Grey cast iron can be welded with oxyacetylene gas or with electric arc with special precautions (preheating in case of gas welding and post heating in arc welding) to avoid cracking in welding area. Welding of gray iron is usually restricted for repair work. Braze welding with bronze or nickel copper, is however, used for fabrication also.
Malleable irons are not considered weldable. It is repaired by brazing, preferably silver brazing.
Ductile cast iron needs special considerations in welding. It can be welded by a carbon are process and other fusion processes. For best results flux-cored electrodes having 60% nickel and 40% iron are used.