Selection of welding process

A wide range of welding processes are available to choose. These were developed over a long period of time. Each process differs in respect of their ability to apply heat for fusion, protection of the weld pool and soundmen of welds joint the so performance of the weld joint. However, selection of a particular process for producing a weld joint is dictated by the size and shape of the component to be manufactured, the metal system to be welded, availability of consumables and machines, precision required and economy. Whatever process is selected for developing weld joint it must be able to perform the intended function for designed life. Welding processes with their field of applications are given below:
  1.  Resistance welding: Automobile
  2. Thermite welding: Rail joints in railways
  3. Tungsten inert gas welding: Aerospace and nuclear
  4. Submerged arc welding: Heavy engineering, ship building
  5. Gas metal arc welding: Joining of metals (stainless
    steel, aluminium and magnesium) sensitive to atmospheric gases

    Applications of welding

    General applications

    The welding is widely used for fabrication of pressure vessels, bridges, building structures, aircraft and space crafts, railway coaches and general applications besides shipbuilding, automobile, electrical, electronic and defense industries, laying of pipe lines and railway tracks and nuclear installations.

    Specific components need welding for fabrication includes
    1. Transport tankers for transporting oil, water, milk etc.
    2. Welding of tubes and pipes, chains, LPG cylinders and other items.
    3. Fabrication of Steel furniture, gates, doors and door frames, and body
    4. Manufacturing white goods such as refrigerators, washing machines,
    5.microwave ovens and many other items of general applications

    The requirement of the welding for specific area of the industry is given in following section.

    Oil AndGas
    1. Welding is used for joining of pipes, during laying of crude oil and gas pipelines, construction of tankers for their storage and transportation. Offshore structures, dockyards, loading and unloading cranes are also produced by welding.

    Nuclear Industry
    2. Spheres for nuclear reactor, pipe line bends, joining of pipes carrying heavy water require welding for safe and reliable operations.

    Defense industry
    3. Tank body fabrication, joining of turret mounting to main body of tanks are typical examples of applications of welding in defense industry.

    Electronic industry
    4. Electronic industry uses welding to limited extent e.g. joining leads of special transistors but other joining processes such as brazing and soldering are widely used.
    5. Soldering is used for joining electronic components to printed circuit boards (PCBs).
    6. Robotic soldering is very common for joining of parts to printed circuit boards of computers, television, communication equipment and other control equipment etc.

    Electrical Industry
    7. Components of both hydro and steam power generation system, such as penstocks, water control gates, condensers, electrical transmission towers and distribution system equipment are fabricated by welding. Turbine blades and cooling fins are also joined by welding.

    Surface transport
    8. Railway: Railway uses welding extensively for fabrication of coaches and wagons, repair of wheel, laying of new railway tracks by mobile flash butt welding machines and repair of cracked/damaged tracks by thermite welding.
    9. Automobiles: Production of automobile components like chassis, body and its structure, fuel tanks and joining of door hinges require welding.

    Aerospace Industry
    10. Aircraft and Spacecraft: Similar to ships, aircrafts were produced by riveting in early days but with the introduction of jet engines welding is widely used for aircraft structure and for joining of skin sheet to body.
    11. Space vehicles which have to encounter frictional heat as well as low emperatures require outer skin and other parts of special materials. These materials are welded with full success for achieving safety and reliability

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