Heat treatment is to point to metal materials under solid state, by means of heating, heat preservation and cooling, changing the chemical composition of material surface or internal and organization, to obtain the required properties of a metal hot working process. Heat treatment is one of the important processes in the manufacturing process of mechanical parts and tooling. Heat treatment process generally consists of three processes: heating, heat preservation and cooling, sometimes only heating and cooling.

Metal heat treatment is one of the important technology in mechanical manufacturing, compared with other processing technology, heat treatment generally does not change the shape of the workpiece and the chemical composition of the whole, but by changing the workpiece internal microstructure, or change the surface chemical composition, or improve the use performance of workpiece. The characteristic is to improve the internal quality of the workpiece, which is not normally visible to the naked eye.

In order to make the metal workpiece have the mechanical properties, physical properties and chemical properties required, the heat treatment process is often indispensable in addition to the reasonable selection of materials and various forming processes. Steel is the most widely used material in the mechanical industry, and the steel microstructure is complex and can be controlled through heat treatment, so the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium and other alloys can also change their mechanical, physical and chemical properties through heat treatment to achieve different performance.