The main feature of die forging is that the diameter of outer circle and inner hole of automobile rear axle basin gear blank forging is large and the material utilization rate is low, because there are many waste materials produced by connecting skin and flash during die forging of gear blank.
When the open pass is formed by rolling, the groove of the rolling wheel is wide and shallow, which has little restriction on the end face of the workpiece, and it is easy to produce axial flash or burr in the rolling process, which is not easy to control. When open pass radial rolling, the workpiece is easy to produce end pit and butterfly distortion. Once these defects occur and are serious, a correction process needs to be added. During the radial rolling forming of closed pass, the pass is open in the initial stage of forming. With the increase of rolling feed, the pass begins to close gradually in the later stage of rolling.
When closing the mold, the flash or burr will be cut off by the edge of the rolling wheel and core rolling. Compared with the beginning, the groove of the closed ring is deeper, and the axial deformation of the workpiece is limited to a certain extent. Therefore, the closed ring can effectively eliminate the defects of end pit and dish warpage. Therefore, the closed pass radial rolling forming process is the preferred process for the production of ring forgings at present. It has high accuracy of size and shape, no flash burr and dislocation error, and can produce ring clean forgings.