Research on Heat Treatment Process of Multipurpose Furnace
In order to improve efficiency and effectively reduce costs, the shaving process is adopted. The process route is: tooth blank processing-hobbing-heat treatment-hard car bore and end face-finished product, that is, the gear is not finished after heat treatment. The key is The dimensions and the accuracy of the gear are guaranteed during the heat treatment. Through analysis, the main manufacturing difficulty of the gear is the heat treatment distortion of the inner hole and the B end face. The previous production process records show that the flatness of the B end face is between 0.08-0.25 mm. The inner hole and end face of the gear are the reference for inspection and installation. The problem of abnormal noise of the differential is more prominent after the inner hole and end face are directly installed. Therefore, controlling the heat treatment distortion of the inner hole and the flatness of the end face are the keys to the successful shaving process.
The gear is a thin-walled gear with complicated shape, large internal hole size and external diameter size, and large difference in effective thickness. After measuring the deformation data of the gear after heat treatment, the gear is warped and deformed after heat treatment, and the inner hole is Elliptical deformation, so this deformation is the result of the effect of tissue stress, the larger the cross-section difference, the greater the end face distortion.
Thermal deformation is a very complex system engineering with many influencing factors. In order to clarify the clues, the major influencing factors have been combed, and research has been conducted on raw materials and preliminary heat treatment, thermal front gear accuracy, and heat treatment process.
Proposal and verification of measures
In order to study the main influencing factors, the following experimental scheme is designed:
① Material: 20CrMoH (J9 = 30-36HRC) or Japanese standard SCM420
② In order to ensure the authenticity of the test data, the samples are all actual production parts.
③ Number of samples: Each furnace (320 pieces) is randomly sampled at 20%.
④ Sampling method: Random sampling with furnace.
① Carburizing and quenching process test is carried out on VKES4 / 2 multi-purpose furnace; the quenching oil is Houghton MT355.
② A special inspection tool (as shown in the right figure) is used for the flatness measuring tool of the gear end face, and an internal hole measuring instrument is used for the internal hole detection.