In order to make metal workpieces have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often essential. Iron and steel are 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, and their alloys can also be used to change their mechanical, physical, and chemical properties through heat treatment to obtain different performance properties.
Heat treatment generally does not change the shape of the workpiece and the overall chemical composition, but imparts or improves the performance of the CNC machining spare parts by changing the microstructure inside the workpiece or changing the chemical composition on the surface of the workpiece. Its characteristic is to improve the intrinsic quality of the workpiece, which is generally not visible to the naked eye.
The role of heat treatment is to improve the mechanical properties of the material, eliminate residual stress and improve the machinability of the metal. According to different purposes of heat treatment, heat treatment processes can be divided into two categories: preliminary heat treatment and final heat treatment.
The purpose of preliminary heat treatment is to improve processability, eliminate internal stress and prepare a good metallographic structure for final heat treatment. The heat treatment processes include annealing, normalizing, aging, and quenching and tempering.
Annealing and normalizing are used for hot-worked blanks. Carbon steels and alloy steels with a carbon content of more than 0.5% are often annealed in order to reduce their hardness and are easy to cut; carbon steels and alloy steels with a carbon content of less than 0.5% are to avoid sticking the knife during cutting. Instead, use normalizing treatment. Annealing and normalizing can still refine the grain and uniform structure, and prepare for subsequent heat treatment. Annealing and normalizing are usually arranged after the blank is manufactured and before roughing.
Aging treatment is mainly used to eliminate the internal stress generated during blank manufacturing and machining. In order to avoid excessive transportation workload, it is enough to arrange an aging treatment before finishing for general precision parts. However, parts with high accuracy requirements (such as the box body of a coordinate boring machine, etc.) should be arranged for two or more aging treatment procedures. Simple parts generally do not need aging treatment.
Quenching and tempering is a high temperature tempering treatment after quenching. It can obtain a uniform and fine tempered sorbate structure, and prepare for reducing deformation during subsequent surface quenching and nitriding treatment. Therefore, quenching and tempering can also be used as preliminary heat treatment. Because the comprehensive mechanical properties of the quenched and tempered parts are better, some parts that do not require high hardness and wear resistance can also be used as the final heat treatment process in customized plastic injection molding.