Device and method for preparing fine-grained magnesium alloy by double-helix torsion complex shear extrusion

Abstract

The application belongs to the field of magnesium alloy processing, and particularly relates to a fine-grained magnesium alloy preparation device and method of double-helix torsion composite shear extrusion. The technical scheme comprises an extrusion part, a power pipe, a concave die positioning block, a concave die, a concave die driving part and a positioning driving part. The extrusion part comprises an end head extending in a first direction, the power pipe comprises a threaded pipe, the concave die positioning block is arranged in the power pipe, the concave die positioning block comprises external threads engaged with the threaded pipe, a positioning cavity and an extrusion through hole are sequentially arranged through a center line of the concave die positioning block and from one end of the concave die positioning block to the other end of the concave die positioning block, the positioning cavity is in communication with the one end of the concave die positioning block, one end of the extrusion through hole is in communication with the positioning cavity, the other end of the extrusion through hole is in communication with the other end of the concave die positioning block, the concave die positioning block rotates during operation of the power pipe, and the concave die oscillates relative to the concave die positioning block when the concave die rotates with the concave die positioning block, so that the magnesium alloy grains are refined, the texture is weakened, and the mechanical properties are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of magnesium alloy processing, and particularly relates to a device and method for preparing fine-grained magnesium alloy through double-helix torsion and composite shearing extrusion. BACKGROUND

[0002] Magnesium alloy is the lightest metal structural material in practical application at present. 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 anti-radiation ability, good thermal conductivity, easy cutting processing and easy recycling, etc. Magnesium alloy has been widely used in the fields of aerospace, transportation, weapon equipment, information industry, etc.

[0003] However, due to the unique hexagonal close-packed structure of magnesium alloy, only 2 independent slip systems are activated at room temperature, which cannot meet the requirement of 5 independent slip systems needed for plastic deformation, so magnesium alloy shows poor mechanical properties and forming properties at room temperature. At the same time, the unique structural characteristics of magnesium alloy lead to the formation of deformation texture during processing. The appearance of deformation texture causes the anisotropy and tension-compression asymmetry of magnesium alloy, which seriously limits its application range and industrialization promotion. Grain refinement can significantly improve the mechanical properties of magnesium alloy materials. Severe plastic deformation technology has been proved to be able to effectively refine the grains of magnesium alloy, such as high-pressure torsion (HPT), multi-directional forging (MDF), equal channel angular pressing (ECAP) and rotary extrusion (TE). However, these severe plastic deformation methods have many technical problems and deficiencies, which greatly limit the realization of large-scale continuous production.

[0004] Therefore, there is an urgent need for a device and method for effectively and greatly refining the grains of magnesium alloy pipes to expand the production efficiency and application range of magnesium alloy pipes. SUMMARY

[0005] To overcome the defects in the above related art, the present application provides a device for preparing fine-grained magnesium alloy by double helix torsion composite shear extrusion. The device comprises an extrusion part, a power tube, a concave die positioning block, a concave die, a concave die driving part and a positioning driving part. The extrusion part comprises at least an end head extending in a first direction. The power tube comprises at least a threaded tube which is a tubular structure with both ends open. The concave die positioning block is a cylindrical structure and is arranged in the power tube. The concave die positioning block comprises an external thread engaged with the threaded tube. A positioning cavity and an extrusion through-hole are arranged in sequence from one end of the concave die positioning block to the other end thereof through the center line of the concave die positioning block. The positioning cavity comprises at least an arc-shaped inner wall and is in communication with the one end of the concave die positioning block. One end of the extrusion through-hole is in communication with the positioning cavity, and the other end of the extrusion through-hole is in communication with the other end of the concave die positioning block. A driving through-hole is further arranged on the concave die positioning block in the radial direction thereof. One end of the driving through-hole is in communication with the positioning cavity, and the other end of the driving through-hole is in communication with other positions on the side wall of the concave die positioning block except the positions where the external thread is arranged.

[0006] The concave die is arranged in the positioning cavity. The outer wall of the concave die is adapted to the inner wall of the positioning cavity. The concave die has a tendency to reciprocally rotate around an axis perpendicular to the first direction. The concave die is provided with an extrusion cavity. One end of the extrusion cavity is in communication with the positioning cavity, and the other end of the extrusion cavity is in communication with the extrusion through-hole. The concave die driving part is arranged in the driving through-hole. The concave die driving part is configured to transmit rotational power to the concave die when the concave die positioning block operates. The positioning driving part is fixed to the power tube. The positioning driving part provides rotational power to the concave die positioning block.

[0007] Preferably, the device for preparing fine-grained magnesium alloy by double helix torsion composite shear extrusion further comprises an extrusion fixed convex die which is a straight rod. The extrusion fixed convex die is fixed opposite to the power tube. The extrusion fixed convex die extends from the extrusion through-hole into the extrusion cavity.

[0008] Preferably, the concave die positioning block further comprises a material placing tube which is a tubular structure with both ends open. The material placing tube is fixed to the side surface of the one end of the concave die positioning block. The center line of the material placing tube is collinear with the center line of the concave die positioning block.

[0009] Preferably, the extrusion cavity comprises a first cavity, a second cavity and a third cavity, wherein the first cavity is a cylindrical structure, one end of the first cavity is in communication with the positioning cavity. The second cavity is a circular truncated cone structure, one end of the second cavity is in communication with the other end of the first cavity. The third cavity is a cylindrical structure, one end of the third cavity is in communication with the other end of the second cavity, and the other end of the third cavity is in communication with the extrusion through-hole. The diameter of the first cavity is greater than the diameter of the third cavity.

[0010] Preferably, the extrusion fixed punch extends from the extrusion through-hole into the second cavity.

[0011] Preferably, the driving through-hole comprises at least a first straight hole perpendicular to the center line of the die positioning block, and the first straight hole is in communication with the positioning cavity. The outer wall of the die is a cylindrical surface or a spherical surface. The power tube further comprises an internal gear, one end of the threaded tube is coaxially fixedly connected with one end of the internal gear, and the center lines of the threaded tube and the internal gear are arranged along the first direction.

[0012] The die driving member comprises a push rod, a connecting rod, a rotating shaft, a first bevel gear, a second bevel gear and a first gear. The push rod is a straight rod, one end of the push rod is fixedly connected with the die, and the other end of the push rod extends into the first straight hole. The connecting rod is a straight rod arranged along the first direction, the connecting rod has a tendency to reciprocate along the first direction, and one end of the connecting rod is hingedly connected with the other end of the push rod. The rotating shaft is arranged perpendicular to the first direction on the die positioning block, one end of the rotating shaft is hingedly connected with the other end of the connecting rod, and a first distance exists between the hingedly connected position of the rotating shaft and the center line of the rotating shaft. The first bevel gear is coaxially fixed to the other end of the rotating shaft; the second bevel gear is engaged with the first bevel gear; the first gear is connected with the die positioning block through a bearing, the first gear is coaxially fixedly connected with the second bevel gear, and the first gear is engaged with the internal gear.

[0013] Preferably, the positioning driving member comprises a first telescopic member; the piston end of the first telescopic member has a tendency to move along the first direction, the piston end of the first telescopic member is connected with the die positioning block, and the first telescopic member is configured to provide a rotating thrust to the die positioning block into the threaded tube.

[0014] Preferably, the positioning driving member further comprises a track, a moving platform and a driving motor.

[0015] In another aspect, the application also provides a method for preparing a fine-grained magnesium alloy by double helix torsion composite shear extrusion, which is suitable for the device for preparing a fine-grained magnesium alloy by double helix torsion composite shear extrusion described in any of the above embodiments. The method for preparing a fine-grained magnesium alloy pipe by double helix torsion composite shear extrusion comprises: preheating the magnesium alloy bulk material, and the preheating temperature is 300-500 DEG C, and the preheating temperature is maintained for 2-4 h. At a temperature of 300-500 DEG C, the magnesium alloy bulk material is extruded in a first direction, and a torsional force perpendicular to the first direction is applied to the outer surface of the magnesium alloy bulk material; wherein the torsional force comprises a first torsional force and a second torsional force, the first torsional force and the second torsional force are opposite in direction, and the magnesium alloy bulk material is reciprocally twisted under the action of the first torsional force and the second torsional force. The magnesium alloy bulk material is extruded in the first direction to enter the device for preparing a fine-grained magnesium alloy by double helix torsion composite shear extrusion and form a pipe, and the magnesium alloy bulk material at the entrance of the device for preparing a fine-grained magnesium alloy by double helix torsion composite shear extrusion is extruded in the circumferential direction.

[0016] The application has the following beneficial effects:

[0017] The first torsion die and the second torsion die are adopted, the magnesium alloy pipe can be twisted and deformed, the grain refinement effect of the magnesium alloy pipe is remarkable, the obtained high-performance fine-grained magnesium alloy pipe has uniform organization, and the strength and toughness are greatly improved. At the same time, the magnesium alloy pipe can be asymmetrically sheared and deformed through the shearing module, and the pipe wall of the magnesium alloy pipe can be extruded and deformed through the extruding module, so that the magnesium alloy pipe is twisted and deformed and also asymmetrically sheared and deformed, the grains are further refined, the texture is weakened, the anisotropy is reduced, the organization is more uniform, and the comprehensive performance of the magnesium alloy pipe is improved. The whole device has a simple structure and is convenient to use. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the technical solutions in the embodiments of the present application or the related art clearer, the accompanying drawings needed in the embodiments or the related art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative work on the basis of these drawings.

[0019] Figure 1 is a structural diagram of the present application;

[0020] Figure 2 is a structural diagram of the die positioning block of the present application;

[0021] Figure 3 is a sectional view of the die positioning block of the present application;

[0022] Figure 4 is a structural diagram of the die of the present application;

[0023] Figure 5 is an installation structural diagram of the die driving member of the present application;

[0024] Figure 6 is an allocation diagram of each region in the extrusion cavity of the die of the present application;

[0025] Figure 7 is a structural diagram of the die of the present application relative to the extrusion fixed punch swing;

[0026] Figure 8 is a twist schematic diagram of the magnesium alloy block in the die of the present application;

[0027] Figure 9 is another structural diagram of the present application. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below by combining the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0029] In the description of the present application, it needs to be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0030] The terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0031] As Figures 1 to 4 shown, some embodiments of the present application provide a double helix torsion composite shear extrusion device for preparing fine-grained magnesium alloy. The double helix torsion composite shear extrusion device for preparing fine-grained magnesium alloy comprises an extrusion part 1, a power tube 2, a concave die positioning block 3, a concave die 4, a concave die driving part 5 and a positioning driving part 6. Wherein, the extrusion part 1 at least includes a tip 11 extending in a first direction X; the power tube 2 at least includes a threaded tube, which is a tubular structure with both ends open. The concave die positioning block 3 is a cylindrical structure as a whole, which is arranged in the power tube 2, and includes an external thread engaged with the threaded tube. A center line passes through the concave die positioning block 3, and a positioning cavity 31 and an extrusion through hole 32 are sequentially arranged from one end of the concave die positioning block 3 to the other end thereof. The positioning cavity 31 at least includes an arc-shaped inner wall, and is in communication with one end of the concave die positioning block 3. One end of the extrusion through hole 32 is in communication with the positioning cavity 31, and the other end of the extrusion through hole 32 is in communication with the other end of the concave die positioning block 3. A driving through hole 33 is further arranged on the concave die positioning block 3 along the radial direction thereof, one end of the driving through hole 33 is in communication with the positioning cavity 31, and the other end of the driving through hole 33 is in communication with other positions on the side wall of the concave die positioning block 3 except the external thread.

[0032] The concave die 4 is arranged in the positioning cavity 31, the outer wall of the concave die 4 is adapted to the inner wall of the positioning cavity 31, the concave die 4 has a tendency to reciprocating rotation around an axis perpendicular to the first direction X, the concave die 4 is provided with an extrusion cavity 41, one end of the extrusion cavity 41 is in communication with the positioning cavity 31, and the other end of the extrusion cavity 41 is in communication with the extrusion through hole 32. The concave die driving member 5 is arranged in the driving through hole 33, and the concave die driving member 5 is configured to transmit rotary power to the concave die 4 when the concave die positioning block 3 is operated. The positioning driving member 5 is fixed to the power pipe 2, and the positioning driving member 5 provides rotary power to the concave die positioning block 3.

[0033] Exemplarily, the end 11 of the extruding member 1 is operated into the extrusion cavity 41 of the concave die 4, and the magnesium alloy block is extruded from the extrusion cavity 41 into the extrusion through hole 32, at the same time, the concave die positioning block 3 is driven to rotate, so that the magnesium alloy block is subjected to a torsional force while being extruded, and in the process that the concave die 4 rotates with the concave die positioning block 3, the concave die 4 swings relative to the concave die positioning block 3 at the same time, and the magnesium alloy block inside is further twisted, so that a secondary helical torsion is formed, and the concave die positioning block can be subjected to multiple torsion and extrusion, so as to refine the magnesium alloy grains and improve the performance of the magnesium alloy.

[0034] In some examples, the fine-grain magnesium alloy preparation device of the double-helical torsion composite shear extrusion further comprises an extrusion fixed convex die 7, the extrusion fixed convex die 7 is a straight rod, the extrusion fixed convex die 7 is fixed relative to the power pipe 2, and the extrusion fixed convex die 7 extends from the extrusion through hole 32 into the extrusion cavity 41.

[0035] Exemplarily, the extrusion fixed convex die 7 can be a cylindrical rod, there is a tubular gap between the extrusion fixed convex die 7 and the extrusion through hole 32, and the extrusion fixed convex die 7 can be fixed to the ground through a support. When the end 11 of the extruding member 1 extrudes the magnesium alloy block, the end of the extrusion fixed convex die 7 located in the extrusion cavity 41 can form a shearing force on the magnesium alloy block, further improving the performance of the magnesium alloy. At the same time, the magnesium alloy block passes through the extrusion through hole 32 and forms a pipe under the action of the extrusion through hole 32 and the extrusion fixed convex die 7.

[0036] A heating jacket is further arranged on the outer side wall of the power pipe 2, and the heating jacket is used for heating the magnesium alloy block in the extrusion cavity.

[0037] In some embodiments, the concave die positioning block 3 further comprises a material placing pipe 33, the material placing pipe 33 is a tubular structure with open ends, the material placing pipe 33 is fixed to the side surface of one end of the concave die positioning block, and the center line of the material placing pipe 33 is collinear with the center line of the concave die positioning block. The material placing pipe 33 facilitates the placement of the magnesium alloy block and is beneficial to material processing.

[0038] In some embodiments, as shown in Figure 4 and Figure 6 The extrusion cavity 41 includes a first cavity 411, a second cavity 412 and a third cavity 413. The first cavity 411 is a cylindrical structure, and one end of the first cavity 411 is in communication with the positioning cavity 31. The second cavity 412 is a circular table structure, and one end of the second cavity 412 is in communication with the other end of the first cavity 411. The third cavity 413 is a cylindrical structure, and one end of the third cavity 413 is in communication with the other end of the second cavity 412, and the other end of the third cavity 413 is in communication with the extrusion through hole 32. The diameter of the first cavity 411 is greater than the diameter of the third cavity 413.

[0039] Exemplarily, the first cavity 411 can be a material placement area A, in which the original magnesium alloy block is placed. The second cavity 412 can be a first torsion area B and a second torsion area C. The third cavity 413 can be a third torsion area D. The first torsion area B, the second torsion area C and the third torsion area D continuously twist the magnesium alloy material entering the area during the magnesium alloy pipe forming process. Through the internal and external reverse differential speed torsion-shear-composite extrusion deformation, the magnesium alloy material can be refined, the texture can be weakened, and the mechanical properties can be improved.

[0040] In some embodiments, the extrusion fixed convex die 7 extends from the extrusion through hole to the second cavity 412. The area of the second cavity 412 where the extrusion fixed convex die 7 is located is the second torsion area C. The area of the second cavity 412 between the second torsion area C and the material placement area A is the first torsion area B. With the rotation of the concave die positioning block and the swing of the concave die, the magnesium alloy block presents a trend of small amplitude torsional deformation-large amplitude torsional deformation-small amplitude torsional deformation in the first torsion area B to the second torsion area C. Specifically, in the first torsion area B, the torsional deformation amplitude of the magnesium alloy block is small. At the joint position of the first torsion area B and the second torsion area C, the torsional deformation amplitude of the magnesium alloy block is large. In the second torsion area C, the torsional deformation amplitude of the magnesium alloy block is small.

[0041] In some embodiments, as shown in Figure 5 and Figure 7 The driving through hole 33 includes at least a first straight hole 331 perpendicular to the center line of the concave die positioning block, and the first straight hole 331 is in communication with the positioning cavity 31. The outer wall of the concave die 4 is a cylindrical surface or a spherical surface. The power pipe 2 further includes an internal gear 21. One end of the threaded pipe is fixedly connected with one end of the internal gear 21 in a same axis, and the center lines of the threaded pipe and the internal gear are arranged along the first direction X.

[0042] The die driving component 5 includes: a toggle rod 51, a connecting rod 52, a rotating shaft 53, a first bevel gear 54, a second bevel gear 55, and a first gear 56. The toggle rod 51 is a straight rod, one end of which is fixedly connected to the die, and the other end extends into the first straight hole 331. The connecting rod 52 is a straight rod, arranged along the first direction X, and has a tendency to reciprocate along the first direction X. One end of the connecting rod 52 is hinged to the other end of the toggle rod 51. The rotating shaft 53 is perpendicular to the first direction X and is mounted on the die positioning block 3. One end of the rotating shaft 53 is hinged to the other end of the connecting rod 52, and a first distance H exists between the hinge position of the rotating shaft 53 and the connecting rod 52 and the centerline of the rotating shaft 53. The first bevel gear 54 is coaxially fixed to the other end of the rotating shaft 53; the second bevel gear 55 meshes with the first bevel gear 54; the first gear 56 is connected to the die positioning block through a bearing, the first gear 56 and the second bevel gear 55 are coaxially fixedly connected, and the first gear 56 meshes with the internal gear.

[0043] For example, the other end of the actuating lever 51 can be connected to one end of the connecting rod 52 by a ball joint. There is a first distance H between the hinge position of the rotating shaft 53 and the connecting rod 52 and the center line of the rotating shaft 53. That is, an eccentric wheel is provided between the other end of the connecting rod 52 and the rotating shaft 53. The center of the eccentric wheel is coaxially and fixedly connected to the rotating shaft 53, and the edge of the eccentric wheel is hinged to the other end of the connecting rod 52.

[0044] When the die positioning block 3 rotates, the first gear 56 meshes with the internal gear. The rotation of the first gear 56 drives the actuating rod 51 to cause the die 4 to swing relative to the die positioning block 3. Figure 7 As shown, the oscillation of the die 4 relative to the die positioning block 3 causes the magnesium alloy block to have different feeding speeds at different positions of the extrusion through hole, which further deflects the magnesium alloy.

[0045] In some embodiments, the positioning drive includes a first telescopic member; the piston end of the first telescopic member has a tendency to run along the first direction, the piston end of the first telescopic member is connected to the die positioning block, and the first telescopic member is configured to provide the die positioning block with a thrust that rotates into the threaded tube.

[0046] In some examples, an annular groove is provided on the end face of the die positioning block, the piston end of the first telescopic member is movably disposed in the annular groove, and an anti-detachment ring is fixed to the opening of the annular groove. The anti-detachment ring is used to prevent the piston end of the first telescopic member from falling out of the annular groove.

[0047] In some embodiments, such as Figure 9As shown, the positioning drive 6 further comprises a track 61, a moving platform 62 and a drive motor 63. The track 61 is arranged along the first direction X and fixed to the power pipe 2. The moving platform 62 is movably arranged on the track 61 and has a tendency to reciprocate along the track 61. The moving platform 62 is connected to the die positioning block 3 in the first direction X. The drive motor 63 is fixed to the moving platform 62, and the output shaft of the drive motor 63 is connected to the die positioning block 3. The drive motor 63 is configured to provide rotational power to the die positioning block 3.

[0048] Exemplarily, the track 61 is fixed below the die positioning block 3, and the track 61 can be two V-shaped tracks arranged in parallel. The die positioning block 3 is provided with a protruding pipe on the cross section. The protruding pipe is connected to the moving platform 62 through a bearing, so that the die positioning block 3 can rotate and drive the moving platform 62 to reciprocate along the track. Meanwhile, the protruding pipe is further provided with a second gear. The output shaft of the drive motor 63 is fixed with a third gear. The second gear and the third gear are engaged, so that the drive motor 63 drives the die positioning block 3 to rotate.

[0049] On the other hand, the application further provides a method for preparing a fine-grained magnesium alloy by double-helix torsion composite shear extrusion, which is suitable for the double-helix torsion composite shear extrusion fine-grained magnesium alloy preparation device described in any one of the above embodiments. The method for preparing a fine-grained magnesium alloy pipe by double-helix torsion composite shear extrusion comprises: preheating the magnesium alloy block material, and the preheating temperature is 300-500°C, and the preheating temperature is maintained for 2-4h. At a temperature of 300-500°C, the magnesium alloy block is extruded in the first direction, and a torsional force perpendicular to the first direction is applied to the outer surface of the magnesium alloy block. The torsional force comprises a first torsional force and a second torsional force, the directions of the first torsional force and the second torsional force are opposite, and the magnesium alloy block is reciprocally twisted under the action of the first torsional force and the second torsional force. The magnesium alloy block is extruded in the first direction to enter the double-helix torsion composite shear extrusion fine-grained magnesium alloy preparation device and form a pipe, and the magnesium alloy block at the entrance of the double-helix torsion composite shear extrusion fine-grained magnesium alloy preparation device is extruded in the circumferential direction.

[0050] Exemplarily, the method for preparing a fine-grained magnesium alloy by double-helix torsion composite shear extrusion suitable for the double-helix torsion composite shear extrusion fine-grained magnesium alloy preparation device described in any one of the above embodiments comprises:

[0051] S1, pre-treating the magnesium alloy block.

[0052] S2, preheating the magnesium alloy block: set the heating temperature of the vacuum atmosphere heating furnace to 450℃, after the furnace temperature reaches the set temperature, put the magnesium alloy block into the heating furnace, and keep it for 3h.

[0053] S3, lubricating, assembling and preheating the fine-grained magnesium alloy preparation device for double-helix torsion composite shear extrusion.

[0054] S4, using the fine-grained magnesium alloy preparation device for double-helix torsion composite shear extrusion to perform internal and external torsion extrusion forming on the magnesium alloy block.

[0055] In some examples, the method for pre-treating the magnesium alloy block comprises:

[0056] S1-1, process the magnesium alloy block into a cylindrical magnesium alloy rod, and polish the surface of the magnesium alloy rod with 600 mesh sandpaper to remove oil stains, then polish it with 800 mesh, 1000 mesh and 1200 mesh sandpaper in turn until the surface of the magnesium alloy rod is smooth.

[0057] S1-2, mix acetone and anhydrous ethanol in a volume ratio of 3:2 in a cleaning tank, and stir until uniform to prepare a cleaning solution.

[0058] S1-3, immerse the magnesium alloy rod prepared in step S1-1 in the cleaning solution prepared in step S1-2, place the cleaning tank on the ultrasonic cleaner and ultrasonically clean the magnesium alloy rod for 60 min, then take out the magnesium alloy rod and clean it with anhydrous ethanol, and finally dry it with a hair dryer.

[0059] S1-4, apply graphite oil solution to the surface of the magnesium alloy rod prepared in step S1-3 for later use.

[0060] In some examples, the method for lubricating the fine-grained magnesium alloy preparation device for double-helix torsion composite shear extrusion comprises: applying graphite oil solution to the inner surface of the power tube, the inner surface of the charging tube, the inner and outer surfaces of the die positioning block, the outer surface of the die, the extrusion cavity, the outer surface of the fixed extrusion punch and the surface of the extrusion part.

[0061] In some examples, the method for preheating the fine-grained magnesium alloy preparation device for double-helix torsion composite shear extrusion comprises: controlling the heating temperature to be 300-500℃, keeping it for 2-4h after reaching the set temperature, and waiting for later use.

[0062] In some examples, the method for internal and external torsion extrusion forming comprises:

[0063] S4-1, the end of the extrusion piece is withdrawn from the material placing pipe, the magnesium alloy rod is placed in the material placing area A, and then the end of the extrusion piece is pushed into the material placing pipe again; the end of the extrusion piece is operated to push the magnesium alloy rod to the right, and the first telescopic piece is operated to push to the left, the concave die positioning block moves to the left and rotates in the threaded pipe during the extrusion process, the rotation of the concave die positioning block drives the rotation of the concave die, the first gear starts to rotate by meshing with the internal gear, and the connecting rod 52 can reciprocate in the first direction X on the rotating shaft 53, and then the concave die generates partial circumferential motion in the concave die positioning block by the operation of the rod. The distance between the concave die and the fixed extrusion convex die changes periodically, resulting in different feeding speeds of the magnesium alloy rod into different positions of the extrusion hole.

[0064] The twisting direction inside the concave die is opposite to that of the fixed extrusion convex die, the twisting angles of the same distance are different, realizing reverse differential twisting inside and outside; the partial circumferential motion of the concave die causes irregular changes in the degree of shear in the third twisting area D; during the twisting and extrusion forming process, the heating temperature is controlled to be 300-500 DEG C.

[0065] S4-2, the magnesium alloy rod is controlled to occur shear deformation in the material placing area A, the first twisting area B, the second twisting area C and the third twisting area D by left and right extrusion, and finally discharged in the third twisting area D. The reverse differential twisting deformation inside and outside causes the grains of each section of the magnesium alloy rod to be refined. After the end of the extrusion piece and the first telescopic piece are displaced by a certain distance, the reverse differential twisting-shear deformation of the magnesium alloy rod is completed, and a uniform magnesium alloy pipe with fine grains is obtained.

[0066] S4-3, the magnesium alloy pipe prepared in step S4-2 is taken out, the surface thereof is polished with sandpaper, then the magnesium alloy pipe is cleaned with the cleaning solution prepared in step S1-2, finally, the magnesium alloy pipe is cleaned with anhydrous ethanol again, and dried with a hair dryer, to obtain a fine-grained and weak-textured magnesium alloy pipe which can be directly used.

[0067] In the description of the present specification, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0068] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A device for preparing fine-grained magnesium alloys by double-helix torsion composite shear extrusion, characterized in that, include: An extruded part, including at least an end that extends or retracts in a first direction; The power pipe includes at least a threaded pipe, wherein the threaded pipe is a tubular structure open at both ends; A die positioning block, which is cylindrical in shape, is disposed inside the power pipe. The die positioning block includes an external thread that meshes with the threaded pipe. A positioning cavity and a pressing through hole are sequentially provided from one end of the die positioning block to the other end, passing through the center line of the die positioning block. The positioning cavity includes at least an arc-shaped inner wall. The positioning cavity is connected to one end of the die positioning block. One end of the pressing through hole is connected to the positioning cavity, and the other end of the pressing through hole is connected to the other end of the die positioning block. A driving through hole is also provided radially on the die positioning block. One end of the driving through hole is connected to the positioning cavity, and the other end of the driving through hole is connected to other positions on the side wall of the die positioning block except for those provided with external threads. A die is disposed within the positioning cavity, the outer wall of the die adapting to the inner wall of the positioning cavity, the die having a tendency to reciprocate around an axis perpendicular to the first direction, the die being provided with an extrusion cavity, one end of the extrusion cavity communicating with the positioning cavity, and the other end of the extrusion cavity communicating with the extrusion through hole; A die driving component is disposed within the driving through hole, and the die driving component is configured to transmit rotational power to the die when the die positioning block is in operation; A positioning drive component is fixed to the power pipe, and the positioning drive component provides rotational power to the die positioning block.

2. The apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion according to claim 1, characterized in that, The fine-grained magnesium alloy preparation device for double-helix torsion composite shear extrusion further includes an extrusion fixing punch, which is a straight rod and is fixed relative to the power tube. The extrusion fixing punch extends from the extrusion through hole into the extrusion cavity.

3. The apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion according to claim 2, characterized in that, The die positioning block also includes a material placement tube, which is a tubular structure with openings at both ends. The material placement tube is fixed to the side of one end of the die positioning block, and the center line of the material placement tube is collinear with the center line of the die positioning block.

4. The apparatus for preparing fine-grained magnesium alloys by double-helix torsion composite shear extrusion according to claim 2 or 3, characterized in that, The extrusion chamber includes: The first cavity is a cylindrical structure, and one end of the first cavity is connected to the positioning cavity; The second cavity has a frustum structure, and one end of the second cavity is connected to the other end of the first cavity; The third cavity is a cylindrical structure. One end of the third cavity is connected to the other end of the second cavity, and the other end of the third cavity is connected to the extrusion through hole. The diameter of the first cavity is larger than the diameter of the third cavity.

5. The apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion according to claim 4, characterized in that, The extrusion fixing punch extends from the extrusion through hole into the second cavity.

6. The apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion according to claim 1, characterized in that, The driving through hole includes at least a first straight hole perpendicular to the center line of the die positioning block, and the first straight hole communicates with the positioning cavity; The outer wall of the cavity mold is a cylindrical or spherical surface; The power tube also includes an internal gear, one end of the threaded tube is coaxially and fixedly connected to one end of the internal gear, and the center lines of the threaded tube and the internal gear are arranged along the first direction; The die drive component includes: The actuating rod is a straight rod, one end of which is fixedly connected to the die, and the other end of which extends into the first straight hole; The connecting rod is a straight rod, arranged along the first direction, and the connecting rod has a tendency to reciprocate along the first direction. One end of the connecting rod is hinged to the other end of the actuating rod. A rotating shaft is disposed on the die positioning block perpendicular to the first direction. One end of the rotating shaft is hinged to the other end of the connecting rod, and there is a first distance between the hinge position of the rotating shaft and the connecting rod and the center line of the rotating shaft. The first bevel gear is coaxially fixed to the other end of the rotating shaft; The second bevel gear meshes with the first bevel gear; The first gear is connected to the die positioning block via a bearing. The first gear is coaxially and fixedly connected to the second bevel gear, and the first gear meshes with the internal gear.

7. The apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion according to claim 1, characterized in that, The positioning drive component includes a first telescopic component; The piston end of the first telescopic member has a tendency to run along the first direction, the piston end of the first telescopic member is connected to the die positioning block, and the first telescopic member is configured to provide the die positioning block with a thrust that rotates into the threaded tube.

8. The apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion according to claim 1, characterized in that, The positioning drive also includes: The track is arranged along the first direction and fixed to the power pipe; A mobile platform is movably mounted on the track and has a tendency to reciprocate along the track, and the mobile platform is fixed to the die positioning block in a first direction; A drive motor is fixed to the moving platform, and the output shaft of the drive motor is connected to the die positioning block. The drive motor is configured to provide rotational power to the die positioning block.

9. A method for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion, applicable to the apparatus for preparing fine-grained magnesium alloy by double-helix torsion composite shear extrusion as described in any one of claims 1 to 8, characterized in that, The method for preparing fine-grained magnesium alloy tubing by double-helix torsion composite shear extrusion includes: The magnesium alloy block blank is preheated at a temperature of 300~500℃ and held at the preheating temperature for 2~4 hours. At a temperature of 300~500℃, the magnesium alloy block is extruded in a first direction, and a torsional force perpendicular to the first direction is applied to the outer surface of the magnesium alloy block; wherein the torsional force includes a first torsional force and a second torsional force, the first torsional force and the second torsional force are in opposite directions, and the magnesium alloy block is reciprocated torsion under the action of the first torsional force and the second torsional force; The magnesium alloy block is extruded along a first direction to enter a fine-grained magnesium alloy preparation device of double-helix torsion composite shear extrusion and form a tube. At the same time, the magnesium alloy block at the inlet of the fine-grained magnesium alloy preparation device of double-helix torsion composite shear extrusion is extruded circumferentially.

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