How To Weld Cast Iron With A Mig Welder. If you’re welding up a machined surface, the best option would be to tig weld it. Also, you can use stick, tig, and even mig welding, so you’ll need to decide based on the welding machine you have in your possession.
However, no preheating will always make the casting weaker next to the weld and more prone to cracking in the future. The studding method can be used for major breaks in large casings. But just as other methods, you’ve got to take note of some stuff before starting up the weld.