Problems in the production of metal special barrels (1)

Since joining the International Trade Organization, the market has become increasingly demanding on product quality, and packaging products have been particularly prominent. Because good products need to enter the international market, the first problem to be solved is the backward historical pattern of “one type of product, two types of price, and three types of packaging”. At present, the paper, plastics, wood and glass packaging industries in China are all in an extremely hot spot, and only the metal container packaging industry has not shrunk, especially the state-owned metal container packaging companies. Most metal container packaging companies are now miniaturizing their products. At present, the author discusses some of his own opinions on the common problems in the production of special-shaped metal drums in domestic enterprises.
At present, there are major problems: First, there are wrinkles at the four corners and leakage. The second is the direct weld leakage and leakage in the weld triangle.
In response to these problems, we mainly carry out technical analysis from the following aspects.
First, the impact of raw materials on product quality In general, the production of special-shaped metal cans are mostly tin plated steel. Tinned steel sheet is a kind of low carbon steel sheet with certain metal ductility and tin plated surface. The tin plating plates currently used for can making are tin plate plating. The production process of tin plating plates is: low carbon steel (molten steel)→casting steel ingots and blooming (or continuous casting)→slabs→hot rolling→strips → Pickling → cold rolling → electrolytic cleaning → annealing → leveling → trimming → electrolytic cleaning → tin plating → reflow → passivation treatment → oil coating → coiling → shearing → sorting → packaging (electroplating tin plate).
In order to meet the quality requirements of canning containers and adapt to the canning process, the process steps must be strictly controlled when producing tinplate plating. From the point of view of the production process of electroplated tinplates, the factors influencing their mechanical properties are not only related to their heat treatment but also to their rolling direction. These are discussed in the study of barrel flanging.
Second, the deformation of the bottom of the top of the deformation characteristics of the product quality from the shape of the geometric shape of the cans, its deformation and the circular tank parts of the deformation of a qualitative difference, the biggest difference is the drawing on the periphery of the Uneven deformation. We can divide it into straight edges with lengths A2r and B2r and four rounded corners with radius r (see Figure 1). The rounded part is a 1/4 cylindrical surface. Assuming that there is no connection between the straight edge portion and the rounded corner portion of the deformed member, the molding of the part can be assumed to consist of bending of the straight edge portion and deep drawing deformation of the rounded portion. However, since the straight edge portion and the rounded corner portion are integrated together, it is inevitable that there is a mutual effect and influence in the deep drawing process, so that neither of these two portions is a simple bending deformation. In fact, from the perspective of the nature of deformation, there is no clear demarcation between the two parts.
When the shaped piece is deepened, the deformation of the straight edge portion and the rounded corner portion is shown in FIG. 1 . Before deep drawing and deformation, the radius formed by radial rays and concentric arcs is drawn on the rounded part of the rough surface, while the straight edge part is drawn into a grid composed of mutually equal equidistant equal lines. If the straight edge portion of the deformed member is only deformed by bending, the grid lines on the side surface of the deformed member after deep drawing deformation should be exactly the same as those before the deformation. However, in fact, the grid size of the side wall of the deformed member undergoes a change in lateral compression and longitudinal elongation after deep drawing deformation. The lateral dimension before deformation is ΔL1 = ΔL2 = ΔL3, and the relationship after deformation becomes ΔL1> ΔL1> ΔL2> ΔL3.
The longitudinal heart-inch before deformation is H1 = â–³H2 = â–³H3, and after deformation it becomes the relationship of â–³H3> â–³H2> â–³H1> â–³H1. From this dimensional change, it can be seen that the laterally compressed and longitudinally stretched tensile deformations are not uniform on the sidewalls of the straight part of the profiled part. In the middle part of the straight edge part, the deep drawing deformation is the smallest, and the deep round part of the deep drawing deformation is the largest. The distribution of deformation in the height direction is also non-uniform. It is the smallest in the near bottom position and the largest in the near upper opening. The deformation of the radiused part is similar to that of the cylindrical part, but its degree of deformation is smaller than that of a cylindrical part with the same radius and height. Therefore, radial radiation on the plate blank does not become an equal-distance line perpendicular to the bottom plane after deep drawing deformation, but becomes an oblique line with a small upper distance and a large lower distance.
The above-mentioned various phenomena indicate that due to the presence of the lateral compression deformation of the straight edge portion, the degree of deep drawing deformation of the rounded portion and the degree of hardening caused by the deformation are reduced, which is lower than that of a cylindrical member having a diameter of 2r and a height of H. . Therefore, the radial tensile stress necessary for tensile deformation in the deformed area of ​​the fillet portion is also lower than that of the cylindrical part of the same size. The influence of the straight edge portion on the rounded corners is determined by the ratio r/B of the fillet radius r to the width B of the profiled part, or the relative fillet radius. The smaller the ratio r/B, the more pronounced the influence of the straight edge portion on the deformation of the rounded portion, that is, the greater the deformation of the rounded portion and the difference of the cylindrical member. When r/B = 0.5, the profiled part becomes a cylindrical part, and the above-described deformation difference does not exist.
On the other hand, since the longitudinal elongation of the straight edge portion is smaller than the rounded portion, the straight portion of the straight edge portion at the bottom portion of the hair has the same movement speed as the rounded portion, but the straight portion is in the deformation region (the flange portion of the blank). The displacement speed is larger than the rounded part. This difference in displacement speed causes the straight edge part in the deformation area to act on the rounded part. As a result, the bottom part of the side wall of the rounded part, that is, the tensile stress value inside the dangerous section. Have decreased.
Third, the bottom of the bottom of the blank shape and size of the blank to determine the impact on product quality When the profiled parts deepen, the correct definition of the shape and size of the blank, not only can save the plate and get the mouth flush parts, but also conducive to Blank deformation and guarantee the quality of parts. When the size of the blank is too large, the tensile stress on the dangerous section will unnecessarily increase, which will increase the degree of deformation and reduce the disadvantage of the process. When the local size of the blank is too large, this part will protrude from the deformation area during the drawing process. Going out not only reduces the deformation of the protruding part itself, but also makes it difficult to deform the sheet material in the adjacent part. The reduction in the degree of deformation of the oversized part of the blank will inevitably cause the deep drawing deformation to concentrate more on the rest of the part, thus increasing the degree of uneven distribution along the periphery of the blank. This results in uneven wall thickness of the parts, and it also easily causes local deformation (such as four rounded corners) in the excessively concentrated part, which reduces the quality of the parts.
The principle of determining blanks when deep-drawing parts are deepened is also to ensure that the gross area of ​​the defect is equal to the area of ​​the part, but the bad shape of the hair must ensure that the distribution of the material on the entire periphery is exactly in line with the contours of each point on the periphery of the part. Side wall needs. Since the values ​​of the tangentially compressive deformation and the longitudinally elongated deformation of the metal at each point on the periphery of the part are not the same, it is necessary to consider the shape and size of the broken hair during the deformation process according to the uneven deformation characteristics of the shaped part. Necessary corrections.