Folding Process Of Forged Aluminum Alloy

The folding of forged aluminum alloy is a defect formed by the accumulation and stacking of oxidized surface metals during the deformation process of the metal. After the oxide scale is cleared, ordinary folds can be identified with the naked eye. Folds that are difficult to detect with the naked eye can be inspected by magnetic particle testing or penetrant testing. When the folding is too shallow, it increases the grinding workload; when it is too deep, it leads to the scrapping of the forging. Now, Lanxi Chihang Machinery Co., LTD., a forging manufacturer, will elaborate on the solution for dealing with folding defects in forged aluminum alloys.

1. Folding of forged aluminum alloy oil seals

Oil seal folding is a forming defect encountered during the commissioning of crankshafts with oil seal flanges, and it has two forms: closed and partially closed. The main mechanism of its formation is that a part of the shape was formed in the early stage of forming here. In the subsequent forming, due to the occurrence of a large axial movement, a significant axial offset occurred in the formed part of the shape. Folding defects occurred during the feeding process in the later stage of forming.

The pre-forging forming process can modify the shape of the pre-forged aluminum alloy here, weaken the steps, and not only coordinate the material forming application rate at the back end but also handle the folding defect. In the forming process without pre-forging, such problems can be dealt with by appropriately extending the length of the rear part of the blank. When making bulk purchases, it is also necessary to pay attention to the positioning of the raw materials to prevent them from leaning towards one end and causing such problems.

2. Folding of forged aluminum alloy connecting rod necks

The folding of the connecting rod neck is a common forming defect in the direct final forging process of die forging hammers. It occurs on the upper part of the inner side of the opening mold surface. The shape is in the form of a horizontal "one" or "eight" shape, and there are also vertical "one" shapes or non-overlapping groove shapes. In the forming process of the forging press, due to the pre-forging step, such defects are rarely seen. When the pre-forging opening storage and material distribution structure is unreasonable, longitudinal "straight" or non-overlapping groove defects will occur during the final forging.

Regarding the die forging hammer process, the main reason for the folding of the connecting rod journal is the absence of a pre-forging step. During the initial deformation of the crankshaft die forging, the protruding part of the die at the opening of the connecting rod journal is formed first, and the blank will form a pit shape. Subsequently, this pit shifts laterally, and finally, the adjacent metal flows back to fill the unfilled pit. When the pit is more obvious, folding is finally formed at this pit. The treatment method is to control the intensity of the impact at different forming stages, but it has higher requirements for operation. Or, a larger fillet can be made at the protruding part of the edge at the opening of the connecting rod neck of the mold, and the thickness of the connecting skin at the opening can be increased to improve the movement of the metal. The latter is a commonly used treatment method. The crankshafts consumed by forging presses usually do not have such defects due to the existence of pre-forging steps. However, when the pre-forging structure and parameters are unreasonable, grooves or folds may occur. Generally, the thickness of the material connecting the skin is too thick, or the thickness difference between the upper and lower skin is too large. During the final forging and forming process, the blank in this part deviates too much, or the blanks in the upper and lower parts move up and down in a misaligned manner. Regarding the die forging process of forging presses, this kind of defect can be easily dealt with simply by correcting the mold according to the cause.

3. Folding of burrs pressed in forged aluminum alloy

The higher longitudinal burrs drawn out by edge cutting are pressed into the forging body after subsequent correction to form folds. Such folds are more likely to occur during the alignment of the crankshaft formed by twisting. The burrs at the horizontal parting surface position after edge cutting are turned to the positions in the grooves of the upper and lower dies of the correction die after twisting. After thermal correction, the longer burrs are pressed into the forging body to form folds. Timely replacement or repair of aged edge cutting dies can prevent such defects from being pulled out by avoiding high longitudinal burrs.

4. Folding of the parting surface of the forged aluminum alloy balance block

For the unformed forgings, the folding of the deep forging body has already occurred at the parting surface of the balance block. After being fully formed, there will be some remaining folding parts of the forging body. The main reason for this is that the billet specification is too small. Regarding the easily formable crankshaft, although the blank specification is relatively small, it can still be perfectly filled and formed, but it is prone to folding on the parting surface of the balance block. Minor folding can be improved by increasing the fillet of the adjacent die at this part, while deeper folding can be addressed through the inclined parting design of the pre-forged structure. In the absence of a pre-forging process, it is often treated by increasing the billet size or possibly by adopting a semi-closed process.