RU2537635C1 - Pressure treatment method of long workpieces from metals and alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: workpiece is arranged in two supporting and moving supports; tensile and compressive stresses are created by movement of the workpiece through a tool with creation of an electroplastic effect by using pulse or direct current. As the tool, a die with equal cross channels is used, and as supports supporting and moving the workpiece and at the same time as a source of pulse or direct current, reversible line motors are used. Tensile and compressive stresses are created with a combination of force action directions; for that purpose, reversing of line motors is performed, and the value of created stresses is controlled by variation of the value of forces developed by the motors.

EFFECT: improving mechanical properties of metal due to formation in it of fine-grained equiaxial structure.

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Description

The invention relates to the field of metal forming using intense plastic deformation and is intended to produce a nanocrystalline metal structure in long workpieces, such as rods, wire, etc. to increase their mechanical properties.

A known method of processing long workpieces by pressure (RF Patent No. 2417857, IPC B21J 5/06, application. January 11, 2010, published May 10, 2011), comprising feeding the workpiece into a working channel formed between a rotating disk and a stationary bounding base. At the output of the working channel, a change in its direction is provided by means of a support part installed in the annular groove. The workpiece is advanced along the working channel in the direction of its exit by rotating the disk and continuous equal-channel angular pressing is carried out without significant change in the cross section of the workpiece. Continuous equal-channel angular pressing of the workpiece is carried out in stages. At each stage, the cross section of the working channel is successively reduced. The blank before each subsequent pressing step is subjected to a plastic forming strain. The deformation temperature is lower than the temperature of recrystallization of the processed material. The result is an increase in the mechanical properties of the processed material due to more intensive grinding of the structure.

The disadvantages of this method are as follows.

1. Due to the fact that the advancement of the workpiece along the working channel is carried out using a rotating disk, during the processing of ductile metals the frictional forces arising between the workpiece and the wall of the trough cause distortion of the cross section of the workpiece, causing the inclusion (if necessary) in the process of processing material to restore the original cross-sectional shape of the workpiece. Moreover, after each stage of equal-channel angular pressing for the implementation of the forming operations of plastic deformation, the workpiece is removed from the working channel. This increases the complexity of processing the workpiece material. In addition, the implementation of the method involves the creation of a device equipped with an electric motor that rotates the central shaft. In this case, inevitable loss of electric motor power to overcome friction in the rotating elements of the device, which leads to an increase in energy consumption during the implementation of the method.

2. Since the preform during the processing accumulates the same deformations along its length, the method does not allow to obtain various normalized mechanical properties of the material on different parts of the preform along its length. This limits the technological capabilities of the method.

Also known is a method of pressure treatment of long workpieces of metals and alloys (RF Patent No. 2159162, IPC B21C 37/04, B21J 5/08, application form 01.10.1998, publ. 20.11.2000), in which the workpiece is installed in two supports moving with the help of the drive, and the workpiece is deformed according to various schemes: they are reduced by a tool with the possibility of relative displacements along and across the axis of the workpiece and relative rolling of its surface, for example, with a roller, while the specified degree of deformation is provided using at least also one of the schemes of deformation realized during torsion, upset, or tension, which are carried out using supports having the ability to influence the workpiece by forces corresponding to the deformation schemes. The temperature of the deformable section, necessary to obtain the desired structure and physico-mechanical properties in the workpiece material, is created using a furnace, which is moved along the workpiece.

This method requires sophisticated equipment, such as movable bearings, made with the possibility of force acting on the workpiece, the presence of a special furnace, also having the ability to move along the workpiece, the presence of rollers. This method is long and laborious.

Also known is a method of pressure treatment of long billets of metals and alloys, comprising deforming at least a portion of the long billet, mainly wire, which is placed in two supports supporting and moving the billet, the deformation being provided by tensile stresses in the billet by moving the billet through instrument with the creation of an electroplastic effect, which is created by applying pulsed or direct current. As supports supporting and moving the workpiece, an unwinding unit of a drawing machine is used, the tool is a draw, and the sources of alternating, direct or pulsed current provide an electroplastic effect. The supply of electric current to the wire during drawing is carried out by roller and brush contacts to a section of wire, including a deformation zone, i.e. dragging (Spitsyn V.I., Troitsky O.A. Electroplastic deformation of metals - M .: Nauka, 1985. Pages 34 ... 36).

The mechanism of electropulse current exposure provides active healing of micro-discontinuities in the workpiece material under the influence of gradients of thermomechanical compressive stresses that arise at the defect boundary during transmission of pulsed electric current. This process occurs during the passage of the workpiece through the die.

However, to obtain a nanostructured material, one pass may not be enough due to the small degree of accumulated deformation, and the use of a die as a tool does not allow the reciprocating movement of the workpiece for more intensive crushing of material grains. In this case, it is necessary to reinstall the workpiece, which makes the method time-consuming and inefficient.

The pulse action of the current on the workpiece material is carried out in the tool area, i.e. material having untreated microcontinuities enters the die.

In addition, the separate implementation of the supports and the current source makes the device for implementing this method difficult and inconvenient to use.

The technical result to which the invention is directed is to provide a high degree of nanostructuring of the material by improving the quality of the material entering the tool, by ensuring the formation of a fine-grained equiaxial structure in the material already in the supports, the ability to provide reciprocating movement of the workpiece through the tool the required number of times without reinstalling the workpiece, as well as the ability to control and the force pushing the workpiece through the tool. In addition, the technical result is the simplification of the device that implements the method, due to the implementation of the supports not only supporting and moving the workpiece functions, but also the functions of the current source.

The claimed technical result is achieved in that the method of pressure treatment of long billets of metals and alloys involves the deformation of at least a portion of a long billet, mainly wire, which is placed in two supports supporting and moving the billet. The deformation is provided by the creation of tensile stresses in the workpiece by moving the workpiece through the tool with the creation of an electroplastic effect using pulsed or direct current.

New in the invention is that a matrix with equal intersecting channels is used as a tool, and reversible linear electric motors are used as supports supporting and moving the workpiece, and at the same time a source of pulsed or direct current, while the workpiece is also deformed by compressive stresses. Tensile and compressive stresses in the workpiece are created by a combination of the directions of action of the forces, for which linear motors are reversed, and the magnitude of the generated stresses is controlled by changing the magnitude of the forces developed by the motors.

The method is illustrated by drawings, where:

figure 1 is an embodiment of equal channel angular pressing of a long workpiece under the influence of a pushing force from the side of the main linear motor and the application of compressive or tensile stresses to the focus of plastic deformation by the auxiliary linear motor;

figure 2 - lengthy workpiece with different nanocrystalline structure along its length.

figure 3 is an embodiment of a sequential equal channel angular pressing of a long workpiece in several matrices;

figure 4 - section aa figure 3.

A device for implementing the method includes a matrix 1 (Fig. 1) having intersecting channels 2 and 3, the cross sections of which are equal to the cross section of the workpiece being processed. At the input of the matrix, the main reverse linear motor with stators 4 and 5 is installed, and at the exit from the matrix, an additional reverse linear motor with stators 6 and 7 is installed. The engines are controlled by the control unit 8.

The method of processing long billets of metals and alloys, mainly wire, is as follows.

The workpiece 9, which can be either in the form of a wire of round or other cross-section, or in the form of strips of different cross-sections, is placed between the stators 4 and 5 of the reverse linear motor, which performs the function of its support, and the workpiece is a secondary element of the engine.

When connecting the stators 4 and 5 of the motor to an alternating current network, a magnetic field is formed, the axis of which will move along the air gap between the stators 4, 5 and the workpiece. 9. This moving magnetic field crosses the workpiece 9 and induces an electromotive force in it, under the action of which currents begin to flow in the workpiece 9. The mechanism of electropulse current exposure provides active healing of micro-discontinuities in the workpiece 9 material already in the supports — linear motors — during the passage of a pulsed electric current through the workpiece 9 and into the matrix 1, the workpiece 9 arrives with improved physicomechanical properties, in particular, with prepared favorable conditions (depending on current density), to intensify the formation of a fine-grained equiaxial structure in the material when the preform passes through the focus of plastic deformation in the no intersection of channels 2 and 3.

The interaction of the induced currents in the workpiece with a magnetic field leads to the appearance of a force P acting according to the well-known Lenz rule in the direction of movement of the magnetic field. In this case, the workpiece 9 receives movement through the intersecting channels 2 and 3 of the matrix 1. At the exit from the matrix 1, the workpiece is sent to the gap between the stators 6 and 7 of the additional reverse linear motor. When the linear motor is operating, an electric current will be induced in the workpiece: direct or pulsed, which leads to the appearance of an electroplastic effect.

In the process of operation of linear motors, the workpiece 9 is heated, which increases the plastic properties of its material and thereby reduces the required force P. The heating temperature is determined by the design of the linear motor, the speed of movement of the workpiece 9 through the channels 2, 3 of the matrix, the gap between the workpiece 9 and the stators 4, 5 of the main engine and 6, 7 of the additional linear motor, as well as physico-mechanical properties of the material of the workpiece 9.

The force P required to realize equal-channel angular pressing of a long workpiece can be determined using the energy method, for example, by balancing the power of external and internal forces applied to the workpiece and spent on overcoming the workpiece resistance to plastic deformation in the zone of intersecting channels 2 and 3.

Example.

For processing wire in the cold state (material: L62 brass, flow stress σ _S = 300 MPa (30 kg / mm2), diameter 2 mm) by equal-channel angular pressing through a die having a channel length of 2 and 3 to their intersection of 10 mm and the angle between the intersecting channels is 90 °, a force P = 500.6 kg is required, while it has been experimentally established that when processing by the claimed method, a force P = 390.3 kg is required.

The method also provides for the implementation of equal-channel angular pressing of a long workpiece 9 by the combined action of a pushing force P from the side of the main linear motor and the application of compressive or tensile stresses to the center of plastic deformation of the workpiece 9 by an additional linear motor.

In this case, the additional linear motor can operate (as well as the main one) both in pulsed and continuous modes, creating additional force applied to the workpiece 9 in the direction of movement of the workpiece 9 or counteracting this movement. In the first case, additional tensile stresses will be induced in the center of plastic deformation of the workpiece, and in the second, compressive stresses.

From the point of view of the force parameters of the method, the application of tensile stresses 9 on the deformation zone of the preform helps to reduce the required technological force P developed by the main linear motor, and from the technological point of view, it helps to loosen the crystal structure of the material in the center of plastic deformation, contributing to its crushing.

The imposition of additional compressive stresses on the plastic deformation zone causes a “softening” of the stress-strain state of the workpiece, increasing its ductility. This allows you to handle the proposed method, long workpieces from maloplastic materials under ordinary conditions.

In addition, depending on the program implemented by the control unit 8, the auxiliary linear motor can develop a compressive force greater than the force P developed by the main linear motor, and the main linear motor can operate in the auxiliary motor mode or be turned off. In this case, the workpiece 9 will change the direction of movement relative to the matrix 1 and the workpiece material will undergo a shear deformation treatment again in the zone of intersection of the channels 2, 3 of the matrix 1. In this case, although the position of the shear plane in the plastic deformation center is maintained, however, the shear directions experienced by the crystal structure of the material at the entrance to the deformation zone and the output will be reversed compared to the original. This leads to an increase in the degree of strain accumulated by the preform 9 and contributes to further crushing of the crystalline structure of the preform material. In this case, the Bausinger effect is realized, which is inherent in all metals taken in both single-crystal and polycrystalline states, both for small and final plastic strains, which consists in a decrease in deformation resistance.

The above method of reversing the pressing of a workpiece can be repeated n number of times set by the control unit 8 to both the entire workpiece 9 and to individual sections along its length. In this case, it becomes possible to control the degree of fragmentation of the crystalline structure of the material along the length of the workpiece 9, obtaining a long workpiece (figure 2) with pre-regulated material structure in its sections, for example, sections 10 and 11, and therefore the various properties of these sections of the workpiece 9.

T.O. The invention allows to provide a high degree of nanostructuring of the workpiece material by improving the quality of the material entering the tool by creating favorable conditions for the formation of a fine-grained equiaxial structure in the supports already in support, the ability to provide reciprocating movement of the workpiece through the tool the required number of times without reinstalling the workpiece. The method also allows to obtain various degrees of structuring of the material in individual sections of the workpiece.

In addition, the invention provides the ability to control the force pushing the workpiece through the tool.

A device that implements the method has a simpler design due to the support not only supporting and moving the workpiece functions, but also the functions of the current source

When processing the workpiece material in the pulsed mode of operation of the main and auxiliary linear motors, as well as when one of the engines is pulsed and the other in constant mode, a sufficiently large number of processing options for the workpiece material arise.

Additionally, the method provides for multiple processing of the material of long workpieces by sequentially pressing the workpiece through several matrices 1 (Fig. 3) having shear planes of the centers of plastic deformation deployed in space relative to each other at an angle α (Fig. 4).

Claims (1)

A method of pressure treatment of long workpieces made of metals and alloys, comprising deformation of at least a portion of a long workpiece, mainly a wire, which is placed in two supports supporting and moving the workpiece, while the deformation is provided by creating stresses in the workpiece as it moves through the tool with the creation of an electroplastic effect under the influence of pulsed or direct current, characterized in that as a tool using a matrix with equal intersecting provided by channels, and as supports supporting and moving the workpiece, reverse linear electric motors creating pulsed or direct current, while the workpiece is deformed by tensile and compressive stresses created by acting on it by a combination of forces of different directions by reversing linear motors, and the magnitude of voltages are regulated by changing the magnitude of the forces developed by the said motors.

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