The pre-forging step diagram is designed according to the final forging step diagram. The following problems must be paid attention to during design:
1. In order to make the metal fill the groove in the thick way during the final forging, the height of the pre-forging should be 2-5mm larger than the corresponding height of the final forging; and the horizontal dimension should be appropriately reduced, and the cross-sectional area of the pre-forging It has a larger cross-sectional area than the final forging.
2. If the cross section of the final forging is circular, the corresponding pre-forging cross-section should be elliptical, and the elliptical cross-section is about 4%-5% of the corresponding cross-sectional diameter of the final forging.
3. The volume of each part of the pre-forging part should be strictly controlled so that the excess metal can flow reasonably during the final forging to avoid defects such as metal backflow and folding. For example, for the hub portion of the forging, the metal volume of the pre-forging step can be 1% to 6% larger than the final forging step. For forgings requiring punching, when the aperture is not large, the difference between the inner hole depth of the pre-forging and the corresponding inner hole depth of the final forging is not more than 5 mm, otherwise the inner hole will have more metal flowing in the radial direction during final forging. Fold or wear help. When the aperture is large, the final forging groove must also be designed to accommodate excess metal.
4. The positioning of the pre-forging in the final forging groove should be considered. For this reason, the shape and size of some parts of the pre-forging step should be basically consistent with the final forging to avoid a part of the filling due to the deflection of the blank, and the other part produces excessive burrs.
5. The pre-forging groove generally does not have a burr groove, but for some forgings with complex shapes, some parts of the pre-forged groove should be considered to have a burr groove, and the height of the bridge is 30% higher than the height of the final forged burr bridge. 60%, the width of the bridge and the height of the warehouse can be smaller.
6. When the metal can not be filled in the final forging by the push-in method, the side of the pre-forging should be in contact with the mold wall at the beginning of the final forging to restrict the outward flow of the metal, thereby forcing the metal to flow. Deep in the groove. In order to avoid the formation of the inner wall of the hole, the corner of the punching boss in the final forging groove should not be too small.