Prewelding defect of longitudinal welded pipe on submerged arc welding

Modern straight seam submerged arc welding steel pipe (UOE, JCOE) in the manufacturing process have set up continuous welding process. Its role is carried out after forming the tube shape, forming the inner weld seam position and back in order to ensure that the steel pipe size and shape for pipe welding, welded pipe quality and production efficiency is increased. However, in the process of preweld homework, sometimes it will inevitably produce welding defects because of the influence of various factors. These defects are often directly lead to the production of steel tube submerged arc welding defects inside and outside, and thus improve the quality of straight seam submerged arc welding pipe must be good control welding quality. As presoldering own characteristics, welding on the back of homework often produce flash, burn through, wrong side slants, welding, welding (arc), the weld residual high too low or too high. The burning through, (arc) welding is easy to find and take timely repair welding repair, generally do not have great influence on the internal and external welding quality.

Internally the back weld seam quality, tracking and welding process stability will have a greater impact. Welding in the welding torch head generally equipped with a guide wheel to stabilize the welding head and guide track. When the guide wheel encountered within the groove weld, the welding head will suddenly rise, wire space (the wire length and spacing) and the arc length will change dramatically, which will cause the weld slag inclusion, incomplete fusion, outer surface welding forming defects such as bad. It is easy to deviate from the guide wheel groove center at the same time, make the weld. When arc burning to flash, arc will suddenly become shorter, short-circuit arc, even affect the normal welding. Thus, a flash may often lead to two inside weld defects. Besides, the wrong side of the internal and external weld penetration and cross-sectional geometry will have a negative impact on the wrong side of tolerance will lead directly welded demotion or retirement. Meanwhile, the partial welding, weld reinforcement is too low, which is generated within the welding burn, cracks and other defects of the main factors. More than partial welding and high low is essentially back weld thickness decreases or no back weld serious welding (partial), at the same time, it also will cause the decrease of strength of forming seam at home, so in burn and cracks easily when welding defects. Outside the weld residual high is too high will cause the weld depth and weld ultra-high.

Straight seam welded steel pipe Pre-and outside submerged arc welding defects will directly affect the quality. Through the bevel angle and size, tube shape, weld zone cleanliness, welding materials, welding parameters, methods of operation, welding and other procedures for quality control, which can effectively reduce the pre-weld defects. Both inside and outside by selecting reasonable submerged arc welding process that eliminates pre-weld inside the pores, slag on the quality of submerged arc welding, pipe welding quality improved.