Analysis of Folding Defects and Causes of Aluminum Alloy Die Forgings (2)

[China Aluminum Network] Die forgings have many closed sections, the distance between the two intercostals is short, the ribs are thin, the spacing between the two ribs and the thickness of the web are large, and many parts of the surface are not processed. Because the forging ribs are much thinner, folding problems often occur at the intersections of thin ribs and webs, ribs, and rims in production. Forgings on the forging collapse its continuity, because it makes the section weakened, or stress concentration occurs in the use of fatigue cracks, to a large extent reduce the forging capacity, and ribs are generally used to give rigidity or for other The parts provide mounting or link faces, so prevent folding defects.

2.1 Folding defect issues The following is a semi-spindle forging process, to illustrate the use of forming step shaft process defects, and after the improvement of the mold solution. The semi-shaft forming step is:

1 Shoulder diameter is 130mm;

2 Pull the long ends to a diameter of 130mm, free forging;

3 shoulder compression diameter 118mm;

4 Pull one end to diameter 115mm, free forging;

5 pressure shoulder diameter 108mm;

6 Pull the other end to a diameter of 105mm, free forging;

7 trimming and straightening forming, straighten the die. When using the mold, folding defects occur easily in steps 1, 3, 5, and 7, and the step of straightening the mold is more serious.

2.2 Problem Analysis Now take the step of straightening and buckling as an example to analyze the causes of defects and process improvement. Dropping the different parts of the mold cavity to create a step, the height of which is determined in combination with the difference in diameter, which causes the step to be not violently deformed and the flow is not smooth during the forging process. When the upper and lower modules are closed, the cavity is provided with a stepped gap at the contact step to avoid concentration of stress and to smooth the flow, and to provide roundness, which further affects the metal flow. In this way, in addition to the steps in most of the metal flow at the step location, the remaining metal due to the diameter change caused by poor flow, there is a part of the flow into the gap between the upper and lower modules, forming a "flash" like when the die forging . When the forging is rotated and forged, the remaining metal in this portion is bent on the forging to be attached to the surface of the forging because the thickness is thin. When the forging is further forged, it will get stuck in the forging and form a fold. The reason (turned to page 1O5) (continued from page 1o3) is that there are two causes of folding defects in the ordinary form. One is the step on the cavity because of different diameters, and the other is the corner of the cavity. To analyze these two factors:

1 cavity corner can not be canceled;

2 The folding began to appear at the junction of the module, indicating that the proximity to the contact site was the main cause of folding.

2.3 Solve the problem Modify the tooling to solve the problem of shaft forgings folding from the root. At the step of the die, two tangential lines are set tangentially to the small-diameter circular arc and are tangent to the large-diameter rounded corner. This partially eliminates the step existing in the contact area of ​​the module and slows the change in shape. When the module is closed, a cavity containing the remaining metal is produced at the corner, not the original step gap. When forging the remaining metal is diverted to this part, no flash is generated and a prismatic block is produced. When the forging is rotated and forged, the remaining metal of this part is not bent first and then folded because it is prismatic because of its thickness. Instead, it is forged and leveled and then melted into the inside of the forging and becomes a whole, and no folding defects occur.

3 Folding defects of bending forgings bending forgings are commonly used structural forgings, mainly including connecting rods, crankshafts, and pipe joints. The majority of defects of these forgings are the folding of the bending angle transition sites, and the flow lines of the forgings are to be distributed along the direction of the parts. This kind of folding is restricted by the shape of the forgings, especially the bending angle is less than 110. Folding is difficult to avoid.

3.1 Part Shape and Defect Position The forging material is stainless steel, the equipment used is a friction press, and the process is bending blanks and open die forging and cold correction. Defect location and depth have this feature: the location is where the curved corner meets the platform. After the defect is polished, the depth is 1-2mm. After the open inspection, it is determined that the nature of the defect is folding.

3.2 Causes of Defects This defect is mainly due to the fact that when the die is forged, the material at the bent end of the bent bar stock is less, and the material at the deformation zone is more than that of the round table. Therefore, at the time of die forging, the material at the bent end is toward the larger material table. Collectively, the metal part of the circular table is filled into the cavity, and the part flows toward the outside of the cavity, and flows together with the bent end to fill the material. If the bent bar material has problems such as wrinkles, the difference in the material flow will increase, and therefore the folding occurs. .

3.3 Resolve Defective Measures Take this measure to resolve the cause of the defect. The bending process is a key step in the folding process. It is known from the experiment that when the temperature and the striking force are appropriate, the bending angle of the material exceeds 120. When the bending radius exceeds 8mm, the blank generally does not appear wrinkles. A comprehensive analysis of the placement and use of forgings, the bending angle from 110. Change to 115. The inner radius of the bend is changed from 5mm to 10mm, which reduces the possibility of bending folds and eliminates the development of folds into hidden dangers. Also, curved slot designs are important when bending a mold design. After the bar is bent, the deformed area will appear elliptic deformation, should pay attention to whether the section after the bending depression occurs, if there is, we must promptly adjust the curved groove design, increase the tilt angle size, from 135. Added to 150.

4 Conclusion Through the analysis of the causes of the forging folded, and then improve the forging wool material and die size changes, so that the size of the forging is good, the surface of the forging and low-fold organizations are not folded, the mechanical properties of the forging are in line with the standard requirements, its quality is stable, like Stepped shaft, tooling improved design has been used in the production of all the crash design, the basic solution to the problem of folding the collapse of the shaft. For bending defects in bending forgings, it is important that the forging process and mold design must be reasonable and appropriate.

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