1. The key to the uneven wall thickness of the hot-rolled seamless tube is the one-time hole in the hot rolling. The uneven wall thickness of the capillary hole is likely to be caused by the following three factors.
①The heating of the tube material is uneven, which is the yin and yang face in general.
When the pipe material is heated in the inclined-hearth furnace, the material is not frequently transferred, which will cause the pipe material to be half "cooked" and half "raw". When the hole is broken, the frictional resistance is different, resulting in uneven wall thickness.
②The hazard of the shape and position of the top side.
Too much application of the top edge, part of the fused deposition "table", the "table" has an uneven aspect ratio, which is equivalent to the top edge is not round, which will harm the uneven wall thickness; when it is more serious, it will continue to scratch the capillary. The surface layer leads to "heavy leather" inside. After the top edge, the uniformity of the wall thickness will also be compromised.
③The small chain vibrates.
The piercing machine's rest assured roller was not adjusted in time, and the small chain could not be steadily "hugged". The small chain vibrated, resulting in uneven wall thickness.

2. Causes of uneven cold-drawn seamless pipe(sa 106 gr b)thick-walled pipe:
①The inclination of the front cutting of the pipe material, excessive bending, and the skewed pipe material relief hole can easily lead to uneven wall thickness at the top of the seamless steel pipe head.
②When the hole is broken, the widening index is very large, the speed ratio of the hot-rolled strip is too high, and the cold-rolling is unstable.
③The unstable steel throwing of the piercer can easily lead to uneven wall thickness at the end of the capillary.