There are a ton of welding processes, depends on the criticalness of the thing needed to be welded. ARC welding: Name Characteristics Applications Atomic hydrogen welding: Two metal electrodes in hydrogen atmosphere: Historical Bare metal arc welding: Consummable electrode, no flux or shielding gas: Historical Carbon arc welding: Carbon electrode: historical Copper, repair (limited) Electrogas welding: Continuous consumable electrode, vertical positioning, steel only: Storage tanks, shipbuilding Electroslag welding: Continuous consumable electrode, vertical positioning, steel only: Storage tanks, shipbuilding Flux cored arc welding: Continuous consumable electrode filled with flux: Industry, construction Gas metal arc welding: Continuous consumable electrode and shielding gas: Industry Gas tungsten arc welding: Nonconsumable electrode, slow, high quality welds: Aerospace Plasma arc welding: Nonconsumable electrode, constricted arc Tubing instrumentation Shielded metal arc welding: Consumable electrode covered in flux, can weld any metal as long as they have the right electrode: Construction, outdoors Stud arc welding: Welds studs to base material with heat and pressure: Construction, shipbuilding Submerged arc welding: Automatic, arc submerged in granular flux: Ship industry OXY FUEL welding: Air acetylene welding: Chemical welding process :not popular Limited Oxyacetylene welding: Combustion of acetylene with oxygen produces high-temperature flame, :inexpensive equipment Maintenance, repair Oxyhydrogen welding: Combustion of hydrogen with oxygen produces flame :Limited Pressure gas welding: Gas flames heat surfaces and pressure produces the weld: Pipe, railroad rails (limited) RESISTANCE welding: Flash welding Pressure-controlled resistance welding Projection welding Resistance seam welding: Two wheel-shaped electrodes roll along workpieces, applying pressure and current Resistance spot welding: Two pointed electrodes apply pressure and current to two or more thin workpieces: Automobile industry Upset welding: Butt joint surfaces heated and brought together by force SOLID state: Coextrusion welding Cold welding Diffusion welding Explosion welding, Military hardware. Forge welding Friction welding: Thin heat affected zone, need sufficient pressure: Aerospace industry, railway, land transport Friction stir welding Hot pressure welding Roll welding Ultrasonic welding OTHER welding processes: Electron beam welding: Deep penetration, fast, high equipment cost Electroslag welding: Welds thick workpieces quickly, vertical position, steel only: Heavy plate fabrication, construction Flow welding Induction welding Laser beam welding: Deep penetration, fast, high equipment cost: Automotive industry Laser-hybrid welding: Combines LBW with GMAW in the same welding head, able to bridge gaps up to 2mm (between plates), previously not possible with LBW alone.: Automotive, Shipbuilding, Steelwork Percussion welding Thermite welding: Railway tracks.