Device and process for preparing fine-grain magnesium alloy plate through turning arc-shaped roller rolling

Abstract

The invention aims to provide a device and process for preparing a fine-grain magnesium alloy plate through turning arc-shaped roller rolling, and belongs to the technical field of light metal plastic forming, and the device comprises a special-shaped roller, a flat roller and a motor; the special-shaped rollers comprise the upper special-shaped roller and the lower special-shaped roller, the lower special-shaped roller is horizontally arranged, 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 degrees. The two ends of the upper special-shaped roller and the two ends of the lower special-shaped roller are connected with an upper bevel gear and a lower bevel gear through roller shafts respectively, the upper bevel gear and the lower bevel gear located at the same end are meshed with each other, and the lower bevel gear located at one end is connected with a motor through a coupler. The flat roller is located behind the discharging end of the special-shaped roller, the included angle between the axis of the flat roller and the axis of the lower special-shaped roller which is horizontally placed is 0-45 degrees, and the fine-grain magnesium alloy plate with the weak basal texture is finally manufactured through the method. The problem that a traditional magnesium alloy plate is prone to forming a strong basal texture is solved, and the performance of the magnesium alloy plate is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of light metal plastic forming, and particularly relates to a device and process for preparing fine-grained magnesium alloy sheets by variable-direction arc rolling. Background Art

[0002] As one of the lightest structural metal materials in the world today, magnesium alloys play an important role in many fields such as automobiles, 3C electronic products, aerospace, and military due to their excellent specific strength and specific stiffness, excellent hot forming characteristics, and extremely high recyclability. However, the close-packed hexagonal crystal structure of magnesium alloys makes only a few slip systems easy to activate at room temperature, far less than the number of slip systems required for polycrystalline deformation, which results in relatively weak mechanical properties of magnesium alloys at room temperature. In addition, there is a significant difference in critical shear stress between basal slip and non-basal slip in magnesium alloys, and non-basal slip is difficult to initiate at low temperatures. This characteristic makes magnesium alloys prone to form strong basal textures during deformation, which has an adverse effect on subsequent deformation processes and thus limits the wide application of magnesium alloys. In recent years, rolling forming technologies such as synchronous rolling, asynchronous rolling (DSR), cross rolling, and accumulative roll bonding (ARB) have been widely used. However, these technologies face challenges in practical applications, such as high requirements for die processing and equipment, huge pressure-bearing requirements, and limitations on the degree of material torsion, etc., which greatly hinder the large-scale continuous preparation of magnesium alloys. Therefore, developing an innovative device and method that can effectively weaken the deformation texture of magnesium alloys and refine their grains has far-reaching significance for further expanding the application fields of magnesium alloys. Summary of the Invention

[0003] Aiming at the above problems, the purpose of the present invention is to provide a device and process for preparing fine-grained magnesium alloy sheets by variable-direction arc rolling. The device adopts innovative profiled rollers and a transmission mechanism. Through a step-by-step rolling method, asymmetric rolling is first carried out with profiled rollers, and then straightening is carried out with a flat roll finishing system. This method improves the forming ability of magnesium alloys, refines the grains, and solves the problem of strong basal texture, thereby improving the properties of the sheets. Through this device and its processing method, continuous severe plastic deformation occurs to the magnesium alloy billet during processing, so as to weaken the basal texture and refine the grains, improve the room-temperature mechanical properties of magnesium alloys, and expand the application range of magnesium alloys.

[0004] The present invention adopts the following technical solutions: A device for preparing fine-grained magnesium alloy sheets by variable-direction arc rolling, comprising profiled rollers, flat rollers, and a motor; Among them, the profiled rollers include an upper profiled roller and a lower profiled roller. The lower profiled roller is horizontally placed, and the included angle between the axis of the upper profiled roller and the axis of the lower profiled roller is 20 - 45°; At both ends of the upper profiled roll and the lower profiled roll, an upper bevel gear and a lower bevel gear are respectively connected through roll shafts. The upper bevel gear and the lower bevel gear at the same end are meshed with each other, and the lower bevel gear at one end is connected to the motor through a coupling. The flat roll is located behind the discharge end of the profiled roll, and the included angle between the axis of the flat roll and the axis of the horizontally placed lower profiled roll is 0 - 45°.

[0005] Furthermore, the lower profiled roll is in a symmetrical hyperbolic shape; the upper profiled roll is in an asymmetrical hyperbola - like shape. The radius of the upper profiled roll near the end with the motor is the same as the radius of the lower profiled roll, and the radius of the other end of the upper profiled roll is 10% smaller than the radius of the end near the motor.

[0006] Furthermore, brackets are provided on the outer sides of the upper bevel gear and the lower bevel gear, and a base is provided at the bottom of the brackets.

[0007] Furthermore, electric heating rods and thermocouples are provided inside the upper profiled roll and the lower profiled roll.

[0008] Furthermore, the roll gap formed between the upper profiled roll and the lower profiled roll is half of the included angle between the axis of the upper profiled roll and the axis of the lower profiled roll.

[0009] Furthermore, a second guide plate is provided at the front end of the feed end of the profiled roll, and side pressure baffles are provided on both sides of the second guide plate; first guide plates are provided at both the feed end and the discharge end of the flat roll, and columns are provided at the bottom of the first guide plates.

[0010] Furthermore, a fixator is provided on the outer side of the bracket. The roll shaft is connected to the fixator through bolts, and a bearing is provided between the roll shaft and the fixator.

[0011] Furthermore, a housing is provided on the outer side of the motor.

[0012] The materials of the upper and lower profiled rolls and the flat roll are all 4Cr5MoSiV1 hot - working die steel.

[0013] A process for preparing fine - grained magnesium alloy sheets by variable - direction arc - roll rolling includes the following steps: S1. Pretreatment of magnesium alloy sheet: S1 - 1. Process the magnesium alloy blank into a rectangular magnesium alloy sheet strip, and polish the surface of the magnesium alloy sheet strip with 600 - mesh sandpaper to remove oil stains, and then polish it successively with 800 - mesh, 1000 - mesh, and 1200 - mesh sandpapers until the surface of the magnesium alloy sheet strip is smooth. S1 - 2. Mix acetone and absolute ethanol in a volume ratio of 3:2 in a cleaning tank and stir evenly to prepare a cleaning solution. S1-3. Immerse the magnesium alloy sheet 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 strip for 60 minutes. Then, take out the magnesium alloy sheet strip, clean it with anhydrous ethanol, and finally dry it with a hair dryer; S1-4. Apply a graphite oil solution to the surface of the magnesium alloy sheet strip prepared in step S1-3 for later use; S2. Preheat the magnesium alloy sheet strip: Set the heating temperature of the vacuum atmosphere heating furnace to 400 °C. After the furnace temperature of the heating furnace reaches the set temperature, put the magnesium alloy sheet strip into the heating furnace and keep it warm for 3 hours; S3. Lubrication, assembly and preheating of the device: S3-1. Lubrication: Apply a graphite oil solution to the surface of the profiled 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 the thermocouple in the corresponding holes, control the temperature of the heating device to 350 °C, and keep it warm for 2 - 4 hours after reaching the set temperature for later use; S4. Rolling, the rolling is divided into two steps. In the first step, the profiled roll performs large deformation shear extrusion deformation on the sheet material. In the second step, the flat roll performs secondary rolling on the sheet material: S4-1. Import the pretreated magnesium alloy sheet strip into the profiled roll with asymmetric geometric features. In the initial bite-in stage, local plastic deformation occurs preferentially at the edges of the sheet strip. During the rolling process, the stress directions on the upper and lower surfaces of the sheet material are different. At this time, the sheet material is subjected to combined stresses: the compressive stress along the normal direction (ND) and the shear stress along the transverse direction (TD) form a synergistic effect. At the same time, due to the change of the geometric parameters of the roll gap width along the TD direction, a gap width difference is formed, which promotes the internal blank flow of the sheet material during the rolling process, generates a large deformation, multiplies a large number of dislocations, activates non-basal slip while suppressing the dynamic recovery process, and refines the grains. During this rolling process, control the temperature of the heating device to 350 °C; Further, the rotational speed range of the profiled roll is 5 - 10 r / min, and the linear speed range is 0.3 - 0.5 m / s; Further, the reduction ratio of this rolling process is 5% - 50%; S4-2. The sheet material after the first pass of rolling enters the flat roll finishing process through the conveyor belt. The reduction ratio and the linear speed of this rolling process are the same as those of the first pass of rolling; During the rolling process of the flat roll, promote the redistribution of the material flow in the TD direction, eliminate the thickness non-uniformity and anisotropy generated by the first pass of processing, and finally make the thickness of the sheet material uniform along the TD direction. At the same time, to a certain extent, eliminate the wrinkles on the surface of the sheet material. After two steps of rolling, a high-performance fine-grained sheet material with weakened basal texture is obtained; S5. Subsequent steps The obtained magnesium alloy sheet and strip is taken out, its surface is polished with sandpaper, and then the magnesium alloy sheet and strip is cleaned with the cleaning solution prepared in step S1-2, and finally cleaned twice with anhydrous ethanol and blown dry 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.

[0014] The rolling method of the present invention is divided into two steps. The first step is to perform asymmetric rolling by special-shaped rollers, and select an upper / lower special-shaped roller group with vertically offset axes. The two rollers rotate in opposite directions, and the preheated magnesium alloy sheet is preferentially guided into the rolling gap along one side in the transverse direction (TD) through the guide plate. In this process, there is a specific angle between the movement direction of the sheet and the rolling gap of the roller, so that one end of the sheet along the TD direction contacts the roller first. This stage of rolling has two significant characteristics. First, because the axes of the upper and lower rollers are not in the same horizontal plane and rotate in opposite directions, the directions of the forces applied by the upper and lower rollers to the two sides of the sheet are different when the sheet passes through the rollers. The difference in the direction of this force causes the sheet to be subjected to shear force in the TD direction while reducing its thickness, which leads to a certain degree of plastic deformation of the sheet. During the process, the sheet is subjected to a shear stress field with significant differences between the upper and lower surfaces - the radial compressive stress applied by the upper and lower rollers and the tangential shear stress form a composite moment, which causes the material to produce lattice deflection in the TD-ND plane, effectively destroying the base surface texture strength formed by traditional rolling. This deformation causes the grains inside the sheet to deflect and offset part of the base surface texture generated by the rolling process. Secondly, due to the difference in the shape of the upper and lower rollers, the width of the rolling gap varies in the TD direction during the rolling process. The gradient design of the special-shaped 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 plate thickness, and cooperates with the dynamic recrystallization process to reduce the average grain size. The flow of the billet caused by this change produces a large amount of deformation, which in turn promotes grain refinement. As the rolling progresses, the material head completely passes through the first rolling mill. When the sheet is extruded from the discharge end of the roller, due to the different directions of the forces on the upper and lower sides and the flow inside the blank, the sheet is continuously acted upon by the non-equilibrium gravitational field, and the movement direction of the entire sheet will deflect in the deflection direction of the upper and lower roller axes, that is, the sheet presents a tilted motion trajectory on one side when it exits the roller (the tilt angle is positively correlated with the angle between the upper and lower special-shaped roller axes). In the second step, a double-roller horizontally opposed flat roller finishing system is used to straighten the inclined sheet at the same rolling speed as the special-shaped roller while maintaining a process temperature of 350°C. By applying additional compressive stress that changes along the TD direction, the residual texture components of the plate core are further randomly distributed (the base surface texture strength is further reduced), and the sheet with a gradient thickness obtained after the first step of rolling undergoes plastic deformation again, the grains are further refined, and the surface wrinkles caused by severe plastic deformation are eliminated, and finally a fine-grained magnesium alloy sheet with a uniform thickness, a flat surface, and a refined grain size and a weak base surface texture is obtained.

[0015] In the above technical scheme, the present invention provides a rolling device for magnesium alloy sheet, which is different from the traditional flat roll rolling tool. The device processes magnesium alloy through an innovative special-shaped roll and transmission mechanism, preparation process, etc., effectively improving its forming ability. The device and process use a step-by-step rolling method, first using special-shaped rolls for asymmetric rolling, so that the magnesium alloy sheet is subjected to shear force and radial compressive stress while the thickness is reduced, resulting in lattice deflection and grain refinement. On the one hand, the inclined rolls constitute the gradient change of the roll gap, and the subsequent flattening of the sheet. These two steps respectively introduce the flow of the sheet along the TD direction, changing the stress state at both ends of the sheet. On the other hand, through the bidirectional rolling of the special-shaped rolls, the TD direction shear force is applied to the sheet, which promotes the activation of a large amount of basal slip. In the second step, the flat roll finishing system is used to straighten the sheet, further refine the grains and eliminate surface wrinkles, and finally obtain a fine-grained magnesium alloy sheet with a weak basal texture. The problem that the existing magnesium alloy sheet is prone to form a strong base surface texture is solved, and the performance of the magnesium alloy sheet is effectively improved.

[0016] Different from the traditional flat roll and other roll gap rolling tools, this technology uses specially designed special-shaped roll mills to process magnesium alloys, which can effectively improve their forming ability. Through the heating element and thermocouple pre-buried in the roll core combined with the electronic control system, the temperature of the roll can be stably controlled to avoid the weakening of the alloy's strength due to the temperature rise caused by the deformation thermal effect, or local rupture due to intense heat conduction. The constant high rolling temperature helps to improve the deformation uniformity of the alloy. At the same time, the rollers with different upper and lower curve shapes constitute the gradient change of the roll gap, introduce shear stress, change the stress state of the rolled plate, and effectively inhibit the formation of strong base surface texture; the preparation process adopted by this technology makes the final plate not only obtain fine grains after a large deformation, but also make the final plate uniform and smooth through the effect of secondary rolling, improve material quality, simplify the process and improve efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the main structure of the device of the present invention; Figure 2 It is a schematic diagram of the external structure of the device of the present invention; Figure 3 Schematic diagram of the relative positions of the upper and lower special-shaped rollers of the present invention; Figure 4 It is a schematic diagram of the dimensions of the upper and lower special-shaped rollers of the present invention; Figure 5 It is a schematic diagram of the upper and lower special-shaped rollers and the rolling seam of the present invention; Figure 6 It is a schematic diagram of the flow of the blank during rolling with a special-shaped roller; Wherein: 1 - blank; 2 - first guide plate; 3 - flat rolling roll; 4 - left support; 5 - left base; 6 - left lower bevel gear; 7 - motor; 8 - housing; 9 - coupling; 10 - left upper bevel gear; 11 - side pressing baffle; 12 - second guide plate; 13 - bolt; 14 - bearing; 15 - fixer; 16 - roll shaft; 17 - right upper bevel gear; 18 - right lower bevel gear; 19 - right base; 20 - right support; 21 - lower special-shaped roll; 22 - upper special-shaped roll; 23 - heating rod and thermocouple hole; 24 - column; 25 - roll gear pin; Ⅰ - primary rolling area; Ⅱ - secondary rolling area. Specific implementation manner

[0018] In combination with the attached drawings, the present invention will be further described.

[0019] As shown in the figure, a device for preparing fine-grained magnesium alloy sheets by variable-direction arc roll rolling includes a special-shaped roll, a flat rolling roll and a motor 7; Wherein, the special-shaped roll includes an upper special-shaped roll 22 and a lower special-shaped roll 21. The lower special-shaped roll 21 is horizontally placed, and the included angle between the axis of the upper special-shaped roll 22 and the axis of the lower special-shaped roll 21 is 20 - 45°; Both ends of the upper special-shaped roll 22 and the lower special-shaped roll 21 are respectively connected with 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 are meshed with each other, and the lower bevel gear at one of the ends is connected with the motor through a coupling; The flat rolling roll 3 is located behind the discharge end of the special-shaped roll. The included angle between the axis of the flat rolling roll 3 and the axis of the horizontally placed lower special-shaped roll 21 is 0 - 45°.

[0020] Further, the lower special-shaped roll 21 is of a symmetrical hyperbolic shape; the upper special-shaped roll 22 is of an asymmetrical hyperbolic shape. The radius of the upper special-shaped roll 22 at the end close to the motor 7 is the same as the radius of the lower special-shaped roll 21, and the radius of the other end of the upper special-shaped roll 22 is 10% smaller than the radius of the end close to the motor 7.

[0021] Further, supports are provided outside the upper bevel gear and the lower bevel gear, and bases are provided at the bottoms of the supports.

[0022] Further, electric heating rods and thermocouples are provided inside the upper special-shaped roll 22 and the lower special-shaped roll 21.

[0023] Further, the rolling gap formed between the upper special-shaped roll 22 and the lower special-shaped roll 21 is half of the included angle between the axis of the upper special-shaped roll 22 and the axis of the lower special-shaped roll 21.

[0024] Further, a second material guiding plate 12 is provided at the front end of the feeding end of the special-shaped rolling roll, and side pressing baffles 11 are provided on both sides of the second material guiding plate 12; first material guiding plates 2 are provided at both the feeding end and the discharging end of the flat rolling roll 3, and columns 24 are provided at the bottom of the first material guiding plates 2.

[0025] Further, a fixer 15 is provided on the outer side of the bracket. The roll shaft 16 is connected to the fixer 15 by bolts 13, and a bearing 14 is provided between the roll shaft 16 and the fixer 15.

[0026] Further, a housing 8 is provided on the outer side of the motor 7.

[0027] Before preparing the fine-grained and weakly textured magnesium alloy, first select the materials and chemical reagents required for the preparation process: (1) Magnesium alloy blank: sheet material, the material is selected as AZ31, containing 96% magnesium, 3% aluminum, and 1% zinc; (2) Sandpaper: solid solid; (3) Graphite oil solution: viscous liquid; (4) Absolute ethanol: liquid liquid, purity 99.5%; A process for preparing fine-grained magnesium alloy sheets by variable-direction arc roll rolling includes the following steps: (1) Install the upper and lower bevel gears at the relative positions on the two side brackets, fix them with the fixer and bolts, connect the upper and lower special-shaped rolling rolls with the upper and lower bevel gears by shafts and fasten them with pins, and connect the motor and the lower rolling roll with a coupling; (2) Process the magnesium alloy blank into a rectangular magnesium alloy strip, and polish the surface of the magnesium alloy strip with 600-mesh sandpaper to remove oil stains, and then polish it with 800-mesh, 1000-mesh, and 1200-mesh sandpapers in sequence until the surface of the magnesium alloy strip is smooth; mix acetone and absolute ethanol in a volume ratio of 3:2 in a cleaning tank and stir evenly to prepare a cleaning solution; immerse the prepared magnesium alloy strip in the cleaning solution, place the cleaning tank on an ultrasonic cleaner to ultrasonically clean the magnesium alloy strip for 60 minutes, take out the magnesium alloy strip and clean it with absolute ethanol, and finally dry it with a hair dryer; (3) Apply the graphite oil solution to the surfaces of the sheet material, rolling rolls, and gears for later use; (4) Set the heating temperature of the vacuum atmosphere heating furnace to 400 °C. After the furnace temperature of the heating furnace reaches the set temperature, put the magnesium alloy strip into the heating furnace and keep it warm for 3 hours; (5) Install the heating rod and thermocouple in the corresponding holes of the rolling roll, control the temperature of the heating device to 350 °C, and keep it warm for 2 hours after reaching the set temperature; (6) The plate coated with graphite oil is placed on the second material guiding plate and fixed on both sides by side pressing baffles. Then the motor is started. During the first rolling, the reduction is set at 15%, the roll speed is 5 r / min, and the linear speed at the center part of the roll is 0.4 m / s. When the magnesium alloy plate strip starts to be rolled, one corner of the sheet first enters the roll gap. The sheet is subjected to a normal stress in the normal direction (ND) and a shear stress in the transverse direction (TD). Due to the slight difference in the curve shapes of the upper and lower rolls, the right end of the roll gap is wider and the left end is narrower. This width inconsistency causes the internal material of the sheet to flow from left to right on the TD-ND cross-section, resulting in significant deformation and further grain refinement. When the sheet is extruded from the discharge end of the roll, due to the different force directions on the upper and lower sides, the moving direction of the whole sheet will tilt to the left. During this process, the temperature of the heating device is precisely controlled at 350 °C.

[0028] (7) The magnesium alloy sheet after the first rolling is transported to the flat roll 3 by a conveyor belt for the second rolling. The reduction for this rolling is 15%. In the flat roll rolling stage, the sheets with different cross-sectional widths are subjected to extrusion forces in the normal direction (ND). At the same time, the internal material of the sheet flows from right to left in the transverse direction (TD), and finally the width of the sheet in the TD direction reaches consistency, meeting the required sheet size, thus completing the processing of the whole sheet.

[0029] (8) Take out the cooled sheet, polish its surface with sandpaper, then clean the magnesium alloy plate strip with a cleaning solution, finally clean it twice with anhydrous ethanol, and dry it with a hair dryer to obtain a fine-grained and weakly textured high-performance magnesium alloy plate strip that can be directly put into use.

[0030] This equipment adopts a unique non-standard roll and drive system, and processes magnesium alloys through a series of innovative processing technologies, significantly enhancing its plastic forming performance. Through the staged rolling technology, first, asymmetric rolling is carried out using non-standard rolls. During the thinning process of the magnesium alloy sheet, it is subjected to 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 rolls form a gradient change in the roll gap clearance and then flatten the sheet, and these two steps respectively promote the flow of the sheet in 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 rolls, a shear force in the TD direction is applied to the sheet, which promotes the massive activation of basal plane slip. In the second stage, the flat roll finishing system is used to straighten the sheet, further refining the grains and eliminating surface wrinkles, and finally obtaining a fine-grained magnesium alloy sheet with a weak basal plane texture. This equipment solves the problem that traditional magnesium alloy sheets are prone to form strong basal plane textures, effectively improving the performance of magnesium alloy sheets.

[0031] 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; Absolute ethanol: CH 3 CH 2 OH, 1200 ml; Acetone: C 3 H 6 O, 800 ml.

[0032] The principle of obtaining fine-grained and weak-textured magnesium alloy by the present invention through the above steps is as follows: (1) Size parameters and relative positions of the upper and lower profiled rolls: The contour curve of the lower 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 profiled roll has the same radius as the lower profiled roll (R1 = R1), and the radius of the right end is slightly smaller than that of the right end of the lower profiled roll (R2 < R1). The side contour of the upper profiled roll is a quasi-hyperbola (slightly different from the side contour of the lower roll); The included angle between the axes of the two profiled rolls in the horizontal plane projection is 20 - 45°. The ratio of the angular velocities of the two profiled rolls is controlled by the radius ratio of the meshing bevel gears; The two pairs of bevel gears can be replaced to change the relative speed of the upper and lower rolls; (2) The first rolling process: The pre-treated magnesium alloy strip is introduced into the profiled roll with asymmetric geometric features. In the initial biting stage, the side plates of the strip enter the roll gap first and preferentially undergo local plastic deformation. During the rolling process, the stress directions on the upper and lower surfaces of the sheet are different. At this time, the sheet is subjected to combined stresses: the compressive stress along the normal direction (ND) and the shear stress along the transverse direction (TD) form a synergistic effect. At the same time, due to the slightly different curve shapes of the upper and lower profiled rolls, the geometric parameters of the roll gap width change along the TD direction, forming a gap width difference, which promotes the internal blank flow of the sheet during the rolling process, generates a large deformation amount, causes a large proliferation of dislocations, activates non-basal plane slip while suppressing the dynamic recovery process, and refines the grains. When the sheet is extruded from the discharge end of the roll, due to the different stress directions on the upper and lower sides, the entire sheet tilts slightly to the left along the RD movement direction; (3) The sheet after the first pass of rolling enters the flat roll finishing process through the conveyor belt. During the flat roll rolling process of the sheet with a thickness varying along the TD direction after the first pass of rolling, it promotes the redistribution of the material flow along the TD direction, eliminates the thickness non-uniformity and anisotropy generated in the first pass of processing, and finally makes the thickness of the sheet uniform along the TD direction. At the same time, to a certain extent, the surface wrinkling of the sheet is eliminated. After two-step rolling, a high-performance fine-grained sheet with weakened basal texture is obtained.

[0033] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described above.

Claims

1. A device for preparing fine-grained magnesium alloy sheets by changing direction arc rolling, characterized in that: It includes a special-shaped roller, a flat roller and a motor (7); The special-shaped roller comprises an upper special-shaped roller (22) and a lower special-shaped roller (21), the lower special-shaped roller (21) is placed horizontally, and the angle between the axis of the upper special-shaped roller (22) and the axis of the lower special-shaped roller (21) is 20-45°; The upper and lower shaped rollers (22 and 21) are connected to an upper bevel gear and a lower bevel gear at both ends through a roller shaft (16), the upper bevel gear and the lower bevel gear at the same end are meshed with each other, and the lower bevel gear at one end is connected to a motor through a coupling; The flat roller (3) is located behind the discharge end of the special-shaped roller, and the angle between the axis of the flat roller (3) and the axis of the horizontally placed lower special-shaped roller (21) is 0-45°.

2. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 1, characterized in that: The lower profiled roller (21) is in a symmetrical hyperbolic shape; the upper profiled roller (22) is in an asymmetrical hyperbolic shape; the radius of the end of the upper profiled roller (22) close to the motor (7) is the same as the radius of the lower profiled roller (21); the radius of the other end of the upper profiled roller (22) is 10% smaller than the radius of the end close to the motor (7).

3. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 1, characterized in that: A bracket is arranged on the outer sides of the upper bevel gear and the lower bevel gear, and a base is arranged at the bottom of the bracket.

4. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 1, characterized in that: Electric heating rods and thermocouples are provided inside the upper special-shaped roller (22) and the lower special-shaped roller (21).

5. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 1, characterized in that: The rolling gap formed between the upper special-shaped rolling roller (22) and the lower special-shaped rolling roller (21) is half of the angle between the axis of the upper special-shaped rolling roller (22) and the axis of the lower special-shaped rolling roller (21).

6. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 1, characterized in that: A second material guide plate (12) is provided at the front end of the feed end of the special-shaped roller, and side pressure baffles (11) are provided on both sides of the second material guide plate (12); a first material guide plate (2) is provided at the feed end and the discharge end of the flat roller (3), and a column (24) is provided at the bottom of the first material guide plate (2).

7. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 3, characterized in that: A fixer (15) is provided on the outer side of the bracket, the roller shaft (16) and the fixer (15) are connected via bolts (13), and a bearing (14) is provided between the roller shaft (16) and the fixer (15).

8. The device for preparing fine-grained magnesium alloy sheet by changing direction arc rolling according to claim 1, characterized in that: A housing (8) is provided on the outer side of the motor (7).

9. A process for preparing a fine-grained magnesium alloy sheet using the device according to claim 1, characterized in that: The steps include: S1. Pretreatment of magnesium alloy sheets: S1-1, processing the magnesium alloy billet into a rectangular magnesium alloy sheet and strip, and grinding the surface of the magnesium alloy sheet and strip with 600-mesh sandpaper to remove oil stains, and then grinding with 800-mesh, 1000-mesh, and 1200-mesh sandpaper in sequence until the surface of the magnesium alloy sheet and strip is smooth; S1-2, mixing acetone and anhydrous ethanol in a volume ratio of 3:2 in a cleaning tank and stirring evenly to prepare a cleaning solution; S1-3, immersing the magnesium alloy sheet and strip prepared in step S1-1 into the cleaning solution prepared in step S1-2, placing the cleaning tank on an ultrasonic cleaning machine to ultrasonically clean the magnesium alloy sheet and strip for 60 minutes, taking out the magnesium alloy sheet and strip and cleaning it with anhydrous ethanol, and finally drying it with a hair dryer; S1-4, applying a graphite oil solution on the surface of the magnesium alloy sheet and strip prepared in step S1-3, and leaving it for use in the next step; S2. Preheating of magnesium alloy plates and strips: Set the heating temperature of the vacuum atmosphere heating furnace to 400°C. After the heating furnace temperature reaches the set temperature, place the magnesium alloy plates and strips into the heating furnace and keep them warm for 3 hours. S3. Lubrication, assembly and preheating of the device: S3-1, Lubrication: Apply graphite oil solution to the surface of the special-shaped roller, the surface of the flat roller, 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℃, keep it warm for 2~4h after reaching the set temperature, and save it for later use; S4, rolling, the rolling is divided into two steps, the first step is to use a special-shaped roller to perform a large deformation shearing and extrusion deformation on the plate, and the second step is to use a flat roller to perform a secondary rolling on the plate: S4-1. The pretreated magnesium alloy sheet and strip are introduced into the special-shaped roller with asymmetric geometric characteristics. In the initial biting stage, the edge of the sheet and strip is preferentially subjected to local plastic deformation. During the rolling process, the stress directions on the upper and lower surfaces of the sheet are different. At this time, the sheet is subjected to composite stress: the compressive stress along the normal direction and the transverse shear stress form a synergistic effect. At the same time, since the geometric parameters of the rolling seam width change along the transverse direction, a seam width difference is formed, which promotes the flow of the internal blank during the rolling process of the sheet, produces a large deformation, causes a large number of dislocations to multiply, activates non-basal slip, and inhibits the dynamic recovery process, so that the grains are refined. During this rolling process, the temperature of the heating device is controlled to be 350°C; further, the rotation speed range of the special-shaped roller is 5~10r / min, and the line speed range is 0.3~0.5m / s; further, the reduction amount of this rolling process is 5%-50%; S4-2, after the first rolling, the plate enters the flat roller finishing process via a conveyor belt. The reduction amount and line speed of this rolling process are consistent with those of the first rolling. During the flat roller rolling process, the redistribution of the material flow in the transverse direction is promoted, and the uneven thickness and anisotropy caused by the first processing are eliminated. Finally, the thickness of the plate is made consistent along the transverse direction, and the wrinkles on the surface of the plate are eliminated. After two-step rolling, a high-performance fine-grained plate with weakened base surface texture is obtained; S5. Next steps The obtained magnesium alloy sheet and strip is taken out, its surface is polished with sandpaper, and then the magnesium alloy sheet and strip is cleaned with the cleaning solution prepared in step S1-2, and finally cleaned twice with anhydrous ethanol and blown dry 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.

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