Hand Tools Archive

Subject:
Re: Narex chisels = chrome manganese

Kees
I could read a bit more form that article from the Sao Paulo university. Here is the conclusion:

Conclusions
Considering the heat treatment parameters and test conditions performed in this work it can be concluded that for
same hardness level quenching and tempering followed by cryogenic bath gave better performance in terms of
impact toughness for both studied steels. Even comparing with tempered martensite without cryogenic bath, bainite
microstructure did not show higher values of absorved energy.

They presume that the apparently better impact resistance of bainite in previous studies, was due to the quenched steel in those was tempered in the embrittlement temperature range, which would have reuced the impact resistant of the traditional method quite a bit.

In the Sao Paulo study they found that the traditional method of quenching and tempering gave far better impact resistance results then the austempering method. And indeed, cryotempering bettered those results even further.

The two steel types were tested at 40 HRC (pretty soft for a chisel!). I guess that is as hard as 4140 ever gets. O1 can be hardened to much higher values of course. But now we of course don't know if the same test results would be valid for the Narex steel at 59 HRC.

© 1998 - 2017 by Ellis Walentine. All rights reserved.
No parts of this web site may be reproduced in any form or by
any means without the written permission of the publisher.

WOODCENTRAL, P.O. BOX 493, SPRINGTOWN, PA 18081