Normalizing, also known as open fire, code Z, is to heat the steel piece to Ac3 or Acm above (30 ~ 50 ℃), hold for a period of time, and then cooled in the air, the cooling rate is slightly faster than annealing.

The main difference between bearing annealing and normalizing is: normalizing is a perversion or special case of complete annealing, the two are only different cooling speeds, usually annealing is cold with the furnace and normalizing is cooled in the air, normalizing is applicable to both sub-eutectic steel is also suitable for over-eutectic steel, for the eutectic steel, normalizing is generally used for the elimination of reticulation carbides; for sub-eutectic steel, normalizing the purpose of annealing and annealing is basically the same, is mainly to refine the grain, eliminate the Defects in the organization, but normalizing the organization of pearlite pieces of finer than the annealed, and sub-eutectic steel pearlite number of ferrite number of less, therefore, by normalizing the steel hardness, strength are higher than the annealed steel, it can be seen that, in production practice, the steel has a reticulated carbide materials need to be eliminated by the normalizing process can be used before the use of other processes, and heat treatment of the material after the performance requirements, according to the requirements of the different and the steel type of different Select annealing process, such as: require a certain degree of strength and hardness after heat treatment, you can choose the normalizing process; require a certain degree of plasticity, try to reduce the strength and hardness should be selected annealing process.

Bearing production on the common types of annealing operations

(1) complete annealing (commonly known as annealing) is mainly used for sub-common-bridge steel and alloy steel castings, forgings and hot-rolled profiles, and some are also used as welded structural parts, the purpose is to refine the grain, improve the organization, eliminate residual stress, reduce hardness, improve plasticity, improve the performance of the cutting and machining, complete annealing is a very long annealing process, in order to shorten the time of the annealing process is often used to replace the process of isothermal fire! Complete annealing process, with complete annealing comparison, isothermal fire purpose and complete annealing the same, but it greatly reduces the annealing time.

(2) spheroidal annealing is mainly used for over eutectic steel and alloy tool steel (such as cutting tools, gauges, molds and bearings, and all other steel). Its purpose is mainly to reduce the hardness, improve the machinability, and prepare for the future quenching.

(3) stress relief annealing (also known as low-temperature annealing) is mainly used to eliminate castings, forgings and weldments, hot rolled parts and other internal stress.

(4) recrystallization annealing is used to eliminate cold working (cold drawing, cold punching, cold rolling, etc.) produced by work hardening. The purpose is to eliminate internal stresses, improve plasticity, improve organization.

(5) diffusion annealing is mainly used for alloy steel, especially alloy steel castings and ingots. The purpose is to use high temperature atoms have a greater ability to diffuse to reduce or eliminate the phenomenon of uneven chemical composition in steel.