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Several common defects and effects of straight seam steel pipes

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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 coil. The gnawing edge of the straight seam steel pipe is the appearance of jagged and uneven edges of the steel belt. The steel strip with severe gnawing will affect the stability of the weld during welding, and cracks and cracks will occur because of the lack of meat from time to time.


2. How does the wave bend of straight seam steel pipe occur? 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 coil) is rolled. both sides) wavy warping. The reason is either the wear of the rolls, the uneven temperature of the center and the edge of the strip, or the uneven thickness of the strip. The wave bending of straight seam steel pipe will cause severe lap welding during forming and welding, which cannot be produced, so it is unacceptable.


3. How does scarring, indentation, scratches, and uneven head and tail occur, and what effect does it have on the welded pipe? The following is the specific introduction:

These shortcomings are brought about by hot rolling (or cold rolling) of steel strips. Scarring is an inherent disadvantage of the strip. The indentation of the straight seam steel pipe is formed by foreign matter sticking to the roll during rolling. The uneven head and tail are formed by the steel strip or coil that is not directly coiled by cutting the head and tail after rolling. Scratches are caused by foreign objects on the roller table or the floor during the travel of the steel strip. The straight seam steel pipe, especially the cold-rolled steel strip, is easily scratched when it is not oiled. The defects such as scarring, indentation, scratches, uneven head and tail of the straight seam steel pipe are transferred to the surface of the welded pipe, resulting in unqualified, cutting or scrapping, which reduces the yield and qualified rate of the welded pipe.


4. How does the sickle bend of the straight seam steel pipe occur? What is the effect on welded pipes?

The straight seam steel pipe camber bend is the appearance of bending to one side on the horizontal plane along the length of the steel strip, or the straight seam steel pipe crescent bend. The straight seam steel pipe camber bend is formed by the uneven deformation of the two sides along the width direction during the rolling of the steel strip. The reason is that the two ends of the roll are pressed unevenly, the temperature on both sides of the strip is uneven, or the thickness of the strip is uneven on both sides. Sickle bending is fundamentally unacceptable for spiral welded pipes, which will lead to instability of the spiral welded seam and instability of the diameter of the straight seam steel pipe. In the straight seam welded pipe, it will also lead to lap welding, deviation or even overturning during forming. For straight seam welding, the camber should not exceed 3 mm per meter.


In addition to the ones we mentioned above, the straight seam steel pipe tower coil is the shape of the steel strip coil being coiled in a tower shape from the inner ring to the outer ring, which is formed by uneven coiling during coiling. The subtle tower shape does not affect the welded pipe. The usual tower shape is no more than 50 mm. The severe tower shape of the straight seam steel pipe prevents the coil from running on the un-coiler, resulting in a lack of metal.


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