Principles of welding

PRINCIPLES OF WELDING Processes, Physics, Chemistry, and Metallurgy......Page 2
CONTENTS......Page 8
PREFACE......Page 24
I THE PROCESS AND PROCESSES OF WELDING......Page 28
1.1 What Is Welding?......Page 30
1.2 The Evolution of Welding as a Process......Page 33
1.3 The Nature of an Ideal Weld: Achieving Continuity......Page 34
1.4 Impediments to Making Ideal Welds in the Real World......Page 37
1.5 What It Takes to Make a Real Weld......Page 39
1.6 Advantages and Disadvantages of Welding......Page 41
References and Suggested Reading......Page 42
2.1 Why Classify Processes?......Page 44
2.2 Mechanisms for Obtaining Material Continuity......Page 45
2.3 The Roles of Temperature and Pressure......Page 48
2.4.1 Fusion Versus Nonfusion......Page 50
2.4.2 Pressure Versus Nonpressure......Page 52
2.4.3 Energy Sources for Welding......Page 53
2.4.4 Interface Relationships and Classification by Energy Transfer Processes......Page 54
2.4.5 Other Bases for Classification and Subclassification......Page 59
2.5 Allied Processes......Page 62
2.6 The AWS Classification Scheme......Page 64
References and Suggested Readings......Page 66
3.1 General Description of Fusion Welding Processes......Page 67
3.2.1 Oxyfuel Gas Welding......Page 68
3.2.2 Aluminothermic Welding......Page 73
3.3 Electric Arc Welding Processes......Page 76
3.3.1 Nonconsumable Electrode Arc Welding Processes......Page 77
3.3.1.1 Gas-Tungsten Arc Welding......Page 78
3.3.1.2 Plasma Arc Welding......Page 82
3.3.1.3 Magnetically Impelled Arc Butt Welding......Page 84
3.3.2.1 Gas-Metal Arc Welding......Page 87
3.3.2.2 Shielded-Metal Arc Welding......Page 91
3.3.2.3 Flux-Cored Arc Welding......Page 93
3.3.2.4 Submerged Arc Welding......Page 95
3.3.2.5 Electrogas Welding......Page 96
3.3.2.6 Electroslag Welding......Page 97
3.4.1 Resistance Spot, Resistance Seam, and Projection Welding......Page 98
3.4.2 Flash, Upset, and Percussion Welding......Page 101
3.5 High-Intensity Radiant Energy or High-Density Beam Welding Processes......Page 104
3.5.1 High-Energy-Density (Laser and Electron) Beam Welding Processes......Page 107
3.5.2 Focused IR and Imaged Arc Welding......Page 113
3.5.3 Microwave Welding......Page 115
3.6 Summary......Page 119
References and Suggested Reading......Page 120
4.1 General Description of Nonfusion Welding Processes......Page 121
4.2 Pressure (Nonfusion) Welding Processes......Page 124
4.2.1 Cold Welding Processes......Page 125
4.2.2 Hot Pressure Welding......Page 126
4.2.2.1 Pressure Gas Welding......Page 127
4.2.2.2 Forge Welding......Page 128
4.2.3 Roll Welding......Page 129
4.2.4 Explosion Welding......Page 130
4.3 Friction Welding Processes......Page 132
4.3.2 Direct-Drive Versus Inertia-Drive (Friction) Welding......Page 134
4.3.3 Angular and Linear Reciprocating (Friction) Welding......Page 135
4.3.4 Ultrasonic (Friction) Welding......Page 136
4.3.5 Friction Stir Welding......Page 139
4.4 Diffusion Joining Processes......Page 141
4.4.1 Diffusion Welding......Page 142
4.4.1.4 Continuous Seam Diffusion Welding......Page 145
4.4.3 Combined Forming and Diffusion Welding......Page 146
4.6 Inspection and Repair of Nonfusion Welds......Page 147
References and Suggested Reading......Page 150
II THE PHYSICS OF WELDING......Page 152
5.2 Sources of Energy for Welding......Page 154
5.3.1 Energy Available at a Source (Energy Level or Capacity)......Page 155
5.3.3 Source Intensity or Energy Density......Page 157
5.3.4 Energy Distribution......Page 158
5.4 Energy Input to a Weld......Page 159
5.6 Transfer Efficiency of Processes......Page 161
5.7 Effects of Deposited Energy: Good and Bad......Page 165
5.7.1 Desirable Melting, Fluxing, or Softening......Page 166
5.7.2 Adverse Effects of Heat in and Around the Weld......Page 168
5.8 Effects of Energy Density and Distribution......Page 169
5.9 Summary......Page 171
References and Suggested Reading......Page 173
6.1 General Description of the Flow of Heat in Welds......Page 174
6.2.1 Types of Weld Joints......Page 175
6.2.2 General Weld Design Guidelines......Page 179
6.3 The Welding Thermal Cycle......Page 181
6.4 The Generalized Equation of Heat Flow......Page 185
6.5 Analysis of Heat Flow During Welding......Page 188
6.5.1 Rosenthal's Simplified Approach......Page 189
6.5.2 Modifications to Rosenthal's Solutions......Page 192
6.5.3 Dimensionless Weld Depth Versus Dimensionless Operating Parameter......Page 194
6.6 Effect of Welding Parameters on Heat Distribution......Page 195
6.7.1 Zones in Fusion-Welded Materials......Page 199
6.7.2 Simplified Equations for Approximating Welding Conditions......Page 200
6.7.2.3 Solidification Rate......Page 201
6.7.2.4 Cooling Rates......Page 202
6.8 Weld Simulation and Simulators......Page 203
References and Suggested Reading......Page 205
7.1 Origin of Thermal Stresses......Page 208
7.2 Distortion Versus Residual Stresses......Page 210
7.2.1 Causes of Residual Stresses in Weldments......Page 212
7.2.1.1 Residual Stresses From Mismatch......Page 213
7.2.1.2 Residual Stresses From Nonuniform, Nonelastic Strains......Page 216
7.2.2 Causes of Distortion in Weldments......Page 217
7.3 Typical Residual Stresses in Weldments......Page 218
7.4 Effects of Distortion......Page 221
7.5 Effects of Residual Stresses......Page 223
7.6 Measurement of Residual Stresses in Weldments......Page 224
7.6.1.1 A Sectioning Technique Using Electric-Resistance Strain Gauges......Page 226
7.6.1.2 The Rosenthal-Norton Section Technique......Page 228
7.6.1.4 The Gunnert Drilling Technique......Page 229
7.6.2 The X-ray Diffraction Technique......Page 231
7.7.2 Prevention Versus Remediation......Page 233
7.7.3 Controlling or Removing Residual Stresses......Page 234
7.7.4 Controlling or Removing Distortion......Page 235
7.8 Numerical Methods for Estimating Residual Stresses......Page 237
7.9 Summary......Page 238
References and Suggested Reading......Page 241
8.1 Electricity for Welding......Page 243
8.2.1 The Physics of an Electric Arc......Page 250
8.2.1.3 Arc Temperature......Page 251
8.2.1.5 Arc Electrical Features......Page 253
8.2.1.6 Effect of Magnetic Fields on Arcs......Page 255
8.2.2 Volt-Ampere Characteristics for Welding......Page 258
8.2.2.2 Constant-Voltage Power Sources......Page 259
8.3 The Physics of a Plasma......Page 261
8.4.1 Joule Heating......Page 264
8.4.2 The Resistance Welding Cycle......Page 266
8.4.3 Resistance Welding Power Supplies......Page 268
8.5 The Physics of Electron Beams......Page 270
8.5.1 Electron-Beam Generation......Page 272
8.5.2 Electron-Beam Control......Page 275
8.5.3 Role of Vacuum in EB Welding......Page 279
8.5.4 Electron-Beam-Material Interactions......Page 280
8.6.2 Laser Generation......Page 283
8.6.2.1 Nd:YAG Lasers......Page 285
8.6.3 Laser-Beam Control......Page 286
8.6.4 Laser-Beam-Material Interactions......Page 287
8.6.5 Benefits of Laser-Beam and Electron-Beam Welding......Page 290
8.7.2 Flame Temperature......Page 292
8.8 The Physics of Converting Mechanical Work to Heat......Page 293
8.9 Summary......Page 295
References and Suggested Reading......Page 296
9.1 Forces Contributing to Molten Metal Transfer in Welding......Page 297
10.1 Origin of Convection......Page 318
10.1.1 Generalities on Convection in Weld Pools......Page 319
10.1.2 Buoyancy or Gravity Force......Page 321
10.1.3 Surface Gradient Force or Marangoni Convection......Page 322
10.1.4 Electromotive Force or Lorentz Force......Page 323
10.1.5 Impinging or Friction Force......Page 324
10.2 Effects of Convection......Page 325
10.2.1 Effect of Convection on Penetration......Page 327
10.2.2 Effect of Convection on Macrosegregation......Page 328
10.2.3 Effect of Convection of Porosity......Page 331
10.3 Enhancing Convection......Page 332
10.4 Weld Pool Oscillation......Page 333
10.5 Weld Pool Evaporation and Its Effects......Page 334
References and Suggested Reading......Page 337
9.1.1 Gas Pressure Generation at Flux-Coated or Flux-Cored Electrode Tips......Page 298
9.1.5 Explosive Evaporation......Page 299
9.1.8 Surface Tension......Page 300
9.2 Free-Flight Transfer Modes......Page 301
9.2.1 Globular Transfer......Page 302
9.2.2 Spray Transfer......Page 303
9.3 Bridging of Short-circuiting Transfer Modes......Page 305
9.4 Pulsed-Arc or Pulsed-Current Transfer......Page 306
9.5 Slag-Protected Transfer......Page 307
9.6 Variations of Major Transfer Modes......Page 308
9.7.1 Effects on Transition Current......Page 309
9.7.2 Shielding Gas Effects......Page 312
9.7.3 Process Effects......Page 314
9.7.4 Operating Mode or Polarity Effects......Page 315
References and Suggested Reading......Page 316
III THE CHEMISTRY OF WELDING......Page 340
11 MOLTEN METAL AND WELD POOL REACTIONS......Page 342
11.1 Gas-Metal Reactions......Page 343
11.1.1 Gas Dissolution and Solubility in Molten Metal......Page 344
11.1.2 Solid Solution Hardening and Phase Stabilization......Page 350
11.1.3 Porosity Formation......Page 353
11.1.4 Embrittlement Reactions......Page 354
11.1.5 Hydrogen Effects......Page 355
11.1.5.1 Hydrogen Embrittlement......Page 356
11.1.5.2 Hydrogen Porosity......Page 358
11.1.5.3 Hydrogen Cracking......Page 359
11.2.1 Shielding Gases......Page 360
11.2.3 Vacuum......Page 362
11.2.4 Self-Protection and Self-Fluxing Action......Page 363
11.3.1 Deoxidizing/Denitriding (or Killing) Versus Protection......Page 364
11.3.2 Flux-Protected Welding Processes......Page 366
11.3.3 Shielding Capacities of Different Processes......Page 367
11.3.4 Slag Function......Page 368
11.3.6 Flux Types......Page 369
11.3.8 Basicity Index......Page 371
11.3.9 Thermodynamic Model for Welding Slag- Metal Reactions......Page 375
11.4 Summary......Page 381
References and Suggested Reading......Page 383
12 WELD CHEMICAL HETEROGENEITY......Page 386
12.1 Weld (Pool) Dilution......Page 387
12.2 Microsegregation and Banding in the Weld Metal......Page 390
12.3 Unmixed and Partially Mixed Zones......Page 392
12.4 Impurities in the Weld Metal......Page 393
12.5 Macrosegregation in Dissimilar Welds......Page 395
References and Suggested Reading......Page 397
IV THE METALLURGY OF WELDING......Page 400
13 WELD FUSION ZONE SOLIDIFICATION......Page 402
13.1 Equilibrium Versus Nonequilibrium......Page 405
13.2.1 Criteria for Equilibrium at TE, and Constant Pressure......Page 408
13.2.2 Pure Material Growth Modes......Page 409
13.2.3.1 Homogeneous Nucleation......Page 411
13.2.3.3 Effect of Radius of Curvature on Supercooling......Page 415
13.2.3.4 Heterogeneous Nucleation......Page 416
13.2.4 Epitaxial and Competitive Growth......Page 419
13.2.5 Effect of Weld Pool Shape on Structure......Page 422
13.2.6 Competing Rates of Melting and Solidification......Page 426
13.3 Equilibrium Solidification of an Alloy......Page 429
13.3.2 Equilibrium Solidification of a Hypothetical Binary Alloy (Case 1)......Page 430
13.4.1 Boundary Conditions for Solidification of Alloys......Page 433
13.4.2 Equilibrium Maintained Throughout the System at all Times: Microscopic Equilibrium (Case 1)......Page 434
13.4.3 Complete Liquid Mixing/No Diffusion in the Solid (Case 2)......Page 435
13.4.3.1 Expression for the Composition of Solid at the Advancing Solid-Liquid Interface......Page 437
13.4.3.2 Calculation of the Average Composition of the Solid for Case 2......Page 438
13.4.4 No Liquid Mixing/No Diffusion in the Solid (Case 3)......Page 440
13.4.4.2 Expression for the Initial Transient in the Composition of the Solid Formed......Page 447
13.4.4.3 Some Limitations of the Classic Models......Page 448
13.4.5.2 Nonequilibrium Phases......Page 449
13.5.1 Interdendritic Microsegregation......Page 450
13.5.2 Solidus Suppression......Page 452
13.5.3.1 Constitutional Supercooling......Page 453
13.5.3.2 Effect of Cooling Rate on Substructure......Page 457
13.5.3.3 Interface Stability......Page 459
13.5.3.5 Controlling Substructure......Page 465
13.6 Fusion Zone Hot Cracking......Page 470
13.6.1 Mechanism of Hot Cracking......Page 471
13.6.2.1 Control of Weld Metal Composition......Page 474
13.6.2.3 Use of Favorable Welding Conditions......Page 475
13.7 Summary......Page 476
References and Suggested Reading......Page 477
14 EUTECTIC, PERITECTIC, AND POSTSOLIDIFICATION FUSION ZONE TRANSFORMATIONS......Page 481
14.1.1 Solidification at the Eutectic Composition......Page 482
14.1.2 Solidification of Two-Phase Alloys at Noneutectic Compositions......Page 487
14.2 Peritectic Reactions......Page 489
14.2.1.1 Alloys Below the Solubility Limit of the Solid Phase in the Peritectic......Page 490
14.2.1.2 Alloys Between the Solubility Limit and the Peritectic Composition......Page 493
14.2.1.3. Alloys Wlth the Perltectlc Composltlon.......Page 494
14.2.1.4 Alloys Beyond the Peritectic Composition, but Within the L + S Range.......Page 495
14.2.2 Nonequilibrium Conditions......Page 496
14.2.2.1 No Diffusion in the Solid/Complete Mixing in the Liquid (Case 2)......Page 497
14.3 Transformations in Ferrite + Austenite or Duplex Stainless Steels......Page 499
14.4 Kinetics of Solid-state Phase Transformations: Nonequilibrium Versus Equilibrium......Page 508
14.5 Austenite Decomposition Transformations......Page 516
14.5.1 Equilibrium Decomposition to Ferrite + Pearlite (The Eutectiod Reaction)......Page 518
14.5.2 Nonequilibrium Decomposition to Other Ferrite Morphologies (Very Slow to Moderately Slow Cooling Rates)......Page 520
14.5.3 Nonequilibrium Transformation to Bainite (Faster Cooling Rates)......Page 521
14.5.4 Nonequilibrium Transformation to Martensite (Very Fast Cooling Rates)......Page 522
14.6 Sigma and Chi Phase Formation......Page 525
References and Suggested Reading......Page 526
15.1 Origin and Location of the Partially Melted Zone......Page 528
15.2 Constitutional Liquation......Page 532
15.3.1 Conventional Hot Cracking and Liquation Cracking in the PMZ......Page 535
15.3.2 Loss of Ductility in the PMZ......Page 536
15.3.3 Hydrogen-Induced Cracking in the PMZ......Page 537
15.4 Remediation of Defects in the PMZ......Page 538
15.5 Summary......Page 539
References and Suggested Reading......Page 540
16.1 Heat-Affected Zones in Welds......Page 541
16.2.1 The Physical Metallurgy of Cold Work/Recovery/Recrystallization/Grain Growth......Page 542
16.2.2 Cold-Worked Metals and Alloys in Engineering......Page 547
16.2.3 Avoiding or Recovering Property Losses in Work-Hardened Metals or Alloys......Page 550
16.2.4 Development of a Worked Zone in Pressure-Welded Materials......Page 552
16.3.1 The Physical Metallurgy of Solid-Solution Strengthening or Alloying......Page 553
16.4.1 The Physical Metallurgy of Precipitation- or Age-Hardenable Alloys......Page 556
16.4.3 Avoiding or Recovering Property Losses in Age-Hardenable Alloys......Page 563
16.5.1 The Physical Metallurgy of Transformation-Hardenable Alloys......Page 570
16.5.3.1 Behavior of Carbon Steels......Page 572
16.5.3.2 Behavior of Alloy Steels......Page 574
16.6.1 The Physical Metallurgy of Stainless Steels......Page 577
16.6.3 Sensitization of Austenitic Stainless Steels by Welding......Page 580
16.6.4 Welding of Ferritic and Martensitic Stainless Steels......Page 588
16.7 The HAZ in Dispersion-Strengthened or Reinforced Alloys......Page 591
16.8.1 Liquation Cracking......Page 593
16.8.2 Reheat or Strain-Age Cracking......Page 594
16.8.3 Quench Cracking and Hydrogen Cold Cracking......Page 597
16.8.4 Weld Decay, Knife-Line Attack, and Stress Corrosion Cracking......Page 598
16.8.5 Lamellar Tearing......Page 600
References and Suggested Reading......Page 601
17 WELDABILITY AND WELD TESTING......Page 604
17.1 Weldability Testing......Page 605
17.2 Direct Weldability or Actual Welding Tests......Page 606
17.2.1 Fusion and Partially Melted Zone Hot-Cracking Tests......Page 607
17.2.1.2 Houldcroft and Battelle Hot-Crack Susceptibility Tests......Page 609
17.2.1.4 Variable-Restraint (or Varestraint) Test......Page 610
17.2.1.6 Root-Pass Crack Test......Page 611
17.2.1.7 Keyhole-Slotted-Plate Test......Page 612
17.2.1.9 Circular-Groove Cracking and Segmented-Groove Tests......Page 613
17.1.1.12 Sigmajig Test......Page 615
17.2.2 Heat-Affected Zone General Cold-Cracking Weldability Tests......Page 616
17.2.3 Hydrogen Cracking Testing......Page 619
17.2.3.1 Implant Test......Page 622
17.2.3.3 Controlled-Thermal-Severity (CTS) Test......Page 623
17.2.3.7 Gapped-Bead-on-Plate or G-BOP Test......Page 625
17.2.4.2 Vinckier Test......Page 628
17.2.5.1 Lehigh Cantilever Lamellar Tearing Test......Page 630
17.2.5.2 Tensile Lamellar Tearing Test......Page 631
17.4 Weld Pool Shape Tests......Page 633
17.5 Weld Testing......Page 634
17.5.2 All-Weld-Metal Tensile Tests......Page 636
17.5.5 Other Mechanical Tests......Page 637
17.5.6.1 General Corrosion and Its Testing......Page 642
17.5.6.4 Intergranular Corrosion and Its Testing......Page 644
17.6 Summary......Page 648
17.5.1 Transverse- and Longitudinal-Weld Tensile Tests......Page 635
References and Suggested Reading......Page 649
CLOSING THOUGHTS......Page 652
APPENDICES......Page 654
INDEX......Page 666