Several common defects and effects of straight seam steel pipe

1. How does the gnawing of straight seam steel pipe happen? What is the effect on welded pipes?
The gnawing edge of the straight seam steel pipe usually occurs on the slitting strip coil. The gnawing edge of the straight seam steel pipe is a jagged appearance at the edge of the steel strip. The reason is that the disc blade of the slitting machine is blunt or not sharp. The stability of the weld is affected when the steel strip with severe gnawing edges is welded, and cracks and cracks occur due to a partial lack of meat from time to time.

2. How does the wave bend of straight seam steel pipe happen? What is the effect on welded pipes?
The wave bend of the straight seam steel pipe is the appearance of repeated longitudinal bending on one or both sides of the edge of the steel strip. The wave bend is formed by the uneven deformation of the central part and the marginal part along the width direction when the steel strip (or plate coil) is rolled. Both sides) wave-style warping. The reason is either the wear of the roll, the uneven temperature of the center and edge of the strip, or the unequal thickness of the strip. The wave bend of straight seam steel pipe will cause serious lap welding during forming welding, making production impossible.

3. How do scars, indentations, scratches, and head and tail unevenness occur, and what impact do they have on welded pipes?
These disadvantages are caused by the hot rolling (or cold rolling) of steel strips. Scarring is an inherent defect of the strip. The indentation of the straight seam steel pipe is caused by foreign matter sticking to the roll during rolling. The unevenness of the head and tail is caused by the direct coiling of the steel strip or coil without cutting the head and tail after rolling. Scratches are formed by scratches on the roller table or on the floor during the travel of the steel strip. Straight seam steel pipes, especially cold-rolled steel strips, are easily scratched when they are not oiled. Straight seam steel pipe scars, indentations, scratches, head and tail unevenness, and other defects are transferred to the surface of the welded pipe, resulting in unqualified, cut-off, or scrapped, which reduces the yield and qualification rate of the welded pipe.

4. How does the camber bend of straight seam steel pipe happen? What is the effect on welded pipes?
The sickle bend of the straight seam steel pipe is the appearance of bending to one side on the horizontal plane along the length direction of the steel strip or called the crescent bend of the straight seam steel pipe. The sickle bend of the straight seam steel pipe is formed by the uneven deformation of both sides along the width direction during the rolling of the steel strip. One side has a large extension and one side has a small extension. The reason is either the uneven pressure at both ends of the roll, the uneven temperature on both sides of the strip, or the uneven thickness on both sides of the strip. The sickle bend is not allowed on the spiral welded pipe, which will lead to the instability of the spiral weld and the instability of the diameter of the straight seam steel pipe. When the straight seam steel pipe is welded, it will also cause lap welding, deviation or even overturning during forming. During straight seam welding, the sickle bend shall not be greater than 3 mm per meter.

In addition to the ones we mentioned above, the straight seam steel pipe tower coil is a shape in which the steel strip rolls from the inner ring to the outer ring in a tower shape, which is formed by uneven coiling during coiling. Slight turrets have little effect on welded pipes. The usual tower shape is not more than 50 mm. The severe tower shape of the straight seam steel pipe prevents the coil from running on the cooler, resulting in the loss of metal.