Briefly Introduce Several Common Defects And Effects of Straight Seam Steel Pipes

1. How does edge gnawing of straight seam steel pipes occur? What impact does it have on welded pipes?

The edge of the straight seam steel pipe usually occurs on the slitting strip roll. The edge of the straight seam steel pipe is a jagged and uneven phenomenon at the edge of the steel strip. The reason is that the disc blade of the slitting machine is blunt or not sharp. When welding steel strips with serious edges, the stability of the weld will be affected, and cracks and cracks will occur due to a partial lack of meat from time to time.

2. How does the corrugated bending of straight seam steel pipes occur? What impact does it have on welded pipes?

The corrugated bend of the straight seam steel pipe is the phenomenon of repeated longitudinal deformation on one or both sides of the steel strip. Wave bending is caused by the uneven deformation of the center and edge parts along the width direction of steel strips (or coils) during rolling. The center part extends small and the edge parts (one or both sides) extend greatly, forming the edge part (one side or both sides). Both sides) wave-like warping. The reason may be that the rollers are worn, or the temperature of the center and edge of the strip is uneven, or the thickness of the strip is unequal.

The corrugated bending of straight seam steel pipes will cause severe lap welding during form welding, making production impossible, so it is not allowed at all.

3. How do scars, indentations, scratches, and uneven heads and tails occur, and what impact do they have on welded pipes? The following is a detailed introduction:

These shortcomings are caused by hot rolling (or cold rolling) of steel strips. Scarring is an inherent shortcoming of the strip. The indentation of the straight seam steel pipe is caused by foreign matter sticking to the roll during rolling. The head and tail unevenness is caused by the steel strip or plate coil being rolled without cutting the head and tail directly. Scratches are caused by foreign objects on the roller table or the floor during the movement of the steel strip. Straight seam steel pipes, especially cold-rolled steel strips, are easily scratched when they are not oiled.

Defects such as scars, indentations, scratches, uneven head and tail of straight seam steel pipes are eventually transferred to the surface of the welded pipes, causing them to be unqualified and sometimes cut out or scrapped, which reduces the yield and qualification rate of the welded pipes.

4. How does the sickle bend of straight seam steel pipe occur? What impact does it have on welded pipes?

The sickle bend of straight seam steel pipe is the phenomenon of bending to one side on the horizontal plane along the length direction of the steel strip, or it is called the crescent bend of straight seam steel pipe. The sickle bend of straight seam steel pipe is caused by the uneven deformation of both sides along the width direction of the steel strip during rolling. One side extends larger and the other side extends smaller, causing the steel strip to bend toward the smaller side. The reason is either uneven pressing at both ends of the roll, uneven temperature on both sides of the strip, or uneven thickness on both sides of the strip.

Sickle bending on spiral welded pipes is not allowed at all, as it will cause instability in the spiral weld and the diameter of the straight seam steel pipe. When straight seam steel pipes are welded, lap welding will also occur, causing deflection or even overturning during forming. During straight seam welding, the sickle bend shall not exceed 3 mm per meter.

In addition to the ones we mentioned above, straight seam steel pipe tower coils are steel strip coils that are coiled in a tower shape from the inner ring to the outer ring, which is caused by uneven coiling during coiling. The slight tower shape has no effect on 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, causing metal loss.