- Taking 9t one speed gear parts as an example, the effects of different pre heat treatment methods on the deformation of heavy truck cylindrical gear are compared. After isothermal annealing, the average change of common normal line after carburizing and quenching of 9t one speed gear parts is only 61.7% of normalized state, and the average change of m value is only 26.8% of normalized state.The structure of heavy truck cylindrical gear pre heat treated as isothermal annealing is smaller than that of ordinary normalizing. After carburizing and quenching, the structure stress of heavy truck cylindrical gear parts is smaller, and its deformation is significantly smaller than that of heavy truck cylindrical gear pre heat treated as ordinary normalizing. Therefore, in order to control the deformation of carburized gear of truck gearbox, the pre heat treatment of heavy truck cylindrical gear blank should adopt isothermal annealing.
- The deformation of carburizing and quenching of heavy truck cylindrical gear is closely related to its carburizing process, that is, carburizing and quenching temperature, quenching cooling speed, stirring mode and furnace loading mode. The comparative tests of different process methods such as carbonitriding and carburizing, paperback and hanging, cooling slow stirring and fast stirring are carried out on the thin-walled 9t 3456 speed gear sleeve parts. It is concluded that according to the actual situation of the cylindrical gear parts of heavy truck, the carburizing temperature can be reduced, the carbonitriding method can be adopted, or the cooling speed can be reduced under the condition of meeting the quenching performance, and the correct charging method can be adopted, It can obviously improve and control the heat treatment carburizing deformation of cylindrical gear parts of heavy truck.
- The cylindrical gear of heavy-duty truck is made of steel to ensure hardenability. After carburizing and quenching, the dispersion of each size is small and the heat treatment deformation is regular. Therefore, in order to control the carburization heat treatment deformation of cylindrical gear of heavy-duty truck in actual production, it is necessary to purchase high-quality steel to ensure hardenability at fixed points on the raw materials. The guaranteed hardenability steel is applied to three typical parts of our heavy truck gearbox product hc7s-120: first and second speed gear sleeve (represented by thin-wall parts), fourth speed gear (represented by transmission gear parts) and second shaft (represented by shaft parts). Compared with the deformation data of the original parts made of ordinary materials, it shows the contribution of controlling the steel hardenability belt to reducing the carburization and quenching deformation fluctuation of heavy truck cylindrical gear. Through experimental demonstration, the cylindrical gear parts of heavy truck have basically adopted the steel to ensure hardenability, which has laid a solid foundation for the mass production of heavy truck gearbox.
- For the mass production of heavy truck cylindrical gear, in order to control the deformation and meet the production requirements, the heat treatment of heavy truck cylindrical gear should be adjusted repeatedly and find the correct heat treatment process for carburizing and quenching on the basis of steel to ensure hardenability, gear blank die forging, isothermal annealing of gear blank, fixed cold work processing means, etc., combined with the actual situation of each heavy truck cylindrical gear part, Can be fully guaranteed in actual production. This is also proved in the production practice of heavy truck cylindrical gear.