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18Cr2Ni4W钢是一种含合金元素较多的渗碳钢,由于淬透性能好,因此在高温缓冷条件下可得到马氏体。渗碳后,当表面含碳量达0.8～1%时,空冷或第二次加热淬火时,均为马氏体及大量残余奥氏体。即使是用一般完全退火的工艺缓慢冷却,也得不到珠光体组织。由于渗碳后冷却下来获得的马氏体针叶比较粗大,残余奥氏体量很多,从而影响了硬度值。此一硬度值如对不再进行金加工的零件来说,表面硬度
18Cr2Ni4W steel is a kind of carburized steel containing more alloying elements. Because of its good hardenability, martensite can be obtained under high temperature and slow cooling conditions. Carburizing, when the surface carbon content of 0.8 to 1%, air cooling or the second quenching, are martensite and a large amount of retained austenite. Pearlescent microstructure can not be obtained even if it is slowly cooled by a generally completely annealed process. As a result of carburizing cooling martensite obtained after relatively coarse, a large amount of retained austenite, thus affecting the hardness value. This value of hardness is no more than the surface hardness of parts that are not machined