The transmission input shaft heat treatment process

2019 - the transmission input shaft heat treatment process 07 - 09 闫保秋 ( Hebei iron and steel group company XuanGong) 1. Technology determine my company 430 HP bulldozer transmission adopts planetary reduction structure, input shaft fine and long, and in the process of working under high torque, four period of spline, require round to beat & le; 0. 15 mm, as shown in figure 1. Material is 42 crmo, technical requirements do heat treatment hardness up to 48 ~ 55 HRC, process routes: forging & rarr; Normalizing & rarr; Rough machining & rarr; Finishing & rarr; Milling spline & rarr; Heat treatment & rarr; Straightening & rarr; Grinding & rarr; Inspection & rarr; Assembly. The RJJ - heat treatment Protective atmosphere heating 105 pit type furnace, the specific process as shown in figure 2. Hardness meet the technical requirements after heat treatment, but parts deformation, deformation in 4 ~ 6 mm, because of the high strength parts, using cold straightening can not meet the technical requirements, straightening by using hot straightening and combined hydraulic press cold straightening straightening. So on the input shaft forming local soft point, which affect the strength of the input shaft, in the process of work I have input shaft fracture accident, seriously affect the quality of bulldozers. To solve the problem of the technical department for research project. 2. Analysis and improvement measures to test the fracture of the input shaft, 53 ~ 54 HRC, surface hardness of heart of 49 ~ 50 HRC hardness, all show parts during quenching has been hardening. Poor parts, therefore, high strength, toughness, straightening the depend mainly on the thermal stress of hot straightening to straight, in local forms more internal stress, and partial formation during hot straightening soft point. From the perspective of the location of the fracture, is just as hot position fracture. To further confirm the input shaft fracture have direct relationship with hot straightening. In order to avoid the hot straightening, at the same time guarantee the strength of the parts, with lower hardenability materials 20 crnimoh instead of 42 crmo, will increase a part after forging, high temperature normalizing process to further stabilize and improve organization, heat treatment process using carbonitriding of low temperature quenching, as shown in figure 3. In order to reduce the heat treatment deformation, shaft end face a M16 process holes on parts, specially designed for vertical lifting equipment as shown in figure 4, to carry on the process test, the surface hardness of 58 to 63 HRC after heat treatment, heart, 35 ~ 40 HRC hardness, deformation within 2 mm, heart for parts of low hardness, better toughness, cold straightening autotransmitting mechanism, it is easy to meet the technical requirements. Installed validation of half an year, stable quality, complete quality research, is now mass production. 3. Conclusion through the process improvement, solve the problem of the input shaft fracture and slender shaft alignment problem, stable product quality, the slender shaft adopts the hoisting method can significantly reduce the axial deformation, but also further clear, when straightening the key parts, must be careful with hot straightening.