What heat treatment boosts 440C stainless steel hardness?

The Hardening Process:

 

Preheat (Optional but Recommended): Slowly bring the steel up to around 760°C - 850°C (1400°F - 1550°F) to prevent thermal shock, especially for larger parts.

 

Austenitize (Hardening Soak): Heat to the critical range, typically 1040°C to 1090°C (1900°F to 2000°F), holding for a short time (e.g., 30 mins for thicker sections) to dissolve carbon into the austenite.

 

Quench: Rapidly cool the steel by quenching in oil or still air, which traps carbon and forms hard martensite.