In order to study the influence of high-temperature tempering process on the microstructure of heavy-duty gears in coal mining machines,the volume fraction changes of the microstructure after high-temperature tempering were obtained through experiments.The variation rule of retained austenite content with process temperature and process times after high-temperature tempering was also studied.The results show that with the increase of high-temperature tempering times,the content of retained austenite in the surface layer and transition layer decreases,and the surface carbon concentration also decreases.With the increase of high-temperature tempering temperature,carbides precipitate at grain boundaries,which has a negative impact on performance.Finally,a method of tempering at 650℃for 2 times is selected as the tempering process after carburizing.
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