Chapter 1 Welding Technology Fundamental 1
1.1 Modern Engineering Structural Material 1
1.2 Mechanical Property of Metal Material 3
1.3 Thermophysical Property of Metal Material 4
1.3.1 Specific Heat 4
1.3.2 Thermal Expansion 5
1.3.3 ThermalConductivity 5
1.3.4 Melting Point or Melting Range 5
1.3.5 Thermionic Work Function 6
1.4 Principal Types of Heat Treatment of Steel 6
1.5 Arc Physics 6
1.5.1 Stabilitv of E1ectric Arc 6
1.5.2 Stability of AC Arc 8
Chapter 2 Arc Welding Power Source 16
2.1 Classification ofPower Source 16
2.1.1 AC Power Supplies 16
2.1.2 DC power supplies 19
2.1.3 Inverse Source of Arc Welding 20
2.2 Electrical Characteristics of Power Source 21
2.2.1 Constant Voltage 21
2.2.2 Constant Current 21
2.2.3 Combined Constant-Current and Constant-Voltage Characteristics 22
2.3 Selecting and Specifying a Power Source 22
Chapter 3 Arc Welding Process 25
3.1 Shielded Metal-Arc Welding 25
3.2 Gas Shielded-Arc Welding 27
3.2.1 Specific Advantages of Gas-shielded Arc 28
3.2.2 Types of Gas-Shielded Arc Processes 28
3.2.3 Gas Tungsten Arc-Tig 28
3.2.4 Gas Metal Arc-Mig 31
3.2.5 CO2 Welding 34
3.2.6 Pulsed Arc Welding 35
3.3 Submerged Arc Welding Fundamentals of the process 36
3.3.1 Deffmition and general description 36
3.3.2 Principles of operation 37
3.4 Plasma Arc Welding 38
3.4.1 Keyhole Action 39
3.4.2 Arc Shaping 39
3.4.3 Operating Data 39
3.4.4 Applications 40
3.4.5 Summary 40
Chapter 4 Other Welding Methods 41
4.1 Resistance Welding 41
4.1.1 Introduction 41
4.1.2 Resistance Spot Welding(RSW) 42
4.1.3 Projection Welding 44
4.1.4 Resistance Seam Welding(RSEW) 45
4.1.5 Upset Butt Welding 46
4.1.6 Fiash Butt Welding 47
4.2 Friction Stir Welding 49
4.2.1 Introduction 49
4.2.2 Principles 50
4.2.3 Friction Stir Tool 51
4.2.4 Friction Stirring Imperfections 55
4.3 Laser Beam Welding 56
4.3.1 Introduction 56
4.3.2 Principles 58
4.3.3 Metals Welded 60
4.3.4 Machines 60
4.3.5 Parameters and Technology 62
4.4 Electron Beam Welding 63
4.4.1 Introduction 63
4.4.2 Principles 64
4.4.3 Variations 66
4.4.4 Equirment 67
4.4.5 Safety 68
Chapter 5 Welding Metallurgy 69
5.1 Chemical Reactions in Welding 69
5.1.1 Overview 69
5.1.2 Gas-Metal Reactions 70
5.1.3 Slag-Metal Reactions 79
5.2 Weld Metal Solidifcation 85
5.2.1 Epitaxial Growth at Fusion Boundary 85
5.2.2 Nonepitaxial Growth at Fusion Boundary 86
5.2.3 Competitive Growth in Bulk Fusion Zone 87
5.2.4 Effect of Welding Parameters on Grain Structure 88
5.2.5 Weld Metal Nuc leation Mechanisms 89
5.2.6 Grain Structure Control 94
5.3 The Microstructure and Properties of Heat-affected Zone 97
5.3.1 Welding Thermal Cycle 98
5.3.2 The Microstructure Changes in the HAZ 98
5.3.3 Hardness Distribution in the HAZ 101
5.3.4 Welding Cracks in the HAZ 105
Chapter 6 Weldability of Material 109
6.1 Weldability of Material and Testing Method 109
6.1.1 Weldability of Material 109
6.1.2 Weldability Evaluation and Test Method 112
6.2 Weldability oflow carbon steel 114
6.2.1 Metallurgy ofthe liquid weld metal 114
6.2.2 Solidification and solidification cracking 119
6.2.3 Stress intensification,embrittlement and cracking of fusion welds below the solidus 121
6.2.4 Lamellar tearing 124
6.2.5 Reheat Cracking 125
6.3 Weldability of Magnesium and Its Alloys 128
6.3.1 Alloys and Welding Procedures 128
6.3.2 Oxide Film Removal 128
6.3.3 Cracking 128
6.3.4 Mechanical Properties 129
6.3.5 Corrosion Resistance and Fire Risk 129
Chapter 7 Residual Stresses,Distortion and Fatigue 130
7.1 Residual stresses 130
7.1.1 Development of residual stresses 130
7.1.2 Analysis ofResidual Stresses 131
7.2 Distortion 133
7.2.1 Cause 133
7.2.2 Remedies 133
7.3 Fatigue 134
7.3.1 Mechanism 134
7.3.2 Fractography 135
7.3.3 S-N Curves 135
7.3.4 Effect of Joint Geometry 135
7.3.5 Effect of Stress Raisers 136
7.3.6 Effect of Corrosion 137
7.3.7 Remedies 137
7.4 Case Studies 138
7.4.1 Failure of a Steel Pipe Assembly 138
7.4.2 Failure of a Ball Mill 138
Chapter 8 Automation of Welding 140
8.1 Introduction of Automatic Welding System 140
8.2 Flexible Automation ofWelding 143
8.3 ARC Welding Robots 145
8.3.1 Introduction 145
8.3.2 Robot Manipulator Configuration 147
8.3.3 Robot Welding Application 151
8.3.4 Buying a Welding Robot 154
8.3.5 Robot Safety 154
8.4 Controls for Automatic Arc Welding 156
8.4.1 Automatic Welding Controllers 156
8.4.2 Robot Controllers 159
8.4.3 Teaching the Robot 159
8.4.4 Robot Memory 161
8.4.5 Weld Execution 161
8.5 Sensors and Adaptive Control 162
8.5.1 Introduction 162
8.5.2 Contact Sensors 164
8.5.3 Noncontaet Sensor Systems 165
8.6 Tooling and Fixtures 168
Chapter 9 Welding Quality Inspection 171
9.1 Welding Defects 171
9.1.1 Definition and Types 171
9.1.2 Cracks 171
9.1.3 Porosity 172
9.1.4 Solid Inclusion 172
9.1.5 Lack ofFusion and Inadequate or incomplete penetration 173
9.1.6 Imperfect Shape 173
9.2 Non-destructive Testing 174
9.2.1 Radiographic Testing 174
9.2.2 Ultrasonic Testing(UT) 177
9.2.3 Magnetic Particle Inspection(MPI) 178
9.2.4 Liquid Penetrant Testing(PT) 179
9.3 Destructive Test 182
9.3.1 Tension Tests 182
9.3.2 Bend Tests 182
9.3.3 Charpy Tests 183
9.3.4 Hardness Testing 183
9.4 Radiograph Interpretation 184
9.4.1 General Welding Discontinuities 184
9.4.2 Other Discontinuities 188
References 190