SU1715455A1 - Screw piercing method - Google Patents

Abstract

The invention relates to pipe production and concerns the flashing of solid blanks in helical rolling mills. The purpose of the invention is to reduce the vibrations of the rod and, consequently, the difference in liners. A solid workpiece is deformed by rolls on a mandrel held by a rod. The rod is centered sequentially along the length of its supports. The supports are in contact with the inner surface of the sleeve emerging from the rolls. The length of the contact surface of the supports is determined in the range of 1.0-1.5 steps of the eccentric difference in thickness of the liner, induced in the deformation zone during the piercing. 3 il.

Description

The invention relates to pipe production, to flashing workpieces on a fixed mandrel in an oblique rolling mill.

The purpose of the invention is to reduce the oscillations of the rod and, consequently, the difference in wall thickness of the sleeves.

FIG. 1 shows the scheme of the proposed method of screw firmware; in fig. 2 and 3 - the sleeve with an eccentric gap and the thickened (supporting) part of the rod located in it is shown.

The workpiece 1 set in the rolls 2 and stitch on the mandrel 3 held by the rod 4, having thickened sections of the support 5, located along its length and centering the rod relative to the inner surface of the sleeve. The length of the contact surface of the supports is determined taking into account the change in the eccentric difference of the liner along the length induced in the deformation zone.

The length of AND supports 2 (Fig. 2) is taken within the range of 1-1.5 steps of changing the eccentric difference thickness of the liner. In this case, at any position of the support on the length of the liner, the smallest deviation of the rod axis from the piercing axis is ensured by centering this section of the rod with liner sections with a maximum wall thickness on two opposite sides. With a length of section 11 equal to one step of change in eccentric varying wall thickness, at any moment of the insertion of the sleeve, this section is inside the sleeve — it is centered by at least two sections of the sleeve with maximum thickness, the walls of two opposite sides. At the moment when the ends of section I are located against two sections with a maximum wall thickness on one side of the sleeve, an account h is centered with three sections of the sleeve with a small wall thickness (two on the one side of the sleeve and one on the opposite side). With an increase in the length of the plot And to

cl

WITH

sl sl

1.5 pitch centering of the rod is improved as the length of the sleeve sections increases, on which the rod is centered with three sections with maximum wall thickness, and the length of sections of the sleeve at which the rod is additionally centered with sections with a wall thickness close to the maximum value, and also decreases the curvature of the rod due to rotation relative to one of the points of the section with the maximum wall thickness during longitudinal bending.

If the length h is less than the pitch of the eccentric difference-thickness condition, the centering of the rod deteriorates, since on the one hand the transverse movement of the section li from the piercing axis is limited by the maximum wall thickness of the sleeve, and on the other by the thinner wall, i.e. conditions are created to increase the displacement of the rod axis relative to the firmware axis.

If the length of the section AND is greater than 1.5 steps, the conditions for centering the rod are almost unchanged, however, efforts to remove the rod increase due to the increased length of contact with the sleeve (until conditions arise when the rod cannot be removed from the sleeve).

The length of the sections of the rod between the supports 2 is determined by the known dependencies, based on the conditions for ensuring the longitudinal stability of these sections when piercing blanks (the longitudinal load on the sections of the rod r must be less than the minimum critical value).

The diameter of the thickened parts of the rod - supports

dcMaxc d2bH - DZmax -A,

where dabH is the inner diameter of the liner, mm;

AZmax - maximum value of the eccentric difference of the liner thickness (accepted on the basis of practical data), mm;

A 1-2 mm (A takes into account the effect on the magnitude of the internal channel waviness and

liner curvature, taken 1 mm for mm or 2 mm for djbH more than 75 mm), or (second option)

dc mar djbH - (0.08-025) Si- (0.005-0.015) dibH.

where S {is the average wall thickness of the liner, mm; (0.08-0.25) is a coefficient representing the ratio of the thickness to the average thickness of the liner wall.

(0.005-0.015) is a coefficient that takes into account the effect of curvature and waviness on the change in the internal channel.

Large values of the coefficients for Si and dZbH are taken at lower values of the wall thickness of the liner and its internal diameter.

A rod with thickened parts by m-supports can be made by rolling, forging, machining, packing the rings in a hot condition on the rod, etc.

When stitching billets according to the proposed method, the deformation of the rod in the transverse direction is limited by its thickened support sections, which come into contact with the inner surface of the sleeve.

As a result, oscillations of the rod and the liner are reduced, which improves the accuracy of the liner. At the same time, when stitching firmware by the proposed method

the necessary conditions are provided for removing the rod without difficulty.

Claims (1)

Invention Formula The method of screw firmware, including the deformation of a solid billet rollers on a mandrel held rigidly by a rod, centered consistently located along its length by the supports, in contact with the inner surface of the sleeve coming out of the rolls, characterized in that, in order to reduce oscillations of the rod and, consequently, the thickness of the sleeves, the length of the contact surface of each rod support is selected in the range of 1-1.5 steps of the eccentric difference thickness of the sleeve induced during the piercing. FIG. I FIG. 2 4b Fig.Z