S35VN heat treat: austenitize, quench & temper chart
S35VN is a stainless knife steel. Here is the full heat-treat schedule — austenitizing temperature, quench, cryo and a tempering-temperature chart mapping each temper to final HRC — with every number cited to the source, not guessed.
The S35VN heat-treat schedule
Austenitize: 1950–2050°F (2025°F recommended), hold 15 min once to temperature. A controlled oven or kiln beats forge colour for hitting this window repeatably.
Quench: Plate quench. Never use Water, Brine, Parks 50, Duratherm 48, Parks AAA, Canola oil. Plate quench between aluminum plates.
Cryo (recommended): LN₂ for at least 30 minutes. Straight from the quench into cryo, then temper.
Temper: 2 passes of 2 h at 400°F for the recommended edge (~60–61 HRC). Temper twice for 2 hours. Higher austenitize temp (2025°F vs datasheet 1950°F) gives both hardness and toughness gains.
S35VN tempering-temperature chart
Two-hour temper (×2), HRC after cryo where used. Pick the tempering temperature for the hardness your knife needs:
| Tempering temperature | Resulting hardness |
|---|---|
| 300°F (149°C) | 61–62 HRC |
| 350°F (177°C) | 61–62 HRC |
| 400°F (204°C) | 60–61 HRC |
Target hardness for S35VN by knife type
| Use | Recommended HRC |
|---|---|
| Kitchen | 61–62 HRC |
| EDC | 60–61 HRC |
| Hunter | 60–61 HRC |
| Hard-use chopper | 60 HRC |
Most common mistake
Datasheet specifies 1950°F austenitize — Larrin's testing shows 2025°F is better. Use 2025°F unless your kiln tops out.
FAQ
What temperature do you austenitize S35VN?
1950–2050°F, with 2025°F recommended, held 15 min once the steel is fully up to temperature.
What is the best quench for S35VN?
Plate quench. Never Water, Brine, Parks 50, Duratherm 48, Parks AAA, Canola oil. Plate quench between aluminum plates.
What HRC does S35VN reach?
60–62 HRC across the usable tempering range; about 61–62 HRC for a kitchen knife. Temper at 400°F for ~60–61 HRC.
How do you temper S35VN?
2 passes of 2 h at 400°F for the recommended edge. See the chart above to pick a different tempering temperature for a harder or tougher blade.
Can you forge S35VN?
S35VN is best heat-treated in a controlled oven or kiln rather than forged by colour — its austenitizing window and quench are too tight to hit reliably by eye.
What you need to heat-treat S35VN
Repeatable hardness comes from controlling temperature and quench speed — eyeballing colour is how blades end up soft or cracked.
- A heat-treat oven or kiln holds the 2025°F austenitizing temperature — the single biggest factor in repeatable hardness.
- Air-hardening steel plate-quenches between aluminium quench plates — no oil bath needed.
- Verify the result with a Rockwell hardness tester or hardness files — don't trust the schedule blind.
- Wrap in stainless tool-wrap foil to stop decarb and scale at high austenitizing temperatures.
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Sources
Heat-treat schedules are the cited published values for S35VN; every furnace, quench and blade geometry varies, so verify against your own hardness testing. Getting steel to non-magnetic is not the same as reaching austenitizing temperature — use a controlled oven or kiln for repeatable results.