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  for Metal Finishing since 1989
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De-embrittlement of stainless steels

Is it necessary to de-embrittle stainless steels (both austenitic and martensitic) after zinc plating?

Wayne Ward
Consumer - Basildon, Essex, England
2007

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First of two simultaneous responses -- 2007

"Necessary" to do what or for what reason? Some people use Rc of 32 and many use Rc of 36 as a point where it must be baked.
It really depends on what it is going to be used for and what % of over design is in the part.
The one absolute is you must follow your customers desires.

James Watts
- Navarre, Florida

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Second of two simultaneous responses --

It depends on the strength of the steel, if it is over 1100MPa then it does.
If you were to de-embrittle everything then it may add some cost to the parts but at least you will guarantee that the ones that definitely need it are done. De-embrittling lower strength steels will not hurt them.

Brian Terry
Aerospace - Yeovil, Somerset, UK
2007

The answer is maybe for austenitic and yes for martensitic. In general, any steel parts that are hardened to 32 HRC (320 HV) or higher need to have some type of embrittlement relief. Most parts using austenitic stainless steels are well below this limit, usually because the raw material has been annealed and no significant hardening occurs during manufacturing. Some of the metastable austenitic grades like 201, 301, and 302 can strain harden very quickly during deformation, and when processed to very small dimensions (thin sheet, small diameter wire), become very strong/hard, and therefore become susceptible to embrittlement.

Toby Padfield
Automotive module supplier - Michigan
2007