At that time, the seam width of the welding seams of domestic seam welders was between 10-12 mm. However, when the imported fully automatic seam welder welded the steel barrels, the lap width was only 2-3 mm and after welding. Not only the appearance of the steel drum is beautiful and beautiful, but also it helps to ensure the quality of the drum seal, and also saves raw materials. The control panel uses direct dialogue between people and machines, and the operation method is simple and easy to learn. Although this kind of welder has so many advantages, due to the high price, most of the barrel makers can only be stunned. At this time, people of insight in the country were optimistic about this business opportunity and decided to develop and manufacture welding electric control boxes, which were installed on the domestic FN1-150-5 seam welding machine.
Through technological transformation, most of the steel tank seam welders do not need to spend too much money, and they can achieve the desire of seam welding edge width of 4 mm. Jiangsu Jiangyin Wuxing Copper Industry Co., Ltd. is one of them. Through the technical personnel's research, it quickly developed and manufactured the control box of the steel tank seam welder, and transformed the corresponding mechanical transmission part of the seam welding machine, supporting the FN1 produced by the company. -150-5 type seam welding machine, to achieve a narrow seam steel welding seam desire. This technology has been applied in many steel drum companies in China, but due to the lack of technology and experience, as well as the inexperienced operation of operators, etc., the quality of welded steel drums has not achieved the desired results.
The following is a discussion of some practical problems in the actual welding process of the FN1-150-5 steel tank seam welder.
problem:
1. The weld has blisters and leakage occurs.
2. The uneven wear of the welding wheel and the occurrence of grooves in the middle of the welding wheel directly affect the welding quality.
3. When the barrel body is seam welded and flanged, both ends of the barrel are cracked, and even a weld with a length of 100 mm is leaking.
4, the barrel body at both ends of the flange is not damaged, but after the ribs tendons cracking.
5. After the welding, there are flying spurs, affecting the appearance quality of the steel drum and the internal quality of the fully open barrel.
The above five issues are problems that many steel barrel companies often encounter in production. To this end, we have discussed the welding theory, mechanical principles, and practical operations on the basis of full practice.
I. Effect of Welding Current, Electrode Pressure, and Welding Speed ​​on the Weld Quality of Bucket
The welding principle of steel drums is resistance welding. Welding is the use of welding heat to melt the steel plates and press them together. Welding heat Q=I2Rt
Where: Q—heat generated; I—welding current; R—resistance between electrodes; t—power on time
From the formula, it can be seen that the factors influencing the welding quality of the barrel are the welding current, the resistance between the electrodes and the energization time, and the resistance between the electrodes is determined by the electrode pressure, and the welding speed determines the energization time. Therefore, the main process parameters affecting the welding quality are: welding current, electrode pressure, welding speed
1, welding current
The source of heat required to form a nugget by seam welding in the barrel is as described above, which is the amount of heat generated by the electric current passing through the resistance of the welding zone. Under other conditions given, the size of the welding current determines the penetration and overlap of the nugget. When welding steel barrels, the average penetration rate of nuggets is 30-70% of the thickness of the steel plate, and 45-50% is the best. In order to obtain a weld nugget overlap, the amount of nugget overlap should not be less than 15-20%.
When the welding current exceeds a certain value, increasing the current can only increase the penetration and overlap of the nugget without increasing the joint strength, which is not economical. If the current is too large, defects such as deep indentation of the barrel and burnout of the barrel weld will also occur. Therefore, the welding current should not be too large or too small, but should be controlled within a certain range.
2, electrode pressure
Electrode pressure has a significant effect on the total resistance R between the two electrodes during seam welding of the barrel body. With the increase of the electrode pressure, R significantly decreases, and when the electrode pressure decreases, R increases significantly. Therefore, the weld strength always decreases as the electrode pressure increases. While increasing the pressure of the electrode, increasing the welding current or extending the welding time can compensate for the effect of the reduction in the resistance, thereby maintaining the welding strength. The use of this welding condition is conducive to improving the stability of the welding strength and avoiding cracking at both ends and ring ribs after welding. If the electrode pressure is too small, it will cause splashing and also reduce the welding strength. At the same time, if the electrode pressure is too high, the indentation of the barrel will be too deep, and the deformation and loss of the welding roller (welding wheel) will also be accelerated. If the pressure is insufficient, fly spurs and a large amount of sparks are liable to occur, and the life of the welding rolling disk is easily burned due to the excessive contact resistance.
3, welding speed
The welding speed of barrel body is directly related to the thickness and material of barrel body material. The special steel barrels produced by different manufacturers are different in the welding parameters during welding, and are not listed here. In short, the welding speed determines the contact area between the barrel welding machine (welding wheel) of the bucket body seam welding machine and the barrel body, and the contact time between the welding wheel and the heating area (where the welding seam overlaps). When the welding speed increases, To get enough heat, the welding current must be increased. Excessive welding speed can cause burnout of the barrel surface and adhesion of the electrode. Therefore, even if the barrel seam welder currently has enough external cooling water, the welding speed cannot be too large and should be limited.
The following is a set of process parameters in a steel drum manufacturer's production for reference only. Because the welder's own precision, modification methods, controller accuracy and welding work environment, the use of raw materials, the operator's proficiency and other factors will have an impact on the barrel welding parameters.
Different welding current, electrode pressure welding results control welding thickness of 1mm drum special steel?
Welding current Welding speed Electrode pressure Welding quantity Qualified quantity Bar body pass rate 11.5 kA 2.5 m/min 0.21 MPa 450 415 90.22% 10.5 kA 2.5 m/min 0.19 MPa 460 458 99.57% 9.5 kA 2.5 m/ Min 0.17 MPa 445 413 92.81%It can be seen from the table that small fluctuations in the welding current and the electrode pressure have a great influence on the qualification rate of semi-finished steel drums. Therefore, the process parameters that have been found in the actual production process to meet the welding requirements are not changed when the material of the steel plate is not changed. ,unable to be changed.
Second, the welder mechanical part and spot welding process on the barrel body welding quality
The first five phenomena are produced. In addition to the effects of welding process parameters, the adjustment of the welder itself is also very important. Because under normal circumstances, in the welding of the barrel, the electrode pressure and welding speed are not frequently changed parameters, unless the material thickness of the welding barrel body has undergone great changes, this parameter will only change. When the material thickness of the welding barrel is 1.2 or 1.0, the electrode pressure and the welding speed may not be changed, and the welding quality of the barrel body may not be affected. However, if the bowl support rack is too high or too low, it directly changes the electrode pressure when the barrel is welded. If the bucket rack is too high, the electrode pressure increases, and the welded barrel will have obvious indentations. As we discussed before, as the electrode pressure increases, R decreases significantly. At this time, the welding heat generated by the welding will be reduced due to the decrease of the electrode resistance R, and the welding strength will also decrease with the increase of the electrode pressure, so that the leakage or flanging will be broken; if the bracket is too low, the electrode pressure Reduced, welded out of the barrel will produce a clear peach type, that is, the barrel outside the weld is too high, not a circular arc. At this time, the pressure of the electrode decreases, and R significantly increases. At this time, the welding heat generated by the welding will increase due to the increase of the electrode resistance R, resulting in burn-through or splash phenomenon, which will easily lead to leakage or cracking. Therefore, after checking the height of the barrel seam welding machine, the first step is to adjust the level, and use the level gauge to adjust the parallelism of the bracket frame to the level. If the two heads are uneven, due to the different electrode pressures, the welding strength at the ends of the barrel welds will be different, and they will leak or break. Secondly, it is to check whether the head of the seam welder is normal, sometimes the lower head swings or the upper head is lubricated to cause the lubricating oil to dry up, so that the upper head cannot be moved down to the position required by the process. These are the main factors that affect the barrel welding. Thirdly, check whether the size and solder joints of the two sides of the bucket body are correct. If the process requires the barrel to be welded with 4mm of matting and 4 solder joints, then the two ends must not have excessive errors. Otherwise, the end of the welded body will leak. Fourth, check whether the welding pressure is correct and whether the gas pipe or the valve has any leakage.
Third, the actual welding process should pay attention to the following matters
1. Select welding process parameters such as welding current, electrode pressure and welding speed. Cut about 20 centimeters of cold-rolled sheet about 10 centimeters in width, and then weld it according to the process requirements, and then perform seam welding. The welding speed is controlled at 2 to 3 m/min. The welding current is adjusted, and the electrode pressure does not flow until the current does not flow. Striking fire, clear traces of steel plate, uniform welding, no scratches on the surface, penetration rate of fusion nugget up to 40-60%, followed by actual welding of the barrel, no leakage after bulging forming at the edge of plate, at this time recording welding current , Electrode pressure and welding speed data, as the welding process parameters, as long as the material and thickness of the steel plate does not greatly change, adjust the welding current, electrode pressure and welding speed can be maintained unchanged.
2. Always use absolute alcohol to clean the weld slag on the surface of the welding wheel to avoid trachoma from the weld seam.
3, found that the barrel after welding the front edge of the crack occurs, the pre-press time is adjusted to 000 or adjust the position of the photoelectric detection, so that early detection and timely welding.
4, timely adjustment and replacement of the wheel correction wheel, so that the surface of the welding wheel in a timely manner to prevent the emergence of grooves. If grooves appear on the surface of the welding wheel and are larger than 1mm, they must be ground or flat on the lathe. Otherwise, the welded barrel body is prone to leakage after molding.
In short, seam welding quality is an important part of controlling the quality of steel drums. In the future, we will continue to summarize on the basis of continuous practice to explore the best welding technology and welding specifications for seam welding to ensure that the welds of steel drums do not leak.
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