Since the introduction of oil pump production technology from Germany Bosch company in the 1980s, the heat treatment process of gear shaft is based on the production process of Germany Bosch company as the blueprint, including various technological parameters and technological process. In Bosch, the cone parts of the gear shaft are annealed at high frequency to reduce hardness and improve plasticity and toughness. No fracture has been found due to heat treatment quality problems. This shows that the cone part should reduce hardness and improve plastic toughness after carburizing and quenching. Our company introduced Bosch's production process, in which the slag oil pump also adopts high-frequency annealing, but often found fracture in the cone part. In order to find the reasons, the production process and production equipment of the two companies were analyzed. The results showed that Bosch company used high-frequency annealing equipment is a special high-frequency annealing machine, heating time and heating parts are guaranteed by the equipment; Our equipment is a traditional high-frequency annealing machine, heating time and heating parts are manually controlled, heating temperature by human eyes observation. After high frequency annealing, some of the gear shaft annealing depth is very deep, and some of the annealing position does not meet the requirements at all, so the gear shaft produced by our company is often caused by human factors and fracture. To solve this problem, advanced foreign equipment can be imported, but it will cost a huge amount of foreign exchange. Therefore, starting from the actual situation, we also jump out of the Bosch process, using the cone surface coating surface anti-carburizing agent new technology. In theory, the new process also reduces the hardness of the cone part and improves the plastic toughness, so it is theoretically desirable. In order to verify the effect of the process in practical application, the material used is 20Cr.
