Extrusion device and method for improving toughness performance of metal material

Abstract

The invention belongs to the technical field of metal plastic processing, and particularly relates to an extrusion device and method for improving the toughness of a metal material. The device comprises a fixing mechanism, an extrusion die, a lifting extrusion driving mechanism, an upper extrusion assembly and a lower extrusion mechanism, the lifting extrusion driving mechanism, the extrusion die and the lower extrusion mechanism are arranged on the fixing mechanism from top to bottom, and the upper extrusion assembly is connected with the driving end of the lifting extrusion driving mechanism. The upper extrusion assembly and the lower extrusion mechanism are in sliding fit with the upper end and the lower end of the extrusion die correspondingly, an extrusion cavity is formed between the upper extrusion assembly and the lower extrusion mechanism, and the upper extrusion assembly and the lower extrusion mechanism cooperate to achieve plastic deformation extrusion of a metal blank in the extrusion cavity. The method is easy and convenient to operate and high in machining efficiency, grains can be effectively refined, the strength and plasticity of the material are improved, and then the mechanical performance of the material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal plastic processing, and particularly relates to an extrusion device and method for improving the strength and toughness of metal materials. Background Art

[0002] Severe Plastic Deformation (SPD) is an emerging plastic deformation method that can introduce large strains during the deformation process (it is difficult to achieve true strains greater than 1 in traditional plastic deformation), thereby effectively refining (submicron or nanometer scale) metals and obtaining complete large-scale bulk specimens. By controlling the microstructure during the deformation process, bulk nanomaterials with high strength and high plasticity can be obtained at the same time. High Pressure Torsion (HPT) is a special plastic deformation process that applies torque on the cross section of the deformed body by applying pressure in the height direction of the deformed body through active friction, causing the deformed body to produce axial compression and tangential shear deformation.

[0003] Although the high-pressure torsion process is an effective way to prepare ultrafine-grained materials, the existing die structure still has the disadvantages of limited plastic deformation capacity of the blank and low working efficiency of the die in practical applications. During the high-pressure torsion extrusion process, the material undergoes strong shear deformation at the corner of the die, which easily causes the blank to deform, crack, or even break along the shear stress direction, ultimately making it impossible to continue the subsequent extrusion deformation. Therefore, it is urgent to study the friction of the internal grain refinement of the microscopic high-pressure torsion metal during the severe plastic deformation and the relationship between the characterization of the macroscopic extrusion device operation process (including but not limited to extrusion size, pressure, speed, electric field, temperature field, ultrasonic and other gradient process parameters), and then optimize the extrusion efficiency. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide an extrusion device and method for improving the strength and toughness of metal materials, so as to study the friction of internal grain refinement of micro-high-pressure torsion metal during severe plastic deformation, and its relationship with the operating process characterization of the macro-extrusion device, so as to optimize the extrusion efficiency.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: On the one hand, the present invention provides an extrusion device for improving the strength and toughness of metal materials, comprising a fixing mechanism, an extrusion die, a lifting extrusion drive mechanism, an upper extrusion assembly and a lower extrusion mechanism, wherein the lifting extrusion drive mechanism, the extrusion die and the lower extrusion mechanism are arranged on the fixing mechanism from top to bottom, the upper extrusion assembly is connected to the driving end of the lifting extrusion drive mechanism, the upper extrusion assembly and the lower extrusion mechanism are respectively slidably matched with the upper and lower ends of the extrusion die, an extrusion cavity is formed between the upper extrusion assembly and the lower extrusion mechanism, and the upper extrusion assembly and the lower extrusion mechanism cooperate to realize the plastic deformation extrusion of the metal blank in the extrusion cavity.

[0006] In one possible implementation, the upper extrusion assembly includes a middle extrusion rod, a hydraulic column I, a hydraulic column II, an extrusion ring and a core mold, wherein the core mold is a hollow structure, and a lateral waist hole for feeding and discharging materials is provided on the upper part of the core mold, the upper end of the core mold is connected to the fixed part of the lifting extrusion drive mechanism, and the middle extrusion rod is slidably matched with the inner cavity of the core mold; the lower end of the core mold is inserted into the inner cavity of the extrusion mold, and the extrusion ring is sleeved on the core mold and slidably matched with the outer surface of the core mold and the inner cavity of the extrusion mold; the top two sides of the extrusion ring are respectively connected to hydraulic column I and hydraulic column II, and the middle extrusion rod, hydraulic column I and hydraulic column II are respectively connected to the driving end of the lifting extrusion drive mechanism; the middle extrusion rod and the extrusion ring are respectively used for forward and reverse alternating reciprocating extrusion.

[0007] In a possible implementation, the lifting and extrusion drive mechanism includes an extrusion rod hydraulic drive chamber I, a middle extrusion rod hydraulic drive chamber and an extrusion rod hydraulic drive chamber II; the upper ends of the hydraulic columns I and II are respectively slidably matched with the extrusion rod hydraulic drive chamber I and the extrusion rod hydraulic drive chamber II, and the extrusion rod hydraulic drive chamber I and the extrusion rod hydraulic drive chamber II respectively hydraulically servo-control the hydraulic columns I and II to rise and fall synchronously; The upper end of the middle extrusion rod is slidably matched with the hydraulic driving chamber of the middle extrusion rod, and the hydraulic servo of the hydraulic driving chamber of the middle extrusion rod controls the lifting of the middle extrusion rod.

[0008] In a possible implementation, the lower extrusion mechanism includes a push rod and a rotating disk, wherein the push rod passes through the rotating disk, and the push rod and the rotating disk are slidably matched, the upper end of the rotating disk is slidably matched with the inner cavity of the extrusion die, and the rotating disk has the freedom of lifting and rotating; the push rod and the middle extrusion rod have the same diameter; The extrusion chamber comprises a middle extrusion chamber located between the middle extrusion rod and the top rod, a shear extrusion chamber located between the core die and the rotating disk, and a torsional friction stirring extrusion chamber located between the extrusion ring and the rotating disk.

[0009] In a possible implementation, the lower extrusion mechanism further includes a rotary drive mechanism, a rotary disk hydraulic cylinder and a push rod lifting drive mechanism, wherein the rotary disk hydraulic cylinder is arranged on the push rod lifting drive mechanism, the lower end of the rotary disk is slidably matched with the inner cavity of the rotary disk hydraulic cylinder, and the rotary disk hydraulic cylinder hydraulic servo controls the lifting of the rotary disk; the rotary drive mechanism is arranged between the extrusion die and the rotary disk hydraulic cylinder, and is connected to the rotary disk, and the rotary drive mechanism provides power for the rotary motion of the rotary disk; The push rod lifting drive mechanism is arranged on the fixing mechanism and is located below the rotating disk hydraulic cylinder. The lower end of the push rod is connected to the push rod lifting drive mechanism, and the upper end of the push rod passes through the rotating disk hydraulic cylinder and the rotating disk in sequence. The push rod lifting drive mechanism is used to drive the push rod to rise and fall.

[0010] In one possible implementation, the rotary drive mechanism includes an upper drive, a lower drive, a small spur gear and a large spur gear, wherein the upper drive and the lower drive are respectively arranged on the extrusion die and the rotating disk hydraulic cylinder, and the rotation axis is collinear, the two ends of the small spur gear are respectively connected to the upper drive and the lower drive, the large spur gear is fixed to the outer side of the rotating disk, and the large spur gear is meshed with the small spur gear, and the axial length of the small spur gear is sufficient to keep the small spur gear and the large spur gear in meshing state when the rotating disk has a maximum lifting stroke.

[0011] In one possible implementation, the push rod lifting drive mechanism includes a push rod hydraulic cylinder, the lower end of the push rod passes through the push rod hydraulic cylinder, and the push rod slides with the inner cavity of the push rod hydraulic cylinder through a piston, and the upper and lower sides of the piston respectively form an upper hydraulic chamber of the push rod and a lower hydraulic chamber of the push rod, and the upper hydraulic chamber of the push rod and the lower hydraulic chamber of the push rod hydraulic servo control the lifting movement of the push rod; the lower end of the push rod passes through the bottom of the push rod hydraulic cylinder and is connected to an ultrasonic generator, and the ultrasonic generator assists the extruded metal in grain refinement through ultrasonic vibration.

[0012] In a possible implementation, the fixing mechanism includes a base, a column, a mold connecting plate and a driving connecting plate, wherein the driving connecting plate is arranged above the base, and the driving connecting plate is connected to the base through two columns, and two ends of the mold connecting plate are respectively slidably matched with the two columns; The lifting extrusion driving mechanism and the lower extrusion mechanism are respectively arranged on the driving connecting plate and the base, and the extrusion die is arranged on the die connecting plate.

[0013] Another aspect of the present invention provides an extrusion method for improving the toughness of a metal material using the above-mentioned device, comprising the following steps: Step S1: the extrusion chamber position is initialized, the space of the shear extrusion chamber and the torsional friction stir extrusion chamber is zero, the top rod is flush with the upper surface of the rotating disk, and the middle extrusion rod is in a high position; Step S2: The metal blank is fed through the lateral waist hole on the upper part of the core mold, and the metal blank falls into the middle extrusion cavity; Step S3: the hydraulic servo controls the extrusion rod to extrude the metal blank; Step S4: the push rod and the rotating disk are synchronously lowered, so that the metal blank is gradually extruded into the shear extrusion chamber and the torsional friction stirring extrusion chamber; Step S5: the extrusion ring rises; at the same time, the ejector rod and the rotating disk gradually descend, and the rotating disk rotates; the middle extrusion chamber continues to vertically extrude the metal blank, the shear extrusion chamber performs layered shear extrusion on the metal blank, and the torsional friction stirring extrusion chamber performs high-pressure torsional grain refinement friction stirring on the metal blank; Step S6: the extrusion ring continues to rise to the set position, and the middle extrusion rod descends to the set position, and then the step S5 is reversed; Step S7: repeating step S5 and step S6 to a specified number of cycles; Step S8: The space of the shear extrusion chamber and the torsional friction stirring extrusion chamber is zero; the middle extrusion rod is at a high position, and the ejector pushes the cylindrical nano-grain finished product to the lateral waist hole for discharge; Step S9: Perform macroscopic mechanical property testing and microscopic material science testing on the nanocrystalline cylindrical finished product.

[0014] The advantages and positive effects of the present invention are as follows: the present invention provides an extrusion device for improving the strength and toughness of metal materials, which completes the internal grain refinement and friction of high-pressure torsion metal through multiple extrusions in forward and reverse cycles, and the extrusion cavity gradient changes gradually during the whole process. Since the stirring friction state of coarse-grained and fine-grained metal grains can be adjusted, metal cracking is effectively avoided, and extrusion efficiency is optimized; the extrusion process of the barrel and the cylinder contains back pressure, which effectively avoids cracking, and has the advantages of reducing material waste and high molding precision due to the crystal refinement of high-pressure torsion metal.

[0015] The present invention can effectively study the friction that characterizes the internal grain refinement of the severe plastic deformation of the micro-high-pressure torsion metal, and characterize the relationship with the operation process of the macro-extrusion device (including but not limited to extrusion size, pressure, speed, electric field, temperature field, ultrasonic and other gradient process parameters), so as to obtain the process parameters for optimizing the extrusion efficiency. Each cycle needs to pass through the area with high linear speed of high-pressure torsion, so the grain uniformity is better and the working efficiency is higher.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 An exploded view of an extrusion device for improving the toughness of metal materials according to the present invention; Figure 2 This is an axonometric diagram of an extrusion device for improving the toughness of metal materials according to the present invention; Figure 3 for Figure 2 A partial enlarged view of the middle part; Figure 4 It is a cross-sectional view of an extrusion device for improving the toughness of metal materials according to the present invention; Figure 5 for Figure 4 A partial enlarged view of point B in the middle; Figure 6 for Figure 4 A partial enlarged view of point C in the middle; Figure 7 It is an axonometric view of the core mold in the present invention; Figure 8 Schematic diagram of the torsional stir friction trajectory for grain refinement in an embodiment of the present invention.

[0019] In the figure: 1-fixed mechanism, 101-base, 102-column, 103-die connecting plate, 104-drive connecting plate, 2-rod, 201-piston, 3-rotating plate, 4-rotating drive mechanism, 401-upper drive, 402-lower drive, 403-small spur gear, 404-large spur gear, 5-extrusion die, 6-lifting extrusion drive mechanism, 7-middle extrusion rod, 8-hydraulic column I, 9-hydraulic column II, 10-ultrasonic generator, 11-middle extrusion chamber, 12-shear extrusion chamber, 13-rod hydraulic cylinder, 14- Torsional friction stirring extrusion chamber, 15-lower hydraulic chamber of push rod, 16-upper hydraulic chamber of push rod, 17-hydraulic driving chamber I of extrusion rod, 18-middle hydraulic driving chamber of extrusion rod, 19-hydraulic driving chamber II of extrusion rod, 20-hydraulic driving chamber of rotating disk lifting, 21-hydraulic cylinder of rotating disk, 22-extrusion ring, 23-core mold, 2301-lateral waist hole, 24-starting point, 25-first inflection point, 26-second inflection point, 27-vortex running track, 28-gradient pitch spiral line, 29-third inflection point, 30-fourth inflection point, 31-end point. DETAILED DESCRIPTION

[0020] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0022] An embodiment of the present invention provides an extrusion device for improving the toughness of metal materials, which can effectively study the relationship between the friction of micro-high pressure torsion method internal grain refinement and the macro-extrusion device operation process characterization, and thus obtain the process parameters for optimizing the extrusion efficiency. Figures 1 to 8 As shown, the extrusion device for improving the strength and toughness of metal materials includes a fixing mechanism 1, an extrusion die 5, a lifting extrusion drive mechanism 6, an upper extrusion assembly and a lower extrusion mechanism, wherein the lifting extrusion drive mechanism 6, the extrusion die 5 and the lower extrusion mechanism are arranged on the fixing mechanism 1 from top to bottom, the upper extrusion assembly is connected to the driving end of the lifting extrusion drive mechanism 6, the upper extrusion assembly and the lower extrusion mechanism are respectively slidably matched with the upper and lower ends of the extrusion die 5, an extrusion cavity is formed between the upper extrusion assembly and the lower extrusion mechanism, and the upper extrusion assembly and the lower extrusion mechanism cooperate to realize the plastic deformation extrusion of the metal blank in the extrusion cavity.

[0023] See also Figure 1 and Figure 2 As shown, in an embodiment of the present invention, the fixing mechanism 1 includes a base 101, a column 102, a mold connecting plate 103 and a driving connecting plate 104, wherein the driving connecting plate 104 is arranged above the base 101, and the driving connecting plate 104 is detachably connected to the base 101 through two columns 102 as a whole, and the two ends of the mold connecting plate 103 are respectively slidably matched with the two columns 102; the lifting extrusion driving mechanism 6 and the lower extrusion mechanism are respectively arranged on the driving connecting plate 104 and the base 101, and the extrusion mold 5 is arranged on the mold connecting plate 103.

[0024] See also Figure 1-2 , Figure 4 and Figure 6-7As shown, in an embodiment of the present invention, the upper extrusion assembly includes a middle extrusion rod 7, a hydraulic column I8, a hydraulic column II9, an extrusion ring 22 and a core mold 23, wherein the core mold 23 is a hollow structure, and a lateral waist hole 2301 for feeding and discharging materials is provided on the upper part of the core mold 23, the upper end of the core mold 23 is connected to the fixed part of the lifting extrusion drive mechanism 6, and the middle extrusion rod 7 is slidably matched with the inner cavity of the core mold 23; the lower end of the core mold 23 is inserted into the inner cavity of the extrusion mold 5, and the extrusion ring 22 is sleeved on the core mold 23 and slidably matched with the outer surface of the core mold 23 and the inner cavity of the extrusion mold 5, that is, a cylindrical pair is formed between the outer cylinder of the extrusion ring 22 and the inner cavity of the extrusion mold 5, and the inner hole of the extrusion ring 22 and the outer cylinder of the core mold 23 form a cylindrical pair. The extrusion ring 22 is annular, and the two sides of the top of the extrusion ring 22 are respectively connected to the hydraulic column I8 and the hydraulic column II9, and the middle extrusion rod 7, the hydraulic column I8 and the hydraulic column II9 are respectively connected to the driving end of the lifting extrusion drive mechanism 6; the middle extrusion rod 7 and the extrusion ring 22 are respectively used for forward and reverse alternating reciprocating extrusion.

[0025] See also Figure 4 As shown, in the embodiment of the present invention, the lifting and extrusion driving mechanism 6 includes an extrusion rod hydraulic driving chamber Ⅰ17, a middle extrusion rod hydraulic driving chamber 18 and an extrusion rod hydraulic driving chamber Ⅱ19; the upper ends of the hydraulic columns Ⅰ8 and Ⅱ9 are respectively slidably matched with the extrusion rod hydraulic driving chamber Ⅰ17 and the extrusion rod hydraulic driving chamber Ⅱ19, and the extrusion rod hydraulic driving chamber Ⅰ17 and the extrusion rod hydraulic driving chamber Ⅱ19 respectively hydraulically servo control the hydraulic columns Ⅰ8 and Ⅱ9 to rise and fall synchronously; the upper end of the middle extrusion rod 7 is slidably matched with the middle extrusion rod hydraulic driving chamber 18, and the middle extrusion rod hydraulic driving chamber 18 hydraulically servo controls the lifting and falling of the middle extrusion rod 7. The hydraulic columns Ⅰ8, Ⅱ9 and the middle extrusion rod 7 perform servo lifting and extrusion movements to control the lifting and falling movements of the extrusion ring 22.

[0026] See also Figure 4 and Figure 6 As shown, in the embodiment of the present invention, the lower extrusion mechanism includes a push rod 2 and a rotating disk 3, wherein the push rod 2 passes through the rotating disk 3, and the push rod 2 and the rotating disk 3 are slidably matched, the upper end of the rotating disk 3 is slidably matched with the inner cavity of the extrusion mold 5, and the rotating disk 3 has the freedom of lifting and rotating; the diameter of the push rod 2 is equal to that of the middle extrusion rod 7; the extrusion cavity includes a middle extrusion cavity 11 located between the middle extrusion rod 7 and the push rod 2, a shear extrusion cavity 12 located between the core mold 23 and the rotating disk 3, and a torsional friction stirring extrusion cavity 14 located between the extrusion ring 22 and the rotating disk 3, the crystal refinement of the middle extrusion cavity 11 is mainly the axial pressure of the metal blank, the crystal refinement of the shear extrusion cavity 12 is mainly the axial torsional shear force of the metal blank, and the crystal refinement of the torsional friction stirring extrusion cavity 14 is mainly the coupling of the axial pressure and torsional shear force of the metal blank.

[0027] Furthermore, the lower extrusion mechanism also includes a rotary drive mechanism 4, a rotating disk hydraulic cylinder 21 and a push rod lifting drive mechanism, wherein the rotating disk hydraulic cylinder 21 is arranged on the push rod lifting drive mechanism, the lower end of the rotating disk 3 is slidably matched with the inner cavity of the rotating disk hydraulic cylinder 21, and a rotating disk lifting hydraulic drive chamber 20 is formed in the rotating disk hydraulic cylinder 21, and the rotating disk lifting hydraulic drive chamber 20 hydraulic servo controls the lifting and lowering of the rotating disk 3; the rotary drive mechanism 4 is arranged between the extrusion mold 5 and the rotating disk hydraulic cylinder 21, and is connected to the rotating disk 3, and the rotary drive mechanism 4 provides power for the rotational movement of the rotating disk 3; the push rod lifting drive mechanism is arranged on the base 101 of the fixing mechanism 1, and is located below the rotating disk hydraulic cylinder 21, the lower end of the push rod 2 is connected to the push rod lifting drive mechanism, and the upper end of the push rod 2 passes through the rotating disk hydraulic cylinder 21 and the rotating disk 3 in sequence, and the push rod lifting drive mechanism is used to drive the push rod 2 to rise and fall.

[0028] See also Figure 5 As shown, in the embodiment of the present invention, the rotary drive mechanism 4 includes an upper drive 401, a lower drive 402, a small spur gear 403 and a large spur gear 404, wherein the upper drive 401 and the lower drive 402 are respectively arranged on the extrusion die 5 and the rotating disk hydraulic cylinder 21, and the rotation axis is collinear, the two ends of the small spur gear 403 are respectively connected to the upper drive 401 and the lower drive 402, the large spur gear 404 is fixed on the outer side of the rotating disk 3, and the large spur gear 404 is meshed with the small spur gear 403. The upper drive 401 and the lower drive 402 drive the small spur gear 403 to rotate, thereby driving the rotating disk 3 to rotate through the large spur gear 404. The upper drive 401 and the lower drive 402 are preferably servo hydraulic motors and planetary reducers, and the rotating disk 3 can perform two-axis coupled motion of lifting and rotating.

[0029] Furthermore, the axial length of the small spur gear 403 satisfies the requirement that the small spur gear 403 and the large spur gear 404 remain in meshing state when the rotating disk 3 has the maximum lifting stroke. In this embodiment, the small spur gear 403 is a simply supported beam configuration, so the use of dual drive can effectively alleviate the fatigue and reliability problems of the coupling of bending stress and torsional stress of the gear shaft cantilever configuration.

[0030] See also Figure 4 As shown, in the embodiment of the present invention, the push rod lifting drive mechanism includes a push rod hydraulic cylinder 13, the lower end of the push rod 2 passes through the push rod hydraulic cylinder 13, and the push rod 2 slides with the inner cavity of the push rod hydraulic cylinder 13 through the piston 201, and the upper and lower sides of the piston 201 respectively form a push rod upper hydraulic chamber 16 and a push rod lower hydraulic chamber 15, and the push rod upper hydraulic chamber 16 and the push rod lower hydraulic chamber 15 hydraulic servo control the lifting and lowering movement of the push rod 2; the lower end of the push rod 2 passes through the bottom of the push rod hydraulic cylinder 13 and is connected to the ultrasonic generator 10, and the ultrasonic generator 10 assists the extruded metal to refine the grain through ultrasonic vibration. The rotating disk hydraulic cylinder 21 is arranged on the top of the push rod hydraulic cylinder 13.

[0031] In this embodiment, the metal blank includes but is not limited to aluminum and aluminum alloys, copper and copper alloys, pure iron, carbon steel, nickel and other metal alloys. In this embodiment, the preferred grade 6201 aluminum alloy cylindrical blank, the extrusion pressure is 0~10GPa, and the rotation speed of the rotating disk 3 is 0~30r / min. Heating coils, cooling water channels and temperature sensors can be arranged on the outside of the extrusion die 5 to achieve process temperature control of the extrusion process. The extrusion die 5 is preferably made of zirconia ceramics with good insulation performance. Electrodes are inserted into the middle extrusion rod 7, hydraulic column I8, hydraulic column II9, push rod 2 and rotating disk 3 to achieve electric field assisted grain refinement during the extrusion process. The base 101 is connected to the ground and insulated. The present invention can make cylindrical profiles without disassembling the extrusion device. Disassembling the extrusion device can manufacture barrel profiles, water cup profiles, and rotating body profiles with an H-shaped axial cross section.

[0032] Figure 8 Schematic diagram of the grain refinement torsional stir friction trajectory in the embodiment of the present invention; see Figure 8 As shown, the grain extrusion process: from the starting point 24 to the first inflection point 25, it runs in the middle extrusion chamber 11, and the axial pressure is dominant. From the first inflection point 25 to the second inflection point 26, it is the transition from the middle extrusion chamber 11 to the shear extrusion chamber 12, and the grain space trajectory changes from axial to horizontal tangential flow. The running trajectory of the grains in the shear extrusion chamber 12 is a vortex running trajectory 27, and the outer edge of the vortex running trajectory 27 is a gradient pitch spiral line 28 along the axial direction. The crystal refinement in the shear extrusion chamber 12 is mainly the axial torsional shear force of the metal blank. From the third inflection point 29 to the fourth inflection point 30, it is the transition from the shear extrusion chamber 12 to the torsional friction stir extrusion chamber 14, and the grain space trajectory changes from horizontal tangential to axial flow. From the fourth inflection point 30 to the end point 31, it runs in the torsional friction stir extrusion chamber 14, and the crystal refinement of the torsional friction stir extrusion chamber 14 is mainly the coupling of axial pressure and torsional shear force of the metal blank.

[0033] Specifically, the vortex running trajectory 27 gradually increases in speed from the inside to the outside in the radial direction, the friction shear force gradually increases, and the friction is intense; the gradient pitch spiral line 28 gradually slows down in speed in the axial direction away from the rotating disk 3, the friction shear force gradually decreases, and the pitch gradually increases.

[0034] In the present invention, the metal flow direction in the outer ring extrusion cavity is oblique to the rotating friction surface, and a gradual change of the oblique angle can be achieved in the process flow, which helps the material to produce axial compression, tangential shear deformation and strain, has a significant effect on grain refinement, and significantly improves the mechanical properties, plasticity and toughness of the material, and improves the strength, hardness, fatigue performance and corrosion resistance of the material.

[0035] The present invention achieves high-pressure torsion metal violent plastic deformation and internal grain refinement friction by cyclically extruding in both forward and reverse directions. The extrusion cavity gradient changes gradually during the whole process, thereby effectively avoiding metal cracking and exploring the optimization of extrusion efficiency. The barrel and cylindrical extrusion process contains back pressure, which effectively avoids metal cracking. The present invention has the beneficial effects recorded in all public documents on equal-diameter corner metal crystal refinement, which will not be repeated here.

[0036] In another embodiment of the present invention, there is provided an extrusion method for improving the toughness of a metal material using the device in the above embodiment, comprising the following steps: Step S1: the extrusion chamber position is initialized, the space of the shear extrusion chamber 12 and the torsional friction stirring extrusion chamber 14 is zero, the top rod 2 is flush with the upper surface of the rotating disk 3, and the middle extrusion rod 7 is in a high position; Step S2: The metal blank is fed through the lateral waist hole 2301 on the upper part of the core mold 23, and the metal blank falls into the middle extrusion cavity 11; Step S3: the extrusion rod 7 is controlled by hydraulic servo to extrude the metal blank; Step S4: the push rod 2 and the rotating disk 3 are synchronously lowered, so that the metal blank is gradually extruded into the shear extrusion chamber 12 and the torsional friction stirring extrusion chamber 14; Step S5: the extrusion ring 22 rises; at the same time, the push rod 2 and the rotating disk 3 gradually descend, and the rotating disk 3 rotates; the middle extrusion chamber 11 continues to vertically extrude the metal blank, the shear extrusion chamber 12 performs layered shear extrusion on the metal blank, and the torsional friction stirring extrusion chamber 14 performs high-pressure torsional grain refinement friction stirring on the metal blank; Step S6: the extrusion ring 22 continues to rise to the set position, and the middle extrusion rod 7 descends to the set position, and then the step S5 is reversed; Step S7: repeating step S5 and step S6 to a specified number of cycles; Step S8: The space of the shear extrusion chamber 12 and the torsional friction stirring extrusion chamber 14 is zero; the middle extrusion rod 7 is at a high position, and the push rod 2 pushes the cylindrical finished nano-grain product to the lateral waist hole 2301 to discharge the material; Step S9: Perform macroscopic mechanical property testing and microscopic material science testing on the nanocrystalline cylindrical finished product.

[0037] The above steps can make many nano-grain cylindrical products with different extrusion processes. The friction environment of the internal grain refinement of the high-pressure torsion metal under severe plastic deformation can be adjusted online, and the characterization relationship between the friction ring of the internal grain refinement of the high-pressure torsion metal under severe plastic deformation and ultrasonic assisted processing, process temperature and auxiliary electric field can be effectively studied. Each cycle needs to pass through the area with higher linear speed of high-pressure torsion, so the grain uniformity is better and the work efficiency is higher, thereby obtaining the process parameters for optimizing the extrusion efficiency.

[0038] The present invention achieves the internal grain refinement and friction of the high-pressure torsion metal by repeated extrusion in forward and reverse directions for multiple cycles, and the extrusion cavity gradient changes gradually during the whole process, thereby effectively avoiding metal cracking, exploring and optimizing the extrusion efficiency, and having the advantages of high-pressure torsion metal crystal refinement, reducing material waste and high forming precision.

[0039] The present invention provides an extrusion device and method for improving the toughness of metal materials, which can significantly refine the grains and improve the mechanical properties of the materials. The high-pressure torsion method is used to apply pressure in the height direction of the deformed body, and torque is applied on the cross section at the same time. Through the combined action of axial compression and tangential shear deformation, plastic deformation of the metal material is achieved. This method can significantly refine the grains and make the microstructure of the material more uniform. The microstructure and mechanical properties of the final parts are mainly affected by process parameters such as aspect ratio, torsion angular velocity, extrusion speed, hydrostatic pressure, friction coefficient and temperature. This method has significant advantages in the production of bulk submicron and nano-fine-grained materials, can greatly improve the performance of traditional materials, and has broad application prospects.

[0040] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An extrusion device for improving the toughness of metal materials, characterized in that: The invention comprises a fixing mechanism (1), an extrusion die (5), a lifting extrusion drive mechanism (6), an upper extrusion assembly and a lower extrusion mechanism, wherein the lifting extrusion drive mechanism (6), the extrusion die (5) and the lower extrusion mechanism are arranged on the fixing mechanism (1) in order from top to bottom, the upper extrusion assembly is connected to the driving end of the lifting extrusion drive mechanism (6), the upper extrusion assembly and the lower extrusion mechanism are respectively slidably matched with the upper and lower ends of the extrusion die (5), an extrusion cavity is formed between the upper extrusion assembly and the lower extrusion mechanism, and the upper extrusion assembly and the lower extrusion mechanism cooperate to realize plastic deformation extrusion of the metal blank in the extrusion cavity.

2. The extrusion device for improving the strength and toughness of metal materials according to claim 1, characterized in that: The upper extrusion assembly comprises a middle extrusion rod (7), a hydraulic column I (8), a hydraulic column II (9), an extrusion ring (22) and a core mold (23), wherein the core mold (23) is a hollow structure, the middle extrusion rod (7) is slidably matched with the inner cavity of the core mold (23), the upper part of the core mold (23) is provided with a lateral waist hole (2301) for feeding and discharging materials, the upper end of the core mold (23) is connected to the fixed part of the lifting extrusion drive mechanism (6), and the lower end of the core mold (23) is inserted into the extrusion die ( 5), an extrusion ring (22) is sleeved on a core mold (23) and is slidably matched with the outer surface of the core mold (23) and the inner cavity of the extrusion mold (5); the top two sides of the extrusion ring (22) are respectively connected to a hydraulic column I (8) and a hydraulic column II (9); the middle extrusion rod (7), the hydraulic column I (8) and the hydraulic column II (9) are respectively connected to the driving end of the lifting extrusion drive mechanism (6); the middle extrusion rod (7) and the extrusion ring (22) are respectively used for forward and reverse alternating reciprocating extrusion.

3. The extrusion device for improving the toughness of metal materials according to claim 2, characterized in that: The lifting and extrusion drive mechanism (6) comprises an extrusion rod hydraulic drive chamber I (17), a middle extrusion rod hydraulic drive chamber (18) and an extrusion rod hydraulic drive chamber II (19); the upper ends of the hydraulic column I (8) and the hydraulic column II (9) are respectively slidably matched with the extrusion rod hydraulic drive chamber I (17) and the extrusion rod hydraulic drive chamber II (19), and the extrusion rod hydraulic drive chamber I (17) and the extrusion rod hydraulic drive chamber II (19) respectively hydraulically servo-control the hydraulic column I (8) and the hydraulic column II (9) to rise and fall synchronously; The upper end of the middle extrusion rod (7) is slidably matched with the middle extrusion rod hydraulic drive chamber (18), and the middle extrusion rod hydraulic drive chamber (18) hydraulically servos the middle extrusion rod (7) to lift and lower.

4. The extrusion device for improving the strength and toughness of metal materials according to claim 2, characterized in that: The lower extrusion mechanism comprises a push rod (2) and a rotating disk (3), wherein the push rod (2) passes through the rotating disk (3), and the push rod (2) and the rotating disk (3) are slidably matched, the upper end of the rotating disk (3) is slidably matched with the inner cavity of the extrusion die (5), and the rotating disk (3) has the freedom of lifting and rotating; the push rod (2) and the middle extrusion rod (7) have the same diameter; The extrusion chamber comprises a middle extrusion chamber (11) located between the middle extrusion rod (7) and the top rod (2), a shear extrusion chamber (12) located between the core die (23) and the rotating disk (3), and a torsional friction stirring extrusion chamber (14) located between the extrusion ring (22) and the rotating disk (3).

5. The extrusion device for improving the strength and toughness of metal materials according to claim 4, characterized in that: The lower extrusion mechanism further comprises a rotary drive mechanism (4), a rotary disk hydraulic cylinder (21) and a push rod lifting drive mechanism, wherein the rotary disk hydraulic cylinder (21) is arranged on the push rod lifting drive mechanism, the lower end of the rotary disk (3) is slidably matched with the inner cavity of the rotary disk hydraulic cylinder (21), and the rotary disk hydraulic cylinder (21) hydraulically servos the rotary disk (3) to lift and lower; the rotary drive mechanism (4) is arranged between the extrusion die (5) and the rotary disk hydraulic cylinder (21), and is connected to the rotary disk (3), and the rotary drive mechanism (4) provides power for the rotary motion of the rotary disk (3); The push rod lifting drive mechanism is arranged on the fixing mechanism (1) and is located below the rotating disk hydraulic cylinder (21); the lower end of the push rod (2) is connected to the push rod lifting drive mechanism; the upper end of the push rod (2) passes through the rotating disk hydraulic cylinder (21) and the rotating disk (3) in sequence; the push rod lifting drive mechanism is used to drive the push rod (2) to rise and fall.

6. The extrusion device for improving the toughness of metal materials according to claim 5, characterized in that: The rotary drive mechanism (4) comprises an upper drive (401), a lower drive (402), a small spur gear (403) and a large spur gear (404), wherein the upper drive (401) and the lower drive (402) are respectively arranged on the extrusion die (5) and the rotary disk hydraulic cylinder (21), and the rotary axes are collinear, the two ends of the small spur gear (403) are respectively connected to the upper drive (401) and the lower drive (402), the large spur gear (404) is fixedly arranged on the outer side of the rotary disk (3), and the large spur gear (404) is meshed with the small spur gear (403), and the axial length of the small spur gear (403) is sufficient to keep the small spur gear (403) and the large spur gear (404) in a meshing state when the rotary disk (3) has a maximum lifting stroke.

7. The extrusion device for improving the strength and toughness of metal materials according to claim 5, characterized in that: The push rod lifting and lowering drive mechanism comprises a push rod hydraulic cylinder (13); the lower end of the push rod (2) passes through the push rod hydraulic cylinder (13); the push rod (2) is slidably matched with the inner cavity of the push rod hydraulic cylinder (13) through a piston (201); the upper and lower sides of the piston (201) respectively form a push rod upper hydraulic chamber (16) and a push rod lower hydraulic chamber (15); the push rod upper hydraulic chamber (16) and the push rod lower hydraulic chamber (15) hydraulically servo-control the lifting and lowering movement of the push rod (2); the lower end of the push rod (2) passes through the bottom of the push rod hydraulic cylinder (13) and is connected to an ultrasonic generator (10); the ultrasonic generator (10) assists the extruded metal in grain refinement through ultrasonic vibration.

8. The extrusion device for improving the strength and toughness of metal materials according to claim 1, characterized in that: The fixing mechanism (1) comprises a base (101), a column (102), a mold connecting plate (103) and a driving connecting plate (104), wherein the driving connecting plate (104) is arranged above the base (101), and the driving connecting plate (104) is connected to the base (101) via two columns (102), and two ends of the mold connecting plate (103) are respectively slidably matched with the two columns (102); The lifting extrusion drive mechanism (6) and the lower extrusion mechanism are respectively arranged on the driving connection plate (104) and the base (101), and the extrusion die (5) is arranged on the die connection plate (103).

9. An extrusion method for improving the toughness of metal materials using the device according to claim 6 or 7, characterized in that: The following steps are involved: Step S1: the extrusion chamber position is initialized, the space of the shear extrusion chamber (12) and the torsional friction stirring extrusion chamber (14) is zero, the top rod (2) is flush with the upper surface of the rotating disk (3), and the middle extrusion rod (7) is in a high position; Step S2: the metal blank is fed through the lateral waist hole (2301) on the upper part of the core mold (23), and the metal blank falls into the middle extrusion cavity (11); Step S3: the hydraulic servo controls the extrusion rod (7) to extrude the metal blank; Step S4: the push rod (2) and the rotating disk (3) are synchronously lowered, so that the metal blank is gradually extruded into the shear extrusion chamber (12) and the torsional friction stirring extrusion chamber (14); Step S5: the extrusion ring (22) rises; at the same time, the push rod (2) and the rotating disk (3) gradually descend, and the rotating disk (3) rotates; the middle extrusion chamber (11) continues to vertically extrude the metal blank, the shear extrusion chamber (12) performs layered shear extrusion on the metal blank, and the torsional friction stirring extrusion chamber (14) performs high-pressure torsional grain refinement friction stirring on the metal blank; Step S6: the extrusion ring (22) continues to rise to the set position, and the middle extrusion rod (7) descends to the set position, and then the step S5 is reversed; Step S7: repeating step S5 and step S6 to a specified number of cycles; Step S8: the space of the shear extrusion chamber (12) and the torsional friction stirring extrusion chamber (14) is zero; the middle extrusion rod (7) is at a high position, and the push rod (2) pushes the nanocrystalline cylindrical finished product to the lateral waist hole (2301) to discharge the material; Step S9: Perform macroscopic mechanical property testing and microscopic material science testing on the nanocrystalline cylindrical finished product.

Images