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 the different purposes of heat treatment, the heat treatment process can be divided into two categories: preliminary heat treatment and final heat treatment.The purpose of the preliminary heat treatment is to improve the processability, eliminate the internal stress, and prepare a good metallographic structure for the final heat treatment. The main purpose of the preliminary heat treatment is to provide the ideal original structure for the final heat treatment, to ensure the performance indexes of the final heat treatment of the parts, and to provide suitable hardness for the machining and to ensure the machining accuracy of the parts. The heat treatment process includes annealing, normalizing, aging, quenching and tempering.
For example: annealing and normalizing, the purpose is to improve the cutting performance, eliminate the internal stress of the blank, refine the grain, and evenly organize; prepare for the heat treatment in the future. For example: carbon steel and alloy steel with carbon content greater than 0.7%, for the reduction of hardness, easy to use for annealing, low carbon steel and low alloy steel with carbon content less than 0.3%, in order to avoid excessive hardness when cutting And use normalizing to properly increase the hardness.
Final heat treatment
The purpose of the final heat treatment is to improve mechanical properties such as hardness, wear resistance and strength. Generally speaking, the final heat treatment is the final heat treatment to obtain the final properties required for the part. The final meaning is that no heat treatment is required, which is the last time.
How to distinguish
Whether it is annealing, normalizing, quenching + tempering, it is mainly to see what its purpose is. Preparing for other processes is to prepare heat treatment. In order to obtain the final performance, it is the final heat treatment. This is the judgment principle.