Metal heat treatment processes can generally be divided into three categories: overall heat treatment, surface heat treatment, and chemical heat treatment. Depending on the heating medium, heating temperature, and cooling method, each category can be divided into several different heat treatment processes. Using different heat treatment processes for the same metal can obtain different microstructures and thus have different properties. Steel is the most widely used metal in industry, and its microstructure is also the most complex. Therefore, there are various types of steel heat treatment processes. Integral heat treatment is a metal heat treatment process that heats the workpiece as a whole and then cools it at an appropriate rate to obtain the required metallographic structure to change its overall mechanical properties. There are four basic processes for the overall heat treatment of steel: annealing, normalizing, quenching, and tempering.