QuenchPlate quench / forced air or gas — quench quickly, cool to ~85°F, temper immediately
Cryo / sub-zeroOptional — Böhler: deep-freeze -112°F for 2 h right after quench for retained-austenite conversion; makers use dry ice or LN2
Temper2× 2 h · cool to room temp between cycles
Reliable hardness59–62 HRC
Böhler PM stainless (= 20CV / 204P) — excellent corrosion resistance and edge retention. Böhler: harden 2010–2100°F / 20–30 min; low temper 390–570°F (once, ≥2 h) for max corrosion resistance. KSN: hardness peaks at 2100°F with cryo; above ~2150°F retained austenite drops hardness — don't chase it. Same recipe applies to CPM 20CV and CTS-204P.
⚠︎ Temper↔HRC points are approximate (Böhler tempering diagram + maker reports) — verify with supplier datasheet.
Temper → hardness chart
Approximate HRC after a double-temper at each temperature (from the sources below). Set your target and pick the matching temper.
Temper °F
Temper °C
Hardness
300°F
149°C
62 HRC
350°F
177°C
61.5 HRC
400°F
204°C
61 HRC
500°F
260°C
60 HRC
Composition (typical, wt%)
Element
%
C
1.9%
Cr
20%
V
4%
Mo
1%
W
0.6%
Mn
0.3%
Si
0.7%
Böhler M390 Microclean datasheet
HeatTreatBench — the recipes in your shop, offline
Get the full M390 recipe plus 25 more steels offline — set your target HRC and the app gives you the exact temper, with a forge timer and a per-blade log. Works in the shop with no signal.