[A] low-temperature tempering (150-250 degrees) from the low temperature tempering martensite. Which is aimed at maintaining the hardened steel of high hardness and high wear resistance under the premise of reducing its quenching stress and brittleness, in order to avoid the use cracked or damaged prematurely. It is mainly used for a variety of high-carbon cutting tools, measuring tools, GB/T9711.1 line pipe, Rolling and carburizing, tempering hardness is generally HRC58-64. [B] tempering (250-500 degrees) in tempering the resulting organization as tempered troostite. Its purpose is to obtain a high yield strength, elastic limit, and high toughness. Therefore, it is mainly used for the various GB/T9711.1 Pipes and hot mold processing, tempering hardness is generally HRC35-50. [Three] high-temperature tempering (500-650 degrees) high-temperature tempering proceeds organizations as the tempering Sorbite. Will be used quenching and tempering heat treatment combination known as quenching, its purpose is to obtain better mechanical properties of strength, hardness and ductility, toughness. Therefore, it is widely used in automotive, GB/T9711.1 line pipe, machine tools and other important structural parts, such as rods, bolts, gears and shafts. Tempered hardness of HB200-330.