Welding: Definition and History Quiz

Welding is a fabrication process that unites materials, primarily metals, through heat application, leading to coalescence with or without pressure.
The iron pillar in Delhi, India, erected around 310 AD, exemplifies early welding use, weighing 5.4 metric tons.
Late 19th century saw the introduction of arc welding, oxyfuel welding, and resistance welding, replacing the earlier forge welding technique.
The World Wars I and II significantly accelerated the development and use of various welding processes for military applications.

Fusion Welding: Involves melting materials to form joints; examples include gas and arc welding.
Pressure Welding: Materials are heated to a plastic state and joined under pressure; resistance welding is a common method.
Homogeneous Welding: Joins similar materials; ideal for consistent welding characteristics.
Heterogeneous Welding: Joins dissimilar materials, requiring specialized techniques to ensure quality.

Fusion Welding:
- Gas Welding: Utilizes a flame from burning gases (e.g., oxyacetylene) for melting materials.
- Arc Welding: Uses an electric arc for heat generation; includes various methods like SMAW, GMAW, GTAW, PAW, and SAW.
Resistance Welding:
- Butt Welding: Joins materials under pressure and current.
- Spot Welding: Creates welds at specific locations.
- Seam Welding: Involves continuous spot welds along seams.
- Projection Welding: Uses projections to focus heat and pressure.
- Percussion Welding: Employs high-energy discharge for melting.
Other Welding Processes:
- Thermit Welding: Relies on a chemical reaction for heat.
- Solid State Welding: Joins materials below melting points, including friction, ultrasonic, diffusion, and explosive welding.
- Newer Processes: Electron Beam Welding (EBW) and Laser Beam Welding (LBW) use focused energy beams for precise welding.

Equipment Needed: Welding generator or transformer, cables, electrode holder, electrodes, protective gear (gloves, goggles), and tools for cleaning.
Advantages:
- Highly efficient with low costs and material waste.
- Versatile, capable of joining all commercial metals.
- Allows for design flexibility in applications.
Limitations:
- Labor-intensive, leading to higher costs.
- Requires high energy, posing safety risks.
- Difficulties in detecting joint defects and inconvenient for disassembly.

Alternating Current (AC):
- More efficient and cost-effective.
- Lower equipment costs but capable of higher voltages, making it less safe.
- Not ideal for non-ferrous metals or thin sections.
Direct Current (DC):
- Less efficient and costlier in terms of power consumption.
- Offers a safer, lower voltage operation, suitable for both ferrous and non-ferrous metals, particularly in thin sections.

Shielded Metal Arc Welding (SMAW): Electric arc generated between a coated electrode and the base metal, with the coating providing gas and filler metal.
Metal Inert Gas (MIG) Welding: Uses a consumable filler wire and inert gas, typically Argon, for shielding.
Tungsten Inert Gas (TIG) Welding: Utilizes a tungsten electrode to produce a plasma between it and the base metal, allowing for additional filler material.
Submerged Arc Welding (SAW): Creates a coalescence through an arc shielded by a flux blanket, minimizing sparks and smoke.
Plasma Arc Cutting (PAC): Melts a small area of metal with a constricted arc, efficiently removing molten material.