Factors that cause weld quality failures in used round tube forming machines include ①lap welding. ②cycle lap welding.③opening. ④bathholes. The following is an introduction to the factor that causes the quality of the weld-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 the long lap welding in the used round tube forming machines are the following factors:

(1) The squeeze roller moves axially. 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) The bearing is damaged. After the bearing is damaged, the normal position of the squeeze roller will be destroyed. Take the two-roll squeeze roller device as an example. Generally, two sets of bearings are installed 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. In the production run, we can observe the swing of the squeeze roll. When the upper end bearing is damaged, the swing range of the roller is larger. 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 to the edge of the tube blank due to the damage of the bearing, causing the weld height to change, which is slightly inappropriate. There will be lap welding accidents.

(3) The squeeze roller is bent. 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. During inspection, release the top tightening device and place the vertical surface 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 scratches are caused by the rollers of the bending shaft; when the shaft is bent inside, the scratches are caused by the rollers that do not bend the shaft.

(4) The squeezing force is large. 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 hole pattern, and it will be transferred to other parts. Space movement forms lap welding. Therefore, when designing the pass, the appropriate pass radius and roll gap should be selected according to different tube wall thicknesses, and at the same time, the amount of extrusion should be adjusted appropriately.

(5) The guide roller is inclined. 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 shape, 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 guide upper roller are not the same size, the problem of lap welded pipes is also prone to occur, especially when thin-walled pipes are produced, this phenomenon is more likely to occur. When shutting down 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.

Due to the above six factors, the quality of the weld in the used round tube forming machines is caused by lap welding. When the welded pipe is made, it is necessary to check whether the used round tube forming machines has these problems.