Die forgings have many closed sections, the distance between the two ribs is short, the ribs are thin, the distance between the two ribs and the thickness of the web are large, and the surface of many parts is non-processed. Because the ribs of die forgings are very thin, folding problems often occur at the intersections of thin ribs and webs, and at the junctions of ribs and flanges. Folding on die forgings destroys its continuity, because it weakens the cross section, or fatigue cracks occur due to stress concentration during use, which greatly reduces the bearing capacity of forgings, and ribs are generally used to give rigidity or other The parts provide mounting or linking surfaces, so fold defects are to be prevented.
1 Folding defect location and cause analysis of aluminum alloy die forgings
1.1 The folding part of the die forging can be seen from the structure and shape of the forging. In production, most of the folding occurs in the web and ribs, ribs and edges of the forging.
1.2 Causes of folding defects ① Wool design, unreasonable design, resulting in differences in metal distribution. The forging process chooses a long bar with a diameter of 180mm×420mm, squares it in two multi-square sections until it reaches 120mm×180mm×480mm, and then elongates the middle part, and finally presses it on a 50 hydraulic press. It can be seen from its shape that its upper and lower ribs are symmetrical, although the shape of the wool is close to that of the forging
The metal on the upper part and the bottom of the forging is uneven, the distribution of the metal on the bottom is large, and the height is not enough. The forging is symmetrical up and down. When molding, the upper ribs are filled with the cavity, but the lower metal is not filled. With the deformation, the upper part of the fillet in the cavity This creates a cavity where eventually the metal meets the lower part to fill it, creating a fold. ② From the analysis of the fillet radius of the connection between the web and the ribs, due to the small fillet radius, in the die forging, after the two ribs are filled, the upper and lower dies will continue to move closer together, and the surface metal will pass through in the direction of less resistance and flow into the burr groove , and drive the metal on the surface to flow out, so that the tendons and webs are stacked together, resulting in folding. ③When molding is considered from the metal flow direction, the metal filling cavity does not flow close to the rounded corner wall, leaving the rounded corner, so that the metal first contacts the opposite side wall, and then contacts the bottom, and the metal flows back to the rounded corner. Make the metal surface of forward flow and reverse flow overlap, and then form folds. ④The damage was not completely repaired after the last molding, and the folds were not quickly repaired to make it enter the next molding, so that the inside and outside of the forging had folds.
1.3 The method to solve the folding defect ① Change the forging material to a long bar with a diameter of 170mm×280mm, pull it out on the long drawing die, pull out the head end with a diameter of (170×80+10)mm, and flatten the tail to 70mm +5i"~11TI thick. Choose new and improved wool to mold, you can see that the upper and lower metals are uniform, and the metal deformation is relatively uniform during the molding process. The rounded corners of the long part of the rod will transition smoothly. When molding, make it perpendicular to the parting mold The flow resistance in the direction is small, and no cavity can be generated in the upper part of the fillet in the cavity, so that the metal can evenly fill the cavity. ② Increase the radius of the fillet on the rib and the web and the radius of the convex fillet on the mold, so that the metal can be evenly filled when molding cavity, the flow resistance is reduced, and the excess metal will flow into the burr groove along the shape of the cavity. ③ There is no folding on the surface of the forging after the improved process, and the streamline is distributed along the forging, which meets the drawings and acceptance standards.
