A rare earth magnesium alloy wide plate and a preparation method thereof

Abstract

The application discloses a rare earth magnesium alloy wide plate and a preparation method thereof. The rare earth magnesium alloy wide plate has a width of not less than 2000 mm and good mechanical properties. The rare earth magnesium alloy plate with a large size and a width of not less than 2000 mm is prepared by taking a magnesium alloy as raw material and through a cooperative process of ring rolling forming-ring cutting-straightening-cross wide rolling. The large-size pie blank is cut into a plurality of ring blanks and respectively ring-rolled to form a ring-shaped piece with an outer diameter of about 2000 mm, an axial height and a wall thickness satisfying a matching relationship of target plate size. After the ring-shaped piece is axially cut, unfolded, straightened and longitudinally and transversely cross-rolled, the high-performance plate with a width of not less than 2000 mm is obtained. The technical problems of uneven structure, easy cracking and difficult control of size precision in the preparation of the large-size rare earth magnesium alloy plate are solved, and the prepared ring-rolled plate has high strength and good plasticity. The prepared ring-rolled plate can meet the demand of the field of aerospace, new energy vehicles and other fields for large-size light-weight structural parts, and has important industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material processing technology, specifically relating to a large-size, high-performance rare earth magnesium alloy wide plate and its preparation method. Background Technology

[0002] Magnesium alloys, as one of the lightest metallic structural materials, possess outstanding advantages such as high specific strength, excellent damping performance, and good recyclability. Furthermore, by utilizing the solid solution strengthening and precipitation strengthening effects of rare earth elements (such as gadolinium (Gd) and yttrium (Y), magnesium alloys significantly improve the material's strength and high-temperature stability, making them a key material for solving the challenge of lightweight equipment. Therefore, the demand for rare earth magnesium alloy materials is increasing in fields such as aerospace, new energy vehicles, and high-end equipment; in particular, there is an urgent need for large-size, high-performance rare earth magnesium alloy sheets for components such as aerospace fuselage skins and new energy vehicle battery trays.

[0003] In related technologies, wide rare-earth magnesium alloy plates are prepared by direct rolling or conventional forging-rolling. The close-packed hexagonal crystal structure of magnesium alloys tends to result in a low room-temperature slip system and poor deformability. During large-size deformation processing, problems such as edge cracking, uneven microstructure, residual stress accumulation, and difficulty in controlling plate shape easily occur. Therefore, for rare-earth magnesium alloy plates with a width of not less than 2000 mm, the plate dimensions, microstructure uniformity, and flatness prepared by direct rolling or conventional forging-rolling methods cannot meet the corresponding requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing large-size rare earth magnesium alloy plates and the plates prepared therefrom, solving the problems of easy cracking, poor microstructure uniformity, and poor mechanical properties during the preparation of wide plates.

[0005] This invention provides a wide sheet of rare earth magnesium alloy, wherein the alloy composition of the sheet comprises, by mass percentage: Gd 8.5-9.5 wt.%, Y 3.5-4.5 wt.%, Zn 1.2-1.8 wt.%, Zr 0.2-0.4 wt.%, with the balance being Mg and unavoidable impurities, and the total content of unavoidable impurities not exceeding 0.1 wt.%.

[0006] Furthermore, the dimensions of the rare earth magnesium alloy wide plate are ≥2000 mm in width and 3~10 mm in thickness.

[0007] Furthermore, the room temperature mechanical properties of the rare earth magnesium alloy wide plate are: yield strength ≥ 410 MPa, ultimate tensile strength ≥ 470 MPa, and elongation ≥ 4.4%.

[0008] The embodiments of the present invention also provide a method for preparing wide rare earth magnesium alloy plates, using Mg, Gd, Y, Zn and Zr as alloy system raw materials, and proceeding according to the proportions through ingot preparation, pre-homogenization before extrusion, extrusion billet preparation, three-stage homogenization treatment, isothermal multi-directional forging, ring rolling, ring straightening, cross-width rolling and heat treatment of the rolled plate.

[0009] Furthermore, the preparation method of the wide rare earth magnesium alloy sheet includes the following steps:

[0010] (1) Ingot preparation: Magnesium alloy ingots with Mg, Gd, Y, Zn and Zr as alloying materials are prepared by multi-stage forced filtration and graded cooling process. The ingot mold specifications are Φ≥650 mm and height≥1800 mm. After machining and flaw detection, the initial billet with size Φ≥630 mm and height≥1700 mm is obtained. The single-sided cutting amount is 8~12 mm.

[0011] (2) Pre-homogenization and extrusion blanking: The initial blank is placed in a heating furnace and preheated at 480-500 ℃ for 7-9 h. After preheating, it is transferred to the extruder for extrusion blanking. The extrusion temperature is 410-450 ℃, the extrusion speed is 0.4-0.6 mm / s, and the extrusion coefficient is 1.3-1.6.

[0012] (3) Three-stage homogenization treatment: After the extruded billet is shaped, it is subjected to three-stage homogenization heat treatment at different temperatures. The heat treatment temperature is 360~520 ℃, and the temperature of each stage increases by 20~80 ℃. The holding time of each stage is 6~20 h.

[0013] (4) Isothermal multi-directional forging: The billet after homogenization heat treatment is transferred to a forging press and isothermal multi-directional forging to form a cake. The preheating temperature of the forging anvil is 440~490 ℃, the preheating time is 6~10 h, and 4~6 forging passes are performed in the three-dimensional X, Y and Z directions. The deformation in one direction is ≥45%.

[0014] (5) Ring rolling: The blank is cut and trimmed to form several ring blanks. After core removal, the individual ring blanks are rolled on a ring rolling mill. Before ring rolling, the blank is kept at 370~390 ℃ for 5~7 h, the roll preheating temperature is 280~330 ℃, and the ring rolling deformation is 30~50%, to obtain a ring part with an outer diameter of about Φ2000 mm, an axial height H of 400~700 mm, and a wall thickness t0 of 30~60 mm.

[0015] (6) Ring cutting and straightening: the ring is cut along the axial direction, kept at 300~320 ℃ for 2~4 h, and straightened by a pressure straightening machine to obtain a slab;

[0016] (7) Wide-width rolling: The straightened slab is heated to 420~440 ℃ and held for 3~5 h. Cross-width rolling is carried out within the temperature window of 420~440 ℃. When the slab temperature is lower than 400 ℃ during rolling, it is returned to the furnace to be reheated to 420~440 ℃ and then rolled. The rolling speed is 0.2~0.4 m / s. After 12~20 passes, the total thickness reduction rate is 70~90%, and a plate with a width of not less than 2000 mm and a thickness of 3~10 mm is obtained.

[0017] (8) Subsequent heat treatment: the rolled plate is subjected to at least one of the following: graded cooling, vibration treatment, deep cryogenic treatment, and then isothermal aging treatment to prepare a wide rare earth magnesium alloy plate with a width greater than 2000 mm.

[0018] Further, in step (1), the multi-stage forced filtration uses a 20-90 mesh metal filter screen, ceramic filter sheet or composite filter assembly that is resistant to magnesium alloy melt corrosion, and the warp and weft lines of adjacent filter screens are at 45°; the staged cooling is in sequence room temperature air blowing cooling, atomized water cooling, 70-85° warm water cooling and room temperature water cooling, and the staged cooling uses the outer wall of the mold, cooling jacket or indirect cooling channel.

[0019] Furthermore, in step (2), the preheating temperature is 470~510 ℃, the preheating time is 7~9 h, and the extrusion process adopts online spray quenching cooling.

[0020] Furthermore, in step (4), the isothermal multi-directional forging includes 3 to 4 upsetting-drawing cycles, and the final blank size is Φ 950 to 1100 mm and the thickness is 600 to 750 mm.

[0021] Furthermore, in step (5), the ring rolling process adopts online induction heating, the ring rolling lubricant is a graphite-based lubricant, and the core material removed by the core removal process has a diameter of 150~250 mm, resulting in an annular part with an outer diameter of Φ 2000 mm, an axial height H of 400~700 mm, and a wall thickness t0 of 30~60 mm.

[0022] Furthermore, in step (6), the ring is cut by plasma cutting or mechanical cutting, the straightening pressure is 500~800 t, and the flatness error of the slab is ≤2 mm / m.

[0023] Furthermore, in step (8), the graded cooling first involves immersing the rolled plate in hot water at 70~80 ℃ for 4~8 min, and then transferring it to ice water at 0~5 ℃ for 8~12 min; the isothermal aging temperature is 190~220 ℃, and the holding time is 12~40 h.

[0024] Furthermore, in step (8), after graded cooling, vibration treatment for 8~25 min and / or liquid nitrogen cryogenic treatment for 15~35 min are performed.

[0025] The beneficial effect of the technical solution adopted in the embodiments of the present invention is that the present invention uses Mg-(8.5-9.5)Gd-(3.5-4.5)Y-(1.2-1.8)Zn-(0.2-0.4)Zr(wt.%) alloy as raw material, and prepares a high-performance plate with a width of not less than 2000 mm through the process path of "ring rolling forming - ring straightening - cross wide rolling". In this invention, multi-stage forced filtration and graded cooling can reduce melt inclusions, shrinkage porosity, and macroscopic segregation, providing ingots with more uniform composition and microstructure for subsequent deformation; extrusion billeting, three-stage homogenization treatment, and isothermal multi-directional forging can break the as-cast microstructure, promote uniform diffusion of alloying elements, and refine grains, improving the plasticity of the billet and its subsequent ring rolling forming capability; ring rolling forming, through continuous circumferential deformation, makes the strain distribution more uniform, reducing the risk of edge cracking when large-sized billets are directly widened; ring straightening and cross-rolling in both directions realize the size conversion from ring parts to wide plates, and improve the microstructure, texture, and uniformity of plate shape through cross-deformation in two directions; further graded cooling, vibration treatment and / or cryogenic treatment, as well as isothermal aging, are beneficial for releasing residual stress and exerting precipitation strengthening effect.

[0026] Through the synergistic effect of the preparation method in this invention, the problems of uneven microstructure, easy cracking, and difficulty in controlling dimensional accuracy during the preparation of large-size rare earth magnesium alloy plates are solved. Rare earth magnesium alloy plates with a width of not less than 2000 mm, room temperature yield strength ≥410 MPa, ultimate tensile strength ≥470 MPa, and elongation ≥4.4% are obtained, which can meet the needs of aerospace, new energy vehicles and other fields for large-size lightweight structural components. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the annular component during the preparation process of the rare earth magnesium alloy wide plate in Embodiment 1 of the present invention;

[0028] Figure 2 This is a schematic diagram of the ring section during the preparation process of the rare earth magnesium alloy wide plate in Embodiment 1 of the present invention;

[0029] Figure 3 This is a schematic diagram of the slab during the preparation process of the rare earth magnesium alloy wide plate in Embodiment 1 of the present invention;

[0030] Figure 4 This is a schematic diagram of the slab straightening process in the preparation method of wide rare earth magnesium alloy plates according to Embodiment 1 of the present invention;

[0031] Figure 5 This is a schematic diagram of the slab after straightening during the preparation process of the rare earth magnesium alloy wide plate in Embodiment 1 of the present invention;

[0032] Figure 6 This is a schematic diagram of the wide rolling process in the method for preparing wide rare earth magnesium alloy plates according to Embodiment 1 of the present invention.

[0033] Figure 7 The images show a comparison of the low-magnification metallographic structures of the ring rolling (a), (b) and cross-broad rolling (c), (d) phases of the rare earth magnesium alloy wide plate preparation method in Embodiment 1 of the present invention.

[0034] Figure 8 The figures represent the uniaxial tensile stress-strain curves of the cross-width rolling state during the preparation process of the wide rare earth magnesium alloy plates in Embodiments 1-4 of this invention.

[0035] Among them, 1 is the ring part, 2 is the slit, 3 is the slab, 4 is the pressure straightening machine, 5 is the wide-width four-roll mill, and 6 is the plate. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0037] This invention addresses the challenges of forming large-size rare earth magnesium alloy billets, poor microstructure uniformity, and low dimensional accuracy through collaborative process innovation. It achieves efficient transformation from "ring part preparation to ring splitting to wide plate production," providing technical support for the large-scale application of rare earth magnesium alloys.

[0038] Example 1

[0039] This embodiment provides a wide sheet of rare earth magnesium alloy, wherein the alloy composition of the sheet includes, by mass percentage: Gd 8.5-9.5 wt.%, Y 3.5-4.5 wt.%, Zn 1.2-1.8 wt.%, Zr 0.2-0.4 wt.%, with the balance being Mg and unavoidable impurities, and the total content of unavoidable impurities not exceeding 0.1 wt.%.

[0040] Preferably, the dimensions of the rare earth magnesium alloy wide sheet are ≥2000 mm wide and 3~10 mm thick.

[0041] Preferably, the room temperature mechanical properties of the rare earth magnesium alloy wide plate are: yield strength ≥ 410 MPa, ultimate tensile strength ≥ 482 MPa, and elongation ≥ 4.4%.

[0042] See attached document Figures 1-6 The present invention also provides a method for preparing the wide rare earth magnesium alloy plate, comprising the following steps:

[0043] (1) Ingot preparation: Industrial pure magnesium ingots, magnesium-gadolinium master alloy, magnesium-yttrium master alloy, zinc ingots and magnesium-zirconium master alloy are selected as raw materials, and the raw materials are prepared and smelted according to the above mass percentage range;

[0044] Specifically, a multi-stage forced filtration process is employed to purify the melt, which is sequentially passed through a 20-90 mesh metal filter resistant to magnesium alloy melt corrosion, a ceramic filter, or a composite filter assembly, with the angle between the warp and weft lines of adjacent filter screens at 45°. A graded cooling process is used, sequentially passing the melt through room temperature air blowing, atomized water cooling, 70-85 ℃ warm water cooling, and room temperature water cooling. The cooling rate in the near-mold wall region is controlled at 4-7 ℃ / s to prepare an ingot with a diameter of Φ650 mm × 1800 mm. After the ingot cools to room temperature, 8-12 mm of oxide scale, segregation layer, and surface defects are removed by machining. Ultrasonic testing yields an initial billet with a diameter of Φ630 mm × 1700 mm. Ultrasonic testing is performed according to the current GB / T 6402 standard. The graded cooling utilizes the outer wall of the mold, a cooling jacket, or an indirect cooling channel, ensuring that the cooling medium does not directly contact the magnesium alloy melt.

[0045] (2) Extrusion blanking: The initial blank is placed in a heating furnace and pre-homogenized and preheated at 480-500 ℃ and kept at the temperature for 7-9 h; after preheating, it is transferred to the extruder for extrusion blanking. The extrusion temperature is controlled at 410-450 ℃, the extrusion speed is 0.4-0.6 mm / s, and the extrusion coefficient is 1.3-1.6; online spray cooling is adopted during the extrusion process.

[0046] (3) Multi-stage homogenization treatment: The extruded billet is cut off at the head and tail and shaped, and then subjected to three-stage homogenization heat treatment. The first stage temperature is 360-380 ℃ and the holding time is 8-12 h; the second stage temperature is 440-460 ℃ and the holding time is 6-10 h; the third stage temperature is 500-520 ℃ and the holding time is 6-8 h.

[0047] (4) Isothermal multi-directional forging: The homogenized billet is quickly transferred to a forging press, and the forging anvil is preheated to 440~490℃ and held for 6~10 h to avoid the billet cooling down and causing a decrease in plasticity. In this embodiment of the invention, a "upsetting-drawing" cyclic process is adopted, and 4~6 forging passes are performed in the X, Y, and Z three-dimensional directions. The deformation in one direction is ≥45%, and the total deformation is ≥70%. Finally, the billet is upset into a disc with a diameter of Φ 95~1100 mm × 600~750 mm. Multi-directional forging can significantly refine the grains, activate non-basal plane slip, and improve the material's subsequent ring rolling deformation capability.

[0048] (5) Ring rolling: After isothermal multi-directional forging, the blank is cut and trimmed to form several ring blanks; the core of each ring blank is removed to remove the core material with a diameter of 150~250 mm, and the ring blank is prepared for ring rolling; the ring blank is placed in a heating furnace and held at 370~390 ℃ for 5~7 h, and then transferred to a ring rolling mill; the main roll and core roll of the ring rolling mill are preheated to 280~330 ℃ and held for 2~3 h, and a graphite-based lubricant is used to reduce friction; the rolling deformation is controlled at 30~50% during the ring rolling process, and after multiple rolling passes, an annular part 1 with an outer diameter of Φ2.0 m, an axial height H of 400~700 mm, and a wall thickness t0 of 30~60 mm is prepared; H and t0 are related to the target plate width B and the target thickness t f Satisfying H×t0 ≥ k×B×t f , where k is 1.1~1.2.

[0049] (6) Ring cutting and straightening: The ring part 1 is cut along the axial seam 2 by plasma cutting or mechanical cutting to obtain a single slab 3; the slab 3 is placed in a heating furnace and kept at 300~320 ℃ for 2~4 h, and then straightened by a 500~800 t pressure straightening machine 4 to ensure that the flatness error of the slab 3 is ≤2 mm / m.

[0050] (7) Wide-width rolling: The straightened slab 3 is heated to 420~440 ℃ and held for 3~5 h, and then transferred to the wide-width four-roll mill 5 for longitudinal and transverse cross rolling;

[0051] Specifically, the slab 3 is first pre-rolled along the circumferential length direction, then rotated 90° and widened by rolling along the axial height direction of the annular component 1, widening the slab 3 from 400~700 mm to not less than 2000 mm. During rolling, the slab temperature is controlled at 420~440 ℃. When the slab 3 temperature drops below 400 ℃, it is returned to the furnace for reheating to 420~440 ℃ before continuing rolling. The rolling speed is controlled at 0.2~0.4 m / s, the single-pass reduction is 5~12%, and the furnace is held for 10~30 min between passes. After 12~20 passes, the total thickness reduction is 70~90%, resulting in a slab 6 with a width of not less than 2000 mm and a thickness of 3~10 mm. The length is determined based on the annular component's unfolded length, rolling deformation, and cutting method.

[0052] (8) Subsequent heat treatment: The rolled plate 6 is cooled in stages, first immersed in hot water at 70~80 ℃ for 4~8 min, then immersed in ice water at 0~5 ℃ for 8~12 min; isothermal aging is completed at 190~220 ℃ for 12~40 h to promote the formation and stabilization of nano-precipitated phases such as β′ and LPSO-related phases, and obtain wide rare earth magnesium alloy plates.

[0053] Preferably, in step (8), vibration treatment for 8 to 25 minutes and / or deep cryogenic treatment with liquid nitrogen for 15 to 35 minutes are performed.

[0054] The rare earth magnesium alloy wide plate prepared in this embodiment of the invention is Mg-9 Gd-4 Y-1.5 Zn-0.3 Zr (wt.%), and the composition content of the plate is determined according to the actual implementation conditions.

[0055] The rare earth magnesium alloy wide plate prepared by the method of this invention has a room temperature mechanical properties of yield strength ≥ 410 MPa, ultimate tensile strength ≥ 482 MPa, and elongation ≥ 4.4%; its width is not less than 2000 mm and its thickness is 3~10 mm.

[0056] See attached document Figure 7 The figures (a) and (b) show the microstructures of the ring-rolled state at scales of 100 μm and 50 μm, respectively, while (c) and (d) show the microstructures of the cross-broad-width rolled state at scales of 100 μm and 50 μm, respectively. In (a) and (b), the LPSO phase in the ring-rolled state mainly exhibits coarse lamellar, curved strip, and local network distributions, with a certain degree of aggregation and microstructure inhomogeneity. In (c) and (d), the coarse continuous LPSO phase is subjected to longitudinal and transverse cross-shearing, resulting in breakage, elongation, and redistribution, transforming into fine strip and short rod-shaped microstructures arranged along the rolling direction. The coarse clusters are significantly reduced, and the second phase distribution is more uniform. Cross-broad-width rolling can effectively refine the microstructure, weaken local agglomeration, and improve the microstructure uniformity of the sheet.

[0057] Example 2

[0058] The method for preparing wide rare-earth magnesium alloy plates according to Embodiment 1 of the present invention includes the following steps:

[0059] (1) Ingot preparation: The materials were prepared according to the following proportions: Gd 8.5~9.5 wt.%, Y 3.5~4.5 wt.%, Zn 1.2~1.8 wt.%, Zr 0.2~0.4 (wt.%). After melting, the materials were filtered through 20 mesh, 45 mesh and 90 mesh and cooled in stages to prepare an ingot with a diameter of 650mm×1800mm. After rolling, an initial billet with a diameter of 630mm×1700mm was obtained.

[0060] (2) Extrusion blanking: The initial blank temperature is 490℃ preheated and kept at that temperature for 8 hours, the extrusion temperature of the extruder is 430℃, the extrusion speed is 0.5 mm / s, and the extrusion coefficient is 1.45;

[0061] (3) Multi-stage homogenization treatment: The first stage of the homogenization heat treatment of the extruded billet is held at 370℃ for 10 h, the second stage is held at 450℃ for 8 h, and the third stage is held at 510℃ for 7 h.

[0062] (4) Isothermal multi-directional forging: The homogenized billet is quickly transferred to the forging press, the forging anvil is preheated to 460℃ and held for 8 hours, and after 5 forging passes, the unidirectional deformation is 48%, and a Φ 1000 mm × 680 mm billet is made.

[0063] (5) Ring rolling: After the blank is slit and trimmed, a ring blank is taken. After removing the core from the ring blank, it is kept at 380 ℃ for 6 h. The preheating temperature of the roll is 300 ℃, and the ring rolling deformation is 40%, to produce a ring part 1 with an outer diameter of Φ2.0 m, a wall thickness of 45 mm, and an axial height of 500 mm. The dimensions of the ring part 1 satisfy H×t0≈500×45 mm², which can support the subsequent preparation of a plate with a width of not less than 2000 mm and a thickness of about 9 mm.

[0064] (6) Ring cutting and straightening: After the ring part 1 is cut by plasma cutting, it is kept at 310℃ for 3 h, and then straightened by pressure straightening machine 4 to obtain slab 3. The flatness error of slab 3 is 1.8 mm / m.

[0065] (7) Wide-width rolling: The rolling temperature of the slab 3 is 430 ℃, the rolling speed is 0.3 m / s, and the longitudinal and transverse cross rolling is adopted. After 14 passes of rolling, the total thickness reduction rate is about 80%, and a plate with a width of not less than 2000 mm and a thickness of about 9 mm is obtained. The length is determined according to the unfolded length of the ring part, the amount of rolling deformation and the cutting method.

[0066] (8) Subsequent heat treatment: The plate is heated by hot water at 75 ℃ for 6 min, heated by ice water at 2 ℃ for 10 min, subjected to vibration treatment for 15 min, subjected to deep cryogenic treatment with liquid nitrogen for 25 min, and subjected to isothermal aging at 200 ℃ for 24 h to obtain a wide plate of rare earth magnesium alloy 6.

[0067] The performance of the wide rare earth magnesium alloy plate prepared in the embodiments of the present invention was tested, and its room temperature yield strength was 419 MPa, its ultimate tensile strength was 479 MPa, and its elongation was 5.05%.

[0068] Example 3

[0069] The method for preparing wide rare-earth magnesium alloy plates according to Embodiment 1 of the present invention includes the following steps:

[0070] (1) Ingot preparation: The alloy composition is Gd 8.5~9.5 wt.%, Y 3.5~4.5 wt.%, Zn 1.2~1.8wt.%, Zr 0.2~0.4 (wt.%). The ingot size is Φ640 mm×1750 mm. After rolling, an initial billet of Φ620 mm×1700 mm is obtained.

[0071] (2) Extrusion and billet opening: The initial billet is preheated in a heating furnace at 480℃ for 7.5 h, the extrusion temperature of the extruder is 420℃, the extrusion speed is 0.45 mm / s, and the extrusion coefficient is 1.35;

[0072] (3) Multi-stage homogenization treatment: The extruded billet is heat-treated at the following temperatures: first stage temperature of 365℃ for 12 h, second stage temperature of 445℃ for 9 h, and third stage temperature of 505℃ for 6.5 h.

[0073] (4) Isothermal multi-directional forging: The billet after homogenization is quickly transferred to the forging press, the forging anvil is preheated to 450℃ and held for 7 hours, and forging is carried out in 4 passes with a unidirectional deformation of 45% to produce a Φ 980 mm × 650 mm billet.

[0074] (5) Ring rolling: After the blank is slit and trimmed, a ring blank is taken. After the core of the ring blank is removed, it is kept at 375 ℃ for 5.5 h. The preheating temperature of the roll is 290 ℃, and the ring rolling deformation is 35%, resulting in a ring part 1 with an outer diameter of Φ2.0 m, a wall thickness of 38 mm, and an axial height of 520 mm. This size meets the size requirements for subsequent preparation of plates with a width of not less than 2000 mm and a thickness of about 8 mm.

[0075] (6) Ring cutting and straightening: After the ring part 1 is cut by plasma cutting, it is kept at 305℃ for 3.5 h, and the flatness error of the slab 3 after being straightened by the pressure straightening machine 4 is 1.6 mm / m;

[0076] (7) Wide-width rolling: The straightened slab 3 is rolled at a temperature of 425 ℃ and a rolling speed of 0.25 m / s. It is rolled in a cross-rolling manner, and after 13 passes, the total thickness reduction rate is about 79%, resulting in a plate with a width of not less than 2000 mm and a thickness of about 8 mm. The length is determined according to the unfolded length of the ring part, the amount of rolling deformation and the cutting method.

[0077] (8) Subsequent heat treatment: The plate is kept in hot water at 70°C for 7 min, in ice water at 3°C ​​for 9 min, subjected to vibration treatment for 12 min, deep-cooled with liquid nitrogen for 20 min, and isothermal aged at 195°C for 30 h to obtain the wide rare earth magnesium alloy plate 6 of the present invention.

[0078] The performance of the wide rare earth magnesium alloy plate prepared in the embodiment of the present invention was tested. Its room temperature yield strength was 427 MPa, its ultimate tensile strength was 492 MPa, and its elongation was 5.15%.

[0079] Example 4

[0080] The method for preparing wide rare-earth magnesium alloy plates according to Embodiment 1 of the present invention includes the following steps:

[0081] (1) Ingot preparation: The alloy composition is Gd 8.5~9.5 wt.%, Y 3.5~4.5 wt.%, Zn 1.2~1.8wt.%, Zr 0.2~0.4 (wt.%), the ingot size is Φ 660 mm×1800 mm, and after rolling, a billet of Φ635 mm×1720 mm is obtained;

[0082] (2) Extrusion blanking: The blank is preheated at 500℃ for 9 h, the extrusion temperature of the extruder is 440℃, the extrusion speed is 0.55 mm / s, and the extrusion coefficient is 1.5;

[0083] (3) Multi-stage homogenization treatment: The extruded billet is heat-treated at the first stage temperature of 375℃ for 9 h, the second stage temperature of 455℃ for 7 h, and the third stage temperature of 515℃ for 6 h.

[0084] (4) Isothermal multi-directional forging: The billet after homogenization heat treatment is quickly transferred to the forging press, the forging anvil is preheated to 480℃ and held for 9 hours, 6 forging passes, unidirectional deformation of 50%, to make a Φ 1050 mm × 700 mm billet.

[0085] (5) Ring rolling: After the blank is slit and trimmed, a ring blank is taken. After the core of the ring blank is removed, it is kept at 385 ℃ for 6.5 h. The preheating temperature of the roll is 320 ℃, and the ring rolling deformation is 45%, resulting in a ring part 1 with an outer diameter of Φ2.0 m, a wall thickness of 55 mm, and an axial height of 420 mm. The dimensions of the ring part 1 meet the dimensional requirements for subsequent preparation of a plate with a width of not less than 2000 mm and a thickness of about 8 mm.

[0086] (6) Ring straightening: The ring part 1 is axially cut to obtain a single slab blank. The slab blank is kept at 315℃ for 2.5 h. After straightening by the pressure straightening machine 4, the flatness error is 1.5 mm / m.

[0087] (7) Wide-width rolling: The straightened slab 3 is heated to 435 ℃ and held for 4 h. It is rolled longitudinally and transversely using a wide-width four-roll mill 5 at a rolling speed of 0.35 m / s. After 16 passes of rolling, the total thickness reduction rate is about 85%, and a plate with a width of not less than 2000 mm and a thickness of about 8 mm is obtained. The length is determined according to the unfolded length of the ring part, the amount of rolling deformation and the cutting method.

[0088] (8) Subsequent heat treatment: The plate was kept in hot water at 80°C for 5 min, kept in ice water at 0°C for 11 min, subjected to vibration treatment for 20 min, deep cooled with liquid nitrogen for 30 min, and isothermal aged at 210°C for 18 h to prepare the rare earth magnesium alloy plate 6 of the present invention.

[0089] The rare earth magnesium alloy sheet prepared according to the embodiments of the present invention was tested for performance, and its room temperature yield strength was 415 MPa, ultimate tensile strength was 478 MPa, and elongation was 6.9%.

[0090] The rare earth magnesium alloy sheet prepared in this embodiment of the invention has a fully deformed microstructure at low magnification, without cracks, folds, or mixed crystal structures, and meets the Class A standard in ultrasonic flaw detection.

[0091] See attached document Figure 8 The rare-earth magnesium alloy cross-width rolled plates prepared in Examples 1 to 4 of this invention all exhibit high tensile strength, with peak engineering stresses of approximately 480–495 MPa. The strength levels of the different examples are relatively similar, but the elongation after fracture varies to some extent. Example 4 shows an engineering strain after fracture close to 7%, exhibiting good plasticity while maintaining a tensile strength of approximately 485–490 MPa. This indicates that the composition design and cross-width rolling process can achieve a synergistic match between high strength and good plasticity in rare-earth magnesium alloy plates.

[0092] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wide sheet of rare earth magnesium alloy, characterized in that, The plate composition and content are: Gd 8.5-9.5 wt.%, Y 3.5-4.5 wt.%, Zn 1.2-1.8 wt.%, Zr 0.2-0.4 wt.%; the balance is Mg and unavoidable impurities, with a total impurity content ≤0.1 wt.%; the plate has at least one planar dimension of not less than 2000 mm and a thickness of 3-10 mm.

2. The wide sheet metal of rare earth magnesium alloy according to claim 1, characterized in that, The room temperature mechanical properties of the rare earth magnesium alloy wide plate are: yield strength ≥ 410 MPa, ultimate tensile strength ≥ 470 MPa, and elongation ≥ 4.4%.

3. The method for preparing a wide rare earth magnesium alloy plate according to claim 1, characterized in that, Using Mg, Gd, Y, Zn, and Zr as alloying raw materials, rare earth magnesium alloy wide plates are obtained through ingot preparation, pre-homogenization before extrusion, extrusion blanking, multi-stage homogenization treatment, isothermal multi-directional forging, ring rolling, ring straightening, cross-width rolling, and heat treatment of the rolled plate according to the specified proportions.

4. The method for preparing a wide rare earth magnesium alloy plate according to claim 3, characterized in that, Includes the following steps; (1) Ingot preparation: Magnesium alloy ingots with Mg, Gd, Y, Zn and Zr as alloy system raw materials are prepared by multi-stage forced filtration and graded cooling process. The ingot mold specifications are Φ≥650 mm and height≥1800 mm. The initial billet is obtained after rolling and flaw detection. (2) Pre-homogenization and extrusion blanking: The initial blank is placed in a heating furnace and preheated at 480-500 ℃ for 7-9 h. After preheating, it is transferred to the extruder for extrusion blanking. (3) Three-stage homogenization treatment: After the extruded billet is shaped, it is subjected to three-stage homogenization heat treatment at different temperatures. The heat treatment temperature is 360~520 ℃, and the temperature of each stage increases by 20~80 ℃. The holding time of each stage is 6~20 h. (4) Isothermal multi-directional forging: The billet after homogenization heat treatment is transferred to a forging press and isothermal multi-directional forging to form a cake. The preheating temperature of the forging anvil is 440~490 ℃, the preheating time is 6~10 h, and 4~6 forging passes are performed in the three-dimensional X, Y and Z directions. The deformation in one direction is ≥45%. (5) Ring rolling: The blank is cut and trimmed to form several ring blanks. After core removal, the individual ring blanks are rolled on a ring rolling mill. Before ring rolling, the blank is kept at 370~390℃ for 5~7 h, the roll preheating temperature is 280~330℃, and the ring rolling deformation is 30~50%, to obtain a ring part with an outer diameter of Φ2000 mm, an axial height H of 400~700 mm, and a wall thickness t0 of 30~60 mm. (6) Ring cutting and straightening: the ring is cut along the axial direction, kept at 300-320 ℃ for 2-4 h, and straightened by a pressure straightening machine to obtain a slab; (7) Wide-width rolling: The straightened slab is subjected to cross-width rolling at a rolling temperature of 420~440 ℃ and a rolling speed of 0.2~0.4 m / s. After 12~20 passes, the total thickness reduction rate is 70~90%, and at least one plate with a planar dimension of not less than 2000 mm and a thickness of 3~10 mm is obtained. (8) Subsequent heat treatment: the rolled plate is subjected to at least one of the following: graded cooling, vibration treatment, and deep cryogenic treatment, and then isothermal aging treatment to prepare wide rare earth magnesium alloy plates.

5. The method for preparing a wide rare-earth magnesium alloy plate according to claim 4, characterized in that, In step (1), the multi-stage forced filtration uses 20-90 mesh metal filter screens, ceramic filter sheets or composite filter components that are resistant to magnesium alloy melt corrosion, and the warp and weft lines of adjacent filter screens are at 45°; the staged cooling uses the outer wall of the mold, cooling jacket or indirect cooling channel; the initial billet size is Φ≥630 mm, height≥1700 mm, and the single-sided cutting amount is 8~12 mm.

6. The method for preparing a wide rare-earth magnesium alloy plate according to claim 4, characterized in that, In step (2), the preheating temperature is 470~510 ℃ and the preheating time is 7~9 h; the extrusion process adopts online spray quenching and cooling, the extrusion temperature is 410~450 ℃, the extrusion speed is 0.4~0.6 mm / s, and the extrusion coefficient is 1.3~1.

6.

7. The method for preparing a wide rare-earth magnesium alloy plate according to claim 4, characterized in that, In step (4), the isothermal multi-directional forging includes 3 to 4 upsetting-drawing cycles to obtain a blank with a size of Φ 950 to 1100 mm and a thickness of 600 to 750 mm.

8. The method for preparing a wide rare-earth magnesium alloy plate according to claim 4, characterized in that, In step (5), the ring rolling process adopts online induction heating, the ring rolling lubricant is graphite-based lubricant, and the core material removed by the core removal process has a diameter of 150~250 mm, resulting in an annular part with an outer diameter of Φ 2000 mm, an axial height H of 400~700 mm, and a wall thickness t0 of 30~60 mm.

9. The method for preparing a wide rare-earth magnesium alloy plate according to claim 4, characterized in that, In step (6), the ring is cut by plasma cutting or mechanical cutting, the straightening pressure is 500~800 t, and the flatness error of the slab is ≤2mm / m.

10. The method for preparing a wide rare-earth magnesium alloy plate according to claim 4, characterized in that, In step (8), the graded cooling first involves immersing the rolled plate in hot water at 70-80℃ for 4-8 minutes, then transferring it to ice water at 0-5℃ for 8-12 minutes; the vibration treatment time is 8-25 minutes; the cryogenic treatment uses liquid nitrogen and the treatment time is 15-35 minutes; the isothermal aging temperature is 190-220℃ and the holding time is 12-40 hours.

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