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Weld quality failure of high frequency straight seam welded pipe unit
Release time:
2018-12-06 13:59
Lapping refers to the dislocation bonding formed after the two edges of the tube blank are stacked together. In terms of length, lap welding is divided into long and short, and the through-long lap welding is generally several meters or even longer.
through-long lap welding
Lapping refers to the dislocation bonding formed after the two edges of the tube blank are stacked together. In terms of length, lap welding is divided into long and short, and the through-long lap welding is generally several meters or even longer. There is a slight misalignment of a few tenths of a millimeter in the misalignment, and a complete misalignment equal to the wall thickness. The main reasons for the long lap welding are as follows:
1 Axial movement of squeeze roller
Due to the unstable positioning of the extrusion roller and the extrusion roller shaft, as well as the open amount formed by the non-tight fit of other zero parts in the assembly, the extrusion roller will have axial movement and radial swing, and the hole pattern of the extrusion roller will not match and cause lap welding.
2 Bearing damage
When the bearing is damaged, the normal position of the squeeze roller will be destroyed. Taking the two-roller squeezing roller device as an example, the upper and lower two sets of bearings are generally installed in the squeezing roller. When one of them is damaged, the squeezing roller loses control, and the welding seam will be higher and cause lap welding. In the production run, we can observe the swing of the squeeze roller. When the upper bearing is damaged, the swing amplitude of the roller is larger, and when the lower bearing is damaged, the swing amplitude of the roller is smaller, and it also has a certain relationship with the degree of bearing damage.
After the bearing of the guide roller is damaged, it not only cannot control the weld direction of the tube blank well, but also the guide ring may cause pressure damage to the edge of the tube blank due to the damage of the bearing, causing the height of the weld to change, and a lap welding accident will occur if it is slightly inappropriate.
3 Bending of extrusion roller shaft
Still taking the two-roller squeezing roller device as an example, there are two reasons for the bending of the squeezing roller shaft: one is the external bending due to insufficient pressure of the upper jacking wire for a long time; The other is the internal bending when the pressure of the upper jacking wire is too large. When checking, release the jacking device, and place the elevation of the steel ruler on the end surface of the roller to check the inclination angle between the end surface of the other roller and the steel ruler. When the shaft is bent outside, the scratch is caused by the roller of the bent shaft; when the shaft is bent inside, the scratch is caused by the roller of the non-bent shaft.
4 Large extrusion force
The lap welded pipe caused by excessive extrusion pressure generally occurs in the production of thin-walled pipes, and rarely occurs in the production of ordinary thick-walled pipes. This is because in the production of thin-walled tubes, due to the poor steel degree of the tube blank, once the extrusion force is too large, the width of the tube blank in the pass can not be accepted, it will move to other space to form a lap weld. Therefore, in the design of the pass, the appropriate radius of the pass and the amount of roll gap should be selected according to the wall thickness of the different pipes, and at the same time, attention should be paid to the appropriate adjustment of the amount of extrusion.
5 Guide roll tilt
Under normal circumstances, the guide roller should be horizontal position, in order to better control the weld, the guide roller can do tilt adjustment. If the inclination angle is too large, the extension of the guide ring is large, and with the rotation of the guide roller, the roller ring will press the edge of the tube blank to deform differently, especially in the production of thin-walled tubes, it is easier to promote the production of lap welded tubes. The large tilt adjustment of the guide roller is often due to its inability to control the direction of the pipe seam. Therefore, when the hole type of the guide roller is large, the new roller should be replaced in time, and the center should be checked and adjusted immediately when the center is not large, so as to avoid large tilt adjustment.
6 The bottom diameter of the guide upper roller is different.
If the bottom diameter of the two holes of the upper guide roller is not the same, it is also prone to the problem of lap welded pipe, especially in the production of thin-walled pipes, this phenomenon is more likely to occur. When stopping for inspection, you can feel whether the weld in the V-shaped area is flat by finger touch. Of course, as long as we strictly control the quality of the roller, this welding phenomenon can be overcome.
Jiangsu Nanyang Machinery Manufacturing Co., Ltd. specializes in the design and manufacture of various types of high-frequency welded pipe units, stainless steel precision welded pipe units, high-precision steel-plastic, stainless steel composite welded pipe units; design and manufacture of various specifications and models of welded pipe molds-rollers, special-shaped rollers, So that the products formed a series, in the majority of domestic and foreign merchants enjoy a high reputation.
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