Mig Gas For Stainless Steel Wire

100% Argon works well, 75Ar/25He also works well. If your shy welding amps then the Helium will help with making a hotter arc. This would be for 304,308 and 309 type SS. If having a problem welding SS, you may have some 316 or ?, then try 75He/25Ar.

T_Bone

I really should have expanded my thoughts a tad more.

Pure Argon with Mig works well on light gauge SS SM as it gives lite penetration and reduces weld splatter.

As we move to heavier SS metals we can add 1% to 5%, o2 with the Argon that helps with undercutting and adding penetration for Mig welding. Adding more than 5% o2 would cause porosity with-in the weldment.

When Helium is added with Argon, 75%Ar/25%He the weld bead is broader and penetration is improved on SS.

Then we can add Co2 with Argon for a mix of 75%Ar/25%Co2. The Co2 is primarly added to reduce the cost of pure Argon. We can also use pure Co2 for some SS types but weld splatter is a big problem.

Now we get the best of all worlds and end up with a tri-mix of Argon/Helium/Co2. With this mix we get the flatest weld bead profile, good penetration and very little weld splatter on SS.

We also can use a heavy consentrate of Helium and add Ar, Co2 or o2 for Mig welding SS. What determines the cover gas, is the composistion of the filler wire and what the filler wire mfg spec's.

These cover gasses can also be used for welding other metals.

T_Bone

Well, now you have given me something to try when I go to work on Sunday. 99% of my welding is done on SS, and a high volume of it is done with TIG on 16 ga. sheetmetal. Think I ll hook up the Argon bottle to the MM 250 and give it a try on the 16 ga. If I get good results, you just helped me improve the rate at which I finish some of my larger projects. Do you have any voltage and wire speed (IPM) recommendations?

Can you recommend books or reference material that contains the shielding gas information that you have mentioned. All my books state Tri mix or C25 (single pass) for short arc,and an argon/oxy mix of 99/1 or 98/2 for spray. I went with the 98/2 so that I could use it on steel too. Any reason you know of besides the obvious lower oxygen content that would make 99/1 a better choice.

I just typed what I remembered about welding gasses so I'm not going to be much help about refference texts.
Although I never liked Hobart welding machines or consumables, I did like there engineering texts. I had two very good ones but lost both of them on my last job in Attu, Alaska. I had taken them along for reading since it was a remote job location and my brief case was lost on the return trip, loosing some great old refference texts. I retired shortly there after and never replaced them.

M.I.T. also has some great engineering refference texts. AWS also has great refference material although very expensive.

If I can remember some text names, I will post them latter. Sorry I couldn't have been more help.

T_Bone