The folding of forged aluminum alloy is a defect formed by stacking together oxidized surface metal during the process of metal deformation. After the oxide scale is cleared, ordinary folds can be identified with the naked eye. For folds that are not easy to detect with the naked eye, the inspection can be stopped by magnetic particle testing or penetration testing. When the fold is shallow, the grinding workload is increased, and when the fold is deep, the forging will be scrapped. Next, PTJ Aluminum Co., Ltd., a forging manufacturer, discusses how to deal with the folding defects of forged aluminum alloys.
1. Forged aluminum alloy oil seal folding
Oil seal folding is a forming defect encountered in the commissioning of crankshafts with oil seal flanges. There are two forms of closed and incomplete closed. Its composition mechanism is mainly that the local shape is formed at the initial stage of forming, and the subsequent forming has a large axial movement, which causes a significant axial deviation of the formed local shape. Folding defects occurred during the replenishment process in the late forming period.
There is a pre-forging forming process that can change the shape of the forged aluminum alloy pre-forging here, weaken the step, not only can coordinate the back-end data forming application rate, but also deal with folding defects. In the forming process without pre-forging, this problem can be solved by appropriately increasing the length of the partial blank at the rear end. Also pay attention to the positioning of the blanks when mass production, avoid tilting one end and causing such problems.
2. Forged aluminum alloy connecting rod neck folding
Connecting rod neck folding is a common forming defect in the direct final forging process of die forging hammers. Produced in the upper part of the parting surface inside the gear opening. The shape is in the shape of a horizontal “one” or “eight”, and there are also vertical “one” or non-overlapping grooves. In the forming process of the forging press, due to the pre-forging process, there are few such defects. When the pre-forging opening and distributing structure is unreasonable, the longitudinal “one” or failure will occur during the final forging. Coincident groove defects.
Regarding the die forging hammer process, the main reason for the folding of the connecting rod neck is that there is no pre-forging step. When the crankshaft die forging is initially deformed, the protruding part of the mold at the opening of the connecting rod neck is formed first, and the blank will form a concave shape. Later, this pit shifts laterally, and finally the metal in its adjacent parts reflows to fill the unfilled pit. When the pit is more obvious, a fold is formed at this pit. The processing method is to control the severity of the blow in different forming stages, but the operation requirements are higher, or the protruding local corners of the connecting rod neck of the mold are made larger rounded corners, and the opening position is increased. The thickness of the skin is used to improve the activity of the metal, and the latter is a common treatment method. Crankshafts produced by forging presses usually do not have such defects due to the presence of pre-forging steps. However, when the pre-forging structure and parameters are unreasonable, grooves or creases will be produced, usually the stock is too thick or the upper and lower skins are connected. If the thickness difference is too large, the blank at this part deviates too much or the upper and lower parts of the blank move up and down during the final forging. Regarding the forging process of the forging press, such defects can be easily dealt with only by correcting the mold for the reason.
3. Folding of forged aluminum alloy burrs
The higher longitudinal burrs drawn by the trimming are post-corrected and pressed into the forging body to form a fold. The twisted crankshaft is more likely to exhibit such folds during calibration. The burrs at the position of the parting surface after trimming are twisted. Then turn to the position in the grooves of the upper and lower molds of the correction die, and the longer burrs after thermal correction are pressed into the forging body to form a fold. Change or repair the aging die trimming die in time to prevent such defects from pulling out higher longitudinal burrs.
4.Forged aluminum alloy balanced block parting surface folding
For forgings that are not completely formed, the folds of the forging body have been deepened at the parting surface of the equalizing block, and there will be partial folds of the forging body remaining after the complete forming. The main reason is that the billet size is too small. Regarding the easy-to-form crankshaft, although the size of the blank is too small, it can be completely filled and formed, but it is easy to fold the parting surface of the balanced block. The fine folding can be improved by increasing the corners of the adjacent mold at this part. This problem is dealt with through the pre-forging structure’s tendency to material distribution design. In the absence of the pre-forging process, it is often handled by increasing the blank gauge or possibly using a semi-closed process.