1, steel annealing
The steel is heated to a certain temperature and incubated for a period of time, and then it was slowly cooled, called annealing. Annealing of the steel is a steel is heated to a phase change or parts of the phase transition temperature, the slow cooling of the heat treatment method after the after insulation. Annealing to eliminate organizational defects, improve tissue composition homogenization and grain refinement to improve the mechanical properties of the steel, to reduce the residual stress; while reducing hardness, improve the ductility and toughness, improve cutting performance. Annealing both prepare for the follow-up process in order to eliminate and improve the organization left over from the preceding process defects and internal stress, therefore annealing is a semi-finished heat treatment, also known as pre-heat treatment.

2, the normalizing of steel
Normalizing the steel is heated to above the critical temperature, all of the steel into a homogeneous austenite, the method of heat treatment and natural cooling in the air. It can eliminate the eutectoid steel mesh cementite sub-eutectoid steel normalizing can the refinement lattice to improve the mechanical properties, less demanding parts with normalizing instead of the annealing process is more economical.

3, the quenching of steel
Quenching the steel is heated to above the critical temperature, and incubated for a period of time, and then quickly into the quenching agent, its temperature is suddenly reduced to greater than the speed of the critical cooling rate of rapid cooling, but mainly to martensite not equilibrium microstructure of the heat treatment method. The quenching can increase the strength and hardness of the steel, but to reduce its plasticity. Quenching in the quenching agent commonly used are: water, oil, alkaline and salts solution.

4, a tempering of the steel
Reheating the quenched steel to a certain temperature, then some method of cooling known as tempering. Its purpose is to eliminate the internal stress generated by the quenching reduces hardness and brittleness, in order to achieve the desired mechanical properties. The tempering points high-temperature tempering, tempering and low temperature tempering three categories. The tempering multi-quenching, normalizing used in conjunction.



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