D2 heat treat: austenitize, quench & temper chart
D2 is a spring / tool 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 D2 heat-treat schedule
Austenitize: 1850–1900°F (1875°F recommended), hold 30 min once to temperature. A controlled oven or kiln beats forge colour for hitting this window repeatably.
Quench: Plate quench. Also acceptable: Forced air. Never use Water, Brine, Parks 50, Duratherm 48, Parks AAA, Canola oil. Plate quench maintains flatness with adequate cooling rate. Air-hardening.
Cryo (recommended): LN₂ or dry ice 30–60 min. D2 has high retained austenite without cold treatment. Straight from the quench into cryo, then temper.
Temper: 2 passes of 2 h at 450°F for the recommended edge (~60–61 HRC). Temper twice for 2 hours. Standard 1850–1875°F + 400–500°F gives 60–62 HRC.
D2 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) | 64 HRC |
| 400°F (204°C) | 61–62 HRC |
| 450°F (232°C) | 60–61 HRC |
| 500°F (260°C) | 60 HRC |
Target hardness for D2 by knife type
| Use | Recommended HRC |
|---|---|
| Kitchen | 61–62 HRC |
| EDC | 61–62 HRC |
| Hunter | 60–61 HRC |
| Hard-use chopper | 60–61 HRC |
Most common mistake
Conventional D2 has large carbides — PM versions (CPM-D2, PSF27) refine the structure for better edge stability.
FAQ
What temperature do you austenitize D2?
1850–1900°F, with 1875°F recommended, held 30 min once the steel is fully up to temperature.
What is the best quench for D2?
Plate quench. Forced air also work. Never Water, Brine, Parks 50, Duratherm 48, Parks AAA, Canola oil. Plate quench maintains flatness with adequate cooling rate. Air-hardening.
What HRC does D2 reach?
60–64 HRC across the usable tempering range; about 61–62 HRC for a kitchen knife. Temper at 450°F for ~60–61 HRC.
How do you temper D2?
2 passes of 2 h at 450°F for the recommended edge. See the chart above to pick a different tempering temperature for a harder or tougher blade.
Can you forge D2?
D2 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 D2
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 1875°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.
Some links above are affiliate links — if you buy through them, Moon Dog may earn a small commission at no extra cost to you. We only point to gear we'd actually use.
Sources
Heat-treat schedules are the cited published values for D2; 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.