A device and process for preparing fine-grained magnesium alloy sheet by means of a changeable arc-shaped roller

Abstract

The application aims to provide a device and process for preparing fine-grain magnesium alloy sheet by changing the direction of arc rolling, belonging to the technical field of light metal plastic forming, comprising a special-shaped roller, a flat roller and a motor; the special-shaped roller comprises an upper special-shaped roller and a lower special-shaped roller, the lower special-shaped roller is horizontally placed, and the included angle between the axis of the upper special-shaped roller and the axis of the lower special-shaped roller is 20-45°; the two ends of the upper special-shaped roller and the lower special-shaped roller are respectively connected with upper bevel gears and lower bevel gears through roller shafts, the upper bevel gears and the lower bevel gears at the same end are mutually engaged, and the lower bevel gear at one end is connected with the motor through a shaft coupling; the flat roller is located behind the discharge end of the special-shaped roller, and the included angle between the axis of the flat roller and the axis of the horizontally placed lower special-shaped roller is 0-45°, so that the fine-grain magnesium alloy sheet with weak basal texture is finally prepared by the application. The problem that the traditional magnesium alloy sheet is prone to forming strong basal texture is solved, and the performance of the magnesium alloy sheet is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of light metal plastic forming technology, specifically relating to an apparatus and process for preparing fine-grained magnesium alloy sheets by directional arc rolling. Background Technology

[0002] Magnesium alloys, as one of the world's least dense structural metals, play a vital role in numerous fields, including automobiles, 3C electronics, aerospace, and the military, thanks to their excellent specific strength and stiffness, superior hot forming properties, and extremely high recyclability. However, the close-packed hexagonal crystal structure of magnesium alloys means that only a few slip systems are easily activated at room temperature, far fewer than the number required for polycrystalline deformation. This results in relatively weak mechanical properties of magnesium alloys at room temperature. Furthermore, there is a significant difference in critical shear stress between basal and non-basal slip in magnesium alloys, making non-basal slip difficult to initiate at low temperatures. This characteristic makes magnesium alloys prone to forming strong basal textures during deformation, adversely affecting subsequent deformation processes and thus limiting their widespread application. In recent years, rolling forming technologies, such as simultaneous rolling, asynchronous rolling (DSR), cross rolling, and cumulative stacking rolling (ARB), have been widely used. However, these technologies face challenges in practical applications, such as high requirements for mold processing and equipment, enormous pressure resistance requirements, and limitations on material torsion, all of which significantly hinder the large-scale continuous production of magnesium alloys. Therefore, developing an innovative device and method that can effectively reduce the deformation texture of magnesium alloys and refine their grains is of profound significance for further expanding the application fields of magnesium alloys. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide an apparatus and process for preparing fine-grained magnesium alloy sheets by variable-direction arc-shaped rolling. This apparatus employs innovative irregularly shaped rolls and a transmission mechanism, using a step-by-step rolling method. First, asymmetric rolling is performed using irregularly shaped rolls, followed by straightening using a flat roll finishing system. This method improves the formability of magnesium alloys, refines the grain size, and solves the problem of strong basal texture, thereby enhancing the sheet performance. Through this apparatus and its processing method, the magnesium alloy billet undergoes continuous and intense plastic deformation during processing, thereby weakening the basal texture and refining the grain size, improving the room-temperature mechanical properties of magnesium alloys, and expanding the application range of magnesium alloys.

[0004] The present invention adopts the following technical solution:

[0005] An apparatus for preparing fine-grained magnesium alloy plates by directional arc rolling includes shaped rolls, flat rolls, and a motor;

[0006] The irregularly shaped roll includes an upper irregularly shaped roll and a lower irregularly shaped roll. The lower irregularly shaped roll is placed horizontally, and the angle between the axis of the upper irregularly shaped roll and the axis of the lower irregularly shaped roll is 20-45°.

[0007] The upper and lower shaped rolls are connected to an upper bevel gear and a lower bevel gear at their respective ends via roll shafts. The upper bevel gear and the lower bevel gear at the same end mesh with each other, and the lower bevel gear at one end is connected to the motor via a coupling.

[0008] The flat roll is located behind the discharge end of the shaped roll, and the angle between the axis of the flat roll and the axis of the horizontally placed lower shaped roll is 0-45°.

[0009] Furthermore, the lower shaped roll is a symmetrical hyperbolic shape; the upper shaped roll is an asymmetrical hyperbolic shape, the radius of the end of the upper shaped roll near the motor is the same as the radius of the lower shaped roll, and the radius of the other end of the upper shaped roll is 10% smaller than the radius of the end near the motor.

[0010] Furthermore, the upper bevel gear and the lower bevel gear are provided with brackets on their outer sides, and the bottom of the brackets is provided with a base.

[0011] Furthermore, the upper and lower shaped rolls are equipped with electric heating rods and thermocouples inside.

[0012] Furthermore, the gap formed between the upper and lower shaped rolls is half the angle between the axis of the upper shaped roll and the axis of the lower shaped roll.

[0013] Furthermore, the feed end of the irregularly shaped roll is provided with a second guide plate, and the two sides of the second guide plate are provided with side pressure baffles; the feed end and the discharge end of the flat roll are both provided with a first guide plate, and the bottom of the first guide plate is provided with a column.

[0014] Furthermore, a retainer is provided on the outer side of the bracket, the roller shaft is connected to the retainer by bolts, and a bearing is provided between the roller shaft and the retainer.

[0015] Furthermore, the motor has an outer casing.

[0016] The upper and lower irregularly shaped rolls and the flat rolls are all made of 4Cr5MoSiV1 hot work die steel.

[0017] A process for preparing fine-grained magnesium alloy sheets by variable-direction arc rolling includes the following steps:

[0018] S1. Pretreatment of magnesium alloy sheet:

[0019] S1-1. Process the magnesium alloy billet into rectangular magnesium alloy sheet and strip, and polish the surface of the magnesium alloy sheet and strip with 600-grit sandpaper to remove oil stains. Then polish with 800-grit, 1000-grit, and 1200-grit sandpaper in sequence until the surface of the magnesium alloy sheet and strip is smooth.

[0020] S1-2. Mix acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stir until homogeneous to prepare a cleaning solution.

[0021] S1-3. Immerse the magnesium alloy sheet and strip prepared in step S1-1 into the cleaning solution prepared in step S1-2. Place the cleaning tank on an ultrasonic cleaner and ultrasonically clean the magnesium alloy sheet and strip for 60 minutes. Then, take out the magnesium alloy sheet and strip and clean it with anhydrous ethanol. Finally, dry it with a hair dryer.

[0022] S1-4. Coat the surface of the magnesium alloy sheet and strip prepared in step S1-3 with graphite oil solution for later use.

[0023] S2. Preheating of magnesium alloy sheet and strip: Set the heating temperature of the vacuum atmosphere heating furnace to 400℃. After the furnace temperature reaches the set temperature, put the magnesium alloy sheet and strip into the heating furnace and keep it warm for 3 hours.

[0024] S3. Lubrication, assembly, and preheating of the device:

[0025] S3-1, Lubrication: Apply graphite oil solution to the surface of the irregularly shaped roll, the surface of the flat roll, and the upper and lower bevel gears;

[0026] S3-2, Assembly;

[0027] S3-3. Preheating: Install the electric heating rod and thermocouple in the corresponding holes, control the temperature of the heating device to 350℃, and keep it warm for 2~4 hours after reaching the set temperature, so that it can be used in the next step.

[0028] S4. Rolling, which is divided into two steps: the first step is to use shaped rolls to perform large-deformation shearing and extrusion deformation on the sheet material; the second step is to use flat rolls to perform secondary rolling on the sheet material.

[0029] S4-1. The pretreated magnesium alloy strip is fed into shaped rolls with asymmetric geometry. During the initial bite stage, localized plastic deformation preferentially occurs at the edges of the strip. During rolling, the stress directions on the upper and lower surfaces of the strip differ, resulting in a combined stress effect: compressive stress along the normal (ND) direction and shear stress along the transverse (TD) direction work synergistically. Simultaneously, the change in the geometric parameters of the roll gap width along the TD direction creates a gap width difference, promoting internal billet flow during rolling, resulting in large deformations, significant dislocation proliferation, activation of non-basal slip while inhibiting dynamic recovery, and grain refinement. During this rolling process, the heating device temperature is controlled at 350℃; furthermore, the rotational speed of the shaped rolls ranges from 5 to 10 r / min, and the linear velocity ranges from 0.3 to 0.5 m / s; furthermore, the reduction during this rolling process is 5%-50%.

[0030] S4-2. After the first rolling pass, the sheet material enters the flat roll finishing process via conveyor belt. The reduction and linear speed in this rolling process are consistent with those in the first rolling pass. During the flat roll rolling process, the redistribution of material flow in the TD direction is promoted, eliminating the thickness unevenness and anisotropy caused by the first processing pass, and finally making the sheet material uniform in thickness along the TD direction. At the same time, it also eliminates wrinkling on the sheet surface to a certain extent. After two rolling steps, a high-performance fine-grained sheet material with weakened base texture is obtained.

[0031] S5, Subsequent Steps

[0032] Take out the prepared magnesium alloy sheet and strip, polish its surface with sandpaper, then clean the magnesium alloy sheet and strip with the cleaning solution prepared in step S1-2, finally clean it a second time with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained weak-textured high-performance magnesium alloy sheet and strip that can be directly put into use.

[0033] The rolling method of this invention consists of two steps. The first step involves asymmetrical rolling using shaped rolls. Upper and lower shaped roll sets with vertically offset axes are selected, and the two rolls rotate in opposite directions. The preheated magnesium alloy sheet is preferentially guided into the roll gap along the transverse direction (TD) via a guide plate. During this process, a specific angle exists between the sheet's movement direction and the roll gap, ensuring that one end of the sheet along the TD direction contacts the rolls first. This stage of rolling has two significant characteristics. First, because the axes of the upper and lower rolls are not on the same horizontal plane and rotate in opposite directions, the directions of the forces applied to the sides of the sheet by the upper and lower rolls are different as the sheet passes through the rolls. This difference in the direction of force causes the sheet metal to experience shear force along the TD direction while its thickness decreases, resulting in a certain degree of plastic deformation. During this process, the sheet metal is subjected to a significantly different shear stress field on its upper and lower surfaces—the radial compressive stress and tangential shear stress applied by the upper and lower rolls form a composite torque, causing lattice deflection in the TD-ND plane, effectively disintegrating the basal texture strength formed by traditional rolling. This deformation causes the grains inside the sheet metal to deflect, offsetting some of the basal texture generated by the rolling process. Secondly, due to the difference in the shape of the upper and lower rolls, the width of the roll gap varies in the TD direction during rolling. The gradient design of the irregular roll gap induces layered shear flow of the material along the ND direction, forming a certain degree of strain in the center layer of the sheet thickness. Combined with the dynamic recrystallization process, this reduces the average grain size. This change causes a large amount of deformation in the billet flow, which in turn promotes grain refinement. As rolling progresses, the sheet passes completely through the first mill. When the sheet is extruded from the roll's exit end, due to the different directions of force on the upper and lower sides and the internal flow of the billet, the sheet is subjected to a continuous non-equilibrium gravitational field. The entire sheet's movement direction deflects towards the direction of the upper and lower roll axes, meaning the sheet exhibits a tilted trajectory when exiting the rolls (the tilt angle is positively correlated with the angle between the upper and lower shaped roll axes). The second step uses a horizontally opposed double-roll finishing system. At a process temperature of 350℃, the tilted sheet is straightened at the same rolling speed as the shaped rolls. By applying additional compressive stress varying along the TD direction, the residual texture components in the sheet core are further randomized (the basal texture strength is further reduced), and the sheet, which has a gradient thickness obtained after the first rolling step, undergoes plastic deformation again, further refining the grains. Simultaneously, surface wrinkles caused by severe plastic deformation are eliminated, ultimately resulting in a fine-grained magnesium alloy sheet with uniform thickness, a smooth surface, refined grain size, and a weak basal texture.

[0034] In the above technical solution, the present invention provides a rolling device for magnesium alloy sheets, which differs from traditional flat roll rolling fixtures. This device processes magnesium alloys through an innovative shaped roll and transmission mechanism, as well as a preparation process, effectively improving its forming capability. The device and process employ a step-by-step rolling method. First, asymmetric rolling is performed using shaped rolls, causing the magnesium alloy sheet to be subjected to shear force and radial compressive stress while its thickness is reduced, resulting in lattice deflection and grain refinement. On one hand, the inclined rolls create a gradient change in the roll gap, and the subsequent flattening of the sheet introduces the sheet's flow along the TD direction, changing the stress state at both ends of the sheet. On the other hand, the bidirectional rolling of the shaped rolls applies shear force in the TD direction to the sheet, promoting significant activation of basal slip. The second step uses a flat roll finishing system to straighten the sheet, further refining the grains and eliminating surface wrinkles, ultimately obtaining a fine-grained magnesium alloy sheet with a weak basal texture. This invention solves the problem of existing magnesium alloy sheets easily forming strong base surface textures, effectively improving the performance of magnesium alloy sheets.

[0035] Unlike traditional flat rolls and other roll gap rolling fixtures, this technology uses a specially designed irregularly shaped roll mill to process magnesium alloys, effectively improving their formability. By combining a heating element and thermocouples embedded in the roll core with an electronic control system, the roll temperature can be stably controlled, preventing the alloy's strength from weakening due to deformation heat effects or localized cracking caused by intense heat conduction. The constant high rolling temperature helps improve the alloy's deformation uniformity. Simultaneously, the different curve shapes of the upper and lower rolls create a gradient change in the roll gap, introducing shear stress and altering the stress state of the rolled sheet, effectively suppressing the formation of strong basal texture. The preparation process employed in this technology ensures that the final sheet not only undergoes large deformation to achieve fine grains but also achieves a uniform microstructure and smooth surface through secondary rolling, improving material quality, simplifying the process, and increasing efficiency. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the main structure of the device of the present invention;

[0037] Figure 2 This is a schematic diagram of the external structure of the device of the present invention;

[0038] Figure 3 This is a schematic diagram showing the relative positions of the upper and lower irregularly shaped rolls of the present invention;

[0039] Figure 4 This is a schematic diagram showing the dimensions of the upper and lower irregularly shaped rolls of the present invention;

[0040] Figure 5 This is a schematic diagram of the upper and lower irregularly shaped rolls and the roll gap of the present invention;

[0041] Figure 6 This is a schematic diagram showing the flow of the billet during the rolling process using irregularly shaped rolls.

[0042] Wherein: 1-Blank; 2-Guide plate one; 3-Flat roll; 4-Left side bracket; 5-Left side base; 6-Left side lower bevel gear; 7-Motor; 8-Housing; 9-Coupling; 10-Left side upper bevel gear; 11-Side pressure baffle; 12-Guide plate two; 13-Bolt; 14-Bearing; 15-Fixer; 16-Roll shaft; 17-Right side upper bevel gear; 18-Right side lower bevel gear; 19-Right side base; 20-Right side bracket; 21-Lower shaped roll; 22-Upper shaped roll; 23-Heating rod and thermocouple hole; 24-Column; 25-Roll gear pin;

[0043] Ⅰ - Primary rolling zone; Ⅱ - Secondary rolling zone. Detailed Implementation

[0044] The invention will be further described with reference to the accompanying drawings.

[0045] As shown in the figure, an apparatus for preparing fine-grained magnesium alloy plates by directional arc rolling includes shaped rolls, flat rolls and a motor 7.

[0046] The irregularly shaped roll includes an upper irregularly shaped roll 22 and a lower irregularly shaped roll 21. The lower irregularly shaped roll 21 is placed horizontally, and the angle between the axis of the upper irregularly shaped roll 22 and the axis of the lower irregularly shaped roll 21 is 20-45°.

[0047] The upper irregular roll 22 and the lower irregular roll 21 are respectively connected to an upper bevel gear and a lower bevel gear through a roll shaft 16. The upper bevel gear and the lower bevel gear at the same end mesh with each other, and the lower bevel gear at one end is connected to the motor through a coupling.

[0048] The flat roll 3 is located behind the discharge end of the shaped roll, and the angle between the axis of the flat roll 3 and the axis of the horizontally placed lower shaped roll 21 is 0-45°.

[0049] Furthermore, the lower shaped roll 21 is a symmetrical hyperbolic shape; the upper shaped roll 22 is an asymmetrical hyperbolic shape, the radius of the end of the upper shaped roll 22 near the motor 7 is the same as the radius of the lower shaped roll 21, and the radius of the other end of the upper shaped roll 22 is 10% smaller than the radius of the end near the motor 7.

[0050] Furthermore, the upper bevel gear and the lower bevel gear are provided with brackets on their outer sides, and the bottom of the brackets is provided with a base.

[0051] Furthermore, the upper shaped roll 22 and the lower shaped roll 21 are equipped with electric heating rods and thermocouples inside.

[0052] Furthermore, the gap formed between the upper shaped roll 22 and the lower shaped roll 21 is half the angle between the axis of the upper shaped roll 22 and the axis of the lower shaped roll 21.

[0053] Furthermore, the feed end of the irregularly shaped roll is provided with a guide plate 2 12, and the two sides of the guide plate 2 12 are provided with side pressure baffles 11; the feed end and the discharge end of the flat roll 3 are both provided with a guide plate 1 2, and the bottom of the guide plate 1 2 is provided with a column 24.

[0054] Furthermore, a retainer 15 is provided on the outer side of the bracket, and the roller shaft 16 is connected to the retainer 15 by bolts 13. A bearing 14 is provided between the roller shaft 16 and the retainer 15.

[0055] Furthermore, the motor 7 has a housing 8 on its outer side.

[0056] Before preparing fine-grained, weakly textured magnesium alloys, carefully select the materials and chemical reagents required for the preparation process:

[0057] (1) Magnesium alloy billet: plate material, AZ31, containing 96% magnesium, 3% aluminum and 1% zinc;

[0058] (2) Sandpaper: solid;

[0059] (3) Graphite oil solution: a viscous liquid;

[0060] (4) Anhydrous ethanol: liquid, purity 99.5%;

[0061] A process for preparing fine-grained magnesium alloy sheets by variable-direction arc rolling includes the following steps:

[0062] (1) The upper and lower bevel gears are installed on opposite sides of the brackets and fixed with fasteners and bolts. The upper and lower irregular rolls are connected to the upper and lower bevel gears with shafts and fastened with pins. The motor and the lower roll are connected with a coupling.

[0063] (2) The magnesium alloy billet is processed into a rectangular magnesium alloy sheet and strip, and the surface of the magnesium alloy sheet and strip is polished with 600 grit sandpaper to remove oil stains. Then, it is polished with 800 grit, 1000 grit and 1200 grit sandpaper in sequence until the surface of the magnesium alloy sheet and strip is smooth. Acetone and anhydrous ethanol are mixed in a cleaning tank at a volume ratio of 3:2 and stirred evenly to prepare a cleaning solution. The prepared magnesium alloy sheet and strip is immersed in the cleaning solution. The cleaning tank is placed on an ultrasonic cleaner and the magnesium alloy sheet and strip is ultrasonically cleaned for 60 minutes. The magnesium alloy sheet and strip is then taken out and cleaned with anhydrous ethanol. Finally, it is dried with a hair dryer.

[0064] (3) Coat the surfaces of the sheet metal, rolls, and gears with graphite oil solution for later use;

[0065] (4) Set the heating temperature of the vacuum atmosphere heating furnace to 400℃. After the furnace temperature reaches the set temperature, put the magnesium alloy plate and strip into the heating furnace and keep it at that temperature for 3 hours.

[0066] (5) Install the heating rod and thermocouple in the corresponding hole of the roll, control the temperature of the heating device to 350℃, and keep it warm for 2 hours after reaching the set temperature.

[0067] (6) The sheet material coated with graphite oil is placed on the guide plate and fixed on both sides by side pressure baffles. Then the motor is started. During the initial rolling, the reduction is set to 15%, the roll speed is 5 r / min, and the linear velocity of the center part of the roll is 0.4 m / s. When the magnesium alloy sheet and strip start rolling, one corner of the sheet enters the roll gap first. The sheet is subjected to compressive stress in the normal (ND) direction and shear stress in the transverse (TD) direction. Due to the slight difference in the curve shape of the upper and lower rolls, the right end of the roll gap is wider and the left end is narrower. This inconsistency in width causes the material inside the sheet to flow from left to right on the TD-ND section, resulting in significant deformation and thus refining the grains. When the sheet is extruded from the roll outlet end, due to the different force directions on the upper and lower sides, the entire sheet will tilt to the left. During this process, the temperature of the heating device is precisely controlled at 350℃.

[0068] (7) After the first rolling, the magnesium alloy sheet is transported by conveyor belt to the flat roll 3 for a second rolling. The reduction in this rolling is 15%. During the flat roll rolling stage, the sheets with different cross-sectional widths are subjected to extrusion force in the normal (ND) direction. At the same time, the material inside the sheet flows from right to left in the transverse (TD) direction, eventually making the width of the sheet in the TD direction consistent, meeting the required sheet size, and thus completing the entire sheet processing process.

[0069] (8) Take out the cooled sheet material, polish its surface with sandpaper, clean the magnesium alloy sheet and strip with cleaning solution, clean it a second time with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained weak-textured high-performance magnesium alloy sheet and strip that can be put into use directly.

[0070] The device adopts unique non-standard rolling rolls and a transmission system, and processes magnesium alloys through a series of innovative processing technologies, significantly enhancing their plastic forming performance. Through the staged rolling technology, first, asymmetric rolling is carried out using non-standard rolling rolls. During the thinning process of the magnesium alloy sheet, it undergoes shear force and radial pressure, which leads to the deflection of the crystal lattice and the refinement of grains. On the one hand, the inclined rolling rolls form a gradient change in the roll gap, and then the sheet is leveled. These two steps respectively promote the flow of the sheet along the TD direction and change the stress state at both ends of the sheet. On the other hand, through the two-way rolling of non-standard rolling rolls, a shear force in the TD direction is applied to the sheet, which promotes the extensive activation of basal plane slip. In the second stage, the sheet is straightened using a flat roll finishing system, further refining the grains and eliminating surface wrinkles, and finally obtaining a fine-grained magnesium alloy sheet with a weak basal texture. This device solves the problem that traditional magnesium alloy sheets are prone to form a strong basal texture and effectively improves the performance of magnesium alloy sheets.

[0071] Materials and chemical reagents used: AZ31 magnesium alloy plate blanks, with a width d = 20 mm; sandpaper: SiC, 600 mesh, 2 sheets; 1000 mesh, 2 sheets; 1200 mesh, 2 sheets; high-temperature graphite oil solution: C, 500 g; anhydrous ethanol: CH3CH2OH, 1200 ml; acetone: C3H6O, 800 ml.

[0072] The principle of obtaining the fine-grained and weakly textured magnesium alloy by the present invention is as follows:

[0073] (1) Size parameters and relative positions of the upper and lower non-standard rolling rolls: The contour curve of the lower rolling roll is a standard hyperbola, with hyperbola parameters: real semi-axis a = 1, imaginary semi-axis b = 4, e = ; The left end of the upper non-standard rolling roll has the same radius as the lower non-standard rolling roll (R1 = R1), and the right end radius is slightly smaller than the right end of the lower non-standard rolling roll (R2 < R1). The side contour of the upper non-standard rolling roll is a hyperbola-like shape (slightly different from the side contour of the lower rolling roll); The included angle between the axes of the two non-standard rolling rolls in the horizontal plane projection is 20 - 45°, and the ratio of the angular velocities of the two non-standard rolling rolls is controlled by the ratio of the radii of the meshing bevel gears; Two pairs of bevel gears can be replaced to change the relative speed of the upper and lower rolling rolls;

[0074] (2) First step of rolling process: The pretreated magnesium alloy strip is fed into a shaped roll with asymmetric geometry. In the initial biting stage, the edge plate of the strip enters the roll gap first and preferentially undergoes local plastic deformation. During the rolling process, the stress directions on the upper and lower surfaces of the strip are different. At this time, the strip is subjected to a composite stress: the compressive stress along the normal (ND) direction and the shear stress in the transverse (TD) direction form a synergistic effect. At the same time, due to the slight difference in the curve shape of the upper and lower shaped rolls, the geometric parameters of the roll gap width change along the TD direction, forming a gap width difference, which promotes the internal billet flow of the strip during the rolling process, generates a large amount of deformation, causes a large number of dislocations to multiply, activates non-basal slip while inhibiting the dynamic recovery process, and refines the grains. When the strip is extruded from the roll outlet end, due to the different stress directions on the upper and lower sides, the entire strip tilts slightly to the left along the RD movement direction;

[0075] (3) The sheet material after the first rolling pass enters the flat roll finishing process via conveyor belt. After the first rolling pass, the sheet material with a thickness that varies along the TD direction is promoted to redistribute the material flow along the TD direction during the flat roll rolling process, eliminating the thickness unevenness and anisotropy caused by the first processing pass, and finally making the sheet material with a uniform thickness along the TD direction. At the same time, it also eliminates the wrinkling of the sheet material surface to a certain extent. After two rolling steps, a high-performance fine-grained sheet material with weakened base texture is obtained.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An apparatus for preparing fine-grained magnesium alloy plates by directional arc rolling, characterized in that: Including shaped rolls, flat rolls and motors (7); The irregularly shaped roll includes an upper irregularly shaped roll (22) and a lower irregularly shaped roll (21). The lower irregularly shaped roll (21) is placed horizontally, and the angle between the axis of the upper irregularly shaped roll (22) and the axis of the lower irregularly shaped roll (21) is 20-45°. The upper and lower shaped rolls (21) are connected to an upper bevel gear and a lower bevel gear respectively via a roll shaft (16). The upper bevel gear and the lower bevel gear at the same end mesh with each other, and the lower bevel gear at one end is connected to the motor via a coupling. The flat roll (3) is located behind the discharge end of the shaped roll, and the angle between the axis of the flat roll (3) and the axis of the horizontally placed lower shaped roll (21) is 0-45°. The lower shaped roll (21) is a symmetrical hyperbolic shape; the upper shaped roll (22) is an asymmetrical hyperbolic shape. The radius of the end of the upper shaped roll (22) near the motor (7) is the same as the radius of the lower shaped roll (21), and the radius of the other end of the upper shaped roll (22) is 10% smaller than the radius of the end near the motor (7).

2. The apparatus for preparing fine-grained magnesium alloy plates by variable-direction arc rolling according to claim 1, characterized in that: The upper and lower bevel gears are provided with brackets on their outer sides, and the bottom of the brackets is provided with a base.

3. The apparatus for preparing fine-grained magnesium alloy plates by variable-direction arc rolling according to claim 1, characterized in that: The upper shaped roll (22) and the lower shaped roll (21) are equipped with electric heating rods and thermocouples inside.

4. The apparatus for preparing fine-grained magnesium alloy plates by variable-direction arc rolling according to claim 1, characterized in that: The gap formed between the upper shaped roll (22) and the lower shaped roll (21) is half the angle between the axis of the upper shaped roll (22) and the axis of the lower shaped roll (21).

5. The apparatus for preparing fine-grained magnesium alloy plates by variable-direction arc rolling according to claim 1, characterized in that: The feed end of the irregularly shaped roll is provided with a guide plate 2 (12), and the two sides of the guide plate 2 (12) are provided with side pressure baffles (11); the feed end and the discharge end of the flat roll (3) are both provided with a guide plate 1 (2), and the bottom of the guide plate 1 (2) is provided with a column (24).

6. The apparatus for preparing fine-grained magnesium alloy plates by variable-direction arc rolling according to claim 2, characterized in that: The bracket has a retainer (15) on its outer side. The roller shaft (16) is connected to the retainer (15) by bolts (13). A bearing (14) is provided between the roller shaft (16) and the retainer (15).

7. The apparatus for preparing fine-grained magnesium alloy plates by variable-direction arc rolling according to claim 1, characterized in that: The motor (7) is provided with a housing (8) on its outer side.

8. A process for preparing fine-grained magnesium alloy plates using the apparatus of claim 1, characterized in that: Includes the following steps: S1. Pretreatment of magnesium alloy sheet: S1-1. Process the magnesium alloy billet into rectangular magnesium alloy sheet and strip, and polish the surface of the magnesium alloy sheet and strip with 600-grit sandpaper to remove oil stains. Then polish with 800-grit, 1000-grit, and 1200-grit sandpaper in sequence until the surface of the magnesium alloy sheet and strip is smooth. S1-2. Mix acetone and anhydrous ethanol in a cleaning tank at a volume ratio of 3:2 and stir until homogeneous to prepare a cleaning solution. S1-3. Immerse the magnesium alloy sheet and strip prepared in step S1-1 into the cleaning solution prepared in step S1-2. Place the cleaning tank on an ultrasonic cleaner and ultrasonically clean the magnesium alloy sheet and strip for 60 minutes. Then, take out the magnesium alloy sheet and strip and clean it with anhydrous ethanol. Finally, dry it with a hair dryer. S1-4. Coat the surface of the magnesium alloy sheet and strip prepared in step S1-3 with graphite oil solution for later use. S2. Preheating of magnesium alloy sheet and strip: Set the heating temperature of the vacuum atmosphere heating furnace to 400℃. After the furnace temperature reaches the set temperature, put the magnesium alloy sheet and strip into the heating furnace and keep it warm for 3 hours. S3. Lubrication, assembly, and preheating of the device: S3-1, Lubrication: Apply graphite oil solution to the surface of the irregularly shaped roll, the surface of the flat roll, and the upper and lower bevel gears; S3-2, Assembly; S3-3. Preheating: Install the electric heating rod and thermocouple in the corresponding holes, control the temperature of the heating device to 350℃, and keep it warm for 2~4 hours after reaching the set temperature, so that it can be used in the next step. S4. Rolling, which is divided into two steps: the first step is to use shaped rolls to perform large-deformation shearing and extrusion deformation on the sheet material; the second step is to use flat rolls to perform secondary rolling on the sheet material. S4-1. The pretreated magnesium alloy strip is fed into shaped rolls with asymmetric geometry. In the initial biting stage, local plastic deformation preferentially occurs at the edges of the strip. During rolling, the stress directions on the upper and lower surfaces of the strip are different, resulting in a combined stress: compressive stress along the normal direction and shear stress in the transverse direction work synergistically. Simultaneously, due to the change in the geometric parameters of the roll gap width along the transverse direction, a gap width difference is formed, which promotes the internal billet flow of the strip during rolling, generating a large amount of deformation, causing a large number of dislocations to multiply, activating non-basal slip while inhibiting the dynamic recovery process, thus refining the grains. During this rolling process, the temperature of the heating device is controlled at 350℃. Furthermore, the rotational speed of the shaped rolls is in the range of 5~10 r / min, and the linear speed is in the range of 0.3~0.5 m / s. Furthermore, the reduction in this rolling process is 5%-50%. S4-2. After the first rolling pass, the sheet material enters the flat roll finishing process via conveyor belt. The reduction and linear speed of this rolling process are consistent with those of the first rolling pass. During the flat roll rolling process, the redistribution of material flow in the transverse direction is promoted, the thickness unevenness and anisotropy generated by the first processing pass are eliminated, and the sheet material thickness is made consistent in the transverse direction. At the same time, wrinkling on the sheet material surface is eliminated. After two rolling steps, a high-performance fine-grained sheet material with weakened base texture is obtained. S5, Subsequent Steps Take out the prepared magnesium alloy sheet and strip, polish its surface with sandpaper, then clean the magnesium alloy sheet and strip with the cleaning solution prepared in step S1-2, finally clean it a second time with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained weak-textured high-performance magnesium alloy sheet and strip that can be directly put into use.

Images