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