Normalizing and spheroidizing in heat treatment of precision parts
For precision parts processing, normalizing treatment includes heating the steel to 50 ℃～ 100 ℃ (10 ℃～ 40 ℃) higher than the upper critical zone, and then cooling it to room temperature in still air. Annealing is mainly used for low carbon steel, medium carbon steel and alloy steel to make the grain structure more uniform, release the internal stress or obtain the required physical properties. Most commercial steels are annealed after rolling or casting.
Spheroidization is a process to produce cementite with a spherical distribution structure. If the steel is slowly heated to just below the critical temperature and kept for a long time, this kind of structure can be obtained. The obtained spherical structure improves the machinability of the steel. This treatment is particularly useful for hypereutectoid steels that must be machined.