Asymmetric design process of upper and lower dies for gear blank forging

In the process of gear blank forging, due to the cylindrical upsetting effect of the blank, the contact area between the blank and the die is increasing, resulting in the symmetrical upper and lower die design, which is easy to cause uneven deformation of the blank, and the filling effect of the upper die is better than that of the lower die. Therefore, the asymmetric upper and lower die design can improve the uneven flow of metal and improve the filling quality.

(a) Before improvement (b) After improvement

Figure 1 shows that the difference between the two schemes of symmetrical and asymmetric die design is that the asymmetric design deepens the depth of the two die cavities of the upper die, changes the stress state of the blank, and accelerates the flow at the lower part of the blank, so that the metal flow velocity at the upper, middle and lower parts tends to be the same.

(a) Before improvement (b) After improvement

Fig. 2 is the equivalent stress distribution diagram of the gear blanks of the two schemes. The stress distribution of the symmetrical scheme is uneven and concentrated in the middle of the gear blank, while the stress distribution of the asymmetric scheme is relatively uniform, indicating that the flow at the upper and lower ends of the gear blank of the asymmetric scheme is basically equal, the deformation symmetry is good and the deformation stress is small, It lays a good foundation for subsequent heat treatment. Therefore, the forging quality is improved by improving the process, the deformation at the spoke is uniform, and the strength and toughness of each part of the gear blank are also significantly improved.