These characteristics include strength, hardness, and ductility, which all contribute to the machinability of the material. Heat treat is a group of processes of heating and cooling material to give it certain physical characteristics. Some procedures are applied to the material and some are applied to the parts, after machining. All of these processes are controlled by the chemical composition of the material, temperature and the rate of heating and cooling. Heating Prior to heat treating, steel is considered soft.
Heat is applied to such high temperatures that the atomic structure of the material is altered.
The maximum temperature and the cooling method alter the material to a more desired state. The temperature at which steel properties change depends on the specific chemical content. The critical point is the temperature above which the material will harden when quickly cooled. For most steel, the critical point is between 1200 and 1800 F. Fast Cooling When the steel is heated to these high temperatures, it must be cooled so the steel is left with the desired physical properties. Quick cooling, or quenching, is done in a number of environments, including air, water, oil, sand and chemical baths.