Hi Rachael,

Welcome to the forum!

Your simple question is really rather complicated.

It takes less amperage to Tig stainless in most cases, however the travel speed is slower, so in some cases more overall heat input occurs with TIG than with Mig.

Stainless (in general) has a low coeffeicent for thermal expansion... (heat travels slowly through it compared to other metals) This can cause heat to build up near the weld zone and bad things can happen (sensitization, cracking and lack of corrosion resistance and other bad stuff) This will also be a consideration for distortion control in fabrication.

GMAW-P (pulsed Mig) can go fast and make a fillet about the same size as Tig in materials down to about 0.45 (19 ga) in all positions... Since it goes fast there is less heat input than with GTAW and this means reduced distortion.... Less control than GTAW but way better for production and automation when practical.

Maybe those thoughts will help you hone your questions... The more specific the question the better the answer you will get from the folks here..

Hello again rachelpoison, I think you can see from the post that Lawrence left for you how there can be many different things that can come into play when considering your question. I might throw a few more topics in for consideration. Stainless steels come in a wide variety of alloys and compositions, these alloys are likely to increase in differences and purpose over time, new ones are being developed and possibly revised all the time. Some of these alloys are compatible with one another and some aren't. Various welding methods can be employed to weld these materials(as Lawrence alluded to in his post) and in many cases this may be a decision that you will have to make and in others it could be a predetermined choice. I would say some of the important points revolve around a few specifics: proper identification of alloy(stainless alloy identification can be very problematic and can require various methods for determinations of alloy type, fairly expensive in many cases and time consuming), this would then likely determine the filler metal to be used and could also address the type of service that the part(s) could be used for, proper welding process for fabrication or repair of item, will distortion be an issue and will this require monitoring of preheats, interpasses, postheats, or possibly post weld heat treatments?, is this an item that will be fabricated in a shop, in the field, underwater, all of these considerations might come into play as a process is selected to perform the welding?,  are the materials compatible?, is there more than one type of material being joined or possibly multiple materials, and is there a filler metal that will address these differences? The majority of the answers to the questions above will likely be determined by an engineer, but it still helps you to have an understanding if you happen to be the welder or fabricator on the project. Hope this may have shed a bit more light in the direction of your question. Regards, aevald