Introduction of heat treatment of steel

Introduction of heat treatment of steel

1, steel annealing

The steel is heated to a certain temperature and heat preservation for a period of time, and then make it slowly cooling, called annealing. Steel annealing is a heat the steel to the phase change or part of the phase change temperature, slow cooling after heat preservation heat treatment method. The purpose of annealing is to eliminate tissue defects, improve the organization make composition uniformity and fine grains, increase mechanical properties of the steel, reduce residual stress; Can decrease the hardness at the same time, improve the plasticity and toughness, improve machinability. So before annealing in order to eliminate and improve both the legacy of tissue defects and internal stress, and to prepare for the follow-up process, so the annealing is belong to the intermediate heat treatment, also called heat treatment in advance.

2, steel normalizing

Normalizing is heated to above the critical temperature of steel, to all into homogeneous austenitic steel, heat treatment and natural cooling in air. It can eliminate hypereutectoid steel mesh cementite, for hyposteel normalizing can refine crystal lattice, improve comprehensive mechanical properties, low requirements for the parts use the normalized instead of the annealing process is more economic.

3, steel quenching

Quenching is the steel is heated to above the critical temperature, heat preservation for a period of time, then quickly into the quenching medium, the temperature plummeted, rapid cooling at greater than the critical cooling rate of speed, which is mainly composed of martensite and unbalanced heat treatment method of the organization. Can increase strength and hardness of the steel quenching, but to reduce its plasticity. That is commonly used in quenching hardening agent are: water, oil, caustic soda, and salt solution, etc.

4, the steel tempering

Will have been reheated quenching of steel to a certain temperature, cooling with a certain method called tempering. Its purpose is to eliminate the quenching of internal stress, reduce the hardness and brittleness, in order to obtain the desired mechanical properties. Tempering points and high temperature tempering, the tempering temperature and low temperature tempering. Tempering and hardening, normalizing, cooperate to use.