Figure 1 shows the equivalent stress distribution diagram of closed die forging of spiral bevel gear. Under four reduction quantities, the reduction is 30%, 50%, 80% and 100% respectively. When the reduction is 30% and 50%, the blank is just filled to the tooth cavity, the metal deformation is mainly concentrated in the tooth cavity, and the upper and lower ends of the blank are filled to the tooth cavity at the same time. As the metal fills the tooth cavity, it is hindered by the friction at the mouth of the cavity, so the equivalent stress at the tooth root is large, with 200MPa. When the reduction is 80%, most of the metal has been filled into the tooth cavity. At this time, the tooth profile has been basically formed. When the reduction is 100%, the cavity of the die is completely filled, and the tooth top and tooth corner are finally filled, with an equivalent force of 250Mpa.
Figure 2 shows the distribution of speed field of closed die forging of spiral bevel gear. The main deformation is concentrated on the teeth of the spiral bevel gear. Metal flow mainly includes axial flow, radial flow and tangential flow. With the descending of the upper die, the whole blank is extruded, and the metal flows downward along the axial direction. The blank is squeezed by the pier and the metal begins to flow to the tooth cavity
At this time, the metal flows along the radial direction and fills the tooth cavity. Because the tooth surface of the spiral bevel gear is a spiral surface, when the metal fills the tooth cavity, there is not only radial strain, but also tangential strain. Its metal flow is not only radial flow, but also tangential flow. Due to the non-uniformity of metal flow, the metal flow will have sequence and speed, resulting in metal folding and other defects.
Fig. 3 shows the load stroke curve of closed die forging of spiral bevel gear. Since the diameter of the blank is close to the diameter of the tooth root circle, the free pier roughening time is reduced. In the period of metal filling into the tooth cavity, the load rises gently with the increase of stroke. The reason is that with the increase of metal filling into the tooth cavity, the deformation resistance and friction resistance will also increase. In the final filling stage, the metal has basically filled the tooth cavity, and the blank flow is difficult. To overcome the hydrostatic pressure generated by most of the filled metal in the static state, the working load increases sharply, and the load value reaches the maximum at this time.