Device and method for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion

Abstract

The present invention belongs to the field of magnesium alloy processing, and in particular, relates to a device and method for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion, which can cause continuous and severe torsional deformation and shear deformation of magnesium alloy tube blanks during processing, thereby achieving great grain refinement, improving the room temperature mechanical properties of magnesium alloy tubes, and expanding the application range of magnesium alloys; the technical solution includes: an external mold frame and a torsional shearing die. Among them, the external mold frame at least includes a power transmission rod and a heating sleeve, the power transmission rod passes through the heating sleeve, and the power transmission rod has a tendency to reciprocate along its axial direction. The torsional shearing die is arranged on the power transmission rod in the heating sleeve, and the torsional shearing die is configured to operate under the drive of the power transmission rod.

Description

Technical Field

[0001] The invention belongs to the field of magnesium alloy processing, and in particular relates to a device and a method for preparing fine-grained magnesium alloy pipes by differential-angle reciprocating torsional extrusion. Background Art

[0002] Magnesium alloy is the lightest metal structural material in practical application. Compared with traditional metal structural materials, magnesium alloy has many advantages, such as high specific strength and specific stiffness, good damping performance, strong electromagnetic shielding and radiation resistance, good thermal conductivity, easy cutting and recycling, etc. Magnesium alloy has been widely used in aerospace, transportation, weapons and equipment, information industry and other fields.

[0003] However, due to the unique close-packed hexagonal structure of magnesium alloys, only two independent slip systems are activated at room temperature, which cannot meet the requirements of five independent slip systems required for plastic deformation. Therefore, magnesium alloys exhibit poor room temperature mechanical properties and forming properties. At the same time, the unique structural characteristics of magnesium alloys often lead to the formation of deformation textures during processing. The appearance of deformation textures causes anisotropy and tension-compression asymmetry in magnesium alloys, which seriously limits their application scope and industrial promotion. Grain refinement can significantly improve the mechanical properties of magnesium alloy materials. Severe plastic deformation technology has been proven to be able to effectively refine magnesium alloy grains, such as high pressure torsion (HPT), multidirectional forging (MDF), equal channel angular extrusion (ECAP), and rotary extrusion (TE). However, these severe plastic deformation methods have many technical problems and shortcomings, which greatly limit the realization of large-scale continuous production.

[0004] Therefore, there is an urgent need for an effective and greatly refined device and method for magnesium alloy tube grains to expand the production efficiency and application range of magnesium alloy tubes. Summary of the invention

[0005] In order to overcome the defects in the above-mentioned related technologies, the present invention provides a device and method for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion, which can cause continuous and severe torsional deformation and shear deformation of the magnesium alloy tube blank during the processing, thereby greatly achieving grain refinement, improving the room temperature mechanical properties of the magnesium alloy tube, and expanding the application range of magnesium alloys.

[0006] In order to achieve the above technical objectives, on the one hand, the present invention provides a device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion. The device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion comprises: an external mold frame and a torsional shearing die. Among them, the external mold frame at least includes a power transmission rod and a heating sleeve, the power transmission rod passes through the heating sleeve, and the power transmission rod has a tendency to reciprocate along its axial direction. The torsional shearing die is arranged on the power transmission rod in the heating sleeve, and the torsional shearing die is configured to run under the drive of the power transmission rod.

[0007] Wherein, the torsion shearing mold includes: a first torsion mold, a second torsion mold and a plurality of shearing molds. Wherein, the first torsion mold is an annular structure, the first torsion mold is axially fixed relative to the power transmission rod, and the first torsion mold is configured to rotate under the drive of the power transmission rod. The second torsion mold is an annular structure, the second torsion mold is axially fixed relative to the power transmission rod, and the second torsion mold is configured to rotate under the drive of the power transmission rod, and the second torsion mold rotates in the opposite direction to the first torsion mold. A plurality of shearing molds are sequentially arranged on the power transmission rod between the first torsion mold and the second torsion mold.

[0008] The multiple shearing dies include: a shearing module and an extrusion module. The shearing module includes an inner torsion member and an outer torsion member, the inner torsion member is an annular structure, the inner torsion member is axially fixed relative to the power transmission rod, and the inner torsion member is configured to rotate under the drive of the power transmission rod, and the rotation angular velocity of the inner torsion member is less than the rotation angular velocity of the first torsion die, the outer ring of the inner torsion member is a polygonal structure, the outer torsion member is an annular structure, the inner ring of the outer torsion member is a polygonal structure consistent with the shape of the outer ring of the inner torsion member, and a first gap is provided between the inner ring of the outer torsion member and the outer ring of the inner torsion member.

[0009] At least one side of the shearing module is provided with at least one extrusion module, and the extrusion module includes an inner extrusion part and an outer extrusion part, the inner extrusion part is an annular structure, a protrusion is provided on part of the outer wall of the inner extrusion part, and a groove is provided on another part of the outer wall of the inner extrusion part, the protrusion is tangent to the connection position of the groove, the inner extrusion part has a tendency to reciprocate axially with the power transmission rod, and the inner extrusion part also has a tendency to rotate with the shearing module; the outer extrusion part is an annular structure, the inner side wall of the outer extrusion part is adapted to the shape of the outer side wall of the inner extrusion part, the outer extrusion part is sleeved on the inner extrusion part, and a second gap is provided between the inner side wall of the outer extrusion part and the outer side wall of the inner extrusion part, and the central axis of the outer extrusion part is parallel to and not colinear with the central axis of the inner extrusion part, and the outer extrusion part is fixed relative to the inner extrusion part.

[0010] Preferably, in two adjacent extrusion modules, the angle between the orthographic projection of the shortest connecting line between the central axis of the outer extrusion of one extrusion module and the central axis of the corresponding inner extrusion on the first plane and the orthographic projection of the shortest connecting line between the central axis of the outer extrusion of the other extrusion module and the central axis of the corresponding inner extrusion on the first plane is 60° to 120°. The first plane is perpendicular to the central axis of the power transmission rod.

[0011] Preferably, a protrusion is provided on half of the outer wall of the inner extrusion, and the outer side surface of the protrusion intersects with the cross section passing through the central axis of the inner extrusion to form a first intersection line, and the curvature of the first intersection line increases from one end of the protrusion to the middle of the protrusion, and decreases to zero from the middle of the protrusion to the other end of the protrusion. A groove is provided on the other half of the outer wall of the inner extrusion, and the outer side surface of the groove intersects with the cross section passing through the central axis of the inner extrusion to form a second intersection line, and the curvature of the second intersection line increases from one end of the groove to the middle of the groove, and decreases to zero from the middle of the groove to the other end of the groove.

[0012] Preferably, the power transmission rod comprises a first threaded shaft section, the first threaded shaft section is provided with an external thread, the first torsion mold is provided with an internal thread meshing with the external thread of the first threaded shaft section, the first torsion mold is sleeved on the first threaded shaft section, and the first threaded shaft section drives the first torsion mold to rotate when the first threaded shaft section reciprocates along the axial direction of the power transmission rod. The power transmission rod comprises a second threaded shaft section, the second threaded shaft section is provided with an external thread, and the external thread of the second threaded shaft section is in the opposite direction to the external thread of the first threaded shaft section, the second torsion mold is provided with an internal thread meshing with the external thread of the second threaded shaft section, the second torsion mold is sleeved on the second threaded shaft section, and the second threaded shaft section drives the second torsion mold to rotate when the second threaded shaft section reciprocates along the axial direction of the power transmission rod.

[0013] Preferably, the power transmission rod includes a plurality of third threaded shaft segments, the thread direction of the third threaded shaft segment close to the first threaded shaft segment among the plurality of third threaded shaft segments is the same as the thread direction of the first threaded shaft segment, and the pitch of the third threaded shaft segment close to the first threaded shaft segment is greater than the pitch of the first threaded shaft segment, and the thread direction of the third threaded shaft segment close to the second threaded shaft segment among the plurality of third threaded shaft segments is the same as the thread direction of the second threaded shaft segment, and the pitch of the third threaded shaft segment close to the first threaded shaft segment is greater than the pitch of the second threaded shaft segment.

[0014] The inner torsion member is provided with an inner thread meshing with the outer thread of the third threaded shaft segment. The inner torsion member is sleeved on the third threaded shaft segment. When the third threaded shaft segment reciprocates along the axial direction of the power transmission rod, the inner torsion member is driven to rotate.

[0015] Preferably, a plurality of rotating rods are arranged on the side surfaces of the inner torsion member and / or the outer torsion member, and the plurality of rotating rods are parallel to the central axis of the power transmission rod. A plurality of through holes are arranged on the inner extrusion member and the outer extrusion member, and a corresponding rotating rod is arranged in each through hole. The rotating rods are configured to drive the inner extrusion member and the outer extrusion member to rotate synchronously with the inner torsion member and / or the outer torsion member.

[0016] Preferably, the torsion shearing die further comprises a plurality of fixed disks, which are annular parts and are coaxially fixed to the power transmission rod. The inner ring of the inner torsion member is provided with an annular groove adapted to the edge of the fixed disk, each inner torsion member is clamped on one of the fixed disks, and the fixed disk is configured to drive the inner torsion member to reciprocate along the axial direction of the power transmission rod.

[0017] Preferably, the power transmission rod comprises a first transmission rod and a second transmission rod. One end of the first transmission rod located in the heating sleeve is connected to one end of the second transmission rod located in the heating sleeve, the central axis of the first transmission rod is colinear with the central axis of the second transmission rod, and the first transmission rod has a tendency to rotate around the central axis of the second transmission rod.

[0018] On the other hand, some embodiments of the present invention further provide a method for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion, which is applicable to the device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion described in any of the above embodiments.

[0019] The method for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsion extrusion comprises: preheating the magnesium alloy tubes, setting the heating temperature of the vacuum atmosphere heating furnace to 300-500°C, and after the temperature of the heating furnace reaches the set temperature, placing the magnesium alloy tubes in the heating furnace for 2-4 hours. The magnesium alloy tubes are subjected to torsion extrusion deformation, and the tube wall of the magnesium alloy tubes is subjected to reciprocating torsion deformation around its central axis at a temperature of 300-500°C, and the tube wall of the magnesium alloy tubes is subjected to shear deformation at the same time, and the tube wall of the magnesium alloy tubes is subjected to multiple extrusion deformations.

[0020] Preferably, before preheating the magnesium alloy tube, the magnesium alloy tube needs to be pretreated, and the method for pretreating the magnesium alloy tube includes: processing the magnesium alloy tube to an outer diameter of D and a tube wall thickness of t. Removing oil stains from the surface of the magnesium alloy tube. Grinding the surface of the magnesium alloy tube, the magnesium alloy tube is less than 0.1a. Using a cleaning liquid to ultrasonically clean the magnesium alloy tube for 30 to 60 minutes, then cleaning the magnesium alloy tube with anhydrous ethanol, and drying the magnesium alloy tube. Applying a graphite oil solution to the surface of the magnesium alloy tube for subsequent use.

[0021] The beneficial effects of the present invention are:

[0022] The present invention adopts a first torsion die and a second torsion die to perform torsion deformation on the magnesium alloy tube, so that the grain refinement effect of the magnesium alloy tube is significant, and the obtained high-performance fine-grained magnesium alloy tube has uniform structure and greatly improved toughness. At the same time, the shearing module can realize shear deformation of the magnesium alloy tube, and the extrusion module can realize extrusion deformation of the tube wall of the magnesium alloy tube, so that the magnesium alloy tube undergoes torsion deformation and shear deformation at the same time, further making the grains more refined, the structure more uniform, and improving the comprehensive performance of the magnesium alloy tube. The structure of the whole device is simple and easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a structural diagram of the present invention;

[0025] Figure 2 It is a structural diagram of the inner torsion member and the outer torsion member of the present invention;

[0026] Figure 3 It is a structural diagram of the inner extrusion part and the outer extrusion part of the present invention;

[0027] Figure 4 It is a state diagram of the extrusion module of the present invention at different rotation periods;

[0028] Figure 5 This is a state diagram of the magnesium alloy tube of the present invention being deformed by external force;

[0029] Figure 6 A step diagram of preparing a fine-grained magnesium alloy tube by differential-angle reciprocating torsional extrusion of the present invention;

[0030] Figure 7 Another step diagram of preparing fine-grained magnesium alloy tube by differential-angle reciprocating torsional extrusion of the present invention;

[0031] Figure 8 This is a diagram of the steps of pretreating the magnesium alloy tube according to the present invention. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0034] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0035] Some embodiments of the present invention provide a device for preparing fine-grained magnesium alloy tube 5 by differential angle reciprocating torsion extrusion. Figures 1 to 5 As shown, the device for preparing fine-grained magnesium alloy tube 5 by differential angle reciprocating torsion extrusion comprises: an external die frame and a torsion shearing die. The external die frame comprises at least a power transmission rod 11 and a heating sleeve 12, wherein the power transmission rod 11 penetrates the heating sleeve 12 and has a tendency to reciprocate along its axial direction. The torsion shearing die is arranged on the power transmission rod 11 in the heating sleeve 12, and the torsion shearing die is configured to operate under the drive of the power transmission rod 11.

[0036] The torsion shearing mold includes: a first torsion mold 21, a second torsion mold 22 and a plurality of shearing molds 23. The first torsion mold 21 is an annular structure, the first torsion mold 21 is axially fixed relative to the power transmission rod 11, and the first torsion mold 21 is configured to rotate under the drive of the power transmission rod 11. The second torsion mold 22 is an annular structure, the second torsion mold 22 is axially fixed relative to the power transmission rod 11, and the second torsion mold 22 is configured to rotate under the drive of the power transmission rod 11, and the second torsion mold 22 rotates in the opposite direction to the first torsion mold 21. A plurality of shearing molds 23 are sequentially arranged on the power transmission rod 11 between the first torsion mold 21 and the second torsion mold 22.

[0037] The multiple shearing dies 23 include: a shearing module 231 and an extrusion module 232. The shearing module 231 includes an inner torsion member 2311 and an outer torsion member 2312, wherein the inner torsion member 2311 is an annular structure, the inner torsion member 2311 is axially fixed relative to the power transmission rod 11, and the inner torsion member 2311 is configured to rotate under the drive of the power transmission rod 11, and the rotation angular velocity of the inner torsion member 2311 is less than the rotation angular velocity of the first torsion die 21, the outer ring of the inner torsion member 2311 is a polygonal structure, the outer torsion member 2312 is an annular structure, the inner ring of the outer torsion member 2312 is a polygonal structure consistent with the outer ring of the inner torsion member 2311, and a first gap H is provided between the inner ring of the outer torsion member 2312 and the outer ring of the inner torsion member 2311.

[0038] At least one side of the shearing module 231 is provided with at least one extrusion module 232, and the extrusion module 232 includes an inner extrusion piece 2321 and an outer extrusion piece 2322. The inner extrusion piece 2321 is an annular structure, and a protrusion is provided on part of the outer wall of the inner extrusion piece 2321, and a groove is provided on another part of the outer wall of the inner extrusion piece 2321. The protrusion is tangent to the connection position of the groove, and the inner extrusion piece 2321 has a tendency to reciprocate axially with the power transmission rod 11, and the inner extrusion piece 2321 also has a tendency to rotate with the shearing module 231; The outer extrusion piece 2322 is an annular structure, and the inner wall of the outer extrusion piece 2322 is adapted to the shape of the outer wall of the inner extrusion piece 2321. The outer extrusion piece 2322 is sleeved on the inner extrusion piece 2321, and a second gap G is provided between the inner wall of the outer extrusion piece 2322 and the outer wall of the inner extrusion piece 2321. The outer extrusion piece 2322 is sleeved on the inner extrusion piece 2321, and the central axis of the outer extrusion piece 2322 is parallel to and not colinear with the central axis of the inner extrusion piece 2321, and the outer extrusion piece 2322 is fixed relative to the inner extrusion piece 2321.

[0039] In some examples, the external mold frame for preparing fine-grained magnesium alloy tube 5 by differential angle reciprocating torsion extrusion also includes a first fixed support 13 and a second fixed support 14, wherein the first fixed support 13 and the second fixed support 14 are arranged opposite to each other, and the heating sleeve 12 is horizontally fixed (the central axis of the heating sleeve 12 is horizontal) between the first fixed support 13 and the second fixed support 14. It can be understood that the heating sleeve 12, as a heating device for the working area of ​​the torsion shearing die, can be a tubular structure with two ends open, and the heating sleeve 12 can include a plurality of heating resistance wires. A cavity filling mold 24 can also be arranged inside the heating sleeve 12. The cavity filling mold 24 can be a cylindrical structure, and a cavity for placing the torsion shearing die is arranged in the middle. Through holes are arranged at both ends of the cavity filling mold 24, so that the two ends of the power transmission rod 11 can pass through the through holes and then be connected to the torsion shearing die. The cavity filling mold 24 can be made of hot working die steel 4Cr5MoSiV1, and the surface roughness can be Ra0.16.

[0040] The power transmission rod 11 may be a horizontally arranged straight rod. Driven by external power, the power transmission rod 11 may reciprocate in the horizontal direction. Therefore, the first fixed bracket 13 and the second fixed bracket 14 may be provided with through holes or linear bearings for supporting the power transmission rod 11 .

[0041] The first torsion die 21 and the second torsion die 22 are both coaxially arranged on the power transmission rod 11. A plurality of rectangular inserts are arranged on the side of the first torsion die 21 opposite to the second torsion die 22, and on the side of the second torsion die 22 opposite to the first torsion die 21, for example, four rectangular inserts. Both ends of the magnesium alloy tube 5 are provided with grooves corresponding to the plurality of rectangular inserts. During operation, the plurality of rectangular inserts on the first torsion die 21 are correspondingly engaged in the plurality of grooves at one end of the magnesium alloy tube 5. Similarly, the plurality of rectangular inserts on the second torsion die 22 are correspondingly engaged in the plurality of grooves at the other end of the magnesium alloy tube 5, so as to fix the magnesium alloy tube 5.

[0042] A plurality of shearing dies 23 are arranged between the first twisting die 21 and the second twisting die 22 . For example, two shearing dies 23 may be arranged. Each shearing die 23 includes a shearing module 231 and an extrusion module 232 .

[0043] Among them, the shear module 231 includes an inner torsion member 2311 and an outer torsion member 2312. The inner torsion member 2311 can be an annular structure. The inner torsion member 2311 is coaxially arranged on the power transmission rod 11. The outer ring of the inner torsion member 2311 is a polygonal structure, for example, it can be a regular hexagonal structure. Correspondingly, the outer ring of the outer torsion member 2312 is a regular hexagonal structure. A first gap H is arranged between the inner torsion member 2311 and the outer torsion member 2312. The width of the first gap H is equal everywhere. The magnesium alloy tube 5 passes through the first gap H. In this way, when the inner torsion member 2311 rotates, the magnesium alloy tube 5 and the outer torsion member 2312 can be driven to rotate at the same time. However, the magnesium alloy tube 5 has a rotation speed difference relative to the inner torsion member 2311 and the outer torsion member 2312, thereby realizing shear deformation of the magnesium alloy tube 5.

[0044] The extrusion module 232 includes an inner extrusion piece 2321 and an outer extrusion piece 2322, and a second gap G is arranged between the inner extrusion piece 2321 and the outer extrusion piece 2322. The second gap G is composed of corresponding protrusions and grooves, and the opposite sides of the second gap G are smooth surfaces. It can be understood that the magnesium alloy tube 5 arranged in the second gap G can form relative movement with the inner extrusion piece 2321 and the outer extrusion piece 2322, that is, the inner extrusion piece 2321 and the outer extrusion piece 2322 can yield to the tube wall deformation of the magnesium alloy tube 5, but cannot drive the magnesium alloy tube 5 to follow the operation, or can only drive the magnesium alloy tube 5 to follow the operation slightly, so as to realize the extrusion deformation of the magnesium alloy tube 5.

[0045] When the power transmission rod 11 reciprocates in the horizontal direction, it drives the first torsion mold 21 and the second torsion mold 22 to rotate, and the first torsion mold 21 and the second torsion mold 22 rotate in opposite ways, so as to achieve torsion deformation of the magnesium alloy tube 5. At the same time, the power transmission rod 11 can also drive the inner torsion piece 2311 to rotate. The rotation direction of the inner torsion piece 2311 close to the first torsion mold 21 is the same as the rotation direction of the first torsion mold 21, but the rotation speed of the inner torsion piece 2311 is lower than the rotation speed of the first torsion mold 21. Similarly, the rotation direction of the inner torsion piece 2311 close to the second torsion mold 22 is the same as the rotation direction of the second torsion mold 22, but the rotation speed of the inner torsion piece 2311 is lower than the rotation speed of the second torsion mold 22, so that the overall torsion of the tube wall of the magnesium alloy tube 5 can be achieved, and the shearing module 231 simultaneously achieves shearing and extrusion deformation of the magnesium alloy tube 5, so that the grain of the magnesium alloy tube 5 is refined.

[0046] In some embodiments, in two adjacent extrusion modules 232, the angle between the orthographic projection of the shortest connecting line between the central axis of the outer extrusion 2322 of one extrusion module 232 and the central axis of the corresponding inner extrusion 2321 on the first plane and the orthographic projection of the shortest connecting line between the central axis of the outer extrusion 2322 of the other extrusion module 232 and the central axis of the corresponding inner extrusion 2321 on the first plane is 60° to 120°, for example, 60°, 90° or 120°. The first plane is perpendicular to the central axis of the power transmission rod 11.

[0047] In some examples, one or two extrusion modules 232 may be provided on one side of the shearing module 231, or one or two extrusion modules 232 may be provided on both sides of the shearing module 231. Adjacent extrusion modules 232 may be located on the same side of the shearing module 231, on both sides of the shearing module 231, or between two shearing modules 231. Adjacent extrusion modules 232 may have an angular deviation, for example, a difference of 90°, so as to facilitate the surplus and shortage of the blank volume of the magnesium alloy tube 5 in the second gap G to complement each other.

[0048] In some embodiments, a protrusion is provided on half of the outer wall of the inner extrusion member 2321, and the outer side surface of the protrusion intersects with the cross section passing through the central axis of the inner extrusion member 2321 to form a first intersection line, and the curvature of the first intersection line increases from one end of the protrusion to the middle of the protrusion, and decreases to zero from the middle of the protrusion to the other end of the protrusion. A groove is provided on the other half of the outer wall of the inner extrusion member 2321, and the outer side surface of the groove intersects with the cross section passing through the central axis of the inner extrusion member 2321 to form a second intersection line, and the curvature of the second intersection line increases from one end of the groove to the middle of the groove, and decreases to zero from the middle of the groove to the other end of the groove.

[0049] It can be understood that the inner side surface of the outer extrusion part 2322 corresponds to the outer side surface of the inner extrusion part 2321, and a second gap G with equal width is formed between the inner side surface of the outer extrusion part 2322 and the outer side surface of the inner extrusion part 2321. That is to say, the inner side wall of the outer extrusion part 2322 corresponding to the outer side wall of the protrusion of the inner extrusion part 2321 is a groove, and the inner side wall of the outer extrusion part 2322 corresponding to the outer side wall of the groove of the inner extrusion part 2321 is a protrusion.

[0050] In some embodiments, the power transmission rod 11 includes a first threaded shaft segment 111, on which an external thread is provided, and the first torsion mold 21 is provided with an internal thread meshing with the external thread of the first threaded shaft segment 111, and the first torsion mold 21 is sleeved on the first threaded shaft segment 111, and the first threaded shaft segment 111 drives the first torsion mold 21 to rotate when the first threaded shaft segment 111 reciprocates along the axial direction of the power transmission rod 11. The power transmission rod 11 includes a second threaded shaft segment 112, on which an external thread is provided, and the external thread of the second threaded shaft segment 112 is opposite in direction to the external thread of the first threaded shaft segment 111, and the second torsion mold 22 is provided with an internal thread meshing with the external thread of the second threaded shaft segment 112, and the second torsion mold 22 is sleeved on the second threaded shaft segment 112, and the second threaded shaft segment 112 drives the second torsion mold 22 to rotate when the second threaded shaft segment 112 reciprocates along the axial direction of the power transmission rod 11.

[0051] It can be known to those skilled in the art that in order to enable the first twisting mold 21 and the second twisting mold 22 to rotate and keep the displacement in the horizontal direction at zero, a bearing can be arranged between the first twisting mold 21 and the cavity filling mold 24. Specifically, the outer side surface of the first twisting mold 21 is fixed to the inner ring of the bearing, and the outer ring of the bearing is fixed to the cavity filling mold 24. Similarly, a bearing can be arranged between the second twisting mold 22 and the cavity filling mold 24. The thread profiles on the first threaded shaft segment 111 and the second threaded shaft segment 112 can be trapezoidal threads, and the thread angles should be large enough, and the friction between the first twisting mold 21 and the second twisting mold 22 and the corresponding first threaded shaft segment 111 and the second threaded shaft segment 112 is small, so that the movement of the power transmission rod 11 can drive the first twisting mold 21 and the second twisting mold to rotate.

[0052] In some embodiments, the power transmission rod 11 includes a plurality of third threaded shaft segments 113, wherein the thread direction of the third threaded shaft segment 113 close to the first threaded shaft segment 111 among the plurality of third threaded shaft segments 113 is the same as the thread direction of the first threaded shaft segment 111, and the pitch of the third threaded shaft segment 113 close to the first threaded shaft segment 111 is greater than the pitch of the first threaded shaft segment 111, and the thread direction of the third threaded shaft segment 113 close to the second threaded shaft segment 112 among the plurality of third threaded shaft segments 113 is the same as the thread direction of the second threaded shaft segment 112, and the pitch of the third threaded shaft segment 113 close to the first threaded shaft segment 111 is greater than the pitch of the second threaded shaft segment 112.

[0053] The inner torsion member 2311 is provided with an inner thread meshing with the outer thread of the third threaded shaft segment 113 , and the inner torsion member 2311 is sleeved on the third threaded shaft segment 113 , and when the third threaded shaft segment 113 reciprocates along the axial direction of the power transmission rod 11 , the inner torsion member 2311 is driven to rotate.

[0054] Similarly, the thread profile of the third threaded shaft segment 113 can be a trapezoidal thread, and the thread angle should be large enough, and the friction between the inner torsion member 2311 and the third threaded shaft segment 113 is small, so that the movement of the power transmission rod 11 can drive the inner torsion member 2311 to rotate.

[0055] In some embodiments, a plurality of rotating rods 26 are arranged on the side of the inner torsion member 2311 and / or the outer torsion member 2312, and the plurality of rotating rods 26 are parallel to the central axis of the power transmission rod 11. A plurality of through holes are arranged on the inner extrusion member 2321 and the outer extrusion member 2322, and a corresponding rotating rod 26 is arranged in each through hole. The rotating rod 26 is configured to drive the inner extrusion member 2321 and the outer extrusion member 2322 to rotate synchronously with the inner torsion member 2311 and / or the outer torsion member 2312.

[0056] In some embodiments, the torsional shearing mold also includes a locking bracket 25, which can be arranged between two adjacent shearing molds 23, and the locking bracket 25 is mounted on the power transmission rod 11. The locking bracket 25 can rotate around the power transmission rod 11, and the locking bracket 25 is fixedly connected to the rotating rod 26 of the two adjacent shearing molds 23 close to the locking bracket 25.

[0057] The locking bracket 25 includes a left locking end 251 and a right locking end 252, the left locking end 251 includes a left locking tube 253 arranged in the middle, and the right locking end 252 includes a right locking tube 254 arranged in the middle, wherein the diameter of the left locking tube 253 can be larger than the diameter of the right locking tube 254, the right locking tube 254 can be mounted on the power transmission rod 11 and has a tendency to rotate relative to the power transmission rod 11, the right locking tube 254 is fixed to the inner ring of the bearing, and the left locking tube 253 is fixed to the outer ring of the bearing, so that the left locking end 251 can rotate relative to the right locking end 252.

[0058] The rotating rod 26 of the shearing die 23 close to the first twisting die 21 extends to the side of the first twisting die 21, that is, the rotating rod 26 close to the first twisting die 21 abuts against the side of the first twisting die 21 and can rotate relative to the first twisting die 21; the rotating rod 26 close to the second twisting die 22 abuts against the side of the second twisting die 22 and can rotate relative to the second twisting die 22. In order to facilitate the rotating rod 26 to run relative to the first twisting die 21 and the second twisting die 22, universal rollers can be provided on the ends of the rotating rod 26 close to the first twisting die 21 and the second twisting die 22.

[0059] In some embodiments, the torsion shearing die further includes a plurality of fixed disks 2323, which are annular members coaxially fixed to the power transmission rod 11. The inner ring of the inner torsion member 2311 is provided with an annular groove adapted to the edge of the fixed disk 2323, each inner torsion member 2311 is clamped on a fixed disk 2323, and the fixed disk 2323 is configured to drive the inner torsion member 2311 to reciprocate along the axial direction of the power transmission rod 11.

[0060] Exemplarily, a step groove is provided on the inner circle of the inner torsion member 2311 to one side surface thereof. During specific installation, the fixed disk 2323 can be set in the step groove, and a clamping plate is provided on the outer side of the fixed disk 2323 facing the step groove. The clamping plate can be two semi-annular structures, which are fixed to the inner torsion member 2311 by screws, so that the fixed disk 2323 is set in the annular clamping groove of the inner torsion member 2311. It can be understood that the annular clamping groove is a part of the step groove.

[0061] In some embodiments, the power transmission rod 11 includes a first transmission rod 114 and a second transmission rod 115. One end of the first transmission rod 114 located in the heating sleeve 12 is connected to one end of the second transmission rod 115 located in the heating sleeve 12, the central axis of the first transmission rod 114 is colinear with the central axis of the second transmission rod 115, and the first transmission rod 114 has a tendency to rotate around the central axis of the second transmission rod 115.

[0062] Exemplarily, the first transmission rod 114 and the second transmission rod 115 may be connected via bearings, for example, a bearing is disposed at each end of a sleeve, one of the two bearings is connected to the first transmission rod 114, and the other bearing is connected to the second transmission rod 115. Alternatively, a conical groove is disposed at one end of the first transmission rod 114 located in the heating sleeve 12, and a conical structure adapted to the conical groove is disposed at one end of the second transmission rod 115 located in the heating sleeve 12, and the conical structure may be snapped into the conical groove.

[0063] The torsion direction of the magnesium alloy tube 5 is opposite, forming two reaction forces in opposite directions on the power transmission rod 11, which may cause stress concentration in the middle of the power transmission rod 11. The first transmission rod 114 and the second transmission rod 115 can avoid the power transmission rod 11 from breaking due to stress concentration.

[0064] In some embodiments, the device for preparing fine-grained magnesium alloy tube 5 by differential-angle reciprocating torsional extrusion may also include a left telescopic member 3 and a right telescopic member 4, wherein the left telescopic member 3 is connected to the first transmission rod 114, and the right telescopic member 4 is connected to the second transmission rod 115, and the left telescopic member 3 and the right telescopic member 4 may be hydraulic cylinders or electric screws.

[0065] In some embodiments, a left connecting member may be provided between the left telescopic member 3 and the first transmission rod 114, and a right connecting member may be provided between the right telescopic member 4 and the second transmission rod 115. The left connecting member and the right connecting member may be couplings.

[0066] In some embodiments, the first threaded shaft segment 111, the second threaded shaft segment 112 and the third threaded shaft segment 113 can all be tubular structures and can be mounted on the power transmission rod 11. To facilitate the control of locking and separation of the first threaded shaft segment 111, the second threaded shaft segment 112 and the third threaded shaft segment 113 with the power transmission rod 11, a radial clutch 116 can be provided between the first threaded shaft segment 111 and the power transmission rod 11, a radial clutch 116 can be provided between the second threaded shaft segment 112 and the power transmission rod 11, and a radial clutch 116 can be provided between the third threaded shaft segment 113 and the power transmission rod 11. The radial clutch 116 can be controlled by hydraulic oil.

[0067] In some embodiments, the device for preparing fine-grained magnesium alloy tube 5 by differential-angle reciprocating torsional extrusion further includes a control device, which is used to control the operation of the left telescopic member 3 , the right telescopic member 4 and the heating sleeve 12 .

[0068] On the other hand, some embodiments of the present invention further provide a method for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion, which is applicable to the device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion described in any of the above embodiments.

[0069] like Figure 6 As shown, the method for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion comprises:

[0070] S1. Preheating the magnesium alloy tube, setting the heating temperature of the vacuum atmosphere heating furnace to 300-500° C., and after the temperature of the heating furnace reaches the set temperature, placing the magnesium alloy tube in the heating furnace for insulation for 2-4 hours.

[0071] S2, the magnesium alloy tube is subjected to torsional extrusion deformation, in which the tube wall of the magnesium alloy tube is subjected to reciprocating torsional deformation around its central axis at a temperature of 300-500°C, the tube wall of the magnesium alloy tube is subjected to shear deformation at the same time, and the tube wall of the magnesium alloy tube is subjected to multiple extrusion deformation.

[0072] In some embodiments, Figure 7 As shown, before preheating the magnesium alloy tube, step S1' is required. Step S1' includes pretreating the magnesium alloy tube. Figure 8 As shown, the method for pretreating the magnesium alloy tube comprises:

[0073] S11, processing the magnesium alloy tube to an outer diameter of D and a tube wall thickness of t.

[0074] S12, removing oil stains from the surface of the magnesium alloy tube.

[0075] S13, grinding the surface of the magnesium alloy tube, wherein the surface of the magnesium alloy tube is less than 0.1a.

[0076] S14, using a cleaning solution to perform ultrasonic cleaning on the magnesium alloy tube for 30 to 60 minutes, then cleaning the magnesium alloy tube with anhydrous ethanol, and finally blowing the magnesium alloy tube dry.

[0077] S15. Apply graphite oil solution to the surface of the magnesium alloy tube and reserve it for later use.

[0078] In some examples, the method for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion of the present invention is combined with the device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion provided in the above embodiment, and the process is as follows:

[0079] Y1. Lubrication of the device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion: smear graphite oil solution on the outer surface of the power transmission rod 11, the outer surfaces of the first threaded shaft segment, the second threaded shaft segment and the third threaded shaft segment, the outer surface of the rotating rod, and the outer surfaces of the first gap and the second gap.

[0080] Y2. Assembly: Assemble the magnesium alloy tube to the device for preparing fine-grained magnesium alloy tube by differential angle reciprocating torsion extrusion. Specifically, the two ends of the magnesium alloy tube are fixed to the corresponding first torsion die and second torsion die. The magnesium alloy tube needs to pass through the first gap and the second gap. It can be understood that for the convenience of installation, the outer extrusion part and the outer torsion part can be two semi-annular structures.

[0081] Y3. Preheating: Control the temperature of the heating jacket to 300~500℃. Keep it warm for 2~4h after reaching the set temperature for later use.

[0082] Y4. Driving the device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion to perform differential-angle reciprocating torsional extrusion deformation:

[0083] Y4-1. The reciprocating torsional deformation of the magnesium alloy tube is that the first threaded shaft segment and the second threaded shaft segment move left and right, and the first torsional die and the second torsional die rotate in opposite directions through the thread, thereby driving the magnesium alloy tube as a whole torsional deformation. The meshed fine thread and coarse thread generate a rotational speed difference when the shearing module and the first torsional die / the second torsional die rotate, thereby causing the magnesium alloy tube blank between the first torsional die / the second torsional die and the shearing module to torsional deformation.

[0084] During the torsional deformation of the magnesium alloy tube billet, due to the opposite torsional directions on the left and right sides, it is easy to generate opposite stress concentration in the middle of the tube billet, causing the tube to break. Therefore, the following steps are used to solve the problem:

[0085] ① Operate the radial clutch between the first threaded shaft segment and the power transmission rod, and the radial clutch between the second threaded shaft segment and the power transmission rod, so that the left telescopic rod drives the first transmission rod to move to the right, and at the same time drives the second transmission rod to move to the right so that the first threaded shaft segment and the second threaded shaft segment move to the right as a whole, thereby driving all the rotating dies engaged with the threads to rotate. From the left perspective of the entire device, the first torsion die and the shearing module near the left rotate counterclockwise, and the second torsion die and the shearing module near the right rotate clockwise. At this time, the opposite stresses on both sides of the magnesium alloy tube are concentrated in the middle of the tube, and the first transmission rod drives the first threaded shaft segment and the second threaded shaft segment to move to the right as a whole. (20mm~80mm) and then stop;

[0086] ② Operate the radial clutch between the first threaded shaft section and the power transmission rod to disengage the first transmission rod from the first threaded shaft section. At this time, when the first transmission rod is moved, the first threaded shaft section does not move left or right. The first transmission rod continues to squeeze to move the second threaded shaft section to the right. (20mm~80mm) and then stop. During this process, the left side of the magnesium alloy tube billet does not rotate, and the right side of the magnesium alloy tube billet continues to rotate clockwise. The magnesium alloy tube billet does not twist in the first gap. At this time, the opposite stress in the middle of the tube billet is concentrated and eliminated. At the same time, the stress is distributed on both sides of the hexagonal channel to avoid stress concentration at one point and cause the tube to break;

[0087] ③ Operate the radial clutch between the first threaded shaft section and the power transmission rod to make the right telescopic rod drive the second threaded shaft section to move to the left (20mm~80mm) and then stop, then fix the first transmission rod and the first threaded shaft section, and finally the second transmission rod drives the first threaded shaft section and the second threaded shaft section to move to the left together (20mm~80mm) and then stop. This process completes the reverse deformation of ① and ② mentioned above, that is, completes a right movement cycle; similarly, the left movement cycle is also completed in similar three steps, the difference is that the whole moves to the left and operates the radial clutch between the second threaded shaft segment and the power transmission rod; in summary, the reciprocating torsional deformation of the magnesium alloy tube blank is completed.

[0088] Y4-2. The variable-angle shear deformation of the magnesium alloy tube billet is accomplished by the rotation of the inner extrusion and the outer extrusion. A centrifugal arc channel is formed between the inner extrusion and the outer extrusion. The centrifugal arc channel is smooth everywhere. Therefore, when the centrifugal circular shearing die rotates, the magnesium alloy tube billet in the channel does not twist with the inner extrusion and the outer extrusion, so that the tube wall of the magnesium alloy tube pressed into an arc in the centrifugal arc channel forms an arc that is convex or concave. The shear angle formed by the tangent at the connection between the arc and the tube wall of the retaining cylinder and the tube wall of the retaining cylinder changes in real time with the inner extrusion and the outer extrusion, such as Figure 4 As shown, the shear angle changes in order: , which ranges from 90° to 270°, and the shear angle change caused by subsequent rotation is the opposite of this change.

[0089] At the same time, when the first threaded shaft section moves left and right, the inner extrusion member and the outer extrusion member are driven to move left and right through the fixed plate. The combination of the left and right movement and rotation causes the magnesium alloy tube blank in the second gap to undergo variable angle shear deformation.

[0090] Y4-3. Control the movement of the first transmission rod and the second transmission rod to drive the first threaded shaft segment and the second threaded shaft segment to cause the magnesium alloy tube blank to undergo torsional deformation and variable angle shear deformation. The first threaded shaft segment and the second threaded shaft segment move back and forth left and right to cause the tube blank to undergo reciprocating torsional deformation and variable angle shear deformation, so that the grains of each section of the magnesium alloy tube are refined; after reciprocating for n times (n≥20 times) and the internal mold is in the initial position, press the stop button to complete the differential angle reciprocating torsional extrusion deformation of the magnesium alloy tube;

[0091] Y4-4. Take out the magnesium alloy tube obtained in step Y4-3, polish its surface with sandpaper, then clean the magnesium alloy tube with the cleaning solution prepared in step Y1-2, finally clean it twice with anhydrous ethanol, and blow dry it with a hair dryer to obtain a high-performance fine-grained magnesium alloy tube that can be put into use directly.

[0092] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0093] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsion extrusion, characterized in that: include: The external mold frame at least comprises a power transmission rod and a heating sleeve, wherein the power transmission rod passes through the heating sleeve and has a tendency to reciprocate along its axial direction; A torsional shearing die is disposed on the power transmission rod in the heating sleeve, and the torsional shearing die is configured to operate under the drive of the power transmission rod; Wherein, the torsion shearing die comprises: A first torsion mold, an annular structure, wherein the first torsion mold is axially fixed relative to the power transmission rod, and the first torsion mold is configured to rotate under the drive of the power transmission rod; A second torsion mold, an annular structure, wherein the second torsion mold is axially fixed relative to the power transmission rod, and the second torsion mold is configured to rotate under the drive of the power transmission rod, and the second torsion mold rotates in an opposite direction relative to the first torsion mold; A plurality of shearing dies are sequentially arranged on the power transmission rod between the first torsion die and the second torsion die, and the plurality of shearing dies include: A shearing module, comprising an inner torsion member and an outer torsion member, wherein the inner torsion member is an annular structure, the inner torsion member is axially fixed relative to the power transmission rod, and the inner torsion member is configured to rotate under the drive of the power transmission rod, and the rotational angular velocity of the inner torsion member is less than the rotational angular velocity of the first torsion mold, the outer ring of the inner torsion member is a polygonal structure, the outer torsion member is an annular structure, the inner ring of the outer torsion member is a polygonal structure consistent with the shape of the outer ring of the inner torsion member, and a first gap is provided between the inner ring of the outer torsion member and the outer ring of the inner torsion member; An extrusion module, at least one side of the shearing module is provided with at least one extrusion module, the extrusion module includes an inner extrusion part and an outer extrusion part, the inner extrusion part is an annular structure, a protrusion is provided on part of the outer wall of the inner extrusion part, and a groove is provided on another part of the outer wall of the inner extrusion part, the protrusion is tangent to the connection position of the groove, the inner extrusion part has a tendency to reciprocate axially with the power transmission rod, and the inner extrusion part also has a tendency to rotate with the shearing module; the outer extrusion part is an annular structure, the inner side wall of the outer extrusion part is adapted to the shape of the outer side wall of the inner extrusion part, the outer extrusion part is sleeved on the inner extrusion part, and a second gap is provided between the inner side wall of the outer extrusion part and the outer side wall of the inner extrusion part, and the central axis of the outer extrusion part is parallel to and not colinear with the central axis of the inner extrusion part, and the outer extrusion part is fixed relative to the inner extrusion part.

2. The device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion according to claim 1 is characterized in that: In two adjacent extrusion modules, the angle between the orthographic projection of the shortest connecting line between the central axis of the outer extrusion piece of one extrusion module and the central axis of the corresponding inner extrusion piece on the first plane and the orthographic projection of the shortest connecting line between the central axis of the outer extrusion piece of the other extrusion module and the central axis of the corresponding inner extrusion piece on the first plane is 60°~120°; The first plane is perpendicular to the central axis of the power transmission rod.

3. The device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion according to claim 2 is characterized in that: A protrusion is provided on half of the outer side wall of the inner extrusion component, and the outer side surface of the protrusion intersects with the cross section passing through the central axis of the inner extrusion component to form a first intersection line, and the curvature of the first intersection line increases from one end of the protrusion to the middle of the protrusion, and decreases to zero from the middle of the protrusion to the other end of the protrusion; A groove is arranged on the other half of the outer side wall of the inner extrusion component, and the outer side surface of the groove intersects with the cross section passing through the central axis of the inner extrusion component to form a second intersection line, and the curvature of the second intersection line increases from one end of the groove to the middle of the groove, and decreases to zero from the middle of the groove to the other end of the groove.

4. The device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion according to claim 3 is characterized in that: The power transmission rod comprises a first threaded shaft segment, the first threaded shaft segment is provided with an external thread, the first torsion die is provided with an internal thread meshing with the external thread of the first threaded shaft segment, the first torsion die is sleeved on the first threaded shaft segment, and when the first threaded shaft segment reciprocates along the axial direction of the power transmission rod, the first torsion die is driven to rotate; The power transmission rod includes a second threaded shaft segment, on which an external thread is provided, and the external thread of the second threaded shaft segment is in the opposite direction to the external thread of the first threaded shaft segment, and the second torsion mold is provided with an internal thread meshing with the external thread of the second threaded shaft segment, and the second torsion mold is mounted on the second threaded shaft segment, and when the second threaded shaft segment reciprocates along the axial direction of the power transmission rod, the second torsion mold is driven to rotate.

5. The device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsion extrusion according to claim 4 is characterized in that: The power transmission rod comprises a plurality of third threaded shaft segments, wherein the thread direction of the third threaded shaft segment close to the first threaded shaft segment among the plurality of third threaded shaft segments is the same as the thread direction of the first threaded shaft segment, and the pitch of the third threaded shaft segment close to the first threaded shaft segment is greater than the pitch of the first threaded shaft segment, and the thread direction of the third threaded shaft segment close to the second threaded shaft segment among the plurality of third threaded shaft segments is the same as the thread direction of the second threaded shaft segment, and the pitch of the third threaded shaft segment close to the first threaded shaft segment is greater than the pitch of the second threaded shaft segment; The inner torsion member is provided with an inner thread meshing with the outer thread of the third threaded shaft segment. The inner torsion member is sleeved on the third threaded shaft segment. When the third threaded shaft segment reciprocates along the axial direction of the power transmission rod, the inner torsion member is driven to rotate.

6. The device for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion according to claim 5 is characterized in that: A plurality of rotating rods are arranged on the side surfaces of the inner torsion member and / or the outer torsion member, and the plurality of rotating rods are parallel to the central axis of the power transmission rod. A plurality of through holes are arranged on the inner extrusion member and the outer extrusion member, and a rotating rod is arranged in each through hole correspondingly, and the rotating rods are configured to drive the inner extrusion member and the outer extrusion member to rotate synchronously with the inner torsion member and / or the outer torsion member.

7. The device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsion extrusion according to claim 6 is characterized in that: The torsion shearing die also includes a plurality of fixed disks, which are annular parts and are coaxially fixed to the power transmission rod; The inner ring of the inner torsion member is provided with an annular groove adapted to the edge of the fixed disk. Each inner torsion member is clamped on a fixed disk, and the fixed disk is configured to drive the inner torsion member to reciprocate along the axial direction of the power transmission rod.

8. The device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsion extrusion according to claim 7 is characterized in that: The power transmission rod comprises a first transmission rod and a second transmission rod; One end of the first transmission rod located in the heating sleeve is connected to one end of the second transmission rod located in the heating sleeve, the central axis of the first transmission rod is colinear with the central axis of the second transmission rod, and the first transmission rod has a tendency to rotate around the central axis of the second transmission rod.

9. A method for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion, applicable to the device for preparing fine-grained magnesium alloy tubes by differential angle reciprocating torsional extrusion as claimed in any one of claims 1 to 8, characterized in that: The method for preparing fine-grained magnesium alloy tubes by differential-angle reciprocating torsional extrusion comprises: Preheating the magnesium alloy tube, setting the heating temperature of the vacuum atmosphere heating furnace to 300-500° C., and after the temperature of the heating furnace reaches the set temperature, placing the magnesium alloy tube in the heating furnace for 2-4 hours; The magnesium alloy tube is subjected to torsional extrusion deformation, in which the tube wall of the magnesium alloy tube is subjected to reciprocating torsional deformation around its central axis at a temperature of 300-500° C., the tube wall of the magnesium alloy tube is subjected to shear deformation at the same time, and the tube wall of the magnesium alloy tube is subjected to multiple extrusion deformations.

10. The method for preparing fine-grained magnesium alloy tube by differential angle reciprocating torsional extrusion according to claim 9, characterized in that: Before preheating the magnesium alloy tube, the magnesium alloy tube needs to be pretreated. The method for pretreating the magnesium alloy tube includes: Processing the magnesium alloy tube to an outer diameter of D and a tube wall thickness of t; Removing oil stains from the surface of the magnesium alloy tube; Grinding the surface of the magnesium alloy tube, wherein the surface of the magnesium alloy tube is less than 0.1a; The magnesium alloy tube is ultrasonically cleaned for 30 to 60 minutes using a cleaning solution, and then the magnesium alloy tube is cleaned using anhydrous ethanol, and the magnesium alloy tube is blown dry; Apply graphite oil solution to the surface of the magnesium alloy tube and reserve it for later use.

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