Analysis of Quality Problems in Steel Barrel Sealing Triangle Area (2)

Analysis of Quality Problems in Steel Barrel Sealing Triangle Area (2)

Yang Wenliang

Second, the impact of the size of the barrel body - the wrong side

In production, a large number of triangular areas are sometimes found to leak. When we cut the crimped section on both sides of the weld, we found that the sides of the weld were completely different. as shown in picture 2. One side of the roll is better, while the other side is extremely unsatisfactory, and the apparent flanging size is insufficient, so that the side of the weld bead triangle is leaked.

Figure 2 seam welding triangle and sectional view

In order to find out the root cause of the problem, we unfold the bead between the section A and the section B, and found that the seam weld has a wrong side, as shown in Fig. 3. When we made the same anatomy at the other end of the barrel weld, we did not find the wrong side. From this point of view, the problem was that it was in the barrel blanking process.

Figure 3 lapped wrong side

In the barrel blanking process, the dimensional tolerances are generally required to be strict. Not only the length and width dimensions can not be exceeded, but also the diagonal errors are also required. In addition, the four corners are evenly angled. These requirements are indispensable. As shown in Fig. 4, three different blank shapes, in Fig. 4(A), the side length ab=cd, ac=bd, satisfy the length and width dimensions, but the diagonal ad≠ Cb, so the shape of the blank becomes a parallelogram, of course, the four corners are not right angles, and such a barrel body seam is welded to form a lap joint as shown in Fig. 5(A); in Fig. 4(B), The diagonal ad=cb has a side length ac=bd. However, the other side is ab≠cd, and the four corners are not right angles, and the shape of the blank is changed into an isosceles trapezoid, and the barrel body is welded to form a lap joint shape as shown in Fig. 5(B); In the case where there are two corners which are right angles, the other two corners are not guaranteed, so that the lap joints in the form of Fig. 5(C) are formed.

Figure 4 Analysis of the causes of overlapping faults

In actual production, we found that some raw materials (oil barrels) are more formal, only need to cut a knife to meet the requirements, but some materials are not formal, you need to cut two, three or even four knives to meet the process requirements, so In the blanking process, you must not blindly cut the machine to avoid the process requirements. On the one hand, you must make the positioning device of the shearing machine. On the other hand, you should always check whether the shape and size error meets the requirements, and try to avoid the erroneous connection. The situation on the side.

Figure 5 Analysis of the type of lap joint

Third, the impact of the quality of the edge - the edge is too thick

In the analysis of the quality problem of the triangular zone, sometimes we found that the curling edge has a looser bead and a larger gap in the cross section of the weld as shown in Figure 2-1, but in the non-triangular zone. The problem of looseness of the curl was not found in other crimped sections. So how is the gap on both sides of the weld formed? In order to find the real reason, we cut a section C at the center of the bead along the direction perpendicular to section A and section B (Fig. 2-2), and found that there is a large gap on both sides of the weld, as shown in Fig. 6. Shown.

The gap between the triangles has a direct relationship with the thickness of the weld, and the thickness of the weld depends on the quality of the edging process. One of the purposes of edging is to thin the seam and make the thickness of the weld. Not too big. However, for most edging equipment, the thickness of the edging is not easy to achieve the desired requirements. Under normal circumstances, the 1.2 mm thick barrel plate is about 1 mm after being smeared on one side. After the double lap joint welding, the total thickness of the lap joint is about 2 mm, which is much larger than the thickness of the raw material, so that the gap of 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 can also be welded by a fully automatic seam welder, or a new process developed in recent years, such as milling technology. Grinding technology, seam welding machine and so on.

Why can I solve the problem of thick weld seam with a fully automatic welder? It turns out that during the welding process of the automatic welding machine, the weld seam is narrower, generally only 3 mm, and the welding wheel is wider, about 20 mm. Therefore, during the welding process, the weld seam is fully contained in the welding wheel. Among them, under the pressure of the upper and lower welding wheels and the resistance heat, the entire lap is completely melted to form a relatively thin weld, the maximum thickness of which is generally about 1.3 mm, which is not much different from the thickness of the barrel of 1.2 mm. Therefore, the gap of the weld seam of the fully automatic welder is small and the possibility of leakage is small. The manual semi-automatic welding machine welding wheel used by most domestic manufacturers is narrower, about 6-8 mm, and the weld seam edge value is wider, about 12 mm, so under welding, under the action of welding wheel pressure and resistance heat. There will be a phenomenon in which the middle of the weld is melted and the edges of both sides are curled out. The thickness of this position is about 2-2.5 mm, which is much larger than the thickness of the barrel, so the curling gap is large, as shown in Fig. 6. It is a comparison of the automatic welder and semi-automatic weld cross section.

Figure 6 Comparison of weld cross sections between fully automatic and semi-automatic seam welders

The milling process is a new process of changing the grinding method of the grinding process to the milling cutter. It is easy to make the thickness of the single edge milling to a better size. The milling process is to use the welded seam after welding. A new technology for the thinning of the edge grinding equipment, the seam welding machine device is to convert the semi-automatic seam welding machine into a similar automatic welding machine, which can also achieve the purpose of small edge and thin weld.