Stainless steel welding with a MIG?
 

Hi,
The DIY stores sell welding wire for MIG for stainless steel welding. I thought you could only weld stainless steel with a TIG, but if the wire does exist, it means that it should be possible with a MIG, no?

I need to weld the stainless steel tubes of my exhaust system, and giving them to a professional welder will cost me a lot of money again.

Shall I try with my MIG, or do you guys absolutely not recommend it? If it is a yes, will my shield gas (Argon + 18% CO2 + 0.03% NO) work for that?

Thank you :)

Yes you can MIG stainless with your current gas how ever it's not as soft as mild steel so it needs a lot of heat. I would suggest turning the amps up and the wire feed down and instead of trying to do long runs take it slow, I would tack space tack space grind flush then fill the spaces that way you know you've sealed the join. It would also help if you match the grade of stainless to the filler wire but I think you have enough to worry about already.

AFAIK you need pure argon to properly shield stainless. However, at worst you'll have a rusting seam.

You only need 100% Argon if you are MIG welding Ali which is a whole new world of ball ache. The seam won't rust if you use Co2/Argon mix on stainless but you will get spatter which will make a mess of the surrounding material the same as welding mild. The reason TIG is prefered over MIG on stainless is it pre-heats as you go as material like 316 is hard stuff. Tig is used in production welding of stainless as there's no need to clean the weld up after it's been done, with most of it being on show in things like kitchens and bits of boat which saves time and money.

Welded stainless with normal wire and Co2 before with no probs,not pretty but effective and for an exhaust that will get bloody hot will it matter.

You need to use mild filler wire for joining mild to mild , stainless for stainless to stainless and so on. As your making an exhaust system it will go through constant heat changes, it will just end up shearing off after a while if you try mixing mild and stainless.

While you most certainly can weld dissimilar steels Phil is right the only way they work is when they are similar or have a dedicated filler/spool of wire mild on stainless will not last for two reasons one has a different expand contract rate to the other this is a perfect recipe for stress fracture especially on an exhaust ie hot cold hot cold the other fact is that it will rust along that seam even some stainless mig wires will rust as well, as the heat involved changes their properties, I would try to get grade 316 better still 316H or even better again would be 316Ti which contains a small amount of Titanium which helps with the weld boundry.
At minimum you want 316 for it to look and perform better

Were you a welder in another existence ?. :p

Austin & Pickergill time served plater.... ah built ships me:D

WF and JR Sheperd,drove the wagon that took the scrap away,same one that featured on Spender .;)