Effect of preheating treatment before carburizing on distortion of 17CrNiMo6 steel gear shaft

The traditional carburizing process is to directly heat the workpiece to the carburizing temperature during carburizing. In this paper, the gear shaft is preheated for a period of time before carburizing. The gear shaft is carburized and quenched according to the two pretreatment methods in the table, and the diameter jump is used to characterize the distortion of the gear shaft. The test results show that preheating before carburizing is beneficial to control the heat treatment distortion of gear shaft, and also verify the correctness of the numerical simulation results.

Test numberCarburizing temperature / ℃Whether to preheatPreheating temperature / ℃Holding time / hRadial jump / mm
1930No30.58 ~ 0.69
2930Yes40030.31 ~ 0.47

1) During the carburizing heating process of gear shaft, the change of internal and external temperature makes it form a large temperature difference and produce a large thermal stress, which leads to the distortion of gear shaft.

2) Preheating treatment can effectively prevent the gear shaft from being directly heated to a higher carburizing temperature and reduce the temperature gradient inside and outside the gear shaft during carburizing heating, so as to reduce the thermal stress and play a certain role in controlling the distortion of the gear shaft after carburizing and quenching.

3) Preheating before carburizing helps to reduce the distortion of the gear shaft, but different preheating temperatures and times have different effects on the distortion of the gear shaft. Therefore, it is necessary to select the optimal preheating process parameters, i.e. preheating temperature 400 ℃ and preheating time 3 h, so as to minimize the distortion of the gear shaft.

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