QuenchInterrupted oil / air / salt bath — cool below 150°F, temper immediately
Cryo / sub-zeroOptional — optional — not specified in the Crucible datasheet
Temper3× 2 h · cool to room temp between cycles (triple temper required)
Reliable hardness60–65 HRC
PM high-speed steel — competition-cutter favorite for extreme edge retention at 62–65 HRC. Like CPM-3V this is a HIGH-temper steel (~1000–1050°F × 3), not a low-temper one. Preheat 1500–1550°F, then heat rapidly to hardening temperature; low side of the range gives better toughness for blades.
⚠︎ Datasheet hardness table is salt-bath austenitized (2 min) + oil quench; furnace/foil heat treat may run 1–2 HRC lower — verify on your setup.
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
1000°F
538°C
64.5 HRC
1025°F
552°C
64 HRC
1050°F
566°C
63 HRC
1075°F
579°C
62 HRC
1100°F
593°C
60 HRC
Composition (typical, wt%)
Element
%
C
1.3%
Cr
4.3%
V
4%
Mo
4.5%
W
5.6%
Mn
0.3%
Si
0.3%
Niagara / Crucible CPM REX M4 datasheet
HeatTreatBench — the recipes in your shop, offline
Get the full CPM-M4 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.