Causes of eccentric (uneven thickness) of seamless steel tubes

The products of seamless precise steel pipe will have the problem of uneven eccentric thickness, but how did it come into being? Many people do not understand, today we will talk about cold-drawn steel pipe, cold-rolled steel pipe, seamless steel pipe eccentricity is how to produce? Why is the concentricity of seamless steel tube less ideal?

The eccentricity of the cold drawn steel pipe for finishing rolling also causes eccentricity.

Any factor that destroys the geometric shape correctness of the deformation zone formed by roll, top and guide plate will aggravate the uneven thickness of capillary wall.

(1) head.

(1) In the shape design of the top, the ideal top rolling cone should be parallel to the roll outlet cone. If the top is designed according to the traditional Matveyev formula, the top rolling cone is not parallel to the roll outlet cone. Metal deformation in such an enlarged gap will inevitably lead to inadequate tube wall rolling and lead to wool. The thickness of the pipe wall is uneven, and the thickness of the wall is more serious with the increase of the feed angle.

(2) Because the stiffness of the ejector rod is not enough, the ejector rod bends in the process of perforation, so that the ejector can not maintain the center position, so that the wall thickness of the perforated capillary is uneven.

3. Uneven wear or damage of the head.

(2) guide plate.

(1) When the distance between the guide plates is too large, it depends on the restriction of the guide plates to maintain the central line of the perforation. The distance between the guide plates is too large, and the position of the top and bottom of the head changes greatly, which makes the top unstable and leads to the uneven thickness of the capillary wall.

(2) uneven wear of the upper and lower guide plates will also aggravate the uneven thickness of the wall.

(3) roll.

(1) Roll center line deflection: In the production process, because of improper installation of screw on both sides of piercing machine, or because of wear of thread and bearing, horizontal deflection occurs between the two rolls. The inconsistent feed angle of the two rolls distorts the deformation zone and results in uneven wall thickness.

2. Under the large feed angle, the rolling cone of the head and the roll is not parallel.

3. Improper roller speed will also affect the accuracy of wall thickness.

(4) centering and heating of billets.

The eccentricity and uneven heating of the centering hole will cause uneven wall thickness.

(5) stiffness, structure and adjustment of piercing mill.

The stiffness of the piercing machine body is not enough, and the locking mechanism on it is unreliable; the alignment device of the ejector rod is inaccurate, and the operation is unreliable and far from the machine body; the alignment of the rolling center line is generally lower than that of the mill center line, which aims to improve the stability of the rolling piece. If the alignment is too large, the deformation zone will occur when the rolling line moves down. The asymmetry of the relative relationship between the tools will also affect the uneven wall thickness.

To sum up, there is no way to avoid the uneven eccentric thickness of seamless steel tube, and it can only be strictly controlled step by step to minimize it. If you have any ideas about our parsing, welcome to leave a message for Raymond steel tube company.