RU1787055C - Method of making straight-seam welded pipes - Google Patents

Description

a method of manufacturing welded flashing tubes, including forming a tube stock, heating its edges, flattening the edges, their upsetting and welding in a cage with vertical application of the resultant force from the technological tool (roll). In this case, the resultant force from the technological tool to the upper part of the perimeter of the workpiece is applied before the convergence point of the edges at a distance of h - k, and the resultant force from the technological tool in contact with the lower part of the perimeter is applied behind the point of convergence of the edges at a distance of k and the relationship between these values set equal to ..- .. ....... .....

. . 2-10, where h is the distance between

force points from the rolls to the upper and lower parts of the workpiece.

When using this method, adopted for the prototype, obtaining an internal burr with a regulated height and stable shape is provided on pipes of a narrow range of size and grade assortment. In particular, if the ratio

k .-.

. . set close to the recommended small value of 2, i.e., if you increase the distance from the axis of the upper roll to the point of convergence of the edges, the process efficiency and the degree of heating of the edges are removed. When choosing the ratio

k. close to the recommended large values of 10, the point of convergence of the edges is displaced beyond the contact point of the pipe and rolls, which leads to the elimination of the artificial bridge.

To clarify the above, let us consider an example of the process of manufacturing pipes in a cell with two horizontal rolls during the transition from a thin wall to welding with a thicker wall 5 1.5; 2; 3 mm (Fig. 1). The edges of the workpiece plowed the HDTV. For 1.5 mm (Fig. 1a), the point of convergence of the edges was at a distance of k 40 mm from the point of application of the resultant force to the lower part of the perimeter of the tube billet. To create a mode of welding with an artificial jumper of current, the upper roll is shifted to L 50.mm,

k

. . 4. If b is the initial distance from the inductor spots to the axes of the welding rolls, then after the upper roll is displaced beyond the point of convergence of the edges in the opposite direction to the pipe direction, this is the distance for the upper roll

will decrease by A b 50 mm, similarly for a pipe with a wall thickness (5 2 mm L b 75 mm (Fig. 16) and for a pipe with a wall thickness (5 3 mm L 85 mm (Fig. 1 c).

Thus, the distance from the edge of the inductor to the axis of the upper welding roll is equal to bi b - 50, b2 b-75,. This leads either to the maximum approximation of the upper welding roll to the inductor, or to its overlap by the roll. When the inductor is very close to the welding roll, the latter enters the electromagnetic field formed by the inductor, and part of the energy is spent on heating the welding rolls, which leads to damage to their surface, insufficient heating of the workpiece edges and a decrease in the quality of pipe welding. In case of blocking the heating device (inductor) with a roller, it becomes necessary to move the latter, and this is associated with great difficulties, since the placement of the equipment of the heating device (inductor) in the mill line is performed with the calculation of the field

Take into account the minimum possible energy losses in conductive wires and buses.

The aim of the invention is to improve the quality of the pipes by creating a stable shape and reducing the height of the inner weld when welding pipes of a wide size and grade assortment, by ensuring the simultaneous approximation of the upper roll to the inductor (without overlapping it) and

expanding the girdle formation zone.

The goal is achieved by the fact that in the manufacture of welded straining pipes by a method including forming a pipe billet, heating its edges, welding the billet in a stand with vertical application of the resultant force from the technological tool (roll) to the upper and lower parts of the workpiece and moving the point of application of force to the upper part of the workpiece in a vertical plane, in contrast to the known one, the welding process is conducted with a shift of the point of application of the resultant forces relative to the point of convergence of the edges by simultaneously go bias

rolls in opposite directions.

In FIG. 26 shows the path of movement of the edges relative to the point of convergence of the edges; in FIG. 2a is a diagram of the movement of rolls relative to the edges of a workpiece.

The essence of the proposed method consists in the fact that the edges of a preformed billet are heated by high-frequency current using an induction or contact current supply and are welded in a welding stand. A technological tool that interacts with the upper part of the perimeter of the workpiece, and a technological tool that interacts with the lower part of the perimeter of the workpiece, are simultaneously displaced in opposite directions by equal distances relative to the plane passing through the point of convergence of the edges. Moreover, the force applied to the upper part is shifted against the movement of the pipe, and applied to the bottom - in the direction of movement.

The stability of the shape of the burr (the absence of splashes) and the stability of the precipitation are determined by the technological tool interacting with the upper part of the perimeter of the workpiece, i.e., with the part where the weld is located. Therefore, to ensure the stability of the burr, the upper technological tool is made in the form of a single roll with a groove in the upper part of the gauge and with an axis located horizontally,

The technological tool in contact with the lower part of the perimeter of the workpiece does not directly affect the burr and can therefore have a different shape and design depending on the specific production conditions, diameter and wall thickness of the pipe, steel grade, technical requirements for the finished product and conditions for the further limit, mill designs, etc.

For example, the lower technological tool (roll) can be made in the form of a single roll with a horizontal axis. For simplicity, hereinafter, the technological tool in contact with the upper part of the perimeter of the workpiece will be called the upper roll, and with the lower - lower roll.

Thus, the upper roll is offset relative to the plane passing through the point of convergence of the edges so that the point of application of its force acting on the workpiece is in front of the point of convergence of the edges in the direction of movement of the workpiece; the lower roll is offset relative to the plane passing through the point of convergence of the edges so that the point of application of its resultant force and the workpiece is beyond the point of convergence of the edges along the pipe.

The upper and lower rolls provide such a deformation scheme for the workpiece in the weld zone, in which (Fig. 26) the edges of the workpiece move along the concave and. convex part of a curve line,

The offset of the upper and lower rolls relative to the point of convergence of the edges allows irrespective of changes in geometric (wall thickness, perimeter of the workpiece) and deformation (depending, in particular, on the steel grade of the workpiece and calibration of the technological tool

5 welding and molding stands) of the perimeters of the welding process, it is guaranteed to carry out artificial bridging of the workpiece edge in front of the convergence point of the edges. The latter makes it possible to stabilize the formation of an internal burr irrespective of the size and grade of the assortment of pipes welded using the same set of technological tools.

5 In addition, when the welded edges move along the convex part of the trajectory I (Fig. 26), which is the zone of formation of the burr, centrifugal forces additionally stabilize the shape and

0 reducing the height of the inner burr. This is especially important for further processing of pipes or in the case of direct (without processing) their use in special fields of technology. Depending on the degree of compression,

5, for example, when welding pipes of the same diameter, which is determined by the wall thickness of the workpiece, the point of convergence of the edges moves along the axis of the pipe. In this case, when welding the most thick-walled pipes

0, the point of convergence of the edges moves to the maximum distance in the direction opposite to the direction of movement of the pipe. Therefore, it is precisely when welding the most thick-walled pipes, when in welding

5 of the stand, the amount of edge compression and, therefore, the value of the forming burr is maximum, the distance between the upper and lower rolls of the welding stand is set to the greatest. Offsets simultaneously

0 the upper and lower rolls in opposite directions to the distance a (Fig. 3) relative to the point of convergence of the edges, we obtain the distance between the rollers 2a (Fig. 3). Thus, at the same time,

5 of the graton formation zone increases, which leads to an increase in the effectiveness of the stabilizing effect on the internal grata.

In addition, with increased reduction

0 edges to eliminate their overheating, it is necessary to reduce the temperature. This is also achieved by maximally displacing both rolls in opposite directions relative to the point of convergence of the edges.

The energy consumption required for welding depends significantly on the distance between the inductor (or contacts) and the point of convergence of the edges. As this distance increases, the heating time increases and, consequently, power loss due to heat transfer from heated edges to adjacent metal layers. This leads to a decrease in welding speed. To reduce the internal burr, it is necessary to increase the welding speed and, therefore, reduce the distance from the inductor to the point of convergence of the edges. All this is achieved by simultaneously shifting the rolls in opposite directions relative to the point of convergence of the edges.

The parameters of the proposed method, implemented in the line of the mill 10-60 of the Moscow Pipe Plant, are shown in the table.

The implementation of the proposed method was carried out at MTZ in December 1990.

Claims (1)

SUMMARY OF THE INVENTION A method for manufacturing welded outer tubes, comprising forming a tube billet, heating its edges, and converging edges at the point and welding with the application of compressive forces to the molded workpiece by the upper and lower profiled rolls while displacing the upper roll relative to the edge reduction point, distinguishing also in order to improve the quality of the pipes by ensuring a stable shape and lowering the height of the inner grain during welding pipes in a wide range of their size and grade assortment, simultaneously with the displacement of the upper roll relative to the roll point, additionally shift the lower roll in the opposite direction. Direction to peden (t. E. Ni ermego lady axis & eaxMP3Q / 6QJX &. Directional. pedeshshche .. nor $ rtes & vfeso balkho. lower axis ПпЛНЛ; . Fig g B & jfHtlu UOJIOtf Point of convergence Kronok lower bsiyuk Fig.Z