Any factor that destroys the geometric shape of the deformation zone formed by the roller, the plug and the guide plate will aggravate the uneven wall thickness of the rough tube.
(1) Plug.
① The shape design of the plug. The ideal plug rolling cone should be parallel to the roller outlet cone. If the plug is designed according to the traditional Matveyev formula, the plug rolling cone and the roller outlet cone are not parallel. The metal deforms in such a gradually expanding gap, which will inevitably cause insufficient rolling of the tube wall and uneven wall thickness of the rough tube. Moreover, the uneven wall thickness of the rough tube becomes more serious with the increase of the feed angle;
② Due to the insufficient rigidity of the ejector rod, it bends during the piercing process, so that the plug cannot maintain the centering position, resulting in uneven wall thickness of the rough tube;
③ Uneven wear or damage of the plug.
(2) Guide plate.
① The distance between the guide plates is too large. During the perforation process, the perforation centerline is maintained by the limiting effect of the guide plates. When the distance between the guide plates is large, the position of the plug changes greatly, making the plug unstable and resulting in uneven wall thickness of the rough tube.
② Uneven wear of the upper and lower guide plates will also aggravate the uneven wall thickness.
(3) Roller.
① Roller centerline deviation: During the production process, due to incorrect installation of the press screws on both sides of the perforator, or due to wear of the threads and bearings, the axial direction between the two rollers is horizontally deflected, and the feed angles of the two rollers are inconsistent, causing the deformation zone to be distorted and resulting in uneven wall thickness.
② Under large feed angles, the plug and the rolling cone of the roller are more non-parallel.
③ Improper roller speed will also affect the wall thickness accuracy.
(4) Centering and heating of the tube blank.
Eccentricity of the centering hole and uneven heating (positive and negative sides) will cause uneven wall thickness.
(5) Rigidity, structure and adjustment of the perforator.
The body of the piercing machine is not rigid enough, and the locking mechanism on it is unreliable; the centering device of the push rod is not adjusted accurately, the operation is unreliable and it is far away from the body; the adjustment of the rolling center line is generally lower than the center line of the rolling mill, the purpose is to improve the stability of the rolled piece. If the adjustment is too large, after the rolling line moves down, the relative relationship between the tools in the deformation zone changes asymmetrically, which will also affect the uneven wall thickness of the rough pipe.
alloy pressure pipe
