What are the reasons for the uneven wall thickness of the spiral welded steel pipe

The wall thickness of the spiral welded steel pipe is uniform, it looks good, the force is uniform, and it is durable. The wall thickness of the spiral welded steel pipe is uneven, and the steel pipe is unevenly stressed. A phenomenon that easily occurs during the steel pipe rolling adjustment process, the uneven wall thickness of the steel pipe is mainly reflected in the appearance of spiral uneven wall thickness, linear uneven wall thickness, and thicker and thinner wall thickness at the head and tail. The details are:

First: uneven wall thickness at the head and tail
Causes: 1) The front end of the spiral seam submerged arc welded steel tube blank has too large a slope and tortuousness, and the centering hole of the tube blank is not correct, which is easy to cause uneven wall thickness of the tapered steel tube head; 2) The elongation coefficient is too large when piercing, and the roll If the rotating speed is too high, the rolling will be unstable; 3) The steel throwing of the piercing machine will not be stable, which will easily cause uneven wall thickness at the end of the capillary tube.

Second: spiral uneven wall thickness
The causes are: 1) The wall thickness is uneven due to the adjustment of the rolling center line of the piercing machine, the inclination angle of the two rolls is not equal, or the reduction amount before the plug is too small, usually distributed in a spiral shape along the entire length of the tapered steel pipe; 2) During the rolling process, the centering roller is opened too early, the centering roller is not adjusted properly, and the wall thickness is uneven due to the vibration of the ejector rod, which is usually distributed in a spiral shape along the entire length of the tapered steel pipe.