The main reference standards for evaluating the final forming quality of gear blanks are as follows:
(1) The hub part first fills the mold cavity, and then the rim part fills the cavity. The time difference between these two steps should be as small as possible to ensure that the burrs extruded from the rim part are as few as possible.
(2) The metal flow inside the gear should have a certain directionality, and there should be no metal reflux.
(3) Metal folding shall not occur during gear forming.
As can be seen from figure (a) and figure (b), Φ 120mm and Φ In the forging process of 110mm bar gear blank, the rim part first fills the die cavity, while the hub part is difficult to form. The hub part can not fully fill the die until the end of the die stroke; In addition, when the rim part fills the mold cavity, the thickness of the rim will be significantly greater than the required size of the gear. Therefore, with the downward pressure of the mold, the metal in the rim part will flow back to the hub part, which will destroy the metal fluidity in the workpiece and eventually lead to the decline of the mechanical properties of the workpiece.
As can be seen from figure (c), Φ In the forging process of 100mm bar gear blank, the hub part first fills the die cavity, and then the rim part just fills the die cavity, and the workpiece extrudes less burrs from the gap between the upper and lower dies; From the analysis of metal flow state, the metal flow direction of the bar tends to be consistent in the whole forming process, and there is no metal reflux, so the forming state of the bar is good.
As can be seen from figure (d), Φ Forging process and of gear blank with 90mm bar Φ Similar to 100mm bar, the metal fluidity can basically tend to be consistent, but the filling time difference between the cavity of the hub and rim is large, and its performance still needs to be further analyzed.
Through the comparative analysis of the above four schemes, it can be seen that, Φ 100mm bar has the best forming effect and can form gear blank well, but whether it is the best scheme needs further analysis.