Accreditation Administration System:
Normalizing is to heat the steel plate to Ac3 (Ac means the final temperature of all free ferrite transformed into austenite during heating, usually from 727 to 912 degrees Celsius). After holding the above 30~50 C for a period of time, the metal heat treatment process is taken out from the furnace in air or by spray, spray or blow cooling. The aim is to refine the grains and homogenize the carbide distribution.
The difference between normalizing and annealing is that the cooling rate of normalizing is slightly faster than that of annealing, so the microstructure of normalizing is finer than that of annealing, and its mechanical properties are also improved. In addition, the cooling outside the normalizing furnace does not occupy the equipment, so the productivity is high, so normalizing should be used instead of annealing in production as much as possible. For the important forgings with complex shape, high temperature tempering (550-650 ¡æ) is needed after normalizing. The purpose of high temperature tempering is to eliminate the stress produced during normalizing cooling and improve the toughness and plasticity.
Other applications of normalizing are:
¢Ù For low carbon steel, the hardness after normalizing is slightly higher than that after annealing, and the toughness is also better, so it can be used as the pretreatment of cutting.
¢Ú For medium carbon steel, it can replace quenching and tempering as the final heat treatment
¢Û It can be used in tool steel, bearing steel, carburizing steel, etc. to reduce or inhibit the formation of network carbide, so as to obtain the good structure for spheroidizing annealing.
¢Ü It is used to improve the cutting performance of steel castings.
¢Ý It can be used as the final heat treatment for large forgings, so as to avoid large cracking tendency during quenching.
¢Þ It is used in nodular cast iron to improve hardness, strength and wear resistance
