Cast irons are welded for repair of cracked and fractured parts or repair of cast porosities. Welding cast iron can be problematic due to its very high carbon content and metallurgical microstructure and metallurgical properties, like low ductility. During the welding process, carbon migrates into the weld metal and the heat affected zone adjacent to the weld metal, causing elevated hardness/brittleness. Many cast iron parts also worked under oil, water or other liquids, which penetrate to cast iron and welding become more difficult due to evaporation and causing porosity in weld seam. So welding preparation, welding technique welding consumable, machine and welding precautions are important for successful welding repair of them.
There are different type of cast irons; grey cast iron, nodular cast iron, mallable cast iron which can be welded with special precautions. But white cast iron types can not be welded anyhow because of its very high carbon content and metallurgical properties. Welding technique, consumable and welding precaution are chosen according to type of cast iron, the purpose of weld repair, service condition, part and repair dimension. Shielded metal arc welding process and coated electrodes are mainly used in repair. Most important welding techniques are hot and cold welding of cast iron. Hot welding technique includes high preheat and high interpass temperatures and slow cooling like furnace cooling of the part. Cold welding technique include short weld seams, back step welding, keeping the part temperature as low as possible by controlling interpass temperature.
Cast irons can be welded by different type of alloys, like pure nickel, nickel-copper alloys, called as monel, nickel-iron alloys, nickel-chromium-iron alloys, cast irons, steel or stainless steel electrodes. Magmaweld has developed special welding consumables for each group of alloy for repair of cast irons successfully in both hot welding or cold welding techniques. Cleaning of cracked or fractured parts can be done by carbon electrodes and abrasive discs. Good striking without crater cracks in weld and welding current control are important factors. Magmaweld power sources can provide better arc striking without defect, and they also provide easy and strick control of welding parameters during welding.