Fundamentals of Metal Joining: Processes, Mechanism and Performance

Preface
About This book
Contents
About the Author
Part I Basics of Metal Joining
1 Metal Joining: Need, Approaches and Mechanisms
1.1 Basics and Need of Joining
1.1.1 Fundamental Approaches of Metal Joining and Joint Capability
1.1.2 Relevance of Heat and Pressure in Metal Joining
1.1.3 Sources of Heat for Metal Joining
1.1.4 Heat and Characteristics of Metallic Joint
1.2 Mechanisms of Joining
1.2.1 Fusion
1.2.2 Plastic Deformation
1.2.3 Chemical Reactions
1.2.4 Metallurgical Reactions
1.3 Choice of the Method of Joining
1.3.1 Type of Joint
1.3.2 Type of Metallic Combination
1.3.3 Workpiece Metal
1.3.4 Service Environment
1.3.5 Reliability
1.3.6 Nature of Loading
1.3.7 Type of Stress
1.3.8 Economy of Joining
1.4 Manufacturing Processes and Welding
1.5 Welding and Its Uniqueness
1.5.1 Selection of Welding as a Route for Manufacturing
1.6 Advantages and Limitations of Welding
1.7 Applications of Welding
Further Reading
2 Classification of Joining Processes
2.1 Classification Based on Approach of Joining Processes
2.1.1 Fusion Weld Processes
2.1.2 Cast Weld Processes
2.1.3 Resistance Weld Processes
2.1.4 Solid State Welding Process
2.2 Classification Based on Technological Factors of Welding Processes
2.2.1 Welding With/Without Filler Material
2.2.2 Source of Energy for Welding
2.2.3 Arc and Non-arc Welding
2.2.4 Pressure and Fusion Welding
Further Reading
3 Heat Generation and Protection of Weld
3.1 Need of Heat in Welding
3.2 Heat Generation
3.2.1 Chemical Reactions
3.2.2 Electric Arc
3.2.3 Resistance Heating
3.2.4 Friction and Deformation Heat
3.3 Effect of Heat Generation and Weld Joint Characteristics
3.4 Protection of Weld Pool
3.4.1 Forming Envelop/shroud of Inactive or Inert Gas
3.4.2 Covering the Weld Pool Using Molten Flux
3.5 Cleanliness of Weld Metals and Welding Processes (Approaches for Protection of the Weld Pool)
3.5.1 Shielded Metal Arc Welding
3.5.2 Submerged Arc Welding
3.5.3 Gas Tungsten Arc Welding
3.5.4 Gas Metal Arc Welding
3.5.5 Electro-Slag and Electro-Gas Welding
Further Reading
4 Power Density and Peak Temperature of Welding Processes
4.1 Introduction
4.2 Effect of Power Density
4.3 Need of Optimum Power Density of Welding Process
Further Reading
Part II Physics of Welding Arc
5 Physics of Welding Arc
5.1 Introduction
5.2 Emission of Free Electrons
5.2.1 Thermo-Ionic Emission
5.2.2 Field Emission
5.2.3 Secondary Emission
5.3 Zones in Arc Gap
5.3.1 Cathode Spot
5.3.2 Cathode Drop Region
5.3.3 Plasma Zone
5.3.4 Anode Drop Region
5.3.5 Anode Spot
5.4 Electrical Fundamentals of Welding Arc
Further Reading
6 Physics of Welding Arc
6.1 Arc Initiation
6.1.1 Touch Start
6.1.2 Field Start
6.2 Maintenance of Arc
6.2.1 Low Ionization Potential Elements
6.2.2 Low Power Factor
6.3 Welding Arc Characteristic
6.4 Temperature of the Arc
Further Reading
7 Physics of Welding Arc
7.1 Arc Forces and Their Significance on Welding
7.1.1 Gravity Force
7.1.2 Surface Tension Force
7.1.3 Force Due to Impact of Charge Carriers
7.1.4 Force Due to Metal Vapours
7.1.5 Force Due to Gas Eruption
7.1.6 Force Due to Electro Magnetic Field
7.2 Effect of Electrode Polarity
7.2.1 Heat Generation
7.2.2 Arc Initiation and Stability
7.2.3 Cleaning Action
7.3 Arc Blow
7.3.1 Causes of Arc Blow
7.3.2 Mechanism of Arc Blow
7.3.3 Controlling the Arc Blow
Further Reading
8 Physics of Welding Arc
8.1 Arc Efficiency
8.1.1 Arc Efficiency of Different Welding Processes
8.1.2 Calculations of Arc Efficiency
8.2 Metal Transfer
8.2.1 Short Circuit Transfer and Dip Transfer
8.2.2 Globular Transfer
8.2.3 Spray Transfer
8.2.4 Rotational Transfer
8.3 Melting Rate
8.3.1 Factors Limiting the Melting Rate
Further Reading
Part III Arc Welding Power Source
9 Arc Welding Power Source
9.1 Introduction
9.2 Characteristics of Power Source
9.2.1 Open Circuit Voltage (OCV)
9.2.2 Power Factor (pf)
9.2.3 Static Characteristic of Power Source
Further Reading
10 Arc Welding Power Source
10.1 Rising Characteristics
10.2 Dynamic Characteristic
10.3 Duty Cycle
10.4 Class of Insulation
10.5 High Frequency Unit
10.6 Feed Drives for Constant Arc Length
Further Reading
Part IV Arc Welding Processes
11 Arc Welding Processes: Shielded Metal Arc Welding—Principle, Electrode and Parameters
11.1 Arc Welding Process
11.2 Shielded Metal Arc Welding (SMAW)
11.3 Shielding in SMA Welding
11.4 Coating on SMAW Electrode
11.5 Types of SMAW Electrodes
11.5.1 Rutile Electrode
11.5.2 Cellulosic Electrodes
11.5.3 Acidic Electrode
11.5.4 Basic Electrode
11.5.5 Basic Rutile Electrode
11.6 Welding Parameters for SMAW
Further Reading
12 Arc Welding Processes: Shielded Metal Arc Welding: Welding Current and Metal Transfer
12.1 Selection of Type of Welding Current
12.2 Electrode Size and Coating Factor
12.3 Weld Beads
12.4 Metal Transfer in SMAW
Further Reading
13 Arc Welding Processes: Submerged Arc Welding: Principle, Parameters and Applications
13.1 Introduction
13.2 Components of SAW System
13.2.1 Power Source
13.2.2 Welding Electrode
13.2.3 SAW Flux
13.3 Composition of the SAW Fluxes
13.4 Fluxes for SAW and Recycling of Slag
13.5 Welding Parameters
13.5.1 Welding Current
13.5.2 Welding Voltage
13.5.3 Welding Speed
13.6 Bead Geometry and Effect of Welding Parameters
13.7 Advantage
13.8 Limitations
13.9 Applications
Further Reading
14 Arc Welding Processes: Gas Tungsten Arc Welding: Principle and System Components
14.1 Introduction
14.2 TIG Welding System
14.2.1 Power Source
14.2.2 Welding Torch
14.2.3 Filler Wire
14.2.4 Shielding Gas
14.3 Effect of Shielding Gases on GTAW Characteristics
14.3.1 Heat of Welding Arc
14.3.2 Arc Efficiency
14.3.3 Arc Stability
14.3.4 Flow Rate of Shielding Gas
14.3.5 Mixture of Shielding Gases
14.3.6 Advantages of Ar Over He as Shielding Gas
Further Reading
15 Arc Welding Processes: Gas Tungsten Arc Welding: Electrode, Polarity and Pulse Variant
15.1 Electrode for TIG Torch
15.2 Welding Torch
15.2.1 Type of Welding Current and Polarity
15.2.2 Electrode Diameter and Welding Current
15.3 TIG Arc Initiation
15.3.1 Carbon Block Method
15.3.2 Field Start Method Using High-Frequency Unit
15.3.3 Pilot Arc Method
15.4 Maintenance of TIG Welding Arc
15.5 Pulse GTA Welding
15.5.1 Process Parameters of Pulse TIG Welding
Further Reading
16 Arc Welding Processes: Gas Tungsten Arc Welding: Pulse Current, Hot Wire and Activated Flux-Assisted GTAW: Plasma Arc Welding: Principle, System, Application
16.1 Selection of Pulse Parameters for Pulse GTAW
16.1.1 Pulse Current
16.1.2 Pulse Frequency
16.2 Hot Wire Gas Tungsten Arc Welding
16.3 Activated Flux-Assisted Welding Processes
16.4 Introduction
16.5 Principle of PAW
16.6 Types of PAW
16.7 Advantage of PAW
16.8 Limitation of PAW
Further Reading
17 Arc Welding Processes: Gas Metal Arc Welding: Principle, System, Parameters and Application
17.1 Fundamentals of GMA Welding
17.2 Power Source for GMA Welding
17.3 Shielding Gases for GMA Welding
17.4 Effect of MIG Welding Process Parameters
17.5 Metal Transfer in GMA Welding
17.6 Pulse GMAW Welding
17.7 Flux-Cored Arc Welding Process
Further Reading
Part V Solid Liquid Joining and Solid State Joining Processes
18 Brazing, Soldering and Friction Stir Welding
18.1 Fundamentals of Brazing and Soldering
18.2 Joints for Brazing and Soldering
18.3 Comparison of Brazing and Soldering
18.3.1 Melting Point of Filler
18.3.2 Strength of Joint
18.3.3 Ability to Withstand Under High Temperature Conditions
18.4 Application
18.5 Source of Heat for Joining
18.6 Limitation of Brazing and Soldering
18.7 Role of Flux in Brazing
18.8 Braze Welding
18.9 Friction Stir Welding
Further Reading
Part VI Heat Flow in Welding
19 Heat Flow and Performance of Weld Joints
19.1 Importance
19.2 Weld Thermal Cycle
19.2.1 Factors Affecting Welding Thermal Cycle
19.3 Cooling Rate
19.4 Calculations of Cooling Rate
19.5 Critical Cooling Rate (CCR) Under Welding Conditions
19.6 Peak Temperature and Heat Affected Zone
19.7 Solidification Rate
19.8 Residual Stresses
19.9 Residual Stresses in Welding
19.10 Mechanisms of Residual Stress Development
19.10.1 Differential Heating and Cooling
19.10.2 Differential Cooling Rate in Different Zone
19.10.3 Metallurgical Transformation
19.11 Effect of Residual Stresses
19.12 Controlling the Residual Stresses
19.12.1 Thermal Methods
19.12.2 Mechanical Methods
Further Reading
Part VII Welding Metallurgy
20 Welding Metallurgy
20.1 Introduction
20.2 Metallurgy and Metal Joining Processes
20.2.1 Adhesive Joining
20.2.2 Brazing and Soldering
20.2.3 Fusion and Solid State Joining Processes
20.3 Metallurgy and Properties of Joints by Fusion and Solid State Joining
20.4 Metal Strengthening Mechanism and Joint Properties
20.4.1 Fusion Welding
20.4.2 Solid State Joining
20.4.3 Brazing and Soldering
Further Reading
21 Welding Metallurgy
21.1 Solidification of Weld Metal
21.2 Types of Solidification of Weld Metal
21.2.1 Epitaxial Solidification
21.2.2 Modes of Solidification
21.3 Effect of Welding Speed on Grain Structure of the Weld
21.4 Common Methods of Grain Refinement
21.4.1 Inoculation
21.4.2 Arc Pulsation
21.4.3 Mechanical Vibrations and Electromagnetic Force
21.4.4 Magnetic Arc Oscillation
21.4.5 Welding Parameter
21.5 Typical Metallurgical Discontinuity of the Weld
21.5.1 Micro-Segregation
21.5.2 Banding
21.6 Chemical Reaction in Welds
21.6.1 Welding Process and Cleanliness of the Weld
21.6.2 Effect of Atmospheric Gases on Weld Joint
21.6.3 Effect on Weld Compositions
21.6.4 Hydrogen in Weld Metal and Fluxes
21.7 Flux in Welding
21.7.1 Basicity of the Flux
Further Reading
22 Welding Metallurgy: Physical Metallurgy of Welding: Steel, PH Hardenable and Work Hardening Metals
22.1 Relevance of Physical Metallurgy of Steel Welding
22.2 Fe–C Equilibrium Phase Diagram
22.3 Effect of Phases on Mechanical Properties
22.4 Phase Transformation
22.4.1 Time Temperature Transformation (TTT) Diagram
22.4.2 Continuous Cooling Transformation (C.C.T.) Diagram
22.5 Metallurgical Transformation in Fe–C System During Fusion Welding
22.5.1 Fusion Weld Zone (Autogenous Welding/Matching Filler and Electrode)
22.5.2 Fusion Welding Dissimilar Filler/Electrode for Steel and Cast Iron
22.5.3 Weld Zone Developed Using Solid State Joining Processes
22.6 Heat Affected Zone in Weld Joint of Fe–C System
22.6.1 The Partial Meting Zone
22.6.2 Thermo-Mechanically Affected Zone
22.6.3 Heat Affected Zone
22.7 HAZ of Base Metal Strengthened by Work Hardening
22.8 HAZ of Base Metals Strengthened by Precipitation Hardening
22.9 HAZ of Transformation Hardening Metals
22.9.1 Peak Temperature
22.9.2 High-Temperature Retention Period/Soaking Time
22.9.3 Cooling Rate
22.10 HAZ of Solid Solution and Dispersion Strengthened Metals
Further Reading
Part VIII Design of Weld Joints
23 Design of Welded Joints: Weld Failure Modes, Welding Symbols: Type of Welds, Joints, Welding Position
23.1 Introduction
23.2 Modes of Failure of the Weld Joints
23.3 Design of Weld Joints and Mechanical Properties
23.4 Factors Affecting the Performance of the Weld Joints
23.5 Design of Weld Joints and Loading Conditions
23.6 Need of Welding Symbols
23.7 Types of Weld Joints
23.8 Types of Weld
23.9 Welding Position
23.10 Rationale Behind Selection of Weld and Edge Preparation
23.10.1 Single Groove Weld
23.10.2 Double Groove Weld
23.11 Comparative Features of U and J Groove Geometry
Further Reading
24 Design of Welded Joints: Weld Bead Geometry: Selection, Welding Parameters
24.1 Groove Weld
24.2 Fillet Weld
24.3 Bead Weld
24.4 Plug Welds
24.5 Welding and Weld Bead Geometry
24.5.1 Welding Current
24.5.2 Arc Voltage
24.5.3 Welding Speed
Further Reading
25 Design of Welded Joints: Weld Joint Design for Static and Fatigue Loading
25.1 Design Aspects of Weld Joint
25.2 Design of Weld Joint for Static Loading
25.2.1 Design of Fillet Welds
25.2.2 Design of Butt Weld Joint
25.3 Design of Weld Joints for Fatigue Loading
Further Reading
26 Design of Welded Joints
26.1 Fracture Under Fatigue Loading
26.2 Factors Affecting the Stages of Fatigue Fracture
26.2.1 Surface Crack Nucleation Stage
26.2.2 Stable Crack Growth Stage
26.2.3 Sudden Fracture (Unstable Crack Growth)
26.3 Crack Growth and Residual Fatigue Life
26.4 Factors Affecting the Fatigue Performance of Weld Joints
26.4.1 Service Load Conditions
26.4.2 Material Characteristics
26.4.3 Environment
Further Reading
27 Design of Welded Joints
27.1 Welding and Fatigue
27.2 Welding Procedure
27.2.1 Edge Preparation
27.2.2 Welding Process
27.2.3 Welding Consumables
27.2.4 Post-Weld Heat Treatment
27.3 Improving the Fatigue Performance of the Weld Joints
27.3.1 Increasing Load-Carrying Capacity of the Weld Joint
27.3.2 Reducing Stress Raisers
27.3.3 Developing Compressive Residual Stress
Further Reading
Part IX Inspection and Testing of Weld Joints
28 Inspection and Testing of Weld Joint
28.1 Introduction
28.2 Destructive Test
28.2.1 Tensile Test
28.2.2 Bend Test
28.2.3 Hardness Test
28.2.4 Toughness Testing
28.2.5 Fatigue Behaviour of Weld Joint
28.2.6 Fracture Toughness
28.3 Non-destructive Testing (NDT)
28.3.1 Dye Penetrant Test
28.3.2 Magnetic Particle Testing
28.3.3 Ultrasonic Testing
Further Reading
Part X Weldability of Metals
29 Weldability of Metals: Characteristics of Metals and Weldability
29.1 Understanding Weldability
29.2 Weldability of Metals by Fusion Welding Processes
29.2.1 Composition
29.2.2 Affinity of Weld Metal with Atmospheric Gases
29.2.3 Melting Temperature
29.2.4 Solidification Temperature Range
29.2.5 Thermal Conductivity
29.2.6 Thermal Expansion Coefficient
29.2.7 Yield Strength
29.2.8 Toughness and Ductility
29.2.9 Thickness
29.3 Weldability of Metals by Solid State Joining Processes
29.3.1 Composition
29.3.2 Affinity with Atmospheric Gases
29.3.3 Thermal Conductivity and Thermal Expansion Coefficient
29.3.4 Yield Strength and Ductility
29.3.5 Work Hardening
29.4 Weldability of Steels
29.4.1 Weldability of Steel and Composition
29.4.2 Different Types of Steel and Welding
29.5 Common Problems in Steel Welding
29.5.1 Cracking of HAZ Due to Hardening
29.5.2 Cold Cracking
Further Reading
30 Weldability of Metals: Weldability of Aluminium Alloys: Porosity, HAZ Softening and Solidification Cracking
30.1 Need of Aluminium Welding
30.1.1 Strengthening of Non-heat-Treatable Aluminium Alloys and Welding
30.1.2 Strengthening of Heat-Treatable Aluminium Alloys and Welding
30.2 Weldability of Aluminium Alloys
30.3 Typical Welding Problems in Aluminium Alloys
30.3.1 Porosity
30.3.2 Inclusion
30.3.3 Solidification Cracking
Further Reading