A couple weeks ago an old man brought me a LARGE 1/4" thick stainless pot and top hat he wanted to assemble to cook alkyhol......I had never welded stainless either mig or tig, so told him to bring stainless wire filler and I'd attempt it tig.....I didn't have tri-mix nor spool of wire and didn't even want to bother to price it nor expect the old moon shiner would want to pay for it...And told him I was NOT going to town to find it....He arrived with a fist full of wire and his bed full of stainless parts.

I have no idea what grade of stainless the pot was and the filler wire....but it welded well with my HTP-221 tig...A first for me, so I did it free.

Yeah, I know you are asking about MIG stainless, but I want to add that tigging it seemed really no different than tigging thick plain steel....Well, except my 150 amp torch got hot quick, so I bought a 250 amp 20 series torch and water cooler immediately afterwards.

 

depending on the service for this piping, solar flux might be the answer for your inside diameter protection. Code shops will often employ Lincoln STT welding systems or possibly the Miller RMD or PipeWorx combos, I am sure that Fronius and others have similar systems that do the same. Whenever SS is welded without providing for an internal purge you just have to have procedures that are proven to provide adequate finished results for the root pass/internal weld zone. Best regards, Allan

 

Bump your gas up to 45-50cfh and drop your volts to about 19, the soot will clear up with more gas.

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Going to play with some 308 MIG and tri or try mix for my shield. Backing gas needed for pipe welds?

 

15 cfh seems a bit low to me, but the weld looks good. What size nozzle is on your gun?

 

Try upping the volts a bit and add more of a circle motion...

 

If its thick enough to get away with it, stainless fluxcore can do some wonderful things...

Trimix(90/7.5/2.5 HeArCo2) works good, 92Ar/2Co2 works good too...
Inductance control helps a bunch with stainless short circuit. A bit more voltage will help to a degree...
Motion will help tie in the toes and can help with over all penetration depending on your joint setup.
Stainless is sluggish, it will Not penetrate like you think it would. It will stick to its self pretty well if you move fast enough...
Purge/copper backing and open roots/open corners are your friend...

 

Played around a little more today.
I went up to 20v/240ipm. Inductance is at about 90%. For my motion I led a little bit in the bottom toe then dipped back for the top.
A little more spatter than I would like, but I won't get too picky on that right now.

I set the gas about 30cfh. Any higher and it started to burn back.
That's on the "Helium" range on my flow meter. It doesn't have a scale for the mixture. How far off could it be?
Forgot to measure the nozzle size. I think it's 5/8"

If its thick enough to get away with it, stainless fluxcore can do some wonderful things...

I'm only on 1/8". But that look really nice. What wire is that?

Thanks for the help so far.

Edit:
I ran a downhill pass and got that nice rainbowish tint in the weld. Is that at all indicative that I may be a little off in my flat settings?

 

I would run it way hotter. But I like doing stainless hot and fast while pushing the puddle laying in a strait bead with little to no manipulation.

 

I'm going to try a hotter setup tomorrow, try to get it flowing smooth like the pictures posted earlier.

 

Picked up a bottle today and ran a few beads. Didn't have a lot of time, but this is what I came up with.
Seemed to run pretty smooth and easily. 17.6v/200ipm. I set the tri-mix to about 15cfh but didn't have the time to play around with settings much.

Hopefully will have a little time tomorrow to dial it in a little smoother, and thoughts/suggestions?

 

Kobelco are making a flux core wire for gage sheet. It is great. Work well with c25.

 

Around here, 120cf bottle of Tri-Mix is like $70. So it's only like $30-$40 more than the standard C25. And it's worth every penny. Stainless is tricky to weld, but get a couple scrap pieces of stainless first and practice on it. It's similar to welding steel, only different. The puddle doesn't flow as well. And as stated above, turn up the inductance, it helps with the fluidity of the puddle.

 

Do not use pure argon. It will produce a tall weld that likes to stack up on its self.
I am cheap so I mix my own 2% to 5% CO2 argon mixture. Have to dial it in on a piece of scrap.
I would like to use try mix but have not yet. Everyone says that it is the best.

 

used an 045 dualsheild stainless wire welding 304 when i worked at the shipyard. c25 shielding gas. it was easy to use the only difuculty i had was vertical-up on less then good fit-up. never paid much attention to who made it, but i imagine it was lincoln as that was all that i can remember being on hand.

 

Your asking so here's my 2 cents worth.....The KEY WORDS in your post are " NO EXPERIENCE" Do your self and the customer a favor and pay someone to build the tank and you can install it. Welding Stainless is NO JOKE.....and not an entry level project....

 

How about prep work for this. Anything out of the ordinary?

The KEY WORDS in your post are " NO EXPERIENCE"

I totally understand.... but the added time and effort will at least get me another process I can handle. It's a relatively small tank so all it has to do is not leak.

used an 045 dualsheild stainless wire welding 304 when i worked at the shipyard. c25 shielding gas. it was easy to use the only difuculty i had was vertical-up on less then good fit-up. never paid much attention to who made it, but i imagine it was lincoln as that was all that i can remember being on hand.

I hadn't thought of dual shield. I'll keep that in mind. I can do all welds in the flat position so it would work for me.

 

I just finished up a stainless mig job on a chemical sprayer tank. Tri mix is absolutely the way to go. I ran out with one fitting to go and had to switch back to C25 for the last weld, it got the job done, but there was a huge difference between the two.

 

Tri-mix is necessary unless you plan on reinventing the wheel. I just finished putting a stainless truck mounted salter back together (BRAND NEW) that the operator backed up into the salt pile and taco'd the chute/spinner. Sorry, no pictures.

 

Thanks for the reply. That's nice welding there.
I'll price some tri-mix tomorrow.

 

It's pricy but the helium gives you the energy in the arc to get good melt off, I have also herd of people using 98%argon 2% co2 with good results, but I know that the tri mix works.

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Pics

the second pic is a corner joint that is only 3/16 toe to toe.

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first weld is nice second ? why ?

 

I do a lot of stainless MIG at work try mix is a must, your wire will work nicely we use it on our 304L. As far as settings on 10ga I start at 18 volts and 225IMP and turn your inductance(crisp/soft setting) up high.