Stainless Mig question

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Let me preface this by saying I did search and ran into a lot of discussion of various MIG processes and applications that had absolutely nothing even remotely close to the situation.  Situation:  110v Northern Mig welder, 304 stainless steel tubing and bracketsMy friend wants to use his mig to weld some stainless tubing (exhaust) and to weld some brackets.  With his 110v Mig welder, what would be his best choice for a gas to weld these items.  Brackets would likely be 1/8" or less.  I offered to tig the stuff for him, but it would involve tacking up all the pieces and then transporting them all 1.5 hours away to finish all the exhaust without having the vehicle for test fitting as we go.  So if he was to get a bottle for welding the stainless, what would be the preferred gas for this application?  Some were saying tri-mix would not be good with a 110v machine, I have no clue about 100% argon (what I use for tig).  And then there are several other 98/2, 98/5 mixes but again, not sure if any of the above will work on his machine.
Reply:I would think the standard Helium tri-mix (90 / 7.5 / 2.5) would be best for this situation since you're short-arcing and not spraying.  Much over 5% (some people say 3%) on the carbon dioxide and corrosion resistance suffers.  I wouldn't try straight argon.  If it worked everyone would be using it.I'm not sure what the 110V power source has to do with what mix you'd use as I have never owned a mini-machine.Last edited by tbone550; 05-24-2012 at 06:53 PM.
Reply:No clue, just something that was mentioned in one of the posts I found....something about not being to even weld 22 gauge (I guess meaning really thin material) with a 110 machine and try mix.  I am still very new to welding in general much less anything other than mild with a mig, so I figured I would ask the folks with more knowledge than me.
Reply:he might be a lil surprised at the cost of the wire for the mig Tri mix for gas also expensive considering Helium is at a premium right nowMiller Xmt 350Lincoln Ln-25Ahp 200xSmith Gas Mixer AR/HTig is my Kung FuThrowing down dimes and weaving aboutInstagram http://instagram.com/[email protected]
Reply:So no one has any reasons why tri-mix would not work on his 130 amp 110v machine?  He is going to have to buy a new bottle as well, so he is going to have a little investment.  I told him just to drive the truck up to me with open headers and we could work on it
Reply:A 110V MIG is not the ideal tool for the job, but a few tips might help:Argon with 2 - 5% CO2 would be the best gas, but not easy to use out-of-position. The reason some people do not recommend tri-mix for a 110V MIG is that Helium mixes require higher voltage than Argon mixes, and the smaller MIGs are voltage-limited.Get 308LSi wire rather than plain 308. The added Silicon makes a "wetter" bead and should give you better fusion with high-Argon blends.Proper fit-up is important- consistent but small gap for adequate penetration without burning through. Definitely practice on some scraps first!JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:On thin, .065 and smaller tubing will the 130 amp be ok with tri-mix?
Reply:Worked ok for meMiller Diversion 180Hobart Handler 140 (Soon to be replaced with Miller 211?)Miller Spectrum 625 Extreme
Reply:In general, tri-mix gas (helium, argon, carbon dioxide) is the usual gas recommended for short-circuit transfer mode GMAW welding of stainless steel.You can find that information at the Miller, Lincoln, and ESAB websites.  As well as many others.  That said, a GMAW weld depends on four main items working together correctly in order to get a 'good' weld:- the welding machine, which has to have the ability to produce the 'proper' voltage and current profile for the task at hand, which depends on the filler (size and type) and shielding gas being used;- the filler (size and type);- the shielding gas (type), has to be appropriate for the base material being welded as well as the filler being used;- and the operator.And yeah, your friend may be in for a bit of a price shock picking up even a 'small' bottle of tri-mix and a 'small' 2 lb spool of 308 wire.Although some 120V MIG machines can weld stainless steel, I do not know for sure one way or the other if the Northern machine can or can't do so.I know my 'small' Lincoln 120V wire-feed machine -can- weld stainless using tri-mix.But would I want to use it to weld some kind of relatively thin stainless exhaust tubing?  Not as a first choice.  If GTAW is available, that would be preferable IMHO.Don't forget the back-purge of the tubing.  The best laid schemes ... Gang oft agley ...