An ultrahigh pressure pre-tightening discrete extrusion die and a preparation method thereof

Abstract

The application discloses an ultrahigh-pressure pre-tightening discrete extrusion die, which comprises a discrete extrusion channel, upper and lower surfaces of the discrete extrusion channel are respectively provided with upper and lower positioning plates, the upper positioning plate is provided with a pressure head for cooperating with a press to perform extrusion, an outer periphery of the discrete extrusion channel is provided with a supporting ring for dispersing pressure of the discrete extrusion channel, a ring inner passage path size of the supporting ring is matched with a discrete extrusion channel size; an outer side of the supporting ring is provided with a pre-tightening structure for preventing the discrete extrusion channel and the supporting ring from being broken; the discrete extrusion channel comprises straight channel discrete blocks and bent channel discrete blocks which are respectively provided with extrusion channels; the straight channel discrete blocks are spliced from discrete blocks which are obliquely cut along vertical and horizontal channel directions; and the bent channel discrete blocks are spliced from discrete blocks which are cut along a radial direction. The extrusion die improves die bearing capacity, improves aluminum scrap extrusion product quality and efficiency, and reduces manufacturing and use cost of the die.

Description

Technical Field

[0001] This invention relates to an extrusion die and its preparation method, and more particularly to an ultra-high pressure pre-tightened discrete extrusion die and its preparation method. Background Technology

[0002] Solid-state aluminum scrap recycling is a novel aluminum scrap reprocessing technology. Because it avoids the smelting process, it consumes less energy and results in less aluminum loss, making it promising for widespread applications. The solid-state recycling process is based on the equal channel corner extrusion method (ECAP) of large plastic deformation theory. It is an effective method for preparing ultrafine-grained materials. By forcibly compressing aluminum scrap through corners using external force, it not only effectively refines the grain size within the material through the pure shear force at the corners but also results in a high degree of uniformity in the material's internal structure, allowing for continuous production.

[0003] Current solid-state hot extrusion dies are mainly equal channel corner extrusion dies. For example, they consist of three parts: left and right dies and a middle die, which are fixed together by bolts. Heating elements and thermocouples are added. The middle die utilizes the equal channel corner extrusion (ECAP) process. The sample size is 10mm × 10mm × 100mm, which improves extrusion efficiency and provides the die with its own heating function. Die parts are interchangeable. However, the die's pressure-bearing strength is insufficient, resulting in fewer extrusion passes, lower extrusion pressure, more defects in the produced profiles, insufficient strength, high production costs, low production efficiency, and short die lifespan.

[0004] The existing equal-channel corner die has only 2 to 3 extrusion passes. The die material is 20CrMnTi (carburized gear steel) with a yield strength of 960MPa. The maximum axial load F that the ejector pin can withstand is 96kN, and the channel bearing capacity does not exceed 0.5GPa. The screw-connected fixing method is prone to loosening or breakage under the axial tensile stress generated by the extrusion pressure during the extrusion process. Since the quality of aluminum chip extruded profiles is positively correlated with the number of extrusion passes and the extrusion pressure, the low extrusion pressure of this die results in many defects and insufficient strength in the produced profiles, leading to high production costs and low production efficiency. The screw connection method also results in a short die lifespan. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide an ultra-high pressure pre-tightened discrete extrusion die that can improve the pressure during the extrusion process and achieve high production efficiency;

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned ultra-high pressure pre-tightened discrete extrusion die.

[0007] Technical Solution: The present invention provides an ultra-high pressure pre-tightened discrete extrusion die, comprising a discrete extrusion channel, wherein an upper positioning plate and a lower positioning plate are respectively provided on the upper and lower surfaces of the discrete extrusion channel, the upper positioning plate is provided with a pressure head for extrusion with a press, and a support ring is provided on the outer periphery of the discrete extrusion channel for dispersing the pressure of the discrete extrusion channel, wherein the channel path size inside the support ring matches the size of the discrete extrusion channel; a pre-tightening structure is provided on the outer side of the support ring for preventing breakage of the discrete extrusion channel and the support ring;

[0008] The discrete extrusion channel includes a straight channel discrete block and a curved channel discrete block, each having an extrusion channel; the straight channel discrete block is formed by splicing discrete blocks that are obliquely cut along the direction perpendicular to the channel; the curved channel discrete block is formed by splicing discrete blocks that are cut radially.

[0009] The discrete extrusion channel comprises five passes; the first pass includes two sets of straight channel discrete blocks and one set of curved channel discrete blocks; the second, third, and fourth passes each include one set of straight channel discrete blocks and one set of curved channel discrete blocks; the fifth pass includes three sets of straight channel discrete blocks. The length of the first pass is 100mm to 200mm; the length of the second, third, and fourth passes is 120mm; and the length of the fifth pass is 160mm.

[0010] The inner diameter-to-height ratio of the straight channel discrete block is 0.5 to 2; the diameter of the first, second, third, and fourth passes and the first and second groups of discrete blocks in the fifth pass are all 50 mm, the height is 60 mm, and the thickness is 60 mm; the diameter of the last group of discrete blocks in the fifth pass, i.e. the diameter of the outlet discrete block, is 45 mm, the height is 40 mm, and the thickness is 60 mm.

[0011] The discrete extrusion channel is a constant diameter corner channel.

[0012] The straight channel discrete block can be skewed by 0° to 30° along the vertical channel direction to divide it into four discrete blocks of the same size; preferably, the skew is 20°.

[0013] The curved channel discrete block is divided into four equal parts by radial cutting, with the inner and outer angles of the channel being 90°.

[0014] The number of support rings is matched with the number of passes in the discrete extrusion channel.

[0015] The support ring is positioned on the outside of the discrete extrusion channel by a positioning pin.

[0016] The pre-tightening structure is a wire winding layer, which includes an outer cylinder sleeved on the outside of the support ring and wires wound on the outer cylinder.

[0017] Invention Principle: Existing equal-channel corner molds easily experience circumferential tensile stress on the inner wall of the channel that exceeds the material's tensile strength during operation, leading to longitudinal fracture. Therefore, by employing the concept of "pre-fractionation before cracking," the mold is first segmented at the crack-prone areas. This longitudinally disperses the channel, allowing the pressure acting on the smaller area of ​​the inner wall to be transferred to the larger area of ​​the outer support ring's inner wall. Due to the larger area of ​​the support ring's inner wall, the unit pressure generated on it is relatively smaller. The frictional resistance between the segmented blocks reduces the outward transmission of internal pressure. This minimizes the circumferential tensile stress in the channel, reduces the possibility of transverse and longitudinal fractures, and significantly improves the channel's pressure-bearing limit during extrusion.

[0018] Aluminum scrap blocks undergo different extrusion passes within a corner extrusion die. Since the quality of the extruded profile is positively correlated with the number of extrusion passes, multi-corner extrusion dies can significantly improve the extrusion efficiency of the sample, effectively avoiding the cumbersome process of multi-pass extrusion using a single-corner extrusion die. By combining different support ring paths to create detachable support ring combinations that can change the number of extrusion passes, extrusion from 2 to 5 passes within the same die can be achieved. For example... Figure 6 The middle section is a schematic diagram of a 5-stage mold.

[0019] Beneficial Effects: Compared with existing technologies, this invention achieves the following significant effects: Based on the application of equal-channel corner extrusion technology, this invention introduces a segmentation approach, designing a novel ultra-high pressure pre-tightened discrete extrusion die. This not only improves the die's load-bearing capacity, enhances the quality and efficiency of aluminum chip extrusion products, but also reduces the die's manufacturing cost, achieving a die channel load-bearing pressure exceeding 1.2 GPa. This invention also improves the die's service life through wire winding pre-tightening. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the discrete extrusion channel assembly structure and a perspective view of the equal-diameter corner channel of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the straight-channel discrete block of the present invention;

[0023] Figure 4 This is a schematic diagram of the structure of the curved channel discrete block of the present invention;

[0024] Figure 5 This is a structural schematic diagram of the channel support ring assembly;

[0025] Figure 6 This is a cross-sectional view of the support ring assembly path;

[0026] Figure 7 The steel wire winding layer and its cross-sectional view are shown.

[0027] Figure 8 For the engineering process flowchart;

[0028] Figure 9 This is a schematic diagram of the aluminum chip extrusion process;

[0029] Figure 10 The simplified die structure for pre-tightened discrete extrusion dies;

[0030] Figure 11 Simplify the die structure for extrusion dies that do not have splitting and separation capabilities;

[0031] Figure 12 for Figure 10 The finite element geometric model diagram completed in Ansys Workbench 2022R1 after simplifying the model features;

[0032] Figure 13 This is a model diagram after hexahedral mesh generation;

[0033] Figure 14 This is a model after applying constraints and loads to the finite element elements according to the operating conditions. Figure 1 ;

[0034] Figure 15 This is a cross-sectional model of the finite element elements after applying constraints and loads according to the operating conditions. Figure 2 ;

[0035] Figure 16 The model diagram is shown when the normal pressure is 1286 MPa.

[0036] Figure 17 The model diagram is shown when the normal pressure is 1287 MPa.

[0037] Figure 18 for Figure 11 The finite element geometric model diagram completed in Ansys Workbench 2022R1 after simplifying the model features;

[0038] Figure 19 This is a model diagram after hexahedral mesh generation;

[0039] Figure 20 This is a model diagram after applying constraints and loads to the finite element elements according to the requirements of the operating conditions.

[0040] Figure 21 The model diagram is shown when the normal pressure is 449 MPa.

[0041] Figure 22 This is a model diagram when the normal pressure is 500 MPa. Detailed Implementation

[0042] The present invention will now be described in further detail.

[0043] like Figure 1 As shown, the ultra-high pressure pre-tightened discrete extrusion die of the present invention includes a pressure head 1, an upper positioning plate 3 and a lower positioning plate 7, a discrete extrusion channel 4, a support ring 5, and a pre-tightening structure 6. The discrete extrusion channel 4, the support ring 5, and the pre-tightening structure 6 constitute the main extrusion structure. Among them, the discrete extrusion channel 4 is the main pressure-bearing component. The upper and lower positioning plates serve a positioning function, restricting the degree of freedom of the main structure and providing buffering and protection. The press extrudes the aluminum chip block 2 through the pressure head 1, and after being extruded by the die, it forms an aluminum chip block with a finer crystalline structure.

[0044] The present invention uses a cylindrical aluminum chip prefabricated block with a bottom diameter of 50mm and a height of 100mm. Therefore, the inlet of the upper positioning plate 3 is a cone shape with a diameter of 100mm and a bottom diameter of 50mm to prevent the aluminum chip block from getting stuck at the inlet.

[0045] like Figure 2 , 3 As shown in Figure 4, where, Figure 2 The left figure in the figure is a schematic diagram of the discrete extrusion channel assembly structure of the present invention. Figure 2 The right figure is a perspective view of the equal-diameter corner channel; the discrete extrusion channel 4 of the present invention is a discrete extrusion channel assembly, which includes a straight channel discrete block 401 and a curved channel discrete block 402, each with an extrusion channel; the straight channel discrete block 401 is formed by splicing discrete blocks obliquely cut along the vertical and horizontal channel directions; the curved channel discrete block 402 is formed by splicing discrete blocks cut radially. The perspective view of the discrete extrusion channel assembly presents an equal-diameter corner channel. The discrete extrusion channel assembly includes five passes. The first pass consists of two sets of straight channel discrete blocks 401 and one set of curved channel discrete blocks 402, with a length of 180mm. A channel length range of 100mm to 200mm is reasonable, as excessive length will prevent aluminum chips from becoming too thick and stuck at the bend or inlet, while excessive length will affect accuracy and manufacturing difficulty. The second, third, and fourth passes each include one set of straight channel discrete blocks 401 and one set of curved channel discrete blocks 402; the length of the second, third, and fourth passes is 120mm. The fifth pass includes three sets of straight-channel discrete blocks 401.

[0046] Figure 3For the straight-channel discrete block 401, the inner hole height-to-diameter ratio should not be too small or too large; a ratio between 0.5 and 2 is reasonable. To prevent axial fracture due to excessive length, the bore diameter of the first, second, third, and fourth passes, and the first and second groups of discrete blocks in the fifth pass, are all 50mm, the height is 60mm, and the thickness is 60mm. The bore diameter of the last group of discrete blocks in the fifth pass, i.e., the outlet discrete block, is 45mm, the height is 40mm, and the thickness is 60mm. The 45mm bore diameter of the outlet discrete block ensures the uniformity of the aluminum chip shape and prevents the aluminum chip from being larger at one end than the other. The number of discrete blocks determines the degree of discretization of the channel, directly affecting the magnitude of the circumferential tensile stress. A higher number of blocks results in lower circumferential tensile stress, leading to greater pressure loss due to friction during radial pressure transmission. This also reduces the circumferential tensile stress on the inner surface of the high-strength steel support ring, making it less prone to breakage. However, too many blocks can affect the accuracy of channel assembly and increase manufacturing difficulty. Therefore, the number of blocks cannot be increased indefinitely; considering these factors, four blocks are the most suitable. Dividing the channel at a 20° angle perpendicular to the channel direction into four identical discrete blocks results in lower circumferential tensile stress and greater friction compared to radial division. Furthermore, the straight channel discrete block 401 can be divided into four identical discrete blocks at a 0°–30° angle perpendicular to the channel direction. The four discrete blocks are fitted with an interference fit. During extrusion, the aluminum chip block is twisted and rotated by the circumferential stress on the inner wall, thus altering the internal structure of the aluminum chip block.

[0047] Figure 4 The curved channel discrete block 402 is divided into four equal parts by radial cutting to address the manufacturing difficulty. Each discrete block has a height of 60mm, a thickness of 60mm, and a hole diameter of 50mm. The inner and outer angles of the channel are 90°, at which point the shear force at the bend is maximized, thus achieving the optimal equivalent plastic strain effect of the shear force on the aluminum chip block at the corner.

[0048] The support ring 5 of the present invention is as follows Figure 5 , 6As shown, the support ring 5 has a diameter of 400mm and a height of 460mm. The dimensions of the channel path inside the support ring 5 are matched with the dimensions of the discrete extrusion channel 4, and they are rationally allocated into five support rings 5. According to the pressure multiplication principle, the large pressure acting on the inner wall of the split block is dispersed to the inner wall of the outer support ring 5. The contact pressure of the split block on the support ring 5 is further reduced by the effect of frictional resistance. By applying pre-tightening force through interference fit, the volume increase of the channel cavity under the action of inner wall pressure can be significantly reduced, and the maximum pressure that the cavity can withstand can be increased. The hollow parts of different support rings 5 ​​constitute the path of the discrete block channel. The discrete block channel assembly is fitted with the support ring 5 by interference fit to form a combination extrusion die with different paths. The aluminum chip block 2 can be extruded from the die along the different path channels. The positioning pin 8 is used to position the five support rings 5, which are stacked one on top of the other. Figure 2 The upper positioning plate 3 and the lower positioning plate 7 effectively restrict the degrees of freedom of the support ring 5 and the discrete extrusion channel 4, so that the aluminum chip block 2 can only move along the groove in the channel.

[0049] Figure 6 This is a cross-sectional view of the combined path of support ring 5, with each pass rotating 90° clockwise or counterclockwise. The aluminum chip block 2 undergoes different extrusion passes within the corner extrusion die. Since the quality of the extruded aluminum chip profile is positively correlated with the number of extrusion passes, multi-corner extrusion dies can greatly improve the extrusion efficiency of the sample, effectively avoiding the cumbersome process of multi-pass extrusion using a single-corner extrusion die. By combining different paths of support ring 5, a detachable support ring 5 combination with adjustable extrusion passes can be formed, enabling extrusion from 2 passes to 5 passes within the same die. For example... Figure 6 The middle section is a schematic diagram of a 5-stage mold.

[0050] Figure 7 The pre-tightening structure 6 is specifically a wire winding layer, comprising an outer cylinder 601 sleeved around the outside of the support ring 5, and steel wire 602 wound around the outer cylinder. The inner diameter of the outer cylinder is 399mm, slightly smaller than the diameter of the support ring 5 assembly, to facilitate interference fit. The thickness of the cylindrical portion of the outer cylinder should not be too thick, as it is unsuitable for transmitting pre-tightening force; a cylinder thickness of 30mm is set. The more layers of steel wire wound around the outer cylinder, the greater the pre-tightening force generated. The tangential normal stress generated by the pre-tightening force can offset some of the tangential tensile stress in the discrete extrusion channel 4 and the support ring 5, preventing loosening and breakage. This reduces the possibility of breakage of the support ring 5 and the channel, improving their safety factor and service life.

[0051] Figure 8As shown in the process flow diagram, firstly, the aluminum chip block and the mold are preheated to 240℃~260℃. Then, the aluminum chip preform 2 is placed into the inlet of the assembled and fixed ultra-high pressure pre-tightened discrete extrusion mold. The pressure head 1 is placed above the aluminum chip block, and the press is started to move downward. The pressure head 1 extrudes the aluminum chip block into the mold. Then, another aluminum chip block is added and the extrusion continues until the front aluminum chip block is extruded from the outlet, and the extrusion process ends.

[0052] Figure 9 This diagram illustrates the aluminum chip extrusion process. At the inlet of the discrete block channel, the aluminum chips have large, dispersed particles. As they are extruded to the outlet, the particles become smaller and more compact. This demonstrates that after extrusion through the die, the aluminum chip structure becomes finer and can be recycled into aluminum.

[0053] (I) Static Analysis of Ultra-High Pressure Pre-tightened Discrete Extrusion Die

[0054] The pre-treated aluminum shavings are fed into the mold of this invention by extrusion. Inside the mold, they are subjected to extrusion and shear forces in various directions, thereby refining the aluminum shavings into recyclable aluminum material. The discrete extrusion channel 4 is the core component of the mold, designed and made of cemented carbide with a compressive strength as high as 6200 MPa, while the ultimate compressive strength of ordinary high-strength steel is 1320 MPa.

[0055] Pressure was directly applied to the interior of the discrete extrusion channel 4, and the limit value of the bearing pressure strength of the mold channel cavity was analyzed using Ansys simulation.

[0056] (1) Simplified schematic diagram of the pre-tightened discrete extrusion die: The die consists of discrete extrusion channels 4 and support rings 5, as shown below. Figure 10 As shown.

[0057] (2) After simplifying the model features, complete the creation of the finite element geometric model in Ansys Workbench 2022R1, such as... Figure 12 As shown, the components of the simplified model are clearly visible.

[0058] (3) Select the finite element solid element and set the element type to SOILD185. Since the length unit used in geometric modeling is mm, Ansys uses the unit: length: mm, pressure: MPa, density: Ton / M.

[0059] Discrete extrusion channel 4 is made of cemented carbide with the following material properties: Young's modulus: 6E+05MPa; Poisson's ratio: 0.22; support ring 5 is made of high-rigidity steel with the following material properties: Young's modulus: 2E+05MPa; Poisson's ratio: 0.3.

[0060] (4) After dividing the geometric model into regular geometric shapes that can be meshed into hexahedrals, each entity is then meshed into a hexahedral mesh, as shown in the image. Figure 13 As shown.

[0061] (5) Apply constraints and loads to the finite element elements according to the operating conditions: apply normal pressure to the inner surface of the selected channel, and select one side of the mold as a fixed support, such as... Figure 14 , 15 As shown, ABCD represents the normal pressure applied to the inner surface of the dispersion extrusion channel 4, and E represents the fixed surface on the upper surface of the support ring 5.

[0062] (6) Analysis Results and Discussion:

[0063] When the normal pressure is 1286 MPa: For example Figure 16 As shown, the maximum equivalent stress on the simplified mold is 6196.2 MPa, which does not exceed the mold's ultimate strength of 6200 MPa.

[0064] When the normal pressure is 1287 MPa: For example Figure 17 As shown, the maximum equivalent stress on the simplified mold is 6201 MPa, which exceeds the mold's ultimate strength of 6200 MPa.

[0065] This invention, by comparing the changes in maximum bearing capacity under different pressure loads, found that when the channel bearing pressure is 1287 MPa, the maximum stress in the discrete channel of the die reaches 6201 MPa, and the die failure stress is 6200 MPa. Therefore, the maximum bearing capacity of the extrusion die using the discrete extrusion channel 4 is 1287 MPa.

[0066] (II) Static Analysis of Equal Channel Corner Extrusion Die

[0067] The corner extrusion die, i.e., the undivided extrusion channel 4, is mainly composed of support rings 5. The ultimate compressive strength of ordinary high-strength steel is 1320MPa. Pressure is directly applied to the inside of the corner channel. Ansys simulation is used to analyze the ultimate bearing pressure of the die.

[0068] (1) A simplified diagram of the extrusion die without splitting and separation. The die consists of five support rings, and the internal equal-diameter corner channel dimensions are the same as those of this invention. Figure 2 Consistent, such as Figure 11 As shown.

[0069] (2) After simplifying the model features, complete the creation of the finite element geometric model in Ansys Workbench 2022R1: such as Figure 18 As shown, the components of the simplified model are clearly visible.

[0070] (3) Select the finite element solid element and set the element type to SOILD185. Since the length unit used in geometric modeling is mm, Ansys uses the following units: length: mm, pressure: MPa, density: Ton / M. The high-rigidity steel material properties used in the support ring 5 are: Young's modulus: 2E+05MPa; Poisson's ratio: 0.3.

[0071] (4) After dividing the geometric model into regular geometric shapes that can be meshed into hexahedrals, each entity is then meshed into a hexahedral mesh. The mesh result is as follows: Figure 19 As shown.

[0072] (5) Apply constraints and loads to the finite element elements according to the operating conditions: apply normal pressure to the inner surface of the selected channel, and select one side of the mold as a fixed support; for example... Figure 20 As shown, ABC represents the normal pressure applied to the inner surface of the extrusion channel 4, and D represents the fixed surface on the upper surface of the support ring 5.

[0073] (6) Analysis Results and Discussion:

[0074] When the normal pressure is 449 MPa: For example Figure 21 As shown, the maximum equivalent stress on the simplified mold is 1319.6 MPa, which does not exceed the mold's ultimate strength of 1320 MPa.

[0075] When the normal pressure is 450 MPa: For example Figure 22 As shown, the maximum equivalent stress on the simplified mold is 1322.5 MPa, which exceeds the mold's ultimate strength of 1320 MPa.

[0076] This invention, by comparing the changes in maximum bearing capacity under different pressure loads, found that when the channel bearing pressure is 500 MPa, the maximum stress of the die reaches 1322.5 MPa, and the die failure stress is 1320 MPa. Therefore, the maximum bearing capacity of the equal channel angle extrusion die is 500 MPa. A comparison of ANSYS simulations of the simplified pre-tightened discrete extrusion die and the simplified die without separation revealed that the bearing capacity of the simplified pre-tightened discrete extrusion die increased by 787 MPa.

Claims

1. An ultrahigh pressure pre-tightening discrete extrusion die, characterized by, The system includes a discrete extrusion channel (4), with an upper positioning plate (3) and a lower positioning plate (7) respectively on its upper and lower surfaces. The upper positioning plate (3) is equipped with a pressure head (1) for extrusion in conjunction with a press. The outer periphery of the discrete extrusion channel (4) is equipped with a support ring (5) for dispersing the pressure of the discrete extrusion channel (4). The inner channel path size of the support ring (5) matches the size of the discrete extrusion channel (4). The outer side of the support ring (5) is equipped with a pre-tightening structure to prevent the discrete extrusion channel (4) and the support ring (5) from breaking. (6); The discrete extrusion channel (4) includes a straight channel discrete block (401) and a curved channel discrete block (402) respectively provided with extrusion channels; the straight channel discrete block (401) is composed of discrete blocks that are obliquely cut along the vertical or horizontal channel direction and spliced ​​together; the curved channel discrete block (402) is composed of discrete blocks that are cut along the radial direction and spliced ​​together; the straight channel discrete block (401) is divided into four discrete blocks of the same size at an oblique angle of 0° to 30° along the vertical or horizontal channel direction; the curved channel discrete block (402) divides the curved channel into four equal parts by radial cutting; The discrete extrusion channel (4) includes five passes; the first pass includes two sets of straight channel discrete blocks (401) and one set of curved channel discrete blocks (402); the second, third and fourth passes each include one set of straight channel discrete blocks (401) and one set of curved channel discrete blocks (402); the fifth pass includes three sets of straight channel discrete blocks (401). The inner diameter ratio of the straight channel discrete block (401) is 0.5 to 2; the discrete extrusion channel (4) is an equal diameter corner channel.

2. The ultrahigh-pressure pre-tension discrete extrusion die according to claim 1, characterized in that, The length of the first pass is 100mm to 200mm.

3. The ultrahigh-pressure pre-tension discrete extrusion die of claim 1, wherein, The number of support rings (5) matches the number of passes in the discrete extrusion channel (4).

4. The ultrahigh-pressure pre-tension discrete extrusion die of claim 1, wherein, The support ring (5) is positioned on the outside of the discrete extrusion channel (4) by a positioning pin.

5. The ultra-high pressure pre-tightened discrete extrusion die according to claim 1, characterized in that, The pre-tightening structure (6) is a wire winding layer, which includes an outer cylinder (601) sleeved on the outside of the support ring (5) and a wire (602) wound on the outer cylinder (601).

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