The raw material of driving spiral bevel gear is 20CrMoH steel in accordance with GB / T 5216-2014 structural steel with guaranteed hardenability, which is required to be carburized and quenched. The effective hardened layer depth of the finished product at the pitch circle of the tooth shall reach 1.0 ~ 1.4mm (550hv), the surface hardness shall reach 58 ~ 63hrc, the core hardness shall reach 30 ~ 40HRC (evaluated according to the intersection of the tested part at the root circle and the central axis of the tooth), and the external thread hardness shall not exceed 45hrc. In addition, the final strong shot peening treatment shall be carried out in accordance with JB / T 10174-2000 quality inspection method for enhanced shot peening of iron and steel parts. The surface coverage shall not be less than 200%. The shot peening strength is evaluated as type A. the arc height value of alming test piece shall not be less than 0.44mm, and the residual compressive stress index at the tooth root of the finished product shall not be less than 896.5mpa.
During the trial production of new products of the sub supplier, the external thread of the driving spiral bevel gear shall be subject to anti-seepage treatment before heat treatment, so as to reduce the hardness of the external thread. On the premise that the specified driving distance was not reached during the road test, an abnormal fracture occurred at the R-angle area of the connection transition between the external thread and the external spline. Through the anatomical analysis of the failed parts, it is found that the hardness of the local position of the external thread exceeds 48hrc. As the anti-seepage link involves whether the anti-seepage coating is used correctly or not, as well as many factors such as people, machines, materials, methods and people in the ring, and considering that the R angle of the connection transition between the external thread and the external spline is an area where stress is easy to concentrate, the hardness reduction process of the external thread has been changed and optimized after technical communication and the review and approval of the driving spiral bevel gear customer, The heat treatment after anti-seepage of external thread is optimized to direct heat treatment without anti-seepage, and then induction annealing is carried out at the external thread.