Various welding processes that can be used for joining the metal parts are solid phase welding, arc welding, resistance welding, thermit welding, ultrasonic welding, electron beam welding, laser beam welding and explosive welding. Solid state phase welding can be further classified into five categories- forge welding, butt welding, oxyacetylene pressure welding, flash butt welding and friction welding. In forge welding, the parts to be welded are heated in a furnace and then hammered together to form the weld. Electric current is used in Butt welding. An Oxyacetylene ring burner is used in oxyacetylene pressure welding. In flash butt welding, the parts are brought in contact with a light pressure and followed by the passage of an electric current. Heat due to friction is employed in friction welding.
