Gas welding is a non-pressure process using heat from a gasflame. The flame is applied directly to the metal edges to be joined andsimultaneously to a filler metalin the form ofwire or rod, called the welding rod, which ismelted to thejoint.Gas welding has theadvantage of using equipment that is portable and does notrequire an electric power source. Thesurfaces to be welded and the welding rod arecoated withflux, afusible material that shields the material from air, which would result in a defective weld.
Arc Welding
Arc-welding is the most important welding process for joining steels. It requires a continuous supply of either direct or alternating electrical current. This current is used tocreate an electric arc, which generates enough heat to melt metal and create a weld.
Arc welding has several advantages over other welding methods. Arc welding is faster because the concentration of heat is high. Also, fluxes are not necessary in certain methods of arc welding. The most widely used arc-welding processes areshielded metal arc, gas-tungsten arc, gas-metal arc, andsubmerged arc.