What is heat treatment ?

Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other machining processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but change the microstructure inside the workpiece or changing the chemical composition of the surface of the workpiece to give or improve the performance of the workpiece. Its characteristic is to improve the internal quality of the workpiece, which is generally not visible to the naked eye. As some people say, machining is surgery, and heat treatment is internal medicine, representing the core competitiveness of a country's manufacturing industry.

The heat treatment process generally includes three processes of heating, heat preservation, and cooling, and sometimes there are only two processes of heating and cooling. These processes are connected and uninterrupted.

When the metal is heated, the workpiece is exposed to the air, and oxidation and decarburization often occur (that is, the carbon content of the surface of the steel part is reduced), which has a very adverse effect on the surface performance of the parts after heat treatment. Therefore, metals should usually be heated in a controlled atmosphere or protective atmosphere, molten salt atmosphere, and vacuum atmosphere, and coatings or packaging methods can also be used for protection and heating.