Understanding cast iron and repairing damaged castings ...
by first preheating the casting to 1500 deg. F. The casting will be bright red in color. Cast iron melts at approximately 2400˚ F so there is 900˚ between the preheat and melting point of the cast iron. The welding is done with an acetylene torch and bare cast iron rod which is just a stick of clean cast iron as the filler metal.