Device and method for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion

Abstract

The application belongs to the field of magnesium alloy processing and relates to a device and method for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion. The technical scheme comprises a first power mechanism, a second power mechanism, an extrusion outer die and an extrusion inner die. The first power mechanism comprises a first extrusion ring, the second power mechanism comprises a second extrusion ring, and the first extrusion ring and the second extrusion ring have a tendency to reciprocate in a first direction. The extrusion outer die comprises a through hole and is arranged between the first extrusion ring and the second extrusion ring, the extrusion outer die is connected with the first power mechanism, and the first power mechanism drives the extrusion outer die to rotate around the center line thereof when the first extrusion ring operates. The extrusion inner die is arranged in the through hole and is connected with the second power mechanism, and the second power mechanism drives the extrusion inner die to rotate around the center line thereof when the second extrusion ring operates. The application can extrude and twist the inner wall of the magnesium alloy pipe, so that the magnesium alloy pipe generates extrusion deformation, twisting and shearing deformation, and the magnesium alloy pipe grain is further refined.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of magnesium alloy processing, and particularly relates to a device and method for preparing fine-grained magnesium alloy pipe by reciprocating radial 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. Therefore, magnesium alloy exhibits poor mechanical properties and forming properties at room temperature. At the same time, the unique structural characteristics of magnesium alloy often 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 preparation.

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

[0005] To overcome the defects in the above related technology, on the one hand, the present application provides a device for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion. The device for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion comprises a first power mechanism, a second power mechanism, an extrusion outer die and an extrusion inner die. The first power mechanism comprises at least a first extrusion ring, which has a tendency to reciprocate in a first direction. The second power mechanism comprises at least a second extrusion ring, the center line of which is collinear with the center line of the first extrusion ring, and the second extrusion ring has a tendency to reciprocate in the first direction. The extrusion outer die is arranged between the first extrusion ring and the second extrusion ring, and the extrusion outer die comprises at least a through hole arranged in the first direction, the center line of the through hole is collinear with the center line of the first extrusion ring or the center line of the second extrusion ring, the extrusion outer die is connected with the first power mechanism, and when the first extrusion ring operates, the first power mechanism has a tendency to drive the extrusion outer die to rotate around its center line. The extrusion inner die is arranged in the through hole, and a die gap is arranged between the extrusion inner die and the inner wall of the through hole. The extrusion inner die is connected with the second power mechanism, and when the second extrusion ring operates, the second power mechanism has a tendency to drive the extrusion inner die to rotate around its center line.

[0006] Preferably, the extrusion outer die comprises, in order from one end close to the first extrusion ring to the other end, a left fixed circular die, a necking concave die, a transition circular die and an expanding convex die. The left fixed circular die is a straight pipe with a circular cross section; the necking concave die is a straight pipe with a polygonal cross section, one end of the necking concave die communicates with the left fixed circular die, and the polygon formed by the normal projection of the necking concave die on the end face of the left fixed circular die is inscribed in the circular end face of the left fixed circular die. The transition circular die is a straight pipe with a circular cross section, and the transition circular die communicates with the other end of the necking concave die. The expanding convex die is a variable diameter pipe with increasing diameter from one end to the other end, and one end of the expanding convex die communicates with the transition circular die. The right fixed circular die is a straight pipe with a circular cross section, and the right fixed circular die communicates with the other end of the expanding convex die.

[0007] Preferably, the device for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion further comprises a support, and two ends of the outer extrusion die are connected to corresponding supports through bearings. The first power mechanism further comprises a first rack, a first gear, a gear steering box, a second gear and a third gear. The first rack is fixedly connected to the first extrusion ring, and the first rack has a tendency to reciprocate in the first direction along with the first extrusion ring. The first gear is engaged with the first rack, and the input end of the gear steering box is fixedly connected to the first gear in a coaxial manner. The second gear is fixedly connected to the output end of the gear steering box in a coaxial manner, and the third gear is fixedly connected to the outer extrusion die in a coaxial manner. The second gear is engaged with the third gear.

[0008] Preferably, the inner extrusion die comprises, from one end close to the first extrusion ring to the other end, a left fixed inner extrusion die, a polygonal inner extrusion die, a transition inner extrusion die, a flared inner extrusion die and a right fixed inner extrusion die. The left fixed inner extrusion die is a straight rod with a circular cross section, is arranged in the left fixed circular die, and the shortest distance between the outer wall of the left fixed inner extrusion die and the inner wall of the left fixed circular die is equal. The polygonal inner extrusion die is a straight rod with a polygonal cross section that is adapted to the inner wall of the necking concave die, is arranged in the necking concave die, is fixedly connected to the left fixed inner extrusion die in a coaxial manner, and the polygon formed by the orthogonal projection of the polygonal inner extrusion die on the end face of the left fixed inner extrusion die is inscribed in the circular end face of the left fixed inner extrusion die. The transition inner extrusion die is a straight rod with a circular cross section, is arranged in the transition circular die, and is fixedly connected to the polygonal inner extrusion die in a coaxial manner. The flared inner extrusion die has a generally circular truncated cone structure, is arranged in the flared convex die, and the diameter of the flared inner extrusion die increases from one end to the other end. The flared inner extrusion die is fixedly connected to the transition inner extrusion die in a coaxial manner at one end. The right fixed inner extrusion die is a straight rod with a circular cross section, is arranged in the right fixed circular die, and is fixedly connected to the other end of the flared inner extrusion die in a coaxial manner.

[0009] Preferably, the two ends of the inner extrusion die are connected to corresponding supports through bearings. The second power mechanism comprises a threaded rod and a rotating member. The threaded rod is fixedly connected to the second extrusion ring in a coaxial manner, and the threaded rod is a straight rod as a whole. At least one thread groove or thread protrusion extending along the axial direction of the threaded rod is arranged on the surface of the threaded rod. The rotating member is an annular member as a whole. A protrusion adapted to the thread groove is arranged on the inner side wall of the rotating member, or a groove adapted to the thread protrusion is arranged on the inner side wall of the rotating member. The rotating member is fixedly connected to the inner extrusion die in a coaxial manner. When the threaded rod runs linearly, the rotating member has a tendency to rotate around the center line thereof.

[0010] Preferably, the flared extrusion inner die comprises a plurality of circular truncated cones arranged along a first direction. The circular truncated cone comprises a first end face and a second end face, the diameter of the first end face is smaller than the diameter of the second end face, and the diameters of the first end faces and the second end faces of two adjacent circular truncated cones are the same. A center line passing through the center points of the first end face and the second end face of the circular truncated cone forms an angle with the first direction, and the center lines of two adjacent circular truncated cones are not collinear.

[0011] Preferably, a flared extrusion transition die is arranged between two adjacent circular truncated cones, the flared extrusion transition die is in a cylindrical structure, the diameter of the end face of the flared extrusion transition die is the same as that of the first end face or the second end face of the adjacent circular truncated cone, and one end face of the flared extrusion transition die is fixedly connected with the first end face of the adjacent circular truncated cone, and the other end face of the flared extrusion transition die is fixedly connected with the second end face of the other adjacent circular truncated cone.

[0012] Preferably, the first power mechanism comprises a first telescopic machine, the piston of the first telescopic machine is fixedly connected with the first extrusion ring, the first extrusion ring is in a tubular structure, at least part of the structure of the first extrusion ring is arranged in the extrusion outer die and is sleeved on the extrusion inner die.

[0013] Preferably, the second power mechanism comprises a second telescopic machine, the piston of the second telescopic machine is fixedly connected with the second extrusion ring, the second extrusion ring is in a tubular structure, at least part of the structure of the second extrusion ring is arranged in the extrusion outer die and is sleeved on the extrusion inner die.

[0014] In another aspect, the application further provides a method for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion, which is suitable for the device for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion described in any of the above embodiments. The method for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion comprises: pretreating a magnesium alloy pipe to keep the surface of the magnesium alloy pipe smooth; preheating the magnesium alloy pipe; repeatedly extruding the magnesium alloy pipe along its axial direction; and repeatedly extruding and expanding the magnesium alloy pipe along its radial direction, while extruding and twisting the pipe wall of the magnesium alloy pipe.

[0015] Compared with the prior art, the application has the following beneficial effects:

[0016] The first extrusion ring and the second extrusion ring are adopted in the application, the magnesium alloy pipe can be extruded in the axial direction, the extrusion outer die and the extrusion inner die are rotated, the inner wall of the magnesium alloy pipe can be extruded, and the pipe wall of the magnesium alloy pipe is twisted, so that the magnesium alloy pipe is deformed in multiple directions, such as extrusion, twisting and shearing, and the grains of the magnesium alloy pipe are effectively refined, so that the room-temperature mechanical properties and forming properties of the magnesium alloy pipe are improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural view of some embodiments in the present application;

[0018] Figure 2 is a partial sectional view of some embodiments in the present application;

[0019] Figure 3 is a plan view of some embodiments in the present application near the first power mechanism;

[0020] Figure 4 is a sectional view of the extrusion outer die of some embodiments in the present application;

[0021] Figure 5 is a structural view of the extrusion inner die of some embodiments in the present application;

[0022] Figure 6 is an extrusion structure view of the extrusion outer die and the extrusion inner die on the magnesium alloy pipe of some embodiments in the present application;

[0023] Figure 7 is another extrusion structure view of the extrusion outer die and the extrusion inner die on the magnesium alloy pipe of some embodiments in the present application;

[0024] Figure 8 is a structural view of the left fixed extrusion inner die, the polygonal extrusion inner die and the transition extrusion inner die of some embodiments in the present application;

[0025] Figure 9 is a sectional view of the H-H direction; Figure 8

[0026] is a perspective view of Figure 10 Figure 8 DETAILED DESCRIPTION

[0027] In order to make the above objectives, features and advantages of the present application more obvious and comprehensible, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0028] ​​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 therefore cannot be understood as indicating or implying 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 limiting the present application.

[0029] 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.

[0030] Some embodiments of the present application provide a device for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion. As shown in Figure 1 、 Figure 2 and Figure 3 , wherein, Figure 1 is a structural diagram of the present embodiment, Figure 2 is a partial sectional view of the present embodiment, Figure 3 is a top view of the first power mechanism part of the present embodiment. The device for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion comprises a first power mechanism 1, a second power mechanism 2, an extrusion outer die 3 and an extrusion inner die 4. The first power mechanism 1 comprises at least a first extrusion ring 11, which has a tendency to reciprocate in the first direction X. The second power mechanism 2 comprises at least a second extrusion ring 21, the center line of which is collinear with the center line of the first extrusion ring 11, and the second extrusion ring 21 has a tendency to reciprocate in the first direction X. The extrusion outer die 3 is arranged between the first extrusion ring 11 and the second extrusion ring 21, and comprises at least a through hole arranged in the first direction X, the center line of which is collinear with the center line of the first extrusion ring 11 or the center line of the second extrusion ring 21. The extrusion outer die 3 is connected with the first power mechanism 1, and the first power mechanism 1 has a tendency to drive the extrusion outer die 3 to rotate around its center line when the first extrusion ring 11 operates. The extrusion inner die 4 is arranged in the through hole, and a die gap H is arranged between the extrusion inner die 4 and the inner wall of the through hole. The extrusion inner die 4 is connected with the second power mechanism 2, and the second power mechanism 2 has a tendency to drive the extrusion inner die 4 to rotate around its center line when the second extrusion ring 21 operates.

[0031] Preferably, the first power mechanism 1 comprises a first telescopic machine 12, a piston of the first telescopic machine 12 is fixedly connected with the first extrusion ring 11, the first extrusion ring 11 is a tubular structure, at least part of the structure of the first extrusion ring 11 is arranged in the extrusion outer die 3 and is sleeved on the extrusion inner die 4.

[0032] Preferably, the second power mechanism 2 comprises a second telescopic machine 22, a piston of the second telescopic machine 22 is fixedly connected with the second extrusion ring 21, the second extrusion ring 21 is a tubular structure, at least part of the structure of the second extrusion ring 21 is arranged in the extrusion outer die 3 and is sleeved on the extrusion inner die 4.

[0033] Exemplarily, the first telescopic machine 12 and the second telescopic machine 22 can be hydraulic telescopic machines, a piston end of the first telescopic machine 12 is fixedly connected with the first extrusion ring 11, a piston end of the second telescopic machine 22 is fixedly connected with the second extrusion ring 21, the extrusion inner die 4 can be a rod-shaped structure as a whole, and the extrusion outer die 3 can be a tubular structure as a whole, wherein the extrusion inner die 4 is movably arranged in the extrusion outer die 3, and a gap, i.e., a molding gap H, is arranged between the extrusion inner die 4 and the extrusion outer die 3, and the gap is used for placing the magnesium alloy pipe. That is, the inner diameter of the magnesium alloy pipe is greater than the diameter of one end of the extrusion inner die 4, and the outer diameter of the magnesium alloy pipe is less than the diameter of one end of the extrusion outer die 3, so that the magnesium alloy pipe can be arranged in the gap, and the first extrusion ring 11 or the second extrusion ring 21 can perform extrusion work on the magnesium alloy pipe.

[0034] It can be understood that the first extrusion ring 11 is arranged at one end of the extrusion outer die 3, so that the first extrusion ring 11 can reciprocally extrude the magnesium alloy pipe in the first direction X, the first extrusion ring 11 can reciprocally slide in the gap, that is, the inner diameter of the first extrusion ring 11 is greater than the diameter of one end of the extrusion inner die 4, and the outer diameter of the first extrusion ring 11 is less than the diameter of one end of the extrusion outer die 3. Similarly, the second extrusion ring 21 is arranged at the other end of the extrusion outer die 3, the inner diameter of the second extrusion ring 21 is greater than the diameter of the other end of the extrusion inner die 4, and the outer diameter of the second extrusion ring 21 is less than the diameter of the other end of the extrusion outer die 3.

[0035] In some examples, the device for preparing fine-grained magnesium alloy pipe by radial extrusion can further comprise a support 5, and the support 5 can comprise a first support frame 51 and a second support frame 52. Two first support frames 51 are oppositely arranged and fixed to the ground, wherein the two ends of the extrusion outer die 3 are connected to the two first support frames 51 through bearings in one-to-one correspondence; on the outer sides of the two first support frames 51, two second support frames 52 are oppositely arranged and fixed to the ground, wherein the end of the extrusion outer die 3 passes through the corresponding first support frame 51 and is connected to the corresponding second support frame 52 through a bearing.

[0036] It can be understood that the first extrusion ring 11 is inserted into the gap between the extrusion outer die 3 and the extrusion inner die 4 after penetrating through the first support frame 51. The second extrusion ring 21 is inserted into the gap between the extrusion outer die 3 and the extrusion inner die 4 after penetrating through the first support frame 51, and the first extrusion ring 11 is arranged at one end of the extrusion outer die 3 or the extrusion inner die 4 close to the first power mechanism 1, and the second extrusion ring 21 is arranged at one end of the extrusion outer die 3 or the extrusion inner die 4 close to the second power mechanism 2.

[0037] In some examples, the first extrusion ring 11 can be coaxially fixedly connected with the piston of the first power mechanism 1, wherein the piston of the first power mechanism 1 is located on the side of the second support frame 52 away from the first support frame 51, and the piston of the first power mechanism 1 and the first extrusion ring 11 can be fixedly connected through a plurality of connecting rods or straight pipes. Specifically, the plurality of connecting rods are arranged along the first direction X, and in a cross section perpendicular to the first direction X, the plurality of connecting rods can be uniformly arranged. One end of the plurality of connecting rods is fixedly connected with the piston of the first power mechanism 1, and the other end of the plurality of connecting rods is fixedly connected with the first extrusion ring 11. It can be understood that the connecting rods should avoid the second support frame 52 to prevent the second support frame 52 from interfering with the operation of the connecting rods in the first direction X. The connection mode of the straight pipes is the same as that of the plurality of connecting rods, and will not be described here.

[0038] The second extrusion ring 21 can be coaxially fixedly connected with the piston of the second power mechanism 2, wherein the piston of the second power mechanism 2 is located on the side of the second support frame 52 away from the first support frame 51, and the piston of the second power mechanism 2 and the second extrusion ring 21 can be fixedly connected through a plurality of connecting rods or straight pipes. The specific connection mode is the same as that of the first extrusion ring 11 and the piston of the first power mechanism 1, and will not be described here.

[0039] In some embodiments, as shown in Figure 4 The extrusion outer die sequentially comprises, from one end close to the first extrusion ring to the other end, a left fixed circular die 31, a necking concave die 32, a transition circular die 33, and an expanding convex die 34. The left fixed circular die 31 is a straight pipe with a circular cross section. The necking concave die 32 is a straight pipe with a polygonal cross section, one end of the necking concave die 32 communicates with the left fixed circular die 31, and the orthogonal projection of the necking concave die 32 on the end face of the left fixed circular die 31 forms a polygon that is inscribed in the circular end face of the left fixed circular die 31. The transition circular die 33 is a straight pipe with a circular cross section, and the transition circular die 33 communicates with the other end of the necking concave die 32. The expanding convex die 34 is a variable-diameter pipe with increasing diameter from one end to the other end, and one end of the expanding convex die 34 communicates with the transition circular die 33. The right fixed circular die 35 is a straight pipe with a circular cross section, and the right fixed circular die 35 communicates with the other end of the expanding convex die 34.

[0040] Preferably, as shown in Figure 5 and Figures 8 to 10 , the extrusion inner die sequentially includes: left fixed extrusion inner die 41, polygonal extrusion inner die 42, transition extrusion inner die 43, flared extrusion inner die 44 and right fixed extrusion inner die 45 from one end to the other end close to the first extrusion ring. Among them, the left fixed extrusion inner die 41 is a straight rod with a circular cross section, which is arranged in the left fixed circular die, and the shortest distance between the outer wall of the left fixed extrusion inner die 41 and the inner wall of the left fixed circular die is equal. The cross section of the polygonal extrusion inner die 42 is a straight rod with a polygonal shape that matches the inner wall of the necking concave die, which is arranged in the necking concave die. The polygonal extrusion inner die 42 is coaxially fixedly connected with the left fixed extrusion inner die 41, and the polygon formed by the orthogonal projection of the polygonal extrusion inner die 42 on the end face of the left fixed extrusion inner die 41 is inscribed in the circular end face of the left fixed extrusion inner die 41. The cross section of the transition extrusion inner die 43 is a straight rod with a circular shape, which is arranged in the transition circular die, and the transition extrusion inner die 43 is coaxially fixedly connected with the polygonal extrusion inner die 42. The flared extrusion inner die 44 is generally a circular truncated cone 441 structure, which is arranged in the flared convex die 34. The diameter of the flared extrusion inner die 44 increases from one end to the other end, and the flared extrusion inner die 44 is coaxially fixedly connected with the transition extrusion inner die 43 at one end. The cross section of the right fixed extrusion inner die 45 is a straight rod with a circular shape, which is arranged in the right fixed circular die 35, and the right fixed extrusion inner die 45 is coaxially fixedly connected with the other end of the flared extrusion inner die 44.

[0041] Exemplarily, as shown in Figure 4 , Figure 5 , Figure 6 and Figure 7 , wherein, Figure 6 is a state diagram of the magnesium alloy pipe being extruded in the die gap by the second extrusion ring to the direction of the first extrusion ring, Figure 7 is a state diagram of the magnesium alloy pipe being extruded in the die gap by the first extrusion ring to the direction of the second extrusion ring. The left fixed circular die 31 is a circular straight pipe, and the aspect ratio can be [A1] 3. The necking concave die 32 is a straight pipe with a polygonal inner wall. For example, the necking concave die 32 can be a straight pipe with a regular hexagonal inner wall. The regular hexagon formed by the cross section of the necking concave die 32 is inscribed in the circle formed by the cross section of the left fixed circular die 31, and the inner wall of the necking concave die 32 is smoothly connected with the inner wall of the left fixed circular die 31 at the connection end.

[0042] The left fixed extrusion inner die 41 is a circular rod arranged in the left fixed circular die 31. It can be understood that the left fixed extrusion inner die 41 is coaxial with the left fixed circular die 31, and a first gap H I is formed between the outer wall of the left fixed extrusion inner die 41 and the inner wall of the left fixed circular die 31. The polygonal extrusion inner die 42 is a polygonal straight rod fixedly connected with the left fixed extrusion inner die 41. For example, the polygonal extrusion inner die 42 can be a regular hexagonal straight rod. The polygonal extrusion inner die 42 is arranged in the necking die 32, and the regular hexagon formed by the cross section of the polygonal extrusion inner die 42 is inscribed in the circle formed by the cross section of the left fixed extrusion inner die 41. Moreover, the outer wall of the polygonal extrusion inner die 42 is smoothly connected with the outer wall of the left fixed extrusion inner die 41 at the connection end of the polygonal extrusion inner die 42 and the left fixed extrusion inner die 41. The polygonal extrusion inner die 42 is coaxial with the necking die 32, and a second gap H II is formed between the outer wall of the polygonal extrusion inner die 42 and the inner wall of the necking die 32. The width of the first gap H I is the same as that of the second gap H II.

[0043] The magnesium alloy pipe 7 sequentially passes through the left fixed circular die 31 and the necking die 32, and the first extrusion ring 11 extrudes the magnesium alloy pipe 7. Meanwhile, the extrusion outer die 3 and the extrusion inner die 4 rotate. Under the action of friction, the magnesium alloy pipe 7 generates rotational torsional deformation and shearing deformation, thereby effectively refining the crystal grains of the magnesium alloy pipe 7.

[0044] The transition circular die 33 is a circular straight pipe with the same inner diameter as the left fixed circular die 31. Therefore, the polygon formed by the cross section of the necking die 32 is inscribed in the circle formed by the cross section of the transition circular die 33, and the inner wall of the necking die 32 is smoothly connected with the inner wall of the transition circular die 33. The polygonal extrusion inner die 42 is a straight rod with the same diameter as the left fixed extrusion inner die 41. Therefore, the polygon formed by the cross section of the polygonal extrusion inner die 42 is inscribed in the circle formed by the cross section of the transition extrusion inner die 43, and the outer wall of the polygonal extrusion inner die 42 is smoothly connected with the outer wall of the transition extrusion inner die 43.

[0045] The magnesium alloy pipe 7 enters the transition circular die 33 from the necking die 32, and the magnesium alloy pipe 7 restores to a circular pipe structure, thereby preparing for the pipe diameter reduction in the next step.

[0046] The magnesium alloy pipe 7 enters the flaring convex die 34 from the transition circular die 33. The inner diameter of the flaring convex die 34 gradually increases from one end to the other end. The flaring extrusion inner die 44 located in the flaring convex die 34 is also a tapered rod structure with the diameter gradually increasing from one end to the other end. The pipe diameter of the magnesium alloy pipe 7 is enlarged, and the magnesium alloy pipe 7 is subjected to tensile deformation and torsional deformation in the radial direction.

[0047] The right fixed circular die 35 is a circular straight pipe, and the right fixed circular die 35 is communicated with the other end of the flaring punch 34, that is, the inner diameter of the right fixed circular die 35 is coaxially fixedly arranged with the inner diameter of the other end of the flaring punch 34. The right fixed extrusion inner die 45 is arranged in the right fixed circular die 35, and the diameter of the right fixed extrusion inner die 45 is coaxially fixedly connected with the diameter of the other end of the extrusion inner die 4, wherein the third gap HIII is arranged between the right fixed extrusion inner die 45 and the right fixed circular die 35. One end of the second extrusion ring 21 is inserted into the third gap HIII, and the second extrusion ring 21 reciprocally moves along the first direction X to extrude the magnesium alloy pipe 7 between the extrusion inner die 4 and the extrusion outer die 3. The first extrusion ring 11 and the second extrusion ring 21 reciprocally advance in this way, so that the magnesium alloy pipe 7 reciprocally moves in the necking concave die 32, the transition circular die 33 and the flaring punch 34, and the crystal grains of the magnesium alloy pipe are further refined.

[0048] In some embodiments, the flaring extrusion inner die 44 comprises a plurality of circular truncated cones 441 arranged along the first direction X. The circular truncated cone 441 comprises a first end face and a second end face, the diameter of the first end face is smaller than the diameter of the second end face, and the diameters of the first end faces and the second end faces of the adjacent two circular truncated cones 441 are the same. There is an included angle between the center straight line passing through the center points of the first end face and the second end face of the circular truncated cone 441 and the first direction X, and the center straight lines of the adjacent two circular truncated cones 441 are not collinear.

[0049] Preferably, a flaring extrusion transition die 442 is arranged between the adjacent two circular truncated cones 441, the flaring extrusion transition die 442 is a cylindrical structure, the diameter of the end face of the flaring extrusion transition die 442 is the same as the diameter of the first end face or the second end face of the adjacent circular truncated cone 441, and one end face of the flaring extrusion transition die 442 is overlapped and fixedly connected with the first end face of the adjacent circular truncated cone 441, and the other end face of the flaring extrusion transition die 442 is overlapped and fixedly connected with the second end face of the other adjacent circular truncated cone 441.

[0050] The structure of the flaring extrusion inner die 44 can cause the magnesium alloy pipe to be extruded and deformed in the process of the magnesium alloy pipe being offset and rotated relative to the second gap HII, so that the crystal grains of the magnesium alloy pipe are refined.

[0051] In some embodiments, as Figure 2 and Figure 3As shown, the reciprocating radial extrusion device for preparing fine-grained magnesium alloy pipe further comprises a support, and each end of the extrusion outer die 3 is connected to a corresponding support through a bearing. The first power mechanism 1 further comprises a first rack 13, a first gear 14, a gear steering box 15, a second gear 16, and a third gear 17. The first rack 13 is fixedly connected to the first extrusion ring 11, and the first rack 13 has a tendency to reciprocate in the first direction X along with the first extrusion ring 11. The first gear 14 is engaged with the first rack 13, and the input end of the gear steering box 15 is fixedly connected to the first gear 14 coaxially. The second gear 16 is fixedly connected to the output end of the gear steering box 15 coaxially, and the third gear 17 is fixedly connected to the extrusion outer die 3 coaxially. The second gear 16 is engaged with the third gear 17.

[0052] In some embodiments, as Figure 2 As shown, each end of the extrusion inner die 4 is connected to a corresponding support through a bearing. The second power mechanism 2 comprises a threaded rod 23 and a rotating member 24. The threaded rod 23 is fixedly connected to the second extrusion ring 21 coaxially, and the threaded rod 23 is a straight rod as a whole. At least one thread groove or thread protrusion is arranged on the surface of the threaded rod 23 along the axial direction. The rotating member 24 is an annular member as a whole, and a protrusion corresponding to the thread groove is arranged on the inner side wall of the rotating member 24, or a groove corresponding to the thread protrusion is arranged on the inner side wall of the rotating member 24. The rotating member 24 is fixedly connected to the extrusion inner die 4 coaxially. When the threaded rod 23 runs linearly, it has a tendency to drive the rotating member 24 to rotate around the center line thereof.

[0053] It should be noted that a heating jacket 6 is further arranged on the outer wall of the extrusion outer die 3. The heating jacket 6 can be a heating rod or a heating resistance wire fixed on the outer wall of the extrusion outer die 3, and an insulating and heat-preserving layer can be arranged outside the heating jacket 6. The heating jacket 6 facilitates heating operation during magnesium alloy pipe processing.

[0054] On the other hand, the present application also provides a method for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion, which is suitable for the reciprocating radial extrusion device according to any one of the above embodiments.

[0055] The method for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion comprises the following steps:

[0056] S1, pretreating the magnesium alloy pipe to keep the surface of the magnesium alloy pipe smooth.

[0057] S2, preheating the magnesium alloy pipe.

[0058] S3, repeatedly extruding the magnesium alloy pipe along its axial direction, and repeatedly extruding and expanding the magnesium alloy pipe along its radial direction, while extruding and twisting the pipe wall of the magnesium alloy pipe.

[0059] In some examples, the method for pre-treating the magnesium alloy pipe comprises the following steps:

[0060] S11, machining the magnesium alloy pipe into a magnesium alloy pipe with an outer diameter D (20-40 mm) and a wall thickness t (1-5 mm), and polishing the surface of the magnesium alloy pipe with 600 mesh sandpaper to remove oil stains, and then polishing with 800 mesh, 1000 mesh and 1200 mesh sandpaper in sequence until the surface of the magnesium alloy pipe is smooth.

[0061] S12, mixing acetone and anhydrous ethanol in a volume ratio of 3:2 in a cleaning tank, and stirring uniformly to prepare a cleaning solution.

[0062] S1-3, immersing the magnesium alloy pipe prepared in step S11 into the cleaning solution prepared in step S12, placing the cleaning tank on an ultrasonic cleaner to ultrasonically clean the magnesium alloy pipe for 30-60 min, then taking out the magnesium alloy pipe and cleaning with anhydrous ethanol, and finally blowing dry with a hair dryer.

[0063] S14, smearing the surface of the magnesium alloy pipe prepared in step S13 with a graphite oil solution for later use.

[0064] In some examples, the method for preheating the magnesium alloy pipe comprises setting the heating temperature of the vacuum atmosphere heating furnace to 300-500℃, placing the magnesium alloy pipe in the heating furnace after the furnace temperature reaches the set temperature, and holding for 2-4 h.

[0065] In some examples, the method for machining the magnesium alloy pipe using the device for preparing fine-grained magnesium alloy pipe by the above-mentioned complex radial extrusion comprises the following steps:

[0066] S31, lubrication: smearing graphite oil solution on the surfaces of the first and second extrusion rings, all gear meshing parts, the surface of the rotating shaft, the surface of the extrusion inner die, and the inner surface of the extrusion outer die.

[0067] S32, preheating: starting the operation of the heating jacket, controlling the temperature of the heating jacket to 300-500℃, holding for 2-4 h after reaching the set temperature, and leaving for later use.

[0068] S33, the first extrusion ring is withdrawn from the first gap, the magnesium alloy pipe is filled in the first gap, and then the first extrusion ring is pushed into the first gap again. The first extrusion ring extrudes the magnesium alloy pipe, forcing the magnesium alloy pipe into the second gap. At the same time, the outer extrusion die rotates as the first extrusion ring moves, and the magnesium alloy pipe produces shear deformation, torsional deformation and extrusion deformation in the second gap. As the first extrusion ring continues to extrude the magnesium alloy pipe, the magnesium alloy pipe enters the third gap, and the diameter of the magnesium alloy pipe is expanded, causing large plastic deformation of the magnesium alloy pipe. The flaring punch is a radially asymmetric conical body with a circular center offset, so that when the magnesium alloy pipe is flared, the inner wall of the magnesium alloy pipe flows asymmetrically in the radial direction, and the thickness of the pipe is not uniform in the radial direction during flaring. The asymmetric deformation caused by the radial asymmetric flow of the metal belongs to shear deformation, which refines the grains while making the c-axis of the grains deflect along the extrusion direction, further changing the strong basal plane texture orientation along the shear direction to weak basal plane texture, achieving texture weakening of the magnesium alloy pipe. At the same time, the outer extrusion die rotates to drive the magnesium alloy pipe in the second gap to rotate, i.e. the magnesium alloy pipe at the beginning of the flaring punch is twisted, and the magnesium alloy pipe in the middle region of the third gap does not twist due to the thin wall thickness and the softening effect of heating, so that the magnesium alloy pipe produces different radial asymmetric flow and deformation during each flaring, further causing the magnesium alloy pipe to produce different shear asymmetric deformation in the radial direction during each flaring, further making the overall shear deformation of the magnesium alloy pipe more comprehensive and uniform; when the first extrusion ring moves to the other end of the first gap, the flaring of the magnesium alloy pipe is completed, and the diameter of the magnesium alloy pipe is doubled and the wall thickness is halved;

[0069] S34, the position of the first extrusion ring after flaring is kept unchanged, the second extrusion ring is controlled to move towards the third gap, the cavity formed between the flaring punch and the necking recess is a necking cavity, and the second extrusion ring moves until the magnesium alloy pipe is extruded to fill the necking cavity. This process causes large plastic deformation of the magnesium alloy pipe, which refines the magnesium alloy grains; the outer side wall of the necking cavity is the inner wall of the necking recess, the inner side wall of the necking cavity is the outer wall of the flaring punch, and the flaring punch is an asymmetric cone, i.e. the necking cavity is also a radially asymmetric structure. During the necking process, the magnesium alloy pipe also flows radially asymmetrically in the necking cavity, so that the thickness of the magnesium alloy pipe is not uniform in the radial direction. The asymmetric deformation caused by the radial asymmetric flow of the magnesium alloy pipe belongs to shear deformation, which refines the grains while making the c-axis of the grains deflect along the extrusion direction, further changing the strong basal plane texture orientation along the shear direction to weak basal plane texture, achieving texture weakening of the magnesium alloy pipe. At the same time, the inner extrusion die rotates as the second extrusion ring moves, causing the magnesium alloy pipe to produce different radial asymmetric flow and deformation during each necking, i.e. the magnesium alloy pipe produces different shear asymmetric deformation in the radial direction, making the shear deformation of the entire magnesium alloy pipe during necking more comprehensive and uniform.

[0070] It can be understood that the rotation direction of the extrusion inner die is different from that of the pressurized outer die, so when the second extrusion ring runs towards the third gap, the first extrusion ring can be driven to run away from the first gap, and vice versa.

[0071] S35, the first extrusion ring and the second extrusion ring are controlled to reciprocate as described above in step S34, so that the grains of each section of the magnesium alloy pipe are refined; when the reciprocating motion is performed n times (n≥20 times) and the magnesium alloy pipe is in the initial position, the stop button is pressed, and the reciprocating radial extrusion flaring and necking shearing deformation of the magnesium alloy pipe is completed.

[0072] S36, the magnesium alloy pipe prepared in step S35 is taken out, the surface thereof is polished with sandpaper, then the magnesium alloy pipe is cleaned with the cleaning solution prepared in step S12, finally the magnesium alloy pipe is cleaned twice with anhydrous ethanol, and dried with a hair dryer, so that a fine-grained and weak-textured magnesium alloy pipe which can be directly used is prepared.

[0073] 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.

[0074] 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 the preparation of fine-grained magnesium alloy pipes by reciprocating radial extrusion, characterized in that The utility model relates to a kind of extrusion die sets, comprising: First power mechanism, at least including first extrusion ring, the first extrusion ring has the tendency of reciprocating in first direction; Second power mechanism, at least including second extrusion ring, the center line of the second extrusion ring is collinear with the center line of the first extrusion ring, the second extrusion ring has the tendency of reciprocating in first direction; Extrusion outer die is arranged between the first extrusion ring and the second extrusion ring, and the extrusion outer die at least includes through hole arranged along first direction, the center line of the through hole is collinear with the center line of the first extrusion ring or the center line of the second extrusion ring, the extrusion outer die is connected with the first power mechanism, and the first power mechanism has the tendency of driving the extrusion outer die to rotate around its center line when the first extrusion ring operates; Extrusion inner die is arranged in the through hole, and the extrusion inner die is arranged with molding gap between inner wall of the through hole, the extrusion inner die is connected with the second power mechanism, and the second power mechanism has the tendency of driving the extrusion inner die to rotate around its center line when the second extrusion ring operates; The extrusion outer die includes in order from one end close to the first extrusion ring to the other end: Left fixed circular die, straight pipe with circular cross section; Contraction recess, straight pipe with polygonal cross section, and one end of the contraction recess communicates with the left fixed circular die, and the polygon formed by the orthogonal projection of the contraction recess on the end face of the left fixed circular die is inscribed in the circle of the end face of the left fixed circular die; Transition circular die, straight pipe with circular cross section, the transition circular die communicates with the other end of the contraction recess; Flaring punch, variable diameter pipe with increasing diameter from one end to the other end, one end of the flaring punch communicates with the transition circular die; Right fixed circular die, straight pipe with circular cross section, the right fixed circular die communicates with the other end of the flaring punch; The extrusion inner die includes in order from one end close to the first extrusion ring to the other end: Left fixed extrusion inner die, straight rod with circular cross section, arranged in the left fixed circular die, and the shortest distance between the outer wall of the left fixed extrusion inner die and the inner wall of the left fixed circular die is equal; Polygonal extrusion inner die, straight rod with polygonal cross section adapted to the inner wall of the contraction recess, arranged in the contraction recess, the polygonal extrusion inner die is coaxially fixedly connected with the left fixed extrusion inner die, and the polygon formed by the orthogonal projection of the polygonal extrusion inner die on the end face of the left fixed extrusion inner die is inscribed in the circle of the end face of the left fixed extrusion inner die; Transition extrusion inner die, straight rod with circular cross section, arranged in the transition circular die, the transition extrusion inner die is coaxially fixedly connected with the polygonal extrusion inner die; Flaring extrusion inner die, generally in the structure of circular truncated cone, arranged in the flaring punch, the diameter of the flaring extrusion inner die increases from one end to the other end, and one end of the flaring extrusion inner die is coaxially fixedly connected with the transition extrusion inner die. The right fixed extrusion inner mold is a straight rod with a circular cross section, which is arranged in the right fixed circular mold, and the right fixed extrusion inner mold is coaxially fixedly connected with the other end of the flared extrusion inner mold; The flared extrusion inner mold comprises a plurality of circular truncated cones arranged along a first direction; The circular truncated cone comprises a first end face and a second end face, the diameter of the first end face is smaller than the diameter of the second end face, and the diameters of the first end faces and the second end faces of the adjacent two circular truncated cones are the same; There is an included angle between the center straight line passing through the center points of the first end face and the second end face of the circular truncated cone and the first direction, and the center straight lines of the adjacent two circular truncated cones are not collinear.

2. The apparatus for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion according to claim 1, characterized by The device for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion further comprises a support, and the two ends of the extrusion outer mold are connected with corresponding supports through bearings respectively; The first power mechanism further comprises: A first rack is fixedly connected with the first extrusion ring, and the first rack has a tendency to reciprocate in the first direction along with the first extrusion ring; A first gear is engaged with the first rack; A gear steering box is coaxially fixedly connected with the first gear at the input end; A second gear is coaxially fixedly connected with the output end of the gear steering box; A third gear is coaxially fixedly connected with the extrusion outer mold, and the second gear is engaged with the third gear.

3. The apparatus for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion according to claim 1, characterized by The two ends of the extrusion inner mold are connected with corresponding supports through bearings respectively; The second power mechanism comprises a threaded rod coaxially fixedly connected with the second extrusion ring, the threaded rod is a straight rod as a whole, and at least one thread groove or thread protrusion extending along the axial direction of the threaded rod is arranged on the surface of the threaded rod; A rotating member is an annular member as a whole, a protrusion corresponding to the thread groove is arranged on the inner side wall of the rotating member, or a groove corresponding to the thread protrusion is arranged on the inner side wall of the rotating member, and the rotating member is coaxially fixedly connected with the extrusion inner mold; When the threaded rod runs linearly, it has a tendency to drive the rotating member to rotate around the center line thereof.

4. The apparatus for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion according to claim 1, wherein A flared extrusion transition mold is arranged between the adjacent two circular truncated cones, the flared extrusion transition mold has a cylindrical structure, the diameter of the end face of the flared extrusion transition mold is the same as that of the first end face or the second end face of the adjacent circular truncated cone, one end face of the flared extrusion transition mold overlaps and is fixedly connected with the first end face of the adjacent circular truncated cone, and the other end face of the flared extrusion transition mold overlaps and is fixedly connected with the second end face of the other adjacent circular truncated cone.

5. The apparatus for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion according to claim 1, wherein The first power mechanism comprises a first telescopic machine, the piston of the first telescopic machine is fixedly connected with the first extrusion ring, the first extrusion ring has a tubular structure, at least part of the structure of the first extrusion ring is arranged in the extrusion outer mold, and the first extrusion ring is sleeved on the extrusion inner mold.

6. The apparatus for preparing a fine-grained magnesium alloy pipe by reciprocating radial extrusion according to claim 1, wherein The second power mechanism comprises a second telescopic machine, the piston of the second telescopic machine is fixedly connected with the second extrusion ring, the second extrusion ring has a tubular structure, at least part of the structure of the second extrusion ring is arranged in the extrusion outer mold, and the second extrusion ring is sleeved on the extrusion inner mold.

7. A method of producing a fine-grained magnesium alloy pipe by reciprocating radial extrusion, which is suitable for the device for producing a fine-grained magnesium alloy pipe by reciprocating radial extrusion according to any one of claims 1 to 6, characterized in that, The method for preparing fine-grained magnesium alloy pipe by reciprocating radial extrusion comprises the following steps: pretreating the magnesium alloy pipe to keep the surface of the magnesium alloy pipe smooth; preheating the magnesium alloy pipe; repeatedly extruding the magnesium alloy pipe along its axial direction; and repeatedly extruding and expanding the magnesium alloy pipe along its radial direction, while extruding and twisting the pipe wall of the magnesium alloy pipe.

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