The heat treatment of fasteners is a comprehensive process that puts the material in a certain medium for heating, heat preservation and cooling, and controls its performance by changing the surface or internal structure of the material.
The main purpose of heat treatment of fasteners is to obtain good comprehensive mechanical properties of the workpiece through quenching and tempering (quenching + high temperature tempering).
Annealing is to heat the workpiece to an appropriate temperature, adopt different holding times according to the material and the size of the workpiece, and then slowly cool it. The purpose is to make the internal structure of the metal reach or approach the equilibrium state, to obtain good process performance and use performance, or to further quench Prepare for organization.
Normalizing is to heat the workpiece to a suitable temperature and cool it in the air. The effect of normalizing is similar to that of annealing, but the resulting structure is finer. It is often used to improve the cutting performance of the material, and it is sometimes used for some less demanding parts. As the final heat treatment.
Quenching is rapid cooling in water, oil or other inorganic salts, organic aqueous solutions and other quenching media after heating and holding the workpiece. After quenching, the steel becomes hard, but at the same time becomes brittle.
Tempering is to reduce the brittleness of steel parts. The quenched steel parts are kept at a suitable temperature higher than room temperature but lower than 650 ° C for a long time and then cooled. This process is called tempering.
Annealing, normalizing, quenching, and tempering are the "four fires" in the overall heat treatment. The quenching and tempering are closely related and are often used in conjunction with each other.
