Welding Cast IronWelding is carried out to reclaim, repair, or build up cast iron quite regularly although castings are not joined by welding very often. The most frequently used welding processes are MMA, TIG, MIG, FCAW, and gas welding. Specialised consumables are available for MMA and FCAW, and may be pure nickel, nickel-iron, or nickel-copper types. High carbon, high silicon, filler rods are available for TIG or gas welding. MIG may also be used to weld cast irons using a pure nickel alloy. Welding cast iron is always difficult due to their inherent low ductility, the presence of brittle constituents, formation of carbides, and possible variations in section. Indeed, white cast iron and some alloy cast irons are virtually unweldable, and malleable cast irons can be very difficult. Grey cast iron may be welded with care. The main problems encountered welding these materials are cracking and porosity. Welding cast iron may be attempted in one of two ways; by preheating to red heat and keeping hot during welding, cooling very slowly, or by welding cold and keeping heat input very low. Special procedures may be required to balance stresses including local preheat and indirect preheat to prevent fracture. The main safety issues depend on process but may include electrical, radiation, spatter, hot metal, and welding fume.
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