Embrittled 17-7

[swall]

One of our plants supplies a Belleville made from 17-7 bar, 3" in diameter, with thickness of .25" thick. It is heat treated to the TH1050 condition. So far, so good. But, for some yet to be determined reason, the plant gives these a supplemental age of 1060F for 3 hours. A high percentage of the parts crack as they are loaded up in the assembly. My question: is this overage the plant is performing embrittling the 17-7?

 

[mcguire]

How were the parts descaled after the last heat treatment? Any chemical which removes oxide also can introduce hydrogen.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[saberblue]

You might want to take a look at the machining process the 17-7 work hardens easily and that might be the source of your problem

A.R. "Andy" Nelson
Engineering Consultant
anelson@arnengineering.com

 

[EdStainless]

I would also suggest that you rough machine and then age adn final machine. These harnesses are no real problem and I am concerned that you are getting two issues.
1. Work hardening in machining giving you CH conditions and low ductility at the edges.
2. and because you are machining soft material you are getting small tears smears along the highest stressed edges.

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