What are the reasons for the uneven wall thickness of spiral seam submerged arc welded steel pipes

The uniform wall thickness of the spiral seam submerged arc welded steel pipe looks good, the force is even, and it is durable. The spiral seam submerged arc welded steel pipe has uneven wall thickness. The steel pipe is unevenly stressed. The thin steel pipe is easy to crack. The uneven wall thickness of the steel pipe is A phenomenon that is easy to appear in the process of steel pipe rolling adjustment, the uneven wall thickness of steel pipe is mainly reflected in the appearance of uneven spiral wall thickness, linear wall thickness, and thick and thin wall thickness at the head and tail. The details are: 1: uneven wall thickness at head and tail Cause: 1) The front end of the spiral seam submerged arc welded steel pipe billet is too large to cut, the tortuosity is too large, the centering hole of the pipe billet is not correct, and the wall thickness of the tapered steel pipe head is uneven; 2) The elongation coefficient is too large during piercing, the roll speed is too high, and the rolling is unstable; 3) Unstable steel throwing of the piercer may cause uneven wall thickness at the end of the capillary tube. 2: Uneven spiral wall thickness The causes are: 1) The uneven wall thickness caused by adjustment causes such as the improper rolling centerline of the piercer, the unequal inclination angle of the two rolls, or the too-small front pressing amount of the head, etc., usually spreads spirally along the full length of the tapered steel pipe; 2) During the rolling process, the centering roller is turned over too early, the centering roller is not adjusted properly, and the wall thickness is uneven, which are usually distributed in a spiral shape along the full length of the tapered steel pipe.