Seamless steel pipe produces steel pipe eccentricity problem

Seamless steel pipes, precision-rolled steel pipes, and cold-drawn steel pipes will also have eccentricity problems due to perforation:
Any factor that destroys the geometric accuracy of the deformation zone formed by the roller, the head, and the guide plate will aggravate the uneven capillary wall thickness.

(1) Head.
① Shape design of the plug. The ideal rolling cone of the plug should be parallel to the exit cone of the roll. If the plug is designed according to the traditional Matveyev formula, the rolling cone of the plug will not be parallel to the exit cone of the roll. The metal will Deformation in such a gradually expanding gap will inevitably cause insufficient rolling of the tube wall, resulting in uneven capillary wall thickness. Moreover, the uneven capillary wall thickness becomes more serious as the feed angle increases;
② Due to the insufficient stiffness of the ejector rod, it bends during the piercing process, so that the ejector cannot maintain its centered position, resulting in uneven wall thickness of the capillary tube that passes through;
③Uneven wear or damage of the plug.

(2) Guide plate.
① The guide plate distance is too large. During the perforation process, the restriction of the guide plate is relied on to maintain the center line of the perforation. The guide plate distance is large, and the top changes greatly in the up and down position, making the top unstable and causing uneven capillary wall thickness.
② Uneven wear of the upper and lower guide plates will also aggravate the uneven wall thickness.

(3) Roller.
①Roll center line deflection: During the production process, due to incorrect installation of the pressing screws on both sides of the punching machine, or due to thread and bearing wear, the axial direction between the two rollers is horizontally deflected, and the feed angles of the two rollers are inconsistent. Distortion occurs in the deformation zone, resulting in uneven wall thickness.
② A large feed angle causes the rolling cone of the head and the roller to be less parallel.
③Improper roll speed will also affect wall thickness accuracy.

(4) Centering and heating of tube blanks.
The eccentricity of the centering hole and uneven heating (yin and yang sides) will cause uneven wall thickness.

(5) Stiffness, structure, and adjustment of the punch.
The body of the punching machine is not rigid enough and the locking mechanism on it is unreliable; the centering device of the ejector rod is inaccurately adjusted, unreliable, and far away from the machine body; the rolling center line is generally adjusted to be lower than the rolling mill center line. , its purpose is to improve the stability of the rolled piece. If the adjustment is too large, the relative relationship between the tools in the deformation zone will change asymmetrically after the rolling line moves downward, which will also affect the uneven wall thickness of the capillary tube.

Therefore, there is no way to completely avoid the uneven eccentric thickness of seamless steel pipes. It can only be strictly controlled step by step and minimized.