Steel quenching is to heat the steel to the critical temperature Ac3 (eutectoid) or Ac1 (over eutectoid) a certain temperature, heat preservation for a period of time, so that all or part of the austenite, and then with a greater than the critical cooling rate of cold fast to MS (or Ms near the isothermal) to the martensite (or bainite) transformation of heat treatment process.

It is also commonly referred to as quenching by solid solution treatment of aluminum alloy, copper alloy, titanium alloy, tempered glass and other materials, or heat treatment process with rapid cooling process.