welding stainless steel exhaust

[frankv11]

working on finishing up 3" stainless steel exhaust. its is tack welded with a mig ( passport plus ) using .035 308 wire and stain mix gas. been practicing on scrap pieces but it seems like i'm going to need to get it tig welded,


so my question has anyone accomplished a good looking weld with mig and if so please share ,settings, process ,pics. I will be grinding down weld for esthetics but trying to minimize as much as possible. I'm sure I will need to purge if I decide to tackle this if its possible. .



stain mix has a lot splatter should I be using cO2 or other shielding gas.

[Vince@Meanstreets]

http://www.pro-touring.com/showthrea...(-back-purging)

heres a great thread regarding stainless exhaust. I run a separate tank and regulator to purge it. Temps are 29-38 on my Miller 180 SD tig.

Its all in the prep. Get your joints nice and tight. I get lazy sometimes on fitment but I can get by. For me its easier to TIG weld exhaust thank MIG. Slower but easier.

Practice-Practice-Practice

[Vince@Meanstreets]

your vid..

[GregWeld]

I WOULD NOT grind down welds on the SS exhaust.... they'll tend to crack. SS expands and contracts more than mild steel.

The SS exhaust on my roadster has a hairline crack at almost every weld (butt welded) joint.. it was ground down and mirror polished. I will have to re-do the entire system.

Talking with Roy Brizio about this -- he said they no longer use SS for exhaust and if they do they NEVER grind the welds.

[GregWeld]

Frank --

You don't mention if you're building a SEMA quality show car or a driver hot rod etc... if you're building a show car - I'd ONLY TIG weld. There's no way you're going to MIG it and have it look show quality. But if you're building a PT style driver that you're going to hammer... then MIG would be fine.

It really just makes a difference in what you're building.

[frankv11]

Vince thanks for info !
Greg that's one of the reasons I really would like to grind as least as possible while Have it looking good. It's going to be a daily driver / show car/ autocrosser, did not start out that way but that's where it's going now.

I'm hoping to get a descent mig weld but yes tig is the way to go. Worst case I'll see if I can find some one local to finish if.

Hairline cracks that's got to suck!!!

[GregWeld]

Originally Posted by frankv11

Hairline cracks that's got to suck!!!

Yes they do! And given the cost of a full custom built - food grade stainless - polished - headers to the tip system... I'm not happy about it!

But I'll just take the whole system off this winter and blast the insides and re-weld it and then polish the welds. It's like everything else on that little POS -- I've had to re do the entire car...

[Cris@JCG]

here is what SS exhaust looked like after running it @ RTTC this weekend on Blu Balz... I had to drive the car back from Irvine to LAX to drop off Karl @ the airport then drive to Oxnard.. I was deaf when I got home!

Notice that it did not break @ the welds.. I think my exhaust system is a little to stiff.. need some more rubber exhaust hangers..

[Sieg]

Interesting cross-over, tough to factor all the stress points with expansion/contraction and I'll assume torque twist.
Looks like some of the beads could have caused stress-risers?
Some broke behind the bead, material became brittle after welding?

[badmatt]

Looks like stress fracture. starts from no where.

Drill a hole in each end, weld it, then lap some new .065" stainless sheet over it.

Just a thought.