Analysis of Quality Problems in Drum Delta of Steel Drum(2)

Second, the impact of the size of the bucket body blanking - overlapping wrong side

In production, a large amount of leakage in the delta region was sometimes found. When we cut the curled section on both sides of the weld, we found that the weld was completely different on both sides. as shown in picture 2. One side of the roll is better, while the other side is extremely unsatisfactory, there is a clear lack of size flanging, so that the side of the weld curled triangle side leakage.

In order to find out the root cause of the problem, we unrolled the bead between section A and section B, and found that there was a side-to-side phenomenon in seam welding, as shown in Figure 3. After we performed the same dissection on the other end of the barrel weld, we did not find the phenomenon of misalignment. From this point of view, the problem was in the process of blanking the barrel plate.

In the barrel blanking process, the general requirements for dimensional tolerances are more stringent, not only the size of the long and wide can not be exceeded, but also have certain requirements for the diagonal error, and also require that the four corners are evenly angled, these requirements are indispensable As shown in Fig. 4, three different blanking shapes are shown in Fig. 4(A). The side length ab = cd, ac = bd satisfies the length and width dimensions without exceeding the difference, but due to the diagonal ad Cb, so the shape of the cutting into a parallelogram, of course, the corners are not right angles, such a barrel body material will be formed after the seam as shown in Figure 5 (A) of the wrong side; in Figure 4 (B), The diagonal ad=cb has a side length ac=bd. However, the other side is ab≠cd, and the corners are not right-angled. The shape of the cutting material becomes an isosceles trapezoid. After the barrel material is welded, it forms a lap joint with a wrong side as shown in Fig. 5(B); in Fig. 4(C) Although there are two corners that are right-angled, the other two corners are not guaranteed, so that a lap-joint side is formed as shown in FIG. 5(C).

In actual production, we found that some of the raw materials (oil barrels) are more formal, and can be achieved simply by cutting a knife. However, some materials are not formal and require two, three, or even four cuts to meet the process requirements. In the blanking process, do not blindly cut in order to save trouble regardless of process requirements, on the one hand to make a positioning device for shears, on the other hand, we must always check whether the shape and size error meets the requirements, try to avoid overlapping error The situation on the side.

Third, the impact of edging quality - too thick

In the analysis of triangular quality problems, sometimes in the cross-sections on both sides of the weld as shown in Figure 2-1, it is found that the curls have loose edges and large crevices, but in the non-triangular areas No curling problem was found in other curled sections. So how are the gaps on both sides of this weld formed? In order to find out the real reason, we cut a section C in the center of the curl along the direction perpendicular to section A and section B (as shown in Figure 2-2), and found that there are large gaps on both sides of the weld, as shown in Figure 6 As shown.

The gap in the triangle area has a direct relationship with the thickness of the weld seam. The thickness of the weld seam depends on the quality of the milling process. One of the purposes of edging is to thin the seam weld to make the seam thickness thinner. Not too large. However, for most edging equipment, the edging thickness is not easy to achieve the desired requirements. In general, the thickness of a 1.2 mm thick barrel plate is about 1 mm after one-sided thinning. After double-lap joint seam welding, the total overlap thickness is about 2 mm, which is much greater than the thickness of the raw material. In this way, the gap in the triangle area appears.

To solve the problem of excessive edging thickness, there are many ways. In addition to increasing the amount of edging, it is also possible to use automatic seam welder welding, or to adopt new technologies developed in recent years in China, such as edge milling technology, Grinding technology, seam welding equipment and so on.

Why can we solve the problem of rapid weld thickness with a fully automatic welder? It turns out that in the welding process of full-automatic welders, the welding seam is narrow, usually only 3 mm, and the welding wheel is wide, about 20 mm. Therefore, in the welding process, the welding seam is completely covered by the welding wheel. Among them, under the effect of the pressure of the upper and lower welding wheels and the resistance heat, the entire lap melts completely to form a relatively thin weld. The maximum thickness is generally about 1.3 mm, which is not much different from the thickness of the barrel body plate 1.2 mm. Therefore, the full-automatic welder has a small gap in the weld fillet triangle area, and the possibility of leakage is small. The manual semi-automatic welder welding wheel used by most domestic manufacturers is narrow, about 6-8 mm, and the welding seam has a wide margin of about 12 mm, so when welding, under the effect of the pressure of the welding wheel and resistance heat There will be a phenomenon in which the middle part of the weld seam is melted and the outer edges of both sides are curled. The thickness of this location is usually about 2-2.5 mm. This dimension is much larger than the thickness of the barrel body plate, so the curl clearance is large, as shown in Figure 7. For automatic welder and semi-automatic weld cross-section comparison.

The edge milling process is to change the grinding method of the grinding wheel to a new milling process using a milling cutter disk. It is easy to make the single-edge milling thickness to a more ideal size, and the edge grinding process is to use the welded seam after welding. A new technique for laminating equipment is thin seams. Seam welding equipment is to convert semi-automatic seam welding machine into a fully automatic welding machine, which can also achieve the purpose of small laps and thin welds.