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PITMAN METALLURGY SERIES

FRANK

T.

SISCO,

Advisory Editor

Engineering

Metallurgy

Engineering

pitman PUBLISHING CORPORATION

>*

Metallurgy By

THE COMMITTEE ON METALLURGY -4

of

collaborative writing group

metallurgy professors.

NEW YORK

•

TORONTO

•

LONDON

Copyright

©,

1957

BY

PITMAN PUBLISHING CORPORATION No part of this book reproduced in any form without

All rights reserved.

may the

l>e

written

permission

of

the

publisher.

1.2

Associated Companies Sir Isaac

London Sir Isaac

t

&9

Pitman & Sons, Ltd. Johannesburg

Mcllraurne

Pitman & Sons (Canada), Ltd. Toronto /

/ ,

QOZAfcl-

COTA

PRINTED

in

the United States of America

Coauthors Theodore Allen,

M.S.M.E., Associate Professor of Mechanical En-

Jr.,

gineering, University of Houston, Houston, Texas; Engineer Associated

with Anderson, Greenwood and Co., Bellaire, Texas

Lee L. Amidon, M.S.M.E., Professor and Head, Department of Mechanical Engineering, South Dakota State College, Brookings, South Dakota

John K. Anthony.

M.S.. Associate Professor of Physical Metallurgy, Uni-

versity of Arizona,

Robert

E.

Tucson, Arizona

Bannon, S.M., Professor

Engineering, Newark,

New

of Metallurgy,

Newark College

of

Jersey

Francis William Brown, Ph.D., Associate Professor, Clarkson College of Technology, Potsdam, New York

Frederick Leo Coonan, D.Sc, Professor and Chairman, Department of Metallurgy and Chemistry, U.S. Naval Postgraduate School, Monterey, California

Howard

P. Davis, M.S., Associate Professor,

Engineering, University of

Harold Vincent Fairbanks, West Virginia

University,

Mars G. Fontana,

Department

of

Mechanical

Wyoming, Laramie, Wyoming

M.S., Professor of Metallurgical Engineering,

Morgantown, West Virginia

Ph.D., Professor and Chairman, Department of Metal-

lurgical Engineering,

The Ohio

State University,

Columbus, Ohio

Arthur R. Foster, M.Eng., ing,

Associate Professor of Mechanical EngineerNortheastern University, Boston, Massachusetts

Arthur C. Forsyth,

Ph.D., Associate Professor of Metallurgical Engi-

neering, University of Illinois, Urbana, Illinois

Richard Edward Grace, Ph.D., Associate Professor of Metallurgical Engineering, Purdue University, Lafayette, Indiana

Leonard

B. Gulbransen, Ph.D., Associate Professor,

versity, St. Louis,

Washington Uni-

Missouri

Joseph Gurland, D.Sc, Assistant Professor, Division of Engineering,

Brown

University, Providence,

Walter R. Hibbard,

Rhode

Island

Adjunct Associate Professor of Metallurgy, College of Engineering, University of Bridgeport, Bridgeport, Con-

necticut

M.S.,

Coauthors

vi

Walter M. Hirthe,

M.S.M.E., Assistant Professor of Mechanical En-

gineering, College of Engineering, Marquette University, Milwaukee,

Wisconsin

Abraham Eldred Hostetter,

Ph.D., Professor of Metallurgy, Kansas

State College, Manhattan, Kansas

John

Kaufman, Metallurgy Department, Academy New York

J.

of Aeronautics,

Flushing, J.

Edward Krauss, M.S., Head, Department of Mechanical Technology, York City Community College, Brooklyn, New York

New

Hollis Philip Leighly, Jr., Ph.D., Chairman, Department of Metallurgy, University of Denver, Denver, Colorado Irving

Levinson, M.S., Professor of Mechanical Engineering, Lawrence

J.

Institute of Technology, Detroit,

Michigan

Jules Washington Lindau, III, M.E., Associate Professor of Mechanical Engineering, The University of South Carolina, Columbia, South Carolina

James R. MacDonald, Ph.D., Chairman, Department gineering, School of Engineering,

The

Mechanical En-

of

University of Mississippi, Uni-

versity, Mississippi

Omar

C. Moore, M.S., Associate Professor of Chemical Engineering, Alabama Polytechnic Institute, Auburn, Alabama

Don

R. Mosher,

B.S.,

Assistant Professor of Mechanical Engineering,

University of Colorado, Boulder, Colorado

Charles Arthur Nagler, Ph.D., Associate Professor, Department of Chemical and Metallurgical Engineering, Wayne State University, Detroit, Michigan

Richard O. Powell, College

of Engineering,

Tulane

University,

New

Orleans, Louisiana

Oran Allan

Pringle, M.S.M.E., Associate Professor of Mechanical En-

gineering, University of Missouri, Columbia, Missouri

Kenneth

E.

Rose, M.S., Professor of Metallurgical Engineering, UniLawrence, Kansas

versity of Kansas,

Philip C. Rosenthal, M.S., Professor of Metallurgical Engineering, University of Wisconsin, Madison, Wisconsin

Robert

E. Shaffer, M.S., Associate Professor of Engineering, University

of Buffalo, Buffalo,

New

York

Coauthors

vii

Walter ing,

E. Short, M.S.M.E., Associate Professor of Mechanical EngineerBradley University, Peoria, Illinois

Floyd Sheldon Smith, M.S., ing, Alabama Polytechnic

Associate Professor of Mechanical EngineerInstitute,

Auburn, Alabama

GEORGE

V. Smith, Ph.D., Assistant Director for Metallurgical EngineerSchool of Chemical and Metallurgical Engineering, College of Engineering, Cornell University, Ithaca, New York ing,

Sicmund Levern Smith, M.Met.E., Professor of Metallurgy, College of Mines, University of Arizona, Tucson, Arizona Joseph William Spretnak, Ph.D., Professor of Metallurgical Engineering, The Ohio State University, Columbus, Ohio

Rocer Greenleaf Stevens,

Ph.D., Head, Department of Chemical Engineering, Southwestern Louisiana Institute, Lafayette, Louisiana

William H. Tholke, cinnati, Cincinnati,

B.S., Instructor of

Metallurgy, University of Cin-

Ohio

John Stanton Winston, M.A., M.S., Chairman, Department of Metallurgy, Mackay School of Mines, University of Nevada, Reno, Nevada

Preface Engineering Metallurgy was developed standable

manner

to present in a concise, under-

the principles of ferrous and nonferrous metallurgy

for all engineers— student

and practicing. Both graduate and undergraduneed a fundamental knowledge of the metals they their work. The emphasis, throughout therefore, is on

ate student engineers

employ

will

in

metallurgical principles rather than on handbook information; however, specific data are given so as to provide a realistic structure to reinforce the theoretical presentations. The practicing engineer who has had little

contact with the field of metallurgy, or who has had no formal work in metallurgy, will find in this book a sufficiently complete summary of all of the essentials he needs to

the

know

to obtain a broad understanding of

field.

Keeping up with metallurgical developments in art, as

all branches of the reported in the technical literature of the world, is difficult for

those actively engaged in the manufacture, processing, or the industrial use of engineering metals and alloys. For the thousands of such individuals, who work with or who use metallic materials but who cannot possibly find time to read everything, summaries such as this book have a well-defined place in the scheme of things.

Because metallurgy

is

such a dynamic and diversified art and science,

the preparation of a definitive, up-to-date, authoritative

work

in this field

required a bold approach. Forty professors actually engaged in teaching engineering metallurgy in universities across the country were asked to pool their knowledge and research to produce this text. Through intensive questionnaire techniques,

the scope and content of the book were defined and outlined by the group. Once the basic content had been selected, ideas for all chapters were channeled to experts selected to first

on individual chapter committees. From these ideas and their own combined experience and research, each committee built chapter outlines. Overlaps and omissions were detected by the editorial staff and referred to the committees for alteration and preparation of rough draft. The coauthors read and checked the smoothness of presentation of the chapter, adding to and refining the draft. Thus were built the twentyserve

three chapters of Engineering Metallurgy by the forty coauthors.

Chapters

1

through

6 deal

with the general principles of metallurgy

as they are related to engineering.

Chapter 3 (Factors Affecting Engineering Properties) will be especially useful to the student in gaining ix

x

Preface

an appreciation of the over-all study of engineering metallurgy. In Chapter 6 (Phase Diagrams and the Simply Alloy Systems) the student is introduced to basic problems of equilibrium and alloying. Chapters 7 through 10 treat of the nonferrous metals and alloys. To these important ,

materials, a generous

amount

of space has been devoted so that com-

plete coverage could be obtained. Chapters

1 1 through 20 arc concerned with iron and steel— with special attention given to the subjects of heat treatment and ferrous alloys. Machinability, corrosion, and the effects

of temperature are fully covered in Chapters 21 to 23. All technical terms are defined as they are introduced, and stress laid

upon fundamental

concepts. At the

end of each chapter there

and exercises constructed on the important definitions and

is

is

a set of questions

to help the student focus at-

tention

principles presented in the

chapter.

and illustrative examples are set down with Drawings and photographs are used without re-

Principles, definitions,

precision

and

clarity.

serve to amplify the discussion. In certain chapters, detailed tables are

included for the convenience of the reader. The Committee on Metallurgy is aware that the usage of this text and developments in the field will indicate areas needing revision. Professors

and students

are therefore urged to send comments on chapters to the publisher or chapter committees so that appropriate changes may be made in the next edition.

The

Editor

Contents Preface

v

Chapter

1.

Metallurgy and Engineering

1

1.1.

Metallurgy as an Art

1

1.2.

Metallurgy as a Science

2

1.3.

Metallurgy and Engineering

3

Chapter

2.

Fundamental Structure of Metals and Alloys

5

2.1.

Building Blocks of Matter

5

2.2.

The Building-Up

Principle

9

in Solids

2.3.

Types of Bonding

2.4.

Assemblages of Atoms

11

2.5.

Defects in Crystals

14

2.6.

Polycrystalline Aggregates

16

2.7.

Interactions in Metallic Solutions

18

9

2.8.

Liquid Solutions

19

2.9.

Solid Solutions

20

Intermediate Phases

20

2.10.

Chapter

3.

Factors Affecting Engineering Properties

3.1.

Grain Size Control

3.2.

Effect of

...

23 24

Grain Size on Properties

29

3.3.

Deformation of Metals

32

3.4.

Slip in Single Crystals

33

3.5.

Twinning

36

3.6.

Deformation of Polycrystalline Metals

37

3.7.

Hot Working

38

3.8.

Cold Working

40

3.9.

Annealing Cold Worked Metal

42

3.10.

Factors Affecting Rccrysiallization Temperature and Grain Size

45 xi

xii

Contents

3.11.

Summary

3.12.

Solid Solution Effects

47

3.13.

Polyphase Structures

49

3.14.

Allotropic Transformation

51

3.15.

Precipitation

Chapter

4.

of

Hot and Cold Working

:

Hardening

46

52

Static Properties of Metallic Materials

...

57

4.1.

Properties of Metallic Materials

57

4.2.

The

60

4.3.

Tensile Strength

4.4.

Elastic Limit, Proportional Limit,

Relative Standardization of Static Tests

61

and Modulus

of Elas-

63

ticity

and Yield Strength

4.5.

Yield Point

4.6.

Elongation and Reduction of Area

67

4.7.

Hardness

69

4.8.

Comparison of the Various Hardness Tests

4.9.

Relation

among Hardness

and Tensile Strength for 4.10.

Relation

4.11.

Shear, Compression,

4.12.

Sonic Testing

Chapter 5.1.

72

Tests and between Hardness

Steel

among Hardness

and Tensile Strength

66

73

Tests and between Hardness

for Nonferrous Alloys

....

and Bend Tests

77 78

Dynamic Properties of Metallic Materials

5.

Notch

74

Brittleness

and Transition from Ductile

.

.

81

to Brittle

Fracture

81

5.2.

Value of the Notched-Bar Impact Test

85

5.3.

86

5.4.

The Mechanism of Fatigue The Endurance Limit

5.5.

Relation of the Endurance Limit to Other Properties

5.6.

The

5.7.

Corrosion Fatigue

5.8.

Increasing the Endurance Limit by Shot Pcening

5.9.

Significance of

5.10.

Chapter 6.1.

Effect of

Notches on the Endurance Limit

87 .

.

....

6.

...

Endurance Data

92 93 94

Phase Diagrams and the Simple Alloy Systems

Thermodynamics and Thermostatics

89 92

Damping Capacity

Solid State

88

...

97

97

6.2.

Contents Concept of Dynamic Equilibrium

6.3.

Cooling Curves

98

6.4.

Solid State Mass Transfer

99

6.5.

The

Phase Rule

100

6.6.

Solid State Solubility

101

6.7.

Binary Systems

101

6.8.

Intermetallic

6.9.

The

6.10.

xiii

97

Compounds

Peritectic Reaction

106 .

108

•

Closure

109

Chapter 7. Heat Treatment of Alloys by Precipitation Hardening 7.1.

Alloy Requirements

7.2.

Step

7.3.

Step II— Precipitation Heat Treatment (Aging)

7.4.

Theory of Precipitation Hardening

7.5.

The

Ill

Ill

.

I— Solution Heat Treatment

Effect of

112

....

Precipitation

Heat Treatment

117

Hardening

Aluminum

Precipitation

7.7. 7.8-

Hardening of Magnesium Alloys Precipitation Hardening of Copper Base Alloys

7.9.

Precipitation Hardening in

Aging and

7.11.

Precipitation

Chapter 8.1. 8.2. 8.3. 8.4. 8.5. 8.6.

8.7. 8.8. 8.9.

of

Alloys

Precipitation

Strain

8.

Its

14

114

Time and Temperature During

7.6.

7.10.

1

.... .... .... ....

Low Carbon Steel Consequences in Low Carbon

Hardening

in

Steel

Alloy Steels

Light Alloys as Engineering Materials

Aluminum Economics of the Aluminum Industry Aluminum Ores— Occurrence and Concentration Manufacture of Aluminum Physical Properties of Aluminum Chemical Properties of Aluminum Aluminum Alloys The Wrought Alloys Aluminum Casting Alloys

119 121

124 125 126

126

....

History of

129 129 130

.

.

.

.

131

132 133 134 135

136 140

8.10.

Functions of Alloying Elements

143

8.11.

Cold and Hot Working of Aluminum Alloys

147

xiv 8.12.

Contents Heat Treatment of Aluminum Alloys

8.13.

Corrosion Resistance of

8.14.

Joining of

8.15.

Magnesium and

8.16.

Beryllium

158

8.17.

Titanium

159

Chapter

9.

Aluminum

Aluminum

148

Alloys

150

Alloys

152

Alloys

Its

155

Copper and Copper- Base as Engineering Materials and Uses

of High-Purity

Copper

161

9.1.

Properties

9.2.

Constitution of the

9.3.

Nomenclature of the Copper-Rich Alloys

9.4.

Characteristics

9.5.

Characteristics of the

9.6.

Properties of the

9.7. 9.8.

172

9.10.

The Copper-Base Bearing Metals The Tin Bronzes Aluminum Bronze and Copper-Silicon

9.11.

Copper-Beryllium Alloys

177

9.12.

The Copper-Rich

184

9.13.

Copper and Copper-Base Alloys

9.9-

Common

164

Copper-Rich Alloys

.

.

.

165 167

and Uses of the High Brasses

168

Low

Brasses

Wrought

Brasses

171

Cast Brass and Cast Nickel Silver

172

Chapter 10. Alloys

and the Nickel

Silvers

174

Alloys

176

Copper-Nickel Alloys

Miscellaneous Heavy

in

170

Powder Metallurgy

Nonferrous

.

.

186

Metals and 190

10.1.

The White

10.2.

Lead and Tin

10.3.

Zinc and Zinc Base Alloys as Engineering Materials

Metals

191

as Engineering Materials

196 .

.

.

197

10.4.

Nickel and Nickel Base Alloys

199

10.5.

Cobalt Base Alloys

201

10.6.

Other Miscellaneous High Temperature Metals and Alloys

201

10.7.

The

202

10.8.

Metals and Alloys in Atomic Power Applications

Precious and Semi-Precious Metals and Alloys

.

.

.

....

203

Chapter 11. The Manufacture and Composition of Carbon and Alloy Steels

208

11.1.

Definitions of Ferrous Engineering Materials

210

11.2.

Iron Ore and the Manufacture of Pig Iron

212

11.3.

Acid and Basic Processes

216

Contents

xv

11.4.

Bessemer Processes

11.5.

Open-Hearth Processes

11.6.

Manufacture of High-Quality

11.7.

Wrought Iron

227

11.8.

Special Steel-making Processes

229

11.9.

Mechanical Treatment of Steel

217 220 Steels

by the

Electric

Processes

226

11.10.

Harmful Elements

11.11.

Manganese

in

231

Carbon and Alloys

Steels

11.13.

Carbon and Alloy Steels Carbon Monoxide, and Rimming and Killed Silicon and Other Degasifiers

11.14.

Other Elements

11.15.

Low-Alloy

11.16.

High-Alloy Steels

11.12.

....

in

233 236

Steels

.

.

.

237 239

239

Steels

.

.

240 241

Chapter

12.

12.1.

The

Allotropy of Iron

244

12.2.

Iron-Carbon Phase Diagram

245

12.3.

Phase Changes and Microstructures of Slowly Cooled Plain

12.4.

Isothermal Transformation in Steel

251

12.5.

The

254

12.6.

Effect of Alloying

12.7.

Effect of Alloying

12.8.

Effect of

258

12.9.

Effect

259

The

Carbon

Constitution of Steel

244

Steels

Effect of

247

Upon the Resulting Structure Elements Upon the Iron-Carbon Dia-

Cooling Rate

g™™

256

mation of

Chapter

Elements on the Isothermal Transfor-

Steel

257

Hot Working on Structure of Cold Working on Structure

13.1.

Fundamentals of Heat Treatment of Steel Grain Size and Grain Growth

13.2.

Controlling and Classifying Grain Size

13.3.

Effects of

13.4.

Hardenability

269

13.5.

Grain

270

13.6.

Quenching and Properties of Martensite

270

13.7.

The

273

13.

Size

Hot Working on Grain

Quenched Carbon

.

263 264

265

Size

267

and Hardenability

Instability of

.

Steels

XVI

Contents

13.8.

Retained Austenite and Cold Treatment

274

13.9.

Structural

and Other Changes

Tempering

274

Operations of Heat Treatment

278

Chapter

14.

The

in

14.1.

Heating Cycle

279

14.2.

Annealing

280

14.3.

Normalizing

280

14.4.

Spheroidizing

14.5.

Quenching

14.6.

Tempering

14.7.

Isothermal Treatments

14.8.

Case Hardening Processes

14.9.

Flame Hardening and Induction Hardening

for

281

Hardening

282

284 285 '

289 293

...

297

15.1.

Carbon-Steel Castings as Engineering Materials

....

298

15.2.

Factors Affecting the Properties of Carbon-Steel Castings

300

15.3.

Hot-Worked Carbon

302

15.4.

Effect of

Chapter

15.

Carbon Steel as an Engineering Material

Steels as Engineering Materials

Composition on

Carbon

Static Properties of

.

.

Hot-Worked

Steels

303

Composition on Other Properties

15.5.

Effect of

15.6.

Cold-Worked Carbon

15.7.

The Important

305

Engineering Materials

.

306

...

307

15.8.

General Effects of Cold Working on Strength and Ductility

308

15.9.

Variables Affecting the Properties of Cold-Worked Wire

.

311

.

.

312

.

.

312

Steels as

Properties of Cold- Worked Steel

Cold-Working on Dynamic Properties

15.10.

Effect of

15.11.

Heat-Treated Carbon Steels

15.12.

Effect of Section Size

Medium-Carbon Chapter

16.

on

as

.

.

Engineering Materials

.

the Properties of Heat-Treated

315

Steels

Low- Alloy Steels

as Engineering Materials

.

.

318

16.1.

Balanced Compositions

16.2.

General Effects of the Alloying Elements on Carbon Steel

320

16.3.

Effects of

....

322

16.4.

Effects of Nickel

16.5.

Effects of the

....

325

16.6.

Low-Alloy Structural Steels

in

Low- Alloy

319

Steels

Phosphorus, Manganese, and Silicon

and Chromium

Other

Common as

Alloying Elements

324

Engineering Materials

.

.

326

Contents

xvii

Composition and Properties of the Low-Alloy Structural

16.7.

Steels

327

16.10.

The S.A.E. Low-Alloy Steels The S.A.E. Low-Alloy Steels as Engineering The New Metallurgy of Low-Alloy Steels

16.11.

Similarity of Properties of Heat-Treated S.A.E. Low-Alloy

16.8. 16.9.

328 Materials

.

.

333

Steels

The

16.12.

Chapter

17.

331

334

Engineering Properties of the S.A.E. Low-Alloy Steels Hardf.nability

337

342

....

343

...

344

17.3.

Hardness and Hardenability in Carbon Steels Hardness and Hardenability in Low-Alloy Steels Cooling Rate and Hardenability

17.4.

Time Delay and

17.5.

Variables Affecting Hardenability

346

17.1. 17.2.

344

Hardenability

346

17.6.

Methods of Determining Hardenability

348

17.7.

The Jominy End-Quench

349

17.8.

Relation of the End-Quench Test to Actual Cooling Rates and the Selection of Steel by Hardenability

17.9

Hardenability Test

Virtues and Shortcomings of the

Jominy End-Quench Test

350 352

17.10.

Hardenability Bands

17.11.

Relation of Hardenability to Engineering Properties

17.12.

Relation of Tempering to Hardenability

356

17.13.

Fundamentals of Calculated Hardenability

356

17.14.

360

17.15.

The The

Chapter

18.

353 .

.

Accuracy of Calculated Hardenability Effect of

Boron on Hardenability

361

Special Purpose Steels

364

18.1.

Classes of Stainless Steels

18.2.

Constitution of

18.3.

Relation of the Constitution of High-Chromium Steels to

18.4.

Mechanical Properties of High

18.5.

Corrosion and Oxidation Resistance of High-Chromium

18.6.

The Constitution of The Role of Carbon

364

High-Chromium

366

Steels

Their Heat Treatment

Steels

18.7.

354

367

Chromium

Steels

...

369

370 18-8

372

in 18-8

374

xviii

Contents

18.8.

Properties of 18-8

18.9.

Recent Developments in Stainless

18.10.

376 378

Steels

Superstainless Steels

381

18.11.

High-Nickel Steels and Special Iron-Nickel Alloys

18.12.

Austenitic

Chapter

19.

Manganese

Tool

...

384 385

Steel

Die Steels, and Cemented Hard

Steels,

Carbides

389

19.1.

High-Carbon Tool

19.2.

390

Steels

19.3.

Low Alloy Tool Steels Medium Alloy Tool and

19.4.

High-Alloy Tool and Die Steels

397

19.5.

High Speed

398

19.6.

Function of Alloy Additions in Tool and Die

19.7.

Cast Alloys

404

19.8.

Cemented Carbide Tools

405

Chapter

20.

395

Die

396

Steels

Steels.

Steels

.

.

402

408

Cast Iron

20.1.

White Cast Iron

20.2.

Malleable Cast Iron as an Engineering Material

20.3.

Engineering Properties of Malleable Cast Iron

20.4.

Gray Cast Iron

20.5.

Structure of Gray Cast Iron

20.6.

Relation between Properties and Structure of Gray Cast

as

as

410

an Engineering Material

.... ....

410 410 412

an Engineering Material

414 415

Iron

416

20.7.

Effect of

Cooling Rate

20.8.

Effect of

Graphite Size on Structure and Properties

.

417

20.9.

Evaluation of Gray Cast Iron for Engineering Applications

419

20.10.

Nodular or Ductile Cast Iron

420

20.11.

Melting and Casting of Irons

422

20.12.

Ternary System of Iron, Carbon, and Silicon

425

20.13.

Heat Treatment of Cast Iron

430

20.14.

Normal and Alloy Elements

434

Chapter

21.

Machinability,

Wear

as

.

an Engineering Material

in Cast Iron

Resistance, and Deep-Draw-

438

ing Properties 21.1.

Variables Affecting Machinability

21.2.

Evaluation of Metallic Materials for Machinability

438 .

.

.

438

Contents

xix

21.S.

Free Machining Steels

21.4.

Relative Machinability of Steel and Nonferrous Alloys

21.5.

Types of Wear

21.6.

Variables Affecting

21.7.

Evaluation of Steel for

21.8.

Importance of Deep-Drawing Properties

445

21.9.

Evaluation of Steels for Deep Drawing

446

440

Wear Resistance Wear Resistance

443 444

Yield-Point Elongation, Stretched Strains, and ing Properties

21.11.

Deep-Drawing Properties of Nonferrous Alloys 22.

441

442

21.10.

Chapter

.

Deep Draw448

....

Corrosion and Oxidation

449 452

22.1.

Electrochemical Corrosion

452

22.2.

EMF

454

22.3.

Uniform Corrosion

456

22.4.

Galvanic or Two-Metal Corrosion

456

22.5.

Concentration Cell Corrosion

458

22.6.

Pitting

459

22.7.

Intergranular Corrosion

460

22.8.

Stress

22.9.

Dezincification

Series

and

Passivity

Corrosion

462 .

466

22.10.

Erosion-Corrosion

468

22.11.

Methods

469

22.12.

Corrosion Testing

471

22.13.

Liquid-Metal Corrosion

472

22.14.

High-Temperature Oxidation

472

22.15.

Formation of Oxides

473

22.16. 22.17.

Dependence of Oxides Growth upon Gas Pressure Dependence of Oxide Growth Upon Time

22.18.

Dependence of Oxide Growth Upon Temperature

22.19.

Oxidation Prevention

for

Combating Corrosion

.

.

.

477 .

.

.

Chapter 23. Effect of Temperature on Mechanical Properties of Metals 23.1. 23.2. 23.3.

The Importance of Creep The Engineering Significance of Creep The Creep to Rupture Curve

474

479 480

485 486 486 488

xx

Contents

23.4.

Determination of Creep

23.5.

Effect of Variables

23.6.

Fatigue and

23.7.

Structural Changes

23.8.

Variation of Other Properties with Temperature

23.9.

Design for Elevated Temperature Service

23.10.

Variation

489

on Creep

491

Combined Fatigue and Creep During Creep

Mechanical

Properties

at

493 495 .

.

.

499

Reduced Tempera500

tures 23.11.

Effects of Metallurgical Variables

23.12.

Design for Low-Temperature Service

Index

498

502

....

...

503

507

Engineering

Metallurgy

Metallurgy and Engi nee r i ng

CHAPTER 1

Don

R. Mosher, B.S., Assistant Professor of Mechanical

Engineering, University of Colorado, Boulder, Colorado

1.1.

Metallurgy as an Art

METALLURGICAL

knowledge had

its

begin-

nings in the stone age

when some ancient craftsman

difference in behavior

amongst certain of the "rocks" with which he was

working.

The

first

recognized the

stones familiar to this primitive artisan were hard and

and were capable of being fashioned into tools and weapons only by tedious shaping, chip by chip. His first encounter with metal then, undoubtedly native copper or gold, must have been an exciting experience. Here was a substance which, instead of fracturing, yielded to the blows of his stone hammer. Here was a material which could be formed brittle,

much more precisely, which was pleasing to the eye, which could be worked to a keener edge, and which, moreover, somehow acquired greater strength the more it was worked. From carbon

the use of native metal to the deliberate reduction of an ore by a long step, and one which is the subject of much interesting

is

speculation.

It

seems likely that the

first

such reduction was accidental-

possibly the result of a fortunate combination of circumstances in which the heat of a campfire, together with carbon from the charred logs

succeeded in reducing copper ore contained in the surrounding stones, On other occasions the stones may have contained additional metals such as tin, and the result was a remarkably stronger metal. In time, the relationship between the

fire,

stones was recognized,

and the

the charred logs,

and the particular types first metallurgist, began

discoverer, the

of

to

produce metals at will. He and his progeny of the next several thousand years have accumulated a mass of information concerning the effects of variables in processing

upon

the properties of the final product. 1

Engineering Metallurgy

2

1.2.

Metallurgy as a Science

Questions concerning the reasons why these variables resulted in the observed

effects

must certainly have been present

in the

minds of

pioneers long before the means were available to answer them.

these

With the

advent of the microscope and the X-ray, these inquiring minds began to supply the answers.

The science of metallurgy really began when Sorby, a British scientist, reported in 1864 the results of his investigations on the use of the microscope to study the structure of meteoric iron.

This was followed by same general field by Martens in Germany, reported in 1878. The work of these two scientists, however, aroused little interest at the time, and nothing further was accomplished until Sorby showed to the British Iron and Steel Institute in 1886 some photomicrographs of iron and steel. This aroused much interest in the internal structure of metals, and from 1890 to 1920 many distinguished metallurgists devoted studies in the

themselves to developing a science of physical metallurgy.

The paramount

early problem of metallurgy, which fairly cried for was that of the hardening of steel— why steel containing considerable carbon was soft when cooled slowly from a red heat but hard when cooled rapidly from the same temperature. This problem occupied most of the workers in the science of metals for more than two decades. solution,

Despite the efforts of

many

brilliant minds,

which resulted

in a

of published literature that amazes present-day metallurgists,

volume

little

that

was wholly decisive was accomplished until confirmatory X-ray crystallography methods came into use about forty years ago. Although some cynics say that the X-ray has created more problems than it has solved, X-ray crystallography has been a useful tool in the study of the structure of metals and the constitution of alloys. In the past three decades the science of physical metallurgy has changed remarkably. Always closely related to chemistry and physics, it has been greatly affected by the revolution that has occurred in these two sciences since 1920. The gap between chemistry and physics has been largely eliminated, and, as these sciences came together, the science of metallurgy changed from simple speculations on the structure of metals and alloys, as affected by composition or mechanical or thermal treatment and as observed by the microscope, to speculations which involve such complex abstractions as spinning electrons, statistical mechanics, electromagnetic theory, quantum theory, wave mechanics, and thermodynamics. Present-day physical metallurgists are inclined to smile condescendingly at the battles over

beta iron, cement carbon, and amorphous metal which

Metallurgy and Engineering filled the transactions of the

It is

not

at all certain that

years from

3

metallurgical societies forty or

fifty

years ago.

even broader smiles will not be in order thirty

now

over the discussions of free energy, entropy, and mosaic filling our journals at the present time. Especially apropos in this connection are the words of a venerable man of science, structure

which are

Ambrose Fleming, who presented a paper to the first meeting of the London in 1873 and who, in a formal address to the same body of scientists on "Physics and Physicists of the Eighteen Seventies,"* summarized his seventy years of experience by saying: Sir

Physical Society of

When we come to look back then on the world of physicists during the eighteen seventies, what we find is that their inventions, discoveries of fact, and ascertained principles remain with us today of permanent value, forming part of our useful knowledge. But their theories and speculations as to underlying causes and nature have nearly all passed away. Perhaps it will

also be the hence a fellow of the physics of the nineteen thirties, he will have to record the great additions then made to knowledge of physical facts. But he may also have to say that our explanations and theories concerning them have all vanished, or at least been replaced by others also destined in turn to pass

same with our present-day work. Physical Society gives a talk on the

If

some

sixty years

away.

1.3.

Metallurgy and Engineering

Until about forty years ago there was

know anything about metallurgy

since

little

need for the engineer to

untreated carbon

steel,

hot-

rolled or cold-drawn,

was used for at least 95 per cent of steel structures and machines. The engineer was interested primarily in four propertiestensile strength, yield point, elongation, and reduction of area-and in having available an ample supply of cheap steel which, in addition to meeting specifications for tensile properties, would machine easily and fabricate readily. It was considered sound engineering practice to build machines and structures that would carry a much higher load than was

anticipated; weight was

synonymous with quality, and the heavier the structure the better the design. High factors of safety were used; consequently slight variations in quality, such as lack of structural geneity, surface irregularities,

and numerous

others,

made

little

homoor no

difference in designing.

This is no longer true. Weight and the strength-weight ratio (tensile strength divided by specific gravity) have become very important. Under the leadership of the automotive and aircraft industries engineers have come to realize that excess weight not only indicates poor design but is an inexcusable economic loss. The experience of the automotive

and

•Nature,

v.

143, 1939, pp. 99-102.

Engineering Metallurgy

4

the aeronautical engineer in designing lightweight structures and machines stimulated similar efforts in other fields of engineering. This

shown by the recent developments in machine tools, in lightweight way rolling stock, and even in bridge and building structures. It

is

rail-

of course, self-evident that the present-day emphasis on light

is,

weight in engineering design

as exemplified by the automobile, airplane, and the streamlined train is directly related to the development of new types of steels and light nonferrous alloys and to new treatments for these materials. It is a moot question whether the metallurgist or the engineer was responsible for most of this development. Enthusiastic metallurgists insist that engineering progress has been the direct result of metallurgical progress; that engineers only improved their tools, machines, and structures because metallurgical art and science had produced new metallic materials for the engineer to use. There is no doubt that many engineers are too conservative and that engineering progress has at times lagged behind progress in metallurgy. On the other hand, examples could be cited where the metallurgist did not improve his product until insistent engineering demand forced it upon him. A discussion of whether this advance was pioneered by the metallurgist or the engineer is as futile as arguing whether the egg or the chicken came first; the essential fact is that important changes have taken place and that the

engineer should

accompanied It

know something

of the metallurgical progress that has

his changes in design.

therefore, the purpose of this

is,

book

to outline the recent develop-

ments

in metallurgical art

mean

that there are long descriptions of melting

and

This does not and refining, or of mechanical and heat treatment, or of thermodynamics and wave mechanics; it does mean, however, that sufficient details of the present state of metallurgical art and science are given so that engineers may recognize the importance of the variables, inherent in the manufacture and treatment of metals and alloys, that affect the engineering properties and the suitability of these materials for engineering applications. in metallurgical science.

QUESTIONS 1.

Distinguish between the art and the science of metallurgy.

2.

What

research tools have most profoundly influenced the development of

metallurgical science? 3. 4. 5.

To what

How Why

is

other sciences

is

metallurgy closely related?

and in metallurgy inter-related? becoming increasingly important for engineers to understand the

progress in engineering

is it

fundamentals of metallurgy?

CHAPTER

Fundamental Structure of Metals and Alloys Leonard B. Gulbransen, Ph.D., Associate Washington University, St. Louis, Missouri

Professor,

Joseph William Spretnak, Ph.D., Professor of MetalEngineering,

lurgical

The Ohio

State

University,

Columbus, Ohio

In RECENT and the application of wave mechanics lurgy has resulted in a

much

years the study of the solid state to solid state physics

and metaland

clearer picture of the structure of metals

Physical and mechanical properties of the metals, such as tensile strength, ductility, electrical conductivity, diffusion, etc are dependent on structure, sometimes to a marked degree. For this reason it is desiralloys.

able to discuss the structure of solids,

metals and

and

in particular the structure of

alloys.

2.1. Building Blocks of Matter All metals are aggregates of atoms. Atoms consist of a nucleus and one or more planetary electrons. In general, except for applications of the nuclear reactions, it can be assumed that the atomic nucleus consists of

positively charged protons,

of the mass of the

sum

atom

is

and neutrons with no

electrical charge.

Most

concentrated in the nucleus and is equal to the and neutrons in the nucleus. Negatively

of the masses of the protons

charged electrons

sufficient to balance the positively charged protons in the nucleus, resulting in an electrically neutral atom, are found outside the nucleus. Electrons may be thought of as point particles, with a definite

mass and electrical charge; however, their motion must be described in terms of an associated wave. The part of science that deals with this problem is known as wave mechanics. The fundamental equation de-

Engineering Metallurgy

6

wave

scribing the motion of an electron and accompanying

is

De

Broglie's

equation: A

where h

Planck's constant (6.62

is

V

electron,

= h/mV

is

x 10—27

the velocity of the electron,

erg-sec)

and A

,

is

m

is

the mass of the

the associated wave-

Practical use of this equation is made in electron diffraction equipment. Application of De Broglie's equation, and Heisen berg's uncertainty principle, which states that the position and momentum (mV)

length.

of a particle cannot be exactly determined simultaneously, result in a

somewhat

different idea of

atomic structure than the

classical picture of

a nucleus and planetary electrons in definite fixed orbits. of the equations of

wave mechanics

Application

results in a picture of the

atom

as a

positively charged nucleus, with electrons in discrete, but "smeared out" orbits.

The

limits of the orbit

can be described

in

terms of a probability

function, in which, the probability of finding the electron at the center of

the orbit

is

maximum, but

finite

and small

probabilities exist for finding

the electron at the limits of the "smeared out" orbit. This description of

atomic structure

1

s

is

sometimes described

2 p State

State

Fig. 2.1.

as

an electron cloud picture.

3

d

State

Electron cloud diagrams of hydrogen atom.

In the solution of the wave equation for a given atom, the electrons are quantum numbers; n, I, m t and m s . The quantum

characterized by four

quantum number, and is related to the n may have any integral value from + to infinity. The quantum number / is related to the angular momentum of the electron and may have any integral value from to (n-1) The quantum number m, is related to the magnetic moment of the elec-

number n

is

called the principal

total energy of the electron.

Number

1

.

Fundamental Structure of Metals and Alloys tron and

may have any

value from

to

related to the rotation of the electron

±

I.

about

7

The quantum number m, is its own axis, and may have

values of ± i/2 . The four quantum numbers determine the energy of the electron in various states, with the result that an atomic system may be fully described by specifying the values for the each electron.

A

quantum numbers

for

wave mechanics is the Pauli Exclusion Principle no two electrons in the same atom can have the same four quantum numbers. This principle in effect restricts a given electron to one and only one energy slate in a single atom. If then, two atoms are brought together to form a molecule, the electrons of each atom must occupy different energy states or energy levels. The idea of energy levels is important with regard to molecule formation and also to the formafurther result of

which

states that

tion of the solid state.

MAXIMUM NUMBER OF ELECTRONS 5P

10 6

to 5s

2

Up 3D

"i

Us

IS Fig. 2.2.

Energy

level

diagram

of

an atom.

As an example of the above principles, consider the hydrogen atom. consists of a proton, + 1 charge, and a mass of approximately one atomic unit. The hydrogen atom must then possess one electron. In the lowest energy state, this electron would have an energy described by the quantum numbers n = 1, / = 0, = 0, and m, = + \/2 The next atom in the periodic system, helium, with a + 2 charge on the

The hydrogen atom

m

;

.

Engineering Metallurgy

8

nucleus must possess two electrons.

The quantum numbers

describing

would then be: n, =1, I, = 0, mj, = 0, m, l = + \/z and n, = 1, l„ = 0, wijj = 0, and m sl = \/z These two electrons have very nearly the same energy, the only difference being related to the spin quantum numbers m„, and m tl Both electrons are confined to the same major energy level with n = 1, and only these two electrons can occupy this level. The next atom in the periodic system, lithium, must possess three electrons. Two of the electrons have the same quantum numbers as those for helium, but the third, n = 2, I = 0, m = 0, and m, = + i/2 these electrons, in order to fulfdl Pauli's exclusion principle, ,

—

.

.

.

A more common method an atom

is

of representing the electronic configuration of

to use the terminology of the spectroscopist, in

which the

quantum number n is listed, followed by a letter designating quantum number /, and indicating by a superscript the number of

principal the

For most metallurgical applicabetween energy states with different values for m and m, is so small that it may be neglected. According to this method of representation the hydrogen atom in its lowest energy state may be described as being in a (Is) 1 state; the helium atom in a (Is) 2 state; the electrons in this particular energy state. tions, the difference

(

lithium atom in a (Isf

nated by s for

I

=

0,

p

(2s)

for

/

•

=

state etc. 1,

d

for

/

Pauli's exclusion principle, the s state electrons, the

p

maximum

state a

The quantum number

=

2,

and

may

/ for

/

contain a

=

3.

I

is

desig-

By applying

maximum

of two

of six electrons, and the d state a maxi-

mum of ten electrons. ATOMIC NUMBER

Fic. 2.S.

ELEMENT

ELECTI ION CONFICUR ATION

1

Hydrogen

(Is)

2

Helium

(Is)'

3

Lithium

(Is)'

1

(2s)

1

1

i

Beryllium

(Is)'

(2s)

5

Boron

(Is)'

(2s)'(2p)'

6

Carbon

(Is)'

(2s)'(2p)'

7

Nitrogen

(Is)'

(2s) '(2p) 3

fi

Oxygen

(Is)'

(2s)'(2p)