welding stainless steel exhaust

[frankv11]

Originally Posted by GregWeld

These guys supply the BELLOWS style with an internal slip joint for smoothness....



http://www.spdexhaust.com/pdfs/AccPDFs/Bellows.pdf

Those are exactly what I'm looking to buy, with interior sleeve / directional. I could be wrong but the ones that I'm replacing don't seem like they would be compression friendly. I need some that will compress when exhaust stretches out from its natural state to eliminate some of the stress , tension , binding.

I'm doing a bit of research on how much it will actually stretch. The only thing I'm missing is the over all running temperature of the exhaust system.

[GregWeld]

Originally Posted by frankv11

Those are exactly what I'm looking to buy, with interior sleeve / directional. I could be wrong but the ones that I'm replacing don't seem like they would be compression friendly. I need some that will compress when exhaust stretches out from its natural state to eliminate some of the stress , tension , binding.

I'm doing a bit of research on how much it will actually stretch. The only thing I'm missing is the over all running temperature of the exhaust system.

The exhaust on my short little '32 ford grows an inch!

[frankv11]

Originally Posted by GregWeld

The exhaust on my short little '32 ford grows an inch!

mine is defenitly going to grow a lot more than one inch...LOL

[snappytravis]

I was recently thinking of stainless exhaust for my 69 camaro. After reading throught this thread I am having second thoughts, What about using regular steel exhaust then having powder coated?

[preston]

Yeah I'm surprised the brain trust here is down on Stainless exhaust. I built many custom steel exhausts and its expensive to coat and my experience with the local coater down there in Auburn hasn't been that great durability wise (scratches then rusts). I finally built a full SS exhaust for my rig and was so much happier with the appearance and performance. I constantly change things so I appreciate being able to cut apart the exhaust and re-weld it without having to get it recoated. I do have a flex joint and plenty of very flexible hangers. I must be the really odd man out because I build my turbo headers from steel and my exhaust from SS and haven't had a problem with either and the car has been tracked several times.

Anyway, my question is back to welding SS - I've read many times your welds/metal should be silver or gold colored or at least shiny when done and that gray is bad. Well most of my welds ended up gray - its been a while since I've welded SS so maybe it would work out better now but I'm having a hard time figuring out what I was doing wrong. I think the gray is too much heat ? But I work that pedal up and down and only use enough heat to do the job, obvioulsy if you use too much you blow through and not enough is easy enough to see. This was mostly on 3" exhaust without backpurging, but including many v-band flanges and such where there was no open air backside. TIG welding using .063 stick on .063 wall thickness runnnig pure Argon (or whatever the standard TIG mix is) and probably 65-75 amps at full throttle on my Lincoln square wave.

Any tips on what I'm doing wrong ?
BTW I've never had any SS weld crack although I never grind them down.

[dontlifttoshift]

My experience is too much heat makes it gray and chalky. 65 to 75 amps sounds about right but I very rarely hit wide open, I don't back purge exhaust either unless it is being polished. It's not just the amount of heat but how long you put the heat in. That's why fitup is so important, if you are trying to "bridge" a gap that requires some time and that can burn the color out of it. That's been my experience.

Here's a secret, I don't even use filler rod on the seams of unpolished exhaust. SShhh.....the welding nazis get mad when they hear that, but that's the way I do it and I have never had a problem.


Headers are another story, I always backpurge.......well not really. I use a local shop that welds sanitary stuff all day, everyday, they do it so cheap its not worth my time. Same with polished exhaust, I tack it and drop it off, and it comes back polished

[preston]

Thanks for the tips. My TIG welding has come a long ways since I last did SS so maybe it will come out better next time. I mostly do aluminum but lately I have been doing alot of bodywork and I have been having success fusion welding 20 awg steel which makes me absolutely giddy. So yeah I would probably do a better job on moving quicklythat was probably my issue, spending too much time in one spot. I have found you are better off leaving a bad bead or void in your wake in order to keep the heat moving and going back and melting/fixing rather than lingering and trying to fix it then.
Not sure I would trust fusion welded exhaust pipes though, need the extra strength there. On body patches not so much.

[dontlifttoshift]

Originally Posted by preston

Not sure I would trust fusion welded exhaust pipes though, need the extra strength there. On body patches not so much.

You got that backwards, ridiculously expensive paint jobs go on the body work.

You have built the exhaust so you know, Have you tacked one joint together and then had to take it apart? 4 good tacks and you have a hell of a time getting it apart.

A 3" tube has over 9" of weld holding it together at each seam. Again, fit up is key. A perfectly fitup joint will fusion weld with no problem. The sanitary guys have automatic welders as well. There are two styles, one that spins the pipe and one that spins the tungsten around the pipe, neither one uses filler of any kind.

Another thing that will make it gray and chalky is dirty tungsten or getting a contaminant in the weld.

[funcars]

Coeff of thermal expansions for those who like specs: - 304 11x10E-6 in/in/deg F, 321 11.4x10E-6, 316L 10.8x10E-6, low carbon steel 6.3x10E-6

[ccracin]

You also must remember that the tubing gets cooler the further back you go. It becomes a fun calculation!