What is the filler metal used in welding stainless steel pipe to carbon steel pipe?
Yes 309 is correct. But, you can weld mild steel to stainless steel with normal fillet rod as well. The reason you use the 309 grade is that it is better suited and handles cracking and fatigue etc. It depends on what application you are using it for. If you are just doing a DIY welding job for at home, and you don’t want to have to spend a lot of money buying extra mig welding wire, filler rods etc then maybe the normal mild steel wire might just do. I know of a company that makes some fuel tanks for aircrafts, I think it is for the on ground refulling trucks actually. The tanks are square folded stainless steel sheets that are welded using mild steel filler rod. The reason for that is that is because the guy said it has better or is easier at making an air/fuel tight seal on the fuel tank….. The 309 grade mig welding wires are available in different sizes and grades ie Lsi etc Also I dare say you can get flux cored mig wires for that specific application also.
