Metal heat treatment is to heat a metal or alloy workpiece to a suitable temperature in a certain medium, and after maintaining this temperature for a certain period of time, it is cooled in different media at different speeds, by changing the surface or interior of the metal material. A process in which the microstructure is used to control its properties.

Metal heat treatment is one of the important processes in machinery manufacturing. Compared with other processing technologies, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but changes the microstructure inside the workpiece or changes the chemical composition of the workpiece surface. , to give or improve the performance of the workpiece. It is characterized by improving the intrinsic quality of the workpiece, which is generally not visible to the naked eye. Therefore, it is a special process in machinery manufacturing and an important link in quality management.  

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