Cracking Phenomena in Welds IV (eBook)

Preface 5
Photograph of Participants 7
Contents 8
Hot Cracking Phenomena I---Testing 11
1 A Historical Perspective on Varestraint Testing and the Importance of Testing Parameters 12
Abstract 12
The Origin of the Varestraint Test 12
The Optimum in a Weld Cracking Test 12
The ``Elegant Version'' of the Varestraint Concept 13
Cracking Criteria at Varestraint Testing 14
A Newly Built Varestraint Testing Device 17
Methodology 18
Measurement System Analysis 18
Design of Experiment 18
Results and Discussion 19
Measurement System Analysis---Stereo Microscopy Versus Fluorescence Penetrant Inspection 19
Effect of Surface Appearance on the Variation 20
Natural Variation in Equipment and Material 21
Design of Experiment 24
Conclusions 30
Acknowledgements 31
References 31
2 Improved Understanding of Varestraint Testing---Nickel-Based Superalloys 33
Abstract 33
Varestraint Testing 34
Varestraint Testing of Precipitation Hardening Nickel-Based Superalloys 36
Experimental 36
Varestraint Testing 36
Material 37
Metallographic Procedures 37
Results and Discussion 38
Strain Measurement 38
Varestraint Testing of ATI 718Plus and Haynes 282 40
Conclusions 44
Acknowledgements 44
References 44
3 Towards Establishment of Weldability Testing Standards for Solidification Cracking 45
Abstract 45
Introduction 46
Alloy Composition 47
Aluminum Alloys 48
Stainless Steel Alloys 49
Test Selection 50
Test Type 50
Intrinsic Versus Extrinsic 50
Bend Versus Tensile 53
Castability Versus Weldability 54
How Test Parameters Affect Results 55
Effect of Loading Direction 55
Effect of Stress 55
Effect of Strain and Strain Rate 56
Effect of Restraint 57
Effect of Welding Parameters 59
Measurements that Uniquely Define Weldability 61
Brittle Temperature Range 62
Critical Strain Rate 62
Summary 66
References 70
4 Use of Computational and Experimental Techniques to Predict Susceptibility to Weld Cracking 75
Abstract 75
Introduction 76
High-Cr, Ni-Base Filler Metal Development 76
Background 76
Experimental 81
Results and Discussion 84
Summary and Conclusions 86
Carbon Diffusion Model for DMW During PWHT 86
Background 86
Experimental 87
Results and Discussion 88
Summary and Conclusions 90
References 91
Hot Cracking Phenomena II---Design Considerations 93
5 Considerations for Sound Parameter Studies in Electron Beam Welding of Thick Walled Components 94
Abstract 94
Introduction 94
Cold Cracks 95
Hot Cracks 96
Inconsistent Welding Defects 97
Experiment to Induce Cracks 100
Results and Discussion 102
Conclusion 104
References 105
6 Consideration of Welding-Specific Component Design on Solidification Crack Initiation 107
Introduction 108
Test Equipment and Procedure 112
Results and Discussion 114
Conclusions 121
References 122
7 Prediction of Ductility-Dip Cracking in Narrow Groove Welds Using Computer Simulation of Strain Accumulation 124
Abstract 124
Ductility-Dip Cracking: Established Theory Overview 124
Test Mockup Designed to Evaluate DDC Mechanism 126
Confirmation of Strain Ratcheting Effect on DDC 130
Comparison of First and Second Narrow Groove Test 134
Benchmarking of SysWeld2122 Simulation 135
Crack Analysis of Second Narrow Groove DDC Test and Comparison with Benchmarked SysWeld2122 Simulation 140
Conclusions 144
Acknowledgements 145
References 145
Hot Cracking Phenomena---Materials 147
8 Ductility-Dip Cracking Susceptibility of Commercially Pure Ni and Ni-Base Alloys Utilizing the Strain-to-Fracture Test 148
Abstract 148
Introduction 148
Experimental Approach 151
Materials 151
Sample Preparation 151
STF Testing 153
Metallurgical Analysis 153
Results and Discussion 154
STF Test Results 154
Alloy 200 154
Alloy 600 155
Alloy 625 155
Effects of Oxygen Additions 155
Microstructure Characterization 156
Alloy 200 156
Alloy 600 157
Alloy 625 158
Fracture Morphologies 158
Improving DDC Response 160
Conclusions 161
Acknowledgements 161
References 161
9 Evaluation of Solidification Cracking Susceptibility in Austenitic Stainless Steel Welds Using Laser Beam Welding Transverse-Varestraint Test 163
Abstract 163
Introduction 164
Materials and Experimental Procedures 165
Materials 165
Transverse-Varestraint Test Procedure with LBW (LBW Transverse-Varestraint Test) 166
Transverse-Varestraint Test Procedure with GTAW 168
Microstructural Analysis 168
Solidification Cracking Behaviour in LBW Transverse-Varestraint Test 168
Appearance and Characterisation of Hot Cracks 168
Solidification Cracking Behaviour 170
Influence of Solidification Microstructure on Solidification Cracking Morphology 172
Establishment of LBW Transverse-Varestraint Testing Methodology 177
Features in Test Procedures 177
Timing-Synchronisation with High-Speed Camera Observation 177
Compensation of Yoke-Drop Time by High-Speed Camera Observation 177
Determination of High-Temperature Ductility Curve for Solidification Cracking 179
Conversion of Solidification Cracking Temperature Range from Crack Length 179
Compensation of Augmented Strain 182
High-Temperature Ductility Curve for Solidification Cracking in Laser Welds 182
Difference Between LBW and GTAW 182
Change in BTR with Welding Speed 184
Mechanism of BTR Variation in LBW 186
Theoretical Basis of Solidification Initiation Temperature ( T_{L} ) Calculation 186
Theoretical Basis of Solidification Completion Temperature ( T_{C} ) Calculation 189
Conditions of Numerical Calculation 192
Calculation Results 194
Solidification Segregation Behaviour 194
Effect of Welding Speed on Solid/Liquid Coexistence Temperature Range 198
Variation Mechanism of Solidification Cracking Susceptibility in LBW 201
Conclusions 204
References 205
10 Comparative Evaluation of Mesoscale Sensitivity to Crack Formation in Multi-pass Welds Using Wires IN52 and IN52MSS 209
Abstract 209
Introduction 209
Materials and Experimental Procedures 210
Results and Discussion 212
Conclusions 218
References 219
11 Welding Optimization of Dissimilar Copper-Aluminum Thin Sheets with High Brightness Lasers 221
Abstract 221
Introduction 221
Experimental Procedure 222
Results and Discussion 224
Conclusions 229
Acknowledgements 229
References 230
12 Elevated Temperature, Solid-State Cracking in Welds 231
Abstract 231
Introduction 231
Ductility Dip Cracking 232
Proposed Mechanisms 234
Quantifying Ductility Dip Cracking 238
Preventing Ductility Dip Cracking 240
Reheat and Stress-Relief Cracking 241
Low Alloy Steels 242
Stainless Steels 244
Relaxation Cracking 246
Quantifying Reheat Cracking Susceptibility 247
Preventing Reheat Cracking 247
Strain-Age Cracking 251
Mechanism for Strain-Age Cracking 253
Quantifying Susceptibility to Strain-Age Cracking 259
Preventing Strain-Age Cracking 262
Summary 263
Acknowledgements 264
References 264
Hot Cracking Susceptibility of Ni-Base Alloys 268
13 Weldability Evaluation of High Chromium, Ni-Base Filler Metals Using the Cast Pin Tear Test 269
Abstract 269
Introduction 269
Motivation 269
Background 271
Materials and Procedures 273
Materials 273
Procedure 274
Results and Discussion 277
Reproducibility Study 277
Tested Alloys 278
Dilution Study 278
Characterization 282
Conclusions 286
Acknowledgements 286
References 287
14 Multi-scale Modeling of the Stress-Strain State During Welding of Ni-Based Alloys 289
Abstract 289
Introduction 289
Experimental Procedures 290
Modeling at the Macrolevel 293
Modeling at Mesoscale 297
Conclusions 302
References 302
15 Weldability of Cast and Wrought Nickel Base Alloys 59, 617 and 625 304
Abstract 304
Introduction 305
Experimental Procedure 306
Materials 306
PVR Testing 308
Hot Ductility Testing 310
Metallurgical Characterization 311
Results 311
PVR Tests 311
Hot Ductility Tests 312
Discussion 319
Conclusions 323
Acknowledgements 323
References 323
Cold Cracking Phenomena 325
16 Numerical Investigations on Hydrogen-Assisted Cracking in Duplex Stainless Steel Microstructures 326
Abstract 326
Introduction 327
Numerical Procedure for Simulating Hydrogen-Assisted Cracking 329
Material Used---Chemical Composition and Mechanical Properties 329
Numerical Simulation of HAC 330
Numerical Mesoscale Model of the DSS Microstructure 331
Numerical Simulation of Hydrogen Diffusion 332
Numerical Simulation of Phase Specific Stresses and Strains 333
Numerical Simulation of Material Damage 336
Results and Discussion 338
Phase Specific Hydrogen Diffusion and Hydrogen Distribution 338
Phase Specific Hydrogen Effusion 341
Phase Specific Stress--Strain Analysis 343
Numerical Simulation of Material Damage 346
Conclusions 351
References 353
17 Hydrogen Assisted Cracking of a Subsea-Flowline 357
Abstract 357
Introduction 358
Failure Sequence and Initial Situation 359
Sequence of Events 359
Preliminary Investigations 360
Investigations 362
Original Fracture Surfaces 362
Simulation Experiments 365
Comparison of Fracture Topographies 371
Conclusions 373
References 374
Stress Corrosion and Cold Cracking Phenomena 376
18 Numerical Modelling of Hydrogen Assisted Cracking in Steel Welds 377
Abstract 377
Introduction 378
Hydrogen Assisted Cracking (HAC)---Types and Mechanisms 379
Mechanisms 381
Pressure Theory 381
Adsorption Theory 381
Inner and Outer Hydride Formation 382
Hydrogen Enhanced Decohesion Theory (HEDE) 382
Plasticity Theory 383
Adsorption Induced Dislocation Emission Theory (AIDE) 385
Numerical Simulation of HAC 387
Modelling Approach and Application to Welded Components 390
Numerical Model 390
HASCC in a SSRT Specimen of Supermartensitic Stainless Steel 392
HASCC in a Welded Supermartensitic Stainless Steel 395
HACC in a Welded Supermartensitic Stainless Steel 401
HACC in S 1100 QL High Strength Structural Steel Welds 408
Simulation of HAC in Duplex Stainless Steel Microstructures at the Mesoscale 419
Conclusions 425
References 426
19 Metallurgical Factors Influencing the Susceptibility of Hydrogen Assisted Cracking in Dissimilar Metal Welds for Application Under Cathodic Protection 434
Abstract 434
Introduction 435
Statement of Problem 435
Metallurgical and Microstructural Factors of HAC 435
Delayed Hydrogen Cracking Test 436
Experimental Approach 438
Results 439
Initial Modeling Conditions 439
Carbon Diffusion Parameters 440
Effect of PWHT Hold Time 441
Effect of PWHT Hold Temperature 441
Width of Transition Region 443
Effect of Initial Carbon Concentration in IN625 444
Discussion 444
Conclusions 446
Acknowledgements 447
References 447
20 Hydrogen Trapping in Supermartensitic Stainless Steel TIG Welds 449
Abstract 449
Introduction 449
Various Trap--Hydrogen Interactions 451
Experimental Approach 451
Results and Discussion 453
Hydrogen Absorption 453
Hydrogen's Effects on Microstructure 455
Desorption Characteristics 457
Conclusions 462
References 463
Elevated Temperature Solid-State Cracking 465
21 Stress-Relief Cracking in Simulated-Coarse-Grained Heat Affected Zone of a Creep-Resistant Steel 466
Abstract 466
Introduction 467
Materials and Experimental Procedures 469
Materials 469
OSU Stress-Relief Cracking Test 470
Sample Preparation 471
Reduction in Area 473
Results and Discussion 473
SRC Test at 600 ?C 473
SRC Test at 650 ?C 475
SRC Test at 700 ?C 478
SRC Test at 750 ?C 478
Summary of the SRC Test Results 481
Summary and Conclusions 482
Acknowledgments 483
References 483
22 Testing Approaches for Stress Relaxation Cracking in Gamma-Prime Strengthened Ni-Base Alloys 485
Abstract 485
Introduction 485
Procedures 491
Results 495
Conclusions 499
Acknowledgements 500
References 500