The purpose of quenching is to transform the supercooled austenite into martensite or bainite, obtain martensite or bainite structure, and then mix with tempering at different temperatures to greatly improve the rigidity, hardness and wear resistance of the steel. Sex, fatigue strength and toughness to meet the different requirements of various mechanical parts and tools. Special physical and chemical properties such as ferromagnetism and corrosion resistance of certain special steels can also be met by quenching.
The quenching process is widely used in the modern machinery manufacturing industry. Important parts in machinery, especially those used in automobiles, airplanes, and rockets, are almost quenched. In order to meet the technical requirements of various parts, various quenching processes have been developed. For example, according to the parts to be treated, there are integral, local quenching and surface quenching; whether the phase transformation is complete according to heating, complete quenching and incomplete quenching (for hypoeutectic steel, the method is also called subcritical quenching); The contents of the phase change include fractional quenching, austempering and underspeed quenching.