Normalizing

Normalizing is the heat treatment method that the steel is heated to Ac3 (total analysis of steel) or Accm- (hypereutectoid steel) above 30-50 ℃ for a period of time, and then cooling in the air or in forced air to room temperature. Normalizing is faster than annealing and cooling, so the normalizing structure is thinner than the annealing structure and the strength and hardness are higher than the annealing structure. Due to the short production cycle of normalizing, equipment utilization and production efficiency, low cost, and therefore widely used in production. The purpose of normalizing is as follows:

(1) Improved machinability : Normalizing improves the machinability of mild steel (with a mass fraction of less than 0.25%). Carbon mass fraction of carbon steel below 0. 25%, hardness is too low after annealing, it is easy to "stick knife" while cutting, the surface finish is poor. By normalizing the hardness can be increased to near the best condition for cutting hardness, thereby improving the machining performance.

(2) As a pre-heat treatment : Large cross-section structural steels often normalize to eliminate Widmanstatten and banded structures before quench or quenching (quenching and high temperature tempering) , and to obtain uniform fine tissue. For carbon mass fraction greater than 0.77% of the carbon steel and alloy tool steel reticular cementite exists, normalizing can reduce the amount of secondary cementite, and make it not to form a continuous network for good tissue preparation of the ball annealing

) As the final heat treatment : The less demanding on the strength for parts can be normalized as the final heat treatment. Normalizing fine particles, uniform organization, thereby enhancing the strength, hardness and toughness of steel.