Summary of crack failure in heat treatment of spiral bevel gear

Three pairs of spiral bevel gears for reducer were heat treated in the heat treatment processing company according to the technical requirements. When the heat treatment process entered the strong infiltration stage, the operator found that the carbon potential in the furnace could not reach the value required by the process. Relevant technicians went to the site for inspection, and the inspection result was that there was a problem with the oxygen probe. They decided to cool down and slowly cool the workpiece out of the furnace. It lasted about 3H from problem discovery to problem solution.

After replacing the oxygen probe, the operator shall process the workpiece according to the heat treatment process specification. When the heat-treated spiral bevel gear was transferred to the processing department for rough machining, it was found that there were a large number of cracks in both large and small spiral bevel gears. Spiral bevel gear is a forging made of 18crnimo7-6 steel. The treatment process is: carburizing at 925 ℃ for 15h + diffusion for 5.5h + quenching at 820 ℃ and tempering at 180 ℃ for 8h.

This paper mainly describes the macro and micro morphology of the spiral bevel gear crack, analyzes the causes of the gear crack, and puts forward the improvement measures to prevent similar accidents.

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