Fine Blanking 17-7PH (TH1050) .032" Sheet

[mighoser]

My current process blanks this material post heat treatment due to constraints on tolerance. We understand there is risk to this especially if the material is hardened beyond limits specified in AMS 2759/3 (38-44 HRC). Since there is a .0045" dimensional change from condition A to T, I would like to try blanking after condition T (31 HRC) instead of post heat treat. Is there a maximum time which these parts could be held at room temp between transformation and precipatate hardening? The spec says hold below 60 F for not less than 30 mins. Any other hazards of fine blanking at condition T? Am I mitigating any risk by taking this approach?

 

[EdStainless]

My choice would be to cool the material even colder (-50F?). I don't the hold time as being an issue, but maybe some testing would be in order.
How long do you think that the delay might be?

It might help. If the edge cracking is related to the low ductility in the aged condition, then it will help.
If the cracking is because of microstructural problems (excessive carbide growth) then it may not help much.

Either way the tooling will last longer and you will have better edges.

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[mighoser]

Ed,

It depends if the supplier is subing out the heat treat operation. I can see heat treating a bunch of material to condition T then shipping it to them for fine blanking then back to the HT house for PH aging. I would prefer no limit to room temp exposure at condition T. Can you order material in condition T? The answer might clue us in on its stability.