Welding Technology and Processes

Study Notes

Evolution of Welding

Welding processes have evolved over time.
Classification of welding processes exists.
Heat sources and shielding methods are utilized.

Physics of Welding Arc

Welding arcs exhibit voltage distribution along the arc.
Cathodes can be thermionic or non-thermionic.
Theories explain cathode and anode mechanisms.
Arc characteristics relate to power sources.
Arc efficiency, heat generation, and shielding gas effects are factors.
Isotherms of arcs are studied.

Welding Power Sources

Conventional welding power sources have static and dynamic characteristics.
Duty cycle is a key parameter.
Inductance affects arc and power source characteristics.
Internal and external regulation exists.
Specific power source requirements vary.
Special welding power sources are available.

Arc Welding Processes

Consumable electrode welding processes are a focus.
Manual metal arc (MMA) welding is described.
Gas metal arc welding and pulsed MIG welding are explained.
Submerged arc welding is also discussed, highlighting the importance of flux-metal combinations.
Electroslag welding, characterized by its heat generation principle, is covered.
Gas tungsten arc welding, discussing polarity selection, is included.
Plasma arc welding and its transferred/non-transferred versions are presented, along with gas selection and parameter discussion.
The keyhole technique is mentioned.

Heat Flow in Welding

Welding parameters affect heat distribution.
Peak temperatures and thermal cycles are calculated.
Cooling rates and solidification are examined.
Residual stresses, their distribution, and influence on static and dynamic loading are discussed.
Weld distortion is addressed.

Design of Weld Joints

Design principles are introduced, including the engineering properties of steels.
Types of welds and weld joints are described.
Terminology, definitions, and weld symbols are explained.
Edge preparation and weld sizing in structures are covered.
Design considerations for static and fatigue loading are detailed.
Fatigue, its nature, strength, factors affecting fatigue life, and improvement methods are discussed.
Reliability analysis and safety factors are applied to fatigue design.

Testing and Inspection of Weld Joints

Chemical, metallographic, and hardness tests are described.
Mechanical tests for groove and fillet welds (full section, reduced section, all-weld-metal tensile, root, face, side bend, and fillet weld break tests) are covered.
Creep and fatigue testing are addressed.
Non-destructive testing (NDT) methods, including visual, dye penetrant, magnetic particle, ultrasonic, radiographic, and eddy current inspections, are presented.
Principle of each NDT method is explained.
Leak tests, NDT standards, WPS, and PQR procedures are noted.

Weldability of Metals

Solidification of weld metal and the heat affected zone (HAZ) are discussed.
Factors affecting HAZ properties are outlined.
Gas-metal, slag-metal, and solid-state reactions in welding and their weld soundness effects are explored.
Issues like lamellar tearing and hydrogen damage are addressed.
Weldability definitions, the factors affecting steel weldability, and carbon equivalent are detailed.
Weldability of important steel, cast iron, and aluminum alloys is covered.
Failure analysis of welded joints is also included.

Description

Explore the evolution of welding processes, including the physics behind welding arcs and the characteristics of various power sources used in welding. This quiz covers different welding methodologies, such as manual metal arc and gas metal arc welding, as well as their efficiency and heat generation aspects.