Quenching is the heat treatment process applied on metal. Heated the metal to a suitable temperature and hold for a certain time, then immersed in quenching medium and cooled immediately. In general, saline, water, mineral oil, air can be used as quenching medium. Quenching process is widely used in various engineering, mold, measuring tools and requirements of surface wear of parts ( such as gears, rollers, carburizing parts ect.). Because quenching can increase the hardness and wear resistance of metal parts. Quenching process has been widely used in modern machinery manufacturing industry. For those important mechanical parts, especially the metal parts applied on automotive, aircraft, rockets.
Generally, quenching and tempering will be applied together on the metal, by quenching and tempering with different temperatures can greatly improve the strength of the metal, fell toughness and fatigue strength, and to get fit ( mechanical properties) between the performance of these to meet different requirements. Further hardening can also make some special properties of steel to obtain certain physical and chemical properties, such as hardened steel reinforcing its permanent magnet ferromagnetic stainless steel to improve its corrosion resistance.
Quenching process is mainly used for steel parts, when steel heated to above the critical temperature, the original organization of steel turned into austenite ( all or most of). Then the steel will be immersed in water or oil rapidly cooling, and the austenite turned into martensite. Compared with other organizations in steel, martensite has highest hardness. Rapid quenching cooling causes internal stress generated. When it to a certain extent, the steel might be distortion or cracking. Therefore, the right method of cooling is significant.
