Main application scope of normalizing of heat treatment process

The main applications of normalizing are:

① For low carbon steel, the hardness after normalizing is slightly higher than that after annealing, and the toughness is also good. It can be used as the pretreatment of cutting.

② For medium carbon steel, it can replace quenching and tempering treatment as heat treatment, and can also be used as preparation treatment before surface quenching by induction heating method.

③ It is used for tool steel, bearing steel, carburizing steel, etc. it can reduce or inhibit the formation of network carbide, so as to obtain the good structure required for spheroidizing annealing.

④ For steel castings, it can refine as cast microstructure and improve machinability.

⑤ It can be used as heat treatment for large forgings to avoid large cracking tendency during quenching.

⑥ It is used for nodular cast iron to improve hardness, strength and wear resistance, such as crankshaft, connecting rod and other important parts of automobile, tractor and diesel engine.

⑦ One normalizing before spheroidizing annealing of hypereutectoid steel can eliminate the network secondary cementite, so as to ensure that all cementite is spheroidized during spheroidizing annealing.

The difference between normalizing and annealing is that normalizing cooling speed is slightly faster than annealing cooling speed, so normalizing structure is finer than annealing structure, and its mechanical properties are also improved. In addition, the cooling outside the normalizing furnace does not occupy equipment and has high productivity. Therefore, normalizing should be used instead of annealing as much as possible in production.