The supercold austenite undergoes martensite or bainite transformation, obtain martensite or bainite tissue, and then cooperate with tempering at different temperatures to greatly improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel, so as to meet the different requirements of various mechanical parts and tools. The ferromagnetic and corrosion resistance of some special steels can also be met through quenching.
The metal workpiece is heated to an appropriate temperature and maintained for a period of time, and then immersed in the quenching medium to quickly cool the metal heat treatment process. Commonly used quenching media include brine, water, mineral oil, air, etc. Quenching can improve the hardness and wear resistance of metal workpieces, so it is widely used in various workpieces, molds, measuring tools and parts that require surface wear resistance (such as gears, rollers, carburizing parts, etc.). Through quenching and tempering at different temperatures, the strength, toughness and fatigue strength of metals can be greatly improved, and the matching between these properties (comprehensive mechanical properties) can be obtained to meet different use requirements.
In addition, quenching can also enable some special properties of steel to obtain certain physical and chemical properties, such as quenching to enhance the ferromagneticity of permanent magnet steel and stainless steel to improve its corrosion resistance. The quenching process is mainly used for steel parts. When the commonly used steel is heated above the critical temperature, the original tissue at room temperature will be completely or mostly converted into austenite. The steel is then immersed in water or oil to cool quickly, and the austenite is converted into martensite. Compared with other tissues in steel, martensitic hardness is the highest. Rapid cooling during quenching will cause internal stress inside the workpiece. When it is large to a certain extent, the workpiece will be twisted, deformed or even cracked. To this end, the appropriate cooling method must be selected. According to the cooling method, the quenching process is divided into four categories: single liquid quenching, double medium quenching, martensite graded quenching and bainite isothermal quenching.
