Property of high-alloy steels such as A2, D2, H13 and most high-speed steels, whose hardenability is high enough that cooling from the austenitizing temperature in air or nitrogen forms martensite. Gentle cooling gives the least distortion of any hardening route, which is why these grades suit dies and precision tooling. Heavy sections may still need a pressurized gas quench to cool the core fast enough.
It's A2, it's air hardening, pull it and set it on the rack in front of the fan, no oil.
Also heard as
- air-hardening
- air hard
Related terms
Vacuum furnace
A sealed, pumped-down furnace that heats parts with no atmosphere, then quenches with pressurized gas or oil.
Hardenability
A steel's ability to form martensite to a given depth, set by its chemistry and grain size, not its hardness.
Distortion
Unwanted change in shape or size of a part during heat treatment, such as bowing, warping or ovality.
Secondary hardening
A rise in hardness when certain alloy steels are tempered around 500 to 600 °C, from fine alloy carbides.