How periodical lap welding happens

The Common Production Failure Analysis Of ERW Steel Pipe Unit-Periodical lap weldingPeriodical Lap welding refers to the intermittent appearance of lap welding. It happens,sometimes lap weld length slightly longer, a few centimeters or even dozens of cm, sometimes slightly shorter,  one or two cm.Sometimes lap welding occurs for relative regular equidistance, sometimes appears irregularly.For all these kinds lap welding phenomena, we collectively known as periodical lap welding.Periodic lap welding generally occurs in the later stages of production, mainly has the following reasons:(1) guide ring rupture. After sealing groove wear, it will not be able to effectively control the pipe run normally, making the tube billet swing in the groove. Once the guide ring breaks and appears gouges, the edge of the tube billet, in the process of running, will sag down by the guide ring gouges, finally forming the lap welding.The feature of such lap welding pipe is with same lap welding cycle length, strong regularity, and easy to judgment.Generally following the broken guide ring spinning, the trace of the sag can be found.(2) the groove wear. It mainly refers to the closed groove roller diameter position appears steps, as well as the open pass vertical roll pass department. When the tube billet swing in the pass and sliding towards the pass step parts, it will cause the tube billet deformation. The sag trace generated by the edge and finally form a lap welding. The best way to eliminate the lap welding tube, is to pay attention to the reasonable adjustment in normal production, make the groove wear uniform, avoid step, once find groove surface appears irregular shape, is about to change in time, to completely eliminate the generation of lap welding.(3) foreign body in the groove surface. Othe metal foreign bodies once attached to the groove surface for some reason, it may cause the tube billet surface generate sag sexual scar, and when the foreign body touching position is in the tube billet edge running track, it can cause short periodicity of equidistance lap welding. In general, this phenomenon is rare.(4) the side seam. In the late production, pass wear is more serious and control of the tube billet ability gradually decreased, and the center position of the groove is damaged by different degree. So, from the molding to welding, pipe will appear unstable phenomenon of side seam. And lap welding caused by side seam is mainly due to the reason of the vertical roll.When checking the conditions of the edge of the tube billet, it is hard to find anything abnormal and apparent defects under pressure, till to the squeeze roll can feel slightly difference of the height of the two edge of the pipe.By then,we should be paid attention to the top shape of the vertical roll pass. If it's ok, can increase the shrinkage of vertical roll, in order to obtain perfect tube billet deformation of edge effect, if the vertical roll shape of top of the groove is not very good, should reduce shrinkage of vertical roll, in case the cause of bad shape.(5) bearing damage. Once the sealing groove bearing is damaged, it can't well control the tube billet running smoothly, the phenomenon of side seam is likely to happen, and the possibility of lap welding followed. Especially after multichannel closed groove bearing damage, lap welding problem will become more serious, of course, this phenomenon is rare, even happen, this kind of lap weld was twitched irregular lap weld, adjust alone will not be able to solve the problem.