A device and method for preparing weak texture fine-grained magnesium alloy rod

Abstract

The invention belongs to the technical field of magnesium alloy plastic forming, and specifically relates to a device and method for preparing a weak texture fine-grained magnesium alloy rod; the device comprises a punch, an extrusion die, and a twisting die, the punch is installed on the action end of a vertical sliding mechanism, the twisting die is connected to a torque input mechanism, and rotates synchronously with the downward movement of the punch; a variable-section curved channel is arranged in the extrusion die, and a twisting variable-section channel is arranged in the twisting die; the variable-section curved channel comprises an entrance channel, a first extrusion channel, a transition channel of equal diameter, and a second extrusion channel from top to bottom in sequence; the transition channel comprises a first transition channel, a second transition channel, and a third transition channel connected at a corner; a plurality of spherical convex hulls are distributed above and below in the twisting variable-section channel; the magnesium alloy billet undergoes multiple variable-section twistings in the variable-section curved channel and the twisting variable-section channel, a large amount of shear torsional deformation is introduced in the deformation process, and the grain size is greatly reduced compared with the magnesium alloy before extrusion.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy plastic forming, and specifically relates to a device and a process method for preparing weak-textured fine-grained magnesium alloy rods by shear-torsion composite extrusion deformation. Background Art

[0002] As the metal structural material with the lowest density, magnesium alloy has important application value in the fields of automobile, electronics, aerospace, military, etc. due to its advantages such as high specific strength and specific stiffness, excellent electromagnetic shielding performance, no sparking during friction, good machinability and hot forming properties, and easy recycling. It is known as the "green energy material of the 21st century". However, due to its close-packed hexagonal crystal structure, magnesium alloy has only two independent slip systems at room temperature, which cannot meet the Von-Mises criterion required for plastic deformation. The macroscopic manifestation is that it is difficult to deform and has poor mechanical 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. For example, rolling or extrusion will form a typical basal texture. The texture will cause anisotropy and tension-compression asymmetry in magnesium alloy, which will limit the application of magnesium alloy in various fields.

[0003] Severe plastic deformation can effectively refine grains and improve the mechanical properties of magnesium alloys. For example, high-strength and high-plasticity magnesium alloy materials can be obtained through equal channel angular pressing (ECAP), high pressure torsion (HPT), and reciprocating extrusion. However, the actual operation is complicated and difficult to achieve continuity. The sample size is small and it is difficult to achieve industrial production. Therefore, it is urgent to invent a continuous large-scale processing deformation process and method to prepare weak texture fine-grained high-performance magnesium alloys and expand their application range. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for preparing weakly textured fine-grained magnesium alloy bars by shear-torsion composite extrusion deformation. The device continuously introduces shear deformation at different angles and simultaneously introduces torsional deformation by extrusion downward transmission, so as to achieve the purpose of refining grains, weakening basal surface texture and preparing high-performance magnesium alloys.

[0005] The present invention provides the following technical solution: a device for preparing a weakly textured fine-grained magnesium alloy bar, comprising a punch, an extrusion die, and a twisting die, wherein the punch is mounted on the action end of a vertical sliding mechanism, and the twisting die is connected to a torque input mechanism and rotates synchronously with the downward movement of the punch;

[0006] A variable-section curved channel is provided in the extrusion die, and a torsion variable-section channel is provided in the torsion die;

[0007] The variable cross-section curved channel includes an inlet channel, a first extrusion channel, a transition channel of equal diameter, and a second extrusion channel from top to bottom; the inlet channel is a cylindrical cavity adapted to the punch; the inlet side and the outlet side of the first extrusion channel shrink toward the middle to form a narrow throat, and both ends of the second extrusion channel shrink toward the middle to form a narrow throat; the transition channel includes the first transition channel, the second transition channel, and the third transition channel connected at a corner, the first transition channel, the second transition channel, and the third transition channel are connected to each other through an elbow channel, the first transition channel is connected to the first extrusion channel through an elbow channel, and the third transition channel is connected to the second extrusion channel through an elbow channel;

[0008] The second extrusion channel directly leads to the torsion variable cross-section channel, and a discharge port is arranged below the torsion variable cross-section channel; and a plurality of spherical convex hulls are distributed above and below in the torsion variable cross-section channel.

[0009] Furthermore, the angle between the surface where the third transition channel 17.5 is located and the surface where the first transition channel is located is α, and the angle range of α is 0°~90°.

[0010] Further, the radius of the elbow channel between the first transition channel and the first extrusion channel is r2, the radius of the elbow channel between the third transition channel and the second extrusion channel is r4, and the radius of the elbow channel between the first transition channel and the second transition channel and between the second transition channel and the third transition channel is r3, r3<r2, r3<r4;

[0011] There are two spherical convex hulls distributed in the torsional variable cross-section channel, and the radius r6 of the upper spherical convex hull I is greater than the radius r7 of the lower spherical convex hull II.

[0012] Furthermore, the inner arc surface with a radius of r1 in the first extrusion channel forms a narrow throat; the second extrusion channel is surrounded by an inner arc surface with a radius of r5.

[0013] Furthermore, it includes a working platform and a top plate. The working platform is provided with guide columns. The top plate is slidably guided and assembled on the guide columns. The punch is vertically downwardly mounted on the punch fixing plate on the bottom surface of the top plate. The torsion die is rotatably assembled on the working platform. A discharge port is arranged on the working platform. The extrusion die is suspended above the torsion die by a bracket. The bottom surface of the extrusion die floats and fits with the top surface of the torsion die.

[0014] Furthermore, the torsion die is installed on a rotating support on the working platform, and the channel in the center of the rotating support connects the torsion variable cross-section channel and the discharge port; the outer ring of the torsion die is provided with a gear ring, and the seat body of the rotating support is provided with a fixed block, and the fixed block is provided with a slideway tangent to the gear ring of the torsion die; it also includes a rack, a reaction block, a downward push rod, and a support rod. The rack penetrates into the slideway and meshes with the gear ring. A first inclined surface is provided at the end of the rack exposed outside the slideway, and a second inclined surface in the opposite direction is provided on the side of the reaction block facing the rack. The downward push rod is fixed under the punch fixing plate, and the support rod is perpendicular to the downward push rod and is arranged at the bottom end of the downward push rod. In the downward stage of the downward push rod, one end of the support rod uses the second inclined surface as a reaction force support, and the other end abuts against the first inclined surface to push the rack, and a reset spring is connected between the rack and the reaction block.

[0015] Furthermore, the extrusion die and the twisting die are covered with a heating jacket, which includes two groups of heat sources. The first group of heat sources is located in the extrusion die area, and the second group of heat sources is located in the twisting die area. The two groups of heat sources form two temperature zones at the positions of the extrusion die and the twisting die.

[0016] Furthermore, a roller is installed at each end of the support rod.

[0017] The present invention also provides a method for preparing a weakly textured fine-grained magnesium alloy rod, using the aforementioned device for preparing a weakly textured fine-grained magnesium alloy rod, comprising the following steps:

[0018] S1: Pretreatment of magnesium alloy billet, grinding, cleaning, lubrication and preheating;

[0019] S2: Install the device on the vertical extruder, connect the top plate to the oil cylinder of the vertical extruder; lubricate and preheat the extrusion die and the twisting die;

[0020] S3: Shearing and twisting extrusion forming: the magnesium alloy billets prepared in step S1 are placed in the inlet channel and pressed down one by one by the punch.

[0021] Furthermore, in step S1, the magnesium alloy billet pretreatment includes:

[0022] S1-1. Grind the surface of the magnesium alloy blank with 600-mesh sandpaper to remove oil stains, and then grind with 800-mesh, 1000-mesh, and 1200-mesh sandpaper in sequence;

[0023] S1-2, mixing acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stirring evenly to prepare a cleaning solution; immersing the magnesium alloy blank prepared in step S1-1 in the cleaning solution, placing the cleaning tank on an ultrasonic cleaning machine to ultrasonically clean the magnesium alloy blank for 40 minutes, then taking out the magnesium alloy blank and cleaning it with anhydrous ethanol, and finally drying it with a hair dryer;

[0024] S1-3, applying a graphite oil solution to the surface of the magnesium alloy blank prepared in step S1-2;

[0025] S1-4, start the heating furnace and set the heating temperature of the heating furnace to 450° C. After the temperature of the heating furnace reaches the set temperature, put the magnesium alloy billet prepared in step S1-2 into the heating furnace and keep it warm for 3 hours;

[0026] Step S2 specifically includes the following steps:

[0027] S2-1, applying graphite oil solution on the first inclined surface of the rack, the second inclined surface of the reaction block, the contact surface between the rack and the fixed block, the variable cross-section curved channel and the torsional variable cross-section channel;

[0028] S2-2, connect the top plate to the oil cylinder of the vertical extruder through bolts;

[0029] S2-3, set the temperature of the first heat source of the heating jacket to 450°C and the temperature of the second heat source to 300°C, and keep the temperature for 3 hours after reaching the set temperature;

[0030] Step S3 specifically includes the following steps:

[0031] S3-1, control the oil cylinder of the vertical extruder to withdraw the punch, put the magnesium alloy billet into the inlet channel, keep it warm for 1 hour, control the punch to move downward for extrusion, and the extrusion speed is 50mm / min. During the extrusion process, control the temperature of the first heat source of the heating jacket to 450℃ and the temperature of the second heat source to 300℃;

[0032] S3-2, after the extrusion of the first magnesium alloy billet is completed, the punch is withdrawn and the next magnesium alloy billet is placed, and step S3-1 is repeated to place the third billet, the fourth billet, ... the nth billet, and the magnesium alloy billet passes through the variable cross-section bending channel and the torsional variable cross-section channel and is extruded from the discharge port to obtain a weak texture fine-grained magnesium alloy rod;

[0033] S3-3. Take out the weakly textured fine-grained magnesium alloy rod obtained in step S3-2, polish its surface with sandpaper, then clean it with the cleaning solution prepared in step S1-2, and finally clean it twice with anhydrous ethanol and blow dry to obtain a finished weakly textured fine-grained magnesium alloy rod.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] The magnesium alloy billet undergoes multiple variable-section torsions in the variable-section bending channel and the torsional variable-section channel. The deformation process introduces a large amount of shear torsional deformation, and the grain size is greatly reduced compared with the magnesium alloy before extrusion.

[0036] During the extrusion process, the magnesium alloy billet enters from the entrance channel, and the channel cross-section becomes narrower at the arc surface in the first extrusion channel, where shear deformation occurs and the grain size becomes smaller. At the connection between the elbow channel of the first extrusion channel and the first transition channel, the channel cross-section becomes larger, but because the extrusion direction of the billet changes at the elbow channel, the deformation introduces a large amount of shear deformation, the grains are refined, the c-axis is deflected, and the texture is weakened.

[0037] The magnesium alloy billet is extruded into the transition channel. The junctions of the I, II and III transition channels are elbow channels with a radius of r3, where r3 < r2. Similarly, the deformation of the magnesium alloy billet at the elbow channel introduces a large amount of shear deformation, the grain size becomes smaller, the c-axis continues to deflect, and the texture weakens.

[0038] The magnesium alloy billet enters the second extrusion channel. The junction of the second extrusion channel and the third transition channel is an elbow channel with a radius of r4, r4>r3. At this time, the cross-section becomes larger, and the extrusion direction of the billet changes at the elbow channel, introducing a large amount of shear deformation. The channel cross-section of the billet becomes narrower at the arc surface in the second extrusion channel and shear deformation occurs, which further refines the grains, continues to deflect the c-axis, and weakens the texture.

[0039] The magnesium alloy billet enters the torsional variable cross-section channel and is affected by two asymmetric arc surfaces with radii r6 and r7, where r6>r7. At the same time, the torsional die rotates clockwise, causing the magnesium alloy billet to undergo torsional deformation in the torsional variable cross-section channel, further refining the grains, continuing to deflect the c-axis, and weakening the texture.

[0040] The heating temperature of the extrusion die is 350-450°C, and the heating temperature of the torsion die is 250-350°C. This results in a temperature gradient inside the magnesium alloy billet during the extrusion process, which makes its internal plasticity uneven. Specifically, the plasticity of the part close to the extrusion die is better than that of the part close to the torsion die. This makes the flow rate of the magnesium alloy billet in the variable-section curved channel greater than the flow rate in the torsion variable-section channel, and once again forces the magnesium alloy billet grain c-axis to deflect in addition to the mechanical transmission, extrusion channel shape, and size parameters, thereby weakening the basal texture and refining the grains. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the structure of the device for preparing weakly textured fine-grained magnesium alloy rods.

[0042] Figure 2 It is a schematic diagram of the coordination of the rack, the torsion die and the fixed block.

[0043] Figure 3 It is a structural schematic diagram of a variable cross-section curved channel.

[0044] Figure 4This is a structural schematic diagram of a variable-section curved channel (with dimension parameters marked).

[0045] Figure 5 It is a schematic diagram of the structure of the variable cross-section curved channel (the angle between the third transition channel and the first transition channel is shown).

[0046] Figure 6 It is a structural schematic diagram of the torsional variable cross-section channel.

[0047] Figure 7 This is the deformation state diagram of the blank when α=20°.

[0048] Figure 8 This is the deformation state diagram of the blank when α=60°.

[0049] In the figure: 1-top plate; 2-punch fixing plate; 3-downward push rod; 4-guide column; 5-reaction block; 6-working platform; 7-support rod; 8-rack; 9-fixed block; 10-extrusion die; 11-torsion die; 12-discharging port; 13-rotating support; 14-punch; 15-heating sleeve; 16-bracket; 17-variable cross-section bending channel; 17.1-entrance channel; 17.2-first extrusion channel; 17.3-first transition channel; 17.4-second transition channel; 17.5-third transition channel; 17.6-second extrusion channel; 18-torsion variable cross-section channel; 18.1-first spherical convex hull; 18.2-second spherical convex hull. DETAILED DESCRIPTION

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Example 1

[0052] like Figure 1 , Figure 2As shown: This embodiment provides a device for preparing a weak texture fine-grained magnesium alloy bar, comprising a punch 14, an extrusion die 10, a twisting die 11, a working platform 6, and a top plate 1. The punch 14, the extrusion die 10, and the twisting die 11 are all made of 4Cr5MoSiV1 hot-working die steel. A variable-section curved channel 17 is provided in the extrusion die 10, and a twisting variable-section channel 18 is provided in the twisting die 11. A guide column 4 is erected on the working platform 6, and the top plate 1 can be slidably guided and assembled on the guide column 4. The punch 14 is vertically downwardly mounted on the punch fixing plate 2 on the bottom surface of the top plate 1; the twisting die 11 is mounted on a rotating support 13 on the working platform 6, and a discharge port 12 is provided on the working platform 6. The channel in the center of the rotating support 13 connects the twisting variable-section channel 18 and the discharge port 12. The extrusion die 10 is suspended above the twisting die 11 through a bracket 16, and the bottom surface of the extrusion die 10 floats and fits with the top surface of the twisting die 11. The outer ring of the torsion die 11 is provided with a gear ring, and the seat body of the rotating support 13 is provided with a fixed block 9, and the fixed block 9 is provided with a slideway tangent to the gear ring of the torsion die 11. It also includes a rack 8, a reaction block 5, a downward push rod 3, and a support rod 7. The rack 8 penetrates the slideway and meshes with the gear ring. The end of the rack 8 exposed outside the slideway is provided with a first inclined surface, and the reaction block 5 is provided with a second inclined surface in the opposite direction on the side facing the rack 8. The downward push rod 3 is fixed under the punch fixing plate 2, and the support rod 7 is perpendicular to the downward push rod 3 and is provided at the bottom end of the downward push rod 3. A roller is installed at each end of the support rod 7. In the downward stage of the downward push rod 3, one end of the support rod 7 uses the second inclined surface as a reaction force support, and the other end abuts against the first inclined surface to push the gear. When the top plate 1 moves downward, it drives the downward push rod 3 to move downward, and the support rod 7 pushes the rack 8 to move with the reaction block 5 as the reaction force support, and the rack 8 is engaged with the toothed ring of the torsion die 11, so that the torsion die 11 rotates clockwise, and a reset spring is connected between the rack 8 and the reaction block 5. When the top plate 1 moves upward, it drives the downward push rod 3 to move upward, and the thrust acting on the rack 8 is released. The reset spring pulls the rack 8 in the reverse direction, and the rack 8 returns to its original position to wait for the next impact of the support rod 7, and at the same time, the torsion die 11 rotates counterclockwise to reset.

[0053] The extrusion die 10 and the torsion die 11 are covered with a heating sleeve 15, which includes two groups of heat sources. The first group of heat sources is located in the extrusion die 10 area, and the second group of heat sources is located in the torsion die 11 area. The heating temperature of the first group of heat sources is 350-450°C, and the heating temperature of the second group of heat sources is 250-350°C. The two groups of heat sources form two temperature zones at the positions of the extrusion die 10 and the torsion die 11. This results in a temperature gradient inside the magnesium alloy billet during the extrusion process, which makes its internal plasticity uneven. Specifically, the plasticity of the part close to the extrusion die is better than that of the part close to the torsion die, which makes the flow velocity of the magnesium alloy billet in the variable cross-section curved channel greater than the flow velocity in the torsion variable cross-section channel, and once again forces the magnesium alloy billet grain c-axis to deflect in addition to the mechanical transmission, extrusion channel shape, and size parameters, thereby weakening the basal texture and refining the grains.

[0054] like Figure 3 As shown: the variable cross-section curved channel 17 includes, from top to bottom, an inlet channel 17.1, a first extrusion channel 17.2, a transition channel of equal diameter, and a second extrusion channel 17.6; the inlet channel 17.1 is a cylindrical cavity adapted to the punch 14; the inlet side and the outlet side of the first extrusion channel 17.2 shrink toward the middle to form a narrow throat, and both ends of the second extrusion channel 17.6 shrink toward the middle to form a narrow throat; the transition channel includes the first transition channel 17.3, the second transition channel 17.4 and the third transition channel 17.5 connected at a corner, the first transition channel 17.3, the second transition channel 17.4 and the third transition channel 17.5 are connected to each other through elbow channels, the first transition channel 17.3 is connected to the first extrusion channel 17.2 through an elbow channel, and the third transition channel 17.5 is connected to the second extrusion channel 17.6 through an elbow channel.

[0055] The first extrusion channel 17.2 is surrounded by an inner arc surface with a radius of r1 to form a narrow throat; the second extrusion channel 17.6 is surrounded by an inner arc surface with a radius of r5.

[0056] The radius of the elbow channel between the first transition channel 17.3 and the first extrusion channel 17.2 is r2, the radius of the elbow channel between the third transition channel 17.5 and the second extrusion channel 17.6 is r4, the radius of the elbow channel between the first transition channel 17.3 and the second transition channel 17.4 and between the second transition channel 17.4 and the third transition channel 17.5 is r3, r3<r2, r3<r4.

[0057] like Figure 6As shown: the second extrusion channel 17.6 directly passes through the torsion variable cross-section channel 18, and a discharge port is arranged below the torsion variable cross-section channel 18; there are several spherical convex hulls distributed above and below in the torsion variable cross-section channel 18. There are two spherical convex hulls distributed above and below in the torsion variable cross-section channel 18, and the radius r6 of the first spherical convex hull 18.1 on the upper part is greater than the radius r7 of the second spherical convex hull 18.2 on the lower part.

[0058] During the extrusion process, the magnesium alloy billet enters from the entrance channel 17.1, and the channel cross-section becomes narrower at the inner arc surface of the first extrusion channel 17.2, and shear deformation occurs, and the grain size becomes smaller; at the elbow channel connection between the first extrusion channel 17.2 and the first transition channel 17.3, the channel cross-section becomes larger, but because the extrusion direction of the billet changes at the elbow channel, the deformation introduces a large amount of shear deformation, the grains are refined, the c-axis is deflected, and the texture is weakened.

[0059] The magnesium alloy billet is extruded into the transition channel. The junctions of the I, II and III transition channels are elbow channels with a radius of r3, where r3 < r2. Similarly, the deformation of the magnesium alloy billet at the elbow channel introduces a large amount of shear deformation, the grain size becomes smaller, the c-axis continues to deflect, and the texture weakens.

[0060] The magnesium alloy billet enters the second extrusion channel 17.6. The junction between the second extrusion channel 17.6 and the third transition channel 17.5 is an elbow channel with a radius of r4, r4>r3. At this time, the cross-section becomes larger, and the extrusion direction of the billet changes at the elbow channel, introducing a large amount of shear deformation. The channel cross-section of the billet becomes narrower at the inner arc surface of the second extrusion channel 17.6, and shear deformation occurs, which further refines the grains, continues to deflect the c-axis, and weakens the texture.

[0061] The magnesium alloy billet enters the torsional variable cross-section channel 18 and is affected by two asymmetric arc surfaces with radii r6 and r7, where r6>r7. At the same time, the torsional die rotates clockwise, causing the magnesium alloy billet to be torsional deformed in the torsional variable cross-section channel 18, further refining the grains, continuing to deflect the c-axis, and weakening the texture.

[0062] During the extrusion of the magnesium alloy billet, in the variable-section bending channel 17, the billet undergoes variable-section extrusion in the first extrusion channel, and undergoes bending deformation at the junction of the first extrusion channel and the first transition channel, the junction of the first transition channel and the second transition channel, and the junction of the second transition channel and the third transition channel, thereby introducing a large amount of shear deformation. In the torsional variable-section channel 18, the magnesium alloy billet undergoes two sections of variable-section and asymmetric extrusion, thereby also introducing a large amount of shear deformation. In addition, various asymmetric variable-section channels can be formed by adjusting the channel section radius parameters r1, r2, r3, r4, r5, r6, and r7, thereby introducing more shear deformation, causing the c-axis of the magnesium alloy billet grains to deflect, thereby weakening the basal texture and refining the grains.

[0063] like Figure 5 As shown, the angle between the surface where the third transition channel 17.5 is located and the surface where the first transition channel 17.3 is located is α, and the angle range of α is 0°~90°.

[0064] The billet is finally formed through the above extrusion. Figure 7 The deformation state of the A1 billet increases with the increase of the billet extrusion speed, and the rotation speed of the twisting die increases synchronously. The billet also introduces more torsional deformation in the twisting variable cross-section channel, forming Figure 7 Deformation state of A2 blank.

[0065] By changing the range of α angle, Figure 8 The deformation state of the A3 billet in the middle, increasing the extrusion speed, introducing more torsional deformation, forming Figure 8 The deformation state of the A4 blank.

[0066] By changing the value of α, different degrees of torsion and shear deformation can be introduced at the junction of the transition channel, causing the c-axis of the magnesium alloy billet grain to deflect, thereby weakening the basal texture and refining the grains.

[0067] The torsional die 11 rotates synchronously with the punch 14 downward. During the extrusion of the billet, the torsional speed of the torsional die 11 changes with the change of the extrusion speed. At the same angle α, the faster the extrusion speed, the faster the torsional speed, ω2>ω1, ω4>ω3, the greater the torsional speed, the greater the torsional deformation introduced, and the c-axis of the grains of the magnesium alloy billet can also be deflected to weaken the basal texture and refine the grains.

[0068] Example 2

[0069] This embodiment provides a method for preparing a weakly textured fine-grained magnesium alloy rod, using the device for preparing a weakly textured fine-grained magnesium alloy rod in Example 1.

[0070] Before preparing weak texture fine-grained magnesium alloy rods by shear-torsion composite extrusion deformation, the materials and chemical reagents required for the preparation process should be carefully selected:

[0071] 1. Magnesium alloy billet, solid round billet, cross-sectional size φ120mm, material selected is AZ31, containing 96% magnesium, 3% aluminum and 1% zinc;

[0072] 2. Sandpaper, solid;

[0073] 3. Graphite oil solution, viscous liquid;

[0074] 4. Anhydrous ethanol, liquid, purity 99.5%;

[0075] 5. Acetone, liquid, purity 99%.

[0076] A method for preparing a weakly textured fine-grained magnesium alloy rod comprises the following steps:

[0077] S1: Pretreatment of magnesium alloy billet, grinding, cleaning, lubrication and preheating;

[0078] S1-1. Grind the surface of the magnesium alloy blank with 600-mesh sandpaper to remove oil stains, and then grind with 800-mesh, 1000-mesh, and 1200-mesh sandpaper in sequence until the surface of the magnesium alloy blank is smooth;

[0079] S1-2, mixing acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stirring evenly to prepare a cleaning solution; immersing the magnesium alloy blank prepared in step S1-1 in the cleaning solution, placing the cleaning tank on an ultrasonic cleaning machine to ultrasonically clean the magnesium alloy blank for 40 minutes, then taking out the magnesium alloy blank and cleaning it with anhydrous ethanol, and finally drying it with a hair dryer;

[0080] S1-3, applying a graphite oil solution to the surface of the magnesium alloy blank prepared in step S1-2;

[0081] S1-4, start the heating furnace and set the heating temperature of the heating furnace to 450° C. After the temperature of the heating furnace reaches the set temperature, put the magnesium alloy billet prepared in step S1-2 into the heating furnace and keep it warm for 3 hours;

[0082] S2: The device is installed on a vertical extruder, and the top plate 1 is connected to the oil cylinder of the vertical extruder; the extrusion die 10 and the twisting die 11 are lubricated and preheated;

[0083] S2-1, apply graphite oil solution on the first inclined surface of the rack 8, the second inclined surface of the reaction block 5, the contact surface between the rack 8 and the fixed block 9, the variable cross-section curved channel 17 and the torsional variable cross-section channel 10;

[0084] S2-2, connect the top plate 1 to the oil cylinder of the vertical extruder through bolts;

[0085] S2-3, set the temperature of the first heat source of the heating jacket 15 to 450°C and the temperature of the second heat source to 300°C, and keep the temperature for 3 hours after reaching the set temperature;

[0086] S3: Shearing and twisting extrusion forming, the magnesium alloy blanks prepared in step S1 are placed in the inlet channel 17.1 and pressed down one by one by the punch 14;

[0087] S3-1, control the oil cylinder of the vertical extruder to withdraw the punch 14, put the magnesium alloy billet into the inlet channel 17.1, keep it warm for 1 hour, control the punch 14 to move downward for extrusion, the extrusion speed is 50mm / min, and during the extrusion process, control the temperature of the first heat source of the heating jacket 15 to 450℃ and the temperature of the second heat source to 300℃;

[0088] S3-2, after the extrusion of the first magnesium alloy billet is completed, the punch 14 is withdrawn and the next magnesium alloy billet is placed, and step S3-1 is repeated to place the third billet, the fourth billet, ... the nth billet, and the magnesium alloy billet passes through the variable cross-section bending channel 17 and the torsional variable cross-section channel 18 and is extruded from the discharge port 12 to obtain a weak texture fine-grained magnesium alloy rod;

[0089] S3-3. Take out the weakly textured fine-grained magnesium alloy rod obtained in step S3-2, polish its surface with sandpaper, then clean it with the cleaning solution prepared in step S1-2, and finally clean it twice with anhydrous ethanol and blow dry to obtain a finished weakly textured fine-grained magnesium alloy rod.

[0090] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for preparing a weakly textured fine-grained magnesium alloy rod, characterized in that: It comprises a punch (14), an extrusion die (10), and a twisting die (11), wherein the punch (14) is mounted on the action end of the vertical sliding mechanism, and the twisting die (11) is connected to the torque input mechanism and rotates synchronously with the downward movement of the punch (14); A variable-section curved channel (17) is provided in the extrusion die (10), and a torsion variable-section channel (18) is provided in the torsion die (11); The variable cross-section curved channel (17) includes, from top to bottom, an inlet channel (17.1), a first extrusion channel (17.2), a transition channel of equal diameter, and a second extrusion channel (17.6); the inlet channel (17.1) is a cylindrical cavity adapted to the punch (14); the inlet side and the outlet side of the first extrusion channel (17.2) shrink toward the middle to form a narrow throat, and both ends of the second extrusion channel (17.6) shrink toward the middle to form a narrow throat; the transition channel includes a corner connection The first transition channel (17.3), the second transition channel (17.4) and the third transition channel (17.5) are connected to each other through elbow channels, the first transition channel (17.3) and the first extrusion channel (17.2) are connected through an elbow channel, and the third transition channel (17.5) and the second extrusion channel (17.6) are connected through an elbow channel; The second extrusion channel (17.6) directly leads to the torsion variable cross-section channel (18), and a discharge port is arranged below the torsion variable cross-section channel (18); a plurality of spherical convex hulls are distributed above and below the torsion variable cross-section channel (18).

2. The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 1, characterized in that: The angle between the surface where the third transition channel (17.5) is located and the surface where the first transition channel (17.3) is located is α, and the angle range of α is 0°~90°.

3. The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 2, characterized in that: The radius of the elbow channel between the first transition channel (17.3) and the first extrusion channel (17.2) is r2, the radius of the elbow channel between the third transition channel (17.5) and the second extrusion channel (17.6) is r4, and the radius of the elbow channel between the first transition channel (17.3) and the second transition channel (17.4) and between the second transition channel (17.4) and the third transition channel (17.5) is r3, r3 < r2, r3 < r4; Two spherical convex hulls are distributed in the torsional variable cross-section channel (18) at the top and the bottom, and the radius r6 of the upper first spherical convex hull (18.1) is greater than the radius r7 of the lower second spherical convex hull (18.2).

4. The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 3, characterized in that: The first extrusion channel (17.2) is surrounded by an inner arc surface with an inner radius of r1 to form a narrow throat; the second extrusion channel (17.6) is surrounded by an inner arc surface with a radius of r5.

5. The device for preparing a weakly textured fine-grained magnesium alloy rod according to any one of claims 1 to 4, characterized in that: The invention comprises a working platform (6) and a top plate (1). A guide column (4) is erected on the working platform (6). The top plate (1) is slidably guided and assembled on the guide column (4). A punch (14) is vertically mounted downward on a punch fixing plate (2) on the bottom surface of the top plate (1). A torsion die (11) is rotatably assembled on the working platform (6). A discharge port (12) is arranged on the working platform (6). An extrusion die (10) is suspended above the torsion die (11) via a bracket (16). The bottom surface of the extrusion die (10) floats and fits with the top surface of the torsion die (11).

6. The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 5, characterized in that: The torsion die (11) is mounted on a rotating support (13) on a working platform (6); a channel at the center of the rotating support (13) is connected to the torsion variable cross-section channel (18) and the discharge port (12); a toothed ring is arranged on the outer ring of the torsion die (11); a fixed block (9) is arranged on the seat body of the rotating support (13); a slideway tangent to the toothed ring of the torsion die (11) is opened on the fixed block (9); and the rack (8), a reaction block (5), a downward push rod (3), and a support rod (7); the rack (8) is inserted into the slideway The rack (8) is meshed with the gear ring, and a first inclined surface is provided at one end of the rack (8) exposed outside the slideway. A second inclined surface in the opposite direction is provided on the side of the reaction block (5) facing the rack (8). The downward push rod (3) is fixed under the punch fixing plate (2). The support rod (7) is perpendicular to the downward push rod (3) and is provided at the bottom end of the downward push rod (3). In the downward stage of the downward push rod (3), one end of the support rod (7) uses the second inclined surface as a reaction force support, and the other end abuts against the first inclined surface to push the rack (8). A reset spring is connected between the rack (8) and the reaction block (5).

7. The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 6, characterized in that: The extrusion die (10) and the twisting die (11) are covered with a heating sleeve (15), and the heating sleeve (15) includes two groups of heat sources, the first group of heat sources is located in the extrusion die (10) area, and the second group of heat sources is located in the twisting die (11) area, and the two groups of heat sources form two temperature zones at the positions of the extrusion die (10) and the twisting die (11).

8. The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 6, characterized in that: A roller is mounted on each end of the support rod (7).

9. A method for preparing a weakly textured fine-grained magnesium alloy rod, characterized in that: The device for preparing a weakly textured fine-grained magnesium alloy rod according to claim 7 comprises the following steps: S1: Pretreatment of magnesium alloy billet, grinding, cleaning, lubrication and preheating; S2: installing the device on a vertical extruder, connecting the top plate (1) to the oil cylinder of the vertical extruder; lubricating and preheating the extrusion die (10) and the twisting die (11); S3: Shearing and twisting extrusion forming, the magnesium alloy blanks prepared in step S1 are placed in the inlet channel (17.1) and pressed down one by one by the punch (14).

10. The method for preparing a weakly textured fine-grained magnesium alloy rod according to claim 9, characterized in that: In step S1, the magnesium alloy billet pretreatment includes: S1-1. Grind the surface of the magnesium alloy blank with 600-mesh sandpaper to remove oil stains, and then grind with 800-mesh, 1000-mesh, and 1200-mesh sandpaper in sequence; S1-2, mixing acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stirring evenly to prepare a cleaning solution; immersing the magnesium alloy blank prepared in step S1-1 in the cleaning solution, placing the cleaning tank on an ultrasonic cleaning machine to ultrasonically clean the magnesium alloy blank for 40 minutes, then taking out the magnesium alloy blank and cleaning it with anhydrous ethanol, and finally drying it with a hair dryer; S1-3, applying a graphite oil solution to the surface of the magnesium alloy blank prepared in step S1-2; S1-4, start the heating furnace and set the heating temperature of the heating furnace to 450° C. After the temperature of the heating furnace reaches the set temperature, put the magnesium alloy billet prepared in step S1-2 into the heating furnace and keep it warm for 3 hours; Step S2 specifically includes the following steps: S2-1, applying a graphite oil solution on the first inclined surface of the rack (8), the second inclined surface of the reaction block (5), the contact surface between the rack (8) and the fixed block (9), the inside of the variable cross-section curved channel (17), and the inside of the torsional variable cross-section channel (10); S2-2, connecting the top plate (1) to the oil cylinder of the vertical extruder by means of bolts; S2-3, setting the temperature of the first heat source of the heating jacket (15) to 450°C and the temperature of the second heat source to 300°C, and keeping the temperature for 3 hours after reaching the set temperature; Step S3 specifically includes the following steps: S3-1, controlling the oil cylinder of the vertical extruder to withdraw the punch (14), placing the magnesium alloy billet into the inlet channel (17.1), keeping it warm for 1 hour, controlling the punch (14) to move downward for extrusion, and the extrusion speed is 50 mm / min. During the extrusion process, controlling the temperature of the first heat source of the heating jacket (15) to 450° C. and the temperature of the second heat source to 300° C.; S3-2, after the extrusion of the first magnesium alloy billet is completed, the punch (14) is withdrawn and the next magnesium alloy billet is placed, and step S3-1 is repeated to place the third billet, the fourth billet, ... the nth billet, and the magnesium alloy billet passes through the variable cross-section bending channel (17) and the torsional variable cross-section channel (18) and is extruded from the discharge port (12) to obtain a weak texture fine-grained magnesium alloy rod; S3-3. Take out the weakly textured fine-grained magnesium alloy rod obtained in step S3-2, polish its surface with sandpaper, then clean it with the cleaning solution prepared in step S1-2, and finally clean it twice with anhydrous ethanol and blow dry to obtain a finished weakly textured fine-grained magnesium alloy rod.

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