In the production process of
submerged arc welded steel pipes, especially in high-speed welding, undercut has become the main defect in the production process of spiral submerged arc welded steel pipes. The defect of undercut mainly has the following surface forms: single unilateral undercut, single bilateral undercut, unilateral continuous undercut, and bilateral continuous undercut. Among them, unilateral continuous undercut and bilateral continuous undercut are opposite. Welding seams are very harmful, and they become fatal defects of welding seams like welding cracks and incomplete penetration. Therefore, we should attach great importance to taking measures to prevent the occurrence of such defects.
1. Causes of formation: Generally speaking, the formation of a single unilateral undercut is sporadic and has no regularity. Excessive changes in the forming seam, small burrs or small gaps on the edge of the strip, and misformed edges may form a single undercut. For a single single-sided undercut that is within the scope of the standard, the undercut can be eliminated by grinding, and for the undercut that exceeds the standard range, it can be eliminated by repair.
2. Preventive measures: Due to the uncertainty caused by such defects, we do not need to make major adjustments. We can make the edges of the strip as smooth as possible and maintain stable molding if conditions permit. For the problem of smooth edges of the strip steel, an edge milling machine can be used instead of disc shears to solve the problem. For the problem of forming stability, it can be solved by improving the shape adjustment.
