Heat setting extension springs

Hello Everyone,

I posted in the general engineering forum, but realized this is more in the manufacturing process of the part...

I am doing research on the heat setting process for small extension springs, in aviation applications. The material is 17-7Ph. So far I have not been able to find much online. I am under the Impression that the spring calls out for 400 Degrees (F) for 5 hours, for the heat setting process. I would like to confirm this. A question I have is; why the exact temperature and time? Is this an Industry standard? if so, where do I find the specs?

Thank you.
Brandon F.

Your ideas about the heat treatment are very fine. It give us nice and clear views.
Thanks.