Heat-treating CPM-S35VN with stainless tool wrap
S30V refined with niobium — tougher and easier to finish.
Recommended SSTW grade
Grade 309 stainless foil
CPM-S35VN austenitizes around 2050°F — above ~2000°F — so 309 stainless foil holds up to the heat and longer soaks without embrittling.
Shop 309 tool wrap rollsCPM-S35VN heat-treat reference
- Austenitizing temp
- 1950–2050°F
- Soak at temp
- 15–30 min
- Quench
- Plate quench, then cryo
- Temper
- Per Crucible spec
- Typical uses
- Premium folders, fixed blades
General knifemaking guidance — always follow the steel manufacturer's published data sheet for your exact stock.
Why wrap CPM-S35VN in stainless foil
At 2050°F the bare surface of CPM-S35VN oxidizes and loses carbon (decarburization), leaving a soft, scaled skin you have to grind back past. Sealing the blade in SSTW 309 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.
CPM-S35VN foil FAQ
Do I need stainless foil to heat treat CPM-S35VN?
Wrapping CPM-S35VN 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 CPM-S35VN, especially for air- and plate-quenched work where the blade sits at temperature.
Which SSTW grade should I use for CPM-S35VN — 309 or 321?
CPM-S35VN austenitizes around 2050°F — above ~2000°F — so 309 stainless foil holds up to the heat and longer soaks without embrittling.
What temperature is CPM-S35VN heat treated at?
CPM-S35VN is commonly austenitized around 1950–2050°F with a 15–30 min soak, then plate quench, then cryo and tempered (Per Crucible spec). Always confirm against the steel mill's published data sheet for your exact stock — these figures are general knifemaking guidance.
Can I use 321 foil for CPM-S35VN?
321 works for many sub-2000°F heat treats, but CPM-S35VN runs hot enough that 309 stainless foil is the safer choice — it tolerates the higher austenitizing temperature and longer soaks without embrittling.
Ready to heat treat CPM-S35VN clean?
SSTW Grade 309 stainless tool wrap, sold by the roll and shipped from the USA.
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