As we all know, the quality of gears is influenced not only by the steel itself, but also by the heat treatment process to a great extent. The heat treatment process mentioned here not only refers to the carburizing and quenching process of gear, but also includes the heat treatment process of gear forging blank. Since the Seventh Five Year Plan, China’s heat treatment technology has developed greatly, introduced many advanced equipment, digested and absorbed some foreign advanced technologies, but the domestic blank heat treatment level is still quite backward. Due to the low level of mechanization and poor processability of the treated blank, it brings many difficulties to the processing and subsequent heat treatment. Generally speaking, the heat treatment of gear forging stock has two purposes:
One is to ensure good cutting performance, which requires the ferrite pearlite structure with uniform equiaxed grains after heat treatment;
The second is to ensure that the gear blank has a uniform structure, which is beneficial to reduce the inevitable irregular deformation during carburizing and quenching, and is of great significance to ensure that the gear has a good contact surface and reduce noise.
For a long time, most domestic gear forgings have been normalized. Although the process is simple, there are two problems: first, it is easy to produce granular bainite and banded structure, which affects the machining performance; Second, the hardness dispersion of parts is large, and the heat treatment deformation is difficult to control.