Analysis of uneven and eccentric thickness of seamless steel pipe (2)
Analysis of uneven and eccentric thickness of seamless steel pipe (2)
Any factor that damages the geometry correctness of the deformation zone formed by the roll, head and guide will aggravate the uneven thickness of the capillary wall.
(1) Head.
he shape design of the top, the ideal top rolling cone should be parallel to the roll exit cone, if the design of the top according to the traditional Matvikov formula, the top rolling cone and the roll exit cone are not parallel, the metal deformation in such a gradually expanding gap, is bound to cause insufficient tube wall rolling and lead to uneven tube wall thickness, and, The uneven capillary wall thickness becomes more serious with the increase of feed Angle.
Because the stiffness of the ejector rod is not enough, it is bent during the perforation process, so that the ejector head can not maintain the alignment position, so that the wall thickness of the perforated capillary is uneven;
Uneven wear or damage of the top.
(2) Guide plate.
The guide distance is too large, in the process of perforation is to rely on the limited role of the guide to maintain the center line of the perforation, the guide distance is large, the top change in the upper and lower position, so that the top is unstable, resulting in uneven capillary wall thickness.
The uneven wear of the upper and lower guide plates will also exacerbate the uneven wall thickness.
(3) Roll.
Roll center line deflection: In the production process, due to the incorrect installation of the screw on both sides of the perforator, or due to thread and bearing wear, the axial deflection between the two rolls occurs horizontally, and the feed Angle of the two rolls distorts the deformation area, resulting in uneven wall thickness.
The large feeding Angle causes the top head to be more parallel to the rolling cone of the roll.
Improper roll speed will also affect the wall thickness accuracy.
(4) Centering and heating of tube billet.
Centring hole eccentricity and uneven heating (Yin and Yang surface) will cause uneven wall thickness.
(5) Stiffness, structure and adjustment of the perforator.
The stiffness of the body of the piercing machine is not enough, and the locking mechanism on it is not reliable; The centring device of the ejector rod is not adjusted accurately, the operation is not reliable and the distance from the fuselage is too far; The adjustment of the rolling center line is generally lower than the middle line of the rolling mill, which aims to improve the stability of the rolled parts. If the adjustment is too large, the relative relationship between the tools in the deformation zone will change asymmetrically due to the rolling line moving, and the uneven wall thickness of the capillary will also be affected.
