Cast iron comprises a large family of alloys that include a wide range of chemical compositions & metallurgical microstructures. Some of this material is weldable, while others require great care to produce a sound weld. Some cast iron is not considered weldable.
The major factors contributing to the difficulty of welding cast iron are its high carbon content and lack of ductility. Shielded metal arc welding (SMAW), flux-cored arc (FCAW), inert metal gas (MIG), and inert tungsten gas (TIG) welding processes commonly use nickel-based welding consumables to produce high-quality welds.