Spiral bevel gear parts are formed by double split precision forging. In the forming process, the forming quality and forming force are affected by many process parameters, such as the shape of preform, split gap, position of internal and external split surface, cone angle of preform, etc. whether these factors are reasonable or not is the key to the success or failure of the scheme. According to the metal flow in the double split precision forging process of spiral bevel gear, the influence law of various process parameters on metal flow and forming force is explored, which provides a basis for the optimization of process parameters and die structure design of double split precision forging.
Using DEFORM-3D finite element numerical simulation software, the double split precision forging process of spiral bevel gear is numerically simulated, and the effects of various process parameters on metal forming quality and forming force are analyzed. The following conclusions are obtained:
1) The structure of spiral bevel gear preform shall be cylindrical inner hole conical preform, and the internal and external diameter shall be close to the size of formed parts. The inner diameter of the preform should be greater than the diameter at the small end of the tooth shape of the female die. When the inner diameter is too large, the deformation degree is large and the internal metal flow is violent in the forming process, so the forming quality cannot be guaranteed.
2) Optimum cone angle of spiral bevel gear preform α 140 ° ~ 150 °. If the cone angle of the preform is too small, it is easy to cause the large end of the tooth cavity of the female die not to be fully filled. If the cone angle of the preform is too large, the middle part of the tooth cannot be filled in time. If the cone angle is too large or too small, the forming force will increase.
3) The position of the inner diversion surface of the spiral bevel gear should be far away from the tooth shape of the female die. When the position of the inner shunting surface is close to the tooth shape of the female die, the metal material flows too much along the radial direction of the shunting gap, and the forming quality is poor.
4) The upper end face of the outer split surface of the spiral bevel gear shall be lower than the lower end face of the inner split surface. When the position of the outer diversion surface is in area B, there is little difference in the flow speed of the metal material to the inner and outer diversion gap. At this time, the tooth shape is fully filled.
5) The internal split clearance of spiral bevel gear has an influence on the forming force. When the internal split gap is too small, the excess metal cannot flow out of the split gap in time during the filling of the tooth shape of the die, resulting in the increase of the forming force; When the shunt gap is too large, the metal material flows out from the shunt gap prematurely, resulting in unnecessary waste of materials.
6) The outer split clearance of spiral bevel gear directly affects the forming quality and forming force. If the clearance of the outer shunt is too large, the tooth shape filling will not be full; If the shunt gap is too small, the forming force will increase. For the driven spiral bevel gear of automobile rear axle, when the inner shunt gap is 5mm and the outer shunt gap is 4mm, the forming quality is good and the forming force is small.