RU2414319C1 - Method of metal forming - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to metal forming with high-intensity plastic deformation and serves to produce nanocrystalline structure of materials with higher mechanical properties. Moulding is carried using die made up of two half-dies. Each half-die has one parallel channel and one intermediate channel. Intermediate semi-channel and semi-channel of another half die make common intermediate channel. At first moulding stage, prior to placing billet into die, half-dies are transferred unless axes of parallel channels are located on one straight line and they form common channel. Then, billet is place into said channel. Axial strain forces are applied simultaneously with lateral strain forces to both faces of the billet, and moving half-does are moved into initial position. Center of plastic deformation originates at biller medium part, and gets divided into two centers to be displaced toward billet ends. At second moulding stage, axial straining loads are removed to displace moving half-dies in opposite directions to form common straight channel. Intermediate channel length at all stages and in each moulding moment is taken to equal the distance between plastic deformation centers. Billet material is changed into stress-strain state by varying male die transfer speed-to-half die transfer speed ratio. ^ EFFECT: fine-grained structure of materials. ^ 11 cl, 9 dwg

Description

The present invention relates to the processing of metals by pressure using intense plastic deformation and is intended to obtain a nanocrystalline structure of materials with an increased level of mechanical properties.

A known method of processing metals by pressure, in which the workpiece is installed in a matrix with two parallel channels connected by an intermediate channel, an axial load is applied to the workpiece and it is pressed by successive pushing through the matrix channels. The intermediate channel of the semi-matrices forms, with parallel channels, internal crosswise lying angles greater than 90 °.

[RF patent 2181314, IPC B21D 25/02. "Device for metal forming." Declared June 9, 2000, publ. April 20, 2002].

The disadvantages of this method include the fact that during the sequential passage of the workpiece by the knees of the matrix, successive formation of deformation centers occurs, which leads to the emergence of significant friction forces between the workpiece and the matrix and requires the application of increased loads to deform the workpiece. This leads to an increase in the energy intensity of the process.

With this method of processing a workpiece, its shaping in the foci of plastic deformation is carried out only due to shear deformation when only non-uniform compressive stresses are applied to the focal point of plastic deformation. This processing method does not allow controlling the scheme of the stress-strain state of the material in the deformation zones and does not allow introducing new, additional sliding planes into the crystal structure of the material in the grain grinding process (obtaining a nanocrystalline structure).

The location of the intermediate channel in relation to parallel channels at an angle of more than 90 ° reduces the degree of hardening of the workpiece material, because the larger the angle, the lower the degree of hardening.

The closest in technical essence and the achieved result is a method of processing metals by pressure, in which pressing is carried out using a matrix containing two movable half-matrixes, in each of which one of the parallel channels and an intermediate half-channel are formed, forming a single intermediate channel with the half-channel of the other half-matrix. This channel forms with parallel channels internal crosswise lying angles greater than 90 °.

Before installing the workpiece in the matrix, half-matrices are moved until the axes of the parallel channels are located on one straight line and they form a single channel. Then, a workpiece is installed in the channel, lateral deforming loads are applied, and moving half-matrixes are moved until the axes of the parallel channels return to their original position. In this case, the intermediate half-channels form a single intermediate channel. Under the influence of the forces developed by the semi-matrices in the middle part of the workpiece, a plastic deformation zone occurs, which is divided into two centers, shifting to the end sections of the workpiece. In this case, the preform is modified mainly due to shear deformation. (Express information “Technology and equipment for forging and stamping”, VINITI, Moscow, No. 26, 1982, p. 18).

In this method, the friction forces between the workpiece and the matrices are reduced by changing the sequence of formation of the deformation zones - from the middle of the workpiece to its edges, which reduces the load required to deform the workpiece and, as a result, reduce the energy consumption of the process.

However, this method does not allow to obtain a nanocrystalline structure of the workpiece material due to both insufficient shear strain in the workpiece deformation centers and the unidirectional nature of shear deformation and, moreover, does not allow to control the stress-strain state of the workpiece material in the deformation centers by creating not not only shear deformations, but also additional tensile or compressive deformations, which does not allow introducing grains into the grinding process (obtaining nanocr crystalline structure) new additional sliding planes in the crystal structure of the material and to intensify the process of structure formation material.

The technical result aimed at achieving the proposed technical solution is to eliminate the above disadvantages, namely: obtaining a finer-grained structure of the material by changing the direction of shear and providing the ability to control the stress-strain state of the workpiece material in the deformation zones by creating not only deformations in them shear, but also additional tensile or compression deformations, which will allow introducing grains into the grinding process (obtaining a nanocrystal structure) new additional slip planes in the crystalline structure of the material and will intensify the process of structure formation of the material.

The claimed technical result is achieved by the fact that when implementing the method of metal forming, pressing is performed using a matrix containing two movable half-matrixes, each of which has one of the parallel channels and an intermediate half-channel forming a single intermediate channel with the half-channel of the other half-matrix. At the first stage of pressing, before installing the workpiece into the matrix, half-matrices are moved until the axes of the parallel channels are located on one straight line and they form a single channel. Then the blank is installed in it, lateral deforming loads are applied and the movable half-matrixes are moved until the axes of the parallel channels return to their original position with the formation of a single intermediate channel by the intermediate half-channels and with the occurrence of a plastic deformation center in the middle of the workpiece, dividing it into two foci and then them offset to the end sections of the workpiece.

New in the proposed method is that at the first stage of pressing simultaneously with lateral deforming loads, axial deforming loads are applied to both ends of the workpiece, the method also comprises a second stage of pressing, in which the axial deforming loads applied to the ends of the workpiece are removed and the movable half-matrixes are moved to opposite direction to the location of the axes of the parallel channels on one straight line and the formation of a single rectilinear channel with the movement of the focus of plastic deformation to the middle part of the workpiece. The length of the intermediate channel at all stages at each moment of pressing is maintained equal to the length of the zone between the centers of plastic deformation. In addition, at all stages, the pressing process is controlled by creating the required stress-strain state of the workpiece material by changing the ratio of the speeds of movement of the punches and half-dies.

The first and second stages can be performed sequentially the nth number of times and to facilitate the extraction of the workpiece from the matrix to finish pressing after an even stage.

For a more uniform distribution of the nanocrystalline structure after removing the deforming loads, the workpiece is rotated around its axis before further pressing.

When implementing the method, a deforming load is applied using punches, and the ratio of the speeds of movement of the punches and movable half-matrices is assigned in the range of 0.85 ... 1.15.

To increase the degree of hardening of the material, the intermediate channel of the semi-matrices is positioned so that it forms, with parallel channels, internal crosswise lying angles α, the magnitude of which is less than 90 °.

The accompanying drawings show the essence of the proposed method:

figure 1 - the initial position of the bar stock in the matrix before performing the first (odd) stage of deformation with internal crosswise lying angles α between the intermediate and parallel channels equal to 90 °;

figure 2. - section I-I of figure 1;

figure 3. - section II-II of figure 1;

figure 4. - section III-III of figure 1;

figure 5 - the final position of the first (odd) stage of deformation of the workpiece;

6 - the initial position of the second (even) stage of deformation of the workpiece;

Fig.7. - the final position of the second (even) stage of deformation of the workpiece;

Fig. 8 - deformed position of the workpiece with internal lying angles α between the intermediate and parallel channels of the matrix less than 90 °;

Fig.9 - the deformed position of the workpiece with internal crosswise lying angles α between the intermediate and parallel channels of the matrix is greater than 90 °;

Pressing the workpiece is carried out using a matrix with parallel channels 1 and 2 (figure 1), connected by an intermediate channel and directed from it in opposite directions. The matrix contains a movable half-matrix 3, in which a parallel channel 1 and an intermediate half-channel 4 are made, and a half-matrix 5 with a parallel channel 2 and an intermediate half-channel 6. When combined, the half-channels 4 and 6 form a single intermediate channel 7 (Fig. 2). The intermediate channel 7 forms with parallel channels 1, 2 internal crosswise lying angles α equal to 90 °.

The method of metal forming is implemented as follows.

Before installing the workpiece 8 (Fig. 1), half-matrices 3 and 5 are moved into the matrix until the axes of parallel channels 1, 2 are located on one straight line and they form a single rectilinear channel. Then, the blank 8 is installed in the specified channel. The blank 8 may be in a cold or heated condition for forging, as well as made of solid metal or pre-pressed briquette from powder and granular metals and alloys, or in the form of a tube or tubular blank filled with plastic filler. To the ends of the workpiece 8, the punches 9 and 10 are brought. In this case, the workpiece 8 is completely covered by the surfaces of the punches 9, 10 and half-matrices 3, 5 (Figs. 3, 4). Then, the punches 9, 10 (FIG. 1) are informed of the counter synchronous movement. The punches 9, 10 impose forces P on the ends of the workpiece 8, sufficient to transfer the material of the workpiece 8 into a plastic state and create a volumetric uneven compression scheme in it.

At the same time, lateral deforming loads are applied to the workpiece 8 by moving the movable half-matrices 3 and 5 in opposite directions along arrows A, choosing at the same time the ratio of the speeds of movement of the punches 9, 10 and the moving half-matrices 3.5, which also exert a force on the workpiece 8, which allows you to achieve the desired stress-strain state of the material of the workpiece 8 in its foci of deformation.

When moving the semi-matrices 3, 5 (Fig. 5), the axes of the parallel channels 1 and 2 are displaced to form the intermediate half channel 7 by the intermediate half-channels 4, 6, and the parallel channels 1, 2 are located on both sides of the single intermediate channel 7. At the initial moment deformation of the workpiece 8 in its middle part there is an instant center of plastic deformation, located in the plane of intersection of parallel and intermediate channels, which is then divided into two centers of plastic deformation 11 and 12. These centers include ma the series of the workpiece 8 from the zones adjacent to the ends of the punches 9, 10. In this case, the deformation zones 11 and 12 are shifted to the end sections of the workpiece 8. The length of the intermediate channel 7 is maintained equal to the length of the zone between the centers of plastic deformation 11 and 12. At the same time, the material of the workpiece 8 in the foci of plastic deformation receives unidirectional shear deformation, leading to misorientation of the grains and crushing of its crystalline structure.

After pushing the workpiece 8 through the channels 1, 2, 7 of the matrix, the second pressing stage is performed, in which the deforming loads applied to the ends of the workpiece 8 are removed (Fig.6), and the half-matrix 3, 5 are synchronously moved in the opposite direction (along arrows D), creating deforming forces sufficient to transfer the material of the workpiece 8 into a plastic state. Moreover, in the knee zones of the workpiece 8, two centers of plastic deformation 14 and 15 are formed again. Under the action of the applied loads, the centers of plastic deformation begin to approach each other, the length of the vertical zones of the workpiece 8 increases and in the final position of the half-matrices 3, 5 (Fig. 7) of the axis of parallel channels 1 and 2 are located on one straight line, and parallel channels form a single rectilinear channel with the displacement of the focus of plastic deformation to the middle part of the workpiece 8. The workpiece 8 acquires the original rectilinear shape. In the process of deformation, the material of the workpiece 8 in the centers of plastic deformation 14, 15 (Fig.6) again receives shear deformations directed in the opposite direction compared to the first stage of deformation. In the material of the workpiece 8, along with a change in the direction of shear strain, the value of the accumulated shear strain increases, leading, as a result, to further crushing of the crystalline structure of the material.

When implementing the described stage of processing the workpiece 8, axial punches 9, 10 can be applied loads directed towards each other (not shown), softening the stress state in the centers of plastic deformation of the workpiece 8.

To ensure a more uniform distribution of the nanocrystalline structure of the material over the volume of the workpiece to be processed, after removing the deforming loads, the workpiece 8, before the next stage of deformation, is rotated around its axis.

When processing workpieces from materials that are low-plastic under normal conditions, the movement speeds of half-matrices 3 and 5 (V _half ) are set according to:

V _half = (0.8 ... 1.0) V _OS ,

where V _oc - the speed of movement of the axial punches.

This makes it possible to impose additional compressive stresses on the plastic deformation centers of the workpiece 8 and, thereby, create a softer stress state scheme in them, which increases the ductility of the material, involving additional slip planes in the process of its structure formation with an increase in the degree of misorientation of grain boundaries.

When processing workpieces materials with a high yield strength or from highly hardening materials during their cold deformation in the axial punches 9, 10, excessively high compression stresses can be induced, leading to their destruction. To reduce the magnitude of the compressive stresses arising in the axial punches 9, 10 when processing the workpiece 8, the moving speeds of the moving half-matrix (V _half ) can be increased in accordance with the expression

V _half = (1.0 ... 1.15) V _oc

In this case, the movable half-matrix 3, 5 take on the share of energy costs for shaping the workpiece 8, thereby unloading the axial punches 9, 10. Additionally, the application of tensile stresses to the centers of plastic deformation of the workpiece 8 contributes to “loosening” of the subcrystalline structure of the material.

The application of compressive stresses at one of the pressing stages and tensile stresses at the other to the sites of plastic deformation of the workpiece makes it possible to increase the formation efficiency of the nanocrystalline structure of the material of the workpiece.

Depending on the required degree of grinding material grains or obtaining the required degree of misorientation of grain boundaries of the workpiece material 8 or other tasks, the first and second stages of deformation of the workpiece can be repeated n-th number of times.

In this case, it is advisable to finish the workpiece material 8 at an even stage of deformation, when it acquires a rectilinear shape that facilitates its extraction from the semi-matrix.

By ensuring the same total degrees of deformation of the material over the entire area of the foci of plastic deformation obtained by the preform during several stages of deformation, a more uniform distribution of the nanocrystalline structure along the radial sections of the deformable zone of the preform is ensured.

When implementing this method, it is also possible to use a matrix with an intermediate channel 7, which forms parallel angles α greater or less than 90 ° with parallel channels 1, 2 of half-matrices 3, 5.

Since the degree of hardening of the material depends on the angle α, and the smaller this angle, the greater the degree of hardening of the metal, it is advisable to arrange the intermediate channel 7 (Fig. 8) of the half-matrices 3 and 5 so that it forms internal parallel channels 1 and 2 crosswise angles α less than 90 °.

When the angle α is greater than 90 ° (Fig. 9), in comparison with the previous matrix execution options, this option, although it has a reduced structure formation efficiency, but requires lower loads for its implementation in comparison with the closest analogue, and, therefore, less energy-intensive and allows you to minimize the dimensions of the devices for its implementation.

The application of the proposed method allows to intensify the process of structure formation of the material by changing the direction of shear for the first (odd) and second (even) stages of deformation of the workpiece and providing the ability to control the stress-strain state of the workpiece material in the centers of plastic deformation by creating not only shear deformations in them, but also additional tensile or compression strains, which allows introducing into the process of grain grinding (obtaining a nanocrystalline structure s) New additional sliding planes in the crystal structure of the material.

Claims (11)

1. A method of processing metals by pressure, comprising pressing the workpiece using a matrix containing two movable half-matrixes, each of which has one of the parallel channels and an intermediate half-channel, forming a single intermediate channel with the half-channel of the other half-matrix, and at the first stage of pressing before installing the workpiece in the matrix is moved half-matrix from the initial position to the location of the axes of the parallel channels on one straight line and the formation of a single channel, they set the workpiece in it, with lay lateral deforming loads and move the movable half-matrixes until the axes of the parallel channels return to their original position with the formation of a single intermediate channel by the intermediate half-channels and with the occurrence of a plastic deformation center in the middle of the workpiece, dividing it into two foci and then shifting them to the end sections of the workpiece, characterized in that in the first stage of pressing simultaneously with lateral deforming loads axial axial forces are applied to both ends of the workpiece forming loads, at the second stage of pressing, they remove axial deforming loads applied to the ends of the workpiece and move the movable half-matrix in the opposite direction until the axes of the parallel channels are located on one straight line and a single rectilinear channel is formed with the focus of plastic deformation moving to the middle part of the workpiece, the stages control the pressing process by creating the required stress-strain state of the workpiece material by changing the speed ratio awns displacement plungers and jaws, and the intermediate length of the channel at each moment of pressing is maintained equal to the length between the centers of the zone of plastic deformation. 2. The method according to claim 1, characterized in that when pressing the first and second stages are performed sequentially n times. 3. The method according to claim 2, characterized in that the pressing is completed after an even stage of pressing. 4. The method according to claim 1, or 2, or 3, characterized in that after removing the deforming loads, the workpiece is rotated around its axis. 5. The method according to claim 1, or 2, or 3, characterized in that the axial deforming load is applied using punches. 6. The method according to claim 4, characterized in that the axial deforming load is applied using punches. 7. The method according to claim 5, characterized in that the ratio of the speeds of movement of the punches and the movable half-matrix set in the range of 0.85 ... 1.15. 8. The method according to claim 6, characterized in that the ratio of the speeds of movement of the axial punches and the movable half-matrix is set in the range of 0.85 ... 1.15. 9. The method according to claim 1, or 2, or 3, or 6, or 7, or 8, characterized in that the intermediate channel of the semi-matrices is positioned so that it forms with parallel channels internal crosswise lying angles α less than 90 °. 10. The method according to claim 4, characterized in that the intermediate channel of the semi-matrices is positioned so that it forms, with parallel channels, internal crosswise lying angles α of less than 90. 11. The method according to claim 5, characterized in that the intermediate channel of the semi-matrices is positioned so that it forms, with parallel channels, internal crosswise lying angles α of less than 90.

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