On Sep 22, 6:04*pm, "Ed Huntress" wrote:






Robelson found that cryogenic treatment of
stainless improved the hardness and edge holding. *I just can not
remember when, but think it was in the 50's. *So that might have been
400 series stainless before the heat treatment was refined.

* * * * * * * * * * * * * * * * * * * * * * * * * Dan

Actually, 400 is a different series of alloys, which form martensite when
heat-treated, like ordinary hardening steels. 300 Series remains austenitic
even if you heat and quench it, and it never attains the hardness of
martensitic steels.

You can work-harden 300 Series somewhat, and there are some other tricks.
But you won't get hardness from it in the Rockwell C 60+ category, as you
can with 400 Series (440, etc.).


My understanding is that 400 series stainless was used for knives with
a heat treat of heat and quench. But the results were not very good
until the quench was followed by a cryogenic soak which caused more
marstenite to be formed.

I was hoping that you knew when cryogenic soaking started to be
used.
--
Ed Huntress