QuenchOil quench or air cool (datasheet); plate quench is the common maker route for blades
Cryo / sub-zeroOptional — maker practice: dry ice / LN2 to convert retained austenite (datasheet table is WITHOUT cold treatment)
Temper2× 2 h · cool to room temp between cycles
Reliable hardness54–59 HRC
The classic high-carbon stainless. Datasheet: harden 1850–1900°F (preheat 1425°F for complex parts), oil or air quench; temper table is without cold treatment — adding cryo typically gains 1–2 HRC. Avoid tempering 800–1100°F (impact strength and corrosion resistance both drop).
⚠︎ Datasheet gives no hold time at hardening temperature; 15–30 min at temperature is common practice — verify with your steel supplier.
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
212°F
100°C
59 HRC
400°F
204°C
56 HRC
600°F
316°C
54 HRC
Composition (typical, wt%)
Element
%
C
1.07%
Cr
17%
Mo
0.75%
Mn
1%
Si
1%
Niagara 440C datasheet (ranges C 0.95–1.20, Cr 16–18; mid-points shown)
HeatTreatBench — the recipes in your shop, offline
Get the full 440C 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.