3.72 35.4 19.2 28.3 16.2 17.6 10.9 11.2 7.1 1 9.89 6.02 7.54 4.35 2.65 2.27 4.8 1 3.74 4.84 6.87 9.80 5 .44 13.8 5.69 4.34 12.5 1.85 2.08 2.97 3.67 5.36 3.95 8.01 4.66 4.80 10.8 3.78 10.5 69.1 33.7 19.6 35.0 18.0 11.4 10.6 7.25 8.33 5.87 4.79 6.69

334 82.2 27.7 12.9 8.85 5.98 55.6 42.7 25. 1 16.0 14.7 12.4 (2.73) 5.86 9.00 16.3 32.7 39.2 (6.48) 12.7 23.0 28.5 I l9 53.6 25.1 13.9 10.7 8.57

~

"Values of B as a function

E.

B"

E (MeV) 4

01 pt.

Lead for Transport and Storage Containers

Shielded containers are used for shipping radioisotopes, spent fuel, and lowlevel waste. Many more will be needed for high-level waste. Spent fuel may be stored in casks for several years before disposal, either by reprocessing or by burial in a repository.

Alloys Properties its andof Lead

305

60 40

20

10

6

1

0.6 0.4

0.2

0.1

Figure 163 Thickness of materials to reducegamma radiation by factor of 10 (buildup included) 126.51. (Courtesy of Lead Industries Association, New York.)

Chapter 2

306

9

7

A

3

2

0.1

1

100

10

Curies

1000

10.000

Figure 164 Thickness of lend for specified external radiation levels (point source in contact with inner surftcc) (265I. (Courtesy of Lead Industries Association, New York.)

Two lypes of packaging are described: ( I ) Type A, which must satisfy specified performance requirements under adverse conditions of “normal transport,’’ but are not designed to withstand accident conditions, and (2) Type B, which are so designed that even under quite severe accident conditions of impact and tire m y escape of radioactive material would not exceed certain small limits and the external radiation level would not be a serious hazard. For radioactive materials that are also tissile, further requirements are iniposed to provide assurance that criticality (i.e.. a nuclear chain reaction) will not occur.

1. Low-Level Waste Class A wastes are relatively innocuous and need not be in a stable form. They may consist, for example, of contaminated clothing, laboratory sam-

Properties Its andof Lead

Alloys

307

ples, orscrapmetal that hasbecomemildlycontaminated.Amongother things, they may contain up to 0.8 Ci/m3 of carbon-14, 700 Ci/m' of cobalt60, or 40 mCi/m3 of strontium-90. Class B wastes must be physically stable or in a container designed to provide stability for 300 years or more. Also, they must beof a type that within 100 years will decay sufficiently to reduce the hazard to an acceptable level if persons might then occupy the site. Examples are wastes containing up to 150 Ci/m' of strontium-90 or an unlimited concentration of cobalt-60. Class C has the most rigorous requirements, including, among other things, the necessary stability and a cover of at least S m of soil or else ;I barrier such as concrete designed for a n effective life of at least S00 years. Examples are wastes containing up to 8 Ci/m' of carbon-14, 7000 Ci/m3 of strontium-90, or 0. I Ci/m.' of p~utonium-239. Casks for low-level waste may be either Type A or Type B. But most casks in use for low-level waste are Type A. However, several Type B casks are in service for suchitemsas radioactive scraphardwareanddepleted nuclear therapy sources. The need for Type B casks is likely to increase as a result of maintenance and modification of nuclear power plants and the growing use of radioisotopes in medicine and industry.

2.

High-Level Waste

The principal high-level wastes are the fission products now stored in underground tanks. Fuel cladding and hardware andcertain reactor components also qualify as high level waste. Disposal techniques for high-level defense waste are to concentrate it by evaporation and incorporate it in a borosilicate glass in metalcanisterswhich willbe shipped to a repository. Spent fuel may eventually be disposed of as high-level waste, as there are, at present, no plans for reprocessing the fuel from power reactors. The waste may be vitrified and solidified i n a stainless-steel canister 1 ft or more in diameter and perhaps 10 ft long; this is then inserted in a cylindrical sleeve of lead about 4 in. thick and the entire unit is encased in a titanium shell. Power reactors in the UnitedStates are dischargingapproximately 3000 metric tons of uraniuma year. Onerepositorycask for a spent-fuel 10 tons. Ten years of storage exclustorage cask can accommodate about sively in casks would require 3000 casks, each of which could use up to 40 tons of lead or a total of 240 million pounds of lead.

This Page Intentionally Left Blank

Processing of Lead Products

The various lead-alloy-product shapes commonly used include sheets, rods, tubes, strips, wire, and complex-shaped bulk components.All the four major manufacturing processes, namely forming, casting, machining, and joining, are used in the production of engineering components made of lead alloys. The ease of production of the different forms (or shapes) of lead using one or more of the above processes make the processing costs extremely IOW and the use of lead attractive. The forms in which lead is used is classified into (1) basic lead, (2) supported lead, (3) bonded lead, (4) brick/lead, and (5) lead coatings [61]. Basic lead is the type of component form where lead is not mechanically supported by other materials and the mechanical strength and corrosion resistance of the component arises primarily from lead alloy. Supported lead is the form in which lead is reinforced by mechanically fastening lead to the supportive material, usually steel. Bonded lead is metallurgically joined laminates of lead and another metal, usually steel. Brick/ lead is a combination of an outer supporting structure of steel or concrete, a lead membrane, and an innerlayer of acid-brick, tile, or borosilicate glass. Lead coatings are thin films of lead that are applied to provide corrosion resistance and differ from supported or bonded lead mainly in its thickness. The processing of these different forms, except the coatings, involves one or more of the four basic manufacturing processes, namely casting, forming, joining, and machining. As discussed in Chapter 2, the face-centered-cubic structure and the relatively low melting point cause lead and lead alloys to be soft and ductile at room temperature. Low recovery and recrystallization temperatures allow lead and lead alloys to be formed without significant strain hardening during the forming operation, obviating the need for any intermediate process an-

309

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310

nealing. The primary forming processes commonly used in the case of lead alloy products are rolling and extrusion. Other forming processes that are used include stamping and die cutting of lead sheets. This section presents a description of these forming processes and their use in processing lead alloys. The low melting temperatures of lead alloys make casting an easy and attractive process in the manufacture of slabs, billets, andcomplex shaped parts. The different casting processes commonly used are sand casting, pressure die-casting, gravity die-casting and continuous casting. Commonly used casting alloys and the processes used in the production of these alloy castings are discussed in detail in this section.Welding,soldering, fastening, thin film coating, as well as the machining of lead alloys used in the production of engineering shapes are also discussed in detail.

1.

MELTING AND CASTING OF LEAD ALLOYS

The casting process involves meltingof lead alloy, pouring the molten metal into a mold cavity patternedafter the part to be made, allowing it to solidify, and removing the metal from the mold. It is a versatile process that allows near-net-shapeproduction of complex-shaped parts andaccommodatesa wide range of sizes and production quantities. Casting sizes varying from a fraction of a gram to several tons can be obtained. Lead and lead alloys are cast in a wide range of shapes that include pumps, valves, filter grids, pipe, vessels, battery grids, pipe flanges, lead shot, nuclear shielding components of complex shapes, and thin lead sheets.

A.

Melting

Melting of lead is usually carried out in oil- and gas-fired furnaces as well [2]. Capacities vary widely as in electrically heatedlead-meltingfurnaces 60 MTdepending on the productbeingproduced. from 1 to asmuchas Figure 1 shows a multizone electrical lead pot furnace with a capacity of 18 MT and 140 kW [277]. No flux is used during the melting of lead and lead alloys. With high-melting-point alloying elements such as Cu, Te, Ni and Ca, hardener master alloys are used for alloying purposes. In the case of alkali and alkali earth elements that easily oxidize, the use of hardener master alloys minimizes loss by burningoff,segregationasPb,Ca,and drossing of Pb and Ca[85].Melting is usually carried out in iron-based alloy pots. These pots may be made of steel, gray cast iron, or high-temperature Fe-based alloys with no or low nickel content. The oxidation resistance, resistance to liquid-metal embrittlement, and resistance to creep are the factors that need to be considered in the selection of steel used and its

Processing Products of Lead

311

-.Figure l A multizoneelectrical lead pot furnace with acapacity of 18 MT and 140 kW [277]. (Courtesy of H. Follke Sandlin AB, Sweden.)

microstructural state. The lead alloys are emptied from the melting pot by pumps, by siphons, and by discharge outlets at the bottom. The reactionsof iron with PbO, with oxygen dissolved in lead, and with alloying elements in solution such as antimony or tin could result in wear of the crucible. With increasing temperature, (1) distortion of the crucible due to creep and (2) resistance to liquid-metal embrittlementneed to be considered. At very high melt temperatures, Cr-MO-V steels and other heat-resistant steels with no or low nickel contents have been used. However, such high melt temperatures are not used during the casting of lead alloys. In air, molten lead becomes covered with PbO with the oxidein contact with lead having pseudo-tetragonal (red) and the layer facing air having a rhombicstructure(yellow)[2,278,279].The (001) plane of theoxide is parallel to the metal surface. The transition temperature from red to yellow oxide is 486°C. However, below this temperature, yellow oxide can form in a metastable manner and transform to the red form with time [280]. The lead oxide also has been found far above the transition temperature up to 750°C [278].

Chapter 3

31 2

The formation and growth of oxide layers on lead melts is influenced by impurities and alloying elements in the lead, agitation of the melt, and duration of exposure to air. The oxidation of 99.999% lead at rest in the temperaturerange350-650°Cfollowsaparabolictime law, AM, = k d , where AM,is the increase of weight, t is the time, and k is the rate constant 1231. Figure 2 shows the weight increase of lead melt with time at 350"C, 400"C, and 450°C [280]. As the volume of the oxide formed is greater than volume of metal from which it formed (Pilling and Bedworth ratio = 1.26), a complete coverage of the metal should occur [281]. The growth of the oxide film on lead alloys takes place by the migration of metal ions from the melt through the oxide layer and reaction with the oxygen of the air. The parabolic oxidation kinetics suggests that the rate-controlling step in the oxidation of lead melts is the diffusion process in the slag. A linear dependence of oxide layer thickness on timemayalso be observeddueto the cracked or loosened condition of the dross. The cracks permit immediate access of air to the surface of the melt. Such cracked or loosened conditions of scale are expected due to local overheating of the melt surface by spontaneous oxidation of impurities with a high affinity for oxygen (Li, Na, Mg) or deposits of oxides of alloying elements (CaO, CdO) on the grain boundaries of the PbO crystals [280]. Secondary reactions such as the oxidation 500°C can lead toa of PbOtoPb30, in the temperatureregionaround deviation from parabolic growth. The rate of diffusion of lead ions in Pb,Od

8

I

l

I

I

N

9 6x D l

0

20

40

60

80

100

Time (h) Figure 2 The oxidationkinetics in 99.999%lead [280]. (Courtesy of Dr. S. A. Hiscock.)

at

350"C,400°C and 450°C

Processing of Lead Products

31 3

is lower than in PbO, so that the formation of Pb.304leads to a reduction of the rate constant [280,282]. At temperatures up to 400"C, the oxidation rates of spectroscopically pure leadis muchlowerthan thatin many lead alloys [278,279]. This is attributed to the low defect concentrations in PbO formed and the consequent low diffusional rates. The high-purity lead maintains mirror-bright surfaces of solid even after storage for 2 years in a desiccator at room temperature. The addition of alloying elements influences the oxidation rate by ( 1 ) their incorporation in the PbO and the consequent change in the lattice vacancy concentrations or (2) by forming a more stable oxide film that covers the melt surface instead of PbO. At shorter times and very low concentrations, the additions in general may be expected to influence the oxidation kinetics through incorporation in the PbO. Figure 3 shows the increase in oxidation rate of Pb, prepared by double electrolysis, alloyed with very low concentrations of different alloying additives. At larger concentrations and at longer times, the formation of a more stable oxide film is likely. During the melting of the alloy, it is of importance to minimize the amount of dross (a mixture of oxide and some trapped liquid lead) formed and to prevent the loss of specific alloying elements from the melt. The effects of many of the alloying elements on dross formation have been studied to a limited extent. Although inadequate for understanding the

Time (S)

Figure 3 Effect of various additions in lead on the rate of growth of oxide layers at 500°C [2,278].(Courtesy of Springer Verlag, New York.)

314

Chapter 3

mechanisms by which the alloying additives influence the dross formation, these studies have been helpful in identifying the elements that help minimize dross formation under typical melting environments. Most of the alloying additions tend to increase the drossformation at temperatures of 400°C and 500°C as is shown in Figures 4 and S [ 102,2801. Figure 4 corresponds to drossing of the melt in still air. In this case, the lead used W ~ I S of Y9.993% purity and contained 0.006% Bi and 0.0004% Ag. Of the different common alloying additives commonly found in lead alloys, Cu and Cd additions resulted in high drossing. In the case of Cd, a maxitnum i n drossing is observed at 0.01%. Figure 5 corresponds to drossing in agitated lead melts. Lead used i n this work was of unspecified composition but showed little drossing in the melt i n the absence of any additions. Considerable inhibition of drossing can be obtained with small additions of aluminum and tin to pure lead and lead alloys such as lead-calcium (by 0.005%

Figure 4 Effect of additions (contents in %) on the drossing of lead at (a) 400°C and ( b ) 500°C during a 100-h exposure to still air 12,2801. (Courtesy o f Springer Verlag, New York.)

Processing of Lead Products

31 5

300 x? 3

U ._ -

m

zoo

1 F

E

2 700 U) U)

F

n

m am 0.1 0.10.01 0.1 O.OIOMO~I 0.1

0.1 0.7 a05 m 0.1 0.5 1.0 Pb Zn Bi Ag Cd Cd Zn Cu li Ca Sn Cu Zn Zn St Zn Cd

Figure 5 Effect of alloying on the cirossing of commercial lead a t 350°C in agitated lcad melts [ 1021. (Courtesy of Springer Verlag, New York.)

AI), lead with 6% Sb (by0.02-0.05% Sn), and lead with O.OS% Te (by 0.02% Sn) [2,2801. With the increase in agitation of the melt, the extent of oxidation tends to be higher. Among the lead alloys, Pb-Sb alloys need special consideration due to the importance of Sb as an alloying addition and its pronounced tendency for oxidation from the melt. In Pb-Sb alloys with antimony contents up to 1596, asharpmaximum in the rate of oxidation (or the amount of total oxides formed) is observed at 0.04% Sb on exposure to blowing air (Figure 6) [ 102,278,2831. With no bath movement and exposure to ambient air, this 250

zoo c

c m ._

g 150

L

0 a, v)

100 0

c -

50 1

0

0.1

l

I

I

3 5 S b , K Scale (wt.%)

I

l0

F

Figure 6 Variation of wcight increase due to oxidation with Sb content in Pb-Sb alloys on exposure to a blowing air environment 12781. (Courtesy of Springer Vcrlag, New York.)

31 6

Chapter 3

maximum occurs at around 0.01% Sb at 350°C. In stirred melts, the oxidation rate shows a pronounced maximum at around 0.01-0.05% Sb in the temperature range 350-500°C [ 102,278,2841. A much less pronounced maximum has also been sometimes observed around 0.2-0.3% Sb [285,286].At small levels of Sb in the Pb melt in the temperature range 35O-50O0C, Sb is present in PbO as Sb” near the oxide-melt interface and as Sb5’ near the oxide-air interface. This increases cation transport and an acceleration of the oxidation of lead until a maximum is reached at Sb contents of around 0.002-0.05%. Beyondthe maximum, the oxidation rate drops with increasing Sb content because of the appearance of lead antimonite. The second oxidation maxima at 0.2-0.396 Sb is attributed to the maximum removal of Sb from the melt. The antimony content of a melt decreases by selective oxidation and the rate of decrease is reduced with falling antimony content, with the rates approaching very low values at antimony contents below 0.1%. A maximum in the rate of oxidation of antimony at a given antimony content was only found if the lead contained, in addition to antimony, more electronegative metals such as arsenic, tin, or zinc. In oxidizing treatments, the accompanyingbasemetalsburn first, with onlyaslowdecrease of the antimony content. The oxidationof antimony only sets in more intensely after removal of the associated base metal 1287,2881. The addition of 0.17% or more of arsenic tends to inhibit dross formation in lead-antimony and lead-antimony-tin alloys [286]. The addition of Sn in small amounts reduces the tendency for rapid formation of oxide film, as indicated by the longer blue film formation time at levels of 0.001% (Figure 7) [286]. The blue film formation time is the elapsed time after skimming the melt surface before the appearance of a characteristic purplish skin on the melt surface. This is used in practice as a production control tool. The deoxidation of the melt by the addition of aluminum is usually recommended. Aluminum addition reduces the dissolved oxygen content and also minimizes dross formation through the formation of a protective aluminum oxide film.

B. Casting In the casting of lead alloys, the choice of the mold material depends on the melting point of the lead alloy, the chemical compatibility of the melt with the mold, size of the casting, dimensional tolerance, surface finish, and number of components to be produced. The low melting point of lead and lead alloys allows the use of many different mold materials, including steel, sand, iron, plaster, rubber, and wood. Obtaining a pore-free casting involves the ability to completely fill the mold cavity and to provide for the continued feeding of the liquid metal during solidification to compensate for the shrinkageassociatedwith the

317

Processing of Lead Products 600

500

Bi I

v)

v

-E

PP”. 3

cu

1

Sb

0.2

As TL

40.1

._ c

Cd

(1 41

0 .c

m

E

e

m

E G

2

iEs

200

100

0-1

1 0~00001

1 1

0~0001

10

100

Impurity percent (ppm) I

o*oa

I

0.01

1000

10,m

I

I

0.1

1

Percent

Figure 7 Variation of blue film formation time withimpurity (Courtesy of Dr. S. A. Hiscock.)

addition [286].

liquid to solid transformation. A measure of the ability of the liquid metal to flow through all the mold channels and fill the mold is given by a parameter referred to as “fluidity.” It is an empirical measurement and is defined by the length of liquid flow in a mold channel before it freezes up and stops further flow. In the spiral fluidity test, which is commonly used, the liquid

31 8

Chapter 3

metal is poured down the sprue and then allowed to flow horizontally in a spiral channel. Fluidity depends on the characteristics of the molten metal and casting parameters. The different parameters that influence fluidity include viscosity, surface tension, solidification characteristics, degree of superheat, rate of pouring of the melt, inclusions in the melt, mold design, mold materials, and heat-transfer characteristics of the mold and the moldmetal interface. Among these parameters, the solidification characteristics of the liquid metal is a critical factor in determining the fluidity [289,290]. The solidification characteristic of interest is the morphology of the solid-liquid interface during growth. Under the cooling rates that are typical in conventional castings, this interface morphology is planar in the case of pure metals and eutectic alloys, as they have unique solid-liquid transformation temperature. In the case of alloys that freeze over a large temperature range, the equilibrium partitioning of the solute at the interface between liquid and solid leads to constitutional supercooling of the liquid ahead of the moving interface. This constitutional supercooling results in the formation of dendritic or cellular interface. The extent of constitutional supercoolingand,hence, the tendency to form dendrites depends on both the heat extraction rate and the solidification (or freezing) range of the alloy. In the range of heat-extraction rates that are typical in conventional casting, the solidification range determines the interface morphology. If the solidification interface has cellular or dendritic morphology, the cells/dendrites that grow normal to channel walls or casting surface rapidly hinder the liquid flow, resulting inlow fluidity. The long-freezing-range alloys that have the greatest tendency for constitutional undercooling tend to form a large, mushy zone consisting of dendrites and a liquid metal and have low fluidity. A minimum of fluidity is situated in the neighborhood of the solubility limit in the solid state (i.e., where the solidification range is greatest, as can be seen in the Pb-Sn system) (Figure 8) [2891. On the other hand, pure metals and eutectics have good fluidity and are usuallypreferred in casting.Among the lead-antimony-tin alloys, the ternary eutectic alloy has the highest relative fluidity (Figure 9) [291,292]. Short-freezing-range alloys also have a nearly planar front and good fluidity. In addition to the ability to fill the mold, obtaining pore-free casting depends on providing a continuous supply of liquid metal to compensate for solidification shrinkage by the use ofan appropriate feeder. The feeder is designed using four criteria involving heat transfer, mass transfer, directional solidification, and minimum hydrostatic pressure. The surface areato volume ratio of the feeder is kept greater than that for the casting, to make sure that the casting solidifies prior to that of the feeder. The mass-transfer criteria makes sure that there is enough liquid metal available from the feeder to provide for solidification shrinkage. The feeder is placed such that solidifi-

Processing of Lead Products

319

Figure 8 Fluidity in Pb-Sn alloys 12891. (Reprinted with permission from McCraw Hill Companies, New York.)

cation initiates from a location farther away from the feeder and progresses toward the feeder (directional solidification). The feeder height is designed such that there is enough hydrostatic pressure to allow complete detail reproduction and prevent pore formation in the liquid. In addition to these general principles, the design process relies on past shop-floor experience. In the recent years, the use of finite element based thermal and fluid flow simulations are increasingly used in the design of casting processes. Solid-state thermal contraction of the casting from solidification temperature to room temperature makes the casting smaller than the mold cavity. Therefore, the linear dimensions of the mold cavities are designed to be larger than the casting dimensions by a certain amount called the pattern maker’s allowance. Thus, the patterns used to make the mold cavity are larger than the actual part by this amount. A linear shrinkage allowance of

320

Sb

Chapter 3

Pb

(at.%)

Pb

Sn (wt.%)

Sb

Figure 9 Fluidity of (a) lead-antimonymelts, and (b) lead-antimony-tinmelts 1291,2921. (Courtesy of Springer Verlag, New York.)

0.75-0.99% [293,294] has been used in lead castings. In addition to solid1.5% in leadalloys)occurs on stateshrinkage,avolumechange(about freezing during casting. As mentioned earlier, a liquid-metal supply to the mold cavity is maintained from the feeder to providefor this volume change. Table 20 in Chapter 2 provides data on the volume change on freezing and solid-state contraction for various lead alloys. Even with proper gating and feeder design, shrinkage microporosity is unavoidable in the case of long-range-freezing alloys. In these alloys, interdendritic feeding of liquid metal occurs through the channels between 10-

Processing Products of Lead

321

and 100-nm-wide dendritic arms [290]. The blockage of fluid flow and feeding will occur between 35% and 68% solid and results in microvoids with dendritic outlines. Cracks also may form due to thermal stresses that pull the dendrites apart. The other casting defects of major concern include distortion due to thermal stresses, laminations, blow holes, pitting on the casting surface, inclusions from mold, and native oxides from the melt. The solubility of gases such as hydrogen or oxygen in lead alloy melts isnot very significant in not usually present a problem. comparison to other metal melts and does Avoiding turbulent conditions during pouring could prevent entrapment of air. Deoxidation of the melt with AI also reduces the dissolved oxygen to extremely low levels. These, combined with the use of higher hydrostatic pressure, suppressbubblenucleation.Theuse of filters/traps in the mold removes inclusions and native oxides from the melt. 1.

.

.-

SandCastings

Sand molds are used when the surface finish is not critical. Such components include centrifugal pump impellers and flanged pipe fittings. In the case of sand molds, the mold is made from a moldable mixture of sand, clay, and water thatis packed and compacted around a pattern. The pattern has the shape of the part to be produced and may be made as a single piece or in multiple pieces. The mold is made in two or three parts to allow for the ease of pattern withdrawal and incorporates the gating and feeding system. Sand characteristics that are important are permeability, thermal conductivity, and strength. A typical sand mix consists of 5-7% clay, 2.5-3.5% water, 0.5% starch, and 3% coal dust. The typical green strength of these molds is around 140 kPa. The dry sand molding process is similar to the green sand process except for the heating of the mold to decrease water content near the cavity surface and a slight difference in mix composition. The surface hardness of the mold cavity surface is higher in dry sand molds. Usually, a gas flameisused todry the moldcavitysurface.Parts for acid-resistant evaporating vessels, valves, pumps, stirrers, and other components made of Pb-(2-10%) Sb alloys for the chemical industry are produced by sand casting [295,296]. Decorative art work and tigures are also produced by sand casting [297,298]. At a casting temperature of 340"C, the shrinkage is about to produce an 1.04% in these alloys. The sand casting has also been used 16 tons, with indievaporator for titanium sulfate that weighs as much as vidual parts weighing up to 4 tons [298]. In casting such heavy components, the mold must be strong enough to bear the pressure of the heavy metal and, in addition, must have the highest possible permeability to allow for the escape of gases.

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322

Sand castings are usually in the size range of 0.1-100 kg, although castings heavierthan 100 kg are alsomade. The economicalproduction 1 to 100,000. Thinnest section size is greater than quantity may vary from S mm and cast hole size is greater than 6 mm. The surface tinish could be in the range 6.35-25 pm 12991. When only a few parts are to be made, plaster molds are used. The plaster mold process reproduces fine detail i n the casting. The mold material i n this process is a mixture of plaster of paris (CaSO,) and water molded around the pattern. The mold is usually impermeable. However, up to 50% porosity can be obtained by foaming the plaster. Talc or silica Hour is used to improve the strength and the setting time. Mold is dried at 120-260°C before the metal is poured into the mold. For intricate castings, rubber molds are also used. Typical castings made by this process are in the size range 0.1-SO kg. The economical production quantity is S0 or more. The thinnest section size is greater than S mm and the cast hole size is greater than 1.5 mm. The surface tinish isin the range 0.8-3.2 pm. Dimensional accuracy of 0.25 mmis obtainable in parts up to 100 mm in size [299].

2.

Gravity Die Casting

Gravity die casting of lead alloys uses steel molds and the mold cavity is tilled by the gravitational How of the liquid metal poured in to the cavity. Large production runs of castings are required to justify the costs of fabricating steel molds. These metallic molds provide rapid heat extraction rates from the solidifying metal compared to sand castings. Excellent surface tinish and a large chill zone near the surface compared to sand casting could be obtained.Typical castings are in the size range0.1-70 kg 13001. The economical production quantity is 1000 or more. The thinnest section size is greater than S mm and the cast hole size is greater than 6 mm. The surface pm. Dimensionalaccuracy of 0.25 mm is finish is in the range1.6-3.2 obtainable in parts up to 100 mm in size. Gravity die casting isused to cast antimonial lead blocksandother components for radiation protection. Figure 10 shows a 9-in.-brick made by gravity diecasting [301]. Themoldconsists of steel sheet,about 4 mm thick, that is heatedtoatemperaturenear the liquidus curve.Themelt temperature is kept no higher than 20-30°C above the liquidus. By watercooling at the base, solidification proceeds from the bottom upward and the formation of pipes is prevented.Thecasting of lead-silver alloy anode plates for zinc electrolysis also involves gravity die casting. The casting of these large plates takes place by top-pouring [301]. A major useof gravity die casting of lead alloys has beenin the productionof grid plates for automobile ignition batteries 12961. The die

Processing of Lead Products

323

Figure 10 Antimonial lead brick for radiation shielding made by gravity die casting [301]. (Courtesy of Lead Development Association, London.)

coating for the insulation of the mold and assisting the separation is based on sodium silicate and fine cork powder. The metal is pumped from the melting chamber into the dies in a timed sequence of operations; a typical 15 grids/min. The casting temperature output for a modem machine is about is 500°C and the die temperatures is about 170°C. The solidification time is only a few seconds. Both lead-antimony alloys and lead-calcium or leadcalcium-tin alloy plates are gravity die cast. Considerable skill is required up so as to in achieving the right cooling conditions in the initial setting produce sound castings free from porosity, hot tears, or short runs. Local reduction of the thickness of the die coating is often used in heavy section areas in the grid impression to prevent hot spots from occurring, in order to produce a uniform cooling of the grid. Further applications of gravity die casting include the production of bearings and the lead coating of fittings of cast iron, malleable cast iron, cast steel, gunmetal, bronze, and special brass or steel. The lead coatingsin A lowand around these fitting is often carried out with antimonial lead. stress joint is made possible by heating the part to be coated to100- 180°C [302]. Cable sockets can be produced by dipping a steel core into molten lead when the lead solidifies as a coat on the core. A lead-tin alloy sheet

Chapter 3

324

of about eutectic composition and of thickness a few millimeters is cast on felt cloth. After milling, the sheets are bent into the shape of organ pipes and soldered. Commercial lead starting sheets for lead electrolysis are cast without a complete mold, the melt being allowed to run down an inclined plane.

3.

High-pressure Die Casting

In high-pressure die casting of lead, the molten metal is forced into a steel mold by plungers in the shot cylinder (pressure chamber). Pressure die cast1 l ) , in which the ing of leadalloysuseshotchambermachines(Figure molten metal crucible is located within the machine and the shot cylinder itself is in the melt [299]. A pressure die-casting machine with locking forces of up to 3000 MT are available, but for lead castings, much lower-capacity machines are used. In casting battery grids of low antimony-lead alloys and Pb-Ca alloys, the lead pot temperatures are kept above 45OoC, the feed line temperatures are kept at around 480-5 1O"C, and the laddle temperature is kept at or above 5 10°C [303].The high injection pressure leads to excellent casting-mold wall contact and higher heat-transfer coefficients ( h = 0.02 J/ cm'/s) 13041.In single-stage injection, the liquid metal enters the mold at high velocity. The cycle times are low and production rates are high. However. the turbulent conditions can result in entrapment of air, resulting in internal pores. The surface of the casting is chill cast on a smooth surface; thus. a part with excellent surface finish but with a lot of internal pores is

Port

Figure 11 A schematic of hot-chamberpressurediecasting [2991. (Courtesy of Dr. A. J. Clegg, Loughborough University of Technology, UK.)

Processing Products of Lead

325

produced. With multiphase injection, the initial slow injection of the liquid expels the air ahead of it and the subsequent application of high pressure can result in excellent detail reproduction with minimal internal pores. The pressure die casting of lead alloys is easy, as the melts hardly attack iron/ steel kettles and the molds, and show only slight shrinkage during solidification and cooling. Die materials for casting them can beof cast iron or steel.Forverylongruns,however, the chrome-molybdenum-vanadium alloy steel, H13, is used. The lead die-cast alloys typically contain Sn and Sb as principal alloying elements and may also have smaller amounts of Cu. An excellent example of the detail reproduction is the pressure die-cast printing type. Lead bullets, plugs, keyboard lead, conical stoppers, and lead packing glands are cast on steel molds by pressure die casting [2,54.297]. Lead plugs are made of commercial lead or antimonial lead [297]. Flat castings are produced in superheated molds by controlled directional solidification. Pressure die casting is alsoemployed for the production of battery plates, mainly for casting the positive plates of industrial batteries used for standby and electrical propulsion applications. The plates are usually larger than those usedin automobile ignition batteries and have splines that are circularwitha2-3 mm diameter in cross section. In these batteries, the activepaste is held in separatepolyestertubessurroundingeachspline. Typical output of positive spline plate castings from a hot-chamber machine would be 3 castings a minute for a 4-impression die, giving 12 platedmin. Pressure die castingprovideshighoutputandgooddimensional accuracy in the production of small bullet cores. A lead alloy with up to 2% antimony is used. The cores are fitted into jackets made of brass containing 90% copper and 10% zinc, or of cupronickel containing 80% copper and 20% nickel. Small pressure die-casting machines are also employed to make rea variety of small lead components,usually in lead-antimonyalloys quiringhighproduction rates and, frequently, great dimensional accuracy. Theyusuallyincludecounterweights for instrument parts suchasspeedometers, battery lugs andterminal parts, car and lorry wheelbalance weights, and bullet cores. The casting of memorials, souvenirs, ornaments, and fancy goods in antimonial lead is also widespread. Caskets and bowls from Japan are also die cast with amazingly good reproductions of all the details of the mold surface. These castings are generally given electroplated coating of copper or brass and then gold [305] or are chemically colored [306,307]. Typicalpressure die-cast components are in the size range0.05-25 kg. The economical production quantity is 5000 or more. The thinnest section size is greater than 0.5 mm and the cast hole size is greater than 6 mm. The surface finish is in the range 0.4-3.2 pm. Dimensional accuracy of 0.15 mm is obtainable in parts up to 100 mm in size [299].

326

4.

Chapter 3

Ingot Casting

In casting ingots in smelters, metal molds in the form of billets and slabs are used. The molds are frequently arranged on a turntable or a continuous is usuallyafine-grainedcastironand belt [2,308]. Moldmaterialused dressed with a graphite-based spray for the ease of ingot/mold separation. Melt is poured gently to avoid turbulence at a super heat of about 50°C. In the production of ingots for lead extrusion presses, the melt is poured directly into the container and allowed to solidify, and the ingot is then extruded in a hot condition. The cross section of the solidified contents of the ingot (Figure 12) shows columnar growth of crystals [309]. The long axis of the crystals is parallel to a cube edge of the unit cell (i.e., the direction of greatest crystal growth rate). This cast texture is common in cubic metals. A (111) texture has been produced by the solidification of a lead melt in

. I

Figure 12 Section throughthe solidified container charge of a cable press [309]. (Courtesy of Springer Verlag, New York.)

Processing Products of Lead

327

such a way that a single crystal forms from the middle of the surface of the liquid and by quenching a melt of zone-refined lead with less than 100 ppm Ag (by wt.%) [21. Long-rangesegregation is one of the problems associated with the casting of lead alloys and this is morepronounced in ingot casting. For example, in lead-antimony alloys, the regions which have solidified last in the interior of the ingot are richer in antimony [310]. Theoccurrence of weak inverse segregation is also observed sometimes (31l]. Grain size of cast lead alloys in general is coarse (Figure 12), but a greater grain refinement in the cast state can be obtained at higher concentrations of the alloying elements that leads to pronounced constitutional supercooling i n the liquid [141,1491. A low casting temperature also favors the formation of fine grains 13121. Semi-Durville casting with tilting book molds and DC continuous casting have been used successfully for casting large lead shapes. Other products cast in static metal moldsinclude lead and lead alloy anodes used in the electrolytic refining of several metals and for elecroplating. High-quality ingots of lead and other nonferrous alloys are produced on a new generation of Continuous Properzi ingot casting line 13131. With the demand for high-quality Pb and other nonferrous metal ingots, Properzi has developed a modern ingot caster that features a large casting wheel, 24.2 m in diameter (Figure 13) [313]. The surface of the wheel edge serves as a hrgc ring mold and the cast ingot is rolled to appropriate shape and cut to the desired size. The production rates of 15-30 tons for aluminum and much greater capacities for lead are possible on this caster. The ingot shapes are designed for easy packing and transportation.

5.

Casting of Lead Shots

The manufacture of lead shot uses a technique invented by Watts i n Bristol in England in 1782, in which the lead shot is produced by the breakdown of a fine liquid-metal stream to fine droplets. The soft shot consists of lead containing up to 0.5% As; hard shot contains up to about 2% Sb in addition. The influence of As in obtaining the spherical shape results from the oxidedissolving property of the arsenious acid formed on the surface [ 3143 151. Casting takes place from the top of a tower or the upper part of a mining shaft. The alloy is in a pasty form and put into a gas-heated iron pot, the the base of which is perforated with aseries of holescorrespondingto desired diameter of shot. On stirring the pasty metal, spheres of molten alloy flow through the sieve or coherent streams of melt are formed, which immediately break up into individual drops. The spheres, after solidifying duringfreefall,arequenched in water at thelowerend of the shaft. After

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Chapter 3

Figure 13 A modem Properzi ingot caster with a 4.2 m wheel diameter [313]. (Courtesy of Properzi International, Milano, Italy.)

drying the shot, the twins(i.e., grains joined together) are removedby using the ability of the spherical balls to roll down an inclined plane. The shots are sorted for diameter in cylindrical sieves and finally polished with graphand economical. Production ratesof smallite in a drum. The method is fast diameter shot (so-called fine bird shot) in a plant could be several tons/day.

6. ContinuousCasting Continuous casting is now widely used in the production of slabs, plates, or strips of a number of commercial alloys. The process for forming slabs or plates involves feeding the molten metal froma tundish (1) into a vibrating (2) onto awater-cooledsingle or bottomless water-cooled metallic mold, twin moving belt (belt casting or twin belt casting) or (3) between twin rolls rotating in opposite directions (twin-roll casting). In the caseof the bottomless mold, the material exits the mold with only the skin region solidified. Further solidification occurs by water or gas spray. In the case of drum or belt casters, the solidification is complete as the metal leaves the drum or the end of the belt. After the solidification iscomplete, the solidmay further be roll-formed to the desired size and shape. These processes are energy efficient, have high material utilization, and are clean. Uniform composition and better surface finish are also obtained. The methods of production of

Processing Products of Lead

329

thin sheets, strips, or foils include belt casting, twin belt casting, twin roll casting, melt extraction technique, and melt drag technique. The melt extraction technique involves casting onto a rotating drum partially immersed in the melt. This process is also referred to as “dip casting.” In the caseof lead alloys, continuous casting hasbeen principally used for the productionof lead grids or strips for battery applicationsand for the production of rods and balls. Melt extraction and melt drag techniques are commonly used in the production of grids and strips. The layerof lead which adheres to the rotating roll is peeled off by a knife to form a continuous strip. Win-roll casting has also been used to produce lead strip. The strips are subsequently slit and expanded to form thegrid. One of the most widely used continuous-casting processes for the production of lead wire and rod is the Continuous Properzi Process.

Continuous Properzi Process.

The first patent in continuous casting of a rolled rod was issued to Ilario Properzi in 1948 titled “Automatic and continuous process to obtain rolled rod directly from molten metal and relevant machinery” [313]. There are morethan 350 Properzi continuous-casting rod and strip lines for the production of Pb, Al, Cu,and Zn alloy products operating in different parts of the world. Figure 14 shows the Properzi Continuous Casting and Direct Rolling (CCR) machinery exhibited at the 1948

Figure 14 The Properzi Continuous Casting and direct Rolling (CCR) machinery exhibited at the 1948 International Trade Exhibition in Milan, Italy[313]. (Courtesy of Properzi International, Milano, Italy.)

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Chapter 3

International Trade Exhibition in Milan, Italy and now in permanent collection at the “Leonardo da Vinci” National Science and Technique Museum in Milan. A electrolytic copper rod was continuously cast and rolled for the first time in the world on a Properzi machine. Figure 15 shows the Properzi CCR lines for the production of rod, strip, and balls. Complete Properzi CCR lines for production of nonferrous metals are applied to lead and zinc rods for theammunitionindustry and galvanizing purposes. ContinuousProperzi has long been oneof the prominent suppliers of lead strip lines for the battery industry. For special applications, lead and lead alloy rods are cast and rolled by Properzi lines. Lead wire produced from a Properzi CCR lead rod has been used to produce calibrated lead shot by a special Properzi machine. In fact, this process was Properzi’s first invention. Almost all precision lead shots in the world are produced by this technology, including those used by Olympic and other world-class athletes. This line can produce a strip which

Figure 15 Properzi CCR rodandstrip national, Milano, Italy.)

lines [313]. (Courtesy of ProperziInter-

331

Processing Products of Lead

finds application for beveragecanopenings,lead-sheathedcables,soundproofing shields, capsules, crown tops, and roofing. One successful application is the production of an alloyed lead strip, which has been proven to be one of the best materials for high-quality grids for starter batteries because of the excellent mechanical properties of ex1 propanded grids of both lead-calcium and lead-antimony alloys. Table of different lead posesproduct lines forcontinuouscastingandforming forms [313]. This rolling system has been specially designed to safeguard the environmentandreduce the pollution level far below the existing standards. Other Conrin~ousCasting Processes. Another process that has been used for the production of lead sheet and strip by continuous casting is the DM (direct method) process developed by Broken Hills Associated Smelters Pty., Ltd. of Australia and now manufactured by Lead Equipment and Development Pty., Ltd. of Australia [3 161. Figure 16 shows a DM continuous

Table 1

Properzi Product Line for the Continuous Casting and Forming Different Lead Forms [313]. (Courtesy of Properzi International Inc., Milano, Italy.)

Lead and Zinc Wire Melting equipment Type furnaces combined Tiltable from Starting Capacity 1 MT/h Casting and rolling equipment Type Lines CCR Properzi from Starting Capacity 1 MT/h m-diameter Standard: Product Coiling equipment Type Basket coiler

of

rod

Lead Strip Melting equipment Type Capacity Casting and rolling equipment Type Capacity Product Coiling equipment Type

Furnace set with liquid-metal Starting from 3 MT/h

pumping unit

Properzi CCR Lines Starting from 3 Mt/h Strip thickness 0.6 mm min width up to 1 l 6 mm Double automatic coiler

332

Chapter 3

Figure 16 DM continuous-sheet caster [316]. (Courtesy of Lead Development Association, London.)

caster for the production of lead sheets and strips [316]. DM process uses 1 through Code 6 sheets of widths a drum-casting technique to produce Code up to 1.5 m. Casting rates are about 12 tonsb. The process produces a sheet with excellent surface finish and thickness control. The DM process is primarily used in the manufacture of lead sheets for building construction for waterproofing, roofing, flashing, and facings. A similar approach but with engraved roll surfaces could be used to produce grid plates for batteries. A continuous grid casting line of CEAc, France for the production of battery grid plates using such an approach is shown in Figure 17a [317]. A battery grid produced by such a machine is shown in Figure 17b [317].

7. Processing of Battery Grids by Cominco’s Continuous Casting and Rotary Expansion Process One of the established lead alloy continuous casters is the Cominco’s patented Multi-Alloy Continuous Strip Caster for producing low-cost and highquality lead strips for use in the manufacture of SLI (starting, lighting, and ignition)batteries. Cominco uses continuous casting of strips and rotary expansion technology to produce new and improved positive and negative battery grid plates at a low cost [318-3231. The production of expanded metal grid plates is typically a two-step process. The strip is first cast and then coiled for storage. Later, the coiled an expander line where it is continuously converted into strip is fed into

Processing Products of Lead

333

(b)

Figure 17 (a) Continuous battery grid caster and (b) continuous-cast battery grid [317]. (Courtesy of Lead Development Association, London.)

Chapter 3

334

mesh, then pasted and divided into discrete plates ready for flash curing and storage. The two-step approach is necessitated by different production rates for the casting and rotary expansion process (24 m/min versus 60 m/min) a s well the need for age hardening of the alloyed strip for improved strength and handleability through the production process [320]. Figure 18 presents a schematic diagram of the caster. The caster consists of a chilled drum and tundish [319]. The tundish is a vessel that acts as a liquid reservoir and delivers a layer of liquid alloy to the casting surface of a rotating drum. The rotating drumdragsacontrolledamount of the molten alloy from the tundish at a substantially vertical section of the casting surface, onto its cooled surface, where the molten metal rapidly solidities and forms a solid strip with predetermined dimensions. The lip insert contoured to the shape of the drum controls the surface level of the pool of the molten metal. The diameter of the drum, rotational speed, surface finish of the roll, and the roll surface temperatures determine the casting speed and strip thickness. The internal structure of the tundish is designed to provide a clean metal supply with minimal turbulence to the drum surface. The strip is pulledfrom the rotating drum by two pull rolls. The strip is slit using adjustable rotary knives to obtain the desired strip width. The strip may be heat treated prior to coiling.Figure 19 presents the Cominco’s multistrip caster [321]. A caster with four coilers is shown in Figure 20 13221. The lead strip coilsare then moved to the rotary expander plate-making line. The plate-making line consists of a turntable strip uncoiler, rotary expander, rotary tab blanker, and rotary plate divider. The strip uncoiler has a 3.4-MT capacity. The rotary expander continuously cuts and elongates the 21) [322]. It is thenuniformly lead alloy strip to preformmesh(Figure

.^ Figure 18 A schematic of Cominco’sstrip-castingprocess Cominco, Missisauga, ON, Canada.)

13191. (Courtesy of

Processing of Lead Products

335

Figure 19 Cominco’s multiship caster [321]. (Courtesy of Cominco, Missisauga, ON, Canada.)

stretched by the expansion chain system into expanded mesh. Before the expanded mesh is pasted, its center solid border is blanked by a rotary tab blanker. The remaining center portion becomes plates lug. The rotary plate 22 divider cuts the blanked and pasted mesh into individual plates. Figure illustrates the production of battery plates from the lead strip [322]. Cominco’s Multi-Alloy Continuous Strip Caster is capable of casting both short- and long-freezing-range alloys such as Pb, Pb-Ca, Pb-Ca-Sn, [321,322]. The Pb-Sb, Pb-Ca-Ag, and Pb-Ca-Ag-Sn for positive plates strip’s inherent characteristicsof zero porosity and corrosion-resistant structure provide increased battery life and performance. In this process, up to five coils can be cast simultaneously. A strip is cast directly to gauge, without rolling, and the thickness is continuously measured for operator control. The of about 2.9 MT/h of finished coiled strip. caster has typical production rates 0.25 to 2.30 mm.Stripthickness Thebroadstripthicknessrangesfrom

336

Chapter 3

4

Figure 20 Cominco’s multistrip caster [322]. (Courtesy of Cominco, Missisauga, ON, Canada.)

tolerances of 6% for a nominal 0.75-mm-thick strip can be obtained. Strip widths of up to 53 cm can be produced. Low maintenance and fewer operators are needed. High material utilization, low lead-to-air emissions typically less than 25 pg/m’, low noise levels, and low heat emissions make this process very attractive. Production rates with advanced expanded metal technology using currently available pasters are typically 450-600 plates/min from a line occupayoff pying about 18 m of linear floor space (i.e., the distance from the strip machine through to the divider, which cuts plates ready for flash curing). Currently, the speeds of these lines are limited by the paster. With highspeed pasters, production rates can approach 800 plates/min [318]. The factors that are of importance in the positive plate production are (1) castability of the alloy strip, (2) expandability of the strip alloy into mesh, (3) maintenance-free or gassing requirements, (4) resistance to corrosion and growth during storage and service, and (5) deep discharge recovery. Until recently, the majority of positive plates were made from a lowantimony alloy using conventional gravity-cast machines. Strip-cast and expanded positive plates were also used to some extent and were made from are the lead-calcium-tin alloys (Pb-0.09 Ca-3 Sn). These positive plates combined with binary lead-calcium negatives to make the popular hybrid battery. Such hybrid batteries with the combinationof lead-calcium negatives and lead-antimony positives provided an optimum balance between mainte-

Processing of Lead Products

337

Figure 21 Cominco’s rotary expander [322]. (Courtesy of Cominco, Missisauga, ON, Canada.)

nance-free and overall performance requirements.In this battery, the less sensitive negative plate is routinely produced by expanded metal processes. However, the alloys used for automotive positive plates have changed substantially since 1990, especially in North America [320]. The main reasons are the improved maintenance-free characteristics required in the battery to satisfy demands by consumers for convenience and the increasing underhood temperatures in the newer more aerodynamically designed vehicles.Elevatedtemperatures promotecorrosion,gridgrowth,and,ultimately,batteryfailure.Anotherfactor, although notasinfluential,isimproved recharge capability. Five years ago, a low-antimony (1.5%) alloy was still a prominent alloy throughout the North American battery industry. Today, low Sb is in steep decline in favor of the calcium alloys. The prominent

338

2 0

ru 0

..

v

Chapter 3

Processing Products of Lead

339

new positive plate alloy is Pb-Ca-Ag-Sn that has good creep resistance and corrosion resistance, low degassing, and improved recharge capability. This alloy was developed and patented by GNB in the early 1990s to specifically combat high-temperature corrosion. Pb-Ca-Ag-Sn alloy is now used by several battery companies for commercial plate production. GNB currently has approximately eight Cominco rotary expander lines in commercial Pb-Ca-Ag-Sn plate production. The as-cast grain structures, such as those produced by the Multialloy strip caster, exhibit (1) higher resistance to recrystallization caused by elevated temperatures and (2) higher creep resistance [318,322]. Continuous processesareinherentlylower in productioncostthanthe conventional book-mold or gravity-cast technologies. The lighter weight of the strip cast To and rotary expanded grids allows one to pack more grid platesbattery. maximize cold crank performance, the rotary expanded grid is designed to have a low-electrical-resistance design. Small diamonds minimize the effect of the less conductive paste. In addition, differential width diamond wires assistcoldcrankperformance by increasingconductivecapacity in the higher-current-density areas of the grid. Qpically, the width decreases from 1.8 mm at the top of the grid, to 1.1 mm in the middle, to 0.9 mm at the bottom (Figure 23) 13121. The small diamond grid assists paste retentionby simply increasing the grid wire-paste interface. Paste retention is further assisted by an irregular, nonflat-surface helical twist in the rotary expanded grid. Higher paste retention improves battery life. The negative grid is not as sensitive to design as the positive, although this grid has also Seen a

Figure 23 Differential width diamond-grid-wire structure [318]. (Courtesy of Corninco, Missisauga, ON, Canada.)

340

Chapter 3

dramaticreduction in diamond size over the years. Thenegative grid is typically 25-30% lighter than the positive, and, therefore, from a processing standpoint, it is more susceptible to physical distortion and damage. For a given grid weight, a smaller diamond provides a more rigid expended mesh which helps to minimize possible distortion during processing and handling. C. Important Cast Forms

of Lead

Fiveimportant cast forms of basic lead are valves, pipe fittings, pumps, anodes, and vessels.

1 . Valves and Pipe Fittings Different types of cast lead valve and pipe fitting are available for use with other lead-based equipment. They can also be obtained in lead-lined steel or lead-lined iron form.These lined valvesor fittings are referred to as supported-lead- or bonded lead-type equipment. Cast hard lead (or lead-lined) valves are available in the Y, angle, splitbody, wedge or gate, check, and diaphragm patterns (Figure 24) [61]. The Y and angle pattern valves are available with a one-piece plug and stem or with a removable plug of acid-resisting rubber. The split-body valve can be made into a y or angle pattern valve by repositioning. The split-body valve is normally furnished with lead or rubber plugs and lead seats. These can be easily replaced when they are worn or when special conditions require the use of an alloy plug and seat. The gate- or wedge-type valves have a hard lead seat cast as part of the body. They can be furnished with disks of rubber, plastic or special alloysas required. Thecheckvalvehasasplitbody pattern which permits easy repair and replacement of the seat and disk with other materials. The clapper is hinged and will swing completely out of the flow path or seat itself tightly when flow ceases. The diaphragm valve has no stuffing box. Flow is controlled by a flexible and inert gum rubber diaphragm. All hard lead (andlead-lined)valvescan be furnishedwith drilled flanges. A 1/32-in. raised lead face is provided on all flange faces to ensure maximum, lead-to-lead contact at joints. Fittings available in hard lead and lead-lined forminclude tees, crosses, Ys, laterals, 45" and 90" elbows, return bends, and reducers. Some of these are shown in Figure 25 [61]. The fittings have bolt holes and dimensions in conformance with the ANSI standard for Class 125 cast-iron fittings. 2.

Pumps

Cast hard lead (and hard lead-lined) pumps of varying sizes and types are available. If the pump base is made of cast iron, it is usually protected from corrosion by leaking fluids by means of a lead cover.

Processing of Lead Products

Y

341

Angle

Diaphragm

Figure 24 Different lead valve patterns [61]. (Courtesy of Lead Industries Association, New York.)

Figure 25 The different forms of hard lead and lead-lined fittings [61].(Courtesy of Lead Industries Association, New York.)

Chapter 3

342

3. Anodes Anodes made of lead or lead alloys are used in the electrolytic refining and plating of metals,suchascopper,zinc,andchromium,and in aluminum anodizing. Lead is preferred over other metals in such applications because of its excellent resistance to corrosion in many electrolytes, especially those based on sulfuric acid or chromic acid. Lead anodes also have a high resistance tocorrosion by seawater,makingthemeconomical to usein the cathodic protection of marine structures, where an impressed current system is used to protect the steel hull. Anodes may be cast, rolled from sheet, or extruded. Extruded anodes are often circular in cross section with a diameter of 1.5-2 in. The surface may be corrugated or ribbed to increase the surface area and, therefore, the current-carrying capacity. The more popular compositions are chemical lead, 7/93 tin-lead alloy, lead-calcium-tin, and 6% antimonial lead. Silver up to a few percent may be added where it increases corrosion resistance leading to longer anode life or where it improves the dielectric properties and anode efficiency. Aluminum- or copper-core lead anodes have been developed for use in metal-finishing operations. It has been claimed that the higher electrical conductivity of the core reduces the voltage requirements compared to solid lead anodes, bringing about reduced operating costs.

4.

Vessels

Lead vessels are sometimes made by casting 8- 12% antimonial lead to the desired shape (Figure 26) [61]. However, as lead is mechanically weak compared to steel, only a few vessels for special purposes have been made.

II. METAL FORMING Metal-forming processes involve shaping of the metal by solid-state deformation. The input material forprimarymetal-formingprocessessuchas rolling, extrusion, or forging is usually a billet or slab produced by casting. Deformation usually involves high levels of stresses and, therefore, requires resilient and strong tooling. The high costs associated with the machinery andtoolingareexpensive;thus, the use of formingprocesses for many metals is usually economical only if the production volumes are large. However, the softness of lead alloys requires relatively less resilience and, thus, less expensive tooling. This, combined with the low-energy input required for deformation, makes the production of lead shapes by different forming processesveryeconomicaland attractive. Extrusionand rolling are two

Processing of Lead Products

343

Figure 26 Seventeen-ton evaporator vessel made of cast lead 8% antimony alloy for concentrating titanium sulphate solution [61]. (Courtesy of Lead Industries As-

sociation, New York.)

widely used processes for lead alloy shapes. The use of forming processes using industrial machinery began in the late 18th century with the award of the first patent for a lead press granted in 1797 to Bramah in London [2]. A brief background on different forming processes and the commonly produced lead alloy shapes are discussed in this section.

A.

Extrusion

The extrusion process is used for the production of lead rods, wire, pipes, heating and cooling coils, cable sheathing, welding rods (burning rods), and bar anodes. In the extrusion process, the metal is reduced in cross section by forcing the metal through a die. The process is ideally suited for the production of shapes that have constant cross section through their length, such as tubes and rods. The lead pipes were the first of the lead products to

344

Chapter 3

be extruded in which casting was replaced as a primary method of making lead pipes. The extrusion operation could be of the following types: direct, indirect, and lateral. Figure 27 presents the geometry of extrusion in the different types of extrusion [179]. In indirect extrusion presses, the billet of metal is at rest relative to the wall of the container, whereas in forward and lateral presses, it is moved relative to the container. In both forward and lateral extrusion, the frictional forces between billet and container must be overcome. As the billet is extruded, these forces decrease due to the reduction in contact area between the billet and container. Idealized force versus displacement curves during both direct and indirect extrusions are shown in Figure 28 [324]. In the case of direct extrusion, the force increases sharply due to the compression of the billet to till the container. Some extrusion of relatively undeformed material also occurs. As the steady-state extrusion of the material through the die opening begins, the load drops steadily. This drop is due to decreasing frictional effect at the billet-container interface. With the progress of extrusion, the contactareabetween the billet andcontainerdecreases, lowering the frictional effect. Toward the end of extrusion, a cavity or pipe formation occurs along the centerline with an associated decrease in load initially, followed by a rapid increase in load. In the case of indirect extrusion, after the onset of steady-state extrusion, the load remains constant until the onset of cavity formation. The load after this point decreases initially, followed by a rapid increase in load. The operation must be stopped before the load starts to increase in order to prevent damage to the equipment. The situation for lateral extrusion is similar to that for direct extrusion 1 1 79,3241. The earliest comparison of direct and indirect extrusions was made by Pearson and Smythe [325] using lead, cadmium, bismuth, and tin and a 31mm-diameter container. Extrusion rates were higher for a given extrusion in the indirect extrusion process. In direct pressure and remained constant extrusion, the extrusion rates rose progressively and approached the value observed for indirect extrusion. The use of a lubricant had minimal effect in the case of lead, but a more pronounced difference was observed in the case of bismuth. A notable effect of lubrication was however observed in the case of extrusion of lead pipe 13261. In general, the extrusion pressure depends on several material and process parameters. The material parameters include yield strength, work-hardening behavior, and strain-rate sensitivity. The process parameters include the extrusion ratio, geometry/shape of the cross section, extrusion die angle, temperature, properties of lubricant used, and rate of extrusion. The extrusion ratio R is detined by the equation R = A,,/A,, where A,, is initial crosssectional area and A, is the tinal cross-sectional area. The geometry of the

345

Processing of Lead Products

Direct extrusion

Closure

Indirect extrusion

Figure 27 The geometry of extrusion in the different types of extrusion [I791 (Courtesy of McGraw Hill Companies, New York.)

346

Chapter 3

Fraction of billet extruded

Figure 28 extrusion.

-

ldealized force versus displacement curves during direct and indirect

cross section is defined by the circumscribing - circle diameter (CCD) or by the shape factor S , which is the ratio of the perimeter divided by crosssectional area 13241. The nature of the lubricant and the surface finish of the container and die walls detennine the frictional effect. The extrusion die angle is ii key parameter in defining the extent of redundant deformation region. Estimations of extrusion pressure can be made using different approaches such as ideal work, lower-bound analysis, upper-bound analysis, and finite element analysis. An ideal work or unifonn energy approach equates external work to energy consumed in ideally deforming the workpiece [327]. Friction and redundant or nonhomogeneous deformation are neglected. The minimum extrusion pressure is then given by

If work hardening is assumed to be zero, (T is the yield strength. Using this approach, Siebel derived an equation 132x1 for the extrusion pressure 11 necessary for extruding a round billet of diameter D to a round rod of diameter cl (neglecting external forces of friction, and in the absence of hardening) as

p = Y In

($)

Processing Products of Lead

347

Siebel used the yield stress Y value of 2.8 kg/mm', determined from compression tests [329] in this equation. An experimental measurement of extrusion pressure at different reduction ratios was also experimentally determined [330]using a 35.7-mm-diameter container and a billet extrusion rate of 6 mm/min. Figures 29 and 30 present the extrusion pressure versus displacement curves for various extrusion ratios. The risein the right-hand part of the upper curve in Figure 29 is due to lead being squeezed out between the die and the wall of the container. The cleanly ground wall of the container minimized the effect of friction in direct extrusion(Figure 30). A semilogarithmic plotof D'/d' versus pressure gave a straight line as predicted, but the slope was slightly greater, as expected because of the effects of friction and redundant deformation. In general,theextrusionpressurecanbe defined by the following equation which has the same form as that of Siebel: P=KInR

(3)

where K is the extrusion constant and R is the reduction ratio. K is experimentallydetermined and includes the effects of process parametersother than R as well as lnaterial parameters. Figures 31 13261 and 32 [325,33 I 3321 compare the variation of extrusion pressures with temperature for lead

I

4

0

I W

I I

m I

a

I

l

I

I m

a0

Posltion of matrlx (mm) I

W

I

M

1 I

0

Distance from base (mm)

Figure 29 Extrusionpressureversusdisplacementcurves during direct extrusion of lead for various extrusion ratios 13301. (Courtesy of Springer Verlag, New York.)

348

Chapter 3

I

I

40

30

I

I

20 l0 Distance from base (mm)

0

Figure 30 Extrusionpressureversusdisplacementcurvesduringdirectextrusion of lead for various extrusion ratios [330].(Courtesy of Springer Verlag, New York.)

l#

200 m 4w Temperature ("C)

m

V

Figure 31 The extrusionpressurefordifferentmaterials ature 13261. (Courtesy of Springer Verlag, New York.)

as a function of temper-

349

Processing of Lead Products

0

Pb-O.B%Sb (Alloy

B)

+ Pb-o-Wo Sb-O.25%Cd (Alloy D) Pb - I

iin-0.25°/oCd (Ternar Alloy No.2)

* P b - 0 . 4 % Sn-0*15%Cd(AIloy 8) 0 .

0.1

I60

200

240

Extrusion temoeratwe

260

('C.)

320

Figure 32 The extrusion pressure for different lead alloys perature [325.331,332]. (Courtesy of Dr. S. A. Hiscock.)

as a function of tern-

and lead alloys. Figures 33 [333] and 34 [325,326,332] show the variation of extrusion pressure with extrusion speed at various temperatures for pure lead and lead alloys. During the extrusion process, the temperature of the material increases due to the work done against friction and the deformation of the material. The thermal profiles that exist are complex and dependent on a heat transfer within the billet, heat transfer across the billet-tooling interface, heat generation due to plastic deformation, and heat generation due to internal shear and friction between the deforming material and tooling. The extrusion rate and extrusion ratio are two key parametersthat determine the extent to which

Chapter 3

350

20 -

10 987-

z6ff a

=

7

54*+

v

P

z

v)

3-

P

a

2-

I-"?! 0.8

~

0.6 -

-

I

I

8.0 Speed of ram (rnlrnin)

I

5OO.G

Figure 33 Thevariation of extrusionpressure with extrusionspeed temperatures [333]. (Courtesy of Springer Verlag, New York.)

at various

the material is heated. The change in the temperature of lead as it exits the die is shown in Figure 35 [334] for different values of R . The original billet diameter and its length were 50.8 mm and 88.9 mm, respectively. The rise of temperature corresponds to an extrusion length of 63.5 mm. The average extrusion pressure for pure lead as a function of reduction ratio is shown in Figure 36 for two different extrusion rates. The increase in extrusion pressure with changes in the shape factor of the cross section lead [324].The variation of extrusion is illustrated in Figure37forpure

Processing of Lead Products

351

Figure 34 The variation of extrusion pressure with extrusion speed at various temperatures for different lead alloys 1325,326,331,3321. (Courtesy of Dr. S. A. Hiscock.)

pressure of pure lead with extrusion ratio and extrusion pressureis presented i n Table 2 (3351. In pipe extrusion, the forces depend essentially on the same conditions as in the extrusion of solid rods. In the extrusion of lead, as distinct from other nonferrous metals, only a slight tensile force is exerted on the mandrel.

352

Chapter 3

Figure 35 Thechange in the temperature of lead a s it exits the die at different extrusion ratios 12.3341. (Courtesy of Springer Verlag, New York.)

1500 a

1200

"

h

m

a

z

900"

a

600 --

0 300 --

b a

0 0

I

I

1

2

1

3

4

5

353

Processing of Lead Products

Figure 37 Increase in extrusion pressure for pure lead with changes in the shape factor of the cross section [324].

The uniform wall thickness of the pipe depends to a great degree on the shape of the mandrel and its coaxial position in the container. The loss of material due to variable sizes of the extrusion residue can be reduced by effecting the piercing of the solid lead billet and extrusion to pipe in two separate operations 121. The flow process in extrusion can be made visible in different ways of different colors as -for instance, by using wax billets having layers model materials. The extrusion of wax billets, cut longitudinally into two

Table 2 Variation of Extrusion Pressure of Pure Lead with Extrusion Ratio and Extrusion Pressure [335]. (Courtesy of Dr. S. A. Hiscock.)

Rate of extrusion (dmin)

50 2.39 1.63 50 2.5 1.92 2.77

9.14 5.07 4.06 3.32 2.77 18.29 2.74 5.78 4.65 3.88 3.27 27.43 3.69 6.46 4.71 2.1 4.46 3.60

T ("C)

(MPa) Pressure R = 50

Pllog R R = 200

R = 50

R = 200

200 250 200 250 150

200 250

1

4.06 6.91

8.48 1

1.94

354

Chapter 3

halves and put back together after inscribing a rectangular grid lines on the cut surface, allows a study of the flow patterns during extrusion [2,329,336,337]. Welding together of the two parts is prevented by a lubricant such as graphite,or white lead in oil.Thedistortion of the network consists, in the simplest case, of an extension in the axial direction and a contraction perpendicular to it. This applies particularly to that part of the billet in the neighborhood of the axis. In the outlying regions, on the other hand, the sides which were originally parallel become curved and displaced toward one another. Three kinds of flow in the extrusion process could be identified experimentally (Figure 38) [337]. Type a is characterized by the fact that friction between the outside of the billet and the container is excluded or at least extensively reduced by using inverted extrusion or, in the case of direct extrusion, by a lubricant. Type b consists of those extrusion processes in which friction works itself out fully on the skin of the billet. In that case, the skin remains, in part, adherent to the container and is sheared off the bulk of the billet. The meshes of the network on theperiphery of the emerging extrusion are, therefore, much more distorted than in Type a. Types a and b occur principally in low-melting metals such as lead. Type c is, on the contrary, found in extrusion processes which take place at high temperatures-for instance, in the extrusion of copper. Here, the outside of the billet cools considerably; first, therefore, the warmer internal zones flow within a thick peripheral layer. Only afterward does the latter take part in the flow process. In these experiments, designed to render the deformation

Figure 38 Flow patterns during (a-c) the direct extrusion and during extrusion [ 1791. (Courtesy of McGraw Hill Companies. New York.)

(d)

indirect

Processing Products of Lead

355

processvisible, the velocities of extrusion are lowerthanthoseusual in practice. The theoretical treatment of extrusion has achieved great advances in recent years. Slip-line-filed, lower-bound and -upper bound approaches have been extensively used for studying extrusion in-plane strain condition. The availability of fast andinexpensivecomputershasallowed the use ofan finite element analysis approach to simulate extrusion of three-dimensional (3D) complex shapes. Realistic predictions of flow patterns and deformation loads for various 3D extrusion geometries, process parameters, and material parameters can now be made.

1.

Extrusion Presses

Hydraulic presses are commonly used in extrusion processes, as they can deliver constant force over a long stroke. Both horizontal and vertical presses can be used in extrusion. Horizontal presses typically have capacities ashigh as 5000 metric tons. Much higher capacities are also possible. However, for lead alloy extrusion, the capacities of the presses used are only a few metric tons. Horizontal presses have been used for the extrusion of lead alloy rods and wire. Horizontal presses are not preferred inlead alloy extrusion used for tubes because of the problems of bending and nonuniform wall thickness. Vertical presses have lower capacities than horizontal presses, typically less than 3000 tons. Vertical presses need more head and pit room, but the alignment of the ram is much easier.

2.

Defects in ExtrudedProducts

Various defects that are common in extruded lead products and their causes are as follows 11791: Defects

Cause

Fir-tree cracking Surface heating, intergranular cracking Bamboo defect Periodic sticking of billet to the die Pipe defect Surface oxides and impurities drawn into billet due to improper flow pattern

3.

the center of

the

Extrusion of Rods, Pipes,andWires

Rod and wire for solders are usuallymade by direct extrusion.Extruded lead products have wide-ranging applications. Extruded lead wires are used i n ammunition, battery manufacturing, lead welding,bearinggauging, weights,gaskets, and tumbled lead shot.Extruded lead strips are used in

356

Chapter 3

stamping and coining stock, vibration dampening, corrosion-resistant tags, radiation shielding, weights, and gaskets. An adhesive-backed extruded lead strip is also made and is a convenient form in many of the above applications. Extruded rodand bar are usedin machining stock, vibration dampening, radiation shielding, weights, and anodes. Extruded piping and tubing are used in explosive delays, linear-shaped charges, liquid-chemical transfer, acid-mist precipitator components, and anodes. Extruded custom shapes are used in lead came, caulking, anodes, radiation shielding, and equipment components.Thefillermaterialrequiredformany lead joints is supplied from extruded welding rods (burning bars). For small-diameter wires in the I-5-mm-diameter range, multihole dies are often used. Precast billets are used to extrude rod and wire. Lead pipe is used in conjunction with lead-based vessels, valves, and fittings to provide a completely corrosion-resistant equipment system. Lead pipes are also used to convey corrosive liquids and handle the corrosive acid mists found in many electrostatic precipitators. The lead pipes generally used in applications requiring high corrosion resistance are made of chemical lead and alloys of antimony (6-8%) and tellurium (0.04-0.05%). The sizes of pipe available normally range from tubing with an inside diameter of 1.6 mm ( ] / l 6 in.) up to pipe with an inner diameter of 305 mm (12 in.). Larger inner diameters are also available. Lead pipe is usually specified by the inside diameter and either by weight per foot or wall thickness. Table 3 shows typical sizes and weights of chemical lead pipes [61]. The small-diameter pipes are shipped on coils or reels, whereas the straight lengths of larger-sized pipe are carefully shipped as fabricated, or crated, if necessary. Corrosive fluids areoftenheatedandcooledusinground,oval,or corrugated lead coils. Heating and cooling coils are made by bending pipe or by extruding pipe in a desired curvature. Corrugated pipe is extruded in helical form. Tubes or pipes are made by extrusion using vertical presses (Figure 39) [3311 using lead containers with a capacity to handle 0.25 to 1.7 metric tons. The presses range in capacity from 5 to 15 MN. Both direct and indirect extrusions have been used for pipe manufacture, but the indirect method is preferred. The ingots are obtained by filling the liquid metal in the container and allowing it to solidify in the container prior to extrusion. An opening through the top of the press allows the pipe to pass through onto a coiler. High-viscosity oils or tallow is used to lubricate the mandrel. Extrusioncanbe used toproduce ( 1 ) wirediameters 0.008 in. (0.2 mm) or more, (2) rods as large as 9.00 in. (229 mm) in diameter, ( 3 ) strip barswiththicknesses in the range0.015-6.50 in. (0.38-165mm)anda maximum width of 9.00 in. (229 mm), and (4) tubing and pipe with 0.085-

Processing of Lead Products

357

Table 3 Chemical Lead Pipe Nominal Sizes and Lead Industries Association, New York.) I.D. in.

6.25 9.5 25.4 12.5

O.D.

W. Th

mm

114

318 1

112

15.9

518

19.1

314

25.4

I

31.8

1-114

38.1

1-112

44.5

1-314

50.8

2

63.5

2- 112

76.2

3

mm 3.18 6.35 3.18 6.35 3.18 6.35 9.5 3.18 6.35 9.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5

Weights 1611. (Courtesy of

in.

wt.

mm 12.5 19.1 15.9 22.2 19.1 25.4 31.8 22.2 28.6 34.9 25.4 31.8 38.1 44.5 31.8 38. I 44.5 50.8 38.1 44.5 50.8 57.2 44.5 50.8 57.2 63.5 50.8 57.2 63.5 69.9 57.2 63.5 69.9 76.2 69.9 76.2 82.6 88.9 82.6 88.9 95.3 101.6

in. 112 314 518 718 314 1 1 - 114 718 1-118 1-318

I 1-114 1-112 1-314 1-114 1-112 1-314 2 1-112 1-314 2 2- 114 1-314 2 2- 114 2- 112 2 2- 114 2- 112 2-314 2- 114 2- 1 12 2-314 3 2-314 3 3-114 3- 112 3- 114 3- 112 3-314 4

kglm

I blft

1.07 2.87 1.44 3.60 1.80 4.32 7.54 2.16 5.03 8.63 2.52 5.76 9.70 14.39 3.23 7.19 11.86 17.26 3.96 8.63 14.02 20.13 4.673 10.07 16.18 23.01 5.39 1 I .S0 18.33 25.89 6.12 12.95 20.49 28.77 7.50 15.82 24.8 I 34.53 8.99 18.69 29.12 40.27

0.72 1.93 0.97 2.42 1.21 2.90 5.07 1.45 3.38 5.80 I .69 3.87 6.52 9.67 2.17 4.83 7.97 1 1.60 2.66 5.80 9.42 13.53 3.14 6.77 10.87 15.46 3.62 7.73 12.32 17.40 4.1 1 8.70 13.77 19.33 5 .04 10.63 16.67 23.20 6.04 12.56 19.57 27.06

Chapter 3

358

Table 3 Continued I.D. mm 88.9

in.

mm

3-112

3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 3.18 6.35 9.5 12.5 6.35 7.94 9.5 12.5

101.6

4

114.3

4- 112

127

5

139.7

5-112

152.4

6

177.8

7

203.2

8

254

10

304.8

12

/Vole:

wt.

O.D.

W. Th in.

mm 95.3 101.6 108.0 114.3 108.0 1 14.3 120.7 127.0 120.7 I27 133.4 139.7 133.4 139.7 146.1 298.5 146.1 298.5 158.8 165.1 158.8 165.1 171.5 177.8 184.2 190.5 196.9 203.2 209.6 215.9 222.3 228.6 260.4 266.7 273.1 279.4 31 1.2 317.5 323.9 330.2

in. 3-314 4 4- 114 4- 112 4- 114 4- I12 4-314 5 4-314 5 5-114 5- 112 5- 114 5- 112 5-314 6 5-314 6 6-1/4 6- I 12 6- 114 6- 112 6-314 7 7-114 7- 1I2 7-314 8 8- 114 8- 112 8-314 9 10-114 10- 1/2 10-314 11 12-114 12- 112 12-314 13

kglm

Iblft

I 0.44 21.59 33.47 46.07 1 1.87 24.47 37.79 5 I .82 13.3 1 27.34 42.13 57.55 14.76 30.24 46.43 63.25 16.19 33.1 1 50.75 69.1 17.63 35.99 55 .07 74.86 20.5 1 4 1.75 63.70 86.38 23.40 47.50 72.35 97.89 29.14 S8.98 89.53 120.83 70.48 88.55 106.79 143.83

7.0 1 14.50 22.47 30.93 7.97 16.43 25.37 34.79 8.94 18.36 28.29 38.64 9.9 1 20.30 31.17 42.53 10.87 22.23 34.07 46.39 I 1.84 24.16 36.97 50.26 13.77 28.03 42.77 57.99 15.7 1 3 1.89 48.57 65.72 19.57 39.63 60.16 81.19 47.36 59.50 7 1.76 96.65

I.D. = inside diameter; O.D. = outside diameter: W.Th. = wall thickness; Wt. = weight.

Processlng of Lead Products

Figure 39 A typicalvertical cock.)

359

extrusion press [331]. (Courtesy of Dr. S. A. His-

Chapter 3

360 9.00 in. (2.2-229mm)outsidediameter.Customshapeswitha

CCDas

large as 9.00 in. (229 mm) can be made.

4.

ImpactExtrusionandDeepDrawing

Although all the commonleadalloyscan be impactextruded, industrial applications have generally been limited to common desilverized lead and the antimonial lead alloys [2,338]. The majorapplication of impact extrusion of common lead and antimonial lead is in the production of collapsible tubes. Closures for the tubes are also impact extruded, but, in many cases, plastic caps have displaced lead caps. Impact extrusion offers a simple method of preparing thin-walled tubular lead-tin alloy preforms for soldering operations. This procedure also is a simple way to prepare shouldered bushings. The sequence of operations in fabricating a tube by impact extrusion is essentially the same for all materials. Blanks are prepared by punching disks of the desired diameter from the rolled sheets of lead or tin-coated lead. The thickness of the sheet determines the length of the tube. The blanks are generally punched with a tool that forms a slightly dished surface. After blanking, the slugs are tumbled for a short time with a suitable lubricant, which may be mineral oil, vegetable oil, a mixture of oil and talc, or various other lubricants. The formation of a collapsible tube requires a combined backward and forward extrusion. The neck is formed by forward extrusion against a spring that limits the distance the metal flows and, thus, controls the length of the neck. The walls are formed by backward extrusion. The thickness of the blank is calculated to produce a wall somewhat longer than that required for the tube in order to permit trimming the irregular end that results from extrusion. The rise in temperature resulting from impact extrusion is sufficient to raise the temperature of lead and tin alloys into the hotworking range. Therefore, the tubes formed from these metals are soft and ductile as they come from the press and are ready for trimming and decorating. Theextruded tubes, trimmedandprovidedwiththreads, are finally lacqueredand printed. In somecases,topreventcorrosion, the tubes are sprayed internally with wax. Secondary operations on the extruded material include stamping, cutting to length, adhesive backing, and continuous imprinting.

5.

Extrusion of CableSheathing

Many high- and medium-voltage power cables are sheathed in lead and then buried directly in the ground or in ducts. The lead sheath provides the cable with an impermeable seal and corrosion resistance for service in soil or the ocean floor. A traditional lead-sheathed high-voltage power cable has a cop-

Processing of Lead Products

361

per core whichis heavily wrapped in oil-impregnated paper and then covered with a lead sheath. Oil impregnation or oil filling eliminates air bubbles or voids, andprevent dielectric breakdown.With the advent of high-performance polymer sheaths, the use of oil-impregnated-paperinsulation has been replaced by polymeric sheaths in low- and medium-voltage applications and these cables do not require lead sheathing when no contact with moisture or water is expected, such as in cable ducts. However, in cables buried in soil or in the ocean floor, where the impermeability to water and corrosion resistance in the aqueous environment is critical, lead sheathing is needed. At very high voltages, even when no contact with water is expected, the lead-sheathed oil-filled cables are used because of their superior resistance to dielectric breakdown and a long history of reliable performance. The lead sheath is applied on the cable by continuously extruding lead over the cable. The lead cable sheathing alloys that are commonly used are further described in detail in Chapter 4. Lead-sheathed cable is joined using extruded sleeves made of lead or a lead alloy. For lead sheathing of long lengths of cable, both ram-type presses and continuous-screw presses have been used in the past. However, in recent years, the screw press is almost exclusively used for cable sheathing. In ram-typepresses(Figure 40)[331], the lead in the container is pressed vertically down into the die chamber, with the cable moving through the die set in a horizontal direction. The lead passes through a die chamber before entering the die and is divided into two streams which flow around the cable core to join up and weld together under the influence of heat and pressure in the chamber. The container capacitiesare typically about 1 metric ton in large presses and the ingot is obtained by directly tilling the container with molten metal and solidifying it in the container. Very long lengths of sheathed cable are made by extruding one charge after another. The lead alloy needs to be free from oxides, large intermetallic-phase particles, or other impurities to obtain a sound pressure weld, a good structural integrity, and mechanical properties sufficient to withstand stresses imposed during service. Obtaining a clean supply of metal, by siphoning from the tundish, at a level below the oxide cover is one way of avoiding the large second-phase particles. Figure 41 shows a Glover tray system that provides a liquid metal supply to the press container in this manner 133I]. Otherways of avoidingoxides in the liquid-metalfeedinclude the transfer of metal to the container under vacuum (Figure 42) [331] or under a protective gas and the use of traps where the oxides are allowed to rise and can be separated. Although the solubility of oxygen in lead is very low, -2 ppm at the melting point and about 4-8 ppm at 360°C, the possibility that the dispersions of small particles of lead oxide in the ingot used for

362

Chapter 3

1 , power

stroke

Figure 40 A schematicdiagram of atypicalram-typeextrusionpress sheathing (331 I. (Courtesy of Dr. S. A. Hiscock.)

for cable

melting can be carried over into the charge requires some care in the handling of liquid-metal transfer to the press container. In continuous-screw presses, the molten metal is fed continuously into the rear of an Archimedes screw rotating in a barrel. The screw and barrel are water cooled. As lead metal is pushed forward by the screw, it solidities and is pushed into the die set. H. Folke Sandlin, AB manufacturer of Hansson-Robertson presses is now the primary supplier of new screw extruders for cable-sheathing applications. In the Hansson-Robertson machine (Figure 43) [331], the screw and barrel are at right angles to the extrusion direction so it can be considered similar in operation to a ram pipe press but with a solid screw instead of a ram to press the lead into a die chamber (Figure 44) [331]. Themelting pot temperature is around 380°C. The liquid lead from the melting pot passes through various zones of the melting pot, and then to the gravity feed pipe, via the melting pot outlet valve. The melting pot is maintained at around 380°C. The electrically heated feed pipe supplies the liquid metal to the screw housing. As the liquid lead moves through the

363

Processing of Lead Products

Cross-head

Ram retracted at end of extrusion

Lead enters through ports

I"y

Conlcalsheld

Timperature recorders

I

,

Ram loweredto close portsIn preparation for power stroke

Hydraulic ram

Figure 41 A verticalpress with the Glover traysystem which provides a liquidmetalsupply to the continuous press container 13311. (Courtesy of Dr. S. A. Hiscock.)

screw housing, it is solidified. The solid lead is forced into the die block at pressures of up to 200 MPa. The die block forms the lead into a tube as it passes through the extrusion core and die. At this point, the material is at a temperature of 200°C. As the lead sheath is applied to the cable, it is immediatelycooledtopreventdamageto the cable. The concentricity and thickness are controlled to within 0.05 mm.The progress of the sheath through the die is sufficient to move the insulated cablecorewithonly moderate pressure being exerted on the core itself. In the Hansson-Robertson extruder, the lead is keptmolten for much of the screw length, thus reducing the stress on the tooling. Tables 4-6 provide operational data for the extrusion of lead alloy cable sheathing in Hansson-Robertson extruders [339]. Table 7 providesa list of Hansson-Robertsonextruders currently operatingworldwide [340]. The screwmachineswork well with lead and

364

Chapter

Figure 42 A feeding system to provide liquid metal to the continuous lead press container under vacuum [331]. (Courtesy of Dr. S. A. Hiscock.)

Figure 43 An overview of the Hansson-Robertson cable-sheathing press [331]. (Courtesy of Dr. S. A. Hiscock.)

365

Processing of Lead Products

Hansson-Robertson Figure 44 The cross section of the screw extruderinthe cable-sheathing press 13313. (Courtesy of Dr. S. A. Hiscock.)

Table 4 Melting Pot Sizes Used in Hansson-Robertson Extruders [339]. (Courtesy of H. Folke Sandlin AB, Sweden.) Melt pot size (tons) 10

18 30 60

Maximum output (kg/min)

Normal ingot size (kg)

Maximum ingot size (kg)

25 40 70 120

30-60 30-60 30-60 30-60

500 1000

loo0 1000

366

Chapter 3

Table 5 Output Rates and Range of Diameters of Lead Cables Extruded in Hansson-Robertson Extruders [339]. (Courtesy of H. Folke Sandlin AB, Sweden.)

Machine size

5

Output'' (kg/ min)

Die block size (in.)

Lead tube outer diameter (mm)

23-25

7- 112 9 II

32-35 36-38 32-35 32-35 32-35 50-55

9 I IB

6-50 9-85 10-1 10 9-85 9-85

11

10-1 10

12-1/4

85- 125 85- 1 50 9-85 10-1 10 85-125 85- 1 50

13-114 I IBL 1 IL

12-114 13-1/4

"Output tigures for tube diameters above 25 mm and wall thickness greater than I .S smaller diameters, ouput will be slightly lower.

111n1. For

Table 6 Extrusion Rates and Die Block Temperatures for Hansson-Robertson Extruders for Different Lead Alloys 13391. (Courtesy of H. Folke Sandlin AB. Sweden.)

Material

output (kg/niin)

Die block temperature

3R

3RT ~~

Pure Pb E' E I /2c B' B PbTeCu F3 PbCu PbTe

Max. 23-26 16-18 20--25 14-16 10-14 20-25 16-18 25-30 25-30

210 205 205 215 190 1 x5 218 I95 210 205

4R ~

200 I95 195 208 I80 I70 212 180

200 195

265 255 255 265 250 245 267 265 265 260

Processing of Lead Products

367

Table 7 List of Hunsson-RobertsonExtrudersCurrently Operating Worldwidc 13401. (Courtesy of H. Folke Sandlin AB, Sweden.)

Continent/country die North America Canada Mcxico Unitctl States

Extruder model (machine size/ size in inches)

511 1

1

319

2

419

I 1 IO 1

411 1 511 1 511 I L

South America Brazil Africa Algeria South Africa

No. of units"

319

2

317 419 317 319

419 319 411 I

Asia China

India

411 1 12 114 13 114 319 411 I

419 319 311 1 Pakistan Korea Japan

317 319 411 1 317 319 419 411 1 4/13 114 511 I

9 II 12-114

9 I 1 2

2 2 I 1 1

2 2 2 1

4 II I 3 2 1 S

Chapter 3 Table 7 Continued

ContinentJcountry die Australia Australia New Zealand Europe Austria

Extruder model (machine size/ size in inches) 319 411 1

2 I

319

1

319

1 1 3 1 1 1

419 411 1

Belgium

317

Bulgaria

411 1 319 411 1

CIS

319 419 411 1 511 1 13-114

Czechoslovakia

No. of units"

2

S 3

9

319

11 1 1

411 1

S

Denmark

317

1

2

Finland

411 1 1

317 319 419

411 1

France

Germany

GreatBritain

317 319 419 411 I SI1 1 117 319 419 411 1 12-114

317 319 419 411 1 511 1 12-114

1 2 1 3 1 6 4 2

7 I 1 4 2 8 1 I 4 7

8 2 2

369

Processing of Lead Products Table 7 Continued

ContinentJcountry Greece Netherlands

Hungary Italy

Northern Ireland Norway Poland Rumania Spain Sweden

Switzerland Turkey Yogoslavia

"Until 1992.

Extruder model (machine size/ size die in inches) 319 411 1 311 319 419 411 1 511 1 12-114 411 1 319 419 411 I 511 1 411 1

311 311 112 319 411 1 419 411 I

I 311 419 411 1 511 1 317 411 1

311 1 319 419 411 I

No. of units''

7 1 2 1 2 4 1 1 1

6 3 6 4 1 1 1

2 2 2 2 1

3 4 1 1 2

3 1 1

2 1

370

Figure 45 Hiscock.)

Chapter 3

Pirelli screw extruder for cable sheathing [33 l]. (Courtesy of Dr. S. A.

dilute lead alloys. Due to segregation of Sb during solidification of Pb-Sb alloys, difficulties are encountered and ram-type machines provide an alternative in such cases. Another screw-type extruder is the Pirelli press (Figure 45) [331]. In this design, the lead passes along both the outside and the inside of the hollow screw joining up in a four-port bridge core die to form pressure welds in the sheath before passing through the die. Compared to the HanssonRobertson extruder, the screw length is longer. Small presses for the manufacture of flux-cored solder wire operate on a similar principle to cable-sheathing presses with a vertical r a m pressing the lead into a horizontally aligned die set. However, instead of a cable core, flux is passed through the center of the extrusion through a tapered nozzle seated in the mouth of the die.

B. Rolling Rolling is commonly used in the breakdown of cast ingots of metals to billets, slabs, sheet, strip and foils. These shapes may further be used to

Processing of Lead Products

371

producedesiredforms by othermetalworkingprocesses.Rolling is the principal method of producingsheetsandfoils of lead. In rolling plastic deformationoccurs by passing the material between the rolls. Rolling involves compression of material between the rolls under nearly plane strain conditions. Depending on the number of rolls i n a given rolling stand, the rolls are classified as a 2-high, 3-high, 4-high, cluster (Sendzmir), or planetary type mill. Two high-rolling mills are employed in the production of lead sheet. Figure 46a illustrates the rolling process schematically [324]. Here, a strip of initial thickness H,, enters the rolling mill with a velocity V,, and exits with a thicknessH , and velocity V,. The roll with a radiusR and surface velocity V , compresses a strip of length I. The surface velocity of the roll is less than that of the strip until the neutral point N is reached. This helps to pull the strip due the friction between the roll and the strip. The load, L , per unit width of the strip is obtained by considering the strip to be made up of a series of slabs with an inclined flat surface and applying the planestrain condition

and where nl is the shear factor, which is a constant for a given material temperature of extrusion, and varies from 0 to 1, U is the effective stress, and h is the average strip height. The distribution of the compressive stress component uLalong the rolling direction is obtained by uz =

-

(2) ( In

h,,

)

+hK, , A x

where K , = -2 tan a and K? = (2/V5)(u/K,) + (2/fi)n?u( 1 rolling torque can be estimated by

T=

1;

+ tan'a).

The

R CIF

where XD is the length of the deformation zone, R is the roll radius, and F is the tangential force on the roll. One of the problems in the rolling process relates to the estimation of spreading of the strip in the width direction (Figure 46b). In the rolling of thick plates, the deformation occurs in three dimensions. The spread is defined as an increase in width as a percentage of its original width. The spread increases with the increase in the amount of reduction, the increase in in-

372

Chapter 3

(4

Deformation Zone

Top View of the slab being rolled

Figure 46 (a) A schematic diagram of the rolling process and (b) the spreading of the strip in the width direction [324]. (Courtesy of ASM International.)

Processing of Lead Products

373

terface friction, the decrease in the plate width-to-thickness ratio, and the increase in the roll diameter-to-plate thickness ratio. In addition, plate edges bulge with increasing reduction and friction. The flow is complex and difficult to analyze. Most of the studies on the spread of the plates during rolling are experimental in nature and empirical formulas are derived based on these evaluations. In the case of lead deformation, the spread can be estimated using the empirical relationship [2]

where h and h represent the width and height of the strip, respectively, D is the diameter of the rolls, and C is a constant estimated to be 0.19 for lead and lead antimony alloys. Figure 47 presents the breadth and thickness reduction for various h/h ratios and roll surface roughnesses [341]. The h/h ratios shown in this figure are smaller values than those usually encountered in practice. For the range of h/h ratios shown in Figure 47, the spreading with rough surface increases more rapidly than with smooth rolls at high values of D/h. In practice, the material to be rolled has a high initial width, and the spreading is very small. Figure 48 presents experimentally determined relationship between resistance to deformation, antimony content, and degree of deformation of lead-antimony alloys (3421. The resistance to deformation term, Kwd,in this

Thickness decrease (mm)

Figure 47 The breadth and thickness reduction for various h/h ratios and roll surface roughnesses [2,34I]. (Courtesy of Springer Verlag, New York.)

Chapter 3

374

Decreaseof lhickness (YO)

Figure 48 Variation of resistancetodefomlation.antimonycontent,and degree of deformation of lead-antimony alloys 12,3421. (Courtesy of Springer Verlag, New York.)

figure is actually the extrusion constant defined earlier. The initial material used i n determining the plot in Figure 48 is a cast alloy, 80 mm X 80 mm in cross section, that was annealed at 100°C prior to deformation. Although the resistance to deformation of commercial lead constantly increases with the amount of rolling, a maximum of K,,,', at a reduction of S-7% becomes more and more marked with increasing antimony content. This maximum occurs due to the hardening of antimonial lead and the onset of dynamic recovery and recrystallization above a critical amount of reduction. The most favorable region of deformation is thus at quite small reductions of thickness and those of 1S-20%. With respect to energy consumption, the most favorable ratio of thickness of material to roll diameter was found to be 0.10 in this work. From the difference in the work of rolling, as calculated from the torsional moment and the rolling load, the coefficient of friction for rolls and material was determined to be between 0.01 and 0.20. Two high-reversing-rolling mills with 1 -4-m-long rolls are employed for the production of lead sheets that are used mainly for building purposes and chemical plant fabrication. Figure 49 shows a typical rolling mill used in the production of lead sheets [343l. The mill parameters depend on the scale of the operation and the sizes of the sheet required. In a modern plant with a large annualthroughput, a typical mill has rolls about 500 mm in

Processing Products of Lead

375

Figure 49 Rolling mill used in the production of milled lead sheets [343]. (Courtesy of Lead Development Association, London.)

diameter and 1500 mm in length. Breaking down cast slabs about 2 m long X 1 m wide and 100 mm thick is done at 100-180°C with rolling speeds of between 30 and 50 m/min down to about 30 mm thickness. Lighter reductions are then usedat higher speedsof around 100 m/min for the finishing passes. The reduction per pass in finish rolling is below 1 mm, as folds are formedwithhigherpressures.Oilemulsionisnormallyused in modem practice for cooling and lubrication. The final operations consist of edge trimming on a separate line and cutting and recoiling to give several small coils. Most grades of lead and lead alloys are rolled without much difficulty, but antimonial lead alloys are more proneto edge cracking than commercial lead. Lead foil refers usually to thicknesses of less than 0.4 mm and produced by rolling in small mills in thicknesses down to about 0.005 mm [2]. In order to achieve uniform thickness, the finished sheets are rerolled without 3-4 m in width and up to 20 m in pressure. A lead sheet can be made length. The typical size sheet, however, is about 3 m wide and 6 m long. Lead sheet thinner than 3/64 in. is usually cast instead of production by rolling. Sheet thickness is often specified by weight with each l-lb/ft' (4.88 kg/m2) equal to approximately 1/64 in. (0.4 mm) of thickness (Table 8) [61]. of lead sheets Table 9 presents the British Standard (BS) code for thicknesses [61]. Standard lead strips have the dimensions of 75 mm X 600 mm, which

376

Chapter 3

Table 8 Sheet Lead Thicknesses and Weights [61]. (Courtesy of Lead Industries Association, New York.) Weight Ib/ft2 314 1

1-112 2 2-112 3 3-112 4 5 6 8 10

12 14 16 20 24 30 40 60

Approximate thickness kg/m’

in. (decimal)

in. (fraction)

mm

3.66 4.88 7.32 9.76 12.21 14.65 17.09 19.53 24.41 29.29 39.06 48.82 58.59 68.35 78.12 97.65 117.18 146.47 195.30 292.95

0.01 17 0.0156 0.0234 0.03 12 0.0391 0.0468 0.0547 0.0625 0.078 1 0.0937 0.12.50 0.1563 0. I875 0.2188 0.2500 0.3333 0.4000 0.5000 0.6667

31256 1/64 31128 1/32 51128 3/64 71128 1/16 5/64 3/32 1/8 5/32 3116 7/32 114 113 215 112 213

1.000

1

0.297 0.396 0.594 0.792 0.993 1.19 1.39 1.58 1.99 2.38 3.18 3.97 4.75 5.56 6.35 8.47 10.16 12.70 16.93 25.4

Table 9 The BS Code for Thicknesses of Lead Sheets 1611. (Courtesy of Lead Industries Association, New York.) BS 1178, 1982 Code No.

Thickness (mm)

Weight (kg/ni’)

Weight (Iblft’)

Color code

1.32 1 .8 2.24 2.65 3.15 3.55

14.97 20.4 1 25.4 30.05 35.72 40.26

3.07 4.19 5.2 I 6.17 7.33 8.27

Green Blue Red Black White Orange

Processing Products of Lead

377

is a convenient form for many flashing and weathering applications. Sheets can be easily rolled to custom sizes or made to have sections with different thicknesses. Thick sheets, of about 1 mm thickness, are used for lead stamping. Foils for lead stamping must have faultless surface quality and require special care in their preparation. Foils of thicknesses of a few tenths of a millimeter have been introduced for wrapping cables. Tin-clad lead sheets are rolled to foil. These foils find application, for example, in the packing industry. Whereas the rolling of commerciallead offers no difficulties, antithe moniallead is less easyto roll dueto its increasinghardness.With hardness, the brittleness increases and there is a risk of cracking, especially at the edges. Therefore, antimonial lead is rolled with smaller reductions per pass. This, however, results in greater cooling of the material during rolling, which again gives rise to an increase in brittleness, resulting in greater waste on cutting. Antimonial lead clad with commercial lead showed a more favorable behavior during rolling compared with the unclad antimonial lead, both with respect to possible reductions per pass as well as of cutting losses and of power requirements. The duplex material has an advantage in regard to corrosion behavior.

111.

JOINING OF LEAD

A.

MechanicalJoints

Both mechanical joints and fusion-welded joints are used in the joining of lead. The softness and low mechanical strength of lead permit mechanical joints to be formed easily in ways which are impossible for other metals. Bossing is a way of shaping highly malleable metals. The lead sheets can be easily joined mechanically using bossing techniques. Bossing refers to shaping of metals such as a lead sheet using hardwood tools. During bossing, the sheet metal is shaped without undue thinning. Some of the tools used for shaping the lead sheet are shown in Figure 50 [344]. The ease of bossing could vary with lead alloy composition and microstructure,but the lead sheet metal workers find no significant difference among dilute lead alloy sheets. The principal types of mechanical joints are flat-lock seam (welt joint), batten seam, wood-cored roll, hollow roll, standing seam, and drip joints. These joint seams are illustrated in Figure 51 [61,344]. The style of these mechanical joints formed in the joining lead sheets is referred as a looselock joint and are designed to accommodate for thermal expansion and contraction of the sheets. The joints are also referred to as slip seams. These joints are frequently used with lead sheet and terne-coated steel to make waterproof roofs, weatherings, and flashings. The use of these joints in roofing applications is discussed in Chapter 4.

378

Chapter 3

Flat dresser. Requlred for dresslng lead sheet Rat both when settingthe workout and when fitting it In position

tool used for bow

Intendedfor bendin

Bosslng mallet. Some

use of two tools

pnor Io bossmg; but may also be used ~nfinlshmg leadworkm position

used.

Chase wedoe. Also shudc with mallet, for settinpm but it mam use IS for finlshmg leadworkm position. In usmg thls tool to finlsh leadwork care musl be laken notto dnve it too hard andthus cut deep

a

Into thelead

Figure 50 Differentbossingtools [344,344al. (Courtesy of LeadDevelopment Association and Lead Sheet Association, UK.)

Processing Products of Lead

379 FLATLOCK SEAM

BATTEN SEAM Coppm cleat fastened Lock seam.

Copper cleat fartened with coppe~nails

Rolled comer

V

l

Allowance for expanamon

Welt Joint

Batten Seam Joint

Roll-up Joint

Stand-up Seam Joint

Wood-core

Joint

Lap

Drip Joint

Figure 51 Different loose-lock joint seams [344,344a]. Association, and Lead Development Association, UK.)

(Courtesy of Lead Sheet

380

Chapter 3

B. Welding of Lead Loose-lock mechanical joints sometimes allow leakage to occur, and in a highly corrosive chemical environment, this can have serious consequences. In addition, loose-lock seams are not designed to supportlarge weight loads. Therefore, welded joints are used in equipment which handles chemicals or where leak tightness andstrongerjoints are required. The relatively low melting point alsomakesfusionwelding relatively easierand it requires simple but special techniques. Lead burning is a term frequently used to refer to fusion welding of lead. The term“leadburning”has its origin to the early daysofcrude welding techniques for joining lead to lead without solder in the fabrication of a chemical plant units. Lead and lead alloys are regularly welded to make joints in a chemical plant and for joining associated pipework. Lead welding is also used for joints in lead roofing and for the construction of sheet lead linings for radiation protection in x-ray rooms. The fusion welding of lead is commonly made by oxyfuel gas-welding [344,34S]. Propane or natprocesses, using oxyacetylene and oxyhydrogen ural gasandhydrogencouldalso be usedasa fuel gas.Acetylene is the preferred fuel in many countries, and in the United States, hydrogen is preferred because of the fine flame size that can be obtained which allows good control of the weld-bead size. With oxyacetylene,the higher pressure needed to obtain a small flame tip disrupts control of the liquid lead pool. Oxyhydrogen and oxyacetylene mixtures can be used for welding in all positions. Oxyhydrogen is especially useful in providing good weld pool control because of its localized heat input. Oxynatural gas and oxypropane are limited to the flat position because of the greater difficulty in controlling weld pool size and shape. In all cases, the proportion of oxygen is adjusted to obtain a neutral flame. Reducing flames with organic fuels tends to deposit soot in the joint, whereas excessive oxygen will oxidize the lead, inhibiting wetting. Flame intensity is controlled by varying the welding torch tip and tip size to control the flow volume of fuel gases and the flame shape. Tips from drill size 78 to 68 (0.4 1-0.79 mm in diameter) are commonly used. Larger tip sizes are used for greater thicknesses and are influenced by the type of joint being welded. Butt, lap, and corner joints welded in the flat position and lap joints welded in the horizontal position require more heat than vertical welds and will require larger tip sizes to achieve higher fuel gas flow rates. Gas pressures between 1.S and S psi (10.3 and 34.5 kPa) are typically used and will produce flames between 1.5 and 4 in. (38 and 102 mm) long [34S]. Filler metal is available in rod form between 1/8 and 3/4 in. (3.2 and 19 mm) in diameter. Filler metal can also be cut from the base metal being

Processing Products of Lead

381

used for the job, in widths typically of 1/4 and 0.5 in. (6.4 and 12.7 mm). The composition of the filler metal should be similar to the base metal to obtain similar melting and mechanical properties. The filler metal must be scrupulously cleaned before use, either by wire brushing or preferably by shaving off a thin layer of metal to expose fresh lead. It is essential that the mating edges, joints, and adjacent surfaces of the lead be shaved clean, as the fluxes (rossin or tallow) used are not effective in removing surface contamination. There are three important type of joints used to unite lead sheet, four types for joining lead pipe, and one type for joining lead-sheathedcable.

1.

Lead Sheet Joints

The three types of joints used for welding sheet lead are butt, corner, and for expansionandcontraction, lap (Figure52) [345]. Lapjointsprovide avoid the possibility of burn-through, often do not require filler metal, and are easily made. For these reasons, lap joints are also almost always used for vertical and overhead welding. Butt and lap welds can be used for flat

in.

0.06 In. MINIMUM

0.13 MAXIMUM (33 mm)

t a ) Square-Groove Butt Joint

11.62 mm1

0.14 in. MiNlMUM

13.55 mm1

(b) V-Groove Butt Joint

J

( C ) Welded Flanged-Edge Butt Joint

(d ) Welded Corner Joint

(e) Fillet Welded Lap Jolnt

Figure 52 Different typesof fusion welded leadsheetjoint Lead Sheet Association, UK.)

13451. (Courtesy of

Chapter 3

382

work,although butt welds are preferredwhen lap weldsgive an overall thickness greater than desired. Lap joints of lead sheet thicker than 1/4 in. (6.4mm) havewidegapsbeneaththem.Therefore, butt joints are often employed in flat-position welding when the lead sheet is thicker than 1/4 in. (6.4 mm). In addition,whena lead sheet is in ahorizontal Rat position, pressure or its own weight tends to limit thermal expansion and contraction. Stress and strain become focused on a localized area, causing the bend in the lap joint to act as an expansion joint. This promotes failure of the lap joint. To prevent this situation from occurring with a heavy lead sheet, butt joints are used with separate expansion joints and bends. The butt joint also providesfewersurfacediscontinuities, especially with the thicker lead sheets. The flange joint is used only in special applications with a lead sheet 1/16 in. (1.6 mm) thick or less. In all cases, adequate support of the joint is necessary and can be ensured by positioning the base metal securely against supporting materials. A square-groove, butt-joint design can be used with a l/8-in. (3.2-mm)thick sheet lighter than 8 Ib/ft’ (39 kg/m2).A 90°, V-groove butt joint is used for heaviersheet.Lead sheet is partially beveled to fornl the V-groove, leaving a root face of 1/16 in. (1.6 mm) atthe bottom of the sheet. This permits easy burning without substantially increasing the risk of completely melting through the lead. These typical butt joints are illustrated in Figures 52a and 52b. The weld grooves and sheet are shaved clean for 1.25 in. (32 mm) beyond the grooves. Butt joints are held in proper alignment for final welding by tacking or flow welding (burning-in), in which the upper meeting edges of lead are fused for a short distance, as shown in Figure 53 13451. Flanged-edge butt joints and corner joints (Figures 52c and 52d) also maybeused with lead weighing less than 4 Ib/ft’ (19.5 kg/m’). For the flanged-edge butt joint, the edges of the sheet to be joined are shaved clean, as are 2-in. ( 5 l-mm) widths on the top and bottom of each sheet adjacent to the edges. A flange 1.5 times the sheet thickness is then formed by bending the edge of the sheet outward. The bent edges are then fitted together and welded as a butt joint.

BURNING IN

L

SPOT

Figure 53 Tack and burning-in of plates to be butt-weld joints 134.51. (Courtesy of Lcad Sheet Association, UK.)

Processing Products of Lead

383

Corner joints are prepared by positioning lead sheets together at an angle, with one sheet always forming one full side of the angle. The other sheet is butted against it. Grooving of the joint is not necessary, regardless of thickness. The root faces of the sheets to be welded are shaved clean to a width of 2 in. (S1 mm), along with the joint root of the butting member. For welding corner joints in thicker sheet, the method shown in Figure S4 is more suitable than the one shown in Figure 52d. Placement of the weld will depend on whether both faces of the angle are inclined (flat position), as shown in Figure S4 (3451, or whether one face of the joint is vertical (horizontal position) as showni n Figure SS [ 344a,34S]. I n the case where one butting member is vertical, the weld is built up on the horizontal face and its sides fused into the vertical face. This results in a wide, horizontal weld. In the case where both faces are inclined, the weld isflat andmoreevenly distributed acrossbothfaces to providemore strength. Fillet-welded lap joints (Figure S2e) can be used in all positions. Typically, an overlap of 0.5-2 in. (12.7-SI mm), is proportional to the sheet thickness. All surfaces the tiller metal will contact must be shaved clean, a s well as the facing surfaces and a 1.25-in. (6.4-mm) border beyond the weld face.

BURNING-IN

FIRST PASS

SECOND PASS

384

BURNI'NG-IN

Chapter 3

PASS FIRST'

SECOND PASS

Figure 55 Comer seam one face vertical-horizontal Lead Sheet Association, UK.)

position [345].(Courtesy of

A variation of the lap joint is the horizontal lapped seam weld on an inclined face. To allow joining of this configuration, the edge of the outer sheet is angledoutwardover the outer 1/4 in. (6 mm) of the inner sheet width, forming a groove between the two sheets, as shown in Figure 56a [34S]. The groove angle should be approximately 45". Filler metal is fused into the groove to form the weld, as in Figure 56b [345].

2. Pipe Joints The pipe joints can be classified into butt, cup, lap, and flange joints. Figure S7 [345] illustrates the butt, cup, and flange joints. The lap joint is similar to that shown in Figure 52e, except that a pipe instead of a flat-sheet geometry is used. The butt joint is generally preferred, and for lead heavier than 10 lb/ft' (47.8 kg/m'), it is considered essential. The cup joint is used with a pipe fixed in the vertical position. The flange joint is used on largerdiameter pipes and lead-lined steel pipes. Flanges, cast or made from sheet lead, are welded to the pipe. The pipes are then joined by bolting the flanges together using a lead or other acid-resistant gasket.

385

Processing of Lead Products

(a) Preparation of Joint with a 114-in. ( m m ) Wide Groove

Figure 56 UK.)

(b)Application of Filler Metal in a Single Pass

Horizontallappedseam

[345]. (Courtesy of LeadSheetAssociation,

To prepare the butt joint, a wooden turn pin is used to slightly flare the ends of the pipes to be joined when wall thicknesses are less than 1/8 in. (3 mm). As shown in Figure 57b, this procedure yields a butt joint with a slight V-shape, allowing good filler metal penetration. It is difficult to use the turn pin with pipe thicknesses greater than 1/8 in. (3.2 mm): hence, a V-groove with an angle of 45" and a 1/16-in. (1.6-mm) land, is prepared as shown in Figure57b.Thepipe ends are butted together, forminga tight joint root. The outer and inner walls of the pipe should be shaved clean for a distance of 0.5 in. (2.7 mm) from the joint. To avoid the difficulties of overhead welding, a V-shaped section can be cut at the top half of the pipe and the inner wall at the bottom of the joint welded from the inside, as shown in Figure 58 [345].The V section is then repositioned and welded to the pipe from the outside. Alternatively, T slots can be cut in the upper halves of both pipe ends. The wall sections are then bent radially outward to expose the lower half of the joint. After the lower half of the joint is welded from the inside, the wall sections are bent back to the original shape, and the T slots in the upper part of the joint are then welded from the outside. Lap or cup joints require that one side of the pipe joint be expanded to allow the other side to fit inside. These joints are most commonly used for vertical pipes, with the lap or cup always opening upward. In lap joints, an overlap equal to the pipe diameter is used. In cup joints, Figure 57a, a flare with a length equal to half of the pipe diameter is made with a turning pin on the overlapping pipe. A 45O-angle flare will produce a bevel-groove joint when the other pipe is inserted into the flare. Lap joints also can be used, but they usually require more joint preparation.

Chapter 3

(a) Cup Joint

0.25 in.

0.063 in.

(6.3mm) (1.6 mm)

(b) Butt Joints 0.25 in. 0.063 in. (6.3mm) (1.6 m m )

(C) Joining of

Figure 57

Two Pipe End Flanges

Lcad pipe weld joints [345].(Courtesy of Dr. F. E. Goodwin, ILZRO.)

387

Processing of Lead Products

Figure 58 Joint design for welding leadpipe (Courtesy of Dr. F. E. Goodwin, ILZRO.)

in thehorizontalposition

[345].

In lap joints, an overlap equal to the pipe diameter is used. The outer pipe section used to form a lap joint should be shaved clean on the edge and both inner and outer sides of the pipe wall over the length of the joint root. The inner pipe section should be shaved clean on the outer pipe wall over the length of the lap joint in addition to a I-in. (25-mm) length beyond the root face. Similarly, the inner pipe used in a cup joint should be shaved clean on its outer wall over the length of the cup in addition to a I-in. (25mm length beyond the cup and the pipe edge. The outer pipe in a cup joint should be shaved clean on the edge and on the wall interior over the length of the cup in addition to a 1/2-in. (13-mm) length of pipe wall interior beyond the root face. Large pipes can be joined by forming a sheet or by casting a shape in is the form of a flange and sleeve. In the case of formedsheet,aseam welded to complete the shape. The sleeve is then lapped over the pipe and welded in place as a lap joint. The flange ends are then butted together and butt welded. A section of a flange joint is shown in Figure 57c.

3.

Welding Positions and Techniques

Good lead burning is achieved by having clean surfaces, correct weld penetration, sufficient reinforcement, and no undercutting. Prior to welding, the meeting edges and faces of the lead should be shaved clean. Handling preis pared surfaces should be avoided. No flux should be applied. The oxide light and floats to the surface of the molten pool, where it can easily be removed. Inadequate penetration is usually the result of using too small a nozzle, which gives a flame of insufficient heat, or of progressing too fast between loadings. Over penetration can be caused by progressing too slowly between loadings when using a fast flame. To provide sufficient reinforcement of the weld, the thickness of a lead-burned seam should be about one59 shows examples third thicker than the lead sheet being welded. Figure of undercut seams in comparison with sound seams [344,345]. Undercutting can be difficult to repair. It is caused by misdirecting the flame away from the center of the joint and the filler metal. It canhappen when working

DERCUT

Chapter 3

388

'h THICKNESS

OFSHEEj

f t

CUlTING-IN

1

-

-/

FILLER METAL FUSED TO FACES BY CONDUCTION

ClJlTlNG-IN

SOUND

UNDERCUT

1

GOOD PENETRATIONJUST THROUGH SOUND

(a) Flat Butted Seam

(b) Inclined Seem LOADINGS CONDUCTION

MAINTAINED

SOUND

UNDERCUT

( c )Comer Seam

SOUND

(dl Overhand Horizontal

3 J

CUTTING-IN

UNDERCUT

Seam

Figure 59 Sound and undercut seams [345]. (Courtesy of Lead Sheet Association, UK.)

outdoors in windy conditions and when the welder takes a slow and hesitant approach to the work, such as when welding in a difficult position. In general, a semicircular or V-shape motion is used in welding lead. In this way, the molten-lead weld pool is controlled and directed by the motion of the flame, giving properly welded seams a semicircular or herringbone appearance. Fusion of the base metal is achieved by applying the flame just long enough for the heat to penetrate to the edges of the shaved area. Then, lead is melted from the filler rod into this area, with the quantity introduced determining the thickness of the seam. The leftward technique is usually employed. with the torch pointing in the direction of the weld at an angle of about 45". The working part of the blowpipe flame is immediately in front of the small cone at the tip of the nipple of the nozzle when the flame is properly adjusted. The cone of the flame should be just clear of the edge of the lead pool produced. The amount of lead melted from the filler for each pass should be sufficient to build up a layer approximately 0.08 in. (2 mm) thick. To avoid overheating with consequent excessive penetration resulting i n the formation of holes or undesirable underbead, low gas presused. Use of sures of between 100 and 300 Pa and low gasspeedsare experienced lead burners is recommended whenever a project involves ex-

Processing Products of Lead

389

tensive burning. Unlike the welding of other metals, the molten pool is not continuously maintained; instead, a series of overlapping pools are formed, each being allowed to solidify individually. Heat input is controlled by gas pressure, rate of flame progression, and the nozzlesize.Theoxyacetylenenozzlesizespreferred for lead burning for different thicknesses of lead sheet normally used in buildings are shown in Table 10 [244].

4.

Sheet Lead Positions

Flat Position. In the flat position, butt joints are most common, although flanged joints can be used for a very thin sheet, and lap joints can be used if they simplify fabrication. The position of the tiller strip and torch relative to the weld pool, weld bead, and joint for a flat-butt joint is shown in Figure 60 134.51. When working on a bench and larger welding tip being used, the torch also can be moved in a straight line. Better control is obtained in field applications by progressing with a circular or V-shape motion. Filler metal generally is not used on the first pass. For lap joints, the semicircular motionbegins on the bottomsheetandthenmovestoward the lap (see Figure 61) [34.5]. Thetorch is thenmoved in a straight line back to the bottom sheet. The slower the progression and the more pronounced the sideto-side action, the rounder will be the pattern of the seam. Filler metal is added just ahead of the flame. Procedures for producing corner joints are shown in Figures 54 and 5.5. The first stage in welding a corner joint is tacking or flow welding from

Table 10 Nozzle Sizes Usually Preferred for Lead-Burning Different Seams in Different Thicknesses of Lead Sheet (344al. (Courtesy of Lead Sheet Association, UK.)

Size of nozzle for oxyacetylene BS Code No. 4 and 5 lead butted lapped

Seam Lead-Burned Flat Flat Angle lapped Horizontal inclined Lapped face on Upright face vertical Inclined on

2 or 2 or 2 or 2 or 2 or

3 3 3 3 3

1 or 2

I or2

BS Code No. 6 and 7 lead sheet 3 or 4 3 or 4 2 or 3 2 or 3 3 or 4 2 or 3 2 or 3

Chapter 3

390

FROM FILLER DIRECTION OF WELD c

I

THIS AREA /" VERY HOT

\ THIS AREA JUST MOLTEN

CROSS SECTION

LATERAL SECTION

Figure 60 Flat-butted seam-position Lead Sheet Association, UK.)

of torch and tiller strip 13451. (Courtesy of

the edges. When both sides of the angle are inclined, the tirst pass is brought forward, justtilling the root of the weld. This is followed by a heavier second to dwell on either side of the angle pass. The flame must not be allowed because this can cause undercutting, which weakens the joint. The moltenweld pool also must be kept in the line of the pass by using a straight-line technique of welding and minimal weaving.

COMPLETED WELD

NEXT STROKE

Figure 61 Technique for weldinglapjoint Dr. F. E. Goodwin, ILZRO.)

in a Rat position 13451. (Courtesy of

391

Processing Products of Lead

Horizontal fillet joints with one face vertical (see Figure 5 5 ) are first tacked and then welded with a heavy tirst pass. When welding in the horizontal position using the circular or V-shape motion, a soft diffused flame is most desirable. The flame for the tirst pass is directed nearly vertically downward, with fusion to the vertical leg occurring only by heat conduction from the pool. The second pass is much lighter and should be pointed toward the vertical seam but without playing the torch on the vertical face. Fusion with the vertical face is again controlled by conduction. Verticul Position. Lap joints are almost exclusively used when welding in the vertical position (see Figure 62) 13451. Welding should begin at the bottom of the joint, which, in many cases, is a continuation of a flatlapped seam weld, as shown in Figure 62a. Otherwise, a backing should be used to support the initial filler metal. Using a pointed flame, a pool of lead is first melted at the base of the joint root on the underlapping sheet. The torch is then moved to the adjacent front sheet and the area melted into the weld pool, completely liquefying the overlap. The welder should try to melt off the corner of the lap edge at a 45" angle and move the liquid lead into the weld pool by following the flame path shown by the arrow in Figure 62b. The flame is then moved higher on the underlapping sheet and the process is repeated, eventually carrying the weld bead to the top of the joint. Filler metal is generally not used, the lap edges being thesource of weld metal. If tiller metal is needed, the torch should be removed momentarily after depositing a bit of tiller to allow it to

(a) Vertical Lap Joint Continuing from Flat Position

Figure 62 UK.)

(b)Welding of Vertical Seam without Filler Metal. Arrow Denotes Flame Path

Welding of vertical seams 13451. (Courtesy of Lead Sheet Association,

Chapter 3

392

solidify immediately, butnot cool appreciably. In all cases,asshown in Figure 62b, the flame should be pointed downward, and either perpendicular to the sheet surface or about 60" into the angle of the overlap. Because this is as difficult as overhead welding, it should be avoided when possible. Instead, as shown in Figure 63 [345], the edge of the lap is turned out to produce a gap less than 1/4 in. (6.4 mm) wide. The torch is held overhand and pointed into the gap. In this case, the lap is not used as filler but provides the flare in which welding is performed. A separate filler rod is used. Controlling the weld pool requires some skill. When changing from a flat-lapped weld to a vertical-lap weld, steps are formed on the flat weld on the bend, as shown in Figure 64 [345]. Welding at this bend should be done without the use of filler metal. It is always easier to weld a vertical joint that is inclined to the vertical, as shown in Figure 65 [345], rather than strictly vertical. This allows the edge of the outer sheet to be angled outward,forminga groove face in which filler metal can be melted. This makes it easier to maintain a relatively flat surface on which the weld pool can be maintained. Welding of vertical sheets is even easier in the horizontal position, as shown in Figure 66 [345]. By making a V groove in the horizontal section, as shown in Figure 66a, welds can be made easily.

Ovcr-head Position. Overhead welding of lead is not generally recommended because the high density of lead makes overhead pool control

CLEANED AREAS

(a) Location and Position of Torch at Stmrt of Stroke

(b) Motion of Torch in Making Vertical Lap Seam

(cl Single Stroke of Torch

Figure 63 Technique for welding lap joint in vertical position 13451. (Courtesy of Dr. F. E. Goodwin, ILZRO.)

Processing of Lead Products

Figure 64 UK.)

393

Lap joint on inclined plane [345]. (Courtesy of Lead Sheet Association,

very difficult. If it is necessary to weld in the overhead position, a lap joint should be used. The flame should be as sharp as possible, weld beads should be small, and the operation completed as quickly as practicable. Filler metal is rarely used and only to build the bead to the required thickness. The pressure of the flame and capillary action of molten lead into the lap seam can be used by the skilled welder to control the liquid pool. An example of this position is shown in Figure 66b.

5.

Lead Pipe Positions

For best results when welding pipe that is in the horizontal position, the work should be rotated to allow welding in the flat position. If the pipe

Figure 65 Inclined seamon a verticalface [34S]. (Courtesy of LeadSheetAssociation, UK.)

Chapter 3

394

(a) Overhand

(b) Underhand

Figure 66 Joint designs for welding horizontal joints in a vertical lead sheet using underhand techniques 13451. (Courtesy of LeadSheetAssociation, UK.)

overhandand

cannot be rotated, butt joints generally are used. The V- or T-slot methods, which allow interior welding of the bottom of the pipe joint, are described in Section III.B.2. This allows the entire joint to be welded in the flat position; otherwise, the underhand vertical position described for joining vertical and overhead sheet lapjoints will be necessary. On pipes oriented vertically, lap or cup joints should be used, allowing the flat position to be used in all cases.

C.NewWeldingTechniques 1.

Friction Stir Welding

Friction stir welding is a new welding technique that is especially suitable for making butt and lap joints in lead and lead alloys sheets [346,347]. This new technique conceived and developed during this decade by The Welding Institute (TWI) has been widely adopted by lead sheet metal industry particularly in Europe. The technique eliminates many environmental and health concerns associated with lead-burning using gas flames during lead sheet metal working on the roof and other situations. The friction stir welding technique is a derivative of conventional friction welding which enables the advantages of solid-phase welding to be applied to the fabrication at long butt and lap joints, with very little postweld distortion. It has made it possible to weld a number of materials that were previously extremely difficult to reliably weld without voids, cracking, or distortion. Although the technique

Processing Products of Lead

395

was initially applied for the joining of aluminum alloys, especially those which are often difficult to weld, it has now been applied for many other metallic alloys. To form a friction stir weld, the butt or lap joint parts are placed on a backing plate (Figure 67a) and clamped in a manner that prevents the abutting joint faces from being forced apart. A cylindrical, shouldered tool (Figure 67b) witha specially profiled projecting pin is rotated andslowly plunged into the joint line. The pin length is similar to the required weld depth. When the rotating pin contacts the work surface, heat generated by friction rapidly raises the temperature of the material at the point of contact, thus lowering the materials mechanical strength. Under anapplied force, the pin forges and extrudes the material in its path (Figure 67c) until the shoulder of the pin is in intimate contact with the work surface. At this point, the friction heating produced by the rotating shoulder pin results in a substantial hot plasticized layer of metal beneath the tool shoulder and about the pin (Figure 67d). When the workpiece is moved against the pin, the plasticized material is crushed by the leading face of the pin profile and transported to the trailing face by a mechanical stirring and forging action imparted by the

a

/ /

b

Fndion heated extruded motenal L

/ hocking plate

4

Plosticld toyer beneath tool shoulder ond about pin

Figure 67 Friction stir welding operation. (a) The parts to be joined are clamped to a backing plate; (b) a cylindrical shouldered tool with a special pin profile is positioned with its axis on the joint centerline; (c) the tool is rotated at a certain peripheral velocity and plunged into the joint; (d) plasticized metal, through friction heating, is removed until the tool shoulder is in intimate contact with the work surface; (e) when the tool is moved against the work, or vice versa, plasticized material is moved from the front to the back of the pin, thus forming a weld on consolidation as the pin and the heat source move away [346]. (Courtesy of Dr. C. J. Dawes, The Welding Institute (M), Cambridge, UK.)

Chapter 3

396

pin profile and its direction of rotation (Figure 67e). Consequently, as the welding tool proceeds down the joint line, it friction heats the abutting joint faces just ahead of the tool to a soft plastic state. It subsequently crushes the joint line, breaking up the oxide, and stirs and recombines the crushed material on the trailing side of the tool where the material cools to form a solid-state weld. All this occurs at temperatures lower than the melting point of the alloy. The welding operation is simple, energy efficient, and does not require a high level of operator skill and training. The process does not require filler wires, weld-pool shielding gas, special joint edge profiling, or oxide removal immediately prior to welding. The technique is ideally suited to automation. The welding can be done in all positions from downhand to overhead. The welding operation and weld energy input is accurately controlled. The solidphase weld formation enables the retention of metallurgical properties in alloys and metal matrix composites. Besides conventional butt and lap joints, the friction stir welding technique is suited to several otherjointconfigurations.

2.

Electrical Welding

The low welding rate (3-5 m/h for flat seams and 2-3 m/h for vertical seams) and the dependence on highly specialized lead burners, whose ability is judged even today by the artistically shaped cupping of the weld seam, have led to efforts for mechanical movement of the torch. Some increase in output (about 30%) can be gained by mechanical guidance of the torch, corresponding to manual movement by the lead burner. However, equipment of this type, fitted with automatic feed, still requires careful monitoring and inspection even though it can be operated by an unskilled lead burner. Automated electrical welding techniques have been explored as a possible economical alternative. However, electrical methods of lead burning have so far been used only occasionally. The carbon arc was tried around the turn of the century, but the high arc temperature caused vaporization of the lead. Recently, promising experiments have been carried out with tungsten inertgas arc welding, commencing with Russian investigations. In this method, the arc is directed between a tungsten electrode and the base material by means of a current impulse, giving an effect similar to that in manual autogeneous welding, and overheating is suppressed [348].

D. Welding Safety and Inspection Because of a risk of exposure to lead fumes, adequate safety procedures need to be followed. The health and safety issues have been discussed in Chapter 1 and are also presented in Chapter 5. Inspection of lead welds is

Processing Products of Lead

397

usually confined to visual examination to ensure that there is no undercutting, there is no oxide, porosity or cavities, there is adequate penetration without run-through, and there is an even, regular weld pattern.

E. Soldering of Lead and Lead Alloys In the soldering process, only the filler material is melted and the base material that is to be joined remains intact as a solid. This requires the filler material (solder) to have a significantly lower melting point than the lead alloy sections being welded. In this section, only soldering of lead to lead or lead-coated products is discussed.The use of lead and lead alloys in soldering other metals is discussed in Chapter 4. Lead and lead alloys are easily soldered when proper care is taken not to melt the base metals, which also have relatively low melting temperatures. Solder joints in lead are generally confined to plumbing, some architectural uses, and lead-sheathed cables. The use of soldered lead joints in the chemical construction field, where highly corrosive chemicals are confined or transported, is not generally recommended. Such joints should be welded. Solderalloys must always be selected so that they can be worked without melting the base metal. Pure lead melts at 327"C, and one of the popular lead antimony alloys, SbS, melts at 240°C. This difference includes a reasonable and practical temperature range for soldering of 75°C. However, to solder lead alloys that could have significantly lower melting temperatures, a lower melting solder should be used. The lowest melting temperature is obtained with the eutectic composition of 63% tin. It melts at 180°C but lacks the mushy range, which can be desirable for some soldering techniques such as wiping. A wide variety of solder compositions are covered in ASTM specification B32. An alloy commonly used for joining lead sheet is SN50, which contains essentially SO% tin and SO% lead. Wiping is a special technique for soldering lead and uses alloys SN30B, SN35B, and SN40B. The numeric part of the ASTM specification indicates the percentage of tin, and these alloys also contain up to 2% antimony, with the balance lead. The solders are solid up to around 182°C and provide a pasty or working range of 56°C. Solders containing 34.5% tin, 1.25% antimony, 0.1 1% arsenic, and the balance lead are widely used in joining lead-sheathed power cables. The arsenic is added to promote a fine-grain structure, and the antimony is added for higher strength. The soldering of lead and its alloys can be accomplished without the useof the corrosive fluxes. Tallow and rosin fluxes and stearic acid are generally used. Nonactivated rosin flux, which does not contain activating

398

Chapter 3

Table 11 Nonactivated Rosin Fluxes ILZRO.)

13451. (Courtesy of Dr. F. E. Goodwin,

Composition, wt. o/o Water white rosin Flux 1 2 3 4 S

Cetyl Glutamic acid pyridiniurn hydrochloride bromine Stearine hydrobromide

Hydrazine Alcohol

10-25 40 40 40 40

2 4

4 2

Bal." Bal. Bal. Bal. Bal.

"Alcohol, turpentine, or petroleum

agents such as amines, is suitable for soldering lead. Typical compositions are shown in Table 1 1 [345]. The areas to be joined should be thoroughly cleaned by wire brushing or shaving. Tallow or stearic acid flux should then be applied promptly to prevent reoxidation of the cleaned areas. Excessive use of cleaning tools should be avoided. Their overuse may cause fatigue failures due to chatter and thinning of the lead near the critical section of the joint. To confine the solder within the joint and help form and build a bead, gummed paper strips can be used. Also useful is plumber's soil, a mixture of lampblack, glue, and water. The low melting point of lead and its alloys limits the choice of heating methods. Soldering irons are usually used for soldering sheet lead joints. In wiped joints, the heat for soldering is supplied by molten solder that is poured over parts such as pipe or cable sheathing, thereby both fusing and wetting the base metal while cooling the bulk of the solder, making it pasty and workable.

1. Joint Types Lap Joinrs. Lapjoints are more satisfactory than butt joints and should be made with a minimum lap of 3/8 in. (9.5 mm)for up to and including a 1/8-in. (3.2-mm) thick sheet (8-lbsheet).The two sheets that form the lapshould be cleaned and fluxed with tallow. The cleaned and fluxed side of the bottom sheet should extend 1/8 in. (3.2 mm) beyond the leading edge at the lap. Theedge and upper side of the top sheet, to a distance of approximately 3/8 in (9.5 mm), should also be cleaned and

Processing Products of Lead

399

fluxed. The sheets are then fitted together and dressed down with a wooden or rubber mallet to fit smoothly. Soldering is usually done with an iron and a 50% tin, 50% lead solder, first by tacking at intervals with solder. Then, application of additional flux is often advisable. The flux source maybe within rosin-cored or stearinecored wire solder. When bar solder is used, stearineor powdered rosin should be applied to the joint.

Lock .Joinfs. Lock joints are lap joints which have been mechanically formed before joining to prevent movement (see Figures 68) 13451. They provide considerably more strength and are preferred whenever the joints are to be in tension. They are made in much the same way as lap joints, using locks of 1/2 in. ( 1 3 mm) or more. The solder should flow between the two lower root faces and contact with the lock. Blrtt .loiwfs. Butt joints are the least desirable type for joining lead sheets and are made using a process termed solder welding. This technique should be confined to those situations in which it is impractical to use other joint designs. The abutting edges of the lead sheet are beveled with a shave hook t o make an angle of 45" or more with the vertical. These edges are placed firmly together and tacked at intervals of 4-6 in. (102-152 mm). Gummed paper strips pasted parallel to the seam and 1/4-3/8 in. (6.3-9.5 mm) away aid in building up the solder and reflowing it in the refinishing operation. Additional flux, a s described in the lap-joint section, is advisable. Solder is fed into the joint and melted by the soldering iron as it is drawn along the joint root. Sufficient solder should be applied to build a slightly convex surface.

P i p .loints. In joining lead pipes, flanged joints made in a bell-andspigot manner as shown in Figure 69 are recommended [344,345]. The flared end is that into which the liquid will flow. The spigot end is beveled to fit snugly into the flared end.The entire area to be wiped is shaved clean,

(4

(b)

(c)

Figure 68 Lock joints used in soldering lead [345].(Courtesy of Dr.F. E. Goodwin, ILZRO.)

400

Chapter 3

Figure 69 Bell-and-spigot joint for pipe soldering 13451. (Courtesy of Dr. F. E. Goodwin, ILZRO.)

lightly, as is the contacting area within the joint. A thin coat of tallow is then applied. The area beyond the joint root on both sides is then coated with plumber’s soil or paper to prevent the solder from adhering at these points. Thejoint is assembled, the flare end is dressed down tightly by swaging with a wooden tool, and the entire assembly is braced so that it will not move during the subsequent soldering operation.

Wiped Joints. In the case of a wiped joint, wiping solder is heated in a ladle to a temperature of 315°C. To join horizontal pipe, the joint is wiped by slowly pouring the solder on top of the joint while containing the solder with a tallow-coated cloth. When the solder is in its pasty stage, the operator wipes or forms the joint. When completed, the joint should be chilled. In vertical pipe, joints are prepared and wiped in much the same manner, except that the solder is poured around the pipe at the top of the joint and the cloth is held directly under the ladle at the bottom of the joint. The ladling or splashing-on of the solder is continued around the joint. Branch Joints. Branch joints in lead pipe are made by cutting a small oval-shaped hole in the main line and drawing up sufficient lead to form a collar or hub into which the beveled branch line is fitted snugly. Preparation or wiping is essentially the same as previously described. Cup Joints. Cup jointsaresimilarto bell-and-spigot joints,except that the flared end is not dressed down and a soldering iron is used rather than wiping. These joints can be made only in the vertical position, although

Processing Products of Lead

401

they can be used in any position. Preparation of the joint includes beveling of the inlet or spigot end, flaring the bell, cleaning, and fluxing with tallow only those areas to become apart of the joint. Plumber's soil or paper should be applied beyond those points. The pipes are then fitted together and spot soldered. With a sharp-pointed iron, solder is flowed around until the joint is filled about halfway. A blunted iron is used to fill the rest of the cup with solder. With the possible exception of alloys containing more than 2% antimony, lead alloys can be soldered in the same manner as described for lead. These alloys have a solidus temperature under 315"C, and so the soldering temperature factor is critical. Extreme care is necessary in soldering to avoid melting the base metal. Being heavier, ornamentalcastings alloyed with more than 2% antimony are more easily soldered.

F. Soldering Lead to Other Metals All metals that can be precoated with lead can be joined to lead pipe or sheet by wiping or heating with a torch or soldering iron. The precoating should be confined to those areas of the other metal that are to become an integral part of the joint. The joint should be prepared just as described for joining lead to lead.

G. Welding of Terneplate Terneplate, or terne, is sheet steel coated with a lead-tin alloy (3-15% Sn), formerly used in large quantities for roofing [349]. It has been replaced in this market to a large extent by either Type I1 aluminized or zinc-coated steel sheets, notably Galvalume@, a registered trademark of BEIC International, Inc. Coatings of standard terneplate, as specified by ASTM A308, are listed in Table 12 13491. Much of terneplate production today is consumed in the manufacture of gasoline tanks for vehicles. These tanks are made either from two drawn halves, which are subsequently seam welded together, or from rolled cylinders that are lock-seamed and soldered. Many other vehicle components, such as tubing, are terned; however, these are generally coated after welding. Another area of use for terne in which joining is important is the manufacture of burial caskets, where the exposed side is polished to a high luster. Seam welding or soldering of lock-seam joints are common joining processes in this application.

402

Chapter 3

Table 12 StandardTemplateCoatings 1611. (Courtesy of Lead Industries Association, New York.) ASTM A308 Coating Designation LT0 1 LT25 LT35 LT40 LT5S LT85 LT1 10

1.

Minimum coating ( g/m ’ No minimum (commercial) 76 107 I22 168

259 336

Resistance Seam Welding

Resistance seam welding is commonly used t o join formed sheets of terne to make leak-tight containers for fluids or gases [349]. Steels typically used have thicknesses of 0.025-0.062 in. (0.6-1.6 mm) and coating weights on one or both sides of 0.16-0.42 oz/ft’ (50- 127 g/m’). Steels thicker than 0.125 in. (3.2 mm) are difficult to weldwith this process. Coated steel surfaces to be joined should be cleaned to remove residues of dirt or oil. The joint is prepared by simply pressing together the surfaces to be joined to make a lap or flange joint. Seam welders use two rotating copper wheels that are spaced with a gap to allow the prepared joint to enter between the wheels under a predetermined force ranging from S00 to 1000 Ib (2.2-4.4 kN) depending on steel thickness. Alternatively, a single rotating wheel and a stationary mandrel can be used. Sufficient alternating current, typically 17,000-22,000 A, also depending on the steel thickness, is applied to fuse the two sheets making up the joint. In a typical welding schedule, current is applied for three cycles at 60 Hz (an interval of 50 ms). Then, it is shut off for two cycles at 60 Hz (an interval of 33 ms) before being applied again for three cycles. The copper wheels can build up significant heat; thus, the introduction of cooling water to the wheels is required, usually by flood cooling. Metal oxides which transfer from the joint and accumulate on the wheel surfaces are removed from the wheel circumference by continuous cleaning. Typical electrodeface widths are 0.20-0.31 in. (5-8 mm), and they produce seam welds of approximately the same width dimension. Welding speeds of 60-100 in./min (25-42mm/s) are typical. Representative conditions for seam welding terneplate are shown in Table 13 [349].

Table 13 'Qpical Conditions for Seam-Welding Terneplate [349]. (Courtesy of Dr. F. E. Goodwin, ILZRO.) Material thicknesses' (mm)

0.6-0.6 0.8-0.8 0.8-0.8 0.9-0.9 0.95-0.95 0.95-1.6 1.0-1.0 1.2- 1.2 1.2-1.2

Electrode shapeb"

W(m) 9.5 10.0 12.7 12.7 12.7 12.7 12.7 12.7 12.7 12.7 10.0 10.0 12.7 12.7

E(mm) 6.4 5.5 7.1 7.1 7.1 7.1 7.1 7.1 7.1 7.1 5.5 5.5 7.1 7.1

Weld time, cycles (60 Hz) net force

0 2.9 2.8 4.0 4.0 4.4 4.4 2.2 3.3 2.5 3.0 3.1 3.1 4.9 4.9

current (A) 20,000 18,500 17,000 18,000 17,500 18,500 17,100 21,000 19,000 19,000 20,000 2 1,500 18,000 19,000

Heat

1 3 3 5 2 5 3 3 3 3 3 3 2 4

Cool 3 2 2 2 1 1 3 3 3 3 2 2 2 1

w

Welding speed

Min. contacting overlap, I"

(ds)

(mm)

27.9 41.7 25.4 42.3 25.4 42.3 17.8

30.5 38.6 32.0 41.7 41.7 25.4 42.3

11.1 11.1 11.1 11.1 12.7 12.7 12.7 12.7 12.7 12.7 12.7 14.3 14.3 14.3

<

8 fD v)

I", =I

m

0, r fD P)

0.

7 0

n

C

2 v)

lndividual thicknesses for bath joint members are given (i.e., T,welded to T3. bDimensional variables are as shown in b) :

(a) Electrode Width and Shape

(b) Minimum Contacting Overlap

'Electrode Material RWMA Group A, Class 2. Nominal electrode diameter ranges between 203 to 254 mm.

g w

404

2.

Chapter 3

ResistanceSpotWelding

Terneplate can be readily spot welded on standard equipment used for coldrolled orgalvanizedsteel. Steel and coatingcharacteristics are similar to those described i n the previous seam-weldingsection.Goodresults are achieved using RWMA Class I1 electrodes or standard Cu-Cr-Zr truncated electrodes with a face diameter of 0.25 in. (6.35 mm). Current, time, and electrode-force conditions for welding terneplate are 15-30% higher than for welding bare steel. Thus, depending on the thickness of the sheet, an electrode force of 900-1500lb (4.0-6.7 kN) would beused with weld currents of 12,000-22,000 A. Current is applied for 6-16cycles, again depending on the steel thickness. Some experimentation is always required to obtain the desired weld nugget size. Welding rates of one weld per second can be obtained. Electrode tip lives exceeding2000 welds are possible. Representative conditions for spot welding terneplate are shown in Table 14 [349]. To establish the suitability of a particular terneplate product (e.g., sheet) for resistance spot welding, evaluation should be done by using the test methods recommended practices of ANSI/AWS/SAE D8.9-97.

3. Arc and Oxyfuel Welding Terneplate can be welded without filler metal. However, the thin sections involved require careful control of heat input. For this reason, oxyfuel and other gas-welding processes are not recommended. Lap joints of terneplate can be welded successfully without filler metal by using the gas-tungsten arc welding (GTAW) process and maintaining asshortanarc length as possible. The lead-tin coating in the joint will not disturb the flow of the base weld metal, allowing a defect-free joint to be produced. For highest joint strengths, the lead-tin coating should be removed from the surfaces by grinding during preparation of the joint.

4.

Soldering

The terneplate coating assists in the soldering process by encouraging wetting of the filler metal. No preparation of the surface is needed other than removal of dirt, oil, and grease. If the surface has been discolored by weathering, light brushing will be necessary to improve wetting. Gas or electric soldering irons, along with other common heating methods, may be used to heat the joint area, which typically consists of a lapped or interlocking joint. Joint clearances of 0.001 to 0.005 in. (0.025 to0.150 mm) are suitable. Rosin fluxes are satisfactory in most instances. Corrosive fluxes may be used when complete removal of flux residues is possible.

(D

In

Table 14 Resistance Spot-Welding Carbon-Steel Temeplate [349].(Courtesy of Dr.F. E. Goodwin, LZRO.)

2. 3

Material thicknesses"

(mm)

0.7 0.9 1.3 1.6

Electrode diameter and shapeb"

D (mm)

d(mm)

15.9 15.9 15.9 19.0

4.4 6.4 6.4 6.4

at

(deg) 120

120 120 120

Electrode net force (kN)

Approx. current (A)

Weld time, cycles (6OHz)

2.0 2.2 2.9 3.1

11,000 12,000 15,000 17,500

12 13 15 18

Weld nugget sizeb (mm)

4.8 5.6 6.1 6.9

(c1

Min. tensionshear strength

Weld spacing

(W

(mm>

4.0

15.9 19.0 22.2 31.8

4.4 6.7 8.5

0,

Mm. contacting overlap, Lb (mm)

12.7 14.3

r

8 P

7 in. 8 C

17.5

19.0

?tvo equal thicknesses of each gauge. Commercial coating weights up to 137 dm'. Material must be free from dirt. grease, paint, and so forth. Qimensional variables are as shown in sketches (a), (b) and (c):

(a) Electrode Diameter and Shape

(b)Weld Nugget Diameter

(c) MinimumContactingOverlap

Blectrode Material Croup A, Class 2. Water cooling with 7.5 L/min. P 0 tJl

406

Chapter 3

5. Automotive Fuel Tank Production The corrosion protection trend among domestic North American automakers is toward widespread application of two-side coated steel [349]. The current and near-future corrosion protection specifications of coated sheet products emphasize manufacturability (i.e., forming,joining, and painting criteria). The coated-sheet products used by the domestic North American manufacturers include both hot-dip and electroplated pure zinc and zinc-iron coatings to 100 g/m*/side) and terneplate. The current and future higher usage of coated steel and the heavier coatings being specified by North American manufacturers are reflections of the philosophy that use of such materials is both a technical improvement and a cost-effective way of providing durability in a highly corrosive environment. The use of terneplate (usually long terne) for automotive fuel tanks is standard practice, as it is corrosion resistant and can be soldered or welded readily using the resistance seam-welding process (RSEW) to produce an economical, leakproof unit. A recently developed material variant is the top coating of a long terne sheet with organic coatings. Azinc-rich organic coating is used for additional protection on the outside of the fuel tank, and an aluminum-rich organic coating is used for additional protection on the inside of the fuel tank. The aluminum augments the long terne’s resistance to the newer auto fuels [e.g., those containing low concentrations (about 10%) of methanol, ethanol, or both]. Through the years, refinement in welding terneplated steel for use in automotive fuel tanks has resulted in welding speeds of 300 in./min (127 mm/s) for 20-22-gauge (0.93-0.78 mm) material. Welding normally is accomplished with seam welders either facing each other or in tandem. Welding is performed in a straight line across one side or end of the fuel tank, with automatic equipment handling the tanks. Welding at the indicated travel speed requires heavy-duty equipment, using a one-cycle-on/one-cycle-off timing schedule (or similar) for AC machines, or a continuous schedule for DC machines to obtain consistently sound welds. Tack welding is required and care must be exercised when crossing prior welds at the corners in order to prevent leaks or blowholes. To give consistent production quality, careful attention must be paid to the knurl drive wheel design.The knurl drive wheel can control the buildup of tin and lead on the wheel electrodes by breaking up the buildup. Also, the knurl drive wheels may function to control the shape of the contact face of the wheel electrodes. This can be accomplished by using knurlers designed with a radius in the wheel contact area or by using a flat knurler design equipped with side cutters that constantly trim the wheel contact face

Processing Products of Lead

407

to a specific width. Both electrodes should be knurl driven, ideally, to deliver a more positive drive, lessen the possibility of skidding, and provide constant maintenance of both electrode contact faces.

H. Mechanical Fastening of Supported Lead In supported lead, the lead sheets are reinforced by mechanically fastening to the supportive steel, wood, or concrete structure. The major types of such equipment are loose-lined and cage-supported vessels, flues, ducts, launders, towers, reactors, floors, floor linings, expanded lead-lined pipe, cable sheathing. rooting, and anodes [611. 1.

Loose-Lined Equipment

Loose-lined construction involves hanging or fastening lead sheet linings to the walls and bottoms of steel, wood, or concrete vessels. This is one of the least expensive and most easily repaired types of vessel. Its use is limited to moderate-temperature ranges and when abrasive conditions, vacuum service, or very large tanks are not involved. Theoutersupporting shell of loose-lined vessels such as tanks, stills, and evaporators may be steel, wood, or concrete. Digestors, evaporators, mixing tanks, and stills are usually made with steel. Woodis generally used only for moderate-sized storage tanks, plating tanks, or vats. Concrete tank shells are often used in making electrolytic cells. A bituminous or asphaltic coating is applied cold to the concrete shell before lining it with lead to prevent incompletely curedor “green” concrete from corroding the lead. Chemical lead is usually chosen for loose-lining small tanks under mild conditionssuchas negligible abrasion,agitation, and flow.Useof 6-8% antimonial lead is recommended when abrasion from mechanical abuse, agitation, or flow is involved, when the tank is very large, or when the operating temperatures exceed 65°C. The thickness of the lead lining may be 8-, 12-, or 16-lb-lead, depending on the expected corrosion rate, mechanical loads, and thermal cycling. The joints or seams should be located where they will be subjected to the minimum stress during operation. Loose lead linings are fastened to the outer shell using lead-covered bolts, lead buttons, and lead-covered steel strapping, or by spot bonding. If the lining exceeds 3.3 m (10 ft) in height, lead-covered, half-oval steel straps should be used. Metallurgically bonding small areas of loose linings (spot bonding) helps support them and distributes the weight load more evenly. Figures 70 and 71 illustrate the different methods of fastening lead sheet to the walls of steel vessels [61]. Figure 72 shows the fastening of lead sheet to wood orconcrete walls [344]. Figure 73 shows the different types of joints used in a lead-lined steel vessel [61].

408

Chapter 3 Burned

Figure 70 Fastening of steel straps in loose-lined vessels 1611. (Courtesy of Lead Industries Association, New York.)

2.

Cage Supported Equipment

Cage or basket construction is a framework of steel pipes, fiats, and angles welded together to support a vessel formed by welding lead sheet together. This type of vessel can be prefabricated and assembled in the field. The main features of cage construction are low cost, rapid heat dissipation, early

Carria e bolt

Stove bolt

Lead strap

Roundhead bolt

Figure 71 Bolt support of loose-leadlinings 1611. (Courtesy of LeadIndustries Association, New York.)

Processingof Lead Products

409

a. Simple, visible fixlng ROWd-heeded

m e w and washer. May be coated with high lead-content

c Lead button or dome

Stamlesss t e e l screw

d. Soldered dot

ReamedWbrass m e w and washer Wiped, soldered or

leadburned dot finished flush

Figure 72 Some of the methods for fastening lead sheet on wood and concrete walls [344a]. (Courtesy of Lead Development Association, UK.)

Chapter 3

410 D d l of l a p . u m

D a i l of top

b.1.d of band iron oupport of load lining

Detail of lapping and burningat bottom of flat tank

Altmato mothad uoing a wood fillw

Shell lmng

Tank bottom1 lining

Lapping and burningat con.

Figure 73 Loose-lined leadtank [61]. (Courtesy of Lead Industries Association, New York.)

leak detection,andeasy repais. Figure 74 showsanexample of this cage (or basket) type of construction [611. Many hazardous fluids may be safely contained in this type vessel, because it has a high percentage of visually exposed surface area which speeds up the detection and repair of leaks.

41 1

Processing of Lead Products

abd le of tank

Figure74 Cage-constructed lead vessel [61]. (Courtesy of Lead Industries Association, New York.)

412

3.

Chapter 3

Floors and Floor Linings

Lead sheet has been used as a corrosion-resistant membrane under the floors of metal-plating and acid plants. In other cases, such as in nitroglycerine plants, the lead sheet is made the top layer of the floor. This takes advantage of the fact that lead is nonsparking and is easier to clean than wood. As lead is resistant to corrosion by most natural waters, it is also used as a waterproof membrane under reflecting pools, shower pans, and planters and as flashing on buildings.

4.

Expanded Lead-Lined Pipe

Expanded lead-lined pipe is often used when operating pressures are too high to be safely handled by lead or hard lead pipe. This supported lead pipe is made by inserting lead pipe into steel pipe and expanding the lead pipe tightly against the inside steel wall. Thesize of lead pipe to use in making expanded pipe is the one which will have the minimum clearance between it and the steel pipe. Expanded lead-lined pipe is available in a wide range of diameters in standard lengths of 20 ft (6.6 m) with lead linings of from 1/8 in. to 3/8 in. (3.2-9.5 mm) in thickness. Typical sizes and weights are shown in Table 15 [61].

1.

Bonded Lead

Bonded lead is metallurgically joined laminates of lead and another metal, usually steel (Figure 75) [61]. This type of composite material has the corrosion resistance of lead combined with the stronger mechanical properties of steel. It will resist delamination so strongly that only by melting the lead or the solder bonding layer or chipping it off with a pneumatic hammer can it be separated from the steel. These excellent performance characteristics allow bonded-lead-type equipment to meet such demanding operating conditions as rapidly fluctuating temperatures, vibration, and changes in pressure from positive levels to vacuums. In addition,as lateral movement of the lining is severely restricted, the only response to thermal cycling is an occasional increase in lining thickness. The thermal and electrical conductivities of bonded-lead vessel walls are high, due to the gapless nature of the metallurgical bond. The cost of bonded-lead vessels is higher than supported-lead vessels with strapped-on linings because of the cost of the metallurgical bonding process. Other metals have been joined metallurgically with lead to make bonded-lead equipment, such as lead-clad copper steam coils. The essential difference between bonded lead and the metallurgically bonded lead coatings is that the former has a much thicker layer of lead,

Table 15 Expanded and Homogeneously Bonded Lead-Lined Pipe 161I. (Courtesy of Lead Industries Association, New York.) I.D.

L. Th. mm

in.

mm

12.5 19 25.4

1/2 314

31.8

1-114

38. I

1-112

50.8

2

63.5

2- I12

76.2

3

101.6

4

127

5

152.4

6

in.

3.18 3.18 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25 3.18 4.76 6.25

1

L. wt.

I.D. mm

kE

in. ~~

203

8

254

10

254

10

305

12

~

Wt.

kg/m

Ib/ft

2.98 3.43 3.72 5.5 1 7.00 6.85 8.04 9.23 8.19 9.68 11.17 10.43 12.8I 14.90 14.90 17.87 20.85 19.81 22.94 26.36 27.70 32.02 36.94 37.39 42.0 48.4 I 45.88 52.88 60.62

2.0 2.3 2.5 3.7 4.7 4.6 5.4 6.2 5.5 6.5 7.5 7.0 8.6 10.0 10.0 12.0 14.0 13.3 15.4 17.7 18.6 21.5 24.8 25.1 28.2 32.5 30.8 35.5 40.7

L. Th. lb

mm

~

Wt.

in.

kg/m

Iblft

70 80 75.8 85.8 88.2 100.4 92.8 104.9 102.2 1 14.2 114.1 132.1 122.6 140.6

47.0 53.7 50.9 57.6 59.2 67.4 62.3 70.4 68.6 76.7 76.6 88.7 82.3 94.4

~

11.4 11.4 13.2 13.2 14.5 14.5 15.9 15.9 18.6 18.6 20.4 20.4 23.2 23.2

25 25 29 29 32 32 35 35 41 41 45 45 51 51

4.76 6.25 4.76 6.25 4.76 6.25 4.76 6.25 4.76 6.25 4.76 6.25 4.76 6.25

3/16 I 14 3/16 114 3/16 114 3/16 1/4 3/16 1 14 3/16 114 3/16 I 14

Nore: I.D. = inside diameter: L. Th. = lining thickness: L. Wt. = weight classilicntion of lining: Wt. = Weight in kg/m2 and Ib/l't (approx).

414

Chapter 3 Bonded Lead

X:Lead or lead alloy Y:Steel, wood or concrete Z:Metallurgical bond

Figure 75 York.)

Bondedlead

[61]. (Courtesy of Lead IndustriesAssociation,

New

which allows it to provide long service life even in severely corrosive chemical environments. The three steps necessary to make bonded-lead materials are careful surface preparation, precoating with a lead alloy, and metallurgically bonding the lead to the precoat. Surface preparation involves cleaning and degreasing the steel or other underlying metal. The lead alloys generally used as precoats contain either tin or antimony. Bonding the lead to the precoat is accomplished using pressure, temperature,or a combination of both. When all of the potentially joinable surface areas of a lead sheath is metallurgically bonded to steel, the resulting composite is said to be homogeneously bonded. If only a few small areas are joined, the process is “spot bonding.” There are three ways to homogeneously bond lead to steel: welding, casting, and cold rolling.

1.

Cold Rolling

One of the important innovations in lead corrosion resistance technology is a new, low-cost method of homogeneously bonding lead sheet to steel. Instead of using the laborious welding or casting procedures, lead-clad steel can be made by coldrolling lead sheet ontoprecoatedsteel plates. The rolling mill used in this new method is a conventional mill which has been modified. In the cold-rolling process, the steel is degreased, pickled if covered with oxides, and then fluxed with a mixture of zinc and ammonium chlorides

Processing Products of Lead

415

and hydrochloric acid. Next, a precoat is applied by hot-dipping the steel in a molten bath of a lead-tin or lead-nickel alloy. Finally, the lead sheet, degreased and wire brushed to remove the oxide film, is roll bonded to the steel. This last step is done in a rolling mill in one pass to avoid buildup of lead. If both sides of the steel are to be lined with lead, it is done in two separate passes to avoid deforming the steel. Cold-roll-bonded, lead-clad steel, as it is called by its originators, the British Non-Ferrous Metals Research Association, is available with lead linings of approximately 1/64-1/16 in. thick on 14-26-gauge steel in plates 2.5 m X l m (7.5 ft X 3.5 ft) in size. To maintain overall rigidity of the thinner cold-roll-bonded plates, the thickness of the steel should be at least equal to that of the lead lining. 2.

Welding and Casting

All the methods used to bond lead sheet to steel have four distinct steps: surface preparation, precoating, lead coating, and finishing. Surface preparation generally involves mechanical cleaning using grit blasting with shot or sand, or grinding. Chemical cleaning such as by pickling is also used. Copper is usually chemically cleaned before lead bonding. The precoat may be a SO% lead solder or 6% antimonial lead. A tin chlorideor zinc chloride flux is applied.The precoat is added either by dipping the cleaned steel (or copper) into a molten bath or by using a torch to melt and apply the precoating material. While the precoat is still hot, the molten excess should be wiped off. After solidification, flux residues should be removed with a cloth that has been dipped in hot water. The lead lining is applied either by pouring molten lead on to the base metal surface or by melting filler metal with a torch and applying it. If molten lead is used, twice the desired thickness is cast on and insoluble impurities such as dross are allowed to float to the top. After cooling, the excess lining is scraped or machined off, and the surface is smoothed over by flame-washing. To apply the lining with a torch, the precoat and then the filler material are alternately melted and then joined. The required lining thickness is built up in several passes. Usually three passes are required for each 1/4 in. (6.4 mm) of thickness. When the lining exceeds the required thickness, the excess should be machined or scraped off and flame-washed to provide a uniform and smooth lead lining.

3. Spot Bonding When lead linings are subjected to extensive thermal expansion and contraction, a buildup of stresses can occur at fixed points in the linings.

Chapter 3

416

One way to prevent this buildup of local stress concentrations is to metallurgically bond to the outer supporting shell those spots of the lead lining which are in low-stress areas. This procedure, called spot bonding, can also be profitablyusedonoccasion as a substitute for mechanical fastening.

BricWlead

J.

In certain corrosive environments, the abrasion resistance of even the hardest lead alloy is not sufficient. In many other situations, the operating temperature is above the melting point of lead. It is under these circumstances that a lead-lined piece of equipment requires either the abrasion protection or insulation of a layer of chemical-resistant masonry set with a suitable cement. This combination of an outer supporting structure of steel or concrete, a lead membrane, and an inner layer of acid-brick or tile or borosilicate glass is called brickbead (Figure 76a) [61]. The lead layer in bricuead may be chemical, acid-copper, or antimonial or other alloy. It may be bondedmetallurgically to a steel shell, mechanically fastened to a shell or framework of steel or a concrete shell, or simply hung between the brickwork and a shell. Thus bricuead is actually supported lead or bonded lead with a layer of chemically resistant Bricknead Y A

z B

X X: Lead or lead alloy Y: Steel or concrete 2:Metallurgical or mechanlcal bond A: Chemical-reustant masonry bnck B: Cushloning material (optional)

(a)

(b)

Figure 76 (a) Details of the interfaces in brick/lead and (b) a section of a brick/ lead vessel [61]. (Courtesy of Lead Industries Association, New York.)

Processing Products of Lead

41 7

masonry added to it. A section of a brick/lead vessel is shown in Figure 76b 16 1 I. The mechanical and thermal protection provided by the masonry allows lead to indirectly handle process temperatures as high as 982°C and above and abrasivesolutions.Good performance has been obtained with vacuums as low as 0.25 in. of mercury at 127°C. The use of masonry greatly increases the types of corrosive environments that can be handled by brick/ lead vessels. The supporting shell of a brick/lead vessel is similar to those used with loose linings. However, it should be designed to withstand the additional stress imposed by the thermal expansion of the masonry. If operating temperatures are 260°C or higher, the vessels should be supported in such a way to permit outside air cooling. This will reduce heat buildup on the bottom of the vessel and prevent damage to the brickwork. Brick/ lead cage vessels are sometimes used. However, for high-pressure operation, a shell must be used, and the bottom of the vessel should be dished and welded joints placed at orabove the bottom edge.The masonry used is usually 3-4% porous brick, which is resistant to the spalling caused by thermal shock, sustained high temperatures, and absorption of solutions that crystallize on cooling. The total thickness of the brickwork should be high enough to keep the temperature at the brick-lead interface at 74°C or below. The upper limit is 52°C if the lead layer is homogeneously bonded to a steel shell with a precoat containing a substantial amount of tin. The temperature gradient through the brickwork of a brick/lead vessel with a steel shell is about 3.3"C per centimeter of thickness for fire clay or shale-type brick and 2.2"C per centimeter for carbon brick. These figures are valid for process temperatures up to 204°C. The temperature gradient through the brickwork of a concrete brick/lead vessel is somewhat less. This is due to the insulating effect of the concrete shell. Another factor to be considered when setting the thickness of the brick layer in a steel brick/lead vessel is thermal expansion. The brickwork must elongate more than the steel shell expansion. This ensures that the lead lining receives continued support. Two or three layers of asbestos paper are often put between the brickwork and the lead. This is done to protect the lead from mechanical abuse when the brickwork is being laid and from the abrasive compression caused by thermal expansion of the brickwork. The use of asbestos may help create pockets of acidity. Therefore, it is not used if operating temperatures are high enough to enable leaking chemicals to significantly corrode lead. Instead, a 1/8 in. coating of either certain resin cements or a plastic coat of silicate cement is applied. Glass cloth can be used in addition to the coatings, if further abrasion resistance is necessary. Another important situation in which brickbead should be used is where a process fluid contains components which are corrosive to lead but

Chapter 3

41 8

cannot seep through chemical-resistant masonry. The lead membrane is necessary t o contain any other components able t o penetrate the masonry or eat through thc cement used t o set the masonry. An example of this type of brick/lead usage is i n vessels used to contain both polar and nonpolar organic compounds. The polar organics. many of which attack lead, cannot penetrate the brickwork. and penetratingnonpolarsareeffectivelycontained by the lead membrnnc. The cost of brick/lead is comparable to that of other material combinations that can handle the same high temperatures and mechanical abrasion. However, thc use of lead makes the overall corrosion resistance of brick/ lead equipmentsuperior to that o f equipment that use chemical-resistarlt masonry with other membranes. Applications handled by brick/lead equipment include vacuum concentrators and storage tanks handling mixtures of sulfuric acid and organic chemicals. such as petroleum distillates and vessels used to alternately bandle acids and alkalis. Autoclaves and the high-temperature portions of the ducts, scrubbers, acid-mist precipitators, and towers used t o handle acid and sulfur dioxide-laden gases are olten of brick/lead construction.

K.

Machining of Lead

The machining process used in thc case of lead alloys principally involve diecuttingor water jetcuttingforhigh-performance ancl high-precision parts. Draw Knives, hand or electric saws, or hand shears also could be used i n parts for less demanding applications.

1.

Die Cuting and Stamping

Die cutting and stamping arc two processes valuable for creating intricate parts from pure chemical lead and antimonial and calcium lead [WO].Each process has proven advantageous in specific applications. Dic cutting i n volves low to moderate tooling cost, meets moderate tolerance requirements. is excellent for low to medium volumes, and involves short tooling delivery time. The typical maximum size that can be die cut is 0.6 m X 1.8 m (24 i n X 72 in.). Tolerances achievable in die cutting are t 0 . 0 1 0 to 2 0.020 in. Stamping involves moderate to high tooling cost, meets high tolerance requirements, is excellent for medium to high volumes. and involves modcrate tooling delivery time of about a month. Stamping can be done using inserts in a master die LIP to a 2.5 i n . cross section or by using dedicated die sets. Typical tolerances achievable i n stamping is t 0.005 i n . and tighter tolcrances are also possible.

Processing Products of Lead

419

Figure 77 Die cut and stamped shapes made from lead and lead alloys [300]. (Courtesy of Vulcan Lead, Milwaukee, W.)

There are many options in die cutting and stamping. Lead parts can be provided with paper backing, adhesive backing, or no backing in thicknesses from 0.001 to 0.375 in., making this ideal for x-ray or nuclear use. Adhesive backing is available for applications such as computer disk pack balance weights or for x-ray and nuclear use. When stamping, interchangeable inserts can be used in a master die to minimize tooling costs.Die cutting, in turn, is perfect for prototyping because the tooling is inexpensive and can be changed rapidly with ease. Vulcan lead uses die cutting and stamping to produce lead parts for a extensive variety of applications. The applications include (1) gasketsin chemical industries, (2) shielding, both for x-ray and nuclear situations, (3) balance weights, with or without adhesive backing, (4) sealing washers, (5) vibration and sound-dampening components and (6) acid-resistant applications. Figure 77 shows a number of die-cut and stamped shapes made from lead and lead alloys [300].

2. Water-Jet Cutting Abrasive water-jet cutting technology is now a widely used by Vulcan Lead and other lead metal fabricators to cut lead sheets and foils with high precision [300]. In the Vulcan’s abrasive water-jet cutting, an intensifier pump pressurizes water to 370 MPa (55,000psi) and forces it through a nozzle as small as 0.1 mm (0.004 in.)indiameter. This generates a high-velocity, coherent stream of water traveling at speeds up to 912 m/s (3000 ft/s). This stream of water will cut lead and other soft materials like rubber, foam, and plastic. For hard materials like stainless steel, titanium, or aluminum, an

420

Chapter 3

optional abrasive (typically 80-120-grit garnet) is entrained into the water stream. Part of the water's momentum is transferred to the abrasive particles which do most of the cutting. Controlled by CNC equipment, the cutting head precisely cuts almost any material into any shape. Figure 78 shows the water-jet-cutting unit used in the fabrication of lead parts [300]. Figure 79 shows water-jet-cut lead parts [300]. Reduced material waste, decreased cutting costs, exceptionally precise shaping and customized, programmable cutting capabilities makes this very attractive in cutting lead and lead alloys. Contour cutting of intricate artistic shapes and cutting delicate material such as lead makes it attractive in cutting lead parts or sheets. The abrasive jet eliminates heat damage and frayed

Figure 78 Vulcan Lead waterjet cutting unit used in the fabrication of lead parts [300].(Courtesy of Vulcan Lead, Milwaukee, W.)

Processing Products of Lead

421

Figure 79 Water-jet-cutleadparts [300]. (Courtesy of Vulcan Lead, Milwaukee, WI.)

edges, creating a smooth finish. The abrasive jet’s precision cutting allows elaborate contouring to create a special product. The abrasive water jet’s flexibility allows both prototypes and multiple pieces to be cut. The abrasive water jet eliminates the expense of diamond wheels and diamond-tipped cutting tools.

L.

Lead Coatings

Instead of lead lining the equipment with lead sheet thicknesses of 1/16 in. or more, a thin coating of lead can be applied to equipment surfaces to provide corrosion protection in an economical manner. The amount of lead alloy per unit area of coating is of the order of g/m2 (oz/ft2) instead of the kg/m2 (lb/ft2)used for sheet lead. The three major methods of applying lead and lead alloy coatings are spraying, hot dipping, and electrodeposition. The corrosion resistance and mechanical performance of equipment protected with lead coatings depend on the strength of the interfacial bond between the coating and substrate bondandtheamountof microscopic porosity. Coatings that are metallurgically well bonded to their substrates will maintain their integrity even when forced to undergo bending, forming, drawing, or other changes of shape. Microscopic pores are introduced in the coating during the deposition of coating. This could lead to a direct contact between the corrosive medium and the substrate metal through these pores. Controlling the coating process to minimize or eliminate this porosity is important. An increase in coating thickness to a value much larger than the pore sizes could also minimize the potential for such direct contact. Microscopic pores in lead or lead alloy coatings are sealed by peening, painting, or an organic sealant. Overall corrosion resistance can be increased by choosing as a substrate a metal which

Chapter 3

422

is either cathodic (e.g., stainless steel) to the lead coating or which f o r m a tight corrosion product (e.g.. copper-bearing steel).

l.

Sprayed Coatings

Thermalspraying of lead coating is an economical wayof applying lead coatings. However. the containment of tine particulates that are generated during thermal spray is of concern because of the toxicity associated with lead. Thermal spray deposition process involves melting of the lead wire or powder feed to the spray gun, the formation of tine droplets by an impinging gas jet, and acceleration and spraying of the tine droplets onto the substrate by the gasstream.Thedroplet may be either i n complete liquid form or semisolid form as it impacts the substrate ancl flows into a lamellar form and solidities completely. The metal-spraying gun or device requires either a fuel gas-air mixture or an electrical arc source to melt the lead i n wire orpowderform.When the combustiblemixture is used 21s a heat source. the process will be referred to a s a flame spray process (Figure 80) [3501. When an electric arc is used as heat source with the wire feed acting as ;I consumableelectrode, the process is rcfcrretl to as an electric arc spray process (Figure X I ) 13501. The plasma spray process is similar to the spray process but uses a non-consumable tungsten electrode, with the feed material melted by the electrically induced plasma (Figure 82) (3501. The lead metal to be sprayed. usually i n the form of a 2-mm-diametcr wire, is fed through a driving mechanism into the llarne (or arc). The compressedair jet atomizes the metal melted in the Harne or arc and hurls it onto the surface, which has previously been cleaned and toughened by sandblasting. The velocity of the particles in the .jet, depending on the operating condi-

Sprayed materla1

Air cap

Ceramlc or wire

/ Burnmg G ,ases

6 Spray stream

Air channel

Figure80 Flame spray deposition o f International. Materials Park. Ohio.)

Prepared substrate

;I

Icad nlloy coatmg [ 3 5 0 ] (Co~~rtcsy . of ASM

423

Processingof Lead Products Substrare

Reflector

Figure 81 Arcspray deposition of a lead alloy coating [3501.(Courtesy of ASM International, Materials Park, Ohio.)

tions, is between 150 and 500 m/s. On impingement, the metal particles, some of which are already solidified to a pasty consistency are pressed flat and matted together. The entrapment of atomizing gas molecules in the liquid is possible and that leads to the formation of microscopic porosity in the coating. Prior to deposition of lead coating, the substratesurface is cleaned and roughened by abrasion. Roughening helps to increase the mechanical bonding of the coating to the substrate. The relatively low strength

Cu Anode

Powder

Coatlng

Figure 82 Flame spray deposition with a powder feed [350].(Courtesy of ASM International. Materials Park, Ohio)

424

Chapter 3

of the mechanical bond limits the use of this type of coating in applications involving any bending or forming that can cause delamination. The low melting point of lead and the ease of the spray process make this process flexible and economical enough to be used in both construction and on-site repair work. Relatively thin coatings (several micrometers) to thick coatings (several millimeters) can be applied by this process. In general, lead coatings should be sprayed on whenever the low cost and flexibility of this method outweigh the thinness, porosity, and low resistance to flexure failure of the resultant coating.This is the caseeven in severely corrosive chemical environments. The application of sprayed lead coatings for protection against corrosion include (1) copper evaporating coils with 1.5-mm-thick lead coating, destined for hot aluminum sulfate, (2) precipitating baths of rayon spinning machines (0.3-l-mm lead coating), and (3) electrofilters in sulfuric acid plants with a 0.3-l-mm-thick lead coating.

2. Hot-Dipped Coatings Hot dipping is another approach to applying a lead coating to a component. Here, the part is dipped in a molten lead alloy bath and taken out; the liquid metal layer attached to the part is allowed to solidify. The surfaces to be coated are chemically cleaned, pickled, and fluxed before dipping. Unalloyed lead will not metallurgically bond to steel, copper, or other metals. Therefore, the coating material is usually a tin or antimony alloy of lead. In addition to tin and antimony, other alloying elements in lead alloys that help the bonding of the lead to steel are silver, nickel, mercury, or cadmium. Porosity formation from trapped gas molecules is less likely in this process and the lead coatings applied by hot dipping contain fewer microscopic pores than sprayed-on coatings. The coatings are also metallurgically bound to the substrate metal. Theequipment coated by hot dipping can, therefore, be used in applications involving bending and drawing without the risk of delamination. The most important hot-dipped coating alloys used in applications requiring high corrosion resistance are (1) lead-tin alloys, including lead alloys containing less than 5 % tin to which small amounts of antimony, silver, and/or zinc are often added to improve fluidity and (2) terne alloys, which can have from 5% to 50% tin in them, but usually contain less than 20% tin. Antimony is sometimes added to both types of alloys to improve abrasion resistance. Astin and antimony are both more costly than lead,the higher their concentration, the more expensive the coating will be. However, for low-tin alloys, increasing the tin content will produce a more abrasionresistant coating. Therefore, 12-20% tin is the concentration used whenever

Processing Products of Lead

425

the equipment to be coated will be subject to mechanical abuse. Antimony is also added to increase the hardness of a coating. The alloys with less than 5% tin are generally used to coat small parts. The parts are centrifuged after hot dipping to remove excess metal, leaving a coating usually 5 pm thick. Some larger parts are hot dipped in this type of alloy but are not centrifuged. The coating thickness on these parts will depend on the temperature of the alloy bath and the mass of the unit being coated. However, the maximum thickness is generally kept below 15 pm. Terne alloys are used to coat steel and form what are called short terne and long terne. Short terne is primarily used as a roofing material and to make cans which hold paints and lacquers. The short terne used in roofing contains 20% tin. This roofing material has been called by many other names, including valley tin, roofer’s tin, terne-coated steel, terneplate, and, at times, just terne. The metals most frequently coated with terne are mild, rim, special killed, and copper-bearing steels, copper, and, recently, passivated stainless steel. Copper-bearing steel coated with terne has especially high resistance to corrosion, as the steel surface exposed at pores forms a tight corrosion product which prevents further attack. Terne-coated stainless steel is the material with the hot-dipped fonn of lead coating which has the highest resistance to corrosion. This is because passivated stainless steel is cathodic to the lead coating which means that even at pores, the corrosive attack will be entirely focused on the lead coating. Roofing terne is often specified in units of pounds per double base box. The surface area of a single base box is equal to one side of 1 12 plates of 14 in. X 20 in. size or 31,360 in.’ (20.23 m’). A double base box has I 12 plates of 20 in. X 28 in. or a total one-side surface area of 62,720 in.’ (40.46 m’). Therefore, an 8-lb double base box of roofing terne has a 3.81 pm-thick coating on each side of such a surface. Roofing terne is generally available in 26-, 28-, and 30-gauge sheets in 100 ft lengths wound on coils having widths of 12, 14, and 40 in. Other sizes are available as required. including plates with base box dimensions (20 in. X 28 in. and 14 in. X 20 in.). Long terne is available in long lengths on coils o r in cut form with a maximum length of 144 in. Widths are available in sizes up to 54 in. and total thicknesses range from 0.01 13 to 0.0635 in. (0.287 to I .613 mm). These thicknesses carry coatings of a total weight on both sides of 0.25, 0.35, 0.45, and 0.55 oz/ft’ (76, 107, 122, and 168 g/m’) and higher. Tests to check weight and composition of long terne are in ASTM Specification B309. Other specifications include ASTM B308 and Federal Specification QQ-T19 I . Long terne is used in automobile brake lines, radiators, air and gas filters, and gasoline tanks, and in television and radio chassis, air cleaning and conditioning equipment, metal furniture parts, and as a roofing material.

Chapter 3

426

Lead coatings with I2-20% t i n have been used to provide protection against atmosphericattack. The use o f terne as a roofing material is also due to the fact that it is very receptive to forming and painting.The last feature is especially important when high light reHectance is desired. Terne coatings. pcriodicnlly repainted. have lasted S O or more years. A coating thickness on eachside of 9.65 p m (20-lbdouble base box) is often used with terne-coated copper-bearing steel to provide protection against atmospheric attack. This protection is normally adequate if thc terne is painted periodically. ASTM Specitication B 1 0 1 contains recommendations on how thick lead coatings on copper (hot dipped or electrodeposited) should be to meet different environmental conditions.

3.

Electrodeposited Coatings

Lead can be deposited at high rates onto steel or copper by electroplating. Anodes of the same composition a s the desired coating are used to replace the material being continuously plated out of the solution. Two plating solutions commonly used to electrodeposit lead alloys arc lead fluosilicate and lead sulfamute. A third solution, lead Huoborate, can be used to electrodeposit both lead alloys and pure lead.Thestructure and density of the coatings are controlled by small amounts of additives in a l l three electroplating baths. The use of Huosilicate bath is preferred because of its lowest cost in large-scale production. However, this type of bath has limited stability. The chemicals used in sulfamate baths are initially i n a noncorrosive solid form, making handing procedures easier. In both solutions, a Hash coating must be applied prior to the electrodeposition of lead coating. The electroplating with fluoborate solution is the most expensive, but a tluoboratc bath is the most stable and gives the finest grain size i n the deposit. In addition, this

Table 16 Recommended Thicknesses lor Lead Coatings (Courtesy ot' Lead Industries Association. New York.)

on Copper [ h 1 1.

Weight of lead coating

(kg/m')

Class 1: Light

Class 2: Standard (for general Class 3: Heavy

use)

Minimum

Maximum

O.SX6

0.733

0.977

1.466

1.95s

2.443

Processing of Lead Products

427

solution has been used i n high-speedstrip-platingoperations with current densities of from 200 to 1000 A/ft.' (2153 to 10.764 A/m'). The fine-grained coatings produced provide good surface coverage. Pure lead coatings which are resistant to peeling. chipping, or delaminationcan be deposited from fluoborate solutions onto steel or copper without having to first put down a flash coat. One important advantage of electrodepositingcoatings, instead of spraying them on or using the hot-dipmethod. is being able to produce coatings free of microscopic porosities. Lead coatings without pores provide the best possiblecorrosionprotection for underlyingmetals. Another important advantage of electrodeposition is that pure lead coatings can be metallurgically bonded to other metals without requiring a precoat. The thickness of electrodeposited lead coatings on ferrous met'd I: \ required to provide adequate corrosion protection for different environments are discussed in ASTM Specification B200. These thicknesses range from below 12.7 p m where a paint aftercoat is used and the environment is mild to more than 38.1 pm when there is exposure to corrosive chemicals such a s sulfuric acid. When a highly corrosive environment is involved or therc is a good possibility of mechanical damage, coatings are made as thick as 127-254 pm. The second appendix of ASTM Specification B200 contains electrodepositionprocedures which helpproducecoatings of acceptable quality. Copper flash coats are deposited from cyanide and alkaline solutions. These range i n thickness from a minimum of 0.38 p m to a maximum of 2.54 pm. Many copper products are protected by lead coatings applied by both electrodeposition and hot dipping. ASTM Specification B 10 I lists desirablecoatingthicknessesfor this type of coating in differentsituations. However, for optimum corrosion protection, the Lead Industries Association, Inc. recommends the coating weights shown in Table 16 [61].

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Applications of Lead

The attractive properties of lead andits alloys, as described in detail in Chapter 2 and the ease with which it can be processed as illustrated in Chapter 3, makes them invaluable in a wide range of modern applications. Contrary to the image in the general public that lead is a poisonous material that a society may be better off without, it is an invaluable material that one cannot do without in many areas of modern life. One cannot imagine a transportation industry today without lead acid batteries, a nuclear industry without lead shielding, electronic circuit boards without lead-based solders, or medical and industrial x-ray equipment without lead alloy collimators and shields. Like many other metals that are vital to high-technology industry, lead certainly poses environmental hazards, and this awareness has led to the minimization of the pathways of lead to humans and other biological species. Thishas led to the elimination of applications in which leadis dispersed in such a way that its recovery and recycling is difficult or human contact cannot be avoided. Such applications include use in paint, gasoline, water pipeline joints, and bearings. Whereas lead in gasoline is being eliminated, the gasoline tank itself is made of a terne-coated steel sheet,as illustrated i n Chapter 3. Newer and modem applications of lead are continuously emerging and all these applications involve the use of lead in such a form that lead is almost completely recovered and recycled. In this chapter, we provide a brief discussion of a wide range of applications in which lead alloys are used. For more detailed treatments, readers are referred to sources listed in the References and the publications of various lead industry associations worldwide. Some of these applications such as its use as an acoustic barrier, handling of corrosive chemicals, nuclear radiation protection, and acoustic damping have been described tosome extent in Chapter 2. By 429

Chapter 4

430

design, the chapter includes mostly those applications in which lead is used in ii metallic alloy form and has avoided applications in which lead is used primarily as a chemical. This has been done mainly to limit the scope of the book. The following sections describe applications that include use of lead in energy storage batteries, earthquake dampers, intill-walls, soldcrs, packaging, nuclear waste storage, other radiation shielding (aspects not covered in Chapter 2), organ pipes, solders, inertial applications. waterproofing and architectural applications, optical glass. infrared semiconductor devices, sitperconductors. fusible alloys in heat-transfer and prototyping applications, liigli-volta,oe-cable sheathing, ~indother miscellaneous applications. Applications in which the use of lead has diminished or eliminated such a s type metals and bearings are also briefly described because of their historic iniportance. It is hopcd that the reader comes away with a bettcr appreciation for the importance of lead and its alloys to modern lifc.

1.

LEAD-ACID BATTERIES

Lend-acid batteries are the most widely used secondary battery at present time. The total capacity of electrical energy storage in lead-acid batteries far exceeds that of any other competing energy storage devices that include zi nc/air. ti ic ke I/cad in i 11m , s o d i iim/me t al ch lo ride, nic ke I tne t al hy dride , I i thiuni ion. zinc/bromine. and sodiuni/sulfur batteries. The relatively low cost a i d availability of the raw materials, room-temper~itureoperation, ease of manufacture. long cycle life. versatility, and the excellent reversibility of the electrochemical system make lead-acid batteries very attractive compared to competing systems. Although these new systems have higher specific energy atid specific power, they are unlikely to replace lead-acid batteries in its traditional markets. Lead-acid cells have extensive use both a s portable power sources for autoniobile service and traction and in stationary applications ranging from small emergency supplies to load-leveling systems. Based on the application, there are three main types of batteries. natnely SLI (starting, lighting, and ignition) batteries, industrial batteries (traction and stationary), and small sealed portable batteries. Over 300 million batteries are in use. with capacities ranging from 2 W h cells in portable applications to 100 W h in SLI battery units t o 40 MW h in load-leveling battery modules 135 1,3521.

A.

Basic Electrochemistryof Lead-Acid Battery

Gaston PlantC. a French physicist, constructed the lirst practical rechargeable cell in 1859. The intent was to tind a replacernent for primary batteries used

Applications of Lead

431

i n telegraphy [ 35 1 l. Although there have been continued improvemcnts i n battery design. the basic clectrochemistry of the lead-acid battery system has not changed since they were developed nearly 150 years ago [ 2.35 1 3541. The lead-acid cell consists o f a negativeelectrodc of porous lead (lead sponge) and ;I positive electrode of lead dioxide, Pb02, both immcrsed i n an aqueous solution o f sulfuric acid:

Pb(s)/PbSO,(s)/H,SO,(aq)/PbSO.,(s)/PbO,(s)/Pb(s)

(1)

the concentration range used in the batteries, thc sulfuric acid dissociates . The sum of the clcctrochemical reaction steps at the positive electrode is describcd ;IS 111

as H ' nnd HSO,

The sum of the reaction steps at the negative electrode is given a s

The overall electrochemical processes is represented by the equation

+ 2H,O(I) The free-energy changc o f the reaction is -372.6 kJ/mol and the standard equilibrium (Nernst) potential is I .93 1 V [ 353,3541. More often. the reaction is written as follows:

Pb(s)

+ PbO,(s) + 2H,SO,(aq)

2PbSO,(s)

+ 2H,O(I)

(5)

I.I,.,,pL.

which gives an equilibrium voltage o f I .94 1 V for cu-PbO? and I .933 V lor P-PbO,. The dependence of this equilibrium on the activities of different reactant and product species is given by

Chapter 4

432

E = 1.931

+ 0.0592 log

Theequilibrium potential varies with temperature by approximately 0.23 mV/K. In practice, the cell voltage is approximately given by the sum of the specific gravity of the acid and 0.84 V. The theoretical storage ability per unit weight assuming the reactants are at unit activity is estimated between 166 and 171 W h/kg [353,354]. However, in practice, the storage capacities achieved are no more than 40 W h/kg, as the utilization of active mass is less than 50% and the activities of the reactant product species differ from unity. As the current density increases, the cell voltage is reduced from this equilibrium voltage by the IR (current X resistance) drop in the electrolyte, activation polarization, and concentration polarization. Also, the cell voltage drops as the battery is discharged because of the decrease in sulfuric acid concentration. Apart from the reactions indicated above, other side reactions involving water decomposition occur at the positive and negative electrodes. Water decomposition occurs at much lower voltage than the equilibrium voltage of the cell, but the kinetics of the decomposition reaction are very slow and the variation of current with voltage is very small for this reaction (Fig. 1) [353].In contrast, the charging and discharging processes have a very steep

discharging the negative electrode I2/2bl

rlPb-PbS04)

charging the positive electrode ylPbS0,-Pb02)121201

+i

evolution of oxygen

c C

+ standard hydrogen4ectrode

I I

I

'discharging the positive electrode

-

-l

lPbO2-PbSO'I

l2/201

Yharging the negative electrode iPbM4

Pbl I2IZbl

Figure 1 Thevariation of current with voltage a t thepositive and negative eketrodes [ 3 5 3 ] .(Courtesy of Marcel Dekker Inc., New York.)

Applications of Lead

433

slope for the current-voltage curve. At equal current levels, the overvoltage (applied voltage - equilibriumvoltage), corresponding to the secondary reaction at both the positive and negative electrodes, is much larger than that for the primary reactions. The large overvoltages of hydrogen and oxygen evolution reactions allow the engineering application of the lead-acid battery. The presence of impurities on the electrode can result in reduction of overvoltage for the hydrogen and oxygen evolution reactions [353,355]. The storage capacity of lead-acid batteries decreases on storage in the open-circuit condition. The self-discharge occurs, as both Pb and PbO are thermodynamically unstable in sulfuric acid solutionsand react with the electrolyte. The slow evolution of both hydrogen and oxygen occurs asgiven by the following reactions that occur at localized cells set up on both positive and negative electrodes: PbO,(s) Pb(s)

+ H2S0,(aq)

2

PbSO,(s)

+PbSO,(s) H,SO,(aq)

+ HzO + 0,

+ H,

(7) (8)

The presence of impurities that lower the overpotential for hydrogen evolution at the negative electrode accelerates the self-discharge reaction at the negative electrode. Such impurities include Sb that is transferred from PbSb-alloy-based positive grids. These are discussed further in a later section. The capacity is usually recoverable on recharge, except under conditions of extended storage and low retained capacity.

B.

Basic Design of the Cell

The design of lead-acid batteries will differ depending on the intended application. The important elements of a lead-acid battery are illustrated using a traditional lead-acid battery shown in Fig. 2 [356].A brief description of the physical form, materials used, and the processing of different components are provided in the following sections. Typical current discharge curves for an automotive lead-acid battery (12 V, 40 A h) are shown in Fig. 3 [356].

1.

Positive Electrodes

In the original lead-acid cell made by Plant&, the positive electrode consisted of a thin layer of the positive active material, Pb02, formed by electrochemical oxidation of the surface of a cast sheet of pure lead. The plates in such a design were heavy and had a low electrode surface area, but they had a long life. Such plate electrodes (Plant6 plates) are still used in stationary applications requiring a very long service life [352,354].

Chapter 4

434

Vent plugs partition ~~

“ - L - ~ -

F

j

I

Container Negative plate \

nent rests Sediment space

Figure 2 A traditionallead-acidstoragebattery opment Association, London.)

[356].(Courtesy of Lead Devel-

An effective waytoincrease the solid/electrolyte contact area, and thereby increase the capacity of the system, is to coat the lead sheet/grid with a “paste” of lead oxide and sulfuric acid. Faur6 originally used this concept in 1880. The paste usedto fill the grid consists of a mixture of metallic lead and lead oxides, water, sulfuric acid, and minor amounts of additives and strengthening fibers. The mixing is camed out in a large flatbottomed mild-steel vessel using dough-type paddles or by a pair of broad rotating wheels with horizontally inclined blades. The paste is loaded onto the grids and cured to produce a crack-free paste, with good adherence to the grid. The active material is later converted to the fully charged condition by the process of forming. The fully charged positive electrode consists of a mass of small PbO, crystals connected to each other to form a continuous porous network. In addition to participating in the charge-discharge reaction, the PbO, provide the electron pathway from the reaction site to the

435

Applications of Lead

13

-

-

a,

.

m ,011

-

10

-

'9

-

L12

~

"

-"

\.

m

c,

8. 0.1

1

10

20

Discharge time(hours) Figure 3 Typical current discharge ct~rveso f an automotive lead-acid battery ( 12 V. 40 A h ) (3491. C , . CL.C,. C,,,, ancl C,,, denotes discharge durations o f I . 2. S . I O . a n c l 20 h. respcctivcly 13.561. (Courtesy o f Le:~d Development Association. London.)

grid. The electrode porosity also makes allownnce for the increase in volume that occurs when P b 0 2 is converted t o PbSO,. Figures 4a and 4b show ;I schematic cross section of lead-acid positive plate in the prescnce and absence of conducting additive, and the redistribution of lead dioxide during cycling that leads to its eventual breakdown [3571. The paste is more readily applied to an open-grid support, rather than to a lead sheet. The use of grids require lead alloys with superior rnechanical properties. Grid design takes into account a number of parameters such as weight, corrosion resistance, strength, and current distribution. Grids are designed to ensure a low internal resistance for the cell and t o minimize shedding of active material on cycling. There are four different processing techniques that have been used i n the production of grids: ( I ) gravity or pressure die casting using book molds. ( 2 ) mechanical working of lead strips (Plant6 and Manchester design). ( 3 ) continuouscasting on a shapeddrumsurface, and (4) expansion from wrought strip or cast slabs. slit to width. followed by progressivedieexpansion, precision expansion, rotary expansion, and diagonal slit expansion. Some of these processing aspects were discussed in Chapter 3. Pasted plates have a relatively high capacity and power density but are not mechanically strong. In a typical automotive battery, the real area of the positive electrode is calculated to be SO- 1 SO m'/A h of capacity. With i n creasing current density, the positive electrode voltage is decreased due to

Chapter 4

436

...outside gradually P b 4 accumulate8 th Atter

wvml sycln

AWr

many

...oland, eventually,collapss the aggregate structure

Near Iallun

P b 4 redlstributlon leads to poor conductivity

..

(W

Figure 4 (a) A schematic cross section of lead-acid positive plate in the presence and absence of a conducting additive. (b) Redistributionof lead oxide during cycling that leads to its eventual breakdown[357].(Courtesy of John Wiley and Sons, Chichester, UK.)

concentration polarization as sulfuric acid withinthe pores is consumed. This effect is more marked for partially discharged cells because the pore volume decreases as lead sulfate is formed. The lead dioxide exists in two crystalline forms, orthorhombic (aPbO,) and tetragonal (P-PbO,), both of which are present in freshly formed electrode structures. The stoichiometry of the lead dioxide crystals actually can vary with the O/Pb ratio ranging from 1.85 to 2.05. The equilibrium potential of a-Pb02 is less than that of P-PbO, by 0.01 V. The a-PbO, forms more compact crystals less active electrochemically and slightly lower in

Applications of Lead

437

capacity/unit weight, but it promotes prolonged life. As the a-form is thermodynamically less stable than the p form, some transfonnation of a-PbO? into P-Pb02 may occurduring the life of a battery, with consequent improvelnet1t i n its performance. The lead oxide is produced by either the ball Inill process or the Barton Pot process [357].In the ball mill process, the grinding action on high-purity lead feed results in fine particles of partially oxidized lead. The particles are removed by the airstream and collected in a cyclone. The irregularly shaped platelets with a mean size of 3-4 km and containing up to 25-30% unoxidized lead are obtained. In the Barton Pot process, the lead oxide is produced by the oxidation of tine molten lead droplets thrown up by the agitation of the pure molten lead holding pot. The airstream carries the particles to a cyclone, where they are collected. The Barton Pot oxides are spherical in shape with a mean size of 7-8 pm and unoxidized lead content of up to 40%. Whereas lower antimony levels are preferred to reduce gassing, its complete elimination in grid alloys leads to a decay in the utilization factor with the charge-discharge cycle. As discussed later, the use of sufficient tin in antimony-free Pb-Ca-based alloys mitigates this problem. Antimony helps in forming a tine and low-resistance lead oxide layer, and tin addition to low-antimony alloys helps stabilize capacity. The addition of phosphoric acid to the electrolyte in gel batteries (described later) has a beneficial effect on cycle stability. It reduces the formation of sulfate layers around the grid. Another form of positive electrode is the tubular plate electrode. This electrode consists of a row of tubes containing axial lead rods surrounded by active material. The tubes are formed of woven fabrics made from fibers such as terylene or glass fibers, or of perforated synthetic insulators, which are permeable to the electrolyte. Circular cross sections are commonfor these tubes, but square, rectangular, and oval tubes are also used. Tubular plates are sufficiently strong to withstand continuous vibration and are resistant to shedding. The tubes are sealed at the base with a plastic bottom bar. They are alsoable to sustain many deepdischarges without loss of integrity and are, therefore, suitable for motive-power applications such as EV (electric vehicle) traction [35 1,352,3541.

2.

Negative Electrodes

Negative electrodes are usually made of pasted grid plates. The paste used is similar to that in positive plate manufacture but differs in that the paste here contains expander additions. The paste is reduced under controlled conditions, to form a highly porous sponge lead consisting of a mass of acicular crystals that give a high electrode area and good electrolyte circulation. To prevent the alteration of the spongy acicular crystal mass to larger grains

Chapter 4

438

that have reduced surface area and which are more easily passivated by PbSO, layers, additions referred to a s expanders are made in ainounts of about I %I. These expanders are surface-active materials such a s lignosulfonic acid derivatives and lampblack. The expanders lower the surface energy of the lead and make the formation of large crystals less energetically favorable and also affect the lead sulfate morphology. Additives such as fine BaSO,, which is isoniorphous with PbSO,, encourage the formation of a line-graincd and porous nonpassivating layer of lead sulfate [ 352,3541. 3.

Other Components of the Battery

Porous insulating separator sheets are used to prevent direct contact and short circuit of electrodes of opposite polarity. Separator sheets act as a barrier to the transport of active material between the plates. mechanically support the positive active mass. and prevent dendrite formation. The high porosity leads to a low electrical rcsistance. and the small pore diameter helps in obtaining good separation. Separator sheets are made of polymers such a s sintered poly(viny1 chloride) (PVC) or extruded polyethylene or made of braided or felted fibers resistant to corrosion i n the electrolyte. Monolithic lead-acid battery cases are fabricated by injection molding using synthetic polymers such as polypropylene (PP), styrene-acrylonitrile (SAN), poly(viny1 chloride) (PVC), polycarbonatc (PC), acrylonitrile-butadiene-styrene (ABS), and acrylic ester-styrene-acrylonitrile (ASA). Generally, the lead-acid battery cases are rectangular i n shape. Provisions are made in the case for the location and support of electrode plates. The lid is welded to the case and may contain apertures for terminal pillars, venting valves, screw caps, and automatic systems for adding distilled water to the electrolyte. A schematic of the automotive battery manufacture is shown in Fig. 5 [3571.

C.

Maintenance-FreeBatteries

Water losses in lead-acid batteries are mainly the result of the gas evolution during electrolysis and any such loss must be replenished. The need for water addition or mnintenance is eliminated i n “maintenance-free” (MF) batteries. No addition of water to the electrolyte is required over a 1101-ma1 service life. Reduction of gas formation under normal operating conditions of the battery does ininiinize the water loss. I n flooded. maintenance-free batteries, the water loss is minimized by the use of modified positive grid and strip alloys in which the amount of antiinony and other elements that promote hydrogen and oxygen evolution are substantially reduced or eliminated. The strengthening in these alloys are obtained by the use of calcium and other elements such a s tin.

439

Applications of Lead OXIDE MANUFACIURE

The loss of water may be reduced further by recombining the gases formed during electrolysis t o form water. which is fed back into the battery. An essential part of this recombiner is a catalyst containing a noble metal i n which the recombination reaction takes place. A protective mat i n l'ront of the recombiner sieve protects it from the aggressive acid spray. Only 70%) o f the hcat cncountercd during this process is from recombination reaction,

440

Chapter 4

whereas 30% of the heat results from the condensation process. The catalytic efficiency of such recombiners is 90%. In addition, condensation efticiency is SO%, and 20% escapes as water vapor through openings in the converter. However, flooding of the catalyst has proved to be a problem [353].

D. Valve-Regulated Lead-Acid Batteries with immobilized Electrolyte In a new generation of MF batteries referred to as “Valve-Regulated LeadAcid” (VRLA) batteries, the electrolyte is immobilized by means of gel formation or by incorporation in an adsorptive glass mat or other microporous separators. The oxygen evolved at the positive electrode is transported and recombined with hydrogen at the negative electrode. The batteries are constructed in leakproof enclosures with a one-way valve-regulated vent to release excess gas pressure. These batteries have a much higher charge retention in comparison with more conventional units, up to 30% of capacity after 1 year. The absence of escaping acid vapors eliminates the corrosion of metalliccomponents,because of the low-gassinggridalloys and high purity of materials used in the manufacture. A schematic of a valve-regulated battery is shown in Fig. 6 [ 3 5 8 ] . Figure 7 showsavalve-regulatedleadacid cell battery with tubular positive plates and a gelled electrolyte [359].

Figure 6 A schematic diagram of a valve-rcgulatedlead-acid (Courtesy of Elsevier Science, Oxford, UK.)

battery [3581.

Applications of Lead

441

Figure 7 An advanced valve-regulated lead-acid cell with tubular positive plates and gelled electrolyte [359].(Courtesy of Elsevier Science, Oxford, UK.)

In a valve-regulated lead-acid battery, the oxygen evolved at the positive electrode is reduced onthe negative electrode by direct electrochemical reduction. The oxygen can oxidize the lead of the negative electrode to lead oxide (PbO) (discharged), the lead oxide will react with the sulfuric acid to lead sulfate (PbSO,), and, finally, be “recharged” to lead (Pb).The sequence of reactions at the negative electrode (Fig. 8) is given as [355].

2 Pb(s)

+ O,(aq) + 2 PbO

+ 2 H2S04+ 2 PbSO,(S) + 2 HZO(1) + 4 H+(aq) + 4e + 2 Pb + 2 H,SO,(s) PbSO,(s) 2 2 PbO

(9) (10) (11)

The overall reaction can be written as

For this oxygen cycle to be complete, oxygen should not escape from the

442

Chapter 4

Figure 8 Reactions thattake place during recharge of a VRLAbattery (Courtesy of Dr. J. E. Manders, Pasminco, Australia.)

[355].

cell and the quick transport of oxygen to the negative electrode must occur. The rates of these processes are dependent on temperature, electrolyte composition, and impurity content. Apart from the control of elements in the electrode that promote gassing reactions, control of electrolyte impurities such as Fe’+ ionswhichcanbere-reducedatthenegativeleadsis also needed to minimize very rapid self-discharge [352].Placing the batteries on a maintenance charge when not in use can minimize the loss in capacity due to self-discharge reactions. The low diffusional rate of oxygen in the sulfuric acid would limit the oxygen cycle to a very low current. The electrolyte in VFUA batteries is immobilized by the soaking of sulfuric acid in a glass mat or by the fixing of sulfuric acid as a gel. In both cases, open pores and cracks allow easy oxygen transport to the negative electrode. On the negative electrode, the overcharge reaction consists mainly of a reduction of oxygen, but a minimum of hydrogen development always remains because the rest potential of the negative electrode is far below the equilibrium potential for hydrogen evolution. Minimum hydrogen evolution is the lowest gassing rate of the negative electrode thatincludes the self-discharge.Optimally,thisis <3 mA/100 A h, (3% self-discharge permonth) [353]. Therefore, “sealed” lead-acid batteries always have to be equipped with a valve, except for very small cells, from which the hydrogen can escape by diffusion through the plastic cell walls, to avoid excessive pressure in the cell. In recent years,

Applications of Lead

443

valve-regulated automotive batteries, stationary batteries, portable batteries. and traction batteries have entered the marketon a significant scale.The advantages of these batteries are no spillage of acid, the possibility of operation in any position, little hydrogen development, and no acid vapors. as there is n o electrolyte surface producing gas bubbles. The disadvantages are an higher amount of lead in the cell, shorter service life, and limited ability to check the condition of the battery. Corrosion of the positive grid can O C C L I ~on charging and overcharging. This leads to ;I progressive weakening of the plate structure and to an increase i n the internal resistance of the cell. If a lead-acid battery is left for ;I prolonged period i n an uncharged state or is operated at too high temperatures or with too high a n acid concentration. the lead sulfatedeposit is gradually transformed by recrystallization into a dense, coat-se-grained form. This process is known as sulfation and leads to severe passivation. particularly o f negativeplates, and. therefore. inhibits chargeacceptance. It is sometimes possible to restore a sulfated battery by slowcharging i n very dilute sulfuric ucid. The current goals of the Actvancc Lead Acid Battery Consortium (ALABC) for electric vehicle batteries are specific power of >200 W/kg, power density of >SO0 W/L. specific energy o f SO W h/kg. energy density of 100 W h/L, cycle life of 500. ancl recharge rates of 50% in S min. 80% i n 1 S min, and 100% in 4 h. These are more ambitious than othcr udv~unced battery systems [360.3611. The goals of fast charging and higher charging efficiency has already been accomplished in the new VRLA batteries, Some or the current efforts include development of optimized tubular and flat gricls with improved surface area and active material utilization. The llat tubular design for itnproved active material utilization is shown in Fig. 9 [360].The

Chapter 4

444

problem of premature capacity loss due to expansion/contraction of the active mass during cycling is being addressed through the development of high-compression valve-regulated designs. Other efforts include the development of improved materials for grid, AGM mat, and expander.

1.

Battery-Grid Alloys

Alloying additions are made to improve mechanical and electrochemical properties of lead-acid battery grids and spines. The Pb-Sb-based ternary alloys with As, Sn, Ag, Se, Cu, S, and Cd and Pb-Ca-based ternary alloys with Sn, Ag, and AI have been considered in grid alloysfor batteries [ 1 1 1,362,3631. In the early battery grids, Sb was the main alloying element used and up to 1 1% Sb was used. By 1950, the phenomenon of Sb poisoning ofthe negative plate was recognized and the Sb content was decreasing, with 6-9% Sb alloys becoming common. However, the low-Sb alloys had inferior castability, mechanical strength, and corrosion resistance under battery operating conditions. Arsenic addition increased the rate of age hardening and reduced the time of grid storage required after casting. Arsenic also increased creep resistance, which was very beneficial in deep cycling conditions. The Electric Storage Battery Co. of USA used a 0.5% As addition to a 6% Sb alloy for positive grids, even in automotive applications. The Sn addition increased fluidity and thus castability. It increased cycle life of batteries containing thin plates. Chloride Electric Storage Battery Co. added 2.5 wt.% Sn in Pb-9 Sb positive grids for a special military battery for cycling service. Ag additions increased both the corrosion and creep resistance in Pb-Sb-alloy grids. The disadvantage was the high cost of Ag. Continuous pressure to reduce Sb to below 6% led to the development of Pb-Sb alloys with less than 3% Sb.Se,Cu, and S were used as the addition to Pb-3 Sb to refine grain size, and among these, Se was the most effective and widely used. Sn additions were used to act synergistically with As and Sb to improve fluidity and castability. Ag improved corrosion resistance. CO also is thought to improve corrosion resistance. Cd additions improved castability oflow Sb alloys, as it decreased the two-phase solidification range. Corrosion resistance was also improved. Pb-( 1.5-2.5)Sb(1.5-2.5)Cd alloys had good properties, but Cd use was inhibited by environmental considerations. Cast Pb-Sb-based alloys are typically used in grid alloys as the PbSb-based wrought alloys have lower yield strength, tensile strength, and creep strength compared to cast alloys. Corrosion behavior of wrought alloys are inferior because of the nature of the distribution of the Pb-Sb eutectic phase and lower creep resistance. Corrosion of cast Pb-Sb alloy occurs by the attack of the Pb-Sb eutectic phase. It solubilizes some Sb and stresses

Applications of Lead

445

of corrosion product are accommodated. In rolled alloys, the eutectic phase is isolated, which leads to stresses in the grid. As mentioned earlier, Sb migration from Pb-Sb-based positive grid :llloys to negative electrode results in the reduction of hydrogen overvoltage and consequent decrease in cell voltage. This led to increased degassing and water loss. The move to purer systems with no poisoning of negative plates led to the use of Pb-Ca alloys. The cast and wrought Pb-Ca binary alloys are significantly inferior to cast Pb-Sb alloys in hardness, creep resistance, and corrosion resistance. Thecycle life of lead-acid batteries is mainly limited by the performance of the positive plate, the capacity of which decreases on cycling, especially under deepdischarge.The common degradation mechanisms [ 3571 include ( 1 ) loss of interparticle contact, (2) shedding of active material due to morphological changes and grid corrosion, ( 3 ) grid deterioration and growth, and (4) irreversible plate sulfation due to acid stratification effects. The growth of positive plates due to corrosion in service reduced the cycle life in batteries with Ca grids and low-Sb alloy grids. This is attributed to ( 1 ) the formation of high-resistance a-PbO on the grid, (2) the increased tendency for cracking and delamination of corrosion layers, and (3) the structural changes in active material that is aggravated by the absence of Sb in the grid alloy. This effect together with other plate mechanisms that reduce battery life to fall well short of design life is known as the antimony-free effect or premature capacity loss (PCL). The antimonyfree effect underlined an urgent need for additions to Pb-Ca. The mechanical properties in Pb-Ca binary alloys peak at 0.07% Ca. Above 0.06% Ca, cellular precipitation of Pb,Ca leads to the fine-grain size. In VRLA batteries, using thin grids of high Ca have been used to aid processing (faster aging rate), but they produce fine grains. Increasing Ca contents above the 0.07% level accelerates corrosion and this is believed to be due to fine grains and primary Pb,Ca. Sn additives increase mechanical properties by changing the mode of precipitation as the precipitate phase is changed from Pb,Ca to more stable Pb(Sn,Ca),. Sn addition aids electrochemical properties by preventing passivation of the grid and permitting recharge of batteries from the deeply discharged condition. Pb-Ca-Sn alloys have become established in traditional automotive batteries and in VRLA batteries. Pb-Ca-Sn alloys are inferior to Pb-Sb-As alloys in terms of mechanical properties, but the properties are adequate. Additions of Ag to Pb-Ca and Pb-Ca-Sn alloys increases creep and corrosion resistance and the durability of batteries. Pb(0.025-0.06)Ca-(0.3-0.7)Sn-(0.015-0.04S)Agpositive grid alloys show improved creep and corrosion resistance. Increased Ag additions are being considered for severe deep cycling conditions. The addition of AI tends to stabilize drossing loss of Ca. Pb-Sr alloys are better than corresponding

Chapter 4

446

Table 1 Typical Composition Range of Battery-Grid Alloys Alloy

Coinposi t ion

Conventional high-Sb alloy-cast LOWSb tilloys-cast Cnst/wrought Pb-Ca-Sn

Ph-(9- I2)Sb-(0.3S-O.S)As Pb-2.SSb with other minor additions Pb-(0.025-0.06)Ca-(0.3-0.7)Sn-(O.O1 S 0.04S)Ag with minor Al addition

Pb-Ca alloys, but the high cost of Sr is an inhibiting factor as long as PbCa-based alloys are behaving adequately. Other grid alloys that have been used include ASTAG alloys (Pb with small amounts of As, Te, and Ag) and ASTATIN alloys (Pb with small amounts of As. Te, Ag, and Sn). Composite grids involving lightweight metals as well as polymers are being explored. Purity levels are strictly controlled in grid alloys, active materials, and electrolyte to minimize elements that promote degassing, corrosion, and passivation of electrode. These elements include As, Co, Cr, Cd, Cu, Fe, Ni, Sb, Te, and Se. Bi has been claimed to have beneficial effect of reducing degassing, but conflicting opinions on the influence of Bi are expressed in the literature. Fe is also detrimental from drossing considerations. The future efforts are expected to be directed toward development of higher-tin-content Pb-Ca alloys, Ag addition to Pb-Ca alloys, Pb-Sr alloys, Pb-Li alloys, and very low-Sb alloys. The development of newer alloy systems and the continued use of existing grid alloys is being reevaluated from the point of recycling of Pb in the battery alloys. These issues are discussed later. Grid alloys for battery applications and their mechanical properties have been already covered i n Chapter 2. Table 1 provides the composition ranges of typical battery-grid alloys.

E.

Bipolar Batteries

One of the factors that limit the specific power (W/kg) is the voltage drop in the cell due to internal resistance of materials used as current collectors and of the electrolyte. A significant reduction of resistance is achieved by a design of bipolar electrode storage batteries. The geometrical configuration of a bipolar battery is shown in Fig. 10 13.561. Here, one side of the lead sheet acts a s a cathode and the other side acts as the anode of the adjacent cell. Between the plates is a microglass tiber separator that absorbs and retains the electrolyte. The cells are connected in series and provide a higher output voltage. Bipolar batteries provide a better performance than traditional systems when high currents are required. Figure 1 1 shows a typical

Applications of Lead

447

Figure 10 Configuration of a bipolarbattery [356]. (Courtesy of Lead Development Association. London.)

current-discharge curve for a battery [356].

bipolar battery compared with a traditional

F. Types of Lead-Acid Battery and Their Applications As mentioned earlier, there are three main types of battery: SLI (starting, lighting, and ignition) batteries, industrial batteries (traction and stationary), and small sealed portable batteries [351-3531. 1. Starting,Lighting,andIgnitionBatteries Starting, lighting, and ignition batteries are used for cranking automobile internal combustion engines and for powering devices when the engine is

Chapter 4

448

-

15 14

-

Tradilionalsealed battery DIPOLAR battery

0.1

1

13

12 11

10

9

10

20

Discharge time (hours)

Figure 11 Typical current-discharge curve for a bipolarbatterycompared with a traditional battery [356].(Courtesy of Lead Development Association, London.)

not running. Nearly 80% of all lead-acid battery production goes to supply the automotive market. SLI batteries should be capable of supplying short but intense discharge currents at rates of greater than 5 C over a wide temperature range. They are generally constructed of thin pasted plates, with thin composite separator/retainer layers and short connector buses to minimize the internal resistance. In this unit, the positive plates are usually inserted into pocket-shaped separators to increase their resistance to shock and prevent the shedding of material onto the cell floor. The through-partition connections reduce the internal resistance and weight of the battery. In recent years, maintenance-free batteries using advanced alloy grids (and catalytic recombiners) and valve-regulated batteries have become more common for SLI applications. SLI batteries generally have nominal voltages of 12 V and 30-100 A h capacities for cars, and 24 V and up to 600 A h for trucks and construction and military vehicles [352]. Typical specific energies of SLI batteries are 30-40 W h/kg (75 kW h/n13) may be obtained. Service lifetimes of 4-6 years are nonnal. For vehicles used in rugged terrain, batteries with tubular positive plates are required. 2.

Motive Power Batteries

Motive power lead-acid batteries are designed for use in electrically powered industrial trucks, aircraft service vehicles, electric service vehicles used

Applications of Lead

449

in industry and hospitalcomplexes,robots,andguidedvehicles. The key requirements of motivepower batteries areconstant output voltage, high volumetric capacity at relatively low unit cost, good resistance to vibration, and a long service life. The electric motors using the motive power require high currents for longperiods, so the traction batteries must be able to sustain prolonged and deep discharges followed by recharges at 1-5 h rates. Cycle life could vary from 1000 to IS00 cycles. This is based on discharges to 80% of the 5-h capacity when charged according to the manufacturers recommendations. Operation at lower depths of discharge extends the cycle life substantially. Two-volt cells in 24-96-V assemblies are common. The voltages of traction battery assemblies vary over a wide range from 24 to 240 V, with capacities from 100 to IS00 A h. The specitic energy of these units is typically 20-30 W h/kg 13521. Both flat-plate/grid and tubulardesignsare widely used in motive power batteries. In tubular-design cells, the positive tubular plates consist of a series of parallel porous tubes, each having a centralized lead conductor surrounded by active material. The negative plates are of standard flat-plate construction. A separator envelope wraps around either the positive or negative plate. The Hat-plate-design motive power cells are similar to SLI batteries, but the electrode plates are thicker and more robust. The cells are built with three layers of separator, consisting of a perforated spacer, a glass mat, and a microporous plastic separator. The higher surface area and the larger quantity of acid in tubular cells lead to higher utilization of the active material and a higher energy density than flat-plate cells. However, the flatplate designs usually have ahighercycle life and durability than tubular cells. Tubular cells also have a lower self-discharge rate, as the conducting grid is buried within the active material; impurities, such a s antimony, released as a result of corrosion during service are adsorbed by the lead dioxide and contamination of the negative plate is reduced. This also results in more stable voltage characteristics and a higher voltage at the top of the charge in tubular cells. The capacity of these batteries is usually quoted at the S-h rate of discharge in North America and at the 6-11 rate in Europe. Electric vehicle batteries are usually assembled in 6- or 12-V monoblock units a s distinct from the more usual 2-V cells used in motive power battery arrays, giving a further improvement in energy density. Unlike the standard traction cell, they are usually rated at the 3-h rate of discharge. The General Motors EV1 electric vehicle, which has been offered in the North American marketsince 1996, has an electrical traction powersystem that provides power at 3 12 V from 26 maintenance-free valve-regulated leadacid (VRLA) batteries (361,3631. The battery pack consists of Delphi Automotive 12 V VRLA battery monoblocks. The lightweight and sleek vehicle (Fig. 12) has a dent/corrosion-resistant composite exterior body panels and

Chapter 4

450

g

l

Figure 12 GeneralMotors EVl electric car [361]. (Courtesy of General Motors Corporation, Detroit.)

a rigid, welded, and bonded aluminum alloy frame [361]. The vehicle has an electronically regulated top speed of 80 mph and the EVl prototype has set the land-speed record for electric cars at 183 mph. The car has a 0-60 mph acceleration in less than 9 S . The estimated range of this vehicle at 85% of battery charge is 70 miles in the city and 90 miles on the highway. The charging times with 15% capacity remaining are approximately 3 h using a 22O-volt/6.6-kW charger. A regenerative breaking system recovers kinetic energy to help recharge batteries. The battery pack weight is 533 kg and the total vehicle weight is only 1350 kg. Advanced designs for the electric vehicle involve increasing specific energy through the reduction of inert components and improving active material utilization [360,361,363]. The increaseinspecificpower is being achieved through the minimization of internal resistance by (1) developing thinner plates withhigh surface areas, (2) improving current collection schemes with new grid designs, (3) increasing gridhop-lead conductivity by the use of composites, (4) developing low-resistance separator materials, and (5) minimizing current pathways. However,efforts to increase specific power and recharge capabilities are generally incompatible with cycle life. Dualbattery concepts in which one unit is optimized for range (specific energy) andthe other unitoptimized for accelerationand hill climbing (specific power) are also being considered.

3.

StandbyBatteries

Standby batteries are used to power essential equipment, critical computer systems, alarms, and emergency lighting when there is a breakdown in the main power supply.Reliability and long service life are critical. In the recent years, the standby battery market has grown rapidly with an increasing demand for unintermptable power systems (UPS) and power systems for new telecommunication networks. For a long time, standby batteries were made

Applications of Lead

451

using the Plant@cell design because of long life, in excess of 20 years. Plant6 cells are still used to some extent in electricity-generating stations. Both tubular and flat-plate designs similar to traction cells are also widely used. These batteries have life expectations of over 1 0 years. In recent years, sealed valve-regulated batteries are increasingly used i n telecommunication and UPS applications. These batteries have service lives of more than I O years, do not require water maintenance, are claimed to be small i n size, pose no risk of acid spill, and can be located in offices without special venting requirements, as they release only small amounts of gas. These cells occupy 70% less space than Plant6 cells of equivalent capacity. The capacities of these batteries are usually quoted at a 3-11 rate of discharge. The available standby time at either constant current or constant power discharge depends on the end of discharge voltage specitied. In certain applications, such as telecommunications, the load is driven directly from the direct-current (DC) output of a rectifier and stabilizing circuit. Across this output is a bank of batteries to drive the load in the event of supply failure. The rectifier serves both the functions of driving the load and of charging the batteries. Telecommunication equipment usually operates on a nominal 24-V or 50-V DC supply with typical tolerances i n the region of + 5% to - 10%.

4.

Portable Batteries

The use of portable sealed valve-regulated lead-acid batteries for use in electrical appliances and electronic equipment have increased significantly in recent years. The critical requirements in these batteries are that they must be transportable and usable in any position without leakage. The cells are made i n cylindrical, prismatic forms or flat-pack forms. The electrolyte immobilized by absorption of electrolytes in porous glass mat or by gelling of electrolytes. All cells with these designs are sealed with a pressure-relief valve located below the external cover. These batteries deliver 1-30 A h and are used as single cells and as 12-V monoblocks. Operational temperature, discharge rate, depth of discharge, and charging method affect the service life of these batteries, in common with other lead-acid battery designs.

G.

Large-scale Energy Storage for Load Leveling

The consumption patterns of electric power varies widely depending on the time of the day or the time of the year. A constant consumption of power would allow utility companies to utilize the installed power-generation capacity more efficiently by having high load factors. Given the reality of varying demands for power, utility companies often employ energy storage procedures at off-peak periods (e.g., when demand for electricity is low-

452

Chapter 4

during the night and weekends). The stored energy is used during the peak demands for power or during the intermediate period when the utility brings on-line the intermediate-load,oil-tired(or gas-fired) combustionturbines during extended peak demands. Among the possible energy storage schemes that utilities may use are pumped hydroelectric systems, compressed-air energy storage facilities, and battery energy storage plants 1364-3681. Woodbridge [366] proposed the use of battery storage plants in various generation/distribution environments as early as 1907. BEWAG, the oldest public utility i n Germany, installed the first battery storage plant in 1893. The total capacities of these plants were 100 MW and they were used in parallel with the DCsupplysystems. With increasing use ofAC power supplysystems, the use of battery storagedecreased and the use of gas turbines for load managementbecameattractive,extensively a s backup power-generation systems and to meet peak demands [367]. The rapid development of power electronics and control engineering has led to the availability of highly sophisticated static power conditioning systems at reasonable costs. This allows the use of batteries within AC systems. An Electric Power Research Institute (EPRI) funded study compared the cost of variousenergystorageschemes that included compressed air, pumped hydro,combustionturbines, and lead-acid batteries. The study showed that lead-acid batteries are the lowest-cost option for duties of about 1 h, with combustionturbines being most cost-effectivefor 2-S h, and compressed air the preferred option for longer periods [36S]. In power-generatingutilities, the battery storage plants are used for load leveling, load frequency control, and instantaneous reserve. The random load fluctuations superimposed on the general trend of the load curve have tobe within thepowermarginfor regulation and thepermissiblepower gradient that is a function of permissible frequency fluctuation. Typical values for power margin and power gradient corresponding to a power-generating utility in West Berlin are 40 MW and I O MW/s,respectively, for a system peak load of 2000 MW and a permissible systems frequency within the range 49.8-50.2 Hz [367]. For economical reasons, generating units in small interconnected systems tend to be large. The faults occurring within the unit or interconnected systems can cause significant imbalance of generated power and load. This can cause large deviations in the system frequency. Subsequent to a fault at a power-generating utility or in transmission,quick-actingreserve units called a“spinningreserve” must come on-line immediately. Their power must be delivered for a time interval sufticient to start up and synchronize a spare generating unit. As electric utilities must provide sufficient emergency power-generating capacity at all times to replace their largest unit in case of failure(known as spinningreserve),

Applications of Lead

453

battery energy storage systems can dedicate part of their capacity as emergency spinning reserve, especially during off-peak and mid-peak hours. Battery storage schemes have the benetit that they can be virtually any size, can be located anywhere within the distribution system, and can operate at any of the system voltages. Battery storage also allows operation of the main generating unit at efficient operating points. The ability to site batteries at major load centers, such as substations, enables deferral of costs for transmission and distribution equipment, increases transformer bank life, and reduces power-line losses. As the stored battery power is availablealmost instantaneously (even while the battery system is being recharged), the system stability and security can be enhanced by the fast-acting battery response. Operating within the distribution system means that load management can be localized, enabling the peak factor within a specitic region to be reduced. Because equipment ratings are based on peak demand. any reduction allows these to be more conservative 1364,365,3671. Energy storage by means of lead-acid batteries offers many other operating benefits to an electric utility. They allow the purchase of economy power during minimum loading conditions and storage for later use to manage peak loads. Battery energy storage systems allow expansion or downsizing as the local or system peak load requirements change, by adding (or removing) individual batteries. Shorter lead times are required to design and install a battery energystorage facility ( 2 yearsorless). Battery energy storage systems do not contribute to acid rain, fly ash, or noise because they are clean and quiet and can be operated in ordinary building enclosures. The economy of a load-leveling battery storage system is largely dependent on the prevailing load-curve characteristics. The limits of economical utilization of battery storage for industrial consumers have been described by Hagen 13691. Depending on the shape of the load peaks and the tariff situation, reasonable load reductionsrange from 5% to 15% of the peak load for peaking periods shorter than 3 h. At the present time, many battery energystorage plants are in use. Most of these plants are using lead-acid technologies of different contigurations, including flooded electrolyte cells, VRLA, automotive, or submarine batteries. Table 2 lists the different large-scale installations worldwide 13641. The choice of lead-acid cells for these applications is due to the attractive feature it provides at lower cost. Table 3 compares the properties of competing storage battery systems in large-scale energy storage [361].

H. Storage of Renewable Energy There is considerable interest in the use of lead-acid batteries to store energy from the power produced by renewable energy sources such as photovoltaic,

P

UI P

Table 2

Large-Scale Battery Energy Storage Plants Worldwide [363] _ _ _ _ _ ~

~

Companyllocation Southern California Edison. Chino. CA, U.S.A. Crescent Electric Member Cooperative, Statesville, NC. U.S.A. Delco Remy, General Motors, Muncie, IN, U.S.A. BEWAG AG, Berlin, Germany Kansai Electric Power Company, Tatsunii, Japan Elektrzitatswerk Hammermuhle. Selters, Germany Hagen Batterie AG, Soest, Germany San Diego Gas and Electric, San Diego, CA, U.S.A. Puerto Rico Electric Power Authority, San Juan, PR Pacific Gas and Electric, San Ramon, CA, U.S.A. Pacific Gas and Electric, various sites in CA. U.S.A. Hawaii Electric Light Company, Island of Hawaii (Big Island), HI, U.S.A. Chugach Electric Association, Anchorage, AK, U.S.A. Golden Valley Electric Association, Fairbanks, AK, U.S.A. Oglethorpe Power Corporation, Atlanta. GA, U.S.A.

Size

Operation application

Date

10 MW/4O MW h 500 kWl500 kW h

Utility energy storage demonstration Peak shaving

1988 1987

300 kWl600 kW h 17 MW/14 MW h

Peak shaving Frequency regulation/spinning reserve Multipurpose demonstration Load leveling Load leveling Transit peak shaving Frequency regulation Distributed peak shaving Distributed peak shaving. T & D deferral Frequency regulation/spinning reserve Frequency regulationlspinning reserve Frequency regulation/spinning reserve Power quality

1987 1986

1 MW/4 MW h 400 kW/4OO kW h 500 kW/7 MW h 200 kWl400 kW h 20 MW/14 MW h 250 kWl167 kW h 500 kW/1 MW h (up to 4 units) 10 MW/15 MW h

20 MW110 MW h 70 MW/17 MW h 2 MW/IO s

I 9x6 1980 1986 I992 1994 1993 1994 1994 199s 1995

P

b 9, ii' 0

Table 3 Status of Battery Systems in Competition with Lead-Acid Batteries 13611. (Courtesy of John Wiley and Sons, Chichester, UK.)

System Acidic aqueous solution Lead-acid Alkaline aqueous solution Nickel/cadmium NickeI/iron Nickel/zinc Nickel/metal hydride Alurninum/air Iron/air Zinc/air Flow Zincbromine Vanadium redox Molten salt Sodium/sulfur Sodiurn/nickel chloride Lithiumhron sulfide (FeS) Organic/lithium Lithium ion

P,

Specific energy (W h k g )

Peak power Wkg)

Energy efficiency Cycle life

Selfdischarge (W48 h)

ill nl

Q

35-50

1 50-400

40-60 50-60 55-75 70-95 200-300 80- 120 100-220

80- 150 80- 150 170-260 200-300

70-85 20-30 150-240

>80

75 65 70 70

500- 1000

0.6

120- 150

800

1 3 1.6 6

250-350 200-400 100-300 200-350

1500-2000 300 750- 1200+

160

<so

90 30-80

60 60

500 + 600 +

90-1 10 I10

65-75 75-85

500-2000

90- 120 100-130

230 130- 160 1 50-250

85 80 80

800+ 1200+

0 0"

1000+

?

250-450 230-345 110

80- 130

200- 300

>95

1 ooo+

0.7

200

"No self-discharge. but some energy loss by cooling.

?

9

?

.?

>

50 90- 120 200-250 400-450

-

P

UI UI

456

Chapter 4

wind, hydro, and tidal systems.These energy sources provide fluctuating output. The use of lead-acid batteries is attractive to store excess energy as a way of normalizing output or to get a substantial reserve. Lead-acid batteries with a good deep cycling capability and long life are required. Maintenance intervals are usually a minimum of 6 months, and the cell design must accommodate the necessary amount of electrolyte or be fitted with an automatic watering device. Plant6 cells, tubular cells, and flat-plate cells may allbeused for this application. The discharge times are long. The photovoltaic-based RAPS system on Coconut island, Torres Strait, Australia that provides continuous AC power to 130 inhabitants is a good example of the benefits of the RAPS system [370]. One of the largest projects in Remote Area Power Supplies for the storage and delivery of solar energy using lead acid batteries is being planned for the Amazon region in Peru [371]. A study to assess the potential for RAPS in the Amazon region is funded by ILZRO; this study attempts to define the specific activity to install the first RAPS systems following the agreement signed in June 1997 between the ministry of Energy and Mines (MEM) in Peru, the Solar Energy Industries Association (SEIA) and ILZRO. The project involves the design, manufacture, management, installation, operation, and financing of the first RAPS systems in the Amazon region of Peru. The funding for the project is to be obtained from multilateral financiers, most specifically the Global Environmental Facility at the World Bank. The project will consist of installing six 150-kW h/day power modules into two community power RAPS systems at Padre Cocha (300 kW h/day) and Indiana (600 kW h/day). The project is expected to cost US $1.875 million for these systems, although options are provided for additional or alternative systems. The modular community power RAPS systems will be integrated into existing electric networks and diesel-generator sets; the project is scheduled for completion within 1 1 months after start. RAPS power modules are to be assembled in Peru. The power system will use modular building blocks. These building blocks include gelled VRLA batteries, a power conditioning system, a 15 kW of photovoltaic array, and a local control/monitoring system. A typical community power system will consist of oneormore of these building blocks, along with an interface to the existing diesel generator, a supervisory control system, and a remote monitoring system. The project load increases could shorten this payback considerably. The system has 25% of the fuel consumption and 15% of the maintenance costs of an equivalent system based on a prime diesel generator. The RAPS system, when completed, will eliminate nearly 19,000 tons of COz and over 900,000 lbs of NO,, compared with an equivalent prime diesel generator. The total value for these savings is $2.7 million over the 20-year life of the project. The RAPS system will

Applications of Lead

457

provide much needed electricity for economic development, reduce emissions in the Amazon region, and (with a payback period of 12.8 years or less for the project cost) reduce the costs to the Peruvian government for supplying fuel and electricity to these remote villages.

1.

Recycling of Lead from Batteries

Nearly 71% of thelead produced today is consumed in the production of batteries 13721. Fortunately, for the benefit of the lead industry and environmental protection, batteries are now completely recyclable [373]. Because of the complications involved in determining recovery rates, detailed calculations of recovery rates are not available. Recovery rates of industrial batteries are nearly loo%, whereas the recovery rates for consumer batteries is somewhat less. Conservative estimates suggested a 98% recovery rates in the United States in 1990. Recovery rates in Europe were higher than 85% i n 1993. These rates have steadily increased with improvements in collection schemes for spent batteries, and today, nearly 100% of batteries are recycled and, as mentioned in Chapter 1, more than 50% of lead produced in the world comes from recycled lead. Lead is probably the most recycled element today. Besides Pb and PbO, the plastic cases and other material are also recycled. Batteries represent a relatively concentrated source of lead. Both pyrometallurgical and hydrometallurgical recycling schemes have been pursued. Modern recycling facilities include a first-stage automated breakup, from which polypropylene case material is extracted and reclaimed.Cell parts consisting of grid metal, lead oxide/lead sulfate paste, top lead parts, and separators form the feedstock for the furnace together with controlled amount of lime. The refining stages differ from primary lead production, as few of the natural ore impurities are present in recycled lead. The limits of toxic elements in gas emissions, slag, and effluent water is a major factor in the recycling processes being adopted. Hydrometallurgical recycling schemes are also available. The elements in grid alloys that cause problems in recycling are As, Se, Ag, Cd, Sn, and Cu [374]. The elements that enter the recycling stream from posts and straps in batteries are As, Se, Cu, Ni, Sn, and Ag. Cd is fumed from the metal to dust.Cdemissionhas to be controlled to very low PEL (personnel exposurelimit)levels. Cd is extremely soluble as lead sulfate and causes problems in wastewater. Copper is a major producer of dross in lead refining. About a half of the refining time and treatments involve copper removal. An even higher effort occurs in obtaining low copper levels. Nickel causes drossing and plugging of lines in die casting. It causes gassing even at low levels in VRLA batteries and should be removed to low levels. Nickel enters the stream as stainless-steel nuts and parts. Arsenic is fumed from grid material as As203and can go

Chapter 4

458

through bag houses using high-temperature bags (gas at 193°C). I t can react with chlorides and fluorides to produce low-boiling-point materials, such as ASCI, (63"C), AsF, (-63°C). The low PEL makes it a difficult element with which to deal. It causes problems in TCLP leach test for slags. Se is fumed from grid materials as SeO, in the furnace. This is also a problem element in TCLP leach tests for slags. It is a problem element in SO, scrubbers producing soluble selenates (Na,Se,03)in scrubber solutionsand wastewater. Sn must be removed by pyrometallurgical refining and most of the Sn is lost in slag. Sn recycling circuits are not adequately developed at the present time. Ag cannot be removed economically at low levels from recycled lead. Buildup can exceed specification limits in lead for pure oxide production. Ag transferred from the positive to the negative grid causes negative voltage changes. Higher Ag content in recycled lead will affect all producers for several years [374]. The future design of batteries and choice of materials for grids and other components will thus be determined by recycling considerations. Some of the suggestions for the future include the elimination of the use of Sb and Cd in battery grids, the reduction and restriction of As to low levels in Pb-Sb grids and strap alloys, the restriction of copper from grids and posts, the substitution ofAg a s an alloying element in positive grids,and the development of Sn-recovery circuits.

II. USE OF LEAD IN EARTHQUAKE PROTECTION A.

Introduction

The excellent damping capacity of lead and its malleability make it a valuable material in seismic protection devices. The collapse or structural damage to buildings, bridges, and other structures and the toppling of material and equipment under the influence of seismic waves generated by an earthquake is a serious concern,particularly i n areas of the world prone to seismic activity. The economic impact of an earthquake could be devastating, as the recent earthquakes in San Francisco, CA and Kobe, Japan amply demonstrated. Designing and incorporating interfaces between the building and the earth that damp seismic wave or isolates the building and their foundations from the earth's movement could provide the structural stability and minimize the damage due to earthquakes. Such structures protected from earthquakes by isolation and damping are referred to as seismically isolated or base-isolation structures.The lead and its alloys are a key component i n these seismic isolation interfaces [ 375-3781. The isolation interface consists of isolators and dampers i n the lowest floor of the buildings. If this interface is designed appropriately, the behavior

Applications of Lead

459

of buildings during earthquakes can be controlled to a certain extent. The function of isolators is to support buildings and, in the case of an earthquake, to cause a moderate degree of lateral displacement. These are commonly made from laminated rubber. Dampers, although not effective in supporting the load of a building, are able to dissipate the energy generated by earthquakes and control the deformation of the isolation interface. Steel and lead alloys are commonly used in damping. Isolation system can be of two types: an integrated system and the independent hybrid system. In the integrated system, the damping mechanism is integrated in the isolators such a s a highdamping rubber bearing and a lead-rubber bearing (LRB). In the Independent hybrid system, the damper can be set up separately from isolators. Installing integrated devices such as LRBs is fairly straightforward, but its overall design in integrating the functions of the dampers and isolators could be very complex. If dampers and isolators are fitted separately, their functions are clearly well defined and this provides increased flexibility in design. Dampers installed separately from isolators in this way include hysteresis dampers made traditionally from steel and lead materials as well as others such as viscous oil dampers. Among these, dampers made from lead have superior performance i n dissipating energy and can sustain repeated deformation due to the superior malleability of lead and its recrystallization mechanism based on repeated deformation. There is a growing acceptance of base-isolation structures and the characteristics of base-isolation devices such as lead dampers. Since the Great Hanshin earthquake in Kobe, Japan, base-isolation systems have been installed in over 150 buildings in Japan and the number is expected to increase. A significant amount of LRB arid lead dampers is being utilized in these new base-isolated buildings and the demand for base-isolation devices using lead is consequently expected to increase. The scale of buildings and applications utilizing this base-isolation technology has greatly increased, and in 1997, a base-isolation system was installed in a nuclear power plant. Since 1987, the International Lead Zinc Organization has supported the development of lead dampers and earthquake-protection devices at Mitsubhishi Materials Corporation and Fukuoka University in Japan 1375-3781. Much of the information on the use of lead in earthquake-protection devices is a result of this effort.

B. Design of Base-Isolated Buildings In the design of structures, structural engineers always consider the various external forces on the building, such as earthquakes and typhoons. The anticipated level of external forces is difficult to decide, but it is common now to use a maximum velocity of 50 cmls (or level 2 ) for earthquake tremors

460

Chapter 4

as a likely basis. For design involving critical structures,surveys on past earthquakes and dislocation earthquakes are used to calculate the likely forces to be expected from earthquake tremors. In Japan and other earthquake-proneareas, it is very important to consider the strength and characteristics of earthquake tremors and the buildings' response to earthquakes and to grasp the ultimate perfonnance of buildings in advance. In base-isolated buildings, isolator interfaces composed of isolators and dampers are installed in the lower story of the building to isolate it from ground excitation. It has been possible to accurately confirm the basic features and performance limits of isolators and dampers through laboratory experiments. Thus, it is possible to accurately determine from these results, the characteristics of vibration of base-isolated buildings due to the reliance of such buildings on the characteristics of the isolator interface. During earthquakes, the upper structure oscillates almost rigidly. The deformation of the building and ground acceleration are extremely small and the deformation of the structure is reduced to within the range of elasticity. Because of the reliance on base isolators, uncertainty in the behavior of foundations is reduced. The response behavior of base-isolated buildings during an earthquake can be measured with a high degree of precision, which also allows one to verify earthquake observation results to date. That their probable behavior during an earthquake can be predicted is indeed what makes baseisolated buildings unique structures. Base-isolation systems using rubber include those systems ( I ) where lead plugs are pressed into the core of laminated rubber where the functions of isolator and damper are integrated and (2) where rubber laminate isolators and lead dampers are not integrated. The response of base-isolated buildings during earthquakes is controlled to a large extent by the characteristics of the isolators (period characteristics) and dampers (damping amounts). In the design and selection of isolation members, it is necessary to carry out stringent engineering tests on the ultimate performance limits and characteristics of a structure.

C. Lead Dampers The lead dampers used are made from pure lead that has the advantages of being corrosion resistant and having superior plastic deformation and crystallization ability. Thedeformable section could have different shapes. In order to improve the characteristic of the force-displacement relationship, four different damper shapes have been evaluated under an ILZRO program: I-shaped (hourglass), C type, J type, and U type. Nomenclature used to refer to the lead dampers is of the form A-nn where A refers to the type and nn refers to diameter in mm. For example, C75 refers to a C-type damper of 75 mm diameter. Sketches of the four types of dampers are shown in Figure

Applications of Lead

461

Steel plate

Steel plate

I - Type

Steel plate

C - Type

Steel plate

Steel plate J - Type

U - Type

Figure 13 Profiles of l-type, C-type, J-type, and U-type dampers 13771.

13 [377]. Earthquake simulation test equipment was used toevaluate the performance of the dampers. The schematic and the actual test equipment are shown in Figs. 14a and 14b, respectively 1375,3771. Specimens were attached to upper and lower H-shape angles by high-tension fasteners. Various wave-pattern forces were applied to specimens by sliding the upper movable angle. Forces were applied in two directions, parallel to the bending plane of the specimens (P direction) and orthogonal to the plane (0 direction), to investigate the force versus displacement hysteresis loop changes depending on the directions. In the case of Fig. 14, the direction of applied force is the P direction. For testing in the 0 direction, the same H-shape angles as shown in Fig. 14 are used, but the specimen orientation is rotated by 90" about the y direction (vertical). Applied forces were measured with actuator load cells and the displacements were measured with linear voltage differential-transformer-type gauges (LVDT). The I-shaped and U-type dampers showed the same yield strength in both directions, whereas the C and J types showed different strengths. The areas of hysteresis loops were plotted versus damper diameter for each type and showed the highest areas (greatest damping) for the C type, followed by the J and U types. The hysteresis area was related to the third or fourth power of the damper diameter, meaning that small diameter adjustments give large changes in damping. The I type has lower damping because a greater proportion of its deformation is tensile strain rather than shear strain.

D. Performance

of U-Type Dampers

There are many U-type lead dampers in use today. There has been a steady increase in the scale,size, and capacity in the use of these U-type lead dampers in base-isolated buildings. The largest U-type lead damper in use, the U 180, has a shaft diameter of 180 mm. Itis possible to shape lead dampers quite freely by gravity die casting and it is also quite straightforward to develop lead dampersappropriate to the particular properties of

462

Chapter 4

Figure 14 Earthquake simulation test equipmentfor the evaluationof the dampers. (a) Schematic and (b) actual test equipment t375.3771.

base-isolated buildings.The challenge one faces today is to begin to develop even larger lead dampers. Dynamic tests using an actual-size Ul80-type damper and a one-quarter size model have confirmed the basic capabilities of dampers, including ultimate deformation, energy dissipation capabilities, and yield strength. Figures 15a and 15b show a schematic indicating the dimensions of the U180type damper and an actual U180-type lead damper [376]. Table 4 gives the specifications of different U-type lead dampers [376]. The lead damper is strengthened at those sections where it is most weak, namelythe deformable section, where the damper has been bent into a U-shaped curve (diameter

463

Applications of Lead Attached flange

-

I Actualsize test plece

Model test plece

(W

Figure 15 (a) A schematic diagram of a U180-type lead damper and (b) an actual size damper [376].

Chapter 4

464

Table 4

Main Specifications for U-Type Lead Dampers [376]

Name of test piece

Diameter of deformable section 10 (mm)]

Height of deformable section [ H (mm)]

Length of deformable section [ L (mm)]

50 75 100

550 560 560 560 560

680 73 0 700 638 660

U50 type U75 type U 100 type U 140 type U180 type

140

180

"Calculated values.

180 mm) and at both ends, where the diameter is at its greatest. The maximum diameter of the strengthened sections at the ends of the damper is 360 mm, or twice that of the deformable section. The strengthened sections and flanges are homogeneously bonded and the deformable and reinforced sections are cast together using a special mold. Lead of purity higher than 99.99% is used, and by the virtue of lead being extremely malleable and able to recrystallize even at extremely low temperatures, its repeated deformation capacity is extremely high. For the evaluations of the dampers, both static and dynamic tests have been carried out on the actual size damper. Sine waves were used for applying vibrations in the dynamic testing. For the application of large-deformation vibrations, an actuator able to apply vibrations (load of +50 tons and a displacement of ? 150 mm) was used. The standards for the deformation offset were set at 0 mm, 200 mm, or 400 mm and the amplitude of the vibrations were -1-50 mm. The vibration period was 3 S. In the static tests, monotonic loading from one direction with a displacement of up to 700 mm was used. The loading speed was approximately 1 mm/s. Figures 16a and 16b show the load versus displacement curves of an actual size damper tested in the P and 0 directions, respectively 13751. Both static and dynamic test results are shown in these figures. During an earthquake, there will be repeated dynamic forces and, thus, a need to experimentally prove to what degree the damper can withstand repeated deformation. Figures 17a and 17b show deformation caused by the dynamic tests in the P direction after 30 and 135 cycles, respectively, for a deformation amplitude of 150 mm [376]. Energy dissipated as a function of accumulated plastic deformation is shown in Fig. I 8 13761. The deformation of the lead damper depends on the loading frequency and amplitude, as the yield strength varies with cyclic loading frequency and amplitude of vibration (Figs. 19a and 19b, respectively) 13761.

465

Applications of Lead

.;............... Static

................... .i.....................

................... i......................

......................

J

................

.......... ......

.................

E

.......... ......

-2 0

.................

.................................... 79cyclcs ,

,

I

I

,

I

,

0

I

I

200

,

,

400

I

L

i 600

Lateral displacement (mm)

(4 ..........................................

I .................

................... :...................... D y n m c ics1

:..................

..,........

x

...........

-0 1 0 : . m 0

7L5

............

0 L.

..,........ 91cyc1cs

...........

.................. {.-.- ............ 1oocyc I oocyc I es 1

"

'

1

0

"

1

'

'

1

'

200

1

1

400

600

Lateral displacement (mm)

(b)

Figure 16 Load-displacement curves of an actual size U180 damper in (a) the P direction and (b) the 0 direction [375].

In the scale-up of dampers, the law of similitude as shown in the Table 5 are used [376]. However, one must bear in mind that the generation of heat arising from repeated deformation will have an influence on the properties of lead.

E.

Energy DissipationCapability

The damper must ultimately dissipate all of the input energy brought about by an earthquake. The total energy input can be expressed as E = M(V,)'/

Chapter 4

466

l

(W

Flgure 17 Deformation in the U180 damper by the dynamic tests in the P direction after (a) 30 cycles and (b) 135 cycles [375].

Applications of Lead

467

Pdircctit~ll.2 0 c m ~ I I I S C I , 11x1 limes Pdirucllotl. W c ~ n t ) ~ r s c ~79 . II~IC)

...................

.._

Amount of accumulated plastic deformation (cm)

Figure 18 Encrgy dissipated uctunl size test pieces 13761.

;IS

a function of accumulated plastic tleformation

of

2, where the equivalent velocity is V,
where a, is equivalent to the damper's total yield shear Coefficient, >8,>is the amount of accumulated plastic deformation, and g is gravitational acceleration. The relationship between the equivalent velocity corresponding to energy input and the accumulated plastic deformation, from a condition of equilibrium, can be determined using [376]

The damper's yield shear coefficient a',"'when the isolation interface's base shear coefficient is at its lowest level can be determined using the following equation which is obtained from the response prediction method based on the energy balance [376]:

468

Chapter 4

-10

m Y o 0 0

81

...........

-

0.0

0.4 0.6 0.8 1.0 Frequency (Hz) 0 P direction: Parallel to bending plane of specimen A 0 direction: Orthogonal to the plane

0.2

(a) h

210 0 0

z

Amplitude of vibration applied for U 180-type (mm)

(b)

Figure 19 Dependence of yicld strength on(a) frequency and (b) amplitude of loading 13761.

Table 5 Laws of Similitude Used in the Scale-up of Lead Dampers (Scaling Factor = A) [376] Physical properties

Model

Actual

Applications of Lead

469

Here, T, is the period of the base-isolated building based solely on the lateral rigidity of the isolator. When c y , is substituted in Eq. (14). one obtains

When T, = 3-4 S and V , = 150-300 cm/s, the amount of accumulated plastic deformation equals 150-420 cm. Lead dampers are easily able to withstand accumulated plastic deformation over and above S000 cm. On the other hand, the amount of energy that a single damper has to dissipate. W,,,, can be determined using the following formula, where nl is equivalent to the mass of the building per damper 1376):

According to this, 111 = \Q>/(cxY'"g) where ,Qv is equal to the yield strength of each damper. Typical values of W,,, = (1.7-2.5) X 10" kg cm when = 3-4 S. V,<= 150-300 cm/s, and ,Q,. = 8 tons. With a deformation of the damper of 30-40 cm and 20 repetitions, the average value of energy dissipation is 1.6 X IO" kg cm. Accordingly, the total energydissipation amount is 32 X IO" kg cm. Such a value is more 10 times higher than the energy-dissipating ability sought from individual dampers.Thus,onecan see that there is already a sufficient and additional dissipating ability i n the dampers. The tensile strength of lead changes with the speed of deformation. Within acompressivedeformation speed (strainrate) of 0.4-31 I S " and within atemperaturerange of 22-3OO0C, therelationship between yield stress and deformation speed E is given by U?

In this case, a,,and 17 are constants dependent on the amount of strain and the temperature, and the value of 17 is somewhere between 0.04 (E = 0.1, 220°C) and 0.26 (E = 0.5, 300°C). The lead damper's yield strength, ,Q,, relies on both displacement and displacement rate: ,Qv = n7(kSf)" = K ( 6 f ) "

(19)

where k is a constant, 6 is the amplitude of the applied vibration, ,f is the

470

Chapter 4

frequency in Hz, and K = m k " . Note that the term yirld strength as referenced here actually refers to the load at yield for the damper and the units are in tons. The yield strength ,$Q,also depends o n the diameter of the damper, D. The maximum yield strength of the lead damper Q\. can be given by

where M,, is the plastic's moment (= Z,pv),Z,, is the plastic's section modulus (= 0'/6), D is the diameter of the deformable section, H is the height of the deformable section, and uvis the yield stress of lead materials 13761.

F. Buildings Employing Base-IsolationSystems The Building Center of Japan (BCJ) has recorded 57 buildings as having base-isolation systems between 1983 and 1991. Of these, 45% are offices, company housing, and experimental centers dedicated to the research of base isolation. Since the Great Hanshin Earthquake at Kobe, Japan in 1995, the number of such buildings has increased tremendously, and by November 1996, it was estimated that approximately 200 such buildings existed in Japan. The dramatic increase in base-isolated buildings is intrinsically linked to the experiences in the Northridge (Los Angeles, CA) and Great Hanshin earthquakes, where the performance of such buildings and the limited damage to fittings and furnishings within them during the earthquakes was witnessed first hand. Consequently, it is anticipated that public housing, hospitals, computer centers, emergency services, and government and municipal offices thatneed to function during emergencies such as earthquakes will be retrofitted on a massive scale using base-isolation systems. Table 6 lists some of the base-isolated buildings in Japan that use lead in its base-isolation system [37X]. Figure 20 shows the City Hall building in downtown Salt Lake City that has lead i n its base-isolation system.

1. Observed Behavior of Base-Isolated Buildings During Earthquakes The actual performance of base-isolated buildings during the Northridge (January 17, 1994), and the Great Hanshin (January 17, 1995) earthquakes have been evaluated. A brief description of the results is presented in this section [376].

Northridge Earthquake. During the Northridge Earthquake (Los Angeles, CA, U.S.A,) on January 17,1994, a maximum ground acceleration exceeding 1G was observed. The highest acceleration recorded was in a free-

Table 6

Some of the Base-Isolated Buildings in Japan that Use Lead in Its Base-Isolation System [378]

Name of building

s

Year of design

Note 1

Uses

Chiba

1988

RC + 2

Apartment

NI 435

HD

Kanagawa

1989

RC +3

House

NI 500

HD+LD

Tokyo

1989

RC + 6

NI 600-700

LD+FD

Ibaragi Kan aga w a

1990 1990

RC +4 RC +4

Oftice, computer room Laboratory Dormitory

NI 500-600 NI 500-600

LD LD

Tokyo

1990

S +6

NI 800

HD+LD

Kanagawa

1991

RC +3

Oftice, computer room Laboratory

NI

LD

Location

Note 2

Note 3

Note 4

+

*

r

P

Konoike-Gumi, Ichikawa Isolation Hasekou Corp., test housing C.P. Fukuzumi P.N.C. Info. Center Dainihon-doboku, Ichigao Dormitory ENICOM Computer Center Fujita Corp. Tech. Lab. No. 6 Red

Norrs ; I . RC = reinforced concrete structure: S = steel structure: + = number of stories above ground. 2. N I = natural rubber insulator: numbers are diameter (in cm). 3 . HD = steel hysteresis damper: LD = lead damper: FD = friction damper. 3. Asterisk indicates that i t was built for the company's own use.

LD

*

*

*

472

Chapter 4

Figure 20 City Hall building in downtown Salt Lake City that has lead in its baseisolation system. (Courtesy of Salt Lake City Corporation.)

surface area, Tarzana, approximately7 km from the center of the earthquake. Recordings show a peak horizontal acceleration of 1.8 G , and a vertical acceleration of 1.O G . The recordings of these high accelerations were made at the surface of the earth where actually the force of the earthquake was mitigated due to the interactive effect between buildings and their foundations, making it hard to imagine the impact of the earthquake without this interaction. The accelerations observed were themselves very significant but so too is a comparison of the horizontal and vertical components of the earthquake acceleration and the fact that the vertical acceleration did not exceed the horizontal acceleration. A base-isolated building in thearea of the Northridge Earthquake, USC Hospital, performed remarkably well during the earthquake. The hospital wasaneight-storybuildingwith one story below ground level.Table 7 compares its maximum response acceleration with that of a traditional sixstory building in the same area [376]. The acceleration values were provided by CSMIP (California Strong Motion Instrument Program). The horizontal acceleration on the roof of the conventional earthquakeresistant building was twice the amplitude of the acceleration on the roof of the base-isolated building. The horizontal acceleration of the base-isolated building, above ground level, was also one-half to one-third lower than in

Table 7

Measured Acceleration in a Traditional and Base-Isolated Structure During the Northridge Earthquake [376]

Name of building

Distance from earthquake’s epicenter

~~

Sylrnar Olive View Hospital (traditional structure) Los Angeles USC Hospital (base-isolated structure)

Free surface ~

15 krn 36 km

Horizontal 0.91 G Vertical 0.6 G Horizontal 0.49 G Vertical 0.12 G

Foundations

Superstructure

~ _ _ _ _

Horizontal 0.82 G Vertical 0.34 G Horizontal 0.37 G Vertical 0.09 G

Horizontal 2.31 G (roof) Vertical G data not available Horizontal 0.21 G (roof) Vertical 0.13 G

Chapter 4

474

the conventionalearthquake-resistantstructure.Whenconsidering the stability of structures during earthquakes, the base isolator's horizontal, rather than vertical, deformation performance is much more important. The base isolators could reduce the horizontal acceleration to manageable levels. G t m t Hcrrlshitl Earthcprcrko. Acceleration recordings during the earthquake were made at two base-isolated buildings based in the north ward (Kita-ku) of Kobe City, approximately 35 km from the center of the Great Hanshin Earthquake on January 17, 1995. The two buildings were the West Japan Computer Center of the Ministry of Posts and Telecommunications (West Building) and Matsumura Group Technical Research Center (Matsumum Building). A comparison of the peak accelerations recorded are shown in Table 8 [376]. The building with lead-rubber bearings and steel dampers (West Building)performed better than the one with high-dampingrubber bearings (Matsumura Building). Also, to investigate the stability of base-isolated buildings during major earthquakes, the response of base-isolated buildings to earthquake tremors exerting a force directlybeneath them based on the recordings from the Northridge and Great Hanshin Earthquakes have been analyzed. Simulation of the response of the base-isolated structures to the major Northridge and Great Hanshin earthquakes using a single-degree-of-freedom model, showed the buildings response is adequate to withstand the earthquakes. Figure 21 shows the input energy, absorbed energy, and kinematic energy as a function of time during the earthquake in the West Building [376]. The figure clearly shows that most of the input energy is absorbed in the isolation interface. Figures 22a and 22b show the maximum acceleration response and maximum displacement of isolation interface, respectively, as a function of the period of the base-isolated building showing a very effective damping performance [376]. The unit gal is an acceleration unit used in seismic engi-

Table 8

Maximum Acceleration Recorded Ncar the Kobe Earthquake 13761

Name of earthquake Great Hanshin

Vertical Lateral Lateral componentscomponentscomponents Point of measurement ( E W (UD) (NS) Kobe Marine Meteorological Observatory Top floor of West Bldg. (28.5 m high) Top floor of Matsumura Bldg. ( 12.5 m high)

Norr: 1 gal = IO-' m/s'.

617.3 gal

818.0 gal

332.2 gal

103 gal

7s gal

377 gal

273 gal

198 gal

334 g d

Applications of Lead

475

I"

-E 0

Ve = 92 2 cmis (=42EIM)

. . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

0 r

...............................................

10

20

30

Time (sec)

Figure 21 The input energy. absorbcd energy, and kinematic energy a s a function of time during the enrthqunke in the West Building, in Kobe. Jap;un [3761.

neering in honor of Galileo andis equal to 10 m/s2. In this unit, the acceleration due to gravity, 1 G. is 981 gal. Past evaluations of the cost performance of base-isolated buildings have been examined and the need to properly evaluate cost in relation to earthquake resistance capability is demonstrated. The cost of the building isolation interface a s a function of base shear coefficient is shown in Fig.

40

1

v

1

2

3

4

S

6

Figure 22 The maximumaccelerationresponse(a)andmaximumdisplaccmcnt of isolation interface (b) as a function of the period 13761.

476

Chapter 4

1.20 I

0. RC structure, rigid wall frame, medlum size A S structure, medium size n - SRC structure. multistoried bulldlna IO S structure, super mullistorled builiing

c ._

I!

‘5 1.05

m

I

:

a,

m a,

0.95

t

Building MSIS= 0 48014 C, + O 91749 CoeHiclenl of correlallon = 0 99239 l . . . .

O.gQo5”

0.2 - 0

6

Base Shear Coefficient

Figure 23 Thecost of the building isolationinterface sheor coefficient [ 3761.

as a function of the base

23 13761. A conceptual chart of optimization of earthquake protection costs and value is presented in Fig. 24 13761. Current efforts are directed at fully comprehending the characteristics of lead dampers and developing new types of lead damper.

111.

USE OF LEAD IN BRICK WALL INFILLS

Infilled frame structures consist of steel framework in which bricks and mortar are used to fill the empty spaces of the frame, typically one-story high. The steel structurals provide elastic resistance to swaying during wind loading and other shocks, and the bricks and mortar provide stiffness and improve compressivestrength. For an infilled frame structure to operate efficiently with regard to resisting racking loading, the infill must be a tight fit within the frame. After long periods of time, the steel framing can creep under the dead-weight loading, transferring load to the bricks and mortar, resulting in cracking ofthe latter. This reduces stiffness and consequent building strength. A layer of lead suitably encased in a protective polymer cover is placed between the bricks and the horizontal steel beams could accommodate creep of the frame while still maintaining elastic properties that could accommodate swaying during wind loading. For this to occur, the lead has to behave in a viscoelastic manner; deforming elastically when the structure is subjected to short-term wind or seismic loading while creeping to accommodate the shortening of the columns. Precautionary measures are

477

Applications of Lead

C, : Initial construction costs Cr Damage and loss at time of earthquake

Optimum value Earthquake loads for design purposes

Figure 24 Conceptual chart of optimization of earthquakeprotectioncosts value 17761.

and

warranted, as lead must be isolated using protective barrier layers to prevent undesirable interaction between lead and mortar. The feasibility of such an approach has been demonstrated at the University of Sussex,where an intill structure with and without a lead layer were examinedexperimentallyaswellasusing finite elementanalysis 1228,3791. The Pb alloy with a suitable viscoelastic property was identified afterextensivecreepmeasurements in the temperaturerange0-60°C on candidate Pb-Cu, Pb-Te, Pb-Sb, Pb-Cu-Te alloys.Overall,theresults clearly indicated that the Pb-0.06 Cu-0.04 Te alloy was theoretically the best alloy to use in infilled frame structures. Consequently, this was the alloy used when infilled frames were constructed and tested. Half-scale infilled frames containing a profiled layer of copper-tellurium-lead alloy was subjected to creep loading by progressive shortening of the columnlength. The load transmitted to the infill asa result of a shortened column is shown in Fig. 25 for infill without lead and two infills with a layer of lead between the infill and the bottom of the top beam [379). The results demonstrated that a lead layer does significantly reduce the load transferred onto the infill. After the creep loading tests, the infilled frames were subjected to swaying or racking loading typical of wind loading, and the response of the frame measured. Figure 26 shows the infilled frame in the test apparatus used in this evaluation [228]. In this racking loading, the maximum load was increased each cycle until complete failure of the infill occurred. The results from thesetestsshowed that a lead layer could be included in an infilled frame without the racking stiffness or strength of the frame being adversely affected.

Chapter 4

478 60

T

Shortenin0 of columns

Columns batno shortened daily

50

40

0.0125mm/day

B -m S

9

"-c lnfilled frame

mm lead

0.01 25mmld.y

30

d-infilled frame whh lead

20

10

0

150

100 0

200

50

Time (Days)

Figure 25 The load transmitted to the infill as a result of a shortened column for the cases of infill frame 1 without lead and infill with a layer of lead (frames 2 and 3). The creep rates of the structure are indicated for each frame [379].

Figure 26 Racking loading setup for the evaluation

of an infill structure [228].

479

Applications of Lead 60

50

40

20

10

0 0

20

40

60

80

Time (Days) Figure 27 Lond generated on the intill with and without a leadlayer In the cnse where a higher grade mortar is used [379].

The creep behavior of the profiled lead layers and the overall behavior of the infilled frames could be accurately predicted by nonlinear FEM anal-

ysis using ANSYS codes using experimental creep data on the lead alloy. Finite element analyses were used to predict the expected behavior of the infilled framesconstructed using a highergrade of mortar. Theanalysis showed that the load generated by the shortening of the columns would have more than doubled in the infill without a lead layer, whereas the load generated i n the infill with a lead layer would have changed very little (Fig. 27) [3791. This indicates that if infilled framesareconstructed with high strength inflls, as would normally be expected, a profiled layer of Pb-CuTe alloy would be very effective in reducing the load transferred onto the intill as a result of creep in the columns.

IV.

LEAD-TIN ALLOYS IN ORGAN PIPES

Organ pipes are typically made from a few traditional materials that include wood, zinc, and lead-tin alloy. The choice of material is related to the tone

Chapter 4

480

of the note requiredfrom the pipeand also occasionally to the wealth, generosity, or otherwise of the purchaser or benefactor. The use of Pb-Sn alloys for organ-pipe production arises due to the unique acoustic properties of these alloys and the microstructural condition. In the last hundred years or more, lead-tin alloy pipes for organs have been made with as high a composition as 85 wt.% lead and 15 wt.% tin. However, the organ trade had the viewthatnoalloy for organ pipes contain less than 25% Sn, and in really good work noalloy with less than 55% tin should be employed [380]. The process of manufacturing lead alloy sheets for organ-pipe production has not changed in the last 200 years [380]. In this process, the heated moltenmetal,typicallyanalloy of 50% lead-50% tin, ispoured into a wooden trough which can slide along a flat horizontal table, from one end to the other (Fig. 28) [380]. As the trough is pulled along the table, the moltenmetal contained initflows out from a thin horizontal slit at the bottom of the backof the trough. Thus, a thin sheet of moltenalloyis delivered to the table. The molten sheet retains a uniform thinness over the table surface due in part to a combination of such factors as the surface material onto which the metal has been cast, the temperature it has been cast at, and also the poor wettability in general of molten lead-tin alloys. As the molten alloy begins to solidify, a surface texture comparable to a mottled, spotty skin of a crocodile is formed (Fig. 29) [380]. The average size of the spots is about 15 mm. Not surprisingly, this spotty patterning of the solidified sheet is what gives the high-quality 50% lead-50% tin organpipe alloy the name “spotty metal.”

,

,I

;

I

I - \

\

\

Figure 28 Production of a spotty metalsheet [380]. (Courtesy of Lead Development Association, London.)

Applications of Lead

481

Figure 29 The spotty surface of a 50% Iead-50% tin alloy (the average spot size is about 15 mm and is visible tothenaked eye) [380]. (Courtesy of Lead Development Association, London.)

From the Pb-Sn binary phase diagram, the room-temperature microstructure is expected to consist of a 25% proeutectic phase and a 75% eutectic two-phase matrix. Indeed, this is more or less exactly the microstructure that is observed. However, the origin of the distinctive large surface spots that are formed as the alloy cools is still not clear. The formation of spots in spotty metal appears to depend on sheet thickness and alloycomposition. If a sheet of solid spotty metal having wellformed spots is placed on a metal hot plate, heated to about 200-300°C, and then left to cool slowly, the molten alloy solidifies surprisingly without the formation of any surface spots. If, on the other hand, the hot plate supporting the molten sheet is rapidly cooled, the spots once more appear on the surface of the solidified sheet. As the alloy composition moves away from the lead-tin eutectic composition, the formation of spots becomes increasingly rare. In the 70% lead-30% tin alloy a coarse dendritic surface structure is formed, instead of spots. Wonderful examples ofspotty metal pipes can be seen in organs throughout the world. One of the largest examples to be seen is the pipe organ in the Tabernacle at Temple Square, Salt Lake City, Utah (Fig. 30). At the other end of the scale, high-quality pipes no more than 200 mm long and 10 mm wide will also exhibit their spotty nature. Unfortunately, many ofthe front pipes of the famous organs throughout the world are made of smoothed metal, often lead-tin or zinc alloys that may have been planed to produce a smooth finish in readiness for the ap-

482

Chapter 4

Figure 30 ThepipeorganintheTabernacle at TempleSquare,SaltLakeCity, Utah. (Courtesy of the Church of Jesus Christ of Latter-Day Saints, Salt Lake City, Utah.)

plication of gilding or other design motifs. However, hidden behind these plain metal fronts, one can glimpse the hidden ranks of row upon row of spotty metal pipes. For example, a typical organ in a reasonably large church may have approximately 60-100 pipes visible on the organ front. Such an organ, however, maycontain as many as 3000 to 4000 more individual pipes hidden out of sight, behind the normallysymmetrical front pipework [380]. Generally, a complete church organ is described in terms of a number of subdivisions of the separate organs that comprise the whole. Thus, a large church organ may contain subdivisions such as a great organ, a choir organ, a swell organ, and echo and solo organs. In turn, each of these separate organs contains a selection of so-called stops made up of a collection of individual pipes. Each stop very loosely represents a type of orchestral in-

Applications of Lead

483

strument sound, andan average stop comprises about 64 pipes. There is steadydemand for lead alloy for this application, as there is a constant demand of organs for new buildings and renovation of old organs.

V.

USE OF LEAD SHEETS IN ARCHITECTURE

One of the important applications of lead is as a building material. The use of lead sheet in buildings for roofing, flashings, building facings, and waterproofing dates back to the earliest days of recorded history. The Greeks, Romans, Turks, and the people of modem Europe have found lead sheet indispensable for long-lived roofing applications. The Hanging Gardens of Babylon in the 9th century B.c., a roof garden, had an underlying structure that was waterproofed with layers of asphalt and sheet lead to preserve the scarce rainfall. From the magnificent and historic Hagia Sophia in Istanbul (Fig. 31) to the modern House of Bluesm in Chicago (Fig. 32), lead has been used as a roofing and siding material [381]. Thousands of cathedrals, homes, courthouses, libraries, and universities all over the world have lead roofs that are virtually maintenance-free and have lasted hundreds of years. The Pantheon in Rome has a lead roof that is over 700 years old (Fig.33) [381]. Anotherexample of a beautiful historic structure is the Amiens CathedralSpire in France that dates back to the 16th century (Fig. 34) [382,383]. St. Paul’s Cathedral, London with a stunning lead dome modeled after St. Peter’s is over 290 years old (Fig. 35) [381]. One of many medieval cathedrals that depend on long-lasting lead as their

Figure 31 The magnificent and historic Hagia Sophia in Istanbul, with decorative lead covering [381]. (Courtesy of Mayfield Manufacturing Company, Birmingham, AL.)

484

Chapter 4

Figure 32 The modem House of Blue@ in Chicago, with lead covering [381]. (Courtesy of Mayfield Manufacturing Company, Birmingham, AL.)

first line of defense against water is the Canterbury Cathedral in England. Thomas Jefferson's home in Monticello, Virginia(Fig. 36) [381] andSt. Mary's Chapel at Washington National Cathedral have lead roofs. Today, lead sheet is used both in the preservation of historic buildings and in the construction of modem structures. Lead's appeal to architects, engineers, and builders for these purposes largely arises from its great durability, ease of installation, and the fact that it does not cause unsightly stains or discoloration on adjacent materials. Its pleasing gray color blends well with any color scheme. Lead's long life makes its ultimate cost extremelylow. It has beenmentioned that protection from cosmic rays is another reason in the choice of lead roofing in some of the expensive homes today. The new Inland Revenue Centre in Nottingham, England (Fig. 37)

Figure 33 The Pantheon in Rome, which has a lead roof that is over 700 years old [381]. (Courtesy of Mayfield Manufacturing Company, Birmingham, AL.)

Applications of Lead

485

I

Figure 34 Amiens Cathedral Spire in France that dates back to the sixteenth century. (Courtesy of Lead Development Association, London.)

has used over 600 tons of lead in8860 roof panels prefabricated ina factory under controlled conditions. Weighing as little as 7.5 lbs/ft2, lead offers an extremely effective life-cycle cost [381]. Lead sheets are frequently used in waterproofing modem large office buildings for the protection of underground installations that may include plazas or other rentable areas beneath landscape plots, reflecting pools, fountains, or planter boxes. Waterproofingis done by the use of a “membrane,” which includes builtup or laminated coverings made up of large unbroken surfaces, providing continuous integrity of the barrier for watertightness. Fusion-welded joints of lead sheets used to form the membrane are made by “lead burning” or by friction-stir welding of lead sheets. Lead specified

486

Chapter4

Figure 35 St. Paul’s Cathedral, London [381]. (Courtesy of Mayfield Manufacturing Company, Birmingham, AL.)

for a waterproofing membrane should be 3/32 or 1/8 in. thick, and in less demanding service, 1/164n. lead sheets are used. One of the prominent andlargest applications of lead for waterproofing purposes is New York City’s massive World Trade Center (Fig. 38) [385]. Approximately 700,000 lbs of lead sheets were installed in critical areas around the huge center for moisture protection. Most of the lead was installed in the World Trade Center Plaza, a huge 5-acre elevated platform that surrounds the center’s building complex and covers hundreds of underground shops and actively used space. Lead wasalso used on the plaza level to line 26 huge landscaping planters used as flashing around the base of buildings facing the plaza’s center court, to waterproof the center court’s

Figure 36 Monticello home of Thomas Jefferson [381]. (Courtesy of Mayfield Manufacturing Company, Birmingham, AL.)

Applications of Lead

407

Figure 37 The new Inland Revenue Centre in Nottingham, England, with a leadpanel-covered roof [381]. (Courtesy of Lead Sheet Association, UK.)

huge water fountain, to line 30 planters at street level, and to waterproof exterior stairways leading from street level to the plaza and from the plaza to the center’s concourse level. Lead’s corrosion resistance, freedom from maintenance, and the fact that it provides for a trouble-free waterproofing membrane are the primary reasons why it was specified. There has been no water leakage in the lead-protected areas since the center was completed in 1974. Throughout the ages, stained-glass pieces such as a cathedral window have been held together by malleable lead cames, which can be relied upon to endure for centuries. Many of the glass colors themselves are created with lead. The best stemware is made from lead crystal. Lead is also used to create beautiful objects of art. The use of the lead sheet in Europe is quite popular among architects [386]. This is particularly true of the United Kingdom, where the use of sheet lead has increased beginning in the early 1980s. By far the greatest tonnage of architectural lead sheet used in the world is used in the United Kingdom. Of the total tonnage, 7-10% of lead sheets is used for the restoration of old and historic buildings. Lead roofing and cladding on new

488

Chapter 4

Figure 38 WorldTradeCenter building using extensive lead sheets for waterproofing water tanks, roofs, and planting pots in the plaza level and other sections of the building [385]. (Courtesy of Lead Industries Association, New York.)

buildings and additions to existing buildings probably accounts for about 15% of the lead sheet market. The standard material is copper-bearing lead, as specified in BS 1178. Sand-cast lead sheets are used in some restoration work. Cast decorative leadwork, a minor application, may also use Pb-Sb alloy. The main use of lead sheet in the United Kingdom, as with all European countries, is for flashings and weatherings. Lead is also widely used in the United Kingdom to dampproof courses in buildings. Many architects and designers have become disillusioned by the performance of alternatives to lead sheet, particularly for flashings, and have returned to the time-tested and proven long life of lead sheet. The ready availability of good quality lead sheet in convenient widths and lengths atbuildersupply merchants

Applications of Lead

489

throughout the United Kingdom has also led to the increased use of lead flashings.

A.

General Guidelines for the Use of Lead Sheet in Roofing

The guidelines for the use of lead sheet in building are now provided by the Lead Sheet Association (LSA), Tumbridge Wells, Kent, England. The LSA is now setting the standards for lead sheet use in buildings in Europe as well as North America. The Lead Sheet Mar~zralpublished in three volumes in 1993 now sets the standards and the guidelines on the installation of lead in sheet roofing and cladding, lead sheet flashings, and lead sheet weatherings [344]. Mayfield Manufacturing in Alabama, a member of LSA, now provides assistance in theuseof lead sheet in roofing in North America. Although it is impossible to condense this detailed information in a few pages of this book, an attempt is made to present some key information. The reader should consult the L e d Sheer Manual 13441 for further information.

1.

Lead Sheet Roofing and Cladding

Lead sheet for roofing, cladding, and gutter linings should conform to British Standard 1178 1982"Milled Lead Sheet for Building Purposes. Standard lead sheet sizes for roofings, claddings, gutter linings, flashings, and weatherings are shown in Tables 9 and 10. Sand-cast lead sheet is used in particular for replacing old cast-lead roofing and for ornamental leadwork. This material is still made by the traditional method of running molten lead over a bedof prepared sand. A relatively small amount of sand-cast sheets are

Table 9 BS 1 178 Codes and Thicknesses 13441. (Courtesy of Lead Sheet Association, UK.) Thickness Codes

( mm )

Weight (kg/n?)

1.32 I .8 2.24 2.65 3.15 3.55

14.97 20.4 1 25.4 30.0s 35.72 40.26

Use for

Color code

A, B, F B-H B-H C-E, G, H C, D, G, H

Green Blue Red Black White Orange

A

~~

Kcy to uses. A-soakers: B-flashings: C-flat rooting; D-parapet, box and tapered valley: E-pitched roofs; F-vertical cladding: G-dormers: H-bay roofs and canopies.

Chapter 4

490

Table 10 Standard Lead Sheet Sizes 13441. (Courtesy of Lead Sheet Association, UK.) For Flashings and Weatherings Width (mm)

Code 3 (3 m)

Code 3 (6 m)

9

18

150 200 250 300 350 400 450 600

Code 4

( 3 m) 9 12.5

IS 13.5

27

18.5 21.5 24.5 27.5 36.5

Code 4 (6 m)

Code 5 ( 3 m)

Code 5 (6 m )

18.5 24.5 30.5 36.5 43 49 55 73.5

11.5 15 19 23 26.5 30.5 34.5 45.5

23 30.5 38 45.5 53 61 68.5 91 .S

For Roofing, Cladding, and Gutter Linings ~~~

Dimensions

Code 4

Code 5

Code 6

~

Code 7 ~~~

6 m X 1.2 m 3 m X 2.4 m 6 m X 2.4 m 12 m X 2.4 m

I47 290 147 366 294

S88

183 257

183 290 732

216.5 257 216.5 433.5 867.0

~~

Code 8 ~

5 14.5 1029

579.5 1 IS9

produced. There is no British Standard for sand-cast lead sheet. Apart from surface texture and less consistency in the thickness, there are, for all practical purposes when the composition of the metal is similar, no significant differences between the properties and working of sand-cast sheet andof milled sheet. There is also now a comparatively new form oflead sheet made by continuous casting, which has physical properties, microstructure, and modes of failure different from either of the above. This should not be used where sand-cast lead has been specified. Lead-clad steel, which consists of lead roll-bonded to mild steel or stainless steel, is also available and this can beused to produce prefabricated panels that can be bolted to a steel substructure that are used to produce modern Mansford roofs and other products. Fixings for lead sheets are used to hold the lead securely and permanently in position and to prevent lifting and distortion in high-wind conditions (see Fig. 72 of Chapter 3 ) . Head fixings are those used to tix the top of a panel sheet to the substrate. Two rows of copper or austenitic stainlesssteel nails are used at a spacing of 75 mm and each row offset by 25 mm

Applications of Lead

491

to the left and 25 mm down. The top row is set at 25 mm from the edge. A single row with a 50-mm spacing is used if the height of the panel does not exceed 500 mm. Copper or stainless-steel nails are used for a timber substrate and screws are used for concrete/masonry. Fixing in joints use copper and stainless steel clips. Copper and stainless-steel clips are incorporated into joints to hold the leadwork in position and prevent the weatherings from lifting under wind pressure or suction. The use of a typical 50-mm-wide clip in a welt joint is shown in Fig. 39. The clip is fixed to the substrate using nails or screws. Similar clips are used in wood-cored roll, hollow-roll, and standing-seam joints. Spacing of the clips is normally between 300 mm and 450 mm, depending on the position and exposure of the weathering.

<

/

COPP stamless steel clip

v ,-Welt A

lightly dressed

Figure 39 The use of a typical 50-mm-wide clip in a welt joint. (Courtesy of Lead Sheet Association, UK.)

492

Chapter 4

Free edges of roofing and cladding must be clipped to prevent lifting and distortion. In positions exposed to very high wind pressure or suction, a continuous clip is recommended. This method of fixing can also be used where visible clips are aesthetically unacceptable. With all clips, the thickness used will depend on exposure.The minimum thickness is 0.6 mm copper or 0.38 mm stainless steel for moderate exposures; for higher exposures, 0.7 mm copper or 0.46 mm stainless steel is recommended. Lead clips should have a thickness not less than that of the leadwork, but for moderate to exposed positions, the thickness of the clips should be increased by one or two codes. The spacing of clips on free edges should be between 200 and 450 mm centers. Intermediate fixings between joints or free edges must not restrict free thermal movement of the lead, as this could cause the sheet to buckle, which, in turn, will result in fatigue cracking. Experience has shown that securing large pieces of lead with numerous intermediate fixings results in fatigue cracking. Therefore, the tendency today is to position the expansion joints so that intermediate fixings are not necessary. Soldered dot, lead button, or capped screw and washer are common types of intermediate fixings. Solder for making soldered fixing dots should be Grade D or Grade J, conforming to BS 219. Joints normally used with lead sheet roofing and cladding are roll, standing seam, welt, drip, and lap joints (see Fig. 51 of Chapter 3). Woodcored roll joints are suitable for flat roofing, pitched roofing, and also lead cladding. Hollow-roll joints can also be used for flat and low-pitched roofing but are more suitable for pitched roofs coverings where laps are used and there are few abutments or complicated joint intersections. Welt joints are used for steeply pitched roofs and wall cladding. Standing seams are only suitable for pitched roofs of 80" and above, where there is little chance of mechanical damage. Drip joints are used across the fall offlat and lowpitched roofs. Lap joints are used across the fall for all roofs over 10" and for vertical cladding. Table 1 I summarizes the maximum recommended sizes of sections, bays, and panels for roofing, cladding, and flashings. An underlay is used to isolate the leadwork from the substrate and allow the lead sheet to expand and contract freely with changes in temperature. Traditionally, an impregnated felt complying with BS 747 Type 4A No 2 has been used on boarded, concrete, and masonry surfaces. Building paper to BS 1521 Class A is a suitable underlay when the surface of the substrate is even and smooth (e.g.,plywood). Where there is any risk of condensation or moisture forming under leadwork, geotextile (nonwoven needle-punched polyester) overlay is recommended. This material will not rot if condensation does occasionally form under the lead and will also allow the air that circulates below the substrate to dry out moisture under the lead

Applications of Lead

more readily. Geotextile underlays should have a weight ofnot 2 10 gtm’.

2.

493

less than

Lead Sheet Weatherings

The architectural definition of the word “weathering” is “the giving of inclination to a surface to throw off water.” Because many of the surfaces themselves need protection to prevent water penetration, one definition of a lead sheet weathering is “a piece or pieces of lead sheet used to prevent water penetration intoasurface.” Lead weatherings are used to protect concrete, stone, and brick projections such as cornices and string courses, to weather the top of parapet and gable walls, and as the protective covering on door hoods, bay windows, porticos, and canopies. The coverings of dormer windows, cupolas, and turrets are often referred to as lead sheet weatherings. However, details of the joints used (e.g., rolls and drips), how they are made by bossing or lead welding, and detailing of the joints at eaves and abutments are the same as for roofing and cladding. Lead sheet for weatherings should conform to British Standard 1 178: 1982“Milled Lead Sheet for Building Purposes. Code 4-lead sheet is the minimum thickness to use for weatherings. The actual thickness will depend primarily on the size of the piece of lead sheet, application, allowances for bossing ordressing into deep profiles, vulnerability to wind lift, possible mechanical wear due to foot traffic (e.g., for access or maintenance), and the quality of the building. On most historic buildings, the thicker codes of lead sheet are normally specified. Joints normally used with lead sheet weatherings are rolls, welts, and lap joints. Wood-cored rolls are suitable for dormer tops, bay windows, door hoods, canopies, domes, cupolas, and turrets. Hollow rolls are suitable for canopies, domes, cupolas, and turrets. Welt joints are suitable for checks, cornices, and parapet tops. Lap joints are used for a minimum 75-mm vertical weathering. Head fixings, intermediate fixings, and fixing on free edges are similar to that for roofs and cladding. 3.

Lead Sheet Flashings

Flashing is a strip put over a junction to nuke it weather-tight and it has been a term associated with buildings since the 16th century. Lead sheet is indisputably the best material for flashings. It can be readily cut and fitted with simple hand tools and its extreme malleability makes it the ideal material for dressing over complicated shapes, particularly the multicurved contours of many roofing tiles. Lead sheet for flashings should conform to British Standard 1178:1982”Milled Lead Sheet for Building Purposes. For most flashing applications, codes 3, 4, and 5 lead sheets will be adequate.

P (D

P

Table 11 Maximum Recommended Sizes of Sections, Bays and Panels [344]. (Courtesy of Lead Sheet Association. UK.) BS 1 17.5 Code Number

Flat roofs 10" or less Maximum spacing of joint with the fall Maximum spacing of drips Pitched roofs 1 I" to 60" Maximum spacing of joint with the fall Maximum distance between laps Pitched roofs above 60" and up to 80" Maximum spacing of joints with the fall Maximum distance between laps Gutters-box or tapered Maximum spacing of drips Maximum overall girth

4

5

6

7

8

500 1500

600 2000

675 2250

675 2500

750 3000

500 1500

600 2000

675 2250

675 2400

750 2500

500 1500

600 2000

675 2250

675 2250

750 2250

9

PI

m1500 750

2000 800

2250 850

2500 900

3000 1000

p

Vertical cladding Maximum spacing of vertical joints Maximum distance between laps Soffits Up to 150 mm deep Up to 200 mm deep Up to SO0 mm deep Projections, cornices, and parapet cappings Not exceeding 450 mm wide nominal fall 450 mm to 650 mm wide with nominal fall Not exceeding 450 mm wide sloping up to 10" 450 mm to 650 mm wide. sloping up to 10" Flashings All flashings, weatherings. and pitched valleys (except for the verges of asphalt and felt roofs) Flashings to verges of asphalt and felt roofs Ridge roll cappings Hip roll cappings

D

'0

SO0 1so0

1000 750

so0

600 2000

600 2000

1200 1200 600

1200 1200 600

1so0 1so0 1 so0

2000

1000 I000 1000 1000

I so0

1so0 1 so0 1 so0

1SO0

1500

I so0

1000

1000 2000

1000 2000 I SO0

1SO0 1SO0

1 so0

N o t c : Oversizing may cause failure. Compare sizes with this chart. Values are given in millimeters.

650 2250

700 22.50

g, 0 3

2000 2000 1S o 0 1so0

Chapter 4

496

On important historic buildings or on positions of extremeexposure, the thicker codes are often specified. Additional thickness can also be required when bossing or dressing lead sheet over deeply profiled glazing bars or tiles. With all flashings, the most important factor toensure long life is length; therefore, for all individual flashing, it should not exceed 1.5 m. Joints between flashing pieces are usually laps. With abutment flashings, the laps should notbe less than 100 mm and less than 150 mm for locations that are exposed to high wind and rain. For secret gutters and pitched-valley gutter linings, the laps should conform to a vertical weathering height of not less than 75 mm. Abutment flashings to brick, block, and stonework are usually fixed into joints by lead wedges. These are simply strips of lead sheet 20-25 mm wide, folded several times to suit the thickness of the joint. The wedges are driven into the joints (with a hammer and plugging chisel) to hold the 25mm turn-in of the flashings securely and to a depth sufficient for the mortar pointing to conceal the wedges. Spacing should not exceed 450 mm. The free edge of a lead flashing must always be clipped with a spacing between 300 and S00 mm, depending on exposure. Polysulfide or neutral-cure silicone sealants are often used to seal the joint between lead sheet and other building materials. Silicone sealants can acconmodate greater movement than polysulfides. Compatibility with masonry and dpc material must be checked with the manufacturer. For building applications, experience has shown that lead sheet can beused in contact with another metal such as copper, zinc, iron, aluminum, and stainless steel without risk of significant bimetallic corrosion. There is, however, one important exception: whenlead and aluminum are used together in marine environments. In such locations, the chemical between lead oxide on the surface of lead sheet and the sodium chloride water creates a caustic runoff that attacks aluminum. As severe corrosion also occurs in crevices, the use of lead sheet in contact with aluminum in marine conditions isnot recommended. 4.

Corrosion of Lead Sheet

When exposed to weather, new lead sheet flashings may produce an initial, uneven white, nonadherent, basic carbonate on the surface.This can be aesthetically unacceptable in somesituations, but more importantly, the white carbonate may be washed off by rain and cause unsightly staining on materials below the flashings. To avoid staining and also provide a pleasing appearance,a coat of patination oil should be applied to the flashings as soon as practical after fixing. Preferably, the oil should be applied no later than the end of the day’s work, as overnight rain can cause the white stain

Applications of Lead

497

to develop. Patination oil should be applied evenly with a soft cloth, and. in vulnerable locations such as mansard flashings, fixed over dark gray slates or tiles; it is important to oil 1r17der.the loweredge of the flashings and between the laps. Clips along the edges of flashings should be turned over after the oil has been applied. This oil coating is designed to weather off after a few months, leaving a nonreactive, highly insoluble, stable patina on the lead. Dilute solutions of organic acids from hardwoods, particularly oak, can cause lead to be slowlycorroded.Thiscorrosioncan be exacerbated in situations where condensation forms below roofing and cladding and takes up acid from the substructure. Adequate ventilation and the use of a building paper underlay can control this problem, which is usually associated with old and historic buildings. Concretes and mortars made from Portland cement or lime can initiate a slow corrosive attack on lead in the presence of moisture. Direct contact between lead and new concrete or mortar should, therefore, be avoided in situations where drying out and carbonation of the free lime, by reaction with atmospheric carbon dioxide, is likely to be slow. When lead claddings, roof coverings, and weatherings are applied to concrete surfaces, a sealing coat of hard-drying bitumen paint on the concrete together with an underlay gives adequate protection during the drying out period. Slow corrosion of lead by dilute organic acids arising from the presence of lichen or mossgrowth on slated or tiled roofs is controlled by applying a solution to kill the moss growth when observed. Condensation on the underside of lead sheet can cause significant corrosion by converting the metal mainly to lead carbonate, but ventilation as per code should avoid such a situation.

5.

Fatigue and Creep of Lead Sheet in Roof

For a maximum temperature variation of 90- 100°C that may be expected in a roof, thermal expansion and contraction of a lead sheet that is 2 m long could be as much as 6 mm. If this cannot take place freely in a piece of lead sheet,distortion and cyclicstresses leading to fatiguecrackingcan occur. Recommendations on sizing and fixings fordifferentapplications should be followed to avoid such a situation. Thermal creep is minimized by appropriate sizing and fixings. Experience has shown that creep will not be a concern in external lead work if the pieces are sized to recommendations in the lead sheet manual.

B. Sheet Lead for Radon Shielding Radon comes from the radioactive decay of uranium. It is most often found in areas where the soils and rocks have high concentrations of granite, urd-

498

Chapter 4

niutn, shale, phosphate, and pitchblende. Although its presence in the air is commonplace, when the gas is trapped indoors it can build up to levels that are considered dangerous to humans. A safe, effective, and passive way of reducing radon concentration has been demonstrated by sheet-lead radon shield installed during the construction of a commercial building i n Butte, Montana and in two Florida homes 1387,3881. In this application, the property of lead that is utilized is not its well-known ability to protect against radiation, but the durability, flexibility, and impermeability of lead. Preconstruction testing in the Florida homes showed soil radon levels averaging 740 pico-Curies/liter (pC/L) at one location, and more than 70 pC/L at the other. I n both cases, the lead membrane shield reduced the indoor radon level to well below the EPA action level of 4 pC/L. In Butte, the preliminary tests indicated that radon levels in the area of the planned construction were up to 3200 pC/L. This was reduced to 4 pC/L. The old way of controlling radon would be to put i n a vent stack and operate a fan to pull the radon from under the concrete floor. The lead shield is meant to be a one-time, put-in-place barrier about which the owner will never have to worry. During construction, 120-cm-wide lead sheets were laidon the subslab fill. The lead sheets were overlapped 50-75 mm and caulked to seal any potential gaps. Despite the bitterly cold weather, the installation proceeded smoothly, with the pliable lead easily molding to the building’s contours. The lead was then coated, with an asphaltum compound to prevent it from chemically reacting with the concrete pad that was poured on top of it. The lead sheet creates a barrier through which practically nothing. not even the tiny molecules of radon gas, can pass.

C. The Sheet Lead Flat Roofing System The roofs i n most commercial buildings i n the United States are not pitched 0 1 - sloped but rather flat, and they require a flat, monolithic covering. On pitched roofs, lead is installed i n panels that are relatively small, about 14 ft’ in all, joined via loose-locked seams to allow for the required expansion and contraction. However, on a f lat roof, loose-lock seams simply would not provide the watertight seal that it is necessary. To address this expansion problem, LIA’s solution is to use a highly efficient insulation cover on top of the lead to eliminate significant temperature fluctuation 13871. The result is decades long durability and watertightness of lead sheet, combined with high-energy efficiency of polystyrene insulation. The Lead Industries Association and some of its member companies have installed three prototype roofs throughout United States to show-

Applications of Lead

499

case a trouble-free alternative to the built-up tar orsingle-ply-membrane, flat rooting systems in North America. In a typical installation, after the deck is swept clean, the sheet lead is hoisted to the roof by a forklift, then rolled out and flattened in place. Lead-burning the overlapped seams completed the membrane,converting the separate rolls into a single, continuous lead sheet. All of the projections or penetrations, such as vents, chimneys and drains, were sheathed with lead and burned (welded) right to the flat membrane lead. A layer of Dow’s Lightguard insulation’ boards, 3-in.-thick extruded polystyrene panels, were placed over the lead membrane to prevent large temperature fluctuations from reaching the membrane. Each insulation panel is extruded and has a tongue-and-groove configuration on its long sides, which interlocks the system on the roof, quickly and simply. With a life expectancy of a minimum of 40-50 years, the sheet lead flat roof is expected to find a niche in the high end of the single-ply marketplace.

VI.

LEAD IN RADIATION SHIELDING AND WASTE MANAGEMENT

The cost-effective shielding of gamma rays and x-rays provided by lead and some of its alloys make lead the first material to be considered in any design of gamma and x-ray radiation shielding. In Chapter 2, a detailed treatment of sources of radiation and the physical and nuclear properties of lead that make it a unique material in nuclear and x-ray shielding applications was provided. A more detailed treatment of the use of lead in radiation shielding in nuclear reactor facilities, in nuclear waste packages for underground facilities and in other industrial and medical applications is provided here.

A.

Use of Lead in Radiation Shielding in Nuclear Facilities

Nuclear reactors and reprocessing facilities have many different applications for lead shielding. Fixed or permanent shielding during initial construction, when space and weight are not critical, is commonly concrete and steel. When gamma shielding must be movable or removable, such as for ten+ porary repair and other activities, or where space is limited, lead is generally used, sometimes together with steel for structural purposes. Applications include such items as fuel charge-discharge machines, reactor room and hot-cell doors, shielding for piping and instruments, and shielding of turbines, walls, hot cells, and containers for handling and storage of exhausted resin beds. More than X0 tons of lead are used at Shoreham Nuclear Power

500

Chapter 4

Station ( S N P S ) on Long Island, NewYork, including 40 tons of interlocking lead brick, 12 tons of pipe sleeves, 15 tons of lead shot, 6 tons of lead wool, and various amountsof lead-burning bar and other items.The reactor vessel itself is lined with sheet lead. The brick was used to construct two floor-toceiling walls in high-radiation areas. The lead pipe sleeves encase 2-in. and 3-in. stainless-steel tubing carrying radioactive waste water. The wool and shot fill many small cavities and supplement the sheet lead lining the reactor vessel.Leadshieldingisinvaluableinnuclearcleanups,retrofitting,and repair in the Savannah River waste-treatment facility and other facilities. Hot cells, in which spent radioactive fuel elements or other radioactive materialsarehandledthroughremotehandlingequipmentandlead-glass viewing windows, are either concrete cells with manipulators and/or cells made from t a d bricks. Figure 40 shows an overview of a hot-cell facility [389]. Different brick shapes have been used. Interlocking V form (used in the 50-100-mm range) Fig. 41 [383] and the form such as the one shown in Fig. 10 in Chapter 3 are some of the typical shapes used. In general, the lead bricks are shaped in such a way that it provides a minimum thickness of lead shielding to the personnel from the hot material inside the cell. The

I

-4

Figure 40 An overview of a hot-cell facility [389]. (Courtesy of UKAEA, Harwell, and Lead Development Association, London.)

Applications of Lead

501

Figure 41 Lead brick with interlocking V form (used in the50-100-mmrange) [383]. (Courtesy of Mayfield Manufacturing Company, Birmingham, AL.)

casting of these bricks are done by gravity or pressure die casting. Figure 42 shows a 4-in. lead-brick shielding system [389]. On-site transporters for fuel or other radioactive material are shielded containersresembling casks, or truck-mountedtankswithup to several inches of lead shielding. The general features of a piece of equipment for transporting a fuel assembly and lowering it into a cask or a hot cell are showninFig. 43 [465].Undergroundpipingdependsprimarilyonearth shielding but may have a coverof lead sheet where shieldingis inadequate. Lead bricks are installed around stack monitors.Cranes and trucks handling radioactive materials may shield the cab with lead sheet. Lead shielding is also installed at the point of transfer of spent fuel from the reactor roomto the storage pool to protect personnel in the pool room until the fuel has enough water cover. The use of sheet lead shielding for so-called “portable” nuclear reactors for research and training reduces their weight to a minimum, as illustratedinFig. 44. Such shields arealsoemployed for waste-disposal containers. B.

Lead for Radioactive Transport and Storage Containers

As briefly mentioned in Section 6 of Chapter 2, the U.S. Department of Transportation and the Nuclear Regulatory Commission classify the types of shippingcontainer for radioactivematerial,whichrequireappreciable shielding as either Type A or Type B. (See 49CFR Parts 171 through 178 of the Department of Transportation, and lOCFR Part 71 of the Nuclear Regulatory Commission, 1973 IAEA Regulations (Safety Series No. 6) and with 1984 revisions with respect to design and operation of shipping con-

502

Chapter 4

4" Lead-Brick System

I . Standard Wall Brlck 2. Standard Base Brick 3. Standard Top Brick 4. Standard Corner Brick 5. Standard Corner Base Brick 6. Standard Corner Top Brick 7. Standard Half Top Brick 8. Standard Halt Wall Brick 9 . Standard Half Base Brick I0.Standard Reverse Corner Base Brick 11. Standard Reverse Corner W a l l Brick 12.Standard Reverse Corner Top Brick 13.Standard Quarter W a l l Brick 14. Flat Top Brick L. H. 15. FlatTop Brick R. H. 16. Flat Base Brick L.H. 17.Flat Base Brick R. H.

18. Flat W a l l Brick L.H. 19. Flat W a l l Brick R. H.

2O.Standard Aperture Brick 21. Standard Bung U n i t 22. Transfer Port Brick 23.Reducer Bung Top Half Reducer Bung Bottom Halt 24. Standard Sphere U n i t Wall Assembly

m.II Standard Sphere Unit Base Assembly

m.I1

Standard Plug for Sphere U n i t , Mk.11 25. Standard Sphere (Lead) Z6.Standard Sphere Unit W a l l Asoembly

Mk.III Standard Window Brick 27. Standard Window Shield 28.10" x 6" Window Assembly

Figure 42 A 4-in lead-brick system [389]. (Courtesy of UKAEA, Harwell, and Lead Development Association, London.)

tainers.) Q p e A must meet certain design and performance specifications intended to ensure safe survival of rather severe conditions of normal transport. Type B must, in addition, survive specified severe impact and fire tests. Requirements are imposed based onthe form and activity level for each type of container. The radioactive material may be in a normal form, a nondispersible form either inherently or because of encapsulation, or in a form that has low specific activity (LSA), which means thatthe amount of radioactive material per unit volume or per unit weight is below specifiedlevels so that the hazards are relatively minor. For radioactive materials that are also fis-

503

Applications of Lead

F I R E SHIELD 1

SHIPPING SKID

Figure 43 Equipment for transporting a fucl asscmbly from the reactor to hot c:ell or cask [265].(Courtesy of Lend Industries Association, Ncw York.)

504

WATER ALONE

Chapter 4

WATER

+ LEAD

Water. 1.14 m

301,884 kg t Total Weight

-+

Lead, 0.23rn

60,554 kg

Figure 44 Reduction in weight of “portable” nuclear reactors with the use of lead shielding 1265). (Courtesy of Lead Industries Association, New York.)

sile, additional requirements are imposed to provide assurance that criticality (i.e., a nuclear chain reaction) will not occur. Each radionuclide is assigned two numbers: A , , which is the maximum number of Curies of special form permitted in a Type A package, and A?, which is the maximum number of Curies of nomial-form radioactive material permitted in a Type A package. When the total amount of radioactivity does not exceed the amount A>,LSA material may be shipped in “strong, tight packages” of lesser integrity than Type A, and LSA material of certain types may be shipped unpackaged (i.e., bulk). The design of casks involves technical aspects of gamma and neutron radiation shielding, heat transfer, metallurgy, and engineering mechanics, and, at times, also criticality control and ncutron shielding. Type B casks require a Certificate of Compliance from the Nuclear Regulatory Commission, which is preferably obtained before fabrication. The lead industry offers help in the design and fabrication of such components. For gamma shielding, the principal candidates are steel, lead, and depleted uranium. Occasionally, another metal may be used for a small container, and concrete or other material may provide part or all of the necessary shielding in disposable low-level waste containers. Uranium encased in steel would probably be used more often if it were not for the high cost of depleted uranium. The advantages of uranium are its high density, which results in a cask of smaller overall size and weight for a given capacity, and its resistance to fire and impact. Steel also has satisfactory resistance to fire and impact, and a steel cask is comparable in cost to a lead-shielded cask. The disadvantages of steel are its relatively low density and its high “buildup” factor, especially for low-energy gamma, resulting in a larger and

Applications of Lead

505

Table 12 Relative Weights of Cylinders for Gamma Attenuation Equivalent to 3, 6. and 9 in. of Lead 12651. (Courtesy of Lead Industries Association, New York.)

Equivalent lead thickness Inside diameter (in.) 12 24 48 72

6 Inches

3 Inches

9 Inches

Steel Uranium Uranium Steel Uranium Steel 0.70 0.75 0.75

1.79 I .64 1 .S6 I .S3

0.64 0.70 0.73 0.75

2.0 I 1.79 1.84 1 .S9

0.60 0.67 0.7 1 0.73

2.16 I .91 1.72 1.64

heavier cask. The loaded weight of a truck cask is limited to about 25 tons without specialpermits and various restrictions; rail casks as a practical matter for handling and transportation generally have a loaded weight not exceeding 100 tons. In consideration of the economic factors, including the payload capacity for a given weight, lead-shielded casks are most commonly used. Table 12 shows the approximate relative weights of cylinders of lead, uranium, and steel for providing a given amount of shielding against 1 MeV gamma, based on assumed required thicknesses of 3, 6, and 9 in. of lead. A small-diameter, heavily shielded cask of steel may weigh almost twice as much as one using lead. Figure 45 shows some of the design details for a cask for shipping 10 pressurized water reactor (PWR) or 24 boiling-water reactor (BWR) assemblies. The principal gamma shielding is 6 in. of lead bonded to a 3/4-in.thick stainless-steel inner shell and a 2-in.-thick stainless-steel outer shell. Surrounding this is 9 in. of awater-ethylene glycol solutionfor neutron shielding, and a 3/4-in.-thick outside shell. The baskets for the fuel contain neutron poisons for criticality control. Helium is used as the coolant. The bottom and the lid utilize uranium for gamma shielding and a solid plastic or polymerfor neutron shielding. During shipment,thecask is equipped with balsa-woodimpact limiters. The loaded weight is almost 100 tons. Casks for shipping fuel decayed for several years may be somewhat simpler because of the lower heat output and lower gamma radiation.

C. Spent-FuelStorage Thespentfuel is stored in the water-filled basins priortoshipmentfor reprocessing or storage in permanent repositories. With restrictions on re-

506

Chapter 4

Figure 45 Railcask assemblyapprovedforshipping 10 PWR or 24 BWRmaterials. Lead is primarilyused for gamma shielding, and awater-ethylene glycol solution is used for neutron shielding. Helium is used as the coolant. The loaded weight of this rail cask assenlbly is nearly 100 tons 12651. (Courtesy of Lead Industries Association, New York.)

processing and delay in finding permanent repositories, the spent fuel is likely to be stored in casks in a monitored retrievable storage facilities, awaiting pennanent burial. The cask, shown i n Figs. 46 and 47, will accommodate S2BWR or 18 PWR assemblies that have cooled for S years o r more 12651. The body of the cask has a 0.7s-in. stainless-steel inner shell, 4.25 in. of lead, 2.0 i n . of stainless steel, 6.0 in. of borated ethylene glycolwater solution, and a 0.25-in. stainless-steel outer shell. The basket or egg crate for the fuel is constructed of stainless clad bora1 for criticality control, plus a copper plate to conduct heat to the cask wall. Dry storage is planned; the criticality control is needed only when exposure to water is anticipated by accidental flooding or during underwater loading when the cask is used for shipping waste from reactors.

D. Storage of Nuclear-Waste Packages in Underground Repositories The nuclear reactors worldwide generate 1500 metric tons of' spent fuel per year 13901. These spent-fuel elements and wastes contain mixed fission product isotopes that emit lethal levels of radioactivity. These must either be

Applications of Lead

507

Figure 46 A cask for possible use in monitored retrievable storage to accommodate 52 BWR or 18 PWR assemblies [265]. (Courtesy of Lead Industries Association, New York.)

Figure 47 A schematic of the cask for possible use in monitored retrievable stor46 [265]. age toaccommodate 52 BWR or 18 PWR assemblies showninFig. (Courtesy of Lead Industries Association, New York.)

Chapter 4

508

reprocessed, producing a waste stream, or disposed of in its unaltered form as spent-fuel rods. As they have a half-life from a few seconds to as high as several thousand years, the spent-fuel rods or the reprocessed waste must be shielded and stored for a long time at safe locations. Many countries are evaluating safe geologic disposal of nuclear fuel waste [391]. In geological disposal, fuel bundles and/or reprocessing waste would be placed inside metallic, corrosion-resistant containers, sealed, and then buried in a mined-out vault deep in the geologic formation. Additional engineered barriers would separate the waste and the geological formation. The engineered barriers would include the corrosion-resistant container, a bentonite clayhand mixture around the container (called the “buffer”), and backfill and sealing materials in the mined-out shafts and disposal rooms. These multiple barriers could retard radionuclide migration to man and environment [390-3931. Nuclear-waste disposal research and development activities in the United States are guided in general by the Nuclear Waste Policy Act of 1982 [393]. This Act has focused activity on developing the first two repositories in United States, a system of monitored retrieval storage and an away-fromreactor spent-fuel storage facility. Whereas defense waste and certain commercial wastes will be subject to reprocessing and vitrification before disposal, it is anticipated that much of the commercial reactor waste will be disposed of as spent fuel. The ideal waste package for disposal of either reprocessed waste or spent fuels would be strong, corrosion-resistant. lightweight, inexpensive, easy to fabricate, and a good radiation barrier [394]. In the case of unreprocessed spent fuel, the barrier afforded by the glass isnot there and the corrosion requirements would appear to be more critical. However, it will be offset to some extent by the lower temperatures due to decreased power density in the disposed unreprocessed fuel.The fuel cladding itself may contribute a barrier, but its effectiveness for this purpose is not yet certain.

1.

Use of Lead in Nuclear WastePackages

Lead has three outstanding positive features for waste package application: It is relatively easy to fabricate and process, it has excellent radiation attenuation characteristics. and from a conservation standpoint, it is i n plentiful supply and relatively inexpensive. Negative features include mechanical weakness if not accommodated by design, low creep strength, higher cost than iron-based alloys (although it has higher corrosion resistance than these alloys), and toxicity. Lead has been considered for use as either a stabilizer or a filler material i n high-level nuclear-waste packages. In the case of waste packages

Applications of Lead

509

containing spent fuel, the lead would completely surround each of the spentfuel rods. In this stabilizer (or “matrix”) capacity, the lead would help protect the container against lithostatic crushing forces, enhance heat transfer, stabilize the spent-fuel waste form against the mechanical shocks associated with transportation, and act as a secondary barrier between the waste form and the repository groundwater. The attenuation characteristics of lead reduces the radiation emissions, protecting both workers and the groundwater that could surround the container. Lead also helps reduce the centerline temperature because of better heat-conduction properties in the container. In the case of reprocessed waste, the waste is immobilized in vitreous glass. Present waste package designs for processed nuclear wastes are centered around the use of a borosilicate glass, based on years of work with glass formulations.A new lead-iron-phosphate glass for use in nuclearwaste disposal has been developed [393]. Depending on the amount and type of nuclear waste (commercial or defense) contained in this glass, 4066 wt.% PbO, 30-55 wt.% P,O,, and 0-10 wt.% Fe,O, would be used in the glass formulation. The corrosion rate is as much as 1000 times less than for borosilicate glass at 90°C; the formation temperature is 100-250°C lower than the temperature for borosilicate glass (1 150°C); the melt viscosity and pouring temperature (800-1000°C) is significantly lower than the pouring temperature for borosilicate glass ( 1 150°C); and the molten glass is reported to be a solvent for the elements found in both CHLW (commercial highlevel waste) and DHLW (defense high-level waste). If the performance of a production-size waste form made from this new glass formulation is equal to the laboratory test results, then this glass could enhance the isolation of processed nuclear wastes. This glass formulation might also make the production of glass marbles easier because of the reduced pouring temperatures, and it might improve the corrosion characteristics of the waste form. For waste packages containing a glass waste form, lead could be poured into the annulus between the container and the canister as a filler material. The resulting layer of lead could then serve lithostatic pressure protection, heat transfer, and corrosion-barrier roles. The minimum target life of the container is 500-1000 years. Two of the package design concepts showing these applications are shown in Figs. 48 and 49 [394]. Acceptability of lead in these applications will depend largely on its stability in the anticipated environments which the waste package will see over its very long design life. These are largely dependent on the surrounding geology and local temperatures, which will be elevateddueto waste placement. The U.S. requirements for radionuclide release are very strict: none for the first 300-1000 years, and only 1 part in 10000 for the next 9000 years [393]. Thus, the package must possess a very high corrosion resistance, which needs to be accurately predicted from design data.

510

Chapter 4

4.68

Figure 48 Containment of unreprocessed fuel rods in alead matrixin Swedish waste package design [394].(Courtesy of Lead Development Association, London.)

In the United States, disposal of nuclear waste is governed by a-law which states that the final repository must begin receiving waste at the beginning of 1998. These shipments have not begun as of yet.InCanada, demonstration of a disposal vault will occur in the years 2000-2020, after which,anoperatingdisposalsitewillbegin. In France,anunderground facilityisto be selectedandstudiesinitiated. In GreatBritain,disposal investigations have been postponed for a period of 50 years from 1991. In Sweden, two copper-shell designs exist. A lead-filled container is one of thesedesignsthathasbeenprovenpossibletomakewithlessthan 2% porosity. In West Germany, disposal will occur in a salt formation at Gorleben. Shafts for investigation are to be sunk and all investigations com-

511

Appllcatlons of Lead /

IDENTICAL GRIPPINGHEADS

/

LEAD PREFABRICATED

I

TITANIUM SHELL. t = 5mm VITRIFIED WASTE

3

CHROMIUM-NICKEL STEEL 1=3mm

Figure 49 Containment of reprocessed fuel waste in vitrified form tesy of Lead Development Association, London.)

[394]. (Cour-

pleted in the 1990s. It is possible that a repository could be in operation by the year 2000. In Switzerland, the repository is likely to be constructed at a great depth in the crystalline rock under Grimsel in the Alps. Final selection is to be made in the year 2000 and the repository is to be operating by the year 2020. In Japan, the Science and Technology Agency (STA) is conducting research on the science and technology of repositories [395]. 2.

RepositoryEnvironment

The geologic environments being considered in different countries include plutonic rock (Canada, United States, United Kingdom, Sweden, Switzerland), volcanic rocks (United States), clays (Belgium), and salt (United States, Germany) [391]. Five different geologies are being considered for waste placement in the United States: basalt, volcanic tuff, salt (either bedded or domed), granite, and shale [390,392,393]. ILZRO-sponsored work has determined the behavior of lead in the U.S.and Canadian repository environments proposed. A description of the results from the ILZRO-sponsored efforts are presented in a later section. The effect of these geologies on the waste package is manifested in the compositions of groundwaters to which the waste package would be exposed if flooding occurred. Factors such as heat transfer and permeability are also important. Groundwater char-

Chapter 4

512

acteristics that impact lead corrosion are pH (hydrogen ion concentration), Eh (redox potential or oxidizing power), and ionic species present [393]. The corrosion resistance of lead depends on the formation of a protective surface film of corrosion products. Highly insoluble lead surface films include the sulfates, carbonates, and complexes containing a high proportion of lead dioxide. Whether or not these surface films can be formed depends heavily on the groundwater pH and Eh values. On the Earth's surface, waters typically have values of pH = 7 and Eh = 0.8 1 , which can oxidize all canister metals proposed for waste packages. At the depths of the proposed repositories, however, the quantities of dissolved oxygen (affecting Eh)and carbon dioxide gases (affectingpH) can change dramatically with temperature [ 3921. Temperature in the repository environment depends on the age of the waste, the density of waste loading, the type of host geology, and the elapsed time since the waste was placed. In the United States, a peak temperature of 375°C was specified for Type 304 stainless steel to prevent sensitization, but peak operating temperatures will be less than 300"C, slightly below the melting point of pure lead, 327°C [392,394]. Table 13 presents the reference

Table 13 Reference Peak Near-Field Temperatures (ONWI 1980) [ 392 I Host rock Salt

Basalt

Location Host rock Canister wall Waste Host rock Canister wall Waste

Tuff

Granite

Shale

Host rock Canister wall Waste Host rock Canister wall Waste Host rock Canister wall Waste

Spent-fuel temperature ("C) 140 145 175

3-PWR 1-PWR 3-PWR 1-PWR 3-PWR I -PWR

assemblies/canister: 245 assembly/canister: 165 assemblies/canister: 2.55 assembly/canister: 170 assemblies/canister: 275 assembly/canister: 1 X5 190 I95 230 150 170 190 12s 140

165

51 3

Applications of Lead Table 14 Peak Operatrng Temperatures of ProposedWaste

Repositories [ 3941 Temperature Country United States United Kingdom Belgium Sweden Canada

300 150 100

75 1 so

Various rockCrystalline Clay rock Igneous Crystalline rock

near-field temperatures anticipated in different geological repositories [392]. Table 14 presents the peak temperaturelevels in several proposed waste repositories [394]. Strong radiation fields decompose water, increasing hydrogen ion concentrations. Within 100 years, radiation levels in commercial wastes decrease by several orders of magnitude and radiation will probably not be important for corrosion-produced hydrogen 1395,3961. 3.

Corrosion Performance of Lead in U.S. and Canadian Repositories

In the United States, three kinds of waste form are expected i n repositories: (1) commercial high-level waste (CHLW) composed of borosilicate glass, (2) defense high-level waste (DHLW)also made of borosilicate glass, and (3) spent fuel that may arrive either as consolidated or unconsolidated fuel rods [393]. Provisions are made for spent fuel arriving in the original assemblies (for tuff and salt repositories), consolidated spent fuel in boxes (for tuff and saltrepositories), or consolidatedspent fuel in low-carbon-steel (LCS) canisters (for basalt repositories). The canister material that is presently selected for borosilicate glasses is 304L stainless steel (SS). If spent fuel is consolidated in boxes, they will probably be SS. As mentioned earlier, lead and lead alloys may be present as a tiller material between the cannister and the borosilicate (or other newer glass waste formulation mentioned earlier) in the bore-hole design or between the cannister and the unprocessed fuel rods in shielded design. Two major concepts for waste packages in current repository designs are ( I ) the boreholedesign in either the vertical or horizontal orientation and (2) the self-shieldeddesign,where a thick cast-steeloverpack limits radiation levels such that waste can be emplaced i n the floor of the repository tunnels. The design for a tuff repository provides for either horizontal or

514

Chapter 4

vertical boreholes.Boreholesare horizontal in basalt and vertical in salt repository designs. Only the basalt and salt repositories will have the selfshielded packages. In general, the borehole design for CHLW and DHLW consists of the original pour canister encased i n m overpack made of SS (for tuff), LCS (for basalt), or LCS overlayed with titanium (for salt). The ILZRO-sponsored study carried out by Battelle Northwest Laboratories has evaluated the corrosion performance of lead and lead alloys in basalt,salt, and turf environments.Theevaluationalso included galvanic corrosion of Pb when i n contact with Ti. Tables IS and 16 present the groundwater chemistry i n different basalt and turf environments (3811. Salt environments included saturated NaCl as well as MgCI, environments. Table 17 presents groundwater chemistry in Swedish granite repository environment (3921. Corrosion rates after 1, 3, and 6 months at a temperature of 9095°C in simulated basalt. salt, and tuff environments is presented in Table 18 13933. Corrosion rates as a function of temperatures after 3 months are shown in Table 19 [397]. Figure SOa presents the corrosion rates when lead is galvanically coupled to Alloy 825 i n a simulated repository groundwater environment in the presence of radiation at a level of 3 X IO' rad/h [3961. Figure Sob presents similar data for a lead- 1 .S% antimony alloy (3961. The study suggested that in the volcanic tuff environment, which is main focus in the United States, in both irradiated and nonirradiated environments, the corrosion rates were less than S pn/year under the different condition tested after 6 months of testing. The addition of antimony substantially reduced the corrosion rates in these environments, and after 6 months of exposure,

Table 15 A Typical Basalt Groundwater Chemistry [ 3931

Range Analysis

(mg/L) 250 I .9 1.3 0.4

27 70 I .4 148 108

37 IO3

515

Applications of Lead Table 16 A Typical Turf Groundwater Composition 13931 Analysis Li Na K ca ME Sr Ba Fe AI SiOz F CO: HCO,

cl-

so3 Po: NO,

~

Range (WL) 0.05 51 4.9 14 2. I 0.05 0.03 0.04 0.03 61 2.2 0 120 7.5 22 0.12 5.6

Table 17 Swedish GraniteGroundwater Composition 13921 Analysis PH KMnO, consumption

ca’ 1

Na ’ Fe total HCO-

c1 so:

F SiO, HS

Range 7.2-8.5 5- 10 mg/L 25-50 mg/L IO- I00 mg/L 1-20 m a 60-400 mg/L 5-50 mg/L 1-15 mg/L 0.5-2 mg/L 5-30 mg/L 4 . 1 - 1 mg/L

Table 18 Composition of Calculated Corrosion Rates for Lead and Lead Alloys Exposed for 1, 2, and 3 Months in Simulated Basalt and Salt Environments at 150°C and in a Simulated Tuff Environment at Approximately 90-95°C [393J ~~

~

~

~~~

Corrosion rates (pn/year) -

~~

~~~~

~

Pb- 1 S % S n

Pb- 1.6%Sn

Environment Basalt Bottom Middle TOP Salt Bottom Middle TOP Tuff Bottom Middle TOP

Oxygen-free lead

Corroding lead

1 mo

3 mo

6mo

1 mo

3 mo

6mo

1 mo

3mo

6mo

1 mo

3 mo

6mo

1.4 I .8 2.0

1 .o

0.4 0.4 0.7

1.6 1 .9 1.2

0.9 1.3

0.1 0.1 0.1

3.5 2.8 3.2

2.0 I .7 1 .5

0.5 0.2 0.5

4.2 NA 2.8

1.8

1.1 1.1

NA 2.1

0.8 0.3 0.5

0.5 0.7 1.5

0.2 0.5 0.7

0.4 0.4 0.6

0.7 0.6 0.9

0.3 0.2 0.3

0.2 0.2 0.2

1.6 1.7 1.6

1.8 1.6 1.3

0.4 0.6 0.6

0.5 NA 3.4

3.2 NA 1 .5

0.7 0.6 0.8

16.7 13.3 7.3

17.6 8.0 4.5

9.8 7.7 10.1

16.0 10.6 8.0

21.7 9.2 7.2

18.6 7.8 14.1

55.3 29.6 32.7

23.3 28.6 10.6

36.3 20.4 13.3

42.8 NA 37.9

29.4 NA 13.0

30.8 NA 19.5

1

.o

P

Table 19 Calculated Corrosion Rates for Lead and Lead Alloys After 3 Months of Testing in Simulated Basalt and Salt (NaCI) with MgClz Brine, and Tuff Environments at Several Temperatures 13971 Corrosion rates (km/year) ~

~

O x y gen-free

Pb- 1.5 % Sn

Pb- I .6%Sn Environment

55°C

90°C

Basalt Bottom Middle TOP Salt Bottom Middle TOP Salt/MgCIz Bottom Middle

200°C

55°C

1.1 1.1 1.0

1.3

-

-

I .3

1.3

-

-

1.o

0.8

-

1.1

0.9

0.9

-

0.9 0.4

0.3 0.2 0.3

0.7 -

0.5

-

1.9

90°C

150°C

592 8.1 9.4

TOP Tuff

Bottom Middle TOP

150°C

5.6 -

6.2

4.5 8.0 18

lead 200°C

90°C

Corroding lead

150°C

55°C

90°C

150°C

200°C

1.5 1.7 2.0

-

2.0 NA 1.2

2.1 NA 1.8

.9 .x

0.7 NA 0.8

1.5

.5

NA 3.2

1.3

-

1.3 I .6

-

1.8

-

-

309 247 60

327 1 I9 146

-

-

-

-

-

-

12 NA 7.3

13 NA 29

-

518

Chapter 4 Envlronments: 0 Vapor *Rock-Vapor 0 Rock-Water

2

- 1.2 - 1.1 - 1.0 - 0.9 5 - 0.6 2 - 0.7 Bc c

0

0

0

i

!l0' 5

"Month Data

-

S_ 0.6

g

- 0.5 t8 @ - 0.4 9 - 0.3 - 0.2

month Dats

Envlronments: OVapor .Rock-Vapor 0 Rock-Water

-

- 1.2 - 1.1 - 1.0 - 0.9 t - 0.8; - 0.7 Ed c - 0.6 - 0.5 a. - 0.4 8 f U - 0.3

g

Galvanic

Galvanic Cwples

@

- 0.2 - 0.1 %Month Data

BYonth Data

Figure 50 (a) Corrosion rates of lead is galvanicallycoupled t o Alloy X25 in a simulated tuff environment in the presence of radiation at a level of 3 X 10' rad/h. (b) Similar data for a lead-1.5% antimony alloy 13961.

Applications of Lead

519

corrosion rates were below 3 p,m/year. Galvanic coupling with Alloy 825 increased the corrosion rates as expected. Allof these corrosion rates are well within the practical design parameters for the container concepts considered i n the United States. A container using lead as a corrosion-barrier component would last for a period of time between several hundred years and many thousands of years, depending on the thickness of the lead placed in the container. All corrosion occurring on these specimens was found to be rather uniform, except in the immediate area of the connection for the galvanic couples around which localized increases in corrosion were found. N o pitting corrosion was observed. The ILZRO-sponsored work on nuclear-waste disposal at Atomic Energy of Canada, Ltd. (AECL) dealt with spent-fuel rods contained i n a lead matrix within a titanium cask. It is surrounded by bentonite in granite. Figure 5 1 shows the waste-storage design i n Canadian repository environments [398]. One of the major concerns is the corrosion of lead galvanically coupled to Ti. Once the Ti layer integrity is compromised due to corrosion or other damage, lead (in contact with Ti) will be exposed to groundwater. In multivariable corrosion experiments, corrosion of lead galvanically coupled t o Ti never exceeded 3 p,m/year. Table 20 shows the nominal compositions of groundwaters in which corrosion rates were examined (3991. Figures 52S6 present the dependence of corrosion rate of Tadanac lead from Cominco

520

Chapter 4

Table 20 Nominal Compositions of Different Canadian Repository Groundwaters 1399)

Concentration (mg/L) GG"

I on

N;I

8.3 3.5 3.9 13

K ME ca Sr Fe Si

HCO, CI

so., NO,

F PH

I"

ND 5 .0 8.6 0.62 0.19 6.5 5 0.5 0.00 15

WN-lh 1,910 14 61 2, I30 24 0.56

SCSSS' 5,050 50 200 IS,000 20 -

-

15

68 6,460 1,040 33 -

10 34,260 790 50

7.0 5 0.5 0.26

7.0 5 0.5 1.37

-

"Gmniic groundwater. "Whiteshell Nuclear Solution. 'Standard Cniindian Shield Solution "Ionic strength (mol).

on ionic concentration, titanium/lead surface-area ratio, diameter of lead, and time [399]. 4.

Medium-Term Storage of Waste

Monitored retrieval and storage (MRS) has been proposed as a method for temporary commercial nuclear-waste storage at an away-from-reactor site in the event that a geologic repository cannot be constructed in time. Two storage concepts that have been proposed for MRS in the United States are sealed storage casks (also referred to as concrete silos) and field dry wells [393]. The design of apparent first choice is presently the sealed storage cask, which would consist of a cylindrical concrete structure with an inner steel liner, a central hole for storage of several stainless-steel canisters, and a closure lid. The sealed storage cask is designed to hold canisters containing either spent fuel or reprocessed waste. Each spent-fuel canister would contain rods consolidated from several BWR or PWR assemblies. The number of canisters in the cask and their dimensions could be adjusted within limits to accommodate different canister designs that might be required for ultimate

Applications of Lead

521

Figure52 Three-dimensional plots showing the effect of oxygen content and ionic strength on the corrosion rate of Tadanac lead at 293 K (a), 363 K (b), and 423 K (c) [399].

522

Chapter 4

Figure 53 Three-dimensional plots showing the effect of Pb diameter and surfacearea ratio on the corrosion rate of Tadanac lead a t different ionic strengths [399].

Applications of Lead

523

Figure 54 Three-dimensional plots showingthe effect of surface-arearatio and ionic strength on the corrosion rate of Tadanac lead at different times [3991.

524

Chapter 4

+ & A

x,

=

-1

(Surface Area Ratio= 8.5)

x,

=

0

2.0EZ W

GI.OE2 K O.OEO

\.@

(Surface Area Ratio= 75.5) 3.0E2

2.OE2 r

a =I.OEZ O.OEO

,.@

Figure 55 Three-dimensional plots showing the effect of time and ionic strength on the corrosion rate of Tadanac lead at different surface-area ratios (3991.

525

Applications of Lead

200

(Ionic Strength

=

0.0015 mol)

=

+l

Y

;!Q0 DI

0

,.ata

2.OE2 Y

zl.OE2 DI

O.QEO

,$Q

x, 3.0E2

-

(Ionic Strength

=

1.37 mol)

2.0E2

U .

eI.0E2

0.060

,

Figure 56 Three-dimensionalplotsshowingtheeffect of timeand surface-area ratios on the corrosion rate of Tadanac lead at different ionic strengths 1399).

Chapter 4

526

disposal at a repository. The canisters would be tilled with an inert gas t o limit oxidation of U 0 2 in any defective fuel rods. At present, the till gas is argon, although another inert gas could be used. Sealed storage casks are being used at the Nevada Test Site (NTS) in the United States and at the Whiteshell Nuclear Research Establishment (WNRE) in Canada. The other choice for MRS are storage in field dry wells. The field dry well consists of a large array of individual waste canisters emplaced in ground-level holes. Each steel-lined hole holds one canister containing processed wastes or spent fuel (either consolidated or unconsolidated). Field dry wells have been used at the Idaho National Engineering Laboratory near Idaho Falls andat the NTS. In both designs, lead is used as tiller material between the canister and the compacted waste or unreprocessed fuel rods.

E. Lead in Other Radiation Environments Lead is widely used for numerous x-ray and y-ray shielding applications in a number of medical, research, and industrial equipment. A few examples are presented here.

1.

Industrial and Medical Applications

CT Scannerx ar~clX-ray Diffruction Units. There are several locations in a medical and industrial CTscanner where lead is used for radiation shielding. Lead lining is used to provide radiation shielding in the massive x-ray housing. Figure S7 illustrates such an use in the x-ray housing of a GE Medical System’s CT scanner. In addition, leadis also used in the xray tube housings to provide the needed radiation shielding. The different components made of lead inanx-ray tube housing are shown in Fig. 58. Besides shielding, lead is also used for the x-ray collimators used in the CT scanners target ring assemblies. Figure 59ashows precision die-cast lead collimators for an Imatron Ultrafast CT Scanner target ring assembly (Fig. S9b). The target ring creates the fan of x-ray beams that must pass through the patient to image internal organs. The lead collimator is a small precision part with thin sections made to a tolerance of only 1.25 pm (?O.OOOS in.). Lead-lined enclosures and lead-glass windows are used for shielding in x-ray diffraction equipment used in material characterization. In dentists offices, leaded vinyl aprons are used to provide the needed radiation protection. Hi,qk-E/~er;qyPar.tkle Detectors. One of the interesting applications of lead is its use i n a new detector for high-energy subatomic particles. The detector designed by the physicists at Fermi National Accelerator Laboratory in Batavia, Illinois uses a sheet lead with hundreds of narrow ribs running its entire length. Every groove between the ribs has to be precisely the same

Applications of Lead

527

Figure 57 Zeus x-ray shield casing in GE medical systems CT scanner. (Courtesy of Vulcan Lead, Milwaukee, WI.)

width. This sheet made by Vulcan Lead using a special rolling mill is shown in Fig. 60. Fiber-optic cables are then inserted into the grooves to create an extremely sensitive detector of subatomic particles.

Lead in X-Ray Image Intensijiers and Filters. Apart from the use of lead in x-ray tubes and as radiation shielding aroundx-rayradiography equipment, lead is also used in x-ray intensifying screens to decrease exposure times and in the absorption of scattered x-ray radiation that reduces the sharpness of the image during radiography [400].

Figure58 Components of a simplified x-ray tubing casing made from lead. (Courtesy of Vulcan Lead, Milwaukee, W.)

528

Chapter 4

ELECTRON

Figure 59 (a) Crystal collimator detectors made of lead for the industrial Ultrafast C T scanner for x-ray tomography of industrial components and systems (tolerances on these cast parts are 50.0005 in.). (b) A schematic of the C T scannersystem showing the geometry of the target ring assembly. (Courtesy of Vulcan Lead, Milwaukee, WI.)

In x-ray radiography, the energy absorbed in a photographic emulsion on the filmis a small fraction (less than 1%) of the energy in the x-ray beam. The overall efficiency of energy absorbed can be increased using an intensifying screen and the exposure times can be shorter. This allows an economic use of x-ray equipment in industrial radiography and reduces radiation exposure to patients in medical radiography. The intensifying screen absorbs the radiation of the x-ray beam and generates secondary radiation

Applications of Lead

529

Figure 60 Groovedleadsheet that is part of the Fermi Laboratories’ subatomic particle detector. (Courtesy of Vulcan Lead, Milwaukee, W.)

that is more efficiently absorbed by the emulsion in the film. Intensifying screens give a gain of efficiency at the expense of loss in definition. The film is sandwiched between two intensifying screens. The two types of intensifying screen used are (1) fluorescent screens containing a paste of fluorescent salts such as zinc sulfate, calcium sulfate, or calcium tungstate, for use up to 130 kV and (2) a lead screen for use with high-kilovolt x-rays. In the case of lead screen intensifiers, secondary radiation is an x-ray that blackens the film. As much as a 100-fold increase in efficiency can be obtained by using a screen. The scattering can be reduced by increasing x-ray tube voltage, filtering off the softer components of x-radiation as the beam leaves the tube, using a filter between specimen and film to preferentially absorb the secondary radiation and by using grids that reduce scattered radiation. Grids are strips of lead built into a radiation-transparent material, with a height such that most of the scattered radiation is stopped by the strips, while the primary beam passes through them. The ratio of the height, h, of tile lead strips to the distance, d, between them is known as the grid ratio. Grid ratios typically are between 5 and 20. The higher the ratio, the greater the discrimination against scattered radiation and the greater the contrast. The grids are oscillated so that it will not cast shadows under the lead strips.

2.

RadiationShielding in X-Ray Installations

Commonly used buildingmaterials in walls,ceilings, and floors may provide an adequate level of x-ray protective shielding in a great many x-ray installations. When these materials do not furnish the necessary level of protection however, the protective barrier must be increased by either additional

Chapter 4

530

thicknesses of these materials or by adding a suitable thickness of a shield material suchaslead,concrete, or steel. Of these, the use of lead in a protective shield installation provides an effective,lightweight, and lowvolume attenuation barrier [401]. Design for radiation protection in areas adjacent to medical and industrial x-ray installations and in the operator booths depends on ( I ) the energy of the radiation source, expressed in kilovolts, (2) orientation and prqjected tield size of the useful beam. (3) distance from the source to the point where protection is required, (4) thc size and location of openings i n the barrier, (S) the geometrical relationship between the source of radiation, (6) openings, and the position of the person or object to be protected, maximum allowablc dose rate, and (7) machine utilization factors and amount of leakage radiation. The primary barrier for x-ray-beam attenuation and a secondary barrier for shielding against leakage and scattered radiation may involve sheet lead, lead laminated to common building materials, lead brick, lead-lined block, leaded glass, and a variety of leaded vinyls, Any openings in the protective barrier, whether nail, screw, or bolt holes, penetrations for pipes, ducts, conduit, electric service devices, louvers, doors, and windows must be so protected as not to impair the overall attenuation of the rays. Lead-glass viewing windows for patient observation from a control booth are available in sizes typically ranging from 30 cm by 30 cm to 90 cm by 90 cm. The use of lightweight partitions, where feasible, with the lead shielding built-in, should always be considered. Advantage may also be taken of the different forms of laminate available to achieve a hygienic and pleasing tinish without any additional treatment or decoration. To achieve the maximum all-round benefit, it is most important that the architect consult a certified radiation physicist or radiologist and the shielding installation contractor at the design stage. This will lead to achieving the required shielding in the building at minimum cost and without unnecessary waste of valuable floor space.

VII.

USE OF LEAD ALLOYS FOR PRINTING TYPES

Printing type was once one of the important uses of lead alloys. Although its use has declined, it is presented here briefly for historical reasons. The invention of printing could be traced to the Chinese [402,403]. I n the technique they used, images were carved on stone, the raised surfaces of the images were then inked, and the image transferred to the paper by pressing the raised surface against the paper. The next major invention occurred around 800 years ago by a Chinese printer Pi Shang. He made each Chinese

Applications of Lead

531

character out of a piece of clay. He assembled the different pieces in a line to form the lines of characters andused this box for printing. These individual pieces are now called “types.” These types could be reused again and again, and the movable type had been invented. The first cast-metal type was invented by the Koreans, who dominated the printing industry until about A.D. 1300. The modern printing machine credited to Johann Gutenberg was developed in the middle of the 15th century. Gutenberg cut each letter at the end of a stick or punch and pressed the shape into a sheet metal to form an depression. Several impressions were made to form a matrix of these depressions. Four wooden blocks were placed around the matrix and a low-melting Pb-Sn-Sb alloy (Babbit alloy) was poured in to form castings of the letters or types. These types were assembled on a plate used for printing. One of the first books he printed was the Bible, known widely as the Gutenberg Bible. The printing technology remained unchanged until the invention of lithography around 1800. Other major inventions that changed the printing industry include mechanization of the printing machine, the invention of photography in the 19th century, the linotype machine and the arrival of computers, photocopy machines, the laser, and inkjet printers. The advent of computers and the evolution of photocopying have revolutionized the printing industry and the use of types and typesetting has nearly vanished [389]. Albert Einstein once worked as a typesetter and, if alive, he would certainly marvel at the changes in the printing technology. Gutenberg used the Babbitt alloy, as it had low melting point and had very low solidification shrinkage. Until a century ago, letters were exclusively cast by hand and assembled to form sentences.These individually cast printing types for handsetting are referred to as foundry types. With the invention of monotype, linotype, and stereotype processes, the typesetting and composition became more mechanized. In the monotype process, holes that correspond to the depressed letter key are first punched in a paper strip. The strip of paper is inserted into the casting machine and types corresponding to the punched holes are cast.The cast letters are assembled in the machine to lines and the latter to columns. In the linotype machine, instead of casting individual letter types,a whole line is cast i n a block. If it is desired to produce many copies in a very short time (as in printing newspapers, periodicals, forms,etc.), then stereotyping was used. The original setting, together with the blocks contained in it, is molded in a specially prepared paper pulp under a hydraulic or mechanical press either at room temperature or with moderate heatand a matrix made of the whole area. The plates of the press are heated electrically. Printing plates corresponding to the original, the f a t stereos, are cast in it. For rotary printing, semicircular stereos are made instead of f a t stereos. Electrotypes are used a s backing

Chapter 4

532

plates and is not used directly in printing. They are therefore not required to resist wear [2,402-4041. The characteristics required of type metal are the low melting point, ability for tine-detail reproduction and dimensional accuracy by casting, high hardness, and low cost. Pb-Sb-Sn alloys have low melting points, very high hardness levels, and low shrinkage on solidification; thus, they were able to meet these requirements. Type metals are almost exclusively lead-antimony-tin alloys. The compositions of common type metals are shown in the ternary diagram of Fig. 61 [21. The solidus temperatures of these different alloys nearly coincide with the ternary eutectic temperature of 239°C. In the region of small antimony contents, the hardness is principally raised by an increase of antimony concentration, and at higher antimony contents(from about 10% to 15% Sb), this is accomplished mainly by an increase in tin concentration. Table 21 presents typical compositions and properties of type metals 14041. The melting and casting properties, the microstructure, and the hardness values determine the end application. The linotype alloys are in the vicinity of the ternary eutectic. They have a particularly low melting point and good fluidity as the result of a small solidification range. The stereotype

---- Amenion sfanhd U

2 4 6 8 7 0

W ,

-lemon siandord

Sn (wt,%)

Figure 61 The Pb-rich corner of a Pb-Sn-Sb ternary phase diagram showing the compositions of thc important type alloys 121. (Courtesy of Spinger Verlag,New York.)

Applications of Lead

533

Table 21 Typical Compositions and Properties of Type Metals [404]. (Courtesy of ASM International, Materials Park, Ohio.) Composition ( 7 6 ) Alloy Electrotype General General Curved plates Stereotype Flat plate General Curved plates Linotype Standard Special Ternary eutectic alloy Monotype Ordinary Display Case type" Case type Rules Foundry type Hard (1.5% Cu) Hard ( I .S% Cu) Hard (2.0% Cu)

Liquidus temp. ("C)

Solidus temp. ("C)

Sn

Sb

Hardness'' (HB)

95 94 93

2.5 3 4

2.5 3 3

12.4 12.5

303 298 294

246 246 246

80 80.5 77

6 6.5 8

14 13 15

23 22 25

256 252 263

239 239 239

86 x4 84

3 5 4

I1 11

19 22 22

247 246 239

239 239 239

78 75 72 64 75

7 8 9 12 10

15 17 I9 24

24 27 28.5 33 26

262 27 1 286 330 270

239 239 239 239 239

60.5 20 58.5 61

13 20 12

25

Pb

12

15

-

25

" I O mm baI1/250 kg. hLanston.

alloys, and especially the monotypealloys,are more heavilyalloyed and therefore harder than the linotype alloys. In spite of the greater solidification range of the monotype alloys, there is no risk of harmful segregation, as cast individual letters solidify more quickly than the lines. The higher hardness of the monotype alloys is necessary because the mechanical stress is greater in individual type than in whole lines. In stereotypes, the stress is particularly high in the printing process for large editions of a newspaper. Of thestereotypealloys, those with tin contents of 5% or 6% lie in the primary solidification field of antimony. The alloys with higher tin content, on the other hand, lie in the primary solidification field of Sb-Sn. The alloys of greatest hardness are specified for casting of types for handsetting, as they are not remelted after each setting but used again and again.

534

VIII.

Chapter 4

BEARINGMETALS

Bearingmetal refers to thematerialthatformsthe working surface of a bearing. The bearing metal is the softer material of any pair of metals which comprise a bearing. The function of the bearing is to support the load on the shaft and provide minimal friction to the motion of the shaft, allowing efficient transmission of power. Some of the widely known alloys for bearing applications are Babbit alloys, which are Pb- or Sn-based alloys. The environmental concerns in the recent years has put pressure on the elimination of lead in these applications. A brief description of the performance requirements in these applications and how the use of tin-lead-based alloys have met these requirements is presented in this section.

A.

Performance Requirements of Bearing Materials

Figure 62 shows the configuration of a journal bearing in which lead-tinbased alloys are extensively used. The original impetus to the development of bearing materialswas the stationarysteamengines.The rail transport, shortage of certain alloying elements during World War I, and the internal combustionengineprovidedfurtherdrivingforce in thedevelopment of lead-tin-based bearing alloys. The crankshafts in these engines are carried by a number of plain rod bearings. Lead-tin-based bearings are the most common of the crankshaftbearingsmaterials.Theincreasingseverity of working conditions, in recent years, has required their replacement with stronger alloys based on aluminum or copper. The duties, the performances, and the characteristics of the bearing metaldepends, to someextent, on theproperties of the shaft material [2,405]. A plain bearing that is to run permanently must be designed and lubricated so that the bearing surfaces are completely separated in service by a filmof lubricant. Such a condition is known as hydrodynamic lubrication and is illustrated in Fig. 62a [405]. Sliding with partial or full solid contactgenerallyleadsto high friction,higher wear, and aconsiderable temperature rise. The shaft rotation in this situation occurs under the condition of boundary lubrication, as shown in Fig. 62b [405]. In plain bearings, sufficient hydrodynamic pressure must be created to support the load of the

>

Figure 62 (a) Configuration of a journal bearing under boundary lubrication con-

dition; (b) configuration of the journal bearing under hydrodynamic lubrication condition: (c) load-shaft rotation velocity (PV) curves for plain bearings [405]. (Courtesy of Butterworth Heinemann, Oxford, UK.)

535

Applications of Lead

Pomt of coniocl

Oil fllrn bearings (Width = 0 6 d )

}

Hydrodynarnlc lubrlcatlon Boundary lubrlcatton

Dry-rubbly baarmgs(ptfe tOOOOh hfe ( b / d = l ) Dry rubblng bearlnqs(graphlte) 5 0 0 h life ( b / d =1 . 5 ) Pre-lubrlcoied beorlngs < 5 0 m m d w . ( b / d = l ) Prs-lubrmted bearlngs z 50mrn d m ( b / d = 1 1

(c)

1.-.-.-

.-..................

536

Chapter 4

shaft. The region between the bearing surfaces, the bearing space, must have a shape suitable for this purpose. Frequently, use is made of a wedge shape, narrowing in the direction of motion. The attainable hydrodynamic pressures and, consequently, the bearing capacity increase when the narrowest gap of the bearing space is decreased and the gap is made uniform in the axial direction. In journal bearings, the wedge form of the gap is usually attained by the eccentric position of the journal in the bush (Fig. 62a).It has been shown experimentally in journal bearings that the gap configuration has a remarkably great effect on the bearing capacity. It is also important for the development and maintenance of hydrodynamic pressures that the bearing surfaces be impervious to the lubricant under pressure. An increase in bearing temperature not only reduces the strength of the bearing material but also lowers the viscosity and the chemical stability of the oil. Bearing materials must dissipate at least a part of the frictional heat by thermal conduction. Here, apart from the thermal conductivity, the thickness of the lining is of importance. The maximum load-carrying capacity of the bearing is related to the rotational velocity. The relationship between rotational speed and maximum load for various shaft diameters and lubrication conditions is shown in Fig. 62c 13911. These curves are known as load-shaft rotation velocity (PV) curves and are used to select the bearing for a given application. Mixed friction is present when the hydrodynamic pressure hasnot kept the bearing surfaces completely separated, and, as a consequence, contact of the solid bodies takes place at different points. It occurs on starting and on stopping the shaft, on overloading, in the running-in process, and when there is a deficiency of lubrication. As the coefficient of solid-body friction is much higher than that of fluid friction, the friction and, consequently, the frictional heating become higher. In bearings which have already been run-in, the main function of the bearing material is to ensure a safe transition through the region of mixed friction on starting and stopping. The bearing surfaces should, therefore, be free from scratches that reduce the hydrodynamic loading capacity and surface deformation. During the running-in process. adjustments occur on the sliding surfaces, both in regard to the macrogeometric shape as well as in regard to the microgeometric shape. The loading capacity of a bearing depends on the compressive yield point of the bearing material at operating temperatures. The bearing metals of low strength such a s lead- and tin-based alloys are only used as a lining in a supporting shell, as a smaller thickness makes its plastic deformation more difficult. The hardness of the bearing material and of its individual structural constituents is of further importance with respect to ridge formation and wear of the shaft material.

Applications of Lead

537

High fatigue resistance is also preferred because of fluctuating stress conditions. Fatigue fractures begin at the bearing surface and penetrate the bearing material until close to the bond between the lining and the steel backing, then proceed parallel to this surface, so that a thin layer of bearing metal continues to adhere to the steel. The lining becomes more and more brittle and, finally, shatters. The low melting point of lead gives rise to a reduction of the fatigue strength with rising temperature. A similar behavior is also to be expected of the white metals based on lead and tin. The life of white-metal linings under dynamic stress is increased by a reduction of wall thickness. A fatigue strength of “15.0 MPa is observed for a steel-backed, tin-based white-metal bearing of 0.2 mm thickness, whereas the fatigue strength was increased to 27.8 MPa for a white-metal layer thickness of 0.04 mm 121. In addition to fatigue strength, the impact strength of bearing materials is of importance. In most cases, white-metal lining is put on a backing of steel, bronze, or cast iron. To attain adhesion, the backings are cleaned by pickling or by shot blasting and then tinned. The bearing metal is applied by casting in the space between the backing and a core, by pressure die casting, or by centrifugal casting.The latter method, in general,gives rise to considerable segregation in lead alloys,as the light phases such as Sb-Sn rise to the surface. Frequently, an intermediate layer of leaded bronze is used, which prevents damage to the shaft in the event of wear or of fusion of the white metal. In the so-called electrodeposited bearings, the white metal (lead with 8- 12% Sn or with 8- 12% Sn and 2-4% Cu) is electrodeposited to a thickness of 0.02-0.06 mm on leaded bronze. In order to prevent the diffusion of tin into the leaded bronze below it. a 1 - 1.5-km-thick barrier layer of nickel is applied below the white-metal layer. The leaded bronze layer, 0.5 mm thick, is supported by a steel backing. The thermal expansion of the bearing material and of the shaft material is responsible for the alteration of the bearing play with change in temperature. The difference in coefficient of thermal expansion between the bearing material and steel also determines the magnitude of the thermal stresses. If acid constituents are either present in the oil or are formed during service, corrosive attack on the bearing metal is to be expected. In this respect, tinbased bearing metals are considered to be superior to lead-based metals. In the event of corrosion in the copper-lead alloys, a preferential dissolution of the lead portion is to be expected, and lead is depleted in the surface layers affecting bearing performance. In general, the boundary layer lubricants are mixtures of long-chain hydrocarbons (paraffins) or the corresponding alcohols, esters, ketones, and acids. At temperatures below the melting point of the hydrocarbons, the chain molecules are grouped in bundles like twigs in faggots. Under the heat

538

Chapter 4

generated duringsliding, the faggots break upat a temperature near the melting point, leaving an actual boundary layer of molecules. The molecules are directly attached either perpendicular or slightly inclined to the surface. Above these, there are film molecules that are less precisely aligned. The maximum thickness of the boundary layer is of the order of <200 A. Good wettability and attachment of polar molecules to the surfaces improve the process of lubrication by facilitating the development of hydrodynamic pressure. The practical experience ascribes to lead-based bearing metals a better wettability for oil than to tin-based bearing metals. The radius of curvature of an asperity exerts a great influence on the hydrodynamic processes when it is pressed against a surface. The time of pressing to a given distance at constant force and the force for pressing with constant speed grow a s the square of the radius of curvature of the asperity. At very narrow gap widths, remarkably high pressures can be generated. At a constant pressing force, the pressure of liquid is inversely proportional to the gap width. At a constant rate of pressing, it is inversely proportional to the square of the gap width. Asthe asperity and the opposite surface are, however, not ideally rigid, they are deformed first elastically and then plastically, and thus adjust to one another. The better the adjustment of the asperities to the opposite surface and the closer the approximation to the ideal parallel gap, the greater the load-bearing capacity of the f i l m of lubricant. The first prerequisite for the cessation of wear and the increase of the running surface is that the sliding surfaces should be completely separated by a hydrodynamic f i l m of lubricant. The second prerequisite is that only elastic but not plastic defonnations should be brought about by the pressures and shearing stresses exerted by the f i l m of lubricant on the sliding surfaces. A low modulus of elasticity (at the temperature of operation) largely favors elastic deformations and therewith speedy cessation of wear. Good plastic deformability permits an adjustment without formation of wear particles. It also favors the embedment of hard wear and dust particles, provided bearing material is of sufficient thickness, so that wear of the shaft is reduced. This is important if little reliance is placed on clean filtration of the oil and on the cxclusion of external dust and sand. Materials that possess these characteristics include lead, tin, cadmium, and, at higher temperatures, aluminum.

B. Compositions of Lead-Based Bearing Alloys The widely known alloy for bearing applications is white metal introduced by Babbitt in 1838. The alloy contained 89-9096 Sn, 8-9% Sb, 1-2% Cu, and trace amounts of Pb. During the time period of the First WorldWar,

Applications of Lead

539

lead-rich white metals were introduced in England and these were also referred to 21s Babbit alloys. These alloys were essentially ternary lead-antimony-tin alloys. Table 22 shows the ASTM specifications for compositions and properties of the lead-based bearing alloys 14061. Larger contents of the high-melting metals such as copper and nickel in bearing alloys considerably increase the melting range upward. On cooling from the region of complete liquid miscibility, small amounts of Cuand Ni-containing phases precipitate out. Most of the alloys, if only the contents of lead, antimony, and tin are considered, lie in the primary crystallization field of antimony or of Sb-Sn of the ternary system and contain primary crystals of antimony or Sb-Sn in a binary or ternary eutectic matrix apart from the high-melting phases of copper already mentioned. Copper contents above 1.5% also increase the hardness of the alloys. Nickel content reduces the tendency for segregation, and nickel has a grain-refining action as well. Arsenic is present in solid solution in lead, in antimony, and in antimony-containing phases such as SbSn. The arsenic level should be kept below 0.8% to maintain a good impact strength. Cadmium, present in small amounts in white metals, is dissolved in lead or may be present as a precipitate in the solid state. The addition of zinc causes drossing, lowers the castability, and coarsens the structure. The lead-based white metals are inferior to tin-based alloys with respect to fatigue strength. However, Pb-based white metals are superior to tin-based alloys at elevated temperatures. The lead-alkali alloys (e.g., Bahnmetall) or the lead-tin-alkali alloys have a limited significance as bearing metals. An example of the lead-alkali bearing metals or precipitation-hardened bearing metals is Bahnmetall. The Bahnmetall contains 0.69% Ca, 0.62% Na, 0.04% Li, and 0.02% Al, and its structure consists of essentially primary crystals of CaPb, in lead solid solution. In the United States, similar alloys with 0.5-0.75% Ca, smaller contents of other elements, and an addition of about 1.5% Sn (e.g., Satco metal) have been used.

IX.

PACKAGINGANDSEALING

One of the advantages of excellent malleability and softness of lead is used in packaging. Lead foil, collapsible tubes, and seals are used in many engineering and other applications (2,3001. Lead collapsible tubes usually contain small percentages of antimony and may be coated with tin. The lead foil may be soldered or pressure bonded by an extremely simple process so that it seals the package hermetically when required. Being soft, lead foil bends readily without cracking. X-ray film is usually packaged i n lead foil to protect the photosensitive film from light rays. X-ray film for both dental

UI

P

0

Table 22 Composition and Physical Properties of White-Metal Bearing Alloys [ASTM B23-941 [406]. (Courtesy of American Society for Testing Materials, West Conshohocken, PA.) ~

Alloy No. 1 2 3 7 8 15

Alloy No. 1

2 3 7 8 15

Specific nominal composition of alloys (%)

Sn

Sb

91.0 89.0 84.0 10.0 5.0 1.0

4.5 7.5 8.0 15.0 15.0 16.0

Pb

cu

As

Specific gravity

0.45 0.45

7.34 7.39 7.46 9.73 10.04

1.o

10.05

4.5 3.5 8.0 Rem. Rem. Rem.

Johnson's apparent elastic limit (MPa)

Composition of alloys tested (%)

Yield point (MPa)

Sn

Sb

Pb

cu

20°C

100°C

90.9 89.2 83.4 10.0 5.2

4.52 7.4 8.2 14.5 14.9

0.03 0.03 7.5.0 79.4

4.56 3.1 8.3 0.1 1 0.14

30.3 42.0 45.5 24.5 23.4

18.3 20.6 21.7 11.0 12.1

Ultimate strength in compression (MPa)

Brinell hardness 10-mm ball. 500-kg load, 30 s

20°C

100°C

20°C

100°C

20°C

100°C

Melting point ("C)

16.9 23.1 36.9 17.2 18.3

7.2 7.6 9.0 9.3 8.3

88.6 102.7 121.3 107.9 107.6

47.9 60.0 68.3 42.4 42.4

17.0 24.5 27.0 22.5 20.0 21.0

8.0 12.0 14.5 10.5 9.5 13.0

223 24 I 240 240 237 248

Temp. of complete liquefaction ("C)

Proper pouring temp. ("C)

37 1 354 422 268 272 28 1

44 1 424 49 I 338 34 1 350

3al

-2

2

P

Applications of Lead

541

and industrial radiography useis also backed up with 0.025-9.5 mm(0.0010.375-in.)-thick lead foils/sheets. Anotherunique use of lead as a packaging material is in special caskets lined withlead for burial of the rich and famous and for shipping human remains across national boarders. Lead foils and sheets are used in many types of boxes or packages that are closed with tamperproof seals. Leadseals for closing moistureproof plastic packages are sometimes merely lead rings, which are slipped over the gathered end of the pliable plastic envelope and crimped tightly together. The soft lead thus seals the package tightly without damaging the plastic. These rings can be pried open and reused when necessary. In light bulbs, the vacuum seal between the metallic cap and glass is a Pb-Sn alloy (Fig. 63). Lead gaskets are used in engineering components to provide leak/vacuum tight seals. One of the interesting application of extruded lead tubes that made modem historyis their useinX-cordand jetcord, which are metal-clad detonating cords. These cords used in the mission and life critical systems in spacecraft, space shuttle, aircraft, and missiles for important functions such as initiation (Fig. M), separation, thrust termination, severance, and sequencing events. The explosive-filled lead tubes are extruded to fine dimensions and the explosive is under moistureproof seal and free from accidental exposure to static charges. The detonation velocities of several miles per second are achieved in controlled reliable manner.

P

.-..

.

. "*

..

'

.~

W.' Figure 63 A light bulb in which the vacuum seal between the metallic cap and glass is a Pb-Sn alloy.

542

Chapter 4

i

Figure 64 The different critical stages detonation cords.

X.

of space shuttle events us( lead-tube-clad

FUSIBLE ALLOYS

Lead is a constituent of a number of extremely useful low-me:lting alloys in which lead is usually combined 'with bismuth, tin, cadmium, or a combination of these metals (Fig. 65) [2,407,408]. Indium, antimony, and silver are also added in some of the alloys. Some of these alloys melt at a temperature lower than the boiling point of water, and those containing appreciable amounts of bismuth expand slightly upon solidification. Low-melting alloys are employed in safety devices such as sprinkler systems and boiler plugs, as special solders where high temperatures cannot be used, for molds, patterns, punches, and dies, for anchoring punches in punch plates, and for bending tubing. The melting point of lead-tin solders can be reduced below the eutectic of about 180°C by the addition of cadmium. The lead-cadmium-tin alloys have good soldering properties, as the melting point of the ternary eutectic is only 145°C. By adding zinc, a quaternary eutectic can be obtained with a melting point 138°C and composition 28.6% Pb, 16.7%Cd, 52.45% Sn, and 2.25% Zn. A further effective decrease in the melting point is obtained by additions of bismuth to the lead-cadmium-tin alloys. The opti-

543

Applications of Lead Bi

finery eutczic l24 (56 Bi t 1 b Pb)

m 0

I

Figure 65 Pb-Cd-Bi-Sn

Schematic representation of the mostimportant mcltingpoints in the quaternary system 121. (Courtesy of Spinger Verlag, Ncw York.)

mum alloy is a quaternary lead-cadmium-bismuth-tin eutectic with a melting point about 70°C and a composition of 50% Bi, 12.5% Cd, 25% Pb, and 12.5% Sn (Wood’s metal). The melting point of the quaternary eutectic alloy can be further lowered by additions of indium to 47°C. Addition of mercury instead of In could also lower the melting point of Pb-Bi-Sn-Ca eutectic, but it is not used because of its high vapor pressure and toxicity. The phases of the quaternary eutectic are the solid solutions corresponding to the lead, tin, and cadmium and the P-phase of the lead-bismuth system. The quaternary Pb-Bi-Sn-Cd eutectic alloy is brittle when cast, becoming plastic on storage for 2-3 h. In addition to the above quatenary eutectic alloys, alloys of the ternary lead-bismuth-tin system are also of great technical importance. One of these alloys is the Newton metal (50% Bi, 30% Pb, 20% Sn) which approximately has the ternary eutectic composition. The eutectic temperature of this system is 90°C. Anotherimportant alloy is Rose’s metal, with 50%Bi,25%Pb, and 25% Sn.Themeltingtemperature of Rose’s metal is 100°C. Alloy designations, composition, and melting points for low-meltingpoint alloys as per ASTMB774-95 specification are shown in Table 23

UI P

P

Table 23 Alloy Designations. Composition, and Melting Points for Low-Melting-Point Alloys as per ASTM B774-95 Specification (4081. (Courtesy of American Society for Testing and Materials, West Conshohocken. PA.) Constituents (wt.%) Alloy designation 1 I7 136 158 158-190 1 74

203 255 28 1 28 1-338 29 1-325 244 296 293 300-302 307-323 320-345

Bi

Pb

44.2-45.2 48.5-49.5 49.5-50.5 42.0-43.0 56.5-57.5 52.0-53.0 55.0-56.0 57.5-58.5 39.5-40.5 13.5-14.5 0.0 I 0.01 0.0 1 0.0 1 0.0 1

22.1-23.1 17.5- 18.5 26.2-27.2 3.2-4.2 0.05 3 1.5-32.5 44.0-45 .O 0.05 0.05 42.5-43 .5 0.05 0.05 29.9-3 1.1 14.5- 15.5 17.5- 18.5 29.5-30.5

0.01

Sn

Cd

7.8-8.8 4.8-5.8 1 1.5- 12.5 0.005 12.8- 13.8 9.5-10.5 10.8-1 1.8 8.9-9.0 0.005 16.5-17.5 0.005 15.0-16.0 0.0 1 0.005 4 1.5-42.5 0.005 59.5-60.5 0.005 0.005 42.5-43.5 0.005 47.5-48.5 0.01 0.005 50.7-5 1.7 17.7- 18.7 0.005 0.0 1 69.5-70.5 0.005 0.0 1 0.005

In

Melting points Ag

18.6-19.6 0.001 20.5-2 1 .5 0.001 0.001 0.008 0.008 0.001 25.5-26.5 0.001 0.008 0.001 0.008 0.001 0.01 0.008 0.01 0.008 0.008 0.01 5 1.5-52.5 0.1 96.5-97.5 2.8-3.2 0.01 0.008 79.5-80.5 4.5-5.5 11.5-12.5 0.01 69.5-70.5 0.01

Cu

0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08

Sb

Zn

0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08 0.1 0.08

All Solidus Liquidus others ("C) ("C) 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08

47 58 70 70 79 95 124 138 138 144

I I8 147 I45 149 153 160

47 58 70 88 79 95 124 138 170 163 118 147 145 1 50 162 174

9 P)

2 1 P

Applications of Lead

545

Table 24 Typical Applications of Some Common Fusible Alloys [407,408]

Alloy

Melting temp. ("C)

ASTM 117

47

ASTM 158 (Wood's metal)

70

ASTM 255

124

ASTM 281

138

Pb-48 wt% Bi-14.5 wt% Sn-9 wt% Sb alloy

103-217

Typical applications Dental models, part anchoring, lens chucking Bushings and locators in jigs and fixtures, tens chucking, reentrant tooling, founding cores and patterns, light sheetmetal embossing dies, tube bending, Wood's-metal sprinkler heads Inserts in wood, plastics, bolt anchors, founding cores and patterns, embossing dies, press-form blocks, duplicating plaster patterns, tube bending, hobbyist pans Locator members in tools and fixtures, electroforming cores, dies for lost-wax patterns, plastic casting molds, prosthetic development work, encapsulating avionic components, spray metallizing, pantograph tracer molds Punch and die assemblies, small bearings. anchoring for machinery, tooling, forming blocks, stripper plates in stamping dies

[408]. Table 24 presents typical applications of some of the common fusible alloys [407,408]. The fusible alloys are used typically as fusible links in sprinkler heads, as electric cutouts, as fire-door links, for making castings, for patterns in making match plates, for making electroforming molds, for setting punches in multiple dies, and for dyeing cloth. Some fusible alloys can be cast or sprayed on wood, paper, and other materials without damaging the base materials, and inany of these alloys can be used for making heimetic seals. Because some of these alloys melt below the boiling point of water, they can be used in bending tubing. The properly prepared tubing is filled with the molten alloy and allowed to solidify, and after bending, the alloy is melted out by immersing the tube in boiling water. The volume changes during the solidification of a fusible alloy are, to a large extent, governed by the bismuth content of the alloy. As a general rule, alloys containing

Chapter 4

546

more than about SS% bismuth expand and those containing less than about 48% bismuth contract during solidification. Those containing 48-55% bismuth exhibit little change in volume. The change in volume due to cooling of the solid metal is a simple linear shrinkage, but some of the fusible alloys owe much of their industrial importance to other volume changes, caused by the change in the structure of the solid alloy, which permit the production of castings having dimensions equal to or greater than those of the mold in which the metal was cast. For fire-sprinkler heads, with a rating of 71"C, Wood's metal is used for the fusible-solder-alloy link. Wood's metal gives the most suitable degree of sensitivity at this temperature. But in tropical countries and i n situations where industrial processes create a hot atmosphere (e.g., baking ovens, foundries), solders having a higher melting point must be used. Alloys of eutectic compositions are used because they melt sharply at a specific temperature. Fusible alloys are also used as molds for thermoplastics, for the production of artificial jewelry in pastes and plastic materials, in foundry patterns, in chucking glass lenses, as holddown bolts, and a s inserts in plastics and wood. They are also used for mounting complex metal shapes such as turbine blades for machining.

XI.

LEADHEAT-TREATINGBATHS

Molten lead baths are widely used for the heat treatment of steel a t temperatures between 350°C and 925°C 121. Lead baths have been preferred over other Sn- or Bi-based low-melting-point metal alloys due to lower cost. One of the examples of the use of molten lead is the patenting process [409]. Patenting is a special form of austempering unique to the steel rod and wire industry. In this process, the wire or rod is cooled from the austenitizing temperature by quenching it in a molten liquid, usually lead, at a temperature of about 540°C. The steel is immersed in the molten lead until the completion of the transformation to obtain a very fine pearlitic structure. This increases the amount of subsequent drawing that could be withstood by the wire and permits the production of high-strength wire. Lead is the only metal so used commercially and has a number of advantages over salts used for the same purpose. The high heat conductivity results in rapid heating, high output, uniform temperature throughout the bath, and high thermal efficiency. Lead does not decompose but does tend to oxidize. This can be minimized in practice by the use of a protective covering such as a layer of charcoal. coke, and salt coverings containing mixtures of sodium chloride, sodium carbonate, and potassium carbonate.

Applications of Lead

547

No appreciable chemical reaction of molten lead with pot material occurs. Cast iron, steel, special alloys such as low-nickel-chromium steel, and high chromium steel can beused as pot material. High-nickel-chromium steels are not preferred, as nickel dissolves in lead. Electrical heating as well as gas/oil-firing furnaces can be used to heat the pots. Unlike the salt baths, it does not absorb water. Also, lead does not tend to pit or decarburize the steel treated in it. Lead hasa high specific gravity and the work must be submerged by suitable means. Lead baths are especially useful for local hardening and tempering and, in fact, are probably the only kind suitable for such work. Molten lead is also used in the bottom of galvanizing pots or in the outer compartment of double galvanizing pots to distribute heat more uniformly and prolong the life of the pots.

XII.

USE OF LEAD IN INERTIAL APPLICATIONS

Lead is frequently used as a counterbalancing weight in many moving components of machinery, as weights or ballasts. This is because of its highest density ( I 1.34 g/cm') among the common metals. The low cost and ease of fabrication into almost any desired shape makes it attractive for this application. Lead weights concentrate the greatest weight in the smallest practical volume and c m be made in the most convenient shape without difficulty and at low cost. Powder metallurgy tungsten components and other highdensity metals may be preferred to lead in some situations, depending on the operating temperature and loading conditions.The low melting point makes lead easy and economical to cast, and where the design is such as to make other methods of fabrication preferable, weights may be extruded or stamped from a sheet. The majority of these applications would tend to use lead-antimony alloys with adequate mechanical properties. There are numerous applications of lead as weights, suchas balances for machinery, locomotive and train wheels, automobile wheels, antiaircraft guns, divers' equipment, industrial trucks, airplane control surfaces, and propellers. Figure 66 presents the application of lead as a compact weight to balance a forklift. The famous Leaning Tower of Pisa is one of the well-known uses of lead in an inertial application (Fig. 67). The landmark that was leaning dangerously was shored up by using lead blocks on the sides of the tower near the base. Its life has now been extended to beyond the 2 1 st century. A modern application of lead is in a high-density computer disk drive such as the one shown in Fig. 68, where it has been used in the balancing of the spindle. Lead in very thin foil form is used in the drive. Therefore, remember when

Chapter 4

548

(b) Figure 66 (a)ForklifttruckfromHyster Co. of Danville, Illinois, and (b) innovative lead counterweight m the forklift in (a). (Courtesy of Vulcan Lead, Milwaukee, WI.)

you are sitting in front of a computer that lead is used from soldering of the printed circuit board components to balancing of the spindle and the damping of vibrations in disk drives. The use of lead in fishing weights is not encouraged.

Applications of Lead

549

Figure 67 The Leaning Tower of Pisa, where lead is used to shore up the landmark structure and extend its life beyond the twenty-first century. (Courtesy of Dr. V. Ramachandran, Salt Lake City.)

Figure 68 A computerdiskdrivewhere high precision lead sheets are used for balancing high-speed spindles. (Courtesy of Maxtor Corporation, Longmont, CO.)

550

Chapter 4

XIII. SOLDERS A.

Introduction

Soldering is one of the major joining processes. Solder material is a material that has a melting point that is lower than that of the parts that are being joined. The molten solder is introduced in the gap between the parts to be joined, completely wetting the surfaces to be joined. Soldering process temperatures are less than 500°C. A strong bond is formed as the molten liquid solidifies, by a combination of mechanical interlocking, interdiffusion across the bond line, and/or a chemical reaction. Soldering presupposes the direct contact of the basis material and the solder without a separating oxide layer. Oxide layers are removed using fluxes. Solders play an important role in the packaging of integrated chips and assembly of components on the printed circuit board. Solders are used in the production of low-cost reliable light bulbs, car radiators, and electronics for television, radio, audio-video recording,computers,automotive ignition systems,telephones, typewriters, and virtually an endless variety of other business, commercial, and industrial products [4 101. The most commonly used solder alloys are composed of tin and lead. When lead is combined with tin, the resulting solder alloys have a unique combination of properties that include low melting point, good strength and ductility to withstand thermal cycling, and ability to flow easily into capillary spaces between metal surfaces. Whether the parts being soldered are for an electronics printed circuit board assembly or a copper heat exchanger, the ductile nature of the solder effectively absorbs differences in expansion rates better than any other bonding material. In addition to various percentages of tin and lead, solder alloys may also include other metals such as antimony, silver, copper, zinc, cadmium, indium, and bismuth. These metals can affect solder properties such as corrosion resistance, strength, hardness, melting point, and service operating temperatures. Obtaining a reliable soldered joint requires a proper joint design, the correct solder alloy and flux for the job, cleanliness of the surfaces to be joined, sufficient heat to the parts to allow the solder to flow properly, and the removal of the flux residue. The choice of whether to use soldering, brazing, or welding to join the different components depends on requirements for joint strength, end use, operating temperatures, and production costs.Thesolder process may be selected over alternative joining methods such as adhesive bonding, welding, brazing, or mechanical joining, because it offers several advantages, as follows. The solder process can be easily and economically automated with a low-capital-expense outlay. Low-energy input is required for soldering, and joint reliability is high. Solders with various melting ranges can be selected

Applications of Lead

551

to fit the application. Sequential assembly is possible. Solders have good thermal and electrical conductivity. Solder joints are impermeable to gas and liquid. Joints are easily repaired and reworked. Precise control is possible over the amount of solder used. A long self life is common. A variety of heating methods can be used. Solder alloys can be selected for service in differing environments.

B. The Tin-Lead Alloys As mentioned earlier, tin-lead alloys are the most widely used of all solders. Most of the tin-lead solders commonly used are in the hypoeutectic range and therefore melt over a range of temperatures, and between these temperatures, part of the solder is molten and part is solid; thus the solder has a pasty consistency. The surface tension of molten solder increases with tin content, and has the advantage in terms of speed of work and quality of the joints. An increase in tin content, however, increases cost. Table 25 gives the melting characteristics of some tin-lead solders and lists their typical applications [410]. When referring to tin-lead solders, the tin content is customarily given first (e.g., 40/60 refers to 40 wt.% tin and 60 wt.% lead). The difficulties of obtaining tin during World War l1 in a number of countries led to the efforts for developing tin-economy solders. For example, part of the tin was replaced by other low-melting elements such as cadmium, bismuth, antimony, thallium, or phosphorus. Some of these efforts led to the development of lead-silver alloys and other low-tin or tin-free solders used in different applications. Table 26 lists the different forms of tin-lead solders which are available 14101. Figure 69 shows the different commonly available forms of tin-lead solders 14101. Tables 27-30 list other commonly used solders which contain Ag, In, or Bi. For the electronics industry, silver is added to tin-lead solders to reduce the dissolution of silver from silver alloy coatings. Silver may also be added to improve creep resistance. Tin-silver alloys are often used for delicate instrument work and food service equipment where operating temperatures are high. Tin-lead-silver alloys exhibit good tensile, creep, and shear strengths. Some are used for higher-temperature bonds in a sequential soldering operation. Fatigue properties are also better than the nonsilver alloys. The tin-97.5% lead-1.5% silver alloy finds use in cryogenic applications because of its high lead content. It is also used to solder tine copper wires, ascopper isnot readily dissolved by lead. Tin-antimony and tin-silver solders are ideal for joining stainless steel used for food handling equipment and decorative items. Tin-antimony solder is used in many refrigeration, plumbing, and air-conditioning applications because of its good creep and fatigue resistance.

Table 25 Melting Characteristics and Applications of Tin-Lead Solders [4 101. (Courtesy of Lead Industries Association, New York.) Composition (wt.%)

Temperature ("C)

Solder alloytinfiead

Tin

Lead

Solidus

Liquidus

Pasty range

2/98 5/95 10190 15/85 20180

2 5 10 15 20

98 95 90 85 80

316 305 268 227 183

322 312 302 288 277

6 7 34 61 94

25/75 30/70 35/65 40160

25 30 35 40

75 70 65 60

183 183 183 183

266 255 247 238

83 72 64 55

45/55 50/50 60140

45 50 60

55 50 40

183 183 183

227 216 190

44 33 10

63/37

63

37

183

183

0

Uses Side seams for can manufacturing For coating and joining metals For coating and joining metals For coating and joining metals For coating and joining metals; for filling dents or seams in automobile bodies For machine and torch soldering For machine and torch soldering General purpose and wiping solder Wiping solder for joining lead pipes and cable sheaths; for automobile radiator cores and heating units For automobile radiator cores and roofing seams For genera1 purpose; most popular of all Primarily used in electronic soldering applications where low soldering temperatures are required Lowest melting (eutectic) solder for electronic applications

3 2 ?! P

Applications of Lead

553

Commercial Forms of Tin-Lead Solders [410]. (Courtesy of Lead Industries Association, New York.)

Table 26

Pig Cakes or ingots Bars Paste Segment or drop Foil, sheet, and ribbon Wire-flux cored

Preforms

Available in 20-, 40-, SO-, and 100-lb size Rectangular or circular in shape, weighing 3, 5 , and 10 Ibs Available in weights from to 2 Ibs Available as a mixture of solder and flux in paste form in quantities of 1 Ib or more Wire or triangular bar cut into pieces or lengths of any desired number Supplied in various thicknesses and widths Solder can be cored with organic, inorganic. or rosin fluxes, 0.010-0.250 in diameter on spools, weighing I , 5 , 20, 25, and 50 Ibs or in bulk packs A wide range of custom-designed preform shapes is available; each shape is a derivative of one or more of the following four most common shapes: wire, punched parts, spheres, and flux-coated metal forms

Bismuth-containing solders, the so-called fusible alloys, are used for soldering operations where a low soldering temperature (below 125°C) is required. These alloys require very corrosive fluxes. Indium alloys are primarily used for soldering at low temperatures and where reduction in gold scavenging is desired. They are also extremely ductile, making them suitable f o r use in areas where there is a thermal mismatch. Other special alloys include zinc-aluminum and tin-zinc, which are used to solder aluminum in order to minimize potential corrosion in the joint. Although solder is not noted for its mechanical strength, strong joints can be made through the selection of solder alloys and proper joint design. The joint should be designed so that the strength of the solder joint is equal to or greater than the load-bearing capacity of the weakest member of the assembly. The lack of strength of solder can be compensated by shaping the parts to be joined so they engage or interlock. The joints can be designed to take advantage of the mechanical properties of the base metal by using such techniques as lap, flanged butt, or interlock joints, as shown in Fig. 70 14101. The solder is then required only to seal the assembly and provide the needed rigidity. Soldered joints are designed to perform one or more tasks that include providing structural integrity, electrical conductivity, or an effective seal. Additional factors to be considered in joint design are the alloy to be used, the heating method used for soldering, fabrication techniques prior to sol-

554

Chapter 4

Figure 69 Different forms of tin-lead solders [410]. (Courtesy of Lead Industries Association, New York.)

Table 27 Compositions of Silver-Bearing Solders [410]. (Courtesy of Lead Industries Association, New York.) Composition (wt.%) Lead 2

Tin 1 62 10

96.5 95

247

97.5 36 88

-

("C)Temperatures

Silver

Solidus

Liquidus

Pasty range

1.5

309

309

22 1 221

268 22 1 245

Eutectic 10 21 Eutectic 24

2 3.5

5

555

Applications of Lead Table 28 Low-Temperature Solders [410]. (Courtesy Association. New York.)

Temperatures ("C)

Composition (wt.%) Tin 12 17 15.5 42

of Lead Industries

Lead

Bismuth

Indium

Solidus Liquidus

18

49 57 52.5 58

21

58 79

-

32 -

26 -

95

-

138

range Pasty

58

Eutectic Eutectic Eutectic Eutectic

7Y 95 138

Table 29 Tin-Antimony Solders 14101. (Courtesy of Lead Industries Association, New York.)

emperatures (wt%) Composition

("C)

dus Antimony Tin 95

range

5

240

8

232

Table 30 Tin-Lead-lndiunl-Silver Association, New York.)

Pasty

Solders [410]. (Courtesy of LeadIndustries

("C) Temperatures (wt%) Composition Indium Tin

Liquidus Solidus Silver Lead

Pasty range

50

50

-

-

118

-

50

-

-

5

50 92.5

124 285

2.5

125 209 305

7

85 20

556

Chapter 4

Figure 70 Joint designs for increasingthestrength [410]. (Courtesy of LeadIndustries Association, New York.)

dering, the number of items to be soldered, the method of applying the solder, and in-service requirements of the part after joining. A particularly significant area of concern in designing joints is to provide for introducing solder into the joint. For example, if the joint clearance is too small, this frequently leads to flux entrapment, inadequate solder flow, and a number of voids in the joint. On the other hand, if joint clearances are too wide, capillary flow of the solder filler metal is impaired; if the joint is heated too vigorously, the solder runs out or leaves only a bridge at the edge of the opening. Generally, optimum clearance in lap joints is about 0.075-0.125 mm to provide propercapillary flow of the solder and to ensure flux removal from the joint. C.

Precleaning and Surface Preparation

Oil, film, grease, tarnish, and other soil will interfere with soldering. A clean surface is required to ensure a sound and uniform quality soldered joint. Fluxing alone cannot substitute for adequate precleaning. The two general methods of cleaning are chemical and mechanical. The most common of these are degreasing, acid cleaning, mechanical cleaning with abrasives, and chemical etching. 1.

Degreasing

Either solvent or alkaline degreasing is recommended for the cleaning of oily or greasy surfaces frequently encountered prior to soldering. Of the solvent degreasing methods, the vapor condensation of halogenated hydrocarbon-type solvents probably leaves the least residual film on the surface.

Applications of Lead

557

However, with increasing concern for the environment, the use of such chemicals is on the wane. The cold articles to be degreased are suspended above the boiling solvent, causing the vapor to condense on the articles and drain back into the boiling liquid. Only clean, freshly distilled solvent contacts the material to be cleaned, so there is no recontamination to hinder the degreasing. In the absencc of vapor degreasing apparatus, immersion i n liquid solventsor in detergent solutions is often a suitableprocedure.The efficiency of this clcaning method can be considerably enhanced by incorporating ultrasonic cleaning. Alkali detergents are also used for degreasing. In general, a 1-3% solution of trisodium phosphate and a wetting agent is satisfactory. These cleaning methods are especially designed for substantial volume.

2.

Acid Cleaning

Acid cleaning, or “pickling,” is used to remove rust and oxide scale from the metal. Hydrochloric, sulfuric, orthophosphoric, nitric, and hydrofluoric acids can be used, either singly or mixed for acid cleaning. Hydrochloric and sulfuric acids are the most commonly used. An inhibitor is sometimes used to prevent pitting once the scale has been removed. The articles should be thoroughly washed in hot water after pickling and dried as quickly as possible. For many electronicapplications, such as printed circuit boards and component leads, special, mild proprietary surface cleaners and solutions are available. Mechanical preparations with abrasives are commonly used for cleaning. These may involve grit or shot-blasting, mechanical sanding or grinding, tilling or hard sanding, cleaning with steel wool, wire brushing, or scraping with a knife or shave hook.

D.

Plating

Plating of tin-lead, tin, copper, cadmium, gold, silver, tin-nickel, and other commonly used materials can provide a suitable surface for soldering. For example, i n the soft soldering of steel, wetting by the solder and the formation of the alloy is difficult. Wetting is attained by “tinning” the steel surface prior to soldering.

E.

Fluxing

One of the most critical steps in soldering is the selection of the proper flux t o ensureasatisfactorysoldered bond. When exposed to thc atmosphere, most metals react to form compounds on their surface. The most common

Chapter 4

558

compoundsfomled are oxides, sulfides, and carbonates.The thickness of these compound films is usually determined by the length of time during which the metal has been exposed to the atmosphere. Increased amounts of either moisture or heat, or a combination of both, tend to increase the compound buildup even though in many cases it may not be visible. The rate of formation and the tenacity of these surface compounds vary with each base metal. It is necessary to remove the nonmetallic compound film from the surface of metals and keep it removed during the soldering operation in order to ensure a “clean” metal surface. The chemical agent used to remove compounds from the surface of metals during the soldering process is called a soldering flux. Ideally, the flux selected should be chemically active enough to remove the surface compounds, stable enough to prevent oxidation of the metal during soldering, and leave a residue which is noncorrosive and nonconductive. There are four general classes of fluxes in common use.

1.

InorganicFluxes(Most

Active)

Inorganic-type fluxes are comprised of one or more inorganic salts such as zinc chloride and ammonium chloride dissolved in water. They are the most corrosive and conductive of all fluxes and are effective on all common metals except aluminum and magnesium. Such fluxes are used for nonelectrical soldering and are not suitable for use on electrical assemblies because they are highly corrosive and conductive. The residue should be completely removed with water. A more thorough cleaning method involves dipping the parts in a 2% hydrochloric acid bath to dissolve the flux residue, followed by a water rinse.

2.

OrganicFluxes(Moderately

Active)

Organic-type fluxes are comprised largely of organic acids such as citric, glutamic, or lactic acids dissolved in water or alcohols. These fluxes are less active than inorganic fluxes and more active than rosin fluxes. The organic fluxes used for electronics soldering must be removed with water to prevent corrosion. 3.

RosinFluxes(LeastActive)

Rosin is the base for fluxes used for electronics soldering. It is produced from pine trees and is unique because it becomes active asa flux when heated and returns to an inactive state when cooled. Rosin fluxes may contain special activating agents to improve their soldering performance.

Applications of Lead

4.

559

No Clean Fluxes

Other organic acids, such as adipic or stearicacids, which are not water soluble, are often used by themselves or in combination with rosin to make up the no-clean fluxes for electronics soldering. These fluxes consist of 9598% solvent and/or water and leave a very small amount of residue. Rosin and the no-clean fluxes are often not removed from the soldered assemblies. Fluxes can be supplied as liquid, paste, solid, or combined with solder in core solder or solder paste. Table 31 provides information on the solderability of different metals and alloys and the recommended fluxes for use with different metals [410].

F. The Soldering Process

In addition to surface preparation, solder selection, and fluxing, another important part of the soldering process is choice of the best heating method. The sources of heating include soldering iron, a gas flame, a molten hot-dip bath, induction heating, ultrasonic soldering, resistance heating, and infrared heating. A common method of soldering is by means of a soldering iron or bit. They maybe heated electrically by direct flame or by oven. Maximum surface area of the heated tip should contact the base metal during soldering. In making a joint, the solder itself should not be melted upon the tip of the iron. If flux-cored wire is being used, such a practice will destroy the effectiveness of the flux. A large variety of size and design irons is available, from a small pencil size to special irons or bits which weigh 2.25 kgs or more. The selection of the iron depends on the task and how much heat is needed at the joint, with the heat recovery time of the iron being fast enough to keep up with the job. Plain copper tips and iron-coated tips are commonly used. Both types must be kept well tinned (coated with molten solder) during use. Oxidized iron tips should never be filed because the thin electrocoating will be removed and the tip ruined. Where fast soldering is necessary, a flame or torch is frequently used. Fuel gases that are used include acetylene and propane. In hot-dip soldering, the parts are dipped and withdrawn from the liquid solder bath, leaving behind enough solder at the joint gap. It is necessary to use jigs or fixtures to contain the unit and keep the proper clearance at the joint until solidification of the solder is completed. Electronic components are commonly soldered to printed circuit boards by wave soldering, an automatic process where the assemblies pass across a wave of molten solder, completing hundreds of soldered connections simultaneously. A similar method is “drag” soldering, where the soldering is accomplished by floating the printed circuit

Table 31

Metal Solderability Chart and Flux Selection Guide [410]. (Courtesy of Lead Industries Association, New York.) UI Q,

Rosin fluxes, no-clean fluxes

0

Nonactivated

Mildly activated

Activated

Organic fluxes, water soluble

Inorganic fluxes, water soluble

r/

J

1/

J

Not recommended for electrical soldering

Metals

Solderability

Platinum Gold Copper Silver Cadmium plate Tin (hot dipped) Tin plate Solder plate

Easy to solder

Lead Nickel plate Brass Bronze Rhodium Beryllium copper

Less easy to solder

Galvanized iron Tin-nickel Nickel-iron Mild steel

Difficult to solder

Not suitable

r/

Chromium Nickel-chromium Nickel-copper Stainless steel

Very difficult to solder

Not suitable

Not suitable

Aluminum Aluminum-bronze

Most difficult to solder

Not suitable

Not suitable

Beryllium Titanium

Not solderable

Not suitable

Special flux and/or solder

J

J

Applications of Lead

561

assemblies on a bath of molten solder. Both of these techniques may be highly automated, incorporating a fluxing station, preheating or drying station, soldering station, and cleaning. Automatic mass soldering speeds can range from 0.6-4.8 m/min (2 to 16 ft/min.). Modem mass soldering machines offer adjustable tracks, variable carriers, and a variety of options to accommodate a large cross section of tasks to be accomplished. The next section presents information on the type of soldering joints encountered in electronic printed circuit boards and methods used to make such joints. Induction heating may be employed in soldering operations in cases of large-scale production of simple joints which lends itself to mechanization and requires application of heat to a localized area, minimum oxidation of surface adjacent to the joint, good appearance, and consistently high joint quality. The only requirement for a material that is to be induction soldered is that it be an electrical conductor. Three types of equipment are available for induction heating: the vacuum-tube oscillator, the resonant spark gap, and the motor generator unit. Resistance heating using carbon electrodes is also employed in soldering. Production assemblies may utilize multiple electrodes, rolling electrodes, or special electrodes, depending on which will be advantageous with regard to soldering speed, localized heating, and power consumption. Resistance soldering electrode bits cannot generally be tinned and the solder must be fed directly into the joint. Oven heating is considered (1) when entire assemblies can be brought to the soldering temperature without damage to any of the components, (2) when production is sufficiently great to allow expenditure for jigs and fixtures to hold the parts during soldering, and (3) when the assembly is complicated in nature, making other heating methods impractical. Infrared (IR) heating using a quartz-iodine and tungsten filament lamp is also widely used in soldering because it is very stable and reliable over a wide range of temperatures. In general, infrared heating systems are simple and inexpensive to operate. The IR heating process provides process repeatability, ability to concentrate or focus the energy with reflectors and lenses, economy of operation, and lack of contact with the workpiece. Ultrasonic soldering is also employed in soldering operations. It can be considered a form of dip soldering in which the workpiece is immersed in a tank of molten solder. When a properly designed transducer (source of ultrasonic energy) is energized in a bath of molten solder, it produces cavitation in the region around the end of the transducer. Aided by the solvent action of the molten tin, the cavitating solder actually scrubs, attacks, and removes the surface compounds and soils found on the workpiece, much as a flux would do in the usual solder operation. After cleaning, which takes only a fraction of a second, solder wets the clean metal and is deposited on

562

Chapter 4

it. The thickness of the deposit is a function of immersion time and solder temperature. Ultrasonic soldering allows fluxless soldering and enables the soldering of metals otherwise considered difficult to solder, such as Kovar, nickel alloys, and aluminum.

G. Solder Joints in Electronic Assemblies Electronic packaging and interconnection involve either (1) the through-hole technology or (2) surface mount technology (SMT) [411-4131. Throughhole technology involves pin connections on to the printed circuit board (PCB), as shown in Figure 71 [41l]. The electronic components such as resistors, capacitors; transistors, anddual-in-linepackages (DIP) that are

Figure 71 Through-hole pin connections on to the PCB [41 l]. (Courtesy of ASM International, Materials Park, Ohio.)

Applications of Lead

563

connected to the PCB through connector pins use this technology.The lands to which connections are made are constructed of copper foil (17-71 km thick) bondedto the laminate. Surface lands may be electrodeposited or electroless deposited. Solder assembly techniques used are hand soldering and automated processessuch as dip, drag, or wave soldering.Surface mount technology (SMT), on the other hand, involves placement of surface-mount components into smaller and tighter PCBs. The increased in packaging density leads to lighter, small, and high performance components at low cost. Figure 72 illustrates the different interconnect techniques [413]. There are at least three chip level connections commonly used in the industry. They are (1) wire bonding using thermocompression or ultrasonic bonding, (2) tape automated bonding (TAB) using thermocompression bonding or pulsethermode reflow, and (3) controlled collapse chip connection (C4). The lead frame is the component of the electronic package that provides the platform for attachment of the semiconductor chip, and a series of metal leads and connections points to carry the electrical signal, voltage, or ground potential from an area inside the final package to the outside world. In wire bonding, a gold wire, 17.5-32.5 km in diameter, is strung through a heated capillary (200-500°C). A ball is created at the end of the wire by a flame or spark. The ball is brought in contact with a metal bond pad, and through the application of compressive force and ultrasonic energy, a metallurgical bond is formed (Fig. 73) [412]. The other end is soldered to the lead frame or directly to the metal pad on the PCB. The attachment of the semiconductor chip directly to the PCB can be accomplished through TAB or a flip-chip, eliminating the need for a lead frame or package. Gold bump (Fig. 74) [413] formed using liquid photoresists on the chip is soldered to the tinned copper tape and the tape is soldered to the pad on the PCB through

Ribbon Flip.Chip

I I

lW(W.6) lW(ll%)

I I

62 100

Figure72 Different interconnect techniques [413]. (Courtesy of Kluwer Academic Publishing, Norwell, MA.)

564

Chapter4

bottle neck capillary

I

I

Figure73 Wire bonding to chip [412]. (Courtesy of Kluwer Academic Publishing, Norwell, MA.)

Figure 74 Gold bump formed on the chip using liquid photoresist. The wire or tape connection is made to this tab by solder. (Courtesy of Kluwer Academic hblishing, Norwell, MA.)

Applications of Lead

565

Figure 75 The soldering of the tinned copper tape to the chip and the soldcring of tape to the pad on the PCB through the rcflow of the solder bumps (4121. (Cowtcsy of ASM International, Materials Park, Ohio.)

the reflow of the solder bumps (Fig. 7 5 ) [4121. The lead pitch capability for TAB connections is about S0 pm. In C4 technology, solder bumps are first formed on the chip (Fig. 76) 14121. Bumps S pm i n diameter and 20 p m in height with a pitch of I O k m can be formed on the chip. After the bumps are formed, the chip is placed upside-down on the PCB or substrate and soldered by the reflow of the solder on heating and subsequent solidification (Fig. 77). The application of solder bumps are made by a screen-printing process. A fine wire mesh coated with photoimaged emulsion to define the opening and masked areas is used. For tiner dimensions, a stencil may be used directly. A squeegee is moved along to force the solder paste containing tine spherical solder-alloy (85-92 wt%) particles and flux vehicle. Figure 78 shows the screen-printing of the solder paste bump on a substrate [41 I ] . Rosin fluxes have been used very widely in electronic assembly in the past, as it has many desirable properties. It delivered a proper amount of reactivity at common soldering temperatures, yet is nonreactive at room temperatures. It is an excellent tackifier and, thus, capable of holding electronic componentsonto the board before permanent solder joints can be formed. However, the need for chloroflurocarbon (CFCI-based solvents, has made these less attractive.The use of CFC as a solvent in cleaning flux residues has come to an end. Two types of non-CFC fluxes filling the role of rosin-based fluxes are water soluble and no-clean fluxes.

566

Chapter4

Figure 76 Solder bumps on the siilicon wafer chip in C4 technology [412]. (Courtesy of Kluwer Academic Publishing, Norwell, MA.)

H. Mechanical Propertiesof Solders The tensile strength of lead-tin alloys increases with increasing tin content. The elongation at fracture is very high over the whole range of concentration, with a maximum possibly present at intermediate tin contents. The minimum in the neighborhood of the solubility limit on the lead side presumably disappears if the alloys soften on storage. An antimony content of 5-6% of the tin content raises the strength by 10-20%. In the alloys that contain antimony, a transientagehardening occurs before the softening.

_"""" " - "- "-"- --- Silicon I.C. - ---

" " " "

AI

cu Au

-

II \U

Figure77 The reflow of the solder to make a joint in C4 technology [412]. (Courtesy of ASM International, Materials Park, Ohio.)

567

Applications of Lead

Nozzle

I

-. f&+h

M I

SUbStntO

Screen (Stencil) Printlng

Figure 78 Screen-printing of solder bumps on asubstrate [41 l]. (Courtesy of ASM International, Materials Park, Ohio.)

Measurements of the shear strength of cast specimens exhibited a steeper rise up to 30% Sn, then a more or less shallow rise up to 60%Sn. The notch bar strength had a maximum at tin content of 35-40%. The creep strength of alloys free from antimony indicated the highest values at the eutectic composition. The creep strength is greatly increased by the additionof antimony. Additionof 0.18% Cu causeda further increase. Small additions of iron, copper,andbismuthhaveno effect. The creep strength of solders with and without antimony fell at 80°C to 20-30% of that at room temperature. Table32 summarizes the mechanical and physical properties of different soft solders [410]. Other property data on solders have been presented in Chapter 2. 1.

EnvironmentalPressures

Health and environmental concerns have led to efforts to find lead-free solders for electronic applications. The possibility of human contact in this application is recognized. However, no other material substitute offers the great combination of properties provided by lead-tin-based solders, and the use of lead in electronic component assembly is likely to continue. Thus the complete recovery and recycling of Iead from electronic circuit boards becomes a more important issue. The use of solders in water pipes has now been banned in most countries. Careful evaluations of applications where lead solders may come in contact with human beingsor groundwater sources are needed.

Ul Q)

0)

Table 32 Physical and Mechanical Property Data on Solders [410]. (Courtesy of Lead Industries Association, New York.) Tensile strength (MPa)

Shear strength WPa)

Specific gravity (glcm')

Lead 5/95 SnPb 10190 SnPb 15/85 Sn/Pb 20180 Snpb 25/75 Sn/Pb 30ffO Snpb 35/65 SnPb 40160 SnPb 45155 SnPb 50150 Sn/Pb 60140 Sn/Pb 63/37 SnPb Tin 95 Snl5 Sb 95 SnJ5 Ag 62 Snf36 Pb12 Ag 10 Sn/88 Pbl2 Ag 96.5 Sn13.5 Ag

12.30 28.96 32.48 34.56 35.94 37.32 39.74 41.82 42.85 42.85 44.58 44.23 46.3 1 12.44 40.78 69.8 1 46.3 1 33.87 59.44

12.44 20.73 26.96 30.89 32.76 36.70 38.01 38.64 39.26 39.53 40.57 39.40 41.88 17.69 42.85 58.06 43.20 29.72 52.87

1 Snl97.5 PbI1.5 Ag

24.88

24.88

Alloy (wt.%)

B ri nel1 hardness

Electrical conductivity (% of copper)

Elastic modulus (GPa)

11.34 11.06 10.44 10.50 10.23 10.00 9.74 9.50 9.29 9.08 8.88 8.5 1 8.41 7.29 7.26 7.42 8.42 10.75 7.3 1

4.0 9.0 11.0 11.3 11.5 11.5 11.2 11.0 10.5 10.6 11.0 12.0 12.0 5 .0 14.0 18.0 16.0 12.0 17.0

7.9 8.0 8.2 8.4 8.7 8.9 9.3 9.8 10.1 10.4 10.9 11.3 11.5 13.9 11.9 14.0 11.6 8.4 14.0

18.04

11.28

11.0

8.8

Surface tension (290°C) (10" N/m)

19.08 20.04

467

2 1.08

470

23.08

474 476

30.07 42.23 50.80 23.57 19.35

490 545

3m

2 2

P

Applications of Lead

XIV.

569

AMMUNITION

The high density of lead and its low cost had always made it attractive for use in bullets and lead shot. It allows attainment of the high momentum necessary for a maximum striking power and accuracy and decreases the surface area against which the air resistance can act. In 1997, about 6% of the lead produced in the world was used in the production of ammunition [372]. Shot up to 6 mm in diameter can be made in shot towers. The method ofmanufacturing shot in towers was invented in 1782 by Watts 12,3381. Watts was a plumber in Bristol, England and, apparently, he had a dream one night that he was out in a rainstorm but that it was raining lead instead of water and the drops of lead were perfectly spherical like raindrops! The next morning he decided to try the experiment and poured molten lead from the tower of St. Mary Redcliffe Church into a water tank below. The rest is history [338]! This technique was briefly described in the Chapter 2. Molten lead is poured from the top of the tower through a pan perforated with holes smaller than the shot desired. The necessary height of the pouring floor in the tower depends on the maximum size of the shot to be poured; the larger the shot to be made, the higher must be the pouring floor. The bottom of the pan is covered with a sludge of oxidized lead, so that the molten metal will ooze slowly through and form round drops. Small amounts of arsenic, up to l%, are added to the lead and this forms arsenious acid, which removes the lead oxide layer and coats the droplet with a thin molten skin of lead arsenite. This allows the lead droplet to more easily assume the perfect spherical shape desired. The lead arsenite solidifies at 200°C after the lead solidified. Modem lead shot has l-2% antimony to increase hardness. The smaller sizes of shot usually contain the higher percentages of arsenic and antimony. As the drops rain down the tower, they solidify and are caught in a tankof water atthe bottom, so that the spheres willnot be flattened on landing. In order to decrease the height of shot towers, an upward blast of air sometimes blows against the falling lead, which has the same effect as a longer fall. After the shot is collected in the water, it is dried and mixed with graphite to polish it and then screened to eliminate odd sizes. It is next rolled down the slope of glass tables which have a narrow trough running along the bottom. The perfectly round shot gather enough momentum to leap this trough, but those slightly flattened are slowed in their descent so as to fall into the trough; they are subsequently remelted. The grading operation is repeated four times. The shot is then loaded into shells and is ready for use. Shot greater than 5 mm in diameter is cast in revolving split-ring molds. The molds are placed around the circumference of a vertical ring several feet in diameter. The lead is poured in at the top and solidifies as it

Chapter 4

570

passes down one side until the split ring opens and drops it out at the bottom. The largest cast shot is about 11 mm in diameter. High-precision shots and other shapes can be made by roll forging of a continuously cast rod or by forging of precut lengths of rolled or extruded rods or wires. Originally, round balls were fired from smooth-bore muskets, but pointed bullets were desired, as they would offer less resistance to the air. However, a pointed bullet fired from a smooth bore simply tumbled end over end and would not stay on its course. It was not until the early part of the 18th century, when a spin could be introduced by rifling, that the pointed bullets were used. Bullet cores are made by swaging of precut lengths of extruded wire and inserting inside a bullet-shaped Cu- IO% Zn jacket. Larger armors will have a steel core and Pb is filled between the steel core and the jacket. It acts as a lubricant and helps steel penetrate the armor. Many different types and sizes of bullets and shot are manufactured for cartridges of a wide array of guns, rifles, pistols, and machine guns. Ammunition for sports and military purposes has up to 8% Sb and 2% As. Modem high-velocity ammunition tends to use depleted uranium. Antimonial lead is used for shrapnel balls, but modem armored warfare has reduced greatly the amount of shrapnel used. Antimonial lead is also employed for practice bombs used by military fliers. They are usually die cast. Ammunition used to train airplane gunners is made from a mixture of lead powder and a plastic. The bullets shatter when they strike the target plane’s special armor, instead of penetrating it. A number of chemical compounds oflead are also important in ammunition. Lead azide is probably most important as a detonator explosive; lead sulfocyanate, nitrate, peroxide, and styphnate may also be employed. Lead-lined vessels are used in the manufacture of nitroglycerin, a powerful liquid explosive highly sensitive to percussive shock 12671. In this case, the lead plays three important roles. The lead lining of various reaction tanks, floors, table tops, and so forth effectively resists the attack of the corrosive acids used in the manufacturing process. The excellent nonsparking characteristic of lead is highly desired. In addition, lead sheet absorbsshock waves and blankets vibration. Therefore, to prevent accidental detonation of the nitroglycerin, it is stored and transported in leaden vessels, which, if dropped or jammed, would not transmit the shock to the explosive.The containers also would deform instead of breaking, thereby preventing the nitroglycerin from spilling.

XV.

LEADCABLESHEATHING

Next to storage batteries, a major engineering use of lead alloys is in cable sheathing. Lead is used in the construction of two general types of electrical

Applications of Lead

571

cables: (1) cable for communication and (2) cable for the transmission and distribution of electric power from public utility generating stations [414]. Lead alloys are used for cable sheathing of high-voltage oil-filled cables for use up to 1 100 kV. It is also used in dry insulated PE, XLPE, and EPR cables, used up to SO0 kV, to eliminate dielectric breakdown under conditions of possible contact with moisture [415,416]. The use of lead in communication cables has declined with the introduction of polyethylene and other polymeric sheathing, but, still, there are significant lengths of lead sheathed cables in service. Lead-covered cables are used both in overhead and underground line construction. In spite of higher initial cost, electrical cables are preferably placed underground, where they will be undisturbed and out of sight while still meeting the service requirements.

A.

Properties Required in Cable Sheaths

The prime function of a cable sheath is to provide an impermeable barrier to prevent access of moisture to the insulated core [2,33 1,4 16-4 181. In the case of oil- or gas-filled cables, the lead sheath is needed for the containment of the oil or gas [416,417]. It is of considerable importance that the sheath be capable of easy manufacture in extremely long lengths and, once applied over the insulated cable core, it should withstand subsequent manufacturing and installation operations without failure. Cable-joining techniques at terminal points and junctions should also be simple and effective. The sheath in power cablesalso needs to meet otherservice requirements such as grounding of the cable and conduction of the short circuit currents. Lead and its alloys meet all the above service requirements and, hence, are widely used in cable sheathing. Aluminum, copper, and composite laminate foils have also been considered because of their low densities and higher thermal/ electrical conductivities [415]. However, lead and its alloys continue to be dominant sheathing materials. Once installed, the cable will be expected to operate without maintenance (if in a duct or buried directly underground) for perhaps 40-50 years. If the sheath is to continue to act for so long as an impervious layer, its resistance to corrosion must be extremely high. As was discussed in Section V of Chapter 2, lead and its alloys have high inherent corrosion resistance in air, soil, and seawater. The corrosion behavior in soils is quite complex. The corrosion rates are influenced by many different variables, including soil composition, presence of stray currents, degree of aeration, cross-bonding, and bacterial activity. The corrosion rates of buried lead cables and structures are presented to a limited extent in Section V of Chapter 2 . To provide additional protection to cables, coatings may be applied, but usually these coating are simpler protective systems and less expensive than that

572

Chapter 4

necessary for any other metallic sheathing material that might be used. The lead alloys behave in the same way as lead; therefore, the cable environment does not influence selection of the lead sheathing alloy. I n addition to the requirements of impernleability to moisture, corrosion resistance, and ease of fabrication, the cable-sheathing material is expected to have good creep resistance, fatigue resistance, and microstructural stability to meet the service conditions. Certain types of power cables, intended for use at 33 kV and above, operate continually under internal gasor oil pressure. Depending on the cable construction, these pressures are of the order of 275- 1380 kPa for oilfilled and low-pressure gas-filled cables, and around 1380- 1725 kPa for high-pressure gas-filled cables [41X]. The internal pressure generates a circumferential tensile stress, which the lead sheath alone is unable to withstand without ultimate failure, although the rate of expansion may be extremely low. It is normal, therefore, to apply metal reinforcing tapes over the sheath. The essential requirement is then that the sheath possesses sufficient ductility to reach the reinforcement without fracture. It is generally accepted that radial or circumferential extensions of the order of 5% maybe necessary before the reinforcement is reached and expansion ceases 14161. Although expansion may take place very slowly, unalloyed lead sheaths will give the required extension. However, some alloys are extremely sensitive to the rate of expansion, and where the time taken to reach the reinforcing tapes is long, failure can occur with very little expansion. In the United Kingdom, even cables operating under low internal pressures are reinforced, and creep ductility is usually regarded as more important than creep resistance. Another way in which lead sheaths may fail is by fatigue due to the repeated application and reversal of stresses or strains that are well below the values necessary to cause failure in a conventional tensile test. There are several sources for the cyclic stresses or strains experienced by the sheath 12,3981. Vibration of the cables operating in the vicinity of machinery or of bridges and roads carrying heavy traftic is a conmon source. With power cables, their normal operating behavior will induce cyclic strains. According to the demand for power, the temperature of the conductors will rise, resulting in circumferential and longitudinal movements of the conductor and insulating medium, which are accommodated by the expansion of the sheath. Theexpansion(and,therefore, the strain) will reach a maximum at peak current demand. At off-peak periods, the sheath will cool and contract to its original dimensions, relieving the strain. Cyclic straining due to temperature changes within the cable typically occurs on a daily frequency. The cyclic stresses arising from external sources will be of unpredictable frequency, but may be as high as several thousand cycles per minute.

Applications of Lead

573

The alloys must also have good structural stability so that its properties do not change with time during service. For example, in the case of agchardened alloys, no overaging should take place. Changes in grain size that can occur due to recrystallization or grain growth is not desirable.

B. Types of Electrical Cable Sheathing In communications cables, the copper conductor core is wrapped with paper and, after careful drying, has a lead sheath extruded over it. The combination of paper and the air space between the conductor and the paper provides the needed insulation. Some of the older cables in service include gas-tilled telephone cables for which lead sheathing provides the containment for the pressurized nitrogen gas i n the cables. The gas-filled cables are divided into sections by means of gas-tight dams. In the case of damage to the cable sheath, the gas pressure drops and, thus, the physical condition of the cable sheath could be monitored. Polyethylene and other polymers started replacing lead a s a sheath material in the sixties because of their lighter weight and corrosion resistance under aggressive soil conditions. Due to good dielectric strength, polymer sheathing also served as the insulation. There are different categories of cables used for the transmission and distribution of electricpower and they vary in size significantly. Unlike telephone cables using a large number of small wires with thin insulation, power cables usually have only one, two, or three conductors, with heavier insulating walls between one another and the outside. Heat is produced during operation by the transmission of current through the conductor, the dielectric losses of the insulation, eddy current losses i n the lead sheath, and eddy current and hysteresis losses in the steel armoring when present. The temperature rise of between 25°C and 50°C could be expected according to the nominal voltage, the higher rise in temperature being associated with low-voltage cables [2]. The thickness of insulation on the individual conductors depends on the voltage rating of the cable, with the heavier walls used at the higher voltages. The thickness of the lead sheath increases with the cable diameter and covers a normal thickness range from 1 to 4.5 mm. The different types of insulation used in the manufacture of power cable include paper, rubber, high-density polyethylene, low-density polyethylene, and cross-linked polyethylene. Rubber, high-density polyethylene, low-density polyethylene, and cross-linked polyethylene are used only for the lowand intelmediate-voltage cables. In paper-lead power cables, the insulation consists of paper that. after application to the cable, is carefully dried in vacuum and impregnated with a mineral oil-resin composition. A lead sheath around the insulation provides the containment for the oil. In multicore cables, the individual con-

574

Chapter 4

ductors are stranded to one another and the bundle is surrounded by a common cover, on which the lead sheath is laid. In addition to the paper-lead cables, lead-sheathed power cables with polymeric insulation are also used in power transmission for operating voltages up to 500 kV [2]. Figure 79 shows a solid-type 15-kV paper-insulatedlead-covered (PILC) power cable made by Okonite [419]. The impregnated paper insulation consists of electrical-grade paper made from sulfate-processed coniferous wood pulp and polybutene dielectric fluid. The paper has high dielectric strength and low dielectric loss. It has the necessary mechanical and physical properties to resist tearing and wrinkling during manufacture and subsequent handling during installation. The impregnating fluid used is a medium-viscosity polybutene type, which is better than natural-petroleumbased insulating fluids as theyresist aging, have lower andmore stable power factor values, and possess an inherenttackiness which resists draining

0-

C-

DE-

F-

Figure 79 Solid-type PILC 15-kV power cable: (A) conductor-strandedcompact round; (B) strand screen-carbon black paper tapes; (C) insulation-impregnated paper tapes; (D) insulation screen-carbon black paper tape;(E) sheath-copper bearing lead; and (F) Jacket-Okolene [419]. (Courtesy of Okonite Co., Ramsey, NJ.)

Applications of Lead

575

of the paper tapes. The copper bearing lead sheath provides an impervious barrier from the environment, mechanical protection for the insulation and encapsulates the impregnant. All lead sheaths have the inherent capacity for substantial electrical conductivity under short circuit conditions without requiring a separate ground. The thermoplastic polyethylene jacket (F) provides mechanical and corrosion protection for the lead sheath. These cables are recommended for use in underground ducts and direct burial and aerial lines when lashed to a messenger. Paper-lead cables are not suitable as solid-type cables for the highest voltages. Fluctuations of temperature produce hollow spaces in the dielectric because the dielectric has a high coefficient of thermal expansion in relation to the lead sheath. Ionization occurs in the hollow spaces in the dielectric and this reduces the quality of the insulation. In order to remedy this, oiltilled cables are predominantly used for voltages above 60 kV. In oil-tilled cables, on electrical loading of the cable, the expansion of the oil occurs due to the increase in temperature. The oil passes from the paper insulation into the hollow space between the individual conductor strands and flows into a closed compensating vessel. On reduction of the load and cooling of the cable, the reverse process occurs. As the oil is always kept under a certain excess internal pressure, air or moisture cannot immediately penetrate the insulation even on mechanical damage. In oil-tilled cables, the insulation can be thinner than i n solid-type cables. Although the solid-type cables reach the limit of their stability at about SO”C, an oil-tilled cable can be permanently operated at temperatures up to 80°C [2]. For the same voltage and conductor cross section, an increase of about 50% in the transmission can be obtained as compared with solid-type cables. For the same thickness of insulation, an increase of 200% in transmission can be obtained [2]. Figures 80 and 81 show some of the high-voltage cables operating above 100 kV that use lead cable sheathing 14201. The dry insulated high-voltage cables appeared in the market around the late sixties. As it was no longer necessary to maintain oil, the impervious barrier was eliminated i n these cables. However, afew years after their introduction, failures started to appear. The dielectric breakdowns occurred when the cable was in contact with moisture and the presence of “water treeing” was observed.The lead sheathing was therefore reintroduced in these dry insulated cables. Figures 82a-82c show a water-impervious XLPE cable with laminated lead as an impervious layer [421]. The design of high-frequency cable departs from that of the communication cable and of the power cable. In these cables, the two conductors are arranged coaxially; thus, one conductor forms the axisof the tubular second conductor. The transmission of high frequencies requires the use of

576

Chapter 4

A

H

CD-

l-

K A Spiral gas duct

B Metallized paper conduc:tor s c reen

E

c

L

Dielectric screen

D Bedding E Anti-corrosion sheath

F

M

F Armour G Servlng

H Conductor

c

I Pre-impregnated paper dielec:tric J Lead-alloy sheath

K Reinforcement L Bedding M Cotton tapes

Figure 80 A gas-filled high-voltage cable operatingat 1 0 0 kV [420]. (Courtesy of Lead Development Association, London.)

insulating materials with particularly low dielectric losses. Plastics with no polar groups such as polystyrene or polythene are used. Buried cables are mostly laid under stone covers in order to guard against mechanical damage from pick axes or other excavation equipment [2]. They are preferably laid on sand. In addition, the lead sheath may be

Applications of Lead A. Copper conductor B. Conductor screen c. Impregnated paper dielectric D. Dielectric screen E. Lead alloy mheath F. Beddingtape G. Galvanimed ateel twist-compsnmating tape8

577

H. Cotton t a p s I. Vulcanised rubber tapes for antl-corrosion protection

J. Cotton tape K. Jute yarn bedding

L. Compounded galvanized mtesl armour wire6 M. Cotton tape N. Jute yarn serving

A B C D E F G H

N

Figure 81 A high-voltage submarine cable operating at 130 kV [420]. (Courtesy of Lead Development Association, London.)

given a protective covering of alternate layers of viscous compound and preimpregnated paper; over this, a layer of preimpregnated jute which is covered with a hard compound is placed. This protective coating should, above all, exclude the chemical effects of the environment. If an additional mechanical reinforcement is required, the cable is armored. Armor is used on buried cables, river and submarine cables, as well as mining shaft cables. Over the protective covering of alternating layers of viscous compound and preimpregnated paper, the lead sheath receives, further layers of a tar-coated steel strip, or flat, round, or profiled wire. Over this, an outer protective covering of asphalted jute is placed. The type of armoring is determined by the magnitude of the tensile stress expected. Cables with galvanized-steelwire armoring are used, among others, as self-supporting cables or as ducted cables when high tensile stresses are expected as a result ofthe greater length of cable to be drawn in or as a result of a distortion of the tube channel. In addition to lead, aluminumand copper have been considered for use as metallic cable-sheathing materials in limited cases. In some places where severe corrosive conditions are encountered or where scoring of the sheath is inevitable, neoprene or polyethylenejacketed cables are being used.These are regular lead-sheathed cables to which a jacket of neoprene or polyethylene about 6.25 mm in thickness is applied by extrusion. Because of the extrusion method used for applying the lead sheath among with other manufacturing facilities such as stranding, insulating, and cabling, it is possible to manufacture cable in long lengths as often required for submarine installations. Where cable is to be pulledinunderground

578

Chapter 4 Water Impervious layer

/

(a) Under-jacket type

Q Conductor @ Conductor shield @ Insulation @ Insulation shield Water lmpervlous layer Holding tape Wire shleld Outer jacket

Water impe'rvlous layer

(b) On-core type

(c) Water impervious layer made of plastic film laminated lead Figure 82 Water-impervious XLPE cable [421]. (Courtesy of Lead Developmcnt Association, London.)

ducts, it is usually supplied in specified lengths corresponding to the distance between manholes. The individual lengths are spliced together toform the complete circuit. In splicing lead-covered cable, a lead sleeve, used to seal the splice, is wiped with solder to the cable sheath at each side of the splice, forming the well-known plumber's joint. Where lead covered cables are used for submarine purposes or for direct earth burial, a metallic armor is normally applied over the sheath for protection against mechanical injury. For submarine cable, this armor usually consists of an asphalt-impregnated jute bedding directly over the lead, followed by a serving of galvanized steel wire armor with a layer of asphalt-impregnated jute yarn over the m o r . Where cable is for direct earth burial, flat steel tapes and 0.2s-mm-thick lead tapes are used in place of steel wire for the metallic armor. Other types of protective covering or modification of the above are sometimes used for special service conditions.

579

Applications of Lead

C.Cable-Sheathing

Alloys

The alloys of lead for sheathing applications have been, for the most part, empirically developed. However, the present severe service requirements have made it essential for the scientific development of these alloys. Various alloying elements such as Sn, Sb, Cu, Te, Bi, Ca, Cd, and As are presently in use, depending on the specific service requirements. These alloying additions improve mechanical properties of lead by solid solution and precipitation strengthening. Their strong influences on grain-boundary mobilities and interdiffusivities make the grain size and microstructure stable and improves creep properties. Of the various alloying elements, Sb, Sn, and Cd have appreciable solid solubilities in Pb and, therefore, could provide solidsolution strengthening as well as precipitation strengthening. Bi has high solubility but no significant influence on strengthening. However, Cu, Te, As, Ca, and Ag have very limited or negligible solubility in Pb. Therefore, their influence on mechanical properties is expected to mainly result from their influence on interdiffusivity and grain-boundary mobility [422]. Early work by Aust and Rutter had shown a dramatic decrease in grain-boundary mobility when ppm levels of Ag, Cu, and Sn were added to zone-retined lead. The second-phase precipitates, because of their low volume fraction, may have only a very limited influence on strength but can influence fatigue properties and ductility. Typical operatingtemperatures of cable sheaths range from OST, to 0.6T,,, where TA, is the melting point of pure lead. The melting temperature of cable-sheathing alloys with extremely low solute content are close to the melting point of lead. Depending on the stress level, power-law creep or diffusional creep is expected to be dominant in the cable sheath. A wide range of production and service conditions, lead ore sources, and noninteraction among various cable manufacturers of different countries have generated a large number of cable-sheathing alloys that are in service. Recent efforts have been made to minimize the number of standard alloys by scientific development of a few multipurpose alloys. Table 33 lists some of cable-sheathing alloys and their typical application. Among these, Alloy E, Alloy 1/2C, Alloy 1/2B, F3 alloy, 1/2F3 alloy, and Pb-Cu-Te alloy are quite popular [8,422-4281. Thereseems to be consensus that Pb-Ca-Sn alloys are good. However, even the most daring manufacturer is unlikely to specify the alloy in demanding application without a 20-30-year field trials. SSuMT alloy (Pb-0.3wt.% Sb-0.02wt.% Cu-0.03wt.% Te) and other SSuMt-based alloys containing lower levels of Sb, Cu, and Te are popular in Russia. Recent standardization efforts in the European Union has led to the development of CEN 306 standards for Pb cable-sheathing alloys as well as

Table 33 Compositions of Commonly Used Cable-Sheathing Alloys Alloy name

Nominal composition

B

Pb-(O.8-0.95)%

1/2B" C 1/ 2 c

Sb

Applicable

Equivalent

national standards

CEN 306 designation"

BS 801

PBOO 1K

Pb-0.55 Sb

BS 801

Pb002K

Pb-(0.35-0.45)% Sn(0.12-0.18)% Cd Pb-(O.18-0.22)% Sb(0.06-0.09)% Cd

BS 801

PBOllK

BS 801

PBO 12K

E

Pb-(0.35-0.45)% Sn(0.15-0.25)% Sb

BS 801

PB02 1K

Pb-Cu Pb-Cu-Te

Pb-(0.04-0.05)% CU Pb-(0.03-0.04)% CU(0.03-0.04)% Te Pb-0.15 As-0.15 Sn0.1% Bi

DIN 17 640 AFNOR NF C32 050

PB06 1K PB04 1K

F3

Pb-Ca-Sn

Pb-0.033 Ca-0.38 Sn

PB03 1 K

PB05 1 K

cn Q)

0

Applications Solid-type cables and telecommunication cables subjected to severe vibration conditions Solid-type cables and telecommunication cables subjected to severe vibration conditions Power cables in ships; acceptable for most types of cables Oil-tilled and submarine power cables; power cables subjected to severe vibrations in service; acceptable for most types of reinforced cables Solid-type power cables, telecommunication cables, and reinforced gas or oil-pressurized power cables under moderate vibration conditions Gas or oil-pressurized power cables Cables subjected to high vibrations and oil-filled cables PILC cables, submarine cables: power cables where creep resistance or bending resistance is required: power cables exposed to severe vibrations Long high-voltage DC and AC submarine cables

Nore: Refer to Chapters 2 and 3 for alloy property data. "The CEN 306 specifications of composition may slightly differ from the equivalent existing BS, DIN. AFNOR and other specifications. The applicable CEN standard for lead to be used in preparing the alloy is specified. hThe number in designation Alloy B refers to the reduction of principal alloying elements by nearly half of the Alloy B. Similar noles apply for 1/2C. and other similar designations.

9 0)

'0, P

581

Applications of Lead Table 34 CEN 306 Designations for CableSheathing Alloys and Their Common Trade Names

Common alloy name New

CEN 306 designation

PBOO I K PB002K PBOl IK PBOl2K PB021 K PB022K PB023K PB03 I K PB032K PB041 K PB042K PB043K PB05 I K PB06 1 K PB071K

B 1/2B C l /2c E EL I /2E F3 1/2F3 CU-TC 112 Cu-Te 114 Cu-Te Pb-Ca-Sn

Pb-Cu Pb-Te

Pb alloysforotherapplications 1429,4301. Table 34lists the CEN alloy designations and the common names of equivalent lead alloys. Compositions of the lead to be used for the production CEN 306 cable-sheathing alloys are shown in Table 35. It must be mentioned that the choice of an alloy is determined by the track record. The ability to continuously extrude long lengths of defect-free and homogeneous sheaths is a most important consideration. Freedom from inclusions is important as they can be focal points for electrical breakdown and perforation. Delivery of inclusion-free melts is assured through ( l ) the use of baffles in the melting pot, (2) the use of tapping from bottom, (3) the

Table 35 Specifications of Pb Used i n NewCEN 306 Designation Alloys (4291 Alloy

Sb

Sn

Cd

As

Te

Ag

Cu

Bi

Zn

Ni

Pb

582

Chapter 4

use of larger ingots for melting, and (4) filters. Segregation or formation and accretion of precipitates on the extruder screw surface and its subsequent incorporation in the sheath also needs to be avoided through the choice of alloy composition and process design and control.

D. Production of Cable Sheathing The extrusion process for cable sheathing was introduced in Chapter 3. Further details of the cable-sheathing process are presented here [422]. Cablesheathing alloys are prepared at lead refineries in batches of 60-300 tons. The production of alloys i n such large batches is done to minimize the compositional variation in extruder input material. For the same reason, ready-made alloys are preferred by cable extruders instead of making them on site in smaller quantities. Production of cable-sheathing alloys generally begins with a bath of fully refined lead having 99.99+% purity. Such a high-purity requirement demands the use of primary lead produced from ores instead of secondary lead produced from recycled lead scrap. The impurity levels of Cd, Sn, Sb, As, S, Zn, AI, Ca, and Na are kept below 0.0001% in the melt, whereas Ag and Te levels are lowered to below 0.0005% and the Bi level to below 0.002%. The alloying elements are generally added to the refined lead bath in elemental form rather than using master alloys because of the formation of a large volume of intermetallic compounds with a high dissolution temperature in the master alloys. Depending on the alloying elements added, the temperature of the lead bath is maintained at 430-490°C. Dissolution of these alloying elements is achieved either by adding them to a vortex in the melt created by a high-speed mixer or by their submerged injection with an inert gas.The first technique is applied for alloying elements such as Cu and Te, which have a very low solubility limit; the second method is used for highly reactive elements such as Ca. Alloying elements such as Sb, Sn, and Cd with appreciable solubility limits in lead are added to the melt as master alloys. They are allowed to soak on the surface of the bath and gradually dissolve i n the melt. Subsequently, the alloy isbriefly stirred to ensure uniform distribution of the solute. Some elements also require a flux addition to aid their dissolution. Bi is not used as an addition in any continuous extrusion alloy. During the alloy preparation, precautions are also taken to minimize the oxide content and keep the dissolved oxygen to below 2-3 ppm. Often, the melts are subjected to sodium treatment for sulfur removal. This Na addition initially lower oxide content, but, subsequently, the residual sodium leads to an increase in the rate of oxidation so that the final oxygen content may be higher than it was at the beginning. However, some manufacturers insist on the sodium treatment.

Applications of Lead

583

The alloy melts are cast in l-ton blocks or 25-40-kg ingots using a submerged metal pump. Larger-sized ingots are preferred by the cable industry because of a lower surface area to volume ratio, which, in turn, lowers the oxide content of the ingots. However, the ingot size used by the cable manufacturer is also limited by the capacity of ingot handling units and melting pots. Ingots are cast on a carousel or a straight-line conveyor machine with several molds. Directional solidification is carried out by using a water-cooling tray on the bottom and radiant heaters on the top of the mold. The cooling rate is maintained at 20"C/min down to a temperature of lSO"C, after which the ingots are air cooled. At present, cable-sheathing operations are performed using HanssonRobertson continuous lead extruders. Constant speed, pressure, and temperature conditions of continuous screw extruders provide a homogenous composition and uniform microstructure of the sheath layer, which is very difficult t o achieve in ram-type extrusion.The uniform composition and microstructure allow the use of alloys with lower solute content and higher extrusion rate without any compromise in the mechanical properties of the sheath layer. For example, arsenical cable-sheathing F3 alloy extruded by ram presses has been replaced with 1/2F3 alloy extruded by continuous presses without significant decrease in mechanical properties [4221. In using Hansson-Robertson continuous lead extruders, the molten lead is continuously delivered from a melting pot maintained at 360-380°C. The melting pot is an electrically heated furnace with capacities of 10-60 tons and output rates of 25- 120 kg/min of molten metal. Generally, larger-sized melting pots are preferred because of lower convective currents within the melt and longer dwell times, which allow sufficient time for the oxides dispersed within the melt to float up. The low density difference between lead (p = 11.33 g/&) and lead oxide (p = 9.32-9.62 g/&) gives preference to the use of a larger melting pot. However, the size of the melting pot also depends on the alloy and extruder capacity. In the melting pot, oxide inclusions rise to the top, as they generally have lower density. The ingot feed location and baffles are designed in such a way as to obtain a flow of inclusion-free melt through the bottom of the pot. Filters at the bottom port and along the feed lines eliminate any inclusion still present. Freedom from inclusion i n the cable sheath is critical to the reliable performance of the cable sheath. The molten metal is fed to the extruder from the bottom of the melting pot through an inlet feed pipe heated to 360-380°C. The temperature inside the screw housing liner is maintained at 200-300°C. Initially, this is done by flowing saturated steam through the cooling water channels of the screw housing body. However, under steady-state conditions, cold water at a temperature of 40-60°C is circulated through the cooling water channel and the temperature of the screw housing body is controlled by the flow rate of

584

Chapter 4

molten lead and the screw speed control. There is a liquid zone and a solid zone in the screw region of the extruder. The relative lengths of the liquid and solid zones depend on the alloy, screw speed and thermal gradient of the screw housing. With the increase in screw speed, the extrusion pressure, production rate, and the length of liquid zone increase. This results in lower friction between the screw and lead and adecrease in motoramperage. Therefore. it is desired to maintain a longer liquid zonecloseto the top pitch of the screw. Generally, the screw speeds are adjusted to 20-30 kg/ min of lead consumption. From the screw section, lead is continuously delivered to cable by the screw action of the press. In power cables, the lead sheath layers are normally 2.5-3.5 mm thick. Segregation or formation of precipitates, their growth on the extruder screw surface, and their subsequent incorporation in the cable sheath is a serious problem in the continuous screw extrusion of some of the cablesheathing alloys such as the Pb-O.O4wt.%Cu-O.O4wt.%Te alloy. Control of the size, volume fraction, and distribution of intermetallic precipitates is of great importance for the successful extrusion ofPb-O.O4wt.% Cu0.04wt.% Te alloys. It is not clear whether these precipitates preexist in the charge or form during the extrusion step. Some observations indicate that the precipitates preexist in the charge and coarsen in the screw section of the extruder. Replacing the hard chrome coating of the screw with titanium nitride, which hasa very low surface friction coefficient and high wear resistance, reduced the adherence of precipitates on the screw surface. However, copper and intermetallic precipitates were still observed to form on the screw surface, grow in size,and eventually get incorporated in the cable sheath. These large precipitates act as crack-initiation sites in the sheath layer and limit the continuousextrusion of thesecablestoabout 9 h, thereby limiting the production of longer cables. The low volume fraction of precipitates rule out any significant precipitation strengthening. Recent studies indicate that the precipitates in the cable-sheathing alloy can be eliminated or minimized by reducing the solute concentration to near-solid solubility levels without any degradation in the microstructural stability and mechanical behavior. Imperfect welding in the joint of cable sheath signifies a mechanical weakening and therewith the possibility of longitudinal cracks. Minimization of this would require an extrusion temperature which isnot too low.In addition, the presence of oxide inclusions at the weld section as well as in other sections of the sheathing needs to be eliminated by careful control of the melt, delivery system, and ingot cleanliness.Segregation of alloying elements promotes fatiguefailure and should be minimized. Mechanical damage by animals and during installation is a serious concern.

Applications of Lead

XVI.

585

INSOLUBLELEADANODES

One of the important engineering application of lead alloys is as insoluble anodes in (1) electrowinning of metals from leach and waste solutions, (2) cathodic protection of ships and offshore structures, and ( 3 ) electroplating such as in electrogalvanizing.

A.

Electrowinning Metals from Leaching Solutions

Insoluble lead alloy anodes are used in the electrowinning and plating of metals such as manganese, copper, nickel, and zinc [43 1-4331. Recovery of metals from many low-grade ores is accomplished by leaching the mineral using an acidic solution. The metallic ion in the leach solution is reduced to metal at the cathode and deposited. The electrolytic cell is continuously replenished with fresh leaching solution. At the inert anode, hydrolysis of electrolyte results in oxygen evolution and acid formation. Rolled leadcalciurn-tin, lead-silver-calcium, and lead-silver alloys are the preferred anode materials in these applications, because of their high resistance to corrosion in the sulfuric acid used in electrolytic solutions, low overpotential for oxygen evolution, and adequate strength. Due to the low metal-ion concentrations, the overall cell voltage is usually much larger than the cell potentials of a few tenths of a volt encountered in electrolytic refining [431].The cell voltage is about 2 V in electrowinning of Cu, whereas it is 3-3.7 V for Zn, 2.5-3 V for Sb, and about 5 V for Mn. In the case of electrowinning of zinc from sulfate solutions, feed leach solution will have 100 g of Zn per liter. The starting cathodes for zinc recovery are made of an aluminum sheet with an aluminum conductor bar welded to them, and the cathodes are stripped approximately once a day. Current densities range from 55- l 100 A/m'. Pb-(0.8- l)wt.% Ag anodes are frequently used because of high formability, corrosion resistance, and low Pb content in electrodeposited Zn. Lowering of cell voltage requires the lowering of ohmic losses and the lowering of the overpotentials for the Zn deposition at the cathode and oxygen evolution at the anode. The use of Pb-0.5 wt% Ag-0.6 wt% Ca alloys show lower anode overpotential than Pb-Ag alloys, but fabrication and other properties are inferior to PbAg alloys [432].

B.

Anodes for Cathodic Protection

Cathodic protection is an electrochemical corrosion control technique in which the structure to be protected is made cathodic in an electrochemical system and the oxidation reaction is concentrated at the anode [433-4351.

586

Chapter 4

The anodic reaction may involve either (1) the oxidation of the anode material in the case of sacrificial anodes or (2) the formation of H' ions by electrolysis of water and oxygen evolution in the case of impressed current (insoluble) anodes. The cathodic reaction may involve deposition of a protective compound and an evolution of hydrogen. The anode and cathode are connected to a rectifier that supplies the direct current to the buried electrodes. The anodic and cathodic potentials are measured and controlled with respect to a reference electrodesuchas Ag/AgCI that forms part of the electrochemical system. Lead anodes have high resistance to corrosion by seawater and in many soils, making them economical to use as insoluble anodes in systems for the cathodic protection of ships, offshore drilling rigs, buried pipelines, and other structures. Buried pipelines and ships usually have an organic protective coating, and a cathodic protection system supplements the corrosion protection and prevents corrosion at defect sites in the coating. In the case of ships, anodes are fastened to a steel backing plate (typically 120 cm X 30 cm X 1.9 cm in size) and the steel backing plate is fastened to the hull. A polychloroprene or other polymer sheet between the steel plate and the hull provides insulation between the anode and the ship's hull. The anode and cathode (hull) are connected through a rectifier that supplies the current. The reference electrodes are also attached to the hull of the ship. Several such anodes are attached to the hull The spacing and number of anodes depend on the desired current distribution. Impressed current systems are inexpensive but complex compared to sacrificial anode systems. Caution must be exercised i n not overprotecting the system by the use of large impressed currents/potentials that can lead to hydrogen embrittlement of the structure being protected. Insoluble anodes for cathodic protection are sometimes made of unalloyed lead, but they are usually made of lead alloyed with silver, tin, or antimony. Pb-6 wt% Sb-l wt% Ag, Pb-l wt% Ag, Pb-2 wt% Ag, and Pb-l wt% Ag-l wt% Sn are some of the anode alloys that have been used. These anodes are produced not only in cast form but also as extruded bars or supported sheet. Table 36 compares Pb-6 Sb- l Ag anodes with other impressed current anodes in seawater. The corrosion rates are sensitive to the seawater pressure that varies with depth. Corrosion rate of Pb-Sb-Ag anodes used in offshore oil-rig platforms at a 200-m depth and current densities of 160 A h ' are twice that in shallow waters.

C.

Electrogalvanizing

One of the important electroplatingapplications, in which insoluble lead anodes are used, is in continuous electrogalvanizing of steels [433,436].The very thin, smooth, and formable coatings produced are ideal for deep draw-

Applications of Lead

587

Table 36 Comparison of the Performance of Pb-6 Sb-l Ag Anodes with Other Impressed Current Anodes in Seawater 14331. (Courtesy of ASM International, Materials Park, Ohio.) Anode Pb-6 Sb-l Sn Platinum (plated on substrate) Platinum wire or cladding Graphite Fe- 14 Si-4 Cr

Typical current density Wm')

Consumption rate (kg/A/year)

160-220 540- 1080 1080-5400 10.8-43 10.8-40

0.045-0.09 6 x lo-" 0.23-0.45 0.23-0.45

ing and painting. The pure zinc coating produced has a uniform structure, adherent, and ductile. The thickness can vary from 0.5 to 4.3 pm. Electrogalvanized sheets are used in a number of automotive applications and in exterior panels of household appliances such as freezers, dryers, and ranges.

XVII.

USE OF LEAD IN Bi-BASED OXIDE HIGH-T, SUPERCONDUCTORS

Lead is an important dopant in a number of copper oxide-based high-T, superconductors. It is used to modify the structure, properties, and processing. The discovery of superconductivity at high temperatures by Bednorz and Muller at IBM Zurich Research Laboratory in 1986 was in a La-BaC u - 0 (LBCO) system [(La,Ba)zCuO,] with a critical temperature, T,., of 30 K. This was followed by the discovery of Y-Ba-Cu-0 (YBCO) system with a T, of 90 K by Wu et al. at the University of Alabama and the University of Houston.This high T,., which is above the liquid-nitrogen temperature, led to a frantic search for newer materials. A new class of high-T, superconductors in the Bi-Sr-Ca-Cu-0 (BSCCO) system, which includes no rare-earth elements, was discovered by Maeda on Christmas Eve in 1987 [437]. The oxide had a T,. of about 105 K. Further work on the system showed that the bismuth-based superconductors have three superconducting phases with a general formula Bi,Sr,Ca,,,- ,CU,,,O~,,,+~ with m = 1, 2, and 3 , and these are referred to as 2201, 2212, and 2223 phases, respectively. These have a layered structure described by llBiO/SrO/Cu(I)OJCa(l)/.../Ca(m - I)/Cu(m)OJSrO/Bi011. The real compositions are nonstoichiometric with respect to both the cationic and anionic elements. The atomic positions in their real structures are considerably shifted from the stoichiometric ones so that each phase is featured

588

Chapter 4

by an incommensurate, one-dimensional structural modulation. Usual ceramic fabrication techniques gave mixtures of the 2212 and 2201 phases mainly and some others. Another problem was a small amount of the 2223 phase thus formed seemed to be poorly crystallized. Substitutions for Bi, Sr, and Ca were considered in BSSCO system in order to increase the superconducting properties and to increase the stability and formation of the superconducting phases [437,438]. High-T,. oxides have a layered perovskite structure composed of 3+ (electric charge) ion, 2 + ion, and Cu oxides. The radii of 3+ and 2+ ions are much larger than that of the Cu ion. In the BSCCO system, the 3+ ions with a large ion radius that include Bi, Sb, In, and TI can form a pervoskite structure. The 2+ ions that may be involved in a perovskite structure with Cu include alkaline earths and other 2+ ions such a s Pb and Cd. In order to adjust the distance between Cu-Cu ions in the CuO, plane precisely, the coexistence of the 2+ ions such as Sr and Ca, Ba and Ca, Bi and Pb, and so on will be necessary. The distance between Cu-Cu ions in the CuO, plane plays an important role in T,.. Takano et al. 14381 showed that partial substitution of Bi with lead had a drastic effect on the formation and properties of the 2223 phase. In the identification of Pb as a partial substitution for Bi, they were guided by two key observations. The first observation was the existence of many perovskite-type oxides containing Bi” and Pb’+ as their “A” ion, such as PbTiO, and BiFeO,, that suggested easy substitution of Bi’+ with Pb2’ in the cupric oxide. Second, the substitution could increase the hole concentration in the CuO, sheets and thereby raise the Tc.. It was found thatPb substitution sharply increased the volume fraction of the 2223 phase in a sample with a composition of Bi:Pb:Sr:Ca:Cu = 1.4:0.6:2:2:3.6. Pb” has a larger ionic radius than Bi”, and the Pb” substitution for BiZt contributes to lowering of the internal stress and to the enhancement of the 2223 formation rate. The partial melting range also becomes lower and wider with this substitution. Further work led to two different monophasic compositions: B, ,Pb(,.,SrZCa2Cu3.20;i and B,,~,Pb,,J,Sr2Caz.,Cu3.202. Thus, partial substitution ofPb for Bi increased the stability of the 2223 phase and the Tc. was increased up to 120 K for optimized samples. The formation was accelerated by the presence of a molten phase during synthesis and the crystalline quality was improved. The Pb substitution also was found to improve the formation of single-phase 22 12 and 12 12material. Figure 83 illustrates how the control of the sintering temperatures and lead contents can favor the formation of a single-phase high-T,- material in the BSSCO system 14391. Other Pb-based materials that exhibit superconducting behavior include Pb (7 K), PbTe ( 5 K), Pb,Sr,(Y, ~,Ca,)Cu,O,+,(80-84 K) and T1-

589

Applications of Lead 900

I

I

I I

2213 no mon oxlrlonl

mostly molten

0

8

Q

Q

Q

0

0

0.45

mostly 1112

0

I

e 0.36

I

I

Q

multi-phase roplonr:

a30

0 r-------l I 0

I

I

t0UPph.s. ngion: 1113 oxlrknt

Q

mostly

0

0

0.27

0.18

I

8 0.11

0

x I at. % ?b Bi2.27-xPbxsr2Ca2Cu301 O+d

Figure 83 Schematic representation of the range of sintering temperatures and lead contents over which 12231 single-phase high-TC inaterial in the BSCCO system 14391. (Courtesy of Marcel Dekker Inc., New York.)

PbSr,CaCu,O, (122 K ) [440,441]. An extensive body of knowledge has been developed to greatly improve grain alignment, to increase the high critical current density, .I,., and to process wires and shapes with controlled microstructure at low cost.

XVIII.

LEAD IN GLASS

Silica is an excellent glass former. Other oxides, such as B203, P,O,, and GeO,, are capable of forming a vitreous solid. The properties of the resulting glass can be modified over a wide range by adding other oxides. These additions modify the physical and optical properties of engineering interest. The addition of PbO to glass is first attributed George Ravenscroft who invented “English Crystal” and patented it in 1673. Due to incomparable quality of lead crystals, the English and Irish lead crystal captured the

590

Chapter 4

world market in the early part of the 19th century. Theadditionof lead oxide to glass consisting of silica, sodium oxide, and potassium oxide reduces the melting point and increases the refractive index and electrical resistivity. At a high content (40-80%), PbO is used in glasses for protection against x-rays. The softening point of a glass occurs at progressively lower temperatures as the lead content of the glass increases. The refractive index depends on the nature of the oxides in the glass. The index of lead glasses can reach 1.8. Ordinary glass has a refractive index, n, of about 1 .S [442]. For lead oxide contents between 20% and 70% of the mass of the glass, the density varies between 2.8 and 5.2. Window glass has a density of 2.5. Optical lead glasses are used in a wide range of optical instruments for scientific, industrial, and medical applications. These include cameras, microscopes, photographic equipment, and astronomical telescopes. A significant fraction of optical glasses made today have lead contents from 10% to 70%. Pb glasses have a high refractive index and an Abbe number 4 0 and are therefore classified under flint glasses. For optical instrument applications, they must possess high homogeneity and a constant and well-defined refractive index. Lead in glass also provides an effective radiation shielding from x-ray and gamma radiation. Heavily leaded glass windows are used in hot-cell facilities in nuclear reactors and viewing windows of the control console in medical and industrial radiography installations. The radiation-shielding windows in hot cells are made up of several cast slabs of lead glass, which are polished and glued together. The thickness of the window can reach 1.2 m. The absorptive power of a material is afunction of its density. The density may vary from 3 to 5.2 and lead contents can be as high as 70%. Many other scientific instruments containing x-ray sources such as xray diffractometers have lead-glass windows to provide the needed shielding. The glass for the cone of the television tube contains 23% of lead oxide to provide protection again x-rays generated in the tube, but this glass turns brown under the impact of x-rays. For the screen glass, a glass that contains oxides of strontium and barium is used. Thechrominance delay lines in color television monitors, video recorders, and video cameras usually have a glass as a acoustic-delaying medium. The cost of glass is lower than for other solid delaying media, such as quartz or metals. These delay lines are used in televisions. These glasses are manufactured in the form of bars, from which a thin slice is cut, and the delay line is made from this. In optical fibers used in numerous applications, an outer shell consisting of ordinary glass with a 1.5 index and the core consisting of lead glass (SO% PbO) with a 1.62 index are used. Leaded glass is also used in high-energy particle detectors based on the Cerenkov effect. The Cerenkov effect makes it possible to convert their

Applications of Lead

591

energy (2- 100 GeV) to light radiation (wavelength 150-600 nm). In transparent media, this effect appears in the form of a burst of light, from which rays are emitted in directions that are related to the trajectory and velocity of the particle. A charged particle, passing through a transparent medium at higher speed than that of light in this medium, emits light in preferred directions. Cerenkov detectors are among the most accurate in particle physics and have been at the center of numerous discoveries, including that of the antiproton. Cerenkov emission is maximum (370-420 nm) at short wavelengths, and it is proportional to the density of the medium and to the refractive index. Lead glass is a transparent medium, which meets these characteristics. Glasses with a very high content of lead oxide (PbO 45-55% and 75%) are used in fiber-optic cables. They have a high refractive index (n = 1.7) and high density (d = 4.06), with an excellent transmission in the blue, violet, and ultraviolet region of the spectrum.

XIX.

LEADCHALCOGENIDESEMICONDUCTORS

Lead chalcogenides such as PbTe, PbSe, and PbS are narrow-band-gap semiconductors and have been used for infrared (IR) detector applications prior to World War I1 [443]. PbTe and related compounds are also of interest as a thermoelectric material. The IV-VI compounds crystallize in cubic galenite or distorted NaCl structure, with a coordination number of six and four formula units per unit cell. These compounds crystallize with mixed ioniccovalent chemical bonds. Lead chalcogenides constitute a group of semiconductors that have unique properties in comparisonto the majority of semiconductors. They have a narrow fundamental band gap that widens with a temperature increase, high carrier mobility, and high dielectric constant. The diluted magnetic semiconductors based on these semiconductors are of great practical interest. For ternary compounds such as Pb, .,A,Te (A = Sn, Cd, Mn), the value of S determines the band gaps and the lazing wavelength. The strong temperature dependence of the refractive index and band gap is also utilized to vary the emission wavelength. Further fine-tuning can be obtained by controlling the magnetic field in the case of (Pb,Mn)Te. Therefore, these systems can be utilized as a tunable laser source in the infrared region and are widely investigated a s materials for infrared detectors and semiconductor lasers for use in the spectral range of 3-30 nm and at higher temperatures. High carrierconcentrations in these semiconductors make them suitable for operation in photovoltaic mode instead of photoconductive operation modes of 11-VI semiconductors. The limitation of the most widely used (Cd,Hg)Te to wavelengths below 10 mm and the need for the detectors in the 10-30-nm spectral range for many applications of current interest

592

Chapter 4

make the IV-VI IR detectors technologically very important.These lead chalcogenide-based diode laser spectrometer applications include ultrahighresolution molecular spectroscopy, trace gas detection and pollution monitoring, fiber-optic communications, isotope selective gas absorption,and heterodyne detection. Epitaxial growth of PbTe semiconductors on Si wafers are desired for the purpose of integration of IR detector with the read-out electronic circuits for hybrid sensors. However, this is made difficult by the large lattice mismatch (19%) between Si (a = 5.43 and PbTe ( a = 6.46 and the large difference in thermal expansion coefficients. Epitaxial growth has been achieved, however, by using intermediate epitaxial buffers of CaF, ( a = 5.46 and BaF, (a = 6.46 A). Thin films of binary PbTe and ternary Pb,-,A,Te compounds have been deposited by hot-wall epitaxy [444], molecular beam epitaxy [445,446], and radio-frequency magnetron sputtering [447] techniques. Generally, these depositions are carried out on the cleaved BaF2 substrate. The misfit between BaF, and PbTe is 4.1%, but the excellent thermal expansion match between the two lattices makes it possible to deposit these films free from low-angle grain boundaries [445]. Quantum-well-type structures [447], with Pb-Te as the well and Pb,Mn,-,Te as barrier layer can be used as injection lasers. Such multiquantum-well structures have been grown by molecular beam epitaxy methods consisting of 20 double periods of the PbTe/Pb,Mn,-,Te structure with the PbTe well thickness in the range 50-350 8, and the barrier thickness between 90 and 680 A. Recently, emphasis has been given to the development of polycrystalline PbTe for IR detector application and PbTePbMnTe quantum-well lasers. High temperature dependence of refractive index and band gap in Pb,+,Mn.,Tematerials can be utilized to fabricate tunable laser sources in the 3-30-nm wavelength range and functionally graded thermoelectric devices. The PbTe-based alloys are of interest asa thermoelectric material, particularly in the 600-700-K range. Two-dimensional (thin-film multilayered) structures based on PbTe are being investigated for the possibility of obtaining a very high thermoelectric figures in this system.

A)

A)

A)

5 Lead in the Environment

Lead is a ubiquitous material that exists naturally in the Earth’s crust. As a result, all of us take in a certain amount of lead as a result of our daily activities. Lead can enter the body through inhalation or ingestion. Inorganic lead does not easily penetrate the skin, so this route is considered an insignificant route of exposure. However, organic forms such as tetraethyl lead used in gasoline can penetrate the skin and contribute to the body burden of lead. Recent years have witnessed a dramatic increase in public awareness on the health risks associated with lead exposure, particularly concerning young children. The increase in media attention has resulted in the general public perceiving that lead poisoning is a growing epidemic when, actually, the opposite is true. The latest results of a National Health and Nutrition Examination Survey (NHANES 111) have shown that the average blood lead in preschool children has declined from 14.9 k g of lead per dL of blood as reported from 1976 to 1980 to just 2.8 pg/dL by 1991- 1994. This is well below the Centers for Disease Control (CDC) guideline which identities 10 kg/dL as a level of concern. However, CDC does not recommend specific action (e.g., nutritional and educational intervention for the individual child) unless and until a blood lead value of IS-l9 kg/dL is reached. As shown in Fig. I , there are numerous pathways that lead can enter the body. The most common are through the air, food, water, and possibly by ingesting dust and soil. The relative contribution from each of these pathways will vary depending on a number of factors such as personal habits, whether it is an occupational or environmental setting, and the level of lead present in each of the media. 593

594

Chapter 5

' Figure 1

Sources and pathways of lead to humans (Source: EPA, 1996).

Voluntary measures adopted by multiple industry sectors plus government actions taken over the past several decades have greatly reduced exposures to lead. As noted above, this management of pathways by which humans are exposed to lead has resulted in significant declines in blood lead levels of the general population in the United States. The CDC has called this decline a major public health success and there is every indication that this downward trend in national average blood lead levels will continue. These observed decreases in population blood lead levels are not unique to the United States. Population studiesconducted throughout the world have shown equally dramatic declines. Studies in New Zealand, Sweden, Great Britain, Wales, Denmark, Belgium, and Canada and other studies carried out by OECD have each found significant declines in population blood lead levels in their respective countries. Lead in the environment has been regulated very closely throughout the world because of its potential impact on the health of the general population. Many countries have established maximum levels of lead they will allow in the various environmental media, such as in the air we breathe and the water we drink. Tables 1 and 2 are a compilation of the maximum limits for lead that selected countries have established for these media. However, it is important to note that individual states or provinces within each country

Lead in the Environment

595

Table 1 International Standards for Lead in the GeneralAtmosphere Country Province/territory Argentina Australia Australia Capital Territory South Australia New South Wales Queensland Tasmania Western Australia Northern Territory Victoria Austria Belgium Canada Alberta British Columbia Manitoba New Brunswick Newfoundland Northwest Territories Nova Scotia Ontario Prince Edward Island Quebec Saskatchewan Yukon Czech Republic Denmark EEC Finland France Germany Greece India Iran Ireland Israel

Italy Japan Korea, Republic of

Maximum Pb level (Pgh') No regulations 1.5.' 1 .S" !.St' I.S" 13'

1 .S" 1 .S$'

No regulations I .S" No regulations 2.0 None quoted

Enforcement status -

Recommendation Rccomrnendation Recommendation Recommendation Standard criteria Legal Guideline -

Legal -

EEC directive

-

-

1.0-2.5 5.0

Objective Guideline

-

-

5.0

Legal

-

-

-

-

2.0'

Legal

-

-

I .0-2.0'

Legal

-

-

-

-

0.5 0.4 2.0 No regulations 2.Ot 2.0' None quoted No regulations None quoted 2.0 0.050" 0.0 1 5' 0.005" 2.0 No regulations

Legal Guideline Legal

1 .St'

-

Legal Legal -

Legal Unknown

Legal -

Unknown

596 Table 1

Chapter 5 Continued

Pb level (pg/m2)

Maximum Country Province/territory status Mexico Morocco Nambia Netherlands Norway Peru South Africa Spain Swedcn Thailand Former Union of Soviet Socialist Republics United Kingdom United States Former Yugoslavia

None quoted None quoted 0.01S 2.0 No regulations No regulations 4.0 2.0 No regulations No regulations 3.W 2.0" 1 .S"

None quoted

Enforcement

-

Unknown Proposal

Legal Legal

Legal Guideline Legal -

"Ninety days nveragc. hThrce calendar months average. 'Thlrty days average. "Annual average. 'Twenty-four hours average.

may establish more restrictive limits and, therefore, it is essential that a compliance strategy be directed at all levels of government.

I. TOXIC PROPERTIES OF LEAD Under normal conditions, most of the lead taken in during the day is excreted and a normal balance is maintained. However, in some environmental or occupational settings, this balance may be disrupted and lead can build up in the blood, bones, and organs. Left unchecked, symptoms of lead toxicity could appear. Acute exposure occurs when a large dose of lead is absorbed within a very short period of time. Encephalopathy may develop, resulting in seizures, coma, and, sometimes, death. This is the most severe stage of lead poisoning and, fortunately, the most rare. This is not a condition one would expect to occur in modern industry, but one should be aware that it could.

Lead in the Environment Table 2

597

International Standards for Lend in Drinking Water

Country Province/territory Argentina Australia Australiu Capital Territory South Australia New South Wales Queensland Tasmania Western Australia Northern Territory Victoria Austria Belgium Canada Alberta British Columbia Manitoba New Brunswick Newfoundland Northwest Territories Nova Scotia Ontario Prince Edward Island Quebec Saskatchewan Yukon Czech Republic Denmark EEC Finland France Germany Greece India Iran Ireland Israel Italy Japan Korea, Republic of Mexico Morocco

Maximum levelPb (mg/L)

Enforcement status

None quoted

-

-

-

No regulation 0.05 No regulation No regulation 0.05 0.05

-

Guideline -

-

Guideline Recommendation

-

-

0.05 None quoted 0.05

Legal

-

-

-

Guideline

-

-

0.05

Objective

-

-

-

-

0.05

Objective

-

-

0.05

Legal

-

-

-

-

0.05 0.05 0.05 0.0 1 0.05 0.04

Legal Legal Legal Recommendation Legal Legal

-

-

0.1 0.05 0.05 0.05 0.0 I

Legal -

Legal Legal Legal Legal

-

-

0.05 None quoted

-

Legal

Chapter 5

598 Table 2

Continued

Country Province/territory Nambia Netherlands Norway Peru South Africa Spain Sweden Thailand Former Union of Soviet Socialist Republics United Kingdom United States Former Yugoslavia

Maximum Pb level (WL) 0.0s 0.05 0.02 None quoted 0.1 0.0s None quoted 0.0s

0.0s 0.015

0.05

Enforcement status Legal Legal -

Recommendation Legal -

Legal

Legal Legal Legal

Chronic overexposure occurs with the slow continual absorption of lead over a long period of time. Chronic overexposure is most frequently seen in industry and the general population. This type of exposure is often overlooked until its signs are unmistakable, because the accumulation of lead in your system is slow and because the effectsare not always noticeable or distinguishable from those associated with minor illnesses. At this stage, permanent and irreversible damage may also have occurred. Overexposure to lead can impair vital functions of the body and damage vital organs. Lead can affect the blood, gastrointestinal tract, nervous system, kidney, and the reproductive system. In the case of blood, an overexposure to lead can produce anemia.Thisoccurs when the lead in the system interferes with the body’s ability to produce and sustain red blood cells. As a result, there is a general lowering of hemoglobin, an oxygenbearing substance in red blood cells. Excessive absorption of lead can also affect the gastrointestinal tract. This can lead to symptoms of stomach pain, loss of appetite, nausea, vomiting, diarrhea, and constipation. Reproductive effects in both men and women have been reported following an overexposure to lead. Pregnant women, in particular, should avoid prolonged exposure to lead because it can cross the placental barrier and affect the unborn child. Although the complete extent of lead’s effect on an unborn child is not known, it is reasonable to assume that the fetus is more sensitive to lead than an adult and, therefore, cannot tolerate the same blood

Environment Lead in the

599

lead levels as adults.Therefore,a pregnant woman hasto be even more careful about exposure to lead than anyone else. The reproductive effects in men have also been reported. Although scientists cannot reach complete agreement in this area, there have been reports that there may be a decrease in sexual desire, impotence, decreased ability to produce healthy sperm, and the possibility of sterility. Lead can also have an effect on the nervoussystem. As mentioned earlier, extremely high exposures to lead have been known to cause a condition called lead encephalopathy, which can result in paralysis, convulsions, delirium, and even death. Perhaps the most common effect of lead on the nervous system is to the peripheral nervous system. These would include signs of weakness in the hands and fingers, from wrist or foot drop. Finally, long-term exposure to large doses of lead can result in kidney damage a s well.

II. OCCUPATIONALEXPOSURES Most industrialized countries have established acceptable exposure limits to which workers may be exposed to lead. The permitted exposure level will vary substantially from one country to mother. In addition to establishing exposure limits for the allowable level of lead in air, most countries have also established biological exposure indices for lead. A compilation of international occupational air and biological exposure limits for lead are provided in Table 3. The level of lead in air to which workers are exposed can be achieved through the use of personal air-monitoring devices that measure the level oflead in the workers’ breathing zone. Samplesare preferably collected throughout the worker’s full working shift and then averaged over an 8-h time period. Engineering controls such as local or general exhaust ventilation systems are the preferred method of reducing the workers exposure to within the permissible exposure limits. However, if engineeringcontrols cannot effectively reduce the level of lead in air to within acceptable limits, then it will be necessary to employ other administrative or work practice controls to reduce the exposure to lead. The use of respirators is generally the method of choice if engineering controls are proven to be ineffective. The selection of the proper respirator to use will be dependent on the concentration of lead in the air to which the worker is employed. The requirements for respirator selection under the U.S. Occupational Safety and Healthy Administration’s standard for lead are provided in Table 4. However, if respirators are to be employed to reduce a workers exposure to lead, it is necessary that a respiratory program be

Chapter 5

600

Table 3 International Air and Biological Exposure Limits for Lead Country Provincelterritory

Alr lead (mg/m')

Enforcement status

Blood lead (pg/dL) None quoted

-

SOh

Recommendation

20' 50/20/1S'

Legal

Argentina Australia"

0.15 0.1.5

Legal Recommendation

Australia Capital Territory South Australia New South Wales Queensland Tasmanm Western Australia Northern Territory Victorla Austria

0.1.5

Legal

0.15 0.15 0 .I 5 0.15 0.15

Legal Legal Legal Legal Legal Legal Legal Legal Legal Legal Guideline Guideline Legal Legal Legal Legal Legal

Belgium Canada Alberta Brltish Columbla Manitoba New Brunswick Newfoundland Northwest Terrltorles Nova Scotia Ontario Prince Edward Island Quebec Saskatchewan Yukon Czech Republic Denmark EEC Finland France Germany

Greece India Iran Ireland Israel

0 .

I5

0. I 5 0.10 (men) 0.20 (women) 0. 15 0.05 0.05 0.05 0.05 0.15

0.05 0.05 0.05 0.15

0.05 0.15 0 . 15 0.15

0.05 0.1 0 . I5

0. I 0.15 0.1

None quoted 0.2 0.005 0.15 0.10 (men) 0.05 (women)"

Legal Legal Legal Legal Legal Legal Legal Legal Legal Legal Legal Legal

Recommendation Unknown Legal Legal

None quoted 50/2(Y'

Enforcement status

-

100 (men)

Legal Legal Legal Unknown Legal Legal Legal

80'

Guideline

None 52 80 50 50/30 30 30

Guideline Legal Guideline Legal Guideline Legal

50120'1 50/20" 60120" 50/20" 75

30 70

30 70 50 80 60- 100 50 70' 50 70' 70 (men) 30 (women)g 70' None quoted None quoted 70 60 (men) 30 (women)"

-

Guideline Legal Legal Guldelinc Guideline Legal Guideline Guideline Legal Legal Legal Legal

Legal

Legal Legal

Environment Lead in the

601

Table 3 Continued Air lead

Country Province/territory Italy Japan Luxemburg Mexico Morocco Nambia Netherlands

(mdm')

Enforcement status

0.1

Legal Legal

None quoted

-

0. 15

Legal Unknown Unknown Recommendation

0.15

0.2 0.15

0.10 (1986)

Blood lead (I*.ddL) 70

60 70' None quoted 60

80 70'

Enforcement status Legal Legal Legal -

Unknown Unknown Legal

0.15 (1987) Norway Peru South Afr~ca Spain Sweden

Thailand United Kingdom Unlted States Former Yugoslavia

0.05 0.2 0.15 0.15

0. I O (total) 0.05 (respirable) 0.2 0.15 0.05

0.05

Recommendation Legal Legal Legal Legal

5V 60 (men)

Legal Legal

70 70 (men)' 40 (women)

Recommendation Legal

Legal Legal

50"'

Legal

None quoted

-

8O/4OL 70' SO/30'

Unknown Legal Legal Legal Legal

'All states have agreed in princlple to adopt the National Standard for the Control of Inorganlc Lead atWorkof October 1994 developed by Workplace Australia. 'For males and females not of reproductive capacity. For females of reproductive capac~ty. 'The first value IS for males and for females not of reproductwe capaclty. The second value IS for females of reproductive capaclty. The third value if given IS for females who are pregnant or breastfeeding. 'If ALAU (ammo laevulinic acid urine) > six European unlts. ' A blood lead level between 70 and 80 p . g / I O O mL shall be allowed if the ALAU < 20 mg/g creatinine or ZPP (zmc protoporphysin) < 20 kg/g hemoglobln or the ALAD (delta aminohaevulinlc acld) > six European units. Women under 45 years of age. 'For women over tile age. 'First action levelL-30 p,g/lOO mL: second action Ievel-SO pg/lOo mL. 'Recornmended value for pregnant women IS < 20 &l00 mL and < 30 p,g/lOO mL for women planning pregnancy. 'Workers declared unlit to work if limits are crossed; can return once below 70 p,g/l00 mL (men) and 35 & l 0 0 mL (women). 'The tirst value IS for men and for women over SO years of age. The second value IS f o r women under SO years of age. "'Units are expressed i n pg/IOO g. The worker nust leave the workplace when the average of the last three tests exceeds SO1 p,g/100 g o r when one test exceeds hOY9/100 g. L

602 Table 4

Chapter 5

Rcspiratory Protecton for Lead Aerosols

Airborne concentration of lead or condition of use

Not in excess of 0.5 mg/m3 Not in excess of 1.25 mg/m'

Not i n excess of 2.5 m g h '

Not in excess of 50 mg/m2

Not in excess of 100 m d m '

Greater than 100 mg/m', unknown concentration, or fire fighting

Required respirator" Any air-purifying respirator equipped with HEPA tiltcrsh Any powered, air-purifying respirator equipped with HEPA filters Any air-purifying full-face piece respirator equipped with HEPA filters; any powered, air-purifying respirator with a tight-fitting face piece and HEPA filters Any supplied-air respirator that has a fullface piece and is operated in a pressuredemand or other positive-pressure mode Any supplied-air respirator that has a fullface piece and is operated in a pressuredemand or other positive-pressure mode Any self-contained breathing apparatus that has a full-face piece and is operated in a pressure-demand or other positivepressure mode

"Respirators specitied for high concentratwns can be used at lower concentrations of lead. "A HEPA tilter is one that is at least 99.97%'efficient against panicles of 0.3 k m in diameter. Sowre: U.S. Occupational Safety & Health Administration (OSHA 3126).

developed that will include proper respirator selection, fit testing, cleaning, and appropriate worker education programs on the use of respirators. Work practice controls are also effective in reducing a worker's exposure to lead. The level of lead to which workers are exposed cannot be accurately determined by personal air monitoring. In a plant where adequate precautions are in force, the main route of exposure is the flouting of rules forbidding eating, drinking, and smoking ina contaminated area, or poor personal hygiene through biting of fingernails or failing to wash properly. These all involve transfer of solid food, not airborne transmission. Personal airmonitoring is effective in measuringtheeffectiveness of engineering process controls or in establishing the need for them. Providing the worker with proper change rooms, showering facilities, a clean lunchroom, and pera l l beendemonsonnelprotectiveequipmentsuchasworkclotheshave strated to reduce the exposure of the worker to lead by preventing hand-tomouth transfer of lead. To ensure the effectiveness of the above programs

Lead

the Environment

603

in reducing an employee’s exposure to lead, it is essential that they be enrolled in a medical surveillance program. At a minimum, this would include periodic medical examination and the routine measurement of the worker’s blood lead level. By employing the appropriate engineering controls, usage of respirators in the workplace will ensure that workers will be adequately protected from the workplace hazards associated with an exposure to lead.

This Page Intentionally Left Blank

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Index

Acoustic barriers, 2, 20, 232-291 Activation energy, 30, 81, 104, 105, 111-114,148,168 for creep in lead, 148 grain boundary migration, 112 for grain boundary sliding, 148 grain growth, I 12 recovery, 1 12 for steady state creep, definition, 148 Activation polarization, 432 Age-hardening, 32, 38, 40, 41, 43, 44, 46, 49, 50, 142, 143, 156, 334, 444, 566 Airborne noise, 234 Airborne sound insulation, 234 ALABC, 443 ALARA, 281 Allowable sound levels, 233, 234 Alternating stress, 17 1 Ammunition, 330, 3.55, 569, 570 lead shot, 327, 569 nitroglycerin, lead-lined vessel for, 570 Amplitude ratio, I7 1 Ancient use of lead, I toxicity of lead, discovery of. 1 Andrade’s creep expression, 146

Antimonial lead, 31, 40, 46, 106, 162, 201, 206, 232, 322-323, 325, 342, 360, 374, 375, 377, 407, 415 (see ulso Lead and lead alloys: lead-antimony alloys) Architecture, 483-499 building facings, 332, 483 corrosion of lead sheet, 496 creep of lead sheet in roof, 497 fatigue of lead sheet in roof, 497 tixings, 490-493 flashing, 46, 192, 332, 377, 412, 483, 486, 488, 489, 492, 496, 497 Hagia Sophia in Istanbul, 483 Hanging Gardens of Babylon, 483 House of Blues in Chicago, 483 lead sheet (see Lead sheet) Pantheon in Rome, 483 rooting, 192, 205, 206, 330, 332, 377, 380, 394, 401, 407, 425, 430, 472,483-487, 489, 492, 493, 497-499 standard lead sheet sizes used in, 489, 490 use of lead in historic structures, 483-486

621

Index [Architecture] waterproofing, 483 (see also Waterproofing) weatherings, 377, 488, 489, 49 1, 493, 497 World Trade Center in New York City, 486, 488 ASTAG alloys, 446 ASTATIN alloys, 446 Atomic sizes, common alloy elements in lead, 28 Audible frequency range, 233 Automotive fuel tank production, 406 Babbit alloy, 531. 534, 538, 539 Bahnmetall, 539 Barton Pot process, 437 Base bullion. 16 Base-isolation structures, definition, 458 Basic lead, 225, 309, 340, 342 cast forms, 340 anodes, 342 pumps, 340 valves and pipe fittings, 340 vessels, 342 Batteries, 12, 35, 39, 325, 430-458, 570 emergency supplies, 430 industrial, 325, 430, 447, 457 lead-acid, 430-458 load leveling, 430, 452, 453 rotary expanded grids, 339 specific energy, 430, 449, 450 specific power, 430, 443, 446, 450 storage battery grids, 3 1, 35, 40, 310, 324, 332, 444, 446, 458 telegraphy, 43 1 Battery energy storage plants, 452454 Battery systems competing with leadacid battery, 430, 455 Bearing metal, 31, 32, 35, 39, 46, 323, 420, 534-539 boundary layer lubricants, 537

[Bearing metal] boundary lubrication of, 534 compositions and properties of, 538, 539 hydrodynamic lubrication of, 534 load-velocity (PV) curves, 536 mixed friction, 536 service requirements, 536-538 Bel, 233 Bell-and-spigot joints. 400 Bending stiffness, 234, 237, 238 Bipolar batteries, 446, 447 current discharge curve, 447, 448 Bird-shot, 328 (see ulso Lead shot) Bismuth removal from lead, 18, 35 Boiling water reactor (BWR), 505507, 520 Bonded lead, 4 12-41 5 cold rolling, 414 spot bonding, 415 welding and casting, 415 Breaking strain, I 18 (see also Elongation) Brick lead, 416-418 Brick wall infills, 476-479 Build-up factor, 287, 290, 291, 294, 304, 504 Burial caskets, 541 Cable sheathing, 12, 31, 35, 39, 40, 46. 48, 50, 163,168,183,196, 228, 229, 343, 360-370, 398, 407,430, 570-584 buried cables mechanical darnage, 576 protective coating, 577 communication cable, 57 I fatigue failure, 168, 572 gas-filled cables, 572 high voltage oil filled cables, 571 inclusions, 58 1 mechanical damage, 584 paper insulated lead power cable (PILC), 573-574 power cable, 571 production, 582

Index [Cable sheathing] Ingot sizes, 583 service requirements, 57 1 types of insulation, 573 Cable sheathing alloys, 39, 361, 579, 582, 584 (see also Cable sheathing) compositions, 579 influence of alloying additions, S79 intermetallic precipitates, 584 mechanical properties on storage, 142 Capture gamma ray emission from alloying elements in lead, 289 Castability, 40, 336, 444, S39 Casting of lead and lead alloys, 3 10342 lead shot, 327, 569 influence of arsenic addition, 327 linear shrinkage allowance for lead, 319 mold materials, 316 pattern makers allowance, 319 volume change on freezing, 320 ( s e c d s o Properties of lead and lead alloys: mass) CCD (see Circumscribing-circle diameter) Chemical lead, 46, 206, 207, 225, 232, 284, 342, 356, 418 Church organ, 482 Circumscribing-circle diameter, definition, 344 Coble creep, 92 Coefficient of internal friction, definition, 274 lead and lead alloys, 292-295 concentration and frequency dependence, 276 Coffin-Manson relationship, 180 Coincidence dip, 237 Coincidence region, 237 Collapsible tubes, 40, 360, 539 Cominco’s rotary expansion process, 332

623 Commercial high level waste (CHLW), 509 (see also Highlevel nuclear waste) Common solder alloys, 55 1 Composites of lead, 234, 238, 245 Concentration polarization, 432 Constant stress creep tests, 141 Constitutional supercooling, 3 18 Continuous casting, 328-340, 435 CEAc grid casting process, 332 Cominco’s multi-alloy strip caster, 332 Continuous Properzi process, 329 DM process, 331 melt drag, 329 melt extraction, 329 twin roll casting, 329 Continuous Properzi ingot casting, 327 Controlled collapse chip connection (C4), 563 Copper-bearing lead, 203, 232, 488 Corrosion resistance of lead and lead alloys, 39, 46, 47, 50, 192, 197-232, 277, 283, 309, 337, 342, 356, 360, 412, 414, 418, 42 I , 424, 435, 444, 445, 487, 508, 509, 512, 550-573, 585 Creep creep strength-temperature-stress plot, 167 definition, 123 different stages, 145 influence of additions in solid solution, 155 influence of age-hardening, I 56 influence of prestrain, I 57 data of lead alloys, 162 lead single crystals, 152 influence of solutes, 152 measurement, 149 under multi-axial stress state, 159 polycrystalline lead influence of grain size, 154 influence of stress, 154 temperature, 154

624 [Creep] strength of lead single crystal, 153 tests, 141, 163 Creep curve, idealized, 145 Creep design of lead pipes, 160 Creep-fatigue interaction, 169 Critical frequency, 237, 238, 240 Critical resolved shear stress, 106, 107, 152 for creep of lead single crystal, 152 Crystal ware, 589 Dampers, 458 Damping capacity, 458 DC continuous casting, 327 Decibel, 232, 233 Deep discharge recovery, 336 Defense High Level Waste (DHLW), 509 Deformation mechanism, 57, 104 Deoxidation of the melt, aluminum addition, 316, 321 Desilverization of lead, 49 Diffusional creep, 84, 86, 92, 104, 106, 153-155, 579 Dip casting, 329 Directional solidification, 3 1X Dispersions in lead alloys, 1 12, 361 Drag soldering, 559 Dross, 15-17, 35, 310, 312, 313, 316, 415, 44.5, 446, 457, 539 Drossing, 313, 314, 316 in agitated lead melt, 314 effect of alloying elements, 314 in still air, 314 Drossing of lead antimony alloys, influence of arsenic addition, 316 Dual battery concepts, 450 Dual-in-line packages (DIP), 562 Dynanlic hardness, 122 Dynamic recrystallization, 92, 105, 114 Earthquakes Great Hanshin earthquake in Kobe, Japan, 459, 474-476

Index [Earthquakes] Northridge earthquake, Los Angeles, 470, 472-474 simulation test equipment, 461 Effective strain rate, 159 Effective stress, 159 Effect of grain size on the fatigue strength, 185 Electric arc spray process, 422 (s(v ulso Spray coatings) Electrodeposited coatings, 426 Electrolytic lead, 20, 30, 113, 116 Electrolytic refining, 18 Electronic packaging, chip level connections, 563 Electroplating, 229, 327, 426, 586 Electrotypes, 53 1 Elongation, 118, 123, 141, 149, 160, 566 Encephalopathy, 597 Endurance limit, detinition, 172 Expanded lead-lined pipe, 41 2 Extrusion cable sheathing, 360-370 continuous screw presses, 361, 362 Pirelli press, 370 ram type presses, 361 extrusion pressure estimations of, 346 influence of extrusion rates, 350 influence of reduction ratio, 350 influence of temperature, 347 shape factor, 350 flow process, modeling, 353 impact, 360 pipes, 355 process modeling tinite element analysis, 355 lower bound analysis, 355 slip-line filed analysis, 355 upper bound analysis, 355 rods, 355-360 wires, 355-360

Index Extrusion of lead and lead alloys. 343, 344, 349, 354, 355, 582 direct extrusion, 344, 347, 354, 355, 356 extrusion pressure, 344 geometries, 344 indirect extrusion, 344, 356 lubrication, effect of, 344, 375, 534. 536, 538 Extrusion presses, 326, 355 horizontal presses, 355 hydraulic presses, 355 vertical presses, 355 Extrusion ratio, definition, 344 Fatigue crack initiation,182, 183 definition, 168 plastic strain range, 180 structural features in, 180 types of fluctuating stress, 170 Fatigue failures, in cable-sheathing, 168, S72 Fatigue limit, definition, 172 Fatigue strength, 172 Field dry wells, 520 Flame spray process, 422 (see also Spray coatings) Flat roof, use of lead sheet in, 499 Fluidity definition, 3 16 factor determining, 3 17 spiral fluidity test, 317 Flux cored solder wire, 370 Fluxes for soldering, 557 Frictional forces in load leveling, 162 Fusible alloys, 430, 542-546, S53 designations and compositions, 543 engineering uses, 545 Fusible links, 545 Fusion welded joints, 377 Fusion welding of lead, 380 lead pipe positions, 393 oxy-acetylene gas welding, 380, 389 oxy-hydrogen gas welding. 380

625 [Fusion welding of lead] oxy-natural gas welding, 380 oxy-propane gas welding, 380 pipe joints, 384 sheet lead positions, 389 flat position, 389 overhead position, 392, 393 vertical position, 384, 39 l , 394, 400 undercut seams, 387 welding positions, 387 welding techniques, 387 Gal, definition, 474 Gamma ray attenuation coefficient of lead, 277 Gamma ray interaction with matter, 286 General Motors EVI electric vehicle, 449 Geological nuclear waste repositories corrosion performance of lead in, 513 factors influencing, 5 12 ground water chemistry, 5 14 peak operating temperatures, 5 12 Geologic environments for nuclear waste disposal, 51 I Glasses, flint, 590 Glover tray system. 361 Grain boundary migration, 112, I14 Grain-boundary sliding, 147 Grain growth, 35, 106, 1 IO, I 1 I , 112, 116, 147, 185, 573 Grain refinement, 29, 38, 39, 116, 117, 327 Grain retining, 35, 116, 117 Grain size, 38, 48, 92, 104, 106, 1 10, 112, 114, 116-1 18, 121, 141, 154, 185, 190, 426, 444, 445. 573, 579 Gravity die casting, 322-324 antimony lead blocks, 322 automobile battery grid plates, 322 lead bricks for radiation protection, 322

626 Hansson-Robertson extruders, 362, 363, 367, 370 lists of machines in operation, 363 Hardness of lead and lead alloys, 3 I , 32, 34, 38, 39, 41, 44, 46, 11 I , 120-123, 188, 190, 206, 225, 226, 232, 276, 283, 284, 321, 377, 424, 445, 532, 536, 539, 550, 569 Harper-Dorn creep, 86, 104, 106 Harris process, 18 Heat treating baths, S46 High cycle fatigue, definition, 172 High-level nuclear waste, 290, 303, 304, 307, 5 13 High pressure die casting, 324, 325 die materials, 325 heat transfer coefficients, 324 lead alloy parts made by, 325 lead pot temperatures, 324 High purity lead, 106, 114, 313, 437 Hot-cells, 500 Hot dipped coating, 424 Hot dip soldering, S59 Human voice range, 233 ICRP. 281 Impact extrusion (SW Extrusion) Impact resistance, 123 Imperial smelt process, 16 Infilled frame structures. 476 lead alloys for, 477 load transmission, 477 Ingot casting, 325, 327 cast texture, 326 columnar crystal growth, 326 long range segregation, 327 Internal friction, 26 1, 274-276, 292295 Isasmelt process, 16 IV-VI compounds, S91

Journal bearings, 536 KIVCET process, 16, 17

index Large scale energy storage instantaneous reserve, 452 load frequency control, 452 load leveling, 45 1 worldwide installations, 453 Larsen-Miller parameter, 152 Lattice bending, 147 Lattice parameter, 19, 52 Lead ( w e also Chemical lead; Electrolytic lead; High purity lead; Pattinson lead; Secondary lead; Sheet lead; Sintered lead; Soft lead) atomic weight, 19, 20, 296 compression modulus, 20 consumption, 6 world ranking among metals, 1 corrosion data in different chemical environments, 203 corrosion rates in acids in acetic acid, 202 in acid sodium sulfate, 202 in chromic acid, 201 in fluosilicic acid, 207 in formic acid, 202 in hydrochloric acid, 201 i n hydrofluoric, 202 i n mixed acids containing sulphuric acid, 203 in nitric acid, 202 i n phosphoric acid, 201, 202 in sulfuric acid, 201 i n sulfurous acid, 201 corrosion resistance (.see ulso Corrosion resistance of lead and lead alloys) in atmospheric exposure, 204 in chemical process solution, 208 classifications in different environment, 2 I O i n contact with passivated stainless steel, 198 in contact with steel, AI, Zn, Cd and Mg, 198 in contact with titanium, 198 different forms of, 200

index [Lead] in distilled water free of oxygen and carbon dioxide, 225 in distilled water, effect of dissolved oxygenkarbon dioxide ratio, 225 in domestic water, 226, 227 in industrial water, 226, 227 in natural outdoor atmosphere, 224 nature of protective films, 198 in natural water, 225, 227 in sea water, 226 in soft aerated waters, 226 in soil, 228 in soil, bacterial, 229 in soil, effect of stray currents, 229 solubility of lead compounds in water,198, 199 solubility of lead nitrate in nitric acid, 200 solubility of lead sulphate in sulphuric acid, 199 solubility of PbS04 film in sulfuric acid. 198 in various chemical solutions, 207 in water, 22.5 crystal structure, 19, 27,36, 104 drossing, 15, 16, 310, 314, 445, 446, 457, S39 ( w e c r l s o Dross; Drossing) economic reserves, 3 electrochemical properties, 24, 25 fatigue strength data, 193 health and safety, 2.18 air and biological exposure limits, 600 chronic overexposure, 19, 599 lead absorption into the body, 18, 594 lead aerosols, respiratory protection, 600 lead exposure, 594 lead pathways to human. S94

627 [Lead] occupational exposure, 600 work practice controls, 603 major consumers, I nature of corrosion in aqueous electrolytes, 197 ore minerals, 2 associated minerals, 3 Poisson’s ratio, 20 primary market, 12 production of refined, 6, 8 recovery, 17, 18, 109,110, 111, 112,146, 309, 336, 374, 429, 457, 458, 559, 567, 585 recrystallization, 29, 30, 34, 38, 86, 92, 105, 110, 111, 112, 113, 114,116,146,156, 185, 309, 339, 374,443, 459. S73 regulatory standards, 19 relative abundance in earth’s crust, 2 relative isotopic abundance, 19 shear modulus, 20,80,104,108 sources of, 2 theoretical density, 20 velocity of sound, 20, 237, 275 Young’s modulus, 20 Lead-acid batteries, IS, 433, 430, 433, 438, 441, 443, 444, 44X, 451, 456 a-Pb02, 431,436, 437 basic electrochemistry, 43 1 basic design, 433 battery grid alloys with IOW antimony, 444 P-Pb02, 431, 436, 437 cell voltage, variation with temperature, 432 current-voltage curves, 432 equilibrium cell voltage, 432 equilibrium voltage, 43 1 expanders, 438 GM Electric Vehicle EV 1, 449 grid production techniques, 435 insulating separator sheets, 438

Index [Lead-acid batteries] lead-antimony alloys, influence of As, Sn, Ag, Se, Cu, S, and Cd as ternary additions, 444 maintenance free, 438 manufacture, 438 monolithic battery cases, 438 motive power, 448 negative electrode, 43 1 negative electrode paste, 437 negative electrodes, 437 overvoltage, 432 for hydrogen evolution, 433 for oxygen evolution, 433 portable sealed VRLA, 451 positive electrode, 43 1, 433-435, 437. 440, 441 positive electrode grid paste, 434 positive plate, degradation mechanisms. 445 self discharge, 433 specific power, factors controlling increase, 450 standby batteries, 450 theoretical storage capacity, 432 tubular plate electrode, 437 valve-regulated with immobilized electrolyte. 440 water decomposition, 432 Lead and lead alloys assigned UNS numbers, 58 compositions as per UNS, 59 corrosion resistance in environment, 192 factor responsible for, 192 in soils, 192 in sulphur containing environments, 192 in water, 192 creep-fatigue interaction, 185 fatigue, 168- 197 choice between bending strain vs bending stress criteria, 187 intergranular fracture, 190 intragranular fracture, 190 fatigue strength, 183

[Lead and lead alloys] effect of environment, 183 effect of grain size on, 185 frequency dependence, 183 temperature dependence, 189 internal friction behavior, 261 lead-antimony alloys, 35, 39-46, SO, 114, 117-119, 147, 155, 156, 162, 163, 167, 171, 174, 175, 177-180. 185, 187-190, 22.5, 283, 315-318, 320. 321, 323-325, 327, 331, 335, 336, 342, 349, 370, 373-375, 397, 433, 437, 444-446, 458, 477, 488, 532, 539, 547, 586 lead-arsenic alloys, 31, 162. 174, 189, 317 lead-barium alloys, 3 1 lead-bismuth alloys, 34, 35, 153, 163, 175. 292, 543 lead-cadmium alloys, 39, 40, 155, 156, 292. 542 lead-calcium alloys, 31, 34, 35, 38, 39, 1 15, 116, 156, 162, 163, 167, 171. 172, 174, 190, 191, 283, 314, 323, 324, 331, 335337, 342. 437, 444-446, S85 lead-copper alloys, 39, 48, 109, 1 IO, 116,117.153-155, 157, 161, 163, 167.172-174,177, 178-180, 284,477,479 lead-gold alloys, 1 15 lead-indium alloys, SO, 52, 155, 156, 292 lead-lithium alloys, SO, 5 I , 116, 284, 446 lead-nickel alloys, I17 lead-silver alloys, 29-3 I , 50, 1 15, 116. 153, 163, 167. 322, 335, 551, 585, 586 lead-strontium, 445 lead-tellurium alloys, 30, 48, 116118, 120, 153, 163.167, 171, 178-180, 284, 314. 477 lead-tin alloys, 46-48, 50. 54, 107, 109, I IO, 112, 113, 117, 118,

Index [Lead and lead alloys] 147, 155, 157, 158, 171,174, 175, 185, 187, 225, 292, 318, 319, 342, 360, 397, 401, 404, 414, 424, 479, 480, 48 I , 53 1, 534, 537, 539, 541, 542, 551, 566, S67 lead-zinc alloys, 49, S0 Pb-Ag-In alloys, S0 Pb-alkali alloys, S39 Pb-As-Sn alloys, 3 1, 4 4 , 163 Pb-Bi-Sn alloys, S43 Pb-Bi-Sn-Ca alloys, S43 Pb-Bi-Sn-Cd alloys, S43 Pb-Bi-Sn-In alloys, SS5 Pb-Ca-Ag alloys, 335, 339, 444, 585, S86 Pb-Ca-AI alloys, 444 Pb-Ca-Sn-Ag alloys, 335, 337, 339, 44s Pb-Ca-Sn-Ag-AI alloys, 446 Pb-Ca-Sn alloys, 35, 37, 39, SO, 56, 335, 336, 342, 444, 445, S79 Pb-Cd-Bi-Sn alloys, S43 Pb-Cd-Sb alloys, 184, 189, 349, 444 Pb-Cd-Sn alloys, 184, 186, 349, 444, S42 Pb-Cd-Sn-Zn alloys, S42 Pb-Cu-Te alloys, 48, 176, 477, 579, S84 Pb-Sb-Ag alloys, SO, 53, S86 Pb-Sb-As alloys, 31, 120,156,159, 169, 190, 206, 445 Pb-Sb-As-Sn-Bi alloys, 188 Pb-Sb-Cu-Te alloys, S84 Pb-Sb-Sn alloys, 35, SO, S S , 185, 316, 318, 320, 323, 325, 444, S3 1, 532, S87 Pb-Sb-Sn-As alloys, 187, 188, 397, 424 Pb-Sb-Sn-Cu alloys, S38 Pb-Sb-Znalloys, 188, 190 Pb-Sn-Ag alloys, 3 1, SO, 54, SS 1, 554, S86

629 [Lead and lead alloys] Pb-Sn-Ag-In alloys, SS5 Pb-Sn-alkali alloys, S39 Pb-Sn-Cd-Zn alloys, S42 Pb-Sn-Cu alloys, S37 Pb-Sn-Cu-Sb alloys, 538 Pb-Sn-Li alloys, 145 phase diagrams lead-antimony-silver alloys, S3 lead-antimony-tin alloys, S S lead-arsenic alloys, 32 lead-barium alloys, 33 lead-bismuth alloys, 36 lead-cadmium alloys, 40 lead-calcium alloys, 37 lead-calcium-tin alloys, S6 lead-copper alloys, 4 1 lead-indium alloys, S2 lead-lithium alloys, S1 lead-silver alloys, 30 lead-tellurium alloys, 48 lead-tin alloys, 47 lead-tin-silver alloys, S4 lead-zinc alloys, 49 Lead and lead based laminates, acoustic data, 234 Lead anodes, 3 I , 342, 585, S86 cathodic protection, S85 ship hulls, S86 electrogalvanizing, 585, S86 electrowinning, S85 performance, comparison with other anode materials, S86 Lead-based composite laminates, 234 Lead-based noise control materials, 234, 235 Lead-based semiconductors, S9 1 Lead beads, l Lead brick, 277, 500, S30 Lead bullets, 32.5, 569, S70 Lead burning, 380, 499 (see also Fusion welding of lead) Lead cames, 487 Lead chalcogenides, S9 1 Lead chalcogenides use in IR detector, S92

630 Lead clad detonation cords jetcord, S41 x-cord, S41 Lead coated fiberglass mat, 261 Lead coatings, 42 I Lead coins, I Lead collapsible tubes, S39 Lead collimator, 526 Leaded glass, 530, S90 Leaded vinyl aprons, S26 Leaded vinyls, S30 Lead-fiberglass mat composites, 26 I Lead floor linings, 410 Lead foil, 375, 539, S41 Lead form, 309 basic lead, 309, 340 bonded lead, 229, 309, 340, 412, 416 brickbead, 309, 416-418 lead coatings, 309, 426 supported lead, 309, 407 Lead free solders, 567 Lead glasses Cerenkov detectors, S91 chrominance delay lines, S90 fiber optic cable, 591 Lead glasses, optical, S90 Lead glass windows, 526, 590 Lead in atmosphere, international standards, 595 Lead in drinking water, international standards, 595 Lead in glass, S89 Lead in packaging, S39 Lead in sealing, S39 Lead in the environment, 594 Lead-lined blocks, 530 Lead melting pot, elimination and trapping of inclusions, S83 Lead mine production, 4 Lead mines, 4, 6 Lead ore deposits. 2, 3, 4 formation, 3 Lead ore minerals anglesite, 2, 3 crussite, 2, 3 galena, 2, 3, 15

Index Lead pipes. 160, 185, 192,343, 356, 399 Lead poisoning, 19, 594, 597 Lead producers, I O Lead sheet, 2, 161, 206, 240, 24 I , 248, 249, 261, 277, 310, 332, 371-377, 380-384, 387, 389394, 397, 399, 407-410, 414, 419, 421, 422, 43.5, 446, 483499, 501, 526, 530, S70 Lead sheet joints, 381 Lead sheets in architecture, 483 Lead-shielded cask for radioactive transport and storage, S04 Lead shot calibrated, 330 high precision, S70 influence of arsenic addition, S69 Lead strip, 329, 330, 331, 332, 334, 335, 355, 3.56, 375, 529 Lead-tin alloys for organ pipes, 480 Lead-tin based bearings, S34 Lead-tin solders, S42 commercial forms, S S 1 melting characteristics, S S 1 Lead tube clad detonating cords, S42 Lead-vinyl composite sheet, 248 Lead water pipes, 1 Lead weights. 547 Leaning Tower of Pisa, S47 Light bulbs, SS0 Linear absorption coefficient, 287 Linotype, 53 1 Logarithmic decrement, 20, 274 Long freezing range alloys, 3 l8 Low cycle fatigue, definition, 172 Low-level waste, 301, 304, 306, 307, 504 Low melting point alloys (see Fusible alloys) Low specific activity, S02 Machining of lead, 418 die cutting and stamping, 418 waterjet cutting, 419 Maintenance free batteries, 438

Index Malleability, I , 458, 459, 493, 539 Mansford roofs, 490 Martens mirror extensometer, 149 Mass attenuation coefficient, 287, 288 Mass attenuation coefficient for lead, 288 Matte, 16, 226, 229, 279, 280, 286, 422, S05 Mean stress, 17 1 Measurements of airborne sound transmission, 242 Mechanical fastening cage supported equipment, 408 lead sheet to steel vessels, 407 loose-lined equipment, 407 Mechanical joints, 377 batten seam, 377 bossing, 377 drip joints, 377 flat-lock seam, 377 hollow roll, 377, 491 standing seam, 377, 49 I , 492 wood-cored roll, 377, 491 Mechanically fastening, 407 lead sheet to wood/concrete walls, 407 Melting of lead, 310, 362 furnaces, 3 I O pots, 310 Metal forming process, 342-377 Miner’s rule in fatigue, 180 Mixed fission products, 296 Moh’s hardness, 120 Molten lead in heat transfer, S47 Patenting, S46 Monitored retrievable storage (MRS), 506, 508, S20 Monotype, S3 I , S33 Moss growth, treatment of, 497 Nabarro-Herring creep, 92 Narrow band gap semiconductors, S9 1 Neutron absorption by alloying elements in lead, 283

631 Neutron activation, 278 Nitroglycerin, 570 Nuclear reactors, 303, 499 Nuclear radiation shielding, 20, SO, 276-307, 499-526 Nuclear waste disposal plans of different countries, 5 10 Nuclear waste, geologic disposal, S08 Nuclear waste package, lithostaticpressure-protection, S09 Nuclear waste transport and storage containers, 304 Octave bands, 242, 243 Organ pipes, 46, 479 church organs, pipes in, 482 lead alloy sheet, manufacturing, 480 stop pipes in, 482 Tabernacle in Salt Lake City, 481 Oxidation of lead, 31 1 blue film formation time, 316 influence of alloying elements, 3 13 influence of antimony content, 3 15 kinetics, 3 12 lead controlling step, 312 parabolic rate constant, 312 Parkes zinc desilvering process, 18 Patenting, S46 Patina, 497 Patination oil, 496 Pattinson lead, 18, 1 16 Pattinson process, l 8 PbO, 311, 312, 316, 431, 433, 436, 44 I , 445,457, 509, 589-59 1 PbS, S9 1 PbSe, S91 PbTe, S91 for thermo-electric applications, S92 Peierls’ stress, 80 Performance of creep tests, 149 Phase diagrams (SWulso Lead and lead alloys: phase diagrams) Pilling and Bedworth ratio, 3 12

632 Pipe alloys. 39 Pirelli press, 370 Pitched roofs, 492, 498 Plain bearing, 534 Plant6 plates, 35. 433 Plasma spray process. 422 (see ulso Spray coatings) Plaster mold process, 322 Plate making line, 334 Plumber’s joint, S78 Plumber’s soil, 400 Polygonization, 1 1 I , 155 Positive plate production. factors considered in, 336 Power law creep, X 1, 84, 86. 92, 105, 154, 155, S79 Precipitates in lead alloys, 36. 38. 46, 49, 81, 109, 112, 117, 146, 156. 162. 579. 582, 584 Premature capacity loss (PCL), 445 Pressure-equalizing material ( s e c crlso Frictional forces in load leveling) Pressurized water reactor (PWR), 505, S20 Primary creep. 145 Printing types, 530, 53 1 Production of lead metal. 15 drossing. IS, 16, 310. 314. 445. 446, 457, 539 froth flotation. 15 lend concentrate, I6 ore dressing, 15 relining. IS. 17. 18. 31, 35, 40, 116, 117. 301. 327, 342, 4.57. 458, 539, S85 coppcr rcmoval, 17 softening. I8 slag composition. I6 smelting. X. IS, 16, 17 Properties of lead and lead alloys acoustic. 20. 25, 232-295, 480 mass law, 235. 237, 241 damping. 2, I S, 20. 159, 234. 237, 238. 274. 275. 429, 458-46 I . 474. 548

Index [Properties of lead and lead alloys] elastic, 20, 476 clectrical. 38, 52, 87, 547 electrochemical, 27, 444, 445 mass, 52, 93 mechanical, 25. 35, 39, 57-192, 331, 361, 381, 412, 435. 445, 446, 547, 553, 579, 583 natural logarithmic damping constant, 20 nuclear, 276 physical, 20, 25, 29-57, 229, 277, 490, 567, 574 thermal, 57, 98 viscosity, 4 1 Properzi continuous casting and direct rolling, 329 QSL process, 16, 17 Quantum well type structures, 592 Radiation definition, 278 gamma, 2, 20, 40, 276. 277, 278, 279, 282, 283, 285, 286, 288, 290, 295, 296. 298, 303. 499. 504, 505, 590 ionizing. 2, 279, 280 neutron, 2, 20, 35, 40. 5 0 , 278, 279, 280, 282, 283, 284, 285, 288, 289, 296, 298, 504, 505 x-ray. 2. 147, 418. 419. 527, 528, 529, 530, 590 Radiation attenuation, calculation. 289 Radiation shiclding. 20, 34. 35. 48, 192. 278. 285. 356. 430, 499, 50 1, 504, 526, 527, 590 (sec o l s o Nuclear radiation shiclding) CT scanner. S26 forms of lend used, 2x5 industrial and medical, 526 industrial radiography. S28 lead bricks. casting, S00 nuclear facilities, 499 nuclear wastc packages, 499

Index [Radiation shielding] in portable nuclear reactors, 501 x-ray installations, 529 Radiation shielding windows, 590 Radioactive transport and storage containers, use of lead, 501 Radon shield, 498 RAPS, 456 Recrystallization diagrams, 1 16 Recrystallization temperature, 1 14 Recycling of lead from batteries, 457 hydrometallurgical schemes, 457 problem elements, 457 pyrometallurgical schemes, 457 Red lead oxide, 31 1 Reduction in area, 118, 151 Relaxation length, 288 Relaxation tests, 141 rem (see Roentgen equivalent mammal) Remote area power supplies, 456 Reprocessed nuclear waste, SOX, 509, 520 Required lead shield thickness for gamma radiation. 295 Resonance frequency, 235, 275 Roentgen equivalent mammal, 281 Rolling, 370 antimonial lead sheets, 377 duplex lead sheets, 377 lead sheets/foils, process of, 229, 375 process description, 37 1 resistance to deformation, 373 spreading of the strip, 371 torque, 37 1 Rolling mills, types of, 371 Rose’s metal, 543 Rotary expander, 334 Rupture strength, 15 1 Sabine equation, 242 Safety devices, 542 Salinity, definition, 226 Sand casting, 310, 321, 322

633 Sand cast parts, 321 Screen printing, 565 Sealants, in roofing, 496 Sealed storage casks, 520 Seals, 539, 541, 545 Secondary creep, 145 Secondary lead, 8, 10, 12, 582 Seismic isolation interfaces, 458 Seismic protection, 2, 15, 20, 458 base-isolation, cost versus benefit, 476 buildings using base isolation system, 470 City Hall, Salt Lake City, 470 dampers, 458 accumulated plastic deformation, 464, 467, 469 energy dissipation capability, 465 yield shear coefficient, 467 dampers yield strength, sQy, 469 dampers yield strength, detinition, 470 Great Hanshin earthquake, performance of base isolated buildings, 474 isolation interface, base shear coefficient, 467 isolation system integrated, 459 independent hybrid. 459 isolators, 458-460, 474 lead dampers, 459-462, 476 lead damper shapes, 460 lead-rubber bearing, 459 Northridge earthquake, performance of base-isolated buildings, 470 period of the base-isolated building, 469 rubber bearing dampers, 459, 474 selected base-isolated buildings in Japan, 470 shock wave, equivalent velocity, V,, 467 U-type dampers, 461 law of similitude, 465 scale up, 465

634 [Seismic protection] U-type lead dampers, 461, 462 energy dissipation, 464 energy dissipation, frequency and amplitude dependence, 464 evaluation, 464 specifications, 462 Seismic protection devices, 458 Seismically isolated structures, detinitioln (see Base isolated structures) Semi-Durville casting, 327 Sheet lead used in radon shielding, 497 (sce also Lead sheet) Sherby-Dorn parameter, 1S 1 Shielding thickness for gamma radiation, 285 Short freezing range alloys, 3 I8 Shot (see Lead shot) Shot towers, S69 Shrinkage, 31, 41 Sinter-blast furnace, 16 SLI batteries, 332, 430, 447-449 Slip-band extrusions, 1 82 Slip-band intrusions, 182 Slipsystems, 107, 109 S-N curves, 172, 185 Sodium treatment, lead melts, 582 Softlead, 40, 168, 187,S41 Softening, 18, 31, 40, 1 10, 113, 114, 566, S90 Solderability of different metals, SS9 Soldering joint types branch joints, 400 butt joints, 399 cup joints, 400 lap joints, 398 lock joints, 399 pipe joints, 399 wiped joints, 400 lead to other metals, 401 non-CFC fluxes, 56.5 process description, 397 solder alloys, 397, 550, SS3 surface preparation for, SS6 wiping, 397

Index Soldering fluxes, 397 inorganic type, 558 no clean fluxes, SS9 organic type, SS8 rosin, S S 8 Soldering in electronic assemblies, S62 Soldering process description, SS0 Soldering processes, SS9 Solder joint design, SS3 Solders, 550-568 Sound levels, 232 Sound level unit (see Bel, decibel) Sound reduction index, 235, 238, 240-243, 245 Sound transmission class, 243, 248, 26 1 Sources of radiation, nuclear fuel cycle, 295 Specific work of impact, 122 Speiss layer, 16 Spent fuel storage, 307, SOS, SO8 Spent nuclear fuel elements, 303, 304, 307, S06 Spotty metal, 48 1 Spray coatings, 421 porosity, 422 SRI (see Sound reduction index) Stacking-fault energy of lead, 147 STC (see Sound transmission class) Steady state creep, 84, 147, 149, 152, 160 Stereotype, S3 I , S32 Storage of renewable energy, 453 Strainhardening, 108,113,146,152, 309 Stress ratio, 171 Stress-rupture curves, 162 Stress-rupturedata, 141, 162 Stress-rupture test, IS 1 Strip uncoiler, 334 Structural changes during creep, 147 Structural stability, 39, 458, 572, 573, S84 Subatomic particle detectors, S27 Subgrain growth, 1 I I

Index Subgrain structure, 147 Superconductors, high temperature containing lead, 587 Surface mount technology (SMT), 562 Tape automated bonding (TAB), 563 TCLP leach test, 458 Telephone cables, 185, 573 Tensile strength, 39, 50, 113, 117120, 283, 284, 444,469, 566 Terne (see Terneplate) Terneplate, 47, 192, 3 10, 377, 401, 402, 404, 406, 425, 429 soldering, 404 welding, 401 arc and oxyfuel welding, 404 resistance seam welding, 402 resistance spot welding, 404 welding automotive fuel tanks (sce Automotive fuel tank product ion) Tertiary creep, 146 Tetraethyl lead, 594 Thermal activation, 57, 81 Thermal neutron capture cross-section of alloying elements in lead, 289 Through-hole technology. 562 Tin-free solders. 55 I Transmission loss, 233, 238, 242, 248, 249, 261 Type metals, compositions and properties, 5 3 I , 532 Ultrasonic soldering, 561 Underground waste repositories, 228, 506

635 Unified Numbering System (UNS), 52 U.S. Nuclear Waste Policy Act, 508 Vacuum seals, light bulbs, 541, 550 Valve-regulated lead-acid (VRLA) batteries, 440, 449 VRLA batteries corrosion of positive grid, 443 oxygen cycle in, 441 Waste immobilization in vitreous glass, 509 Waste packages, roll of lead, 508 Waterprooting, 192, 332, 430, 483, 485 Wave soldering, 559 Weight balancing applications, 547 computer disk drives, 547 Welding of lead electrical welding, 396 friction stir welding, 394 loose-lock mechanical joints, 380 terneplate (see Terneplate) Welding safety, 396 White metals, 537-539 Wire bonding, 563 Wood’s metal, 543 X-ray housing, 526 X-ray intensifying screens, 527 Yellow lead oxide, 31 1 Yield strength, 104, 117, 120, 123, 185, 344, 346, 444, 46 I , 462, 464,469,470 Zero emission vehicle, 12, 15 Zone melting, 18