In the rotary forging process of spur gear, the contact area between the swing head and spur gear blank is only part, and the surface of rotary forging spur gear has two parts: contact area and non-contact area. The contact area with the swing head directly bears the pressure of the tool and produces plastic deformation, which is called active deformation.
According to the law of minimum resistance, the schematic diagram of metal flow in this area can be roughly drawn (as shown in Figure 1).
Therefore, the metal flow in the active deformation zone can be roughly divided into two parts: one part is mainly radial flow; The other part is mainly tangential flow.
After rotary rolling, the upper end face of spur gear blank becomes S-shaped, as shown in Figure 2.