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过热过热往往引起零件淬裂,所谓过热即晶粒长大,显微组织粗化,使组织应力和热应力显著增加。由于零件过热使材料的冲击韧性显著下降,使用寿命大大缩短,特别是零件在受冲击负荷时尤为显著。高速钢在碳化物偏析较严重呈大块状分布时,易使零件在热处理时过热(图31),使刀具在用时易崩刃和折断。碳化物呈大块状 200X 众所周知.随着淬火加热温度的升高或保温时间的延长.钢的奥氏体晶粒长大.故金相方法是检验零件是否过热的最有效方法. 淬火过热便马氏体的针叶粗大.根据
Overheating and overheating often cause quenching and tearing parts, the so-called overheating that grain growth, coarsening of the microstructure, the organizational stress and thermal stress increased significantly. As the parts overheat material impact toughness decreased significantly, the service life is greatly reduced, especially when the parts are particularly affected by the impact load. High-speed steel in the more serious segregation of carbides were large-scale distribution, easy to make the parts overheated in the heat treatment (Figure 31), the tool is easy to collapse when used and broken. Carbide was massive 200X is well known.With the quenching heating temperature or holding time extension of the steel austenite grain growth.Therefore, the metallographic method is to test whether the parts overheating the most effective way. Martensite needle thick. According to