Heat-treating 440C with stainless tool wrap
The classic high-carbon stainless — corrosion resistant and wear-tough.
Recommended SSTW grade
Grade 321 stainless foil
440C austenitizes at or below ~2000°F, so 321 stainless foil is the right everyday choice — full scale and decarb protection at a lower cost per roll.
Shop 321 tool wrap rolls440C heat-treat reference
- Austenitizing temp
- 1875–1950°F
- Soak at temp
- 15–30 min
- Quench
- Plate / air, then cryo
- Temper
- 300–400°F, 2× 2 hr
- Typical uses
- Dive knives, hard-use stainless
General knifemaking guidance — always follow the steel manufacturer's published data sheet for your exact stock.
Why wrap 440C in stainless foil
At 1950°F the bare surface of 440C oxidizes and loses carbon (decarburization), leaving a soft, scaled skin you have to grind back past. Sealing the blade in SSTW 321 stainless tool wrap keeps oxygen off the steel through the soak and quench, so it comes out of the kiln bright with full hardness right to the edge — less post-heat-treat grinding, no decarb surprises.
440C foil FAQ
Do I need stainless foil to heat treat 440C?
Wrapping 440C in stainless tool wrap before the kiln prevents surface scale and decarburization, so the blade comes out clean with the carbon at the edge intact. It is strongly recommended for 440C, especially for air- and plate-quenched work where the blade sits at temperature.
Which SSTW grade should I use for 440C — 309 or 321?
440C austenitizes at or below ~2000°F, so 321 stainless foil is the right everyday choice — full scale and decarb protection at a lower cost per roll.
What temperature is 440C heat treated at?
440C is commonly austenitized around 1875–1950°F with a 15–30 min soak, then plate / air, then cryo and tempered (300–400°F, 2× 2 hr). Always confirm against the steel mill's published data sheet for your exact stock — these figures are general knifemaking guidance.
Ready to heat treat 440C clean?
SSTW Grade 321 stainless tool wrap, sold by the roll and shipped from the USA.
Shop tool wrap rolls