stainless vs mild help
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Teching In
Joined: Nov 2013
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stainless vs mild help OK got a problem, need all ur badass guys expertise Gonna start building my 2.25 hot side and I would love to do stainless but only have experience in welding mild steel. I use a miller 220 for a welder but don't know if I need to use diff wire or anything. I'm concerned I'd be better of with steel. Don't think I know enough for stainless help please. Thanks
Has anyone had mild rust on the inside and cause problems with the turbo? I would think it would be fine. Look how the turbine housings rust anyways. I am planning on using mild as well unless someone sees a problem with it.
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FormerVendor
Joined: Feb 2011
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Aluminized tubing holds up a lot better than plane mild steel.
Wrapping mild steel will shorten it's life span. If something needs protecting from heat wrap it not the tubing when using steel tubing aluminized of not.
The correct way to mig weld SS is to use a trimix and SS wire.
You can weld SS with steel mig wire and C25 Mig mix "25%C02 75%Argon"
You won't find the spec's for how to do it in a book, and the guys that haven't done it will say you can't do it..... but you can.
SS is best welded using the Tig process.
Since you have a nice mig welder just build it with aluminized tubing if you on a tight budget. If you budget will allow SS fab up your parts and tack it up with your mig have someone tig the rest.
Wrapping mild steel will shorten it's life span. If something needs protecting from heat wrap it not the tubing when using steel tubing aluminized of not.
The correct way to mig weld SS is to use a trimix and SS wire.
You can weld SS with steel mig wire and C25 Mig mix "25%C02 75%Argon"
You won't find the spec's for how to do it in a book, and the guys that haven't done it will say you can't do it..... but you can.
SS is best welded using the Tig process.
Since you have a nice mig welder just build it with aluminized tubing if you on a tight budget. If you budget will allow SS fab up your parts and tack it up with your mig have someone tig the rest.
just remember if you tack it up and have someone else tig it.... zero gaps or you'll be paying in the end!!!
Mild steel is fine, its been done a million times over. If you wrap anything it will promote cracking. Id rather see mild steel over aluminized due to if the kit gets hot enough the aluminum coating will flake off. Stainless kits look like **** after running race gas and letting it sit too, So unless you dug up an old carbon steel sewer pipe and are building the kit from that... pick your material and start welding!
Mild steel is fine, its been done a million times over. If you wrap anything it will promote cracking. Id rather see mild steel over aluminized due to if the kit gets hot enough the aluminum coating will flake off. Stainless kits look like **** after running race gas and letting it sit too, So unless you dug up an old carbon steel sewer pipe and are building the kit from that... pick your material and start welding!
I wouldnt purge weld anything unless you planned on it being used for the dairy or medical industry. No one sees the inside of the pipes and i cant count how much gas piping mild and SS ive welded and never purged....no point. Buy some stainless wire for your wire feed, practice on a couple peices and have at it. Instead of running one continuous bead you might have to throttle the trigger depending on how thin the piping is. If you can MIG weld with mild, you can MIG weld with SS.... not difficult at all and no real science behind it.
Best way to avoid anything moving while welding is to have everything fully welded and done except for your last joint. Get 99% completely done, bolt it all back up and then do the last joint, weld as much as you can of it in place. Its amazing how much a pipe shrinks and moves while welding. Most people cant comprehend it untill they ruined it and have to cut it all apart and start over. 
just remember if you tack it up and have someone else tig it.... zero gaps or you'll be paying in the end!!!
TECH Enthusiast
Joined: Jul 2013
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From: Okmulgee, OK
TECH Enthusiast
Joined: Oct 2012
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From: Arkansas
There's 20 different ways to go at it. When I started building my on kits I didn't have a tig. I learned by doing . If you have access to stainless use it . I t definitly looks nicer and to me it welds better but if all you got is mild get after it . I've had three different turbo kits with mild steel and never had problem.
Use what you like and can afford. Stainless needs to be pack purged, aluminized needs to be stripped at the sight of the weld (it is toxic) mild should be coated for longevity. Fit up is everything when welding regardless of the metal used. If i was working with a mig, i would go mild and have it ceramic coated. With the mig you will need to take short breaks to let the pipe/tube cool or it will heat soak and you will start blowing through it. Good luck
The weld only needs to be on the outside. A lot of stuff I see no one adds the correct amount of filler rod, they fuse it more than welding it... more heat than filler, so of course they burn the **** our of it. Sure it looks pretty but isnt how you do it. It also doesnt need to be welded with 100% penetration as I doubt any of them get x-rayed.
The only way a weld should come through to the inside is if you leave a gap, and the gap is so the bead forms no the underside making it 100% You could do that but unless you are running high pressure and need to meet specs..... waste of time on a low pressure system. 
About every answer under the sun here.
I used aluminized and mig. Where I could, I tacked on the car. Where I couldn't, I marked, removed, tacked and reinstalled to check fit. I welded one joint at a time before fitting the last piece. It's time consuming for sure.
The aluminized coating is removable with a wire wheel.
Fit is important, gaps are a bitch. I don't have fancy equip like a sanding wheel or a band saw. So I use a chop saw and a file.
Watch out on the outside radius of mandrel bends. The pipe is thinner there. Perfect opportunity for blowing through.
If you tack really well, 3 places around each pipe, I don't find that things move at all. With pipe, it's very hard to do continuous weld with mig. So by nature you have to stop flip the work and continue.
I wonder if mild steel coated ends up costing more than stainless and no coating? I had a set of headers coated locally, it was $200 which is typical. Seems time that would push the cost of mild beyond SS?
Have fun!
I used aluminized and mig. Where I could, I tacked on the car. Where I couldn't, I marked, removed, tacked and reinstalled to check fit. I welded one joint at a time before fitting the last piece. It's time consuming for sure.
The aluminized coating is removable with a wire wheel.
Fit is important, gaps are a bitch. I don't have fancy equip like a sanding wheel or a band saw. So I use a chop saw and a file.
Watch out on the outside radius of mandrel bends. The pipe is thinner there. Perfect opportunity for blowing through.
If you tack really well, 3 places around each pipe, I don't find that things move at all. With pipe, it's very hard to do continuous weld with mig. So by nature you have to stop flip the work and continue.
I wonder if mild steel coated ends up costing more than stainless and no coating? I had a set of headers coated locally, it was $200 which is typical. Seems time that would push the cost of mild beyond SS?
Have fun!