SU685371A1 - Method of helical rolling of tubes in three-high mill - Google Patents

Description

one

The invention relates to pipe production, in particular to the hot rolling of seamless tubes from a hollow billet on a long cylindrical mandrel in a three-roll mill.

There is a method of helical rolling tubes in a three-roll mill, which includes crimping the front end of the liner with a roll comb at the thinned end of a long mandrel and further rolling on a free-floating mandrel. At the approach of the rear end of the thin-walled sleeve to the ridge of the rolls, the latter are diluted by no more than the height of the ridge 1. The magnitude of the underside and the thickened front end are within the cutting edge.

There is a known method of rolling tubes in a three-roll mill, including the deformation of a hollow billet on a free-floating long mandrel with a decrease in reduction by the end of the process by changing the distance between the rollers and their angle of inclination to the axis of rolling 2. The resulting pipes have a slight thickening of the wall at the end. This causes a decrease in the rolling speed in the process of rolling the rear end of the workpiece (in the process of releasing the deformation zone from the rolled metal). The decrease in the axial rolling speed during the process of freeing the deformation zone from the rolled metal increases the total masinating time of rolling the workpiece and, consequently, reduces the productivity of the mill.

Closest to the described invention is a method of rolling tubes in a three-roll rolling mill, which provides for the deformation of a hollow billet on a long cylindrical mandrel that moves freely with the billet during the rolling process 3.

The disadvantage of this rolling method is the impossibility of increasing the axial rolling speed above a certain limit due to the appearance of triangular sockets at the rear ends, which is due to the lack of active forces acting on the workpiece in the direction of its rotation from the rolls when rolling the rear end of the workpiece.

The aim of the invention is to increase the torque applied to the workpiece in

the direction of its rotation when rolling the rear end of the workpiece, reducing defects at the rear ends of the rolled tubes, increasing the possible rolling speed and productivity of the mill.

The goal is achieved by the fact that in the method of screw rolling of pipes in a three-roll mill, including the deformation of a hollow billet on a freely floating mandrel, torque is applied to the mandrel in the direction of rotation of the billet during the rolling of the rear end. The torque applied in the mandrel is 0.05-0.15 rolling torque.

The appearance of sockets limiting the speed of rolling in a three-roll mill is associated with a lack of rotation from the rolls when rolling the rear end of the billet to overcome the torque of the reactive forces acting on the billet at the same time. Attaching it to the front or rear end of the mandrel in the plane, the first: directional to the direction:, ;; torque in direction ;, rotation of the workpiece and the mandrel, increase the moment of active forces applied to the workpiece in the direction of its rotation. In the deformation zone is compression of the wall of the workpiece on the mandrel. The mandrel is tightly pressed to the billet by normal pressure forces and the moment applied to it will be transmitted to the billet. Thus, the application of torque to any of the ends of the mandrel increases the moment of active forces applied to the workpiece in the direction of its rotation when rolling a given end, which, in turn, prevents the appearance of a "socket at the rear end of the pipe and allows increase possible rolling speed and mill productivity.

The method consists in that the hollow billet is set with a long mandrel to a three-roll rolling mill where the workpiece is deformed by rolls on a free-floating long mandrel. When the rear end of the workpiece is rolled, an automatic system is triggered and a rotational moment in the direction of rotation of the workpiece and the mandrel is simultaneously applied to the front, rear, or both protruding ends of the mandrel. The moment can be transmitted to the ends of the mandrel from a special drive installed on the mill, by any of the known methods of torque transmission (friction device, gear coupling of the end of the mandrel and the drive mechanism, etc.).

The proposed method allows to increase the possible rolling speed without the formation of end defects (maximum rolling speed) by 13-25 / 0.

Claims (3)

1. A method of helical rolling of pipes in a three-roll mill, including the deformation of a hollow billet on a free-floating mandrel, characterized in that, in order to prevent the occurrence of a socket at the rear end of the pipe and thereby increasing productivity, the torque in the direction of rotation is applied to the mandrel blanks during the rolling of the back end. 2. A method according to claim 1, characterized in that the torque applied to the mandrel is 0.05-0.15 rolling torques. Sources of information taken into account in the examination 1. USSR author's certificate number 358041, cl. B 21 B 19/06, 1971. 2. US patent number 3465563, cl. 72-96, 1966. 3. US patent number 2060767, class. 72-100, 1936.