Annelaing 321 stainless 1

[goucho]

I wasn't sure where to post this so I posted it in the Metal and Metallurgy forum as well ([URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=375377[/url]). I would like to anneal 321 at 1900F and what to know how it will react. Here's my case:

We've been thermal forming a piece of 6-4 Ti between an inner ring of 321 and an outer ring of 410. The 6-4 piece is about 9 ft in diameter (in two halves). We're using the differing CTE's to cause an interference between the rings to form the 6-4 at 1350F. After an initial 10 cycles, the rings size are set and they stay pretty much the same diameter for another 50 cycles. After that they start to creep. The inner gets smaller and the outer gets bigger, thus reducing the interference which causes the 6-4 to be partially formed. We are now at ~120 runs and the part is out of contour.

In an effort to bring the interference back, we are going to be cutting the inner ring in half and basically shimming it outwards. Before we do that I wanted to try annealing the inner ring to 1900F for about 7 hours (it's 9" thick). I don't really care about fixing carbide precipitation since it is not in a corrosive environment. I'm thinking though that this should relieve the stress that's been built up from the repeated compression of the ring, hopefully causing the ring to expand back towards the nominal diameter. This way the initial interference will return and the part can then be fully formed.

However I'm afraid that since the part will soften up, it may cause undesirable effects when it goes in for the first interference cycle after the anneal. What should I be concerned with or what should I take into account? Should I try annealing the outer ring as well?

Thank you for taking the time to read this!
-Benjamin

 

[weldstan]

Creep caused deformation cannot be recovered by your heat treating method.

 

[EdStainless]

annealing the 321 will only often it.
If you are worried about residual stresses then try a stress relief, however your 1350F should be a very effective stress relief temp. so I doubt that residual stress is involved.
I don't see how any heat treatment will help your situation. Just make the mechanical alterations.

As for the 410 part, which 410 grade is it (what is the C content)?
If it is over 0.08% C then it should be re-heat treated by taking to the austenitizing temp and quenching it. Then you can temper it by putting through one of your 1350F cycles.
If it is low C 410 don't bother trying any heat treatment on it.

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