RU2403206C1 - Method for obtaining nanocrystalline structure of material in pipe workpieces and device for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: group of inventions refers to plastic metal working and is intended for obtaining nanocrystalline metal structure in pipe workpieces, schemes of stress and strain state of deformable material. Workpiece cavity is filled with filler, edges are sunk with axial punches and middle zone of workpiece is shifted in the direction perpendicular to its axis at creation of pressure, during the shift, in filler, which is kept by constant control of the filler amount, and shift speed is chosen depending on sinking speed of edges and also kept constant. At the end of odd workpiece deformation step there stopped is sinking of its edges by keeping its cavity tightness, and at even step there performed is shift of middle part of workpiece in the direction opposite to the previous one till the workpiece has initial straight-line state. At that, shift speed of middle zone of workpiece is provided depending on movement speed of axial punches. Workpiece is rotated through standard angle relative to its axis and odd step of its deformation is implemented, or direction of shift of middle part of workpieces is kept at odd and even deformation steps. Device includes split die consisting of upper and lower semi-dies and having central insert consisting of pressure-bearing and support semi-inserts, punches of axial compression of pipe workpiece. In die channels there arranged are pins the section of which has the shape corresponding to the shape of workpiece section, which interact with their edges on one side to workpiece surface, and on the other side - with stocks of hydraulic cylinders the axes of which are perpendicular to pin axes. At that, pins and hydraulic cylinders are arranged in pairs in upper and lower semi-dies.

EFFECT: increasing efficiency and ensuring the quality.

4 cl, 14 dwg

Description

The 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 in tube blanks.

A known method and device for the structuring of metals with equal channel angular pressing, containing a site for deformation, having two communicated channels, one of which is placed the workpiece, and a site for loading, with which they push the workpiece into the second channel, while the channels of the site for deformation are at an angle to one another and have the same diameters equal to the diameter of the workpiece [A.S. 492780 USSR, MKI 3 G01N 3/00. Device for hardening material by pressure / V.M.Segal, V.Ya. Shchukin (USSR). - 1924516 / 25-28: Declared June 11, 73. Publ. 02/23/76. Bull. 43].

The known technical solution does not allow equal channel angular deformation by shear of the tube billet due to a loss of stability of the wall of the billet.

The closest in technical essence and the achieved effect is a known method of manufacturing steeply curved products from tube billets by placing filler in the cavity of the preform, settling the ends and shifting the corresponding sections of the preform in the direction perpendicular to its axis when creating pressure in the filler during manufacture, which is maintained continuously regulation of the amount of filler, and the shear rate is chosen within 1 ... 0.85 of the upsetting speed of the ends and is also kept constant at that carry out a shift or the middle part of the workpiece relative to the end, or the shift of one section of the workpiece relative to another (AS No. 1021060 USSR, MKI3 B21D 9/00).

The disadvantage of this method is that the deformation of the tube stock obtained in the process of forming is insufficient for the formation of a nanocrystalline structure of the material of the workpiece.

A prototype of a device for implementing the method is a device for hydraulic stamping of hollow products with a stepped axis from tube blanks, which includes a detachable matrix having a central movable liner, consisting of push and support half liners, as well as axial compression punches of the tube billet (A.S. No. 593768, CL B21C 37/29, 1976).

The known device does not allow to implement the proposed method due to the fact that the push and support liners are not designed to reverse the shear process of the central part of the workpiece.

The technical result of the invention is the production of a nanocrystalline metal structure in tube billets by cyclically increasing the total degree of shear strain in the center of plastic deformation of the workpiece by controlling the stiffness of the stress-strain state of the deformable material.

To achieve this technical result, the preform cavity is filled with filler, stepwise deformation of the preform is carried out by the end faces by moving axial punches and shifting its middle part relative to the end sections in a direction perpendicular to its axis, while at the odd stage of deformation during shear, constant pressure is created in the filler, by adjusting its quantity, and a constant shear rate, chosen within the range of 1 ... 0.85 of the upsetting speed of the ends, at the end of the odd stage d deformation of the workpiece stops the upsetting of its ends, maintains the tightness of the cavity of the workpiece, and at an even stage, shift the middle part of the workpiece in the opposite direction to the previous step to give the workpiece an initial rectilinear state, while providing a predetermined ratio of shear rates of the middle zone of the workpiece in the range 1 ... 1.15 the speed of movement of the axial punches, turn the workpiece through an angle relative to its axis, then carry out the odd stage of deformation, while at the odd stage de the formation of the shift of the middle part of the workpiece is carried out in the direction coinciding with its direction at an even stage of deformation.

And the device comprises a detachable matrix in the form of upper and lower half-matrices with a central hole, a central liner in the form of a pressure and support half-liners, placed in the central hole of the detachable matrix with the formation of channels, axial compression punches of the tube stock, hydraulic cylinders with rods, rods placed in the said channels, the cross-sectional shape of which corresponds to the cross-sectional shape of the pipe billet, hydraulic cylinders with rods whose axes are perpendicular to the axes of the rods, and the ends of the rods on one side have the possibility of interaction with the surface of the workpiece, and on the other hand with the rods of the aforementioned hydraulic cylinders, while the rods and hydraulic cylinders are placed in pairs in the channels of the upper and lower half-matrices.

The accompanying drawings show the essence of the proposed method and a diagram of a device for its implementation.

Figure 1. The initial position of the pipe billet before performing the first, odd stage of deformation of the pipe billet;

Figure 2. Section AA of FIG. 1;

Figure 3. Section BB of FIG. 1;

Figure 4. The final position of the first, odd stage of deformation of the tube stock with the implementation of shear deformation in the center of plastic deformation;

Figure 5. The initial position of the pipe billet before the second, even stage of deformation of the pipe billet;

6. The final position of the second, even stage of deformation of the workpiece;

7. An example of a rotation of a pipe billet at a certain angle around its axis before the implementation of the third, odd stage of deformation of the pipe billet;

Fig. 8. The initial position of the device and the tube stock before performing the first, even stage of deformation of the tube stock;

Fig.9. Section B-B of Fig. 8 .;

Figure 10. Section G-G of Fig. 8;

11. The position of the device and the deformed tube billet at the final stage of the first, odd stage of deformation;

Fig. 12. The initial position of the device and the deformed tube billet before performing the second, even stage of billet deformation;

Fig.13. The final position of the device and the deformed tube billet at the end of the second even stage of the tube billet deformation before the third, odd stage of deformation;

Fig.14. The final position of the device and the deformed tube billet at the end of the third, odd stage of tube billet deformation;

The implementation of the method of obtaining a nanocrystalline structure in tube blanks and the operation of the device are as follows.

Tubular billet 1 (figure 1) is installed in the stream of the stamp, consisting of a fixed upper 2 and lower 3 half-matrices having a plane of the connector perpendicular to the plane of the drawing. The upper half-liner 4 is introduced from above into the central hole of the half-matrix 2 from the top until it contacts the surface of the tube billet 1. The lower half-liner 5 is contacted below from the workpiece 1. In the closed position, the half-liners 4 and 5 form a movable liner, the channel of which covers the workpiece 1. On the lateral faces of the half-liner 4 there are made semi-channels (FIG. 2), for example, of a semicircular shape, and on a half-liner 5 (FIG. 3) there are protrusions, also of a semicircular shape, in contact with the corresponding channels made on the lower semi-matrix 3.

Having installed the tube billet in the die stream, they begin the first, odd stage of its deformation. To do this, counter synchronous movement is reported to axial punches 6 and 7, providing their force contact with the ends of the workpiece, while sealing its cavity. After this, the movement of the axial punches is stopped. Then, through the axial channels made in the punches 6 and 7, air is removed from the billet cavity, filling its cavity with a filler, for example, machine oil, pumped by a high pressure source, for example, a multiplier (not shown), hydraulically connected, for example, with the axial punch channel 6. After removing air from the cavity of the workpiece 1, the channel of the axial punch 7 is closed, a filler is added to the cavity of the workpiece 1 from the high pressure source, creating a certain hydrostatic pressure q. Then, the axial punches 6 and 7 are informed of the synchronous oncoming movement towards each other. At the same time, a downward movement with force P (P <F) is reported to the movable liner, providing a predetermined ratio of speeds between the moving axial punches 6 and 7 and the liner.

-образный крутоизогнутый полуфабрикат 8. На заключительной стадии первого, нечетного этапа деформирования заготовки прекращают встречное перемещение осевых пуансонов 6, 7 и перемещение вниз подвижного вкладыша. Приступают к выполнению следующего, четного этапа деформирования заготовки. Для этого уменьшают силы Q осевых пуансонов 6 и 7 до величины Q' (фиг.5), достаточной для герметизации полости полуфабриката 8 и сохранения в ней высокого гидростатического давления q, прекращая тем самым осадку торцов заготовки. Затем силу F (фиг.4) увеличивают до величины Р' (фиг.5), а силу Р (фиг.4) снижают до величины силы F (фиг.5). Далее сообщают перемещение вверх подвижному вкладышу и синхронное с ним перемещение друг от друга осевым пуансонам 6 и 7, выдерживая заданное соотношение скоростей между подвижным вкладышем и осевыми пуансонами. При этом под действием силы Р' и высокого гидростатического давления q

-образный крутоизогнутый полуфабрикат деформируют в первоначальную прямолинейную форму исходной заготовки (фиг.6), удваивая тем самым эквивалентную деформацию, получаемую материалом трубной заготовки. На этом заканчивают четный этап деформирования заготовки.Under the action of axial forces Q (Fig. 4), applied to the workpiece 1 by punches 6 and 7, high hydrostatic pressure of the filler q in the cavity of the workpiece and load P from the side of the movable insert, the pipe workpiece is deformed into

-shaped curved semi-finished product 8. At the final stage of the first, odd stage of deformation of the workpiece, the onward movement of the axial punches 6, 7 and the downward movement of the movable insert are stopped. Proceed to the next, even stage of deformation of the workpiece. To do this, reduce the force Q of the axial punches 6 and 7 to a value of Q '(Fig. 5), sufficient to seal the cavity of the semi-finished product 8 and maintain a high hydrostatic pressure q in it, thereby stopping the settlement of the ends of the workpiece. Then, the force F (Fig. 4) is increased to a value of P '(Fig. 5), and the force P (Fig. 4) is reduced to a value of the force F (Fig. 5). Next, the upward movement of the movable liner and synchronous movement from each other to the axial punches 6 and 7 are reported, maintaining a predetermined ratio of speeds between the movable liner and the axial punches. Moreover, under the action of the force P 'and high hydrostatic pressure q

-shaped curved semi-finished product is deformed into the initial rectilinear shape of the original billet (Fig.6), thereby doubling the equivalent deformation obtained by the material of the pipe billet. This completes the even stage of deformation of the workpiece.

Further, the preform shaping can again be continued according to the scheme for implementing the odd stage of deformation, or, to increase the efficiency of creating a nanocrystalline structure of the preform material, before performing the odd stage of deformation, the preform is turned at a certain angle, for example, 90 °, an angle relative to its axis and then the odd stage of deformation is realized .

The turn of the workpiece relative to its axis is carried out, for example, after completing an even stage of deformation as follows. After giving the billet a rectilinear shape again in its cavity, high hydrostatic pressure is released to atmospheric pressure (in this case, the diameter of the tube billet is reduced by the amount of the elastic component of the deformation), and axial punches 6 and 7 are reported to move in one direction, for example, to the left in the direction of arrow A (Fig. 7). In this case, the tube stock is pushed out of the movable insert and half-matrices 2 and 3, providing the necessary conditions for its rotation by a certain angle around its axis in the direction of arrow M relative to the initial position. The workpiece is returned to its original position before deformation by moving the axial punches to their original position, that is, by moving them to the right.

-образного полуфабриката на четном этапе его деформирования, значительно превышает силу Р нечетного этапа ее формоизменения вследствие пассивного участия, в данном случае, в деформировании заготовки осевых пуансонов, необходимости преодоления сил трения, возникающих между заготовкой и поверхностями устройства, а также преодоления тянущей силы, направленной навстречу силе Р' и возникающей вследствие разницы площадей контакта трубной заготовки, в полости которой находится наполнитель под давлением q, с полувкладышами 4 и 5, показанных на фиг.2 и 3.Force P 'applied to the central zone of the deformable

-shaped semi-finished product at an even stage of its deformation, significantly exceeds the force P of the odd stage of its shaping due to passive participation, in this case, in the deformation of the workpiece of the axial punches, the need to overcome the friction forces arising between the workpiece and the surfaces of the device, as well as to overcome the pulling force directed towards the force P 'and arising due to the difference in the contact areas of the tube stock, in the cavity of which there is a filler under pressure q, with half-liners 4 and 5, shown on figure 2 and 3.

To increase the intensity and uniformity of the formation of the nanocrystalline structure of the material in the circumferential direction along the workpiece sections at the odd stage of deformation, the shift of the middle part of the workpiece is carried out in the direction coinciding with its direction at the even stage of deformation.

For this, the tube billet 9 (Fig. 8) is installed in a device having a stream formed by a fixed upper 10 and lower 11 half-matrix having a plane of the connector perpendicular to the plane of the drawing. The upper half-liner 12 is introduced into the central hole of the half-matrix 10 from the top until it contacts the surface of the tube billet 9. The lower half-liner 13 is contacted below from the workpiece 9. In the position F closed by forces F, the half-liners 12 and 13 form a movable liner, the channel of which covers the blank 9. On the lateral faces of the half-liners 12 and 13 are made semi-channels (Fig.9), for example, a semicircular shape. Similar channels are made in the central holes of the half-shells 10 and 11 (Fig. 8), forming in sections BB and GG with half-channels of the half-shells 12 and 13 holes 13, 14, 15 and 16, having a diameter equal to the outer diameter of the tube stock 9 (Fig.9, 10). Cylindrical rods 17, 18, 19, and 20 are placed in the marked holes, contacting ends opposite to those located from the tube stock with flat flats made on cylindrical rods 21, 22, 23, and 24. Opposite ends of the rods 17, 18, 19, and 20 facing the billet 9, have a semicircular shape and cover the outer surface of the tube billet 9, minimizing the surface of the tube billet not covered by the hard surfaces of the device. Each of the rods 21, 22, 23 and 24 is rigidly connected with its piston, which is placed in the hydraulic cylinders. In the initial position, the rods of the device are reduced towards each other, in contact with the liners 12 and 13, as shown in Fig. 8.

Having installed the pipe billet 9 in the stream of the device, begin the first, odd stage of its deformation. For this, a counter synchronous movement is reported to the axial punches 25 and 26, ensuring their force contact with the ends of the workpiece and thereby sealing its cavity. After this, the movement of the axial punches is stopped. Then, through the axial channels made in the punches, air is removed from the billet cavity and the cavity is filled with a filler, for example, machine oil, pumped by a high pressure source, for example, a multiplier (not shown), hydraulically connected, for example, with an axial punch channel 25. By removing air from the cavity of the workpiece 9 overlaps the channel, for example, of the axial punch 26, and filler is added to the cavity of the workpiece 9 from the high pressure source, creating a certain hydrostatic pressure q.

Then, the odd, first stage of deformation of the workpiece is performed. In this case, the rods 23 and 24 are diverted from each other, and the axial punches 25 and 26 are informed of the synchronous oncoming movement towards each other. At the same time, a downward movement with force P (P <F) is reported to the movable liner, providing a predetermined ratio of speeds between the moving axial punches 25, 26 and the liner.

-образный крутоизогнутый полуфабрикат 31.Under the action of axial forces Q (Fig. 11), applied to the workpiece 9 by punches 25 and 26, of high hydrostatic pressure of the filler q in the cavity of the workpiece and the load P from the side of the movable insert, the pipe workpiece is deformed into

-shaped curved prefabricated 31.

-образный крутоизогнутый полуфабрикат деформируют в первоначальную прямолинейную форму исходной заготовки (фиг.13), удваивая тем самым эквивалентную деформацию, получаемую материалом трубной заготовки. На этом заканчивают четный этап деформирования заготовки. При этом стержни 19, 20 и штоки 23, 24 устройства возвращают в исходное положение (фиг.8).At the final stage of the first, odd stage of deformation of the workpiece, the oncoming movement of the axial punches 25, 26 and the downward movement of the movable insert are stopped. Proceed to the next, even stage of deformation of the workpiece. To do this, reduce the force Q of the axial punches 25 and 26 to a value of Q '(Fig. 12), sufficient to seal the cavity of the semi-finished product 27 and maintain a high hydrostatic pressure q in it, thereby stopping the settlement of the ends of the workpiece. Then, the force F (Fig. 11) is increased to a value of P '(Fig. 12), and the force P (Fig. 11) is reduced to a value of the force F (Fig. 12). Next, the upward movement of the movable liner and synchronous movement from each other to the axial punches 25 and 26 are reported, maintaining a predetermined ratio of speeds between the movable liner and the axial punches. Moreover, under the action of the force P 'and high hydrostatic pressure q

-shaped curved semi-finished product is deformed into the initial rectilinear shape of the original billet (Fig.13), thereby doubling the equivalent deformation obtained by the material of the pipe billet. This completes the even stage of deformation of the workpiece. In this case, the rods 19, 20 and the rods 23, 24 of the device are returned to their original position (Fig. 8).

Further, depending on the required degree of grinding of the grains of the material or obtaining the required degree of misorientation of the grain boundaries of the pipe billet material or other tasks, the deformation of the billet can be continued according to several scenarios.

-образного полуфабриката. Дальнейшее деформирование ступенчатого полуфабриката, то есть четный этап, может заключаться в формоизменении полуфабриката со ступенчатой осью в полуфабрикат с прямолинейной осью, по ранее описанной схеме деформирования.Firstly, the next, odd stage of deformation of the workpiece can consist in a further upward shift of the middle zone of the workpiece (Fig. 14) relative to the position achieved in the even stage of deformation shown in Fig. 13. To do this, the rods 21 and 22 are diverted from each other, reverse the movement of the axial punches 25 and 26, applying an axial load Q to them. At the same time, the movable insert continues to move upward, maintaining a predetermined ratio of speeds between the axial punches and the insert. This step is completed upon receipt, for example, of a mirror relative to the previous step form

-shaped semi-finished product. Further deformation of the stepped semifinished product, that is, an even stage, may consist in shaping the semifinished product with a stepped axis into a semifinished product with a straight axis, according to the previously described deformation pattern.

In this case, by providing, to a first approximation, the same total deformations of the material in the concave and convex radii of the knees of the pipe billet, obtained in total at the even and odd stages of deformation, a more uniform distribution of the nanocrystalline structure over the radial sections of the inter-knee zones of the semi-finished product is ensured.

Secondly, the next, odd stage of deformation of the workpiece can consist in performing a shift of the middle zone of the workpiece down with a preliminary turn of the workpiece by a certain angle around its initial position, for example, as shown in Fig.7. Then the preform shaping can again be continued according to the scheme of the even deformation stage.

Moreover, the number of stages of deformation of the pipe billet and their sequence of implementation are determined by the goals and objectives of the practice.

An additional reserve for increasing the efficiency of creating a nanocrystalline structure of the workpiece material according to the proposed method is the ability to control the scheme of the stress-strain state of the material in the centers of plastic deformation located in the knee zones of the wrought workpiece at angles α = π / 4 (Fig. 4) to the initial axis of the workpiece. This is realized by controlling the relative velocities of the axial punches and the movable matrix. For example, at an odd stage of deformation of the workpiece, a decrease in the speed of movement of the movable matrix (Vm) compared to the speed of movement of the axial punches (Vp), approximately up to a value of 0.85 of the speed of movement of the axial punches, (i.e. ) allows you to impose additional compressive stresses on the plastic deformation zone of the workpiece, which increase the ductility of the material. Conversely, at an even stage of deformation of the workpiece, an increase in the speed of movement of the movable matrix by an amount approximately up to 1.15 of the speed of movement of the axial punches creates the same effect of increasing the ductility of the material in the center of plastic deformation. In addition to intensifying the formation of the nanocrystalline structure of the workpiece material, this allows us to treat tube blanks having a reduced, under normal conditions, material ductility.

The range of application of the proposed method and device is not limited to obtaining the nanocrystalline structure of the material of the tube blanks of circular cross section, but can be expanded to form the nanocrystalline structure of the material of the tube blanks having cross sections in the form of a square, rectangle, or other cross-sections other than round.

The application of the proposed method and device for its implementation allows us to implement not only equal channel pressing of tube blanks with various cross-sectional shapes, but also to control the formation of increased mechanical properties of the tube material semi-finished products, while ensuring high labor productivity and the quality of the nanocrystalline structure.

Claims (4)

1. A method of obtaining a nanocrystalline structure of a material in tube billets, including filling the billet cavity with filler, stage-by-stage deformation of the billet by end face precipitation by moving axial punches and shifting its middle part relative to the end sections in a direction perpendicular to its axis, while at the odd stage of deformation during the shift create a constant pressure in the filler by adjusting its amount and a constant shear rate, selected in the range of 1 ... 0.85 sedimentation rate ends, at the end of the odd stage of deformation of the workpiece, the ends of the ends are stopped, the cavity of the workpiece is sealed, and at the even stage, the middle part of the workpiece is shifted in the opposite direction to the previous step to give the workpiece an initial rectilinear state, while providing a predetermined ratio of the shear rate of the middle zone of the workpiece in within the range of 1 ... 1.15 of the axial punches moving speed, turn the workpiece through an angle relative to its axis, then carry out an odd stage of deformation Niya. 2. The method according to claim 1, characterized in that at an odd stage of deformation, the shift of the middle part of the workpiece is carried out in the direction coinciding with its direction at an even stage of deformation. 3. A device for producing a nanocrystalline structure of a material in tube billets, comprising a detachable matrix in the form of upper and lower half-matrices with a central hole, a central liner in the form of a pressure and support half-liners placed in the central hole of the detachable matrix with the formation of channels, axial compression punches of the tube billet, hydraulic cylinders with rods, rods placed in the said channels, the cross-sectional shape of which corresponds to the cross-sectional shape of the pipe billet, hydraulic cylinders with rods, axes ryh perpendicular to the axes of rods, the ends of the rods on one side have the ability to interact with the workpiece surface, and on the other side - with rods of said cylinders. 4. The device according to claim 3, characterized in that the rods and hydraulic cylinders are placed in pairs in the channels of the upper and lower half-matrices.

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