tempered martensite embrittlement

wnease

wnease

Joined
Apr 22, 2004
Messages
878
I work a lot of steel in the hardened and tempered state, and that includes using dry abrasive cutting wheels. To relieve stresses I temper again when I am finished, but have just learned about tempered martensite embrittlement. For most alloys it seems if 300 C tempering is avoided then this embrittlement will not be an issue. Can anyone confirm? Can anyone explain the factors involved? Will tempering below this temperature remove stresses caused by grinding hot?

Thanks
 
From what I remember about tempering embrittlement, the retained austenite in the hardened steel converts to martensite around 500F. The expansion from one structure to the other creates an unstable grain structure under great stress. This makes it quite brittle. The solution is to temper a second time at 400F to reduce the stress and temper the new martensite.

At least that is how I remember it.
Stacy
 
Yes, that is what I forgot. -

Quenching the steel from 600F will reverse the embrittlement.
Then re-temper at 400F.

Thanks for the link mete.

On rereading some texts, I recall now that TME (tempered martensite embrittlement) is irreversible, and TE ( temper embrittlement) is the reversible one.
By keeping the S,P, and Mn low, the amount of available elements to precipitate in the grain boundaries is low, and tends to limit the problem. This is why they are kept low in blade steel.
In all actuality, it is not much of a problem for blades, if the steel was properly heat treated in first place. Small grain size will effectively eliminate TME.

Stacy
 
Last edited:
yes thanks for the link, mete, tho it's going to take me a few readings
 
You must log in or register to reply here.
Back
Top