Analysis of common technical problems in the produ

2022-08-07
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Analysis of common technical problems in the production of metal special-shaped cans (II)

2 Manufacturing process of resistance welding can

the can body is generally round during welding. The manufacturing process of the tank body is as follows: iron printing → blanking (plate cutting) → rounding → welding → touch up coating → drying → bulging → flanging → capping → inspection

the sheet used in the resistance welding can must be left with a certain width of printing blank at the welding position, which is called "blank" to avoid the impact of printing ink on the welding quality. This process requires high precision, because inaccurate blanking will directly affect the welding quality of the weld

the flat sheet is fed by the transfer roller, and the sheet is repeatedly bent by the bending device composed of several rollers and guide blocks to eliminate the internal stress, which is called softening. After the softened sheet enters the rounding device, it is rolled into a cylindrical shape under the action of the wedge and the cylinder groove (see Fig. 4). The rounding device can be adjusted to form different tank diameters

the rolled cylinder is pushed into the beginning of the positioning guide rail (i.e. Z-shaped rod) by the conveyor chain (see Fig. 5, omitted). The Z-shaped rod guide groove gradually transits from a in the figure to B at the Z-shaped rod outlet. During the propulsion process, both sides gradually approach. When it is about to enter the electric welding roller, both sides of the tank overlap, and the overlap amount is the specified value. Then the stopper of the transmission chain pushes the tank into the upper and lower electrode rollers for welding

when welding, the two overlapping edges of the can body to be welded are placed between the upper and lower welding rollers. In order to prevent the tin on the tinplate from sticking to the edge of the roller, the copper wire moving synchronously with the can body is used as the intermediate electrode to remove the tin splashed from the welded sheet. The copper wire is wound in the electrode roller groove (see Fig. 6, omitted) to transmit the welding current and voltage to the tank body weld. Therefore, the copper wire is required to have high conductivity and thermal conductivity; The copper wire is subject to tensile force and requires high tensile strength; It is also required that the surface be clean without oxide film and oil stain, otherwise, breakdown and copper wire sticking may occur. Used copper wires can be recycled and reprocessed. In order to keep the roller in good contact with the power supply, the wheel is filled with mercury. In order to prevent the roller from overheating and deformation, circulating water is used to dissipate heat in the wheel (see Fig. 7 omitted)

in addition, welding pressure, current, welding speed and other parameters will affect the welding quality of the tank body

for the welded tank body, the weld surface is oxidized and blackened. In order to prevent the corrosion from the contents and atmospheric corrosion, the tank body should be immediately sent to the touch up mechanism to apply a layer of quick drying paint on the weld. The can body after coating is sent to the dryer for drying and cured at 280 ℃ for 10s

3. Quality inspection of resistance welding can body

1 Appearance quality inspection

no tank leakage, tank expansion and other phenomena

the tin layer on the outer wall of the tank is complete without obvious rust and scratch. The tank body is smooth without obvious edges and corners

the main patterns and words printed on the outside of the tank shall be clear without serious scratch and damage

the whole weld shall be smooth and beautiful, with uniform lapping, uniform connection of welding points, and no poor welding and breakdown

the welding touch up tape shall be smooth and uniform, completely cover the weld and the empty part of the coating, completely cured, and free of large bubbles and iron dew points

the tank body shall be free from serious collapse caused by mechanical collision

the dislocation of both sides of the weld end shall be less than 0.5mm, and the tailing of the weld end shall be less than 0.5mm

the paint on the inner wall of the tank shall not fall off

the inner wall of the tank shall not produce iron sulfide

2. The performance inspection of welds

requires that the tensile strength of welds shall not be lower than the tensile strength of tank body plate. The tear test is relatively simple. It is widely used in production at present. The method is to cut along one side of the tank weld, bend the part away from the tank weld upward, and clamp the part with pliers to tear along the weld (see Fig. 8). For good welds, the weld crater shall be smooth after tearing, and it is qualified if the weld does not peel off

v. influence of special-shaped tank body flanging on its product quality

before flanging, the special-shaped tank must first be bulged to expand its approximate shape, and then flanging. Flanging plays an important role in the subsequent sealing (capping) process, because the tightness of the tank depends on the sealing degree of the tank body and the tank cover. For high-quality sealing, the flanging of the tank body is particularly critical

for the special-shaped tank in actual work, the tank edge is generally bent. When the tank body enters the flanging die, the outer die holds the tank body tightly, and the inner die pushes the tank body outward to flanging. During flanging, the four straight edges are bent and deformed, and the material has no elongation and shortening; At the four fillets, the material belongs to the extended flanging, so this problem should be paid attention to when designing the flanging die. In general, the flanging width at the fillet is 0.8 ~ 1mm less than that at the straight edge, so that there will be no creases at the fillet after flanging, which is conducive to the smooth sealing

it can be seen from the production process of raw materials that thin plates are obtained by rolling. From the principle of plastic deformation of materials, it is known that the thin plate has certain directionality during rolling, and the longitudinal and transverse mechanical properties are different. Therefore, during blanking and layout, it is generally required that the rounding direction of the tank body is consistent with the rolling direction (i.e. longitudinal), and the flanging direction is vertical to the rolling direction (see Fig. 9). Because the stress during flanging is large, such orientation can make the stress direction follow the rolling direction with high mechanical properties and prevent flanging cracks

VI. influence of sealing on product quality

double edge curling is adopted for the sealing of the tank body and bottom (top) of the special-shaped tank. Because the distance between the pressure head center of the special-shaped tank and the tank edge is variable, the tank body is generally fixed, and the roller rotates around the tank edge to form a double curling. (see Fig. 10 for the formation process.)

the key to double crimping is the roller, which is divided into the first roller and the second roller. Its overall dimensions are basically the same, but the shape of the "roller" groove is different. Determine the groove curve of roller according to the needs of crimping operation. The head roller mainly makes the cover hook of the tank cover bend down to the flange of the tank body, and curl it together with the flange of the tank body to hook each other. The double crimping is basically finalized, so the upper bending ring of the groove curve is large, which is convenient for the cover hook to continue bending and gradually hook up with the flange of the tank body. The second roller is used to flatten and compress the preliminarily finalized curling to achieve the final shape of curling and ensure the smoothness and beauty of curling. Therefore, the upper bending of the groove curve is large and the lower bending is small

the following defects are most likely to occur during sealing, thus affecting the internal and external quality of the product

1. Fake roll. Refers to the curling where the folded cover hook tightly presses the folded body hook, but does not hook with each other. As shown in Figure 11 (omitted)

2. Big collapse edge. It refers to that the tank body and the tank cover are not connected with each other due to serious collision and shrinkage at the tank body flanging or the edge of the tank cover, and there is obvious flanging at the lower part of the flanging. As shown in Figure 12 (omitted)

3. Sharp edges and sharp edges. The sharp edge on the inner side of the crimping top is called sharp edge. When the sharp edge reaches the breaking degree of the tinned steel sheet, it is called fast edge, as shown in Figure 13 (omitted)

4. Incomplete crimping. It refers to the phenomenon that the local crimping is not fully compressed due to the slipping or poor rolling rotation of the indenter during the can sealing process, as shown in Figure 14 (omitted)

5. Skip (skip). It refers to the phenomenon that due to the thick curling at the weld, the roller skips over the weld and fails to compress the curling, as shown in Figure 15 (omitted)

6. Crimp "teeth". It means that the can is poorly sealed, the cover hook and body hook are not overlapped locally, and the V-shaped protrusion is formed at the lower edge of the crimping, as shown in Figure 16 (omitted)

7. Iron tongue and drooping lip. Due to poor sealing, the iron tongue shaped part visible at the lower edge of crimping is called iron tongue, as shown in figures 17 (omitted) and 18 (omitted)

8. The roll seal is broken. It means that the can is poorly sealed and the outer iron sheet of the crimping is broken, which usually occurs at the joint of the can body, as shown in Figure 19 (omitted)

9. Packing extrusion. It refers to the phenomenon that the sealant is exposed at the lower edge of the crimping at the tank

10. Double line. The double linear shape of the lower edge of the edging rolled by the sealing roller obviously damages the rolling mark of the tin layer

from the above analysis, these technologies have overcome the technical bottleneck of bio based chemical fiber and raw material industrialization; Bio based synthetic fiber needs to break through the industrialization of bio based synthetic fiber raw materials. All technical factors may directly affect the final quality of products. Therefore, in the production process, only pay attention to each process. 5. In order to protect personal safety, strictly control the process quality according to ISO9000 standards, can qualified products be obtained

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