Weld quality failure of high frequency straight seam welded pipe unit
Long lap welding
Lap welding refers to the dislocation bonding formed after the two edges of the tube blank are stacked together. In terms of length, lap welding can be divided into long and short. The general length of lap welding is generally a few meters or even longer. In terms of dislocation, there is a slight dislocation of a few tenths of a millimeter, and there is a complete dislocation equal to the wall thickness. The main reasons for long lap welding are as follows:
1 Axial movement of squeeze roller
Due to the unstable positioning of the squeeze roller and the squeeze roller shaft, as well as the openness of other zero parts during assembly, the squeeze roller will move axially and oscillate in the radial direction. The pass of the squeeze roller will not match and cause lap welding.
2 Bearing damage
After the bearing is damaged, the normal position of the squeeze roller will be destroyed. Take the two-roller squeeze roller device as an example. Generally, there are two sets of upper and lower bearings in the squeeze roller. When one of the squeeze rollers is damaged, the squeeze roller loses control, and the weld seam will rise higher and cause lap welding. During production operation, we can observe the swing of the squeeze roller. When the upper end bearing is damaged, the swing range of the roller is larger, and when the lower end bearing is damaged, the swing range of the roller is smaller. At the same time, it has a certain relationship with the degree of bearing damage.
After the bearing of the guide roller is damaged, not only can it not well control the direction of the weld seam of the tube blank, but the guide ring may also cause pressure loss on the edge of the tube blank due to the damage of the bearing, which will change the height of the weld seam, which is slightly inappropriate. There will be lap welding accidents.
3 Bending of the squeeze roller
Still taking the two-roller squeeze roller device as an example, there are two reasons for the bending of the squeeze roller shaft: one is the external bending due to insufficient top wire pressure for a long time; the other is the internal bending when the top top wire pressure is too high. When checking, release the top tightening device and place the vertical surface of the steel ruler on the end face of the roller to check the inclination angle between the end face of the other roller and the steel ruler. When the shaft is bent outside, the scratches are caused by the rollers of the bent shaft; when the shaft is bent inside, the scratches are caused by the rollers that do not bend the shaft.
4 Large squeezing force
Overlap welded pipes caused by excessive extrusion force generally occur in the production of thin-walled pipes, and rarely occur in the production of ordinary thick-walled pipes. This is because in the production of thin-walled tubes, due to the poor rigidity of the tube blank, once the extrusion force is too large, the width of the tube blank can not be accepted after too much margin in the pass, and it will be transferred to other parts. Space movement forms lap welding. Therefore, when designing the pass, it is necessary to select the appropriate pass radius and roll gap allowance according to different pipe wall thicknesses, and at the same time, pay attention to adjusting the amount of extrusion appropriately. To
5 The guide roller is tilted
Under normal circumstances, the guide roller should be in a horizontal position. In order to better control the weld seam, the guide roller can be tilted. If the inclination angle is too large, the extension of the guide ring will be large. With the rotation of the guide roller, the roller ring will press the edge of the tube blank to deform abnormally, especially when the thin-walled tube is produced, it is easier to promote the lap welded tube. produce. Often the large tilt adjustment of the guide roller is because it cannot well control the direction of the pipe seam. Therefore, when the guide roller has a large hole pattern, it is necessary to replace the new roller in time, check and adjust immediately when the center is not correct, and try to avoid large tilt adjustments.
6 The bottom diameter of the guide roller is different
If the bottom diameters of the two holes of the upper guide roller are not the same, the problem of lap welded pipes is also prone to occur, especially in the production of thin-walled pipes, this phenomenon is more likely to occur. When the machine is stopped for inspection, you can feel whether the welding seam of the welding V-shaped zone is smooth by touching it with your fingers. Of course, as long as we strictly control the quality of the rollers, this lap 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 and stainless steel composite welde
