The unqualified welding seam of ERW pipe welding machine generally has the following reasons
1. The squeeze roller moves axially
Due to the unstable positioning of the squeeze roller and the squeeze roller shaft, and the opening of other parts during assembly, the squeeze roller will move axially and swing radially. Mismatched squeeze roller passes, resulting in 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, two sets of bearings are installed in the squeeze roll. When one of the squeeze rollers is damaged, the squeeze roller loses control and the weld seam rises, causing lap welding. In the production operation, we can observe the swing of the squeeze roll. When the upper bearing is damaged, the roller's swing is larger, and when the lower bearing is damaged, the roller's swing is smaller, and it has a certain relationship with the degree of bearing damage.
After the guide wheel bearing is damaged, not only the welding direction of the tube blank cannot be well controlled, but the guide ring may also cause pressure loss on the edge of the tube due to the damage of the bearing, which will change the height of the weld, which is a bit inappropriate. There will be lap welding accidents.
3. Squeeze roll bending
Still taking the two-roller pressing roller device as an example, there are two reasons for the bending of the pressing roller shaft: one is the external bending caused by the long-term insufficient top thread pressure; the other is the internal bending when the top thread pressure is too high. During inspection, loosen the top tightening device, place the vertical surface of the steel ruler on the end surface of the roller, and check the inclination angle between the end surface of the other roller and the steel ruler. When the axis is bent outward, the scratches are caused by the rollers of the bent shaft; when the axis is bent inward, the scratches are caused by the rollers of the unbent shaft.
4. Large squeeze force
Overlap welded pipes caused by excessive extrusion force generally occur in the production of thin-walled pipes, but 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 is unacceptable after the excess amount of the pass is left, and it will be lap welding in the form of spatial movement. Therefore, when designing passes, the appropriate pass radius and roll gap should be selected according to different tube wall thicknesses, and the amount of extrusion should be adjusted appropriately.
5. The guide roller is tilted
Under normal circumstances, the guide wheel 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 elongation of the guide ring will be large. With the rotation of the guide wheel, the roller ring will squeeze the edge of the tube blank to produce abnormal deformation, especially in the production of thin-walled tubes, it is easier to push the lap welded tube. Production. The large adjustment of the inclination of the guide roller is often because the direction of the pipe gap cannot be well controlled. Therefore, when the guide roller has a large hole shape, it should be replaced with a new guide roller in time. If the center is not correct, check and adjust immediately, 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 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 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.
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