The heat treatment deformation of the carburized gear directly affects the precision, strength, noise and life of the gear. Even if the gear grinding process is added after the carburizing heat treatment, the deformation still reduces the precision level of the gear. There are many factors affecting the deformation of carburizing heat treatment, and only by controlling various factors can the deformation be controlled to a small degree. Controlling gear deformation must also be solved in the whole process of manufacturing gears.
(1) Effect of gear material metallurgical factors on deformation
Tests have shown that the higher the hardenability of steel. The larger the deformation. When the core hardness is higher than 40HRC, the deformation will increase significantly. Therefore, there are certain requirements for the hardenability of steel, and the narrower the hardenability zone. The more stable the deformation, the steel mills are required to provide "low and stable deformation" steel. The A1/N content ratio is controlled within the range of 1 to 2.5, which can narrow the hardenability zone and reduce deformation. In addition, the frame segregation and banded structure of the material affect the uneven deformation and uneven carburization of the spline hole of the gear.
(2) Effect of preparatory heat treatment on gear deformation
Excessive normalizing hardness, mixed crystals, a large amount of sorbite or Widmanstatten structure will increase the deformation of the inner hole, so forgings should be treated with temperature-controlled normalizing or isothermal annealing.
(3) Effect of carburizing process on deformation
Uniformity of temperature. The uniformity of the carbon layer and the uniformity of the cooling medium temperature all affect the gear deformation, and the higher the carburizing temperature, the thicker the carburizing layer. Low oil temperature and large gear deformation. Therefore, it is necessary to improve the equipment, optimize the process, and improve the quality of gear heat treatment.
(4) Effect of quenching on deformation
The quenching and cooling behavior is the most important factor affecting the gear deformation. The deformation of hot oil quenching is smaller than that of cold oil quenching, and it is generally controlled at 100°C±120°C. The cooling capacity of the oil is also critical to deformation. Both the stirring method and the intensity affect the deformation, and the disc gears quenched by the upper quenching press, according to the deformation of various gears. Adjust the parameters of the fire press to reduce the deformation, adjust the pressure of the inner and outer dies and the expansion core block, the size of the fuel injection volume of each section and the upper work table to control the deformation.
