SU761041A1 - Method of screw expanding of tubes - Google Patents

Description

The invention relates to pipe production, in particular to methods of rolling pipes in three-roll mills.

There is a known method of screw rolling of pipes, which contains the deformation of a hot billet with three rollers on a mandrel when regulating the magnitude of the angle of feed of the rollers during the rolling process, namely, reducing it at the end portion of the pipe by 1-1.5 °.

This allowed us to intensify the rolling process and reduce machine time [1] However, setting the rolls to the feed angle distorts the geometric dimensions of the deformation zone, which reduces the accuracy of the rolled tubes.

The closest in technical essence to the proposed invention is a method of helical rolling of tubes, including the deformation of a heated hollow billet on a long mandrel with rollers with a screw thread on the inlet cone in front of the rowing, the projections of the axes of which are ny vertical? The square plane with the projection of the rolling axis constitutes the feed angle [2]. The disadvantage of 25 of this method is the distortion of the geometric dimensions of the deformation zone due to the angle of feed of the rolls, especially in the calibration section of the deformation zone, and the non-parallelism of the forming 30

2

mandrel and roll, leading to the longitudinal difference of the wall thickness of the pipe. Since different pipe sizes are rolled in a three-roll mill at different feed angles of the rolls, adjusting the position of the cage pressure screws and changing the calibration of the rolls on their calibration section does not allow reducing the induced difference below 0.07-0.23 mm. As the analysis shows, parallelism of the forming mandrels and rolls in the calibration section of the deformation zone can be achieved only in the absence of rotation of the rolls at the feed angle relative to the axis of rolling.

The aim of the invention is to improve the accuracy of the geometric dimensions of the pipe due to the parallelism of the surfaces of the rolls and the mandrel in the meridional section of the calibration section of the deformation zone.

^! This goal is achieved by the method of screw rolling tubes, including the deformation of a heated hollow billet on a long mandrel rolls with a screw thread on the inlet cone in front of the ridge, the projection of the axes on the vertical plane with the projection of the axis of the rolling is the feed angle diminished761041

3

The rolls feed angle is filled during the time when the metal fills the deformation zone and, before the established process is combined, the projections of the roll axes and the rolling axis onto the vertical plane. The location of the axes in the same plane at an angle of inclination of the generators of the calibration roll section to the roll axis equal to the rolling angle (on which the rolls are turned relative to the rolling axis in the plane of the meridian section of the deformation zone) ensures parallelness of the forming mandrels and rolls in the plane of the meridian section of the deformation center on the calibration section. The induced differential wall on the pipes in this case is minimal.

The drawing shows the meridional section of the deformation zone during the rolling of pipes.

The essence of the method of rolling is that the hollow heated billet 1 on the mandrel 2 is set into a caliber formed by three rollers having a screw thread 4 on the inlet cone 3 before the ridge 5. Before rolling, the rolls are installed at the feed angle, which, after the billet is seized, is reduced by rolls the time of filling the metals of the deformation zone and combining before the established process the projections of the roll axes and the rolling axis onto the vertical plane. The established process of rolling is carried out at a feed angle equal to zero. .

After the task of the workpiece in the rolls under the action of contact forces of friction, the sleeve begins to retract into the deformation zone and, at the same time, the angle of feed of the rolls is reduced so that by the end of the process of filling the deformation zone with rolled metal it becomes zero. Further, axial feed of the liner during the deformation process is provided by screw cutting on the inlet cone of the roll or the attachment of the rear sub4

pore (for thick-walled sleeves that can withstand the pressure of the backwater without crushing). The angle of inclination of the screw grooves to the axis of the roll should be 75–85 °, which ensures that the axial feed of the workpiece is commensurate with the feed at a roll feed angle of 5–15 °. In the final stage of the process, back pressure, naturally, is not carried out and the release of the sleeve from the mill

0 is carried out exclusively under the action of contact friction forces acting from the side of the profile grooves on the liner in the inlet cone, and the inertial forces that occur when the velocity of the axial feed of the liner is slowed down. The method provides improved accuracy of the geometric dimensions of the pipes, due to the fact that the steady-state process is carried out in the deformation zone, in which the forming mandrels

O and the roll are parallel in the calibrating zone.

Claims (1)

Claim The method of screw rolling of tubes, including the deformation of a heated hollow billet on a long mandrel with rollers with screw thread on the inlet cone in front of the ridge, the projections of the axes of which onto the vertical plane with the projection of the rolling axis make up the feed angle, characterized in that pipes, after gripping the billet, reduce the roll feed angle during the metal filling of the deformation zone and, before the established 5 process, align the roll axes and the rolling axes onto a vertical flat st.