What is steel normalizing?

1. Definition of normalizing steel

Normalizing is the heat treatment process of heating steel to the appropriate temperature above AC3 or Accm, and then cooling it at a fast speed (air cooling, air cooling or spray) after the complete austenitization of the steel for the appropriate time. The essence of the normalizing process is the complete austenitization plus pseudo eutectoid transformation.

2.The purpose of normalizing

Refine grain, uniform composition, and structure, eliminate internal stress, adjust hardness, eliminate Weidner's structure, ribbon structure, mesh carbide and other defects, for the final heat treatment to provide a suitable tissue state.

3. Application of normalizing

2 Improve the cutting performance of mild steel.

2 Elimination of hot working defects of medium carbon steel (Weisner structure, strip structure, coarse grain).

2 The net carbide of eutectoid steel is eliminated, which is convenient for spheroidizing and annealing, and is ready for quenching.

2 As a final heat treatment, improve the mechanical properties of common structural parts.

4. In order to improve the strength of subeutectoid steel in production, the commonly used method is to increase the content of pearlite in the subeutectoid steel, which heat treatment process should be used?

Answer: The normalizing process should be used.

Reasons: During the cooling process, the hypereutectoid ferrite in subeutectoid steel will be precipitated. The slower the cooling speed is, the more the content of the pro eutectoid ferrite will be, which leads to the decrease of the pearlite content and the decrease of the hardness and strength of the subeutectoid steel. The essence of the normalizing process is complete austenitization and pseudo-eutectoid transformation. By increasing the cooling rate, the content of proeutectoid ferrite can be reduced, and the steel with subeutectoid composition can be transformed into the eutectoid structure, which means the content of pearlite is increased, and the strength and hardness of subeutectoid steel can be improved. 

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