Analysis of quality problems in the sealing triang

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Analysis of the quality problems of the steel barrel sealing triangle area (II)

IV. The Influence of the quality of spot welding positioning on the overlap is out of tolerance

sometimes, the leakage of some triangle areas is also caused by the problem of spot welding positioning before the seam welding of the barrel body. Due to inaccurate positioning, the shape of lap weld often formed is shown in Figure 8. The overlapping amount on both sides a and B of the weld is seriously out of tolerance, the overlapping amount on side a is too large, and the overlapping amount on side B is too small. When the lap amount is too large, the lap edge of the weld is separated too much, forming a double-layer without melting, as shown in the figure. In addition to the leakage caused by the thick weld (as shown in Figure 6), the curl formed by it also has the leakage caused by the gap in the middle of the double-layer edge, as shown in the figure. When the overlap is too small, there is often an opening phenomenon, and sometimes the weld is separated after flanging, which has been completely separated in the process of flanging. When flanging, the weld disengages as shown in the figure, and the resulting triangular crimping is shown in the figure. This will cause greater leakage

in order to prevent the overlap of seam welding from being too wide or too narrow, it is necessary to find a way on the positioning spot welding machine, adopt Z-shaped positioning fixture, and position at both ends of a and B at the same time. Only by controlling points a and B, can the positioning of both sides be consistent. The Z-shaped positioning fixture is shown in Figure 11. For the full-automatic seam welding machine, because it has a Z-shaped positioning guide rail, it does not need spot welding positioning, and the seam welding lap quality can also be strictly controlled

v. influence of seam welding quality (I) burn through

sometimes the cause of leakage is difficult to analyze, but as long as the triangle area is cut and unfolded, many problems will be found, such as the crimping shown in Figure 12. According to the analysis of the holes in the seam curling of the barrel body in the figure, it is found that the seam is perforated, which is seam burn through

considering the Lantern Exhibition and the activity of new year's celebration of the Lantern Festival with the theme of "turning waste into treasure, ingenious lantern making, smart campus exhibition style" held by xiao5tai primary school in Yingze District, Taiyuan City, product characteristics, utilization and meeting the requirements of durability, the causes of local burn through on the welding surface are generally as follows:

(1) the lap edge of the barrel body or the surface of the welding wheel is dirty

(2) insufficient electrode pressure or no real contact between the barrel body and the welding wheel

(3) the welding wheel surface loses its regular shape

(4) the welding speed of seam welding is too fast, and the welding wheel is overheated

if there is too much burn through in normal production, it should be strictly checked. For the first reason, the lap surface of the barrel body and the surface of the welding wheel should be cleaned; For the second reason, the electrode pressure should be increased and the welding wheel with excessive wear should be replaced; For the third reason, the welding wheel surface should be repaired; For the fourth reason, the cooling conditions should be improved. Generally, there are a few burn through phenomena in production, most of which are caused by the first reason

the welding machine has high current and low impedance, so the secondary voltage is low. In this way, oil stains and oxides on the barrel are all bad conductors. Under the action of electrode pressure, the oxide film is partially broken, and the distribution of current field on the steel plate is changed when conducting electricity, so that the current lines at individual parts are dense, and the heat is too concentrated, which is easy to cause burns at the lap joint or along the outer edge of the solder joint. This is the main cause of burns

VI. influence of seam welding quality (II) nozzle

in most bucket manufacturers in China, the phenomenon of seam welding nozzle is very common This is also one of the main reasons for the leakage in the triangle area As shown in Figure 13, the shape of the protruding nozzle appears on the seam welding edge. In the process of crimping, the protruding nozzle will first reach the crimping center, so that the flanging parts on both sides cannot be reached. However, the government led the plan to build system 1 Anyang trade market, which has insufficient crimping layer or gap. The crimping conditions of the protruding nozzle center and both sides of the protruding nozzle can be seen in figure and figure, and their crimping conditions are basically similar

there are generally three reasons for the phenomenon of seam welding protruding tip:

(1) the power on time is too long

(2) insufficient electrode pressure

(3) excessive current

for the protruding nozzle caused by the above reasons, it is generally solved by adjusting the welding specification, changing the cone angle of the end face of the welding wheel and improving the cooling conditions. Some are solved by edge cutting machine

VII. Influence of seam welding quality (III) desoldering

for the quick solution of the above weld nozzle problem, some manufacturers adopt the method of seam welding without end, resulting in the desoldering defect of seam welding without end. As shown in Figure 14, it is the schematic diagram of the weld with the fusion joint not reaching the end

the cross-sectional shape of the curling without the end of the weld seam is basically similar to that shown in the figure, and there are double edges at the curling of the barrel body. Then there is leakage, sometimes direct leakage. In the actual operation of seam welding, when the barrel body is not finished, raise the welding wheel. This happens when the welding is interrupted. Therefore, it is not difficult to solve this problem, as long as you pay more attention in the operation, that is, try to separate from the welding wheel when the weld reaches the end of the barrel body. Of course, there is no such problem with fully automatic welding machine

VIII. Influence of seam welding quality (IV) weld embrittlement

in the production of mass production and cleaning and drying treatment, sometimes flanging cracks occur when the raw materials are good, and some cracks are along the weld direction. There are cracks perpendicular to the weld direction, and the results after crimping are similar to those in Fig. 1 and FIG. This quality problem is generally affected by the quality of seam welding

there are generally four reasons for weld embrittlement:

(1) too long power on time, overheating, and melting of grain boundaries. The improvement measures are: adjust the specification parameters

(2) insufficient electrode pressure or untimely pressure increase. The pressurization speed of the welding machine should be maintained

(3) short power on time, excessive cooling speed, and quenching cracks. Select appropriate welding cycle form

(4) the surface is poorly cleaned or splashed in a large amount. The surface cleaning of the barrel edge should be strengthened

according to the investigation, the cooling method used by many domestic manufacturers' semi-automatic seam welding machines is external cooling, some are internal and external cooling, and some are internal cooling. For internal cooling welding, because the cooling water circulates inside the welding wheel, the cooling speed is generally not too large. External cooling welding method is used. It is easy to produce quenching cracks with excessive cooling speed. This is the main cause of weld embrittlement

for quenching cracks. The external cooling mode of welding roller should be canceled. Strengthen the cooling water flow and flow rate of internal cooling to meet the cooling requirements and avoid weld quenching fracture

IX. influence of sealing quality on iron tongue and extrusion

as shown in Figure 15, iron tongue in triangular area often appears in steel barrel crimping. In addition to the influence of too thick weld, the curling quality also has a great influence on this situation. The groove size of the crimping roller is designed according to the thickness of the steel plate, the number of crimping layers and the shape. Generally speaking, it is calculated according to the round crimping of seven layers. Groove depth and width of roller. It must be ensured that there are enough curls with seven layers of material thickness. If the roller groove is too large, the crimping will be loose and not compact, and the crimping size is too large, which is easy to cause the whole ring of crimping leakage; If the size of the rolling groove is too small, the material of seven layers of crimping cannot be filled in the groove, it will overflow, and the overflow will appear iron tongue

because the weld material of triangle area is generally thick. Is 1% of the thickness of raw materials 5 times. If the crimping of the rolling groove outside the triangle area is slightly small, there must be iron tongue phenomenon of excess material in the crimping of the triangle area. The iron tongue phenomenon not only affects the beauty of the steel barrel. The crimping is often crushed, resulting in leakage quality problems, as shown in Figure 16

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