Straight wall thickness uneven
Cause:

1) The saddle height adjustment for core rod pre-insertion is not suitable; during pre-insertion, the core rod contacts a side of the tube, causing the tube to rapidly lose temperature on the contact surface, resulting in uneven wall thickness of Q345B seamless steel tubes or even pulling凹 defects.

2) Excessive or insufficient gap between rolling rolls in tandem rolling.

3) Mandrel mill centerline deviation.

4) Uneven pressure on single or double racks can cause linear symmetric deviation, with the single rack direction being excessively thin (thick) and the double rack direction being excessively thick (thin).

5) A broken safety mandrel and large difference in the inner and outer roller gaps can cause asymmetric straightness deviation in Q345B seamless steel pipes.

6) Improper rolling adjustment can lead to uneven wall thickness in straight-line shapes due to steel stacking and pulling during rolling.