Long lap welding
The lap welding refers to the misalignment bond formed after the two sides of the tube blank are stacked together. In terms of length, the lap welding has a length and a length, and the long lap welding is generally several meters or even longer. There is a slight misalignment of a few millimeters in the misalignment, with a complete misalignment equal to the wall thickness. The main reasons for the long lap welding are the following factors:
1 Squeeze roller axial movement
Due to the unstable positioning of the squeezing roller and the squeezing roller shaft, and the amount of enthalpy formed by the non-compacting of other zero parts during assembly, the squeezing roller is axially swayed and radially oscillated. The hole shape of the squeezing roller does not match and causes lap welding.
2 bearing damage
When the bearing is damaged, the normal position of the squeezing roller is destroyed. Taking a two-roller squeeze roll device as an example, two sets of upper and lower bearings are generally installed in the squeeze roll. When one set is damaged, the squeeze roll is out of control, and the weld bead is raised to cause lap welding. In the production run, we can observe the swing of the squeeze roller. When the upper end bearing is damaged, the swinging amplitude of the roller is larger. When the bearing at the lower end is damaged, the swinging amplitude of the roller is smaller, and at the same time, it has a certain relationship with the degree of bearing damage.
After the bearing of the guide roller is damaged, it not only can not control the weld direction of the tube blank well, but also the guide ring may cause pressure loss on the edge of the tube blank after the bearing is damaged, so that the weld height changes, which is slightly inappropriate. A lap weld accident will occur.
3 Squeeze roller shaft bending
Still taking the two-roller squeeze roll device as an example, there are two reasons for the roll bending of the squeeze roll: one is an outer bend in which the pressure of the top wire is insufficient for a long period of time; and the other is an inner bend when the pressure of the top wire is too large. During the inspection, the topping device is released, and the elevation of the steel ruler can be placed on the end face of the roller to check the inclination angle of the end face of the other roller and the steel ruler. When the shaft is bent out, the scratch is caused by the roller of the curved shaft; when the shaft is bent, the scratch is caused by the roller that does not bend the shaft.
4 large pressing force
The lap welded pipe caused by the excessive pressing force 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 steelness of the tube blank, once the pressing force is too large, the width of the tube blank is too large to be accepted in the hole type, and it will not be accepted. The space moves to form a lap weld. Therefore, in the hole design, the appropriate hole radius and roll gap should be selected according to different pipe wall thicknesses, and at the same time, the amount of extrusion should be adjusted appropriately.
5 guide roller tilt
Under normal conditions, the guide roller should be in a horizontal position. For better control of the weld, the guide roller can be tilted. If the inclination angle is too large, the amount of protrusion of the guide ring is large. As the guide roller rotates, the roller ring will compress the edge of the tube blank, especially when the thin-walled tube is produced, it is easier to promote the lap tube. produce. The large tilt adjustment of the guide rolls is often due to the fact that they do not control the direction of the pipe joint well. Therefore, when the guide roller hole type is large, it is necessary to replace the new roller in time, and the center is not checked immediately to check and adjust, and try to avoid a large tilt adjustment.
6 Guided upper roller bottom diameter is different
If the diameter of the two holes of the upper roll is not the same, the problem of the lap welded pipe is likely to occur, especially in the production of thin-walled pipes, which is more likely to occur. During the stop inspection, you can feel the weld of the welded V-shaped area by finger touch. Of course, this lap welding phenomenon can be overcome as long as we strictly control the quality of the rollers.
Jiangsu Nanyang Machinery Manufacturing Co., Ltd. specializes in designing and manufacturing various types of high-frequency welded pipe units, stainless steel precision welded pipe units, high-precision steel-plastic and stainless steel composite welded pipe units; designing and manufacturing various types of welded pipe molds – rolls and shaped rolls, thus The products have been serialized and enjoy high reputation among domestic and foreign merchants.