A2 heat treat: austenitize, quench & temper chart
A2 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 A2 heat-treat schedule
Austenitize: 1725–1800°F (1775°F recommended), hold 20 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. A2 is air-hardening. Plate quench is preferred for thin stock; forced air works for thicker sections.
Cryo (recommended): LN₂ for 30–60 min. A2 has elevated retained austenite without cold treatment. Straight from the quench into cryo, then temper.
Temper: 2 passes of 2 h at 400°F for the recommended edge (~61–62 HRC). Temper twice for 2 hours. A2 tolerates 500–600°F without tempered martensite embrittlement.
A2 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) | 63–64 HRC |
| 400°F (204°C) | 61–62 HRC |
| 500°F (260°C) | 60 HRC |
| 600°F (316°C) | 59–60 HRC |
Target hardness for A2 by knife type
| Use | Recommended HRC |
|---|---|
| Kitchen | 62–63 HRC |
| EDC | 61–62 HRC |
| Hunter | 60–61 HRC |
| Hard-use chopper | 59–60 HRC |
Most common mistake
Forgiving steel — but cryo is non-optional for retained-austenite control at 60+ HRC.
FAQ
What temperature do you austenitize A2?
1725–1800°F, with 1775°F recommended, held 20 min once the steel is fully up to temperature.
What is the best quench for A2?
Plate quench. Forced air also work. Never Water, Brine, Parks 50, Duratherm 48, Parks AAA, Canola oil. A2 is air-hardening. Plate quench is preferred for thin stock; forced air works for thicker sections.
What HRC does A2 reach?
59–64 HRC across the usable tempering range; about 62–63 HRC for a kitchen knife. Temper at 400°F for ~61–62 HRC.
How do you temper A2?
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 A2?
A2 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 A2
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 1775°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 A2; 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.