Straightening the stainless weld job

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Boris,

Congrats on a job nicely done.

I'm of the opinion that you could get the material to relax enough to improve flatness, but it would likely require clamping it to something with great mass, so it isn't overcome by the tension of the manifold. Even then, it's likely to be improved to some degree, if not made perfect. It's hard to see the amount of warping that concerns you. How much can you measure?

One thing for you to consider, and I hope it's not an issue for your application. 304 stainless, along with almost all other of the 300 series materials, undergo intergranular corrosion when subjected to temperatures from 800 F through 1500 F. The repeated heating cycles you speak of

Harold

Boris, Try posting this over at sci.engr.joining.welding. There are a bunch of very helpful guys over there that should be able to help you with your warpage issues. Try pinging Rob Fraser at that group. He builds high end exhaust and manifold for big drag racing engines and has been very helpful to others with exhaust system problems.

Greg Postma

I have nothing useful to offer here other than congratulations. That is one neat looking job. I can see what you're talking about, hope someone can answer your question usefully.

After what I

material if I

chunk of high

engine head

learning

Boris,

I scanned a few pages from "Stainless Steel Fabrication" on annealing. Don't know if it will help you out or not. It's the first time I've really looked at the book since I picked it up at a sidewalk sale. There's over 350 pages, 70 just on cold forming...

My $0.02;

- don't put it in the kiln as it'll likely pretzel even worse on you

- how bad is it? can you just bolt her to the head and pray it doesn't rip out the studs? If you can bolt it flat that's probably your best bet. It'll still move once you use it.

I think I would use a very thick gasket ( or two or three regular gaskets ) and install it. It will get pretty hot in use and I would think unwarp at least partially. If you still have problems with exhaust leaks, you can take it off and see if it is closer to being flat. If it is flatter, you might have enough thickness to machine it really flat.

Dan

NICE job of fabrication!!!!

It needs to be straightened AND stress relieved AND machined flat. If you just clamp it down, it is likely to leak and erode either the manifold or the head. If you don't machine it flat it WILL leak.

You have enough time and effort > Gentlemen,

That is what I am was about to try now. I have it bolted to a chunk of steel with some shim in strategic places. Someone posted that I should get it hot in the area where it should expand and than quench that spot. The theory being that quenching will cause it to contract less.

How about heating the area that needs to be enlarged and peening it while red hot?

It appears from the pics that the curve of the flange is fairly uniform. Because the metal shrinks as it's heated, on similar items I have been able to use the tig on the longer face to selectively heat areas and shrink that face back to fairly straight. It's a little bit "by guess and by golly" and you could end up making more of a noodle if you overheat any one place. It's often done with a gas torch also but I've had good luck doing the same thing with the tig and a rounded end electrode to get a wide "brush" instead of a tight arc. The mounting holes will move also...depending on how oversized they were you may have to re-drill em.

FYI, the legs of the space needle, about 1-1/2" thick plates welded into H beams about 5 feet on a side, were curved using torches to heat and selectively shrink the metal.

With care, you can probably get it flat enough to mill the surface flat without taking off much material. You have to do an area, let it cool, and do another or you will probably over-do it.

Koz

That stress relieve procedure is a mystery to me. I have aces to a large kiln. What material do I bold it to so that it too does not get pulled out of shape due to softening under heat?

You can either expand the proper side by heating and peening or shrink the opposite side by heating and quenching.

This info is pasted from another post: Your project was interesting enough that I talked to my resident metalugist this evening. We agreed that you will need to straghten it first using a combination of heat, shrinkage, and heavy clamping pressure, then anneal it PROPERLY considering it is 304 Stainless. He suggested this site for tech info on the anneal process.

Keep it up, I th> >