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Dimensional changes for 17-7 ( A -> RH950) 1

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NickE

Materials
Jan 14, 2003
1,570
Does anyone have good hard information about the resultant expansion that occurs on the treatment of 17-7 steel. We have a part with a relatively tight positional requirement on a hole. This part needs a 90degree 1t (one thickness (1mm)) bend. We threfore cant use Condition C. The final part needs UTS > 220ksi, and stainless.

I selected 17-7 condition A with a hardening treatment to RH950. My project engineer is really worried (the heat treater has produced some estimates of ~0.0045in/in expansion on X-formation to martinsite. With a final contraction of ~0.0005in/in during precipitation hardening) We can easily alter the wire cutting (for prototypes, final production will be stamped) program to take into account the change the part is going to under go, however telling the programer/wire shop that the part is going to grow "about" 0.004" per inch will not work.

Are there any good published papers anyone is aware of that could apply in this case? (IE quantitative studies, empirical reasearch) It's very hard for me to just guess, since I have to use an outside source for the heat treatment and that gets us a not too pricey batch cost, but it defiantely wont be effective to make a bunch of trials only to have to then alter the program and then finally produce the order.

Thanks for any help.

Nick
I love materials science!
 
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The problem is, it all depends on the original anneal. Sometimes you get a slight size change with the re-anneal that the RH requires.
In general, if you are working from annealed material I would expect 0.0035"/"-0.0045"/" growth.
I am also concerned about the change in the angle of the bend. It will relax, I don't know how much.
You won't really know until you do it.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
 
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