Welding Metallurgy (3RD)

Discover the extraordinary progress that welding metallurgy has experienced over the last two decades

Welding Metallurgy, 3rd Edition is the only complete compendium of recent, and not-so-recent, developments in the science and practice of welding metallurgy. Written by Dr. Sindo Kou, this edition covers solid-state welding as well as fusion welding, which now also includes resistance spot welding. It restructures and expands sections on Fusion Zones and Heat-Affected Zones. The former now includes entirely new chapters on microsegregation, macrosegregation, ductility-dip cracking, and alloys resistant to creep, wear and corrosion, as well as a new section on ternary-alloy solidification. The latter now includes metallurgy of solid-state welding. Partially Melted Zones are expanded to include liquation and cracking in friction stir welding and resistance spot welding. New chapters on topics of high current interest are added, including additive manufacturing, dissimilar-metal joining, magnesium alloys, and high-entropy alloys and metal-matrix nanocomposites.

Dr. Kou provides the reader with hundreds of citations to papers and articles that will further enhance the reader's knowledge of this voluminous topic. Undergraduate students, graduate students, researchers and mechanical engineers will all benefit spectacularly from this comprehensive resource.

The new edition includes new theories/methods of Kou and coworkers regarding:

Predicting the effect of filler metals on liquation cracking
An index and analytical equations for predicting susceptibility to solidification cracking
A test for susceptibility to solidification cracking and filler-metal effect
Liquid-metal quenching during welding CSM 404

15.2.2 Mechanism II: Alloy with Co < CSM and no AxBy or Eutectic 405

15.2.3 Mechanism III: Alloy with Co < CSM and AxBy or Eutectic 405

15.2.4 Additional Mechanisms of Liquation 409

15.3 Directional Solidification of Liquated Material 411

15.4 Grain-Boundary Segregation 411

15.5 Loss of Strength and Ductility 413

15.6 Hydrogen Cracking 414

15.7 Effect of Heat Input 414

15.8 Effect of Arc Oscillation 415

Examples 416

References 417

Problems 418

16 Liquation Cracking 419

16.1 Liquation Cracking in Arc Welding 419

16.1.1 Crack Susceptibility Tests 421

16.1.1.1 Varestraint Testing 421

16.1.1.2 Circular-Patch Testing 422

16.1.1.3 Hot Ductility Testing 423

16.1.2 Mechanism of Liquation Cracking 423

16.1.3 Predicting Effect of Filler Metal on Crack Susceptibility 424

16.1.4 Factors Affecting Liquation Cracking 430

16.1.4.1 Filler Metal 430

16.1.4.2 Heat Source 430

16.1.4.3 Degree of Restraint 431

16.1.4.4 Base Metal 431

16.2 Liquation Cracking in Resistance Spot Welding 434

16.3 Liquation Cracking in Friction Stir Welding 434

16.4 Liquation Cracking in Dissimilar-Metal FSW 439

Examples 445

References 446

Problems 449

Part IV The Heat-Affected Zone 451

17 Introduction to Solid-State Transformations 453

17.1 Work-Hardened Materials 453

17.2 Heat-Treatable Al Alloys 455

17.3 Heat-Treatable Ni-Base Alloys 458

17.4 Steels 461

17.4.1 Fe-C Phase Diagram and CCT Diagrams 461

17.4.2 Carbon Steels 463

17.4.3 Dual-Phase Steels 470

17.5 Stainless Steels 471

17.5.1 Types of Stainless Steels 471

17.5.2 Sensitization of Unstabilized Grades 473

17.5.3 Sensitization of Stabilized Grades 473

17.5.4 σ-Phase Embrittlement 475

Examples 475

References 475

Problems 477

18 Heat-Affected-Zone Degradation of Mechanical Properties 479

18.1 Grain Coarsening 479

18.2 Recrystallization and Grain Growth 480

18.3 Overaging in Al Alloys 483

18.3.1 Al-Cu-Mg (2000-Series) Alloys 483

18.3.1.1 Microstructure and Strength 483

18.3.1.2 Effect of Welding Parameters or Process 488

18.3.2 Al-Mg-Si (6000-Series) Alloys 489

18.3.2.1 Microstructure and Strength 489

18.3.2.2 Effect of Welding Processes and Parameters 491

18.3.3 Al-Zn-Mg (7000-Series) Alloys 492

18.4 Dissolution of Precipitates in Ni-Base Alloys 494

18.5 Martensite Tempering in Dual-Phase Steels 498

Examples 500

References 500

Further Reading 502

Problems 502

19 Heat-Affected-Zone Cracking 505

19.1 Hydrogen Cracking in Steels 505

19.1.1 Cause 505

19.1.2 Appearance 506

19.1.3 Susceptibility Tests 507

19.1.4 Remedies 508

19.1.4.1 Preheating 508

19.1.4.2 Postweld Heating 509

19.1.4.3 Bead Tempering 509

19.1.4.4 Use of Low-H Processes and Consumables 509

19.1.4.5 Use of Lower-Strength Filler Metals 509

19.1.4.6 Use of Austenitic-Stainless-Steel Filler Metals 510

19.2 Stress-Relief Cracking in Steels 510

19.3 Lamellar Tearing in Steels 514

19.4 Type-IV Cracking in Grade 91 Steel 517

19.5 Strain-Age Cracking in Ni-Base Alloys 519

Examples 524

References 524

Further Reading 527

Problems 528

20 Heat-Affected-Zone Corrosion 529

20.1 Weld Decay of Stainless Steels 529

20.2 Weld Decay of Ni-Base Alloys 533

20.3 Knife-Line Attack of Stainless Steels 534

20.4 Sensitization of Ferritic Stainless-Steel Welds 536

20.5 Stress Corrosion Cracking of Austenitic Stainless Steels 537

20.6 Corrosion Fatigue of Al Welds 538

Examples 538

References 539

Further Reading 540

Problems 540

Part V Special Topics 541

21 Additive Manufacturing 543

21.1 Heat and Fluid Flow 543

21.2 Residual Stress and Distortion 545

21.3 Lack of Fusion and Gas Porosity 547

21.4 Grain Structure 550

21.5 Solidification Cracking 550

21.6 Liquation Cracking 553

21.7 Graded Transition Joints 558

21.8 Further Discussions 560

Examples 560

References 561

Further Reading 563

Problems 564

22 Dissimilar-Metal Joining 565

22.1 Introduction 565

22.2 Arc and Laser Joining 565

22.2.1 Al-to-Steel Arc Brazing 566

22.2.1.1 Effect of Lap Joint Gap 569

22.2.1.2 Effect of Heat Input 575

22.2.1.3 Effect of Ultrasonic Vibration 577

22.2.1.4 Effect of Preheating 578

22.2.1.5 Effect of Postweld Heat Treatment 578

22.2.1.6 Butt Joint 579

22.2.2 Al-to-Steel Laser Brazing 579

22.2.3 Al-to-Steel Laser Welding 580

22.2.4 Mg-to-Steel Brazing 582

22.2.5 Al-to-Mg Welding 583

22.3 Resistance Spot Welding 583

22.3.1 Al-to-Steel RSW 583

22.3.2 Mg-to-Steel RSW 586

22.3.3 Al-to-Mg RSW 588

22.4 Friction Stir Welding 589

22.4.1 Al-to-Cu FSSW 589

22.4.2 FSSW of Al to Galvanized Steel 592

22.4.3 Effect of Coating on Al-to-Steel FSSW 597

22.5 Other Solid-State Welding Processes 603

22.5.1 Friction Welding 603

22.5.2 Explosion Welding 606

22.5.3 Magnetic Pulse Welding 607

Examples 608

References 609

Further Reading 612

Problems 612

23 Welding of Magnesium Alloys 613

23.1 Spatter 613

23.1.1 Spatter in Mg GMAW 613

23.1.2 Mechanism of Spatter 614

23.1.3 Elimination of Spatter 614

23.1.4 Irregular Weld Shape and Its Elimination 617

23.2 Porosity 618

23.2.1 Porosity in Mg GMAW 618

23.2.2 Mechanisms of Porosity Formation and Elimination 620

23.2.3 Comparing Porosity in Al and Mg Welds 621

23.3 Internal Oxide Films 622

23.3.1 Mechanism 622

23.3.2 Remedies 624

23.4 High Crowns 625

23.4.1 Mechanism of High-Crown Formation 625

23.4.2 Reducing Crown Height 627

23.5 Grain Refining 628

23.5.1 Ultrasonic Weld Pool Stirring 628

23.5.2 Arc Pulsation 629

23.5.3 Arc Oscillation 629

23.6 Solidification Cracking 629

23.7 Liquation Cracking 629

23.7.1 A Simple Test for Crack Susceptibility 631

23.7.2 Effect of Filler Metals 634

23.7.3 Effect of Grain Size 636

23.8 Heat-Affected Zone Weakening 636

Examples 638

References 640

Further Reading 641

Problems 641

24 Welding of High-Entropy Alloys and Metal-Matrix Nanocomposites 643

24.1 High-Entropy Alloys 643

24.1.1 Solidification Microstructure 643

24.1.2 Weldability 644

24.2 Metal-Matrix Nanocomposites 646

24.2.1 Nanoparticles Increasing Weld Size 646

24.2.2 Nanoparticles Refining Microstructure 648

24.2.3 Nanoparticles Reducing Cracking During Solidification 650

24.2.4 Nanoparticles Allowing Friction Stir Welding 651

Examples 653

References 654

Further Reading 655

Problems 655

Appendix A: Analytical Equations for Susceptibility to Solidification Cracking 657

Index 659