Type of stainless in stock exhaust?

[reclino]

What type stainless is the stock exhaust made from? 409 or 304?
David
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[908/930]

That looks like mild steel, what year car?

[reclino]

This is stock exhaust from a 1986 911 turbo, It has a fair amount of surface rust like 409 stainless gets with age. The problem is not the rust but the cracking. I am going to cut out and replace the cracked section..... That's the plan anyway.
David

[Maltese Falcon]

It's either very low grade stainless steel ,or probably just likes to tarnish into this brown color.
Next time I'm out in the garage I'll put a magnet to it ...check for carbon steel.

[908/930]

You should be ok with welding in a section of 304 or 316 tube, keeping the location of the exhaust tubes could be tricky. clean up the old section with a flap wheel and degrease it.

[quattrorunner]

Yeah make a jig keep to that turbo flange exactly in the same place.

[908/930]

Can you TIG weld? You can try cleaning it up and build up the section with 316 welding rod and not cut out the section, any oil inside will be a problem though.

[Maltese Falcon]

Magnet test:
won't stick to:
Small wastegate-to-muffler pipe; dual tip section leading away from muffler; these are
stainless steel , maybe a slight trace of carbon steel mix.
Will stick to:
Turbo cross -pipe; main muffler canister and its inlet pipe from turbo: very low grade ss, or totally carbon steel.
Tig or Mig welding carbon steel with ss should be fine.
Build a small holding jig to keep the pipe from shifting during the welding session.
Also watch for welding debris on the interior walls of your repair ...get these cleaned out prior to re-installation.
Marty

[reclino]

I had planned on making a jig to hold all the geometry and tig weld in some new metal. 409 stainless is magnetic, 304, and 316 are not in there annealed condition. The entire exhaust is definitely a type of stainless, or it would be long gone by now. Stainless suffers from Intergranular Corrosion Cracking. http://en.m.wikipedia.org/wiki/Intergranular_corrosion
So trying to reweld this badly cracked section is not likely to last. Replacing with fresh metal will be pretty easy once I have it jigged in place.

[RarlyL8]

I wouldn't fix that cracked J-pipe as the rest of the pipe is in bad shape as well and the weld won't last. Better to find another one in good shape.

[reclino]

Buying a used replacement isn't a bad idea, anyone got a pipe for sale? What do these sell for used?