Multi-purpose furnace study on heat treatment process

In order to improve the efficiency and reduce the cost effectively, the shaving process is adopted. The process route is: gear blank processing - gear hobbing - heat treatment - hard turning inner hole and end face - finished product, that is, after heat treatment, the gear is not refined, and the key size and gear precision are guaranteed in the heat treatment process. Through analysis, the main manufacturing difficulty of the gear is the heat treatment distortion of inner hole and end face B According to the previous production process records, the flatness of the B end face is between 0.08-0.25mm. Because the inner hole and the end face of the gear are the inspection and installation basis, the abnormal noise of the differential after the inner hole and the end face are directly installed is more prominent. Therefore, the key to the success of the shaving process is to control the heat treatment distortion of the inner hole and the flatness of the end face.

The gear belongs to thin-walled gear, with complex shape, large inner hole size and outer diameter, and large difference in effective thickness. Through the measurement of deformation data after heat treatment, after heat treatment, the gear is bowl shaped warping deformation, and the inner hole is elliptical deformation. Therefore, this kind of deformation belongs to the result of tissue stress. The greater the difference in cross section, the greater the distortion variable of end face.

Thermal deformation is a very complex system engineering, which has many influencing factors. In order to make a clear understanding, the major influencing factors are combed, and the research is carried out from the aspects of raw materials and preparation heat treatment, precision of gear before heat treatment, heat treatment process, etc.

Proposal and verification of measures

In order to study the main influencing factors, the following test scheme is designed:

① Material: 20CrMoH (J9 = 30-36hrc) or Japanese standard SCM420

② In order to ensure the authenticity and validity of the test data, the samples are all actual production parts.

③ Number of samples: 20% of samples are randomly selected from each furnace (320 pieces).

④ Sampling method: random sampling with furnace.