Its my understanding (and an earlier post from James stated as
such) that you can't heat harden Stainless. As stated in earlier
posts, the problem with annealing stainless is that with slow
cooling the chromium tends to crack etc. My research confirmed what
earlier posters have stated And one source that I encountered
stated the importance of cooling rapidly that ice water should be
used. I took it to mean as cold as you could get it.
Stainless steel has a tendency to build up stress, and to warp.
Heating needs to be an even heat.
Most stainless steel will harden in a light oil, some are air
hardening, it’s possible.
The tempering process “must” occur pretty much straight away. Either
a traditional temper or a sub-zero quench, depending on the stainless
alloy. A data sheet is handy. If you have mystery stainless, then
you have to do a trial, or sell the stainless and a know alloy.
Acetone and dry ice, or liquid nitrogen. Plunge the blade into the
liquid for 20-30 seconds, that’ll do it.