Method and device for preparing rare earth magnetic alloy powder through gaseous calcium reduction

Abstract

The invention relates to a method and device for preparing rare earth magnetic alloy powder through gaseous calcium reduction. The method comprises the following steps: respectively placing rare earth magnetic alloy precursor powder and a calcium source in a first area and a second area of a vacuum container; and performing heat treatment to obtain the rare earth magnetic alloy powder. The first area and the second area of the vacuum container are separated by a porous partition plate or a net-shaped partition plate. According to the method, the precursor in the powder form is used as a raw material, the rare earth magnetic alloy precursor powder and the calcium source are placed in the first area and the second area which are spatially independent and allow gas circulation respectively, the rare earth magnetic alloy precursor powder is reduced through heat treatment and gaseous calcium, and the reduction efficiency and the utilization rate of the calcium source are remarkably improved; the residue of the calcium source on the surface of the rare earth magnetic alloy powder is reduced, and the waste of the calcium source is reduced.

Description

Technical Field

[0001] This invention relates to the field of rare earth alloy material preparation technology, specifically to the reduction preparation of rare earth magnetic alloy powder, and more particularly to a method and apparatus for the reduction preparation of rare earth magnetic alloy powder using gaseous calcium. Background Technology

[0002] Rare earth magnetic alloy powder is the core precursor for preparing high-performance rare earth permanent magnet materials, and its preparation process directly affects the final performance and production cost of the permanent magnet materials.

[0003] The mainstream industrial method for preparing this alloy is the calcium thermal reduction method. Traditional processes are mostly static reduction methods, where the raw materials and calcium are mixed uniformly and then placed in a reactor, where the reduction reaction is completed under high temperature and vacuum. In this static reduction process, the raw material powder and calcium are in static, stacked contact, resulting in poor contact uniformity and low reaction efficiency. To ensure complete reduction, excessive calcium is added, which not only wastes calcium and increases preparation costs but also generates a large amount of calcium oxide as a byproduct that adheres to the product surface, requiring an additional acid washing process for removal. This increases the complexity of the process and production time, while also generating waste acid treatment, further increasing environmental costs and overall energy consumption.

[0004] CN108274016A discloses a method for directly preparing samarium-iron alloy powder by spray thermal decomposition and reduction. The method includes first using a mixed aqueous solution of samarium salt and iron salt as a spray precursor solution, preparing spherical samarium-iron composite oxide by ultrasonic spray thermal decomposition, and then using hydrogen pre-reduction followed by calcium reduction to obtain samarium-iron alloy, thereby saving the amount of calcium used.

[0005] CN111014714A discloses a method for preparing samarium-iron alloy powder that integrates spray thermal decomposition and iron oxide reduction in one step. The method includes using samarium salts, iron salts, high-melting-point salts, and soluble substances that are reducing at high temperatures or decompose at high temperatures to produce reducing substances as spray precursor solutions. Spherical particles with intercalated Sm₂O₃ and α-Fe structures are prepared using ultrasonic spray thermal decomposition, followed by calcium reduction diffusion to obtain the samarium-iron alloy. This method significantly reduces the amount of calcium used and the corresponding calcium reduction diffusion time.

[0006] CN110172614A discloses a method for preparing samarium-cobalt alloys, comprising the following steps: first, anhydrous samarium halide, metallic cobalt or anhydrous cobalt halide, reducing agent, and other chemical components are prepared in a certain proportion; the raw materials are mixed and placed in a crucible, and then placed in a vacuum furnace for reaction. This method utilizes metallic calcium or calcium salts to reduce rare earth samarium halides and interact with the transition metal cobalt to directly produce rare earth samarium-cobalt alloys under conditions higher than the alloy melting point. Because the density of the reaction slag calcium halide is much lower than that of the samarium-cobalt alloy, and no oxygen is introduced, it floats on the top layer of the molten slag after melting, resulting in obvious stratification, good impurity separation, and a metal recovery rate greater than 98%.

[0007] Therefore, it is of great significance to provide a method for preparing rare earth magnetic alloy powder with high calcium utilization, low calcium and oxygen residue, and high production efficiency. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method and apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction. This invention uses a powdered precursor as raw material, placing the rare earth magnetic alloy precursor powder and a calcium source in separate, spatially independent regions, a first region and a second region, allowing gas flow. Through heat treatment, gaseous calcium is used to reduce the rare earth magnetic alloy precursor powder, significantly improving reduction efficiency and calcium source utilization, reducing calcium source residue on the surface of the rare earth magnetic alloy powder, and minimizing calcium source waste.

[0009] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, the method comprising: Rare earth magnetic alloy precursor powder and calcium source are placed in the first and second regions of a vacuum container, respectively; heat treatment is performed to obtain the rare earth magnetic alloy powder; the first and second regions of the vacuum container are separated by a porous partition or a mesh partition, the maximum pore size of the porous partition or mesh partition being smaller than the minimum particle size of the rare earth magnetic alloy precursor powder and the calcium source; the rare earth magnetic alloy precursor powder includes samarium precursor powder, cobalt precursor powder and / or iron precursor powder.

[0010] This invention places rare earth magnetic alloy precursor powder and calcium source in two spatially independent regions, a first region and a second region, which allow gas flow. During heat treatment, the calcium source is heated and vaporized, diffuses from the second region to the first region, and uses gaseous calcium to reduce the rare earth magnetic alloy precursor powder. This avoids direct contact between the rare earth magnetic alloy precursor powder and the calcium source, and significantly reduces the residue of calcium source on the surface of the rare earth magnetic alloy powder.

[0011] Furthermore, in this invention, the precursor exists in powder form, which has a large specific surface area, which is beneficial for capturing gaseous calcium. The contact effect between gaseous calcium and rare earth magnetic alloy precursor powder is better, and the reduction is more complete and thorough, improving the reduction efficiency and calcium utilization rate. It also significantly reduces calcium loss caused by the direct condensation of gaseous calcium. The unreacted excess calcium source can be used in subsequent production, reducing the waste of calcium source and significantly reducing costs.

[0012] Preferably, the calcium source includes calcium metal.

[0013] Preferably, the precursor powder of samarium is composed of Sm2O3 and / or Sm(OH)3.

[0014] Preferably, the precursor powder of cobalt is made of any one or a combination of at least two of Co, CoO, Co3O4 or Co(OH)2.

[0015] Preferably, the precursor powder of iron is composed of any one or a combination of at least two of Fe, Fe2O3, Fe3O4 or Fe(OH)3.

[0016] Preferably, the average particle size of the rare earth magnetic alloy precursor powder is above 150 μm.

[0017] Preferably, the mass ratio of the rare earth magnetic alloy precursor powder to the calcium source is 1:(0.2~1).

[0018] Preferably, the vacuum level of the vacuum container is 10. -3 Pa or above.

[0019] Preferably, the heat treatment temperature is 600℃~850℃.

[0020] Preferably, the heat treatment time is 1 hour to 4 hours.

[0021] Preferably, the heat treatment process further includes stirring the rare earth magnetic alloy precursor powder.

[0022] Preferably, after the heat treatment is completed, the rare earth magnetic alloy powder is further cooled.

[0023] Secondly, the present invention provides an apparatus for use in the method for preparing rare earth magnetic alloy powder by gaseous calcium reduction as described in the first aspect. The apparatus includes: a cavity, wherein at least one heating system is disposed on the inner wall of the cavity; an inner cylinder, which is disposed through the cavity and extends at both ends outside the cavity; a container, which is fixed inside the inner cylinder by a fixing member and corresponds to the heating system; the container is divided into a first region and a second region by a porous partition or a mesh partition, wherein the first region and the second region are spatially independent and gas flow is maintained between the first region and the second region; and a gas pipe, one end of which is connected to the container and the other end is connected to a vacuum pump or a gas source.

[0024] The device provided by this invention is used to prepare rare earth magnetic alloy powder by gaseous calcium reduction. The cavity is equipped with multiple heating systems that can be set up according to the preparation needs to realize the mass production and differentiated preparation of rare earth magnetic alloy powder. The container is connected to a gas pipe, and a vacuum pump or gas source is connected to the gas pipe to achieve precise control of the gas environment inside the container.

[0025] Preferably, the device further includes at least two support parts, each support part including a rotary bearing, which is nested with both ends of an inner cylinder extending outside the cavity, thereby driving the inner cylinder to rotate.

[0026] Preferably, the device further includes an air-cooling system, which is disposed adjacent to the heating system on the inner wall of the cavity.

[0027] Preferably, the inner wall of the first region of the container is provided with a plurality of turning plates, the length direction of the turning plates is consistent with the axial direction of the inner cylinder, and the angle between the height direction and the inner wall of the container is 30° to 45°.

[0028] Preferably, along the axial direction of the inner cylinder, an end cap is provided on one side surface of the container, and a connecting hole is provided on the other side surface opposite to the end cap, the connecting hole being connected to the gas pipe of the vacuum pump.

[0029] Preferably, in the container, a porous partition or a mesh partition is arranged along the axial direction of the inner cylinder.

[0030] Preferably, in the container, the second region is enclosed by a porous partition or a mesh partition to form a cage-like cavity, which is fixedly connected to the end cap.

[0031] Preferably, during the heat treatment process, the rotation speed of the inner cylinder is 15 r / min to 30 r / min.

[0032] Preferably, during the cooling process, the rotation speed of the inner cylinder is 5 r / min to 10 r / min.

[0033] Compared with the prior art, the present invention has the following beneficial effects: This invention uses a powdered precursor as raw material. The rare earth magnetic alloy precursor powder and the calcium source are placed in a first region and a second region that are spatially independent and allow gas flow. Through heat treatment, the rare earth magnetic alloy precursor powder is reduced by gaseous calcium, which significantly improves the reduction efficiency and the utilization rate of the calcium source, reduces the calcium source residue on the surface of the rare earth magnetic alloy powder, and reduces the waste of calcium source. Attached Figure Description

[0034] Figure 1 This is a cross-sectional schematic diagram of the apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction as provided in Example 1.

[0035] Figure 2 This is a schematic cross-sectional view of the container in the apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction provided in Example 1.

[0036] Figure 3 This is a schematic diagram of the cross-sectional structure of the container in the apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction provided in Example 1.

[0037] Figure 4 This is a cross-sectional schematic diagram of the apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction as provided in Example 3.

[0038] Figure 5 This is a schematic diagram of the cross-sectional structure of the container in the apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction provided in Example 3.

[0039] Figure 6 The images show the XRD patterns of the SmCo5 powders prepared in Example 1 and Comparative Example 1.

[0040] Figure 7 These are the MH curves of the SmCo5 powders prepared in Example 1 and Comparative Example 1.

[0041] Among them, 1-cavity; 2-heating system; 3-cooling system; 4-inner cylinder; 5-support part; 6-rotary bearing; 7-container; 71-end cap; 721-cage-shaped cavity; 722-stainless steel mesh; 73-tilting plate; 74-connection hole; 8-air pipe; 9-vacuum pump; 10-air source. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0043] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0044] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0046] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0047] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0049] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0050] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0051] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0052] In this invention, unless otherwise specified, it is assumed that the experiments are conducted at room temperature or a temperature conventionally set in the art. "Room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this invention, room temperature refers to 20°C to 30°C.

[0053] In one specific embodiment, the present invention provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, the method comprising: Rare earth magnetic alloy precursor powder and calcium source are placed in the first and second regions of a vacuum container, respectively; heat treatment is performed to obtain the rare earth magnetic alloy powder; the first and second regions of the vacuum container are separated by a porous partition or a mesh partition, the maximum pore size of the porous partition or mesh partition being smaller than the minimum particle size of the rare earth magnetic alloy precursor powder and the calcium source; the rare earth magnetic alloy precursor powder includes samarium precursor powder, cobalt precursor powder and / or iron precursor powder.

[0054] This invention places rare-earth magnetic alloy precursor powder and a calcium source in two spatially independent regions, a first region and a second region, respectively, allowing gas flow. During heat treatment, the calcium source vaporizes upon heating and diffuses from the second region to the first region. The gaseous calcium reduces the rare-earth magnetic alloy precursor powder, avoiding direct contact between the precursor powder and the calcium source and significantly reducing calcium source residue on the surface of the rare-earth magnetic alloy powder. Therefore, the rare-earth magnetic alloy powder prepared by this invention only requires washing with water to remove surface impurities, eliminating the need for acid washing and avoiding the problem of waste acid disposal.

[0055] Furthermore, in this invention, the precursor exists in powder form, which has a large specific surface area, which is beneficial for capturing gaseous calcium. The contact effect between gaseous calcium and rare earth magnetic alloy precursor powder is better, and the reduction is more complete and thorough, improving the reduction efficiency and calcium utilization rate. It also significantly reduces calcium loss caused by the direct condensation of gaseous calcium. The unreacted excess calcium source can be used in subsequent production, reducing the waste of calcium source and significantly reducing costs.

[0056] In this invention, the material of the porous partition or mesh partition is not particularly limited; for example, it can be stainless steel, graphite, or ceramic.

[0057] In some embodiments, the calcium source includes calcium metal.

[0058] The calcium metal used in the method provided by this invention does not require high-purity treatment. Because the method involves heating a calcium source to form gaseous calcium, which is then used to reduce rare-earth magnetic alloy precursor powder, there are no strict requirements on the purity of the calcium metal in the calcium source, significantly reducing the cost of the calcium source.

[0059] The rare earth magnetic alloy described in this invention includes SmCo5 or Sm2Fe. 17 Rare earth magnetic alloys, the rare earth magnetic alloy precursor powders include oxides or hydroxides of Sm, and elemental powders, oxide powders or hydroxide powders of Co and Fe.

[0060] In some embodiments, the samarium precursor powder is made of Sm2O3 and / or Sm(OH)3.

[0061] In some embodiments, the material of the cobalt precursor powder includes any one or a combination of at least two of Co, CoO, Co3O4 or Co(OH)2. Typical but non-limiting combinations include combinations of CoO and Co3O4, combinations of Co(OH)2 and CoO, or combinations of Co3O4 and Co(OH)2.

[0062] In some embodiments, the precursor powder of iron comprises any one or a combination of at least two of Fe, Fe2O3, Fe3O4 or Fe(OH)3. Typical but non-limiting combinations include combinations of Fe2O3 and Fe3O4, combinations of Fe(OH)3 and Fe2O3, or combinations of Fe3O4 and Fe(OH)3.

[0063] In some embodiments, the average particle size of the rare earth magnetic alloy precursor powder is above 150 μm, for example, it can be 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, or 300 μm. In this invention, the average particle size of the rare earth magnetic alloy precursor powder is above 150 μm, and there are large gaps between the powder particles, which is conducive to the full entry of gaseous calcium into the powder particles, improving the rare earth magnetic alloy precursor powder's ability to capture gaseous calcium, promoting the reduction reaction between gaseous calcium and the rare earth magnetic alloy precursor powder, and making the reaction more complete and thorough.

[0064] In some embodiments, the mass ratio of the rare earth magnetic alloy precursor powder to the calcium source is 1:(0.2~1), for example, it can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:1, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1.

[0065] In some embodiments, the vacuum level of the vacuum container is 10. -3 Pa or higher, for example, 1×10 -4 Pa, 2×10 -4 Pa, 3×10 -4 Pa, 4×10 -4 Pa, 5×10 -4 Pa, 6×10 -4 Pa, 7×10 -4 Pa, 8×10 -4 Pa, 9×10 -4 Pa or 1×10 -3 Pa.

[0066] In some embodiments, the heat treatment temperature is 600°C to 850°C, for example, it can be 600°C, 650°C, 700°C, 750°C, 800°C or 850°C.

[0067] In some embodiments, the heat treatment time is 1h to 4h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.

[0068] In some embodiments, the heat treatment process further includes stirring the rare earth magnetic alloy precursor powder. In the method provided by this invention, by stirring the rare earth magnetic alloy precursor powder during the heat treatment process, the rare earth magnetic alloy precursor powder is repeatedly lifted and scattered, resulting in a dispersed state. Gaseous calcium reacts with the dynamic rare earth magnetic alloy precursor powder, greatly increasing its contact area and collision probability with calcium vapor, thus enhancing the mass transfer process and making the reduction reaction faster and more thorough.

[0069] In some embodiments, after the heat treatment is completed, the rare earth magnetic alloy powder is further cooled. In this invention, the cooling method includes air cooling to rapidly reduce the temperature of the alloy powder.

[0070] In another specific embodiment, the present invention provides an apparatus for use in the method for preparing rare earth magnetic alloy powder by gaseous calcium reduction as described in one of the foregoing specific embodiments. The apparatus includes: a cavity, the inner wall of which is provided with at least one heating system; an inner cylinder, which is disposed through the cavity and extends at both ends outside the cavity; a container, which is fixed inside the inner cylinder by a fixing member and corresponds to the heating system; the container is divided into a first region and a second region by a porous partition or a mesh partition, the first region and the second region being spatially independent and maintaining gas flow between the first region and the second region; and a gas pipe, one end of which is connected to the container and the other end of which is connected to a vacuum pump or a gas source.

[0071] The device provided by this invention is used to prepare rare earth magnetic alloy powder by gaseous calcium reduction. The cavity is equipped with multiple heating systems that can be set up according to the preparation needs to realize the mass production and differentiated preparation of rare earth magnetic alloy powder. The container is connected to a gas pipe, and a vacuum pump or gas source is connected to the gas pipe to achieve precise control of the gas environment inside the container.

[0072] In some embodiments, the device further includes at least two support portions, each including a rotary bearing. The rotary bearing is nested at both ends of an inner cylinder extending outside the cavity, driving the inner cylinder to rotate. In the device provided by this invention, the inner cylinder is supported by the support portions, and its rotation is achieved by the rotary bearings. Since the container is fixed inside the inner cylinder, the rotation of the inner cylinder drives the container to rotate, thus agitating the rare-earth magnetic alloy precursor powder and the calcium source. This dynamic reaction process avoids problems such as localized overheating or uneven reaction, which is beneficial for obtaining samarium-iron alloy products with more uniform composition and particle size.

[0073] In this invention, the method of fixing the container inside the inner cylinder is not particularly limited. For example, the container can be fixed by guide rails and limiting parts, or by flanges and gaskets.

[0074] In some embodiments, the apparatus further includes an air-cooling system disposed adjacent to the heating system on the inner wall of the cavity. After heat treatment, the container is rapidly cooled using the air-cooling system.

[0075] In some embodiments, the inner wall of the first region of the container is provided with a plurality of tilting plates, for example, 2, 3, 4, 5, 10, 20, 50, 100 or 200. The length direction of the tilting plates is consistent with the axial direction of the inner cylinder, and the angle between the height direction and the inner wall of the container is 30° to 45°, for example, 30°, 31°, 33°, 35°, 37°, 39°, 41°, 43° or 45°. The height of the tilting plates is not specifically limited, but preferably does not exceed 1 / 4 of the radial dimension of the container along the inner cylinder.

[0076] During the rotation of the container with the inner cylinder, the rare earth magnetic alloy precursor powder is repeatedly lifted and scattered by the tipping plate, resulting in a dispersed state. This significantly increases the contact area and collision probability between the powder and calcium vapor, enhancing the mass transfer process and making the reduction reaction faster and more thorough, thereby improving production efficiency and calcium utilization. To improve the tipping effect of the tipping plate, its surface can be sandblasted to increase its roughness, thereby increasing the rotational capacity carrying the rare earth magnetic alloy precursor powder and enhancing its ability to lift and scatter the powder.

[0077] In some embodiments, an end cap is provided on one side surface of the container along the axial direction of the inner cylinder, and a connection hole is provided on the opposite side surface of the end cap, the connection hole being connected to the gas pipe of the vacuum pump.

[0078] An end cap is provided on one side of the container for feeding rare earth magnetic alloy precursor powder and calcium source. A connection hole is provided on the other side. When connected to a vacuum pump, the container can be evacuated; when connected to a gas source, it can be used to replace and clean the internal gas of the container with inert gas. In this invention, the connection method between the gas pipe and the vacuum pump and gas source is not specifically limited. For example, a three-way valve can be used to connect the gas pipe to both the vacuum pump and the gas source simultaneously.

[0079] In some embodiments, the container has a porous or mesh partition arranged axially along the inner cylinder.

[0080] In some embodiments, in the container, the second region is enclosed by a porous or mesh partition to form a cage-like cavity, which is fixedly connected to the end cap.

[0081] In the device provided by this invention, the division between the first region and the second region can be configured as needed. When the second region is enclosed by a porous partition or a mesh partition to form a cage-like cavity, it can be fixed at a position corresponding to the inner wall of the end cap and the axis of the inner cylinder, so that the relative position of the cage-like cavity remains unchanged during the rotation of the inner cylinder. Furthermore, at least one porous partition or mesh partition of the cage-like cavity can be opened for feeding.

[0082] In some embodiments, during the heat treatment process, the rotation speed of the inner cylinder is 15 r / min-30 r / min, for example, it can be 15 r / min, 17 r / min, 19 r / min, 20 r / min, 22 r / min, 24 r / min, 26 r / min, 28 r / min or 30 r / min. By adjusting the rotation speed of the inner cylinder, the rare earth magnetic alloy precursor powder is kept at a suitable frequency of being lifted and scattered, achieving sufficient dynamic contact with gaseous calcium while ensuring sufficient reaction time for a complete reaction.

[0083] In some embodiments, during the cooling process, the inner cylinder rotates at a speed of 5 r / min to 10 r / min, for example, 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min, or 10 r / min. Maintaining a low rotation speed of the inner cylinder during cooling assists in uniform heat dissipation and, in conjunction with the air-cooling system, achieves rapid cooling.

[0084] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0085] Example 1 This embodiment provides an apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction. A cross-sectional schematic diagram of the apparatus is shown below. Figure 1 As shown, the device includes: a cavity 1, the inner wall of which is provided with a heating system 2 and a cooling system 3; an inner cylinder 4, which penetrates the cavity 1 and extends to both ends outside the cavity 1; a support 5 that nests the two ends of the inner cylinder 4 through a rotary bearing 6, thereby rotating the inner cylinder 4; and a container 7, which is a cylinder coaxial with the inner cylinder, fixed inside the inner cylinder 4 by a flange 8, and positioned to correspond with the heating system 2. Figure 2 As shown, the container 7 includes an end cap 71. A cage-shaped cavity 721, formed by a graphite porous partition, is disposed on the inner wall of the end cap 71 at a position corresponding to the axis of the inner cylinder. The cage-shaped cavity 721 is fixed to the end cap 71 by bolts, and the surface opposite to the end cap 71 can be opened. Figure 3 As shown, the inner wall of container 7 is also provided with 5 tilting plates 73. The length direction of the tilting plates 73 is consistent with the axial direction of the inner cylinder 4, the height direction makes an angle of 35° with the inner wall of container 7, and the height is 1 / 3 of the radius of container 7. The bottom of container 7 is also provided with a connecting hole 74, which is connected to one end of the air pipe 8. The other end of the air pipe 8 is connected to the vacuum pump 9 and the air source 10 through a three-way valve.

[0086] Since Sm is easily burned at high temperatures, Sm(OH)3 powder with a purity ≥99.9% and an average particle size of 160 μm was mixed with Co(OH)2 powder with a purity ≥99.9% and an average particle size of 170 μm in a V-type mixer for 3 hours, with an Sm excess of 30% and an Sm:Fe atomic ratio of 1.3:5, to obtain a uniform rare earth magnetic alloy precursor powder. Then, the rare earth magnetic alloy precursor powder and metallic calcium were placed in container 7 at a mass ratio of 1:1, with the metallic calcium placed inside the cage-shaped cavity 721 and the rare earth magnetic alloy precursor powder placed outside the cage-shaped cavity 721. Container 7 was placed in the inner cylinder 4, corresponding to the heating system 2. Using a vacuum pump 9 in conjunction with a gas source 10, container 7 was evacuated and then purged with argon gas three times to remove air from container 7. Then, container 7 was evacuated to a vacuum level of 6 × 10⁻⁶. -4Pa. The rotation speed of the inner cylinder 4 was set to 30 r / min, the heating system 2 was started, and the temperature was raised to 600℃ for 4 hours. After the heat treatment, the heating system 2 was turned off, the rotation speed of the inner cylinder was adjusted to 10 r / min, the air cooling system 3 was started, and the temperature of the inner cylinder was rapidly cooled until it dropped below 50℃. Argon gas was then introduced into the container 7 to atmospheric pressure using the gas source 10. The prepared SmCo5 powder was taken out and placed in deionized water. CaO was dissolved and removed by mechanical stirring and ultrasonic-assisted cleaning. After vacuum drying, pure SmCo5 powder was obtained.

[0087] Example 2 This embodiment provides an apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction, and the apparatus is the same as that in Embodiment 1.

[0088] This embodiment also provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, including: Since Sm is easily burned at high temperatures, Sm₂O₃ powder with a purity ≥99.9% and an average particle size of 155 μm was mixed with Fe₂O₃ powder with a purity ≥99.9% and an average particle size of 170 μm in a V-type mixer for 4 hours, with an Sm excess of 30% and an Sm:Fe atomic ratio of 2.6:17, to obtain a uniform rare-earth magnetic alloy precursor powder. Then, the rare-earth magnetic alloy precursor powder and metallic calcium were placed in container 7 at a mass ratio of 1:0.8, with the metallic calcium placed inside the cage-shaped cavity 721 and the rare-earth magnetic alloy precursor powder placed outside the cage-shaped cavity 721. Container 7 was placed in the inner cylinder 4, corresponding to the heating system 2. Using a vacuum pump 9 in conjunction with a gas source 10, container 7 was evacuated and then purged with argon gas three times to remove air from container 7. Then, container 7 was evacuated to a vacuum level of 8 × 10⁻⁶. -4 Pa. The rotation speed of the inner cylinder 4 was set to 15 r / min, and the heating system 2 was started to raise the temperature to 800℃ for 2 hours. After the heat treatment, the heating system 2 was turned off, the rotation speed of the inner cylinder was adjusted to 5 r / min, the air cooling system 3 was started, and the temperature of the inner cylinder was rapidly cooled until it dropped below 50℃. Then, argon gas was introduced into the container 7 using the gas source 10 to atmospheric pressure, and the prepared Sm2Fe was taken out. 17 The powder was placed in deionized water and subjected to mechanical stirring and ultrasonic-assisted cleaning to dissolve and remove CaO. After vacuum drying, pure Sm₂Fe₂ was obtained. 17 powder.

[0089] Example 3 This embodiment provides an apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction, such as... Figure 4 and Figure 5As shown, the device is the same as in Embodiment 1 except that the container 7 is a cuboid structure and the container 7 is divided into a first region and a second region by a stainless steel mesh 722 arranged along the axial direction of the inner cylinder. The first region has four turning plates 73 arranged on its inner wall. The length direction of the turning plates 73 is consistent with the axial direction of the inner cylinder 4, the height direction makes an angle of 45° with the inner wall of the container 7, and the height is 1 / 2 of the radius of the container 7.

[0090] This embodiment also provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, including: Since Sm is easily burned at high temperatures, Sm₂O₃ powder with a purity ≥99.9% and an average particle size of 150 μm is mixed with Fe powder with a purity ≥99.9% and an average particle size of 155 μm in a V-type mixer for 4 hours, with an Sm excess of 30% and an Sm:Fe atomic ratio of 2.6:17, to obtain a uniform rare earth magnetic alloy precursor powder. Then, the rare earth magnetic alloy precursor powder and metallic calcium are placed in container 7 at a mass ratio of 1:0.2, with the metallic calcium placed on the side without the tilting plate 73 and the rare earth magnetic alloy precursor powder placed on the side with the tilting plate 73. Container 7 is placed in inner cylinder 4, corresponding to heating system 2. Using vacuum pump 9 and gas source 10, container 7 is evacuated and then purged with argon gas three times to remove air from container 7. Then, container 7 is evacuated to 10... -3 Pa. The rotation speed of the inner cylinder 4 was set to 20 r / min, and the heating system 2 was started to raise the temperature to 850℃ for 4 hours. After the heat treatment, the heating system 2 was turned off, the rotation speed of the inner cylinder was adjusted to 10 r / min, the air cooling system 3 was started, and the temperature of the inner cylinder was rapidly cooled until it dropped below 50℃. Then, argon gas was introduced into the container 7 using the gas source 10 to atmospheric pressure, and the prepared Sm2Fe was taken out. 17 The powder was placed in deionized water and subjected to mechanical stirring and ultrasonic-assisted cleaning to dissolve and remove CaO. After vacuum drying, pure Sm₂Fe₂ was obtained. 17 powder.

[0091] Example 4 This embodiment provides an apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction, and the apparatus is the same as that in Embodiment 1.

[0092] This embodiment also provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, which is the same as in Example 1 except that the heat treatment temperature is 550°C.

[0093] Example 5 This embodiment provides an apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction, and the apparatus is the same as that in Embodiment 1.

[0094] This embodiment also provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, which is the same as in Example 1 except that the heat treatment temperature is 900℃.

[0095] Example 6 This embodiment provides an apparatus for preparing rare earth magnetic alloy powder by gaseous calcium reduction, and the apparatus is the same as that in Embodiment 1.

[0096] This embodiment also provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction. Except that the average particle size of the rare earth magnetic alloy precursor powder is 120 μm, the rest is the same as in Example 1.

[0097] Comparative Example 1 This comparative example provides a method for preparing rare earth magnetic alloy powder by gaseous calcium reduction, including: (1) Therefore, according to the Sm excess of 30% and the atomic ratio of Sm:Fe of 1.3:5, Sm(OH)3 powder with a purity ≥99.9% and an average particle size of 160μm and Co(OH)2 powder with a purity ≥99.9% and an average particle size of 170μm are mixed in a V-type mixer for 3 hours to obtain a uniform rare earth magnetic alloy precursor powder; (2) After mixing the rare earth magnetic alloy precursor powder obtained in step (1) with metallic calcium, calcium chloride and potassium chloride in a mass ratio of 1:1:1:0.5, place it in a metal crucible and cover the crucible tightly.

[0098] (3) Place the metal crucible into the vacuum tube furnace, first introduce argon gas into the furnace cavity and then evacuate it. Repeat this operation 3 times to remove air; finally evacuate to 10. -3 Pa, then the tubular furnace was programmed to heat up to 600℃ for 4 hours. After the heat treatment was completed, the tubular furnace was immediately cooled to below 50℃ using an air-cooling device.

[0099] (4) Place the product in the crucible in ice water to dissolve a large amount of calcium and calcium oxide adhering to the surface of the magnetic powder. Then, slowly add acetic acid solution and stir the solution with a glass rod to make the reaction uniform. Test the pH of the solution while adding acetic acid solution, and stop adding when the entire solution is neutral. Then, ultrasonically wash twice with deionized water, centrifuge twice with anhydrous ethanol, and vacuum dry to obtain pure SmCo5 powder.

[0100] Performance testing: XRD tests were performed on the SmCo5 powders prepared in Example 1 and Comparative Example 1. The test results are shown in the figure. Figure 6 In Example 1, a pure phase SmCo5 was prepared, while in Comparative Example 1, the SmCo5 prepared contained the impurity phase Sm2Co7.

[0101] Under an external magnetic field of 7T, the rare earth magnetic alloy powders prepared in Examples 1, 4, 5, and 6 and Comparative Example 1 were subjected to PPMS testing to obtain the remanent magnetization M. r and coercivity H cj The test results are shown in Table 1. The MH curves of the rare earth magnetic alloy powders prepared in Example 1 and Comparative Example 1 are shown in Table 1. Figure 7 As shown.

[0102] Table 1 According to the test results in Table 1, Examples 1 to 3 used the method and apparatus provided by the present invention for preparing rare earth magnetic alloy powder by reducing gaseous calcium. By placing the rare earth magnetic alloy precursor powder and the calcium source in two separate spaces, and by heat treatment, the rare earth magnetic alloy precursor powder is reduced by gaseous calcium, which improves the utilization rate of calcium, makes the reaction more complete and thorough, and the magnetic alloy powder prepared has excellent magnetic properties.

[0103] Compared to the SmCo5 powder prepared by the conventional static process in Comparative Example 1, the SmCo5 powder provided in Example 1 exhibits significantly improved magnetic properties, M r Increased from 4.87kG to 5.46kG, H cj The concentration increased from 37.75 kOe to 44.06 kOe. Figure 7 As can be seen from the MH curves shown, Example 1 has better overall magnetic properties.

[0104] Based on the test results of Examples 1, 4, and 5, if the heat treatment temperature is too low, the degree of calcium source vaporization will be weak, the concentration of gaseous calcium inside the container will be low, which is not conducive to sufficient contact between gaseous calcium and rare earth magnetic alloy precursor powder, resulting in a decrease in the reduction efficiency of rare earth magnetic alloy precursor powder, incomplete reaction, and a decrease in the magnetic properties of SmCo5 powder. On the other hand, if the heat treatment temperature is too high, the gasification rate of the calcium source will be too fast, which will easily cause calcium residue on the surface of the prepared SmCo5 powder, resulting in a decrease in the magnetic properties of SmCo5 powder and a waste of calcium resources.

[0105] According to the test results of Examples 1 and 6, if the average particle size of the rare earth magnetic alloy precursor powder is small, it has a larger specific surface area. The volatilization loss of Sm element at high temperature is serious, which leads to the deviation of the stoichiometry of the final product. The rare earth magnetic alloy phase prepared is impure, which in turn leads to the decrease of magnetic properties of SmCo5 powder.

[0106] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing rare earth magnetic alloy powder by reduction of gaseous calcium, characterized in that, The method includes: Rare earth magnetic alloy precursor powder and calcium source are placed in the first and second regions of a vacuum container, respectively; heat treatment is performed to obtain the rare earth magnetic alloy powder. The first and second regions of the vacuum container are separated by a porous partition or a mesh partition, wherein the maximum pore size of the porous partition or mesh partition is smaller than the minimum particle size of the rare earth magnetic alloy precursor powder and the calcium source. The rare earth magnetic alloy precursor powder includes samarium precursor powder, cobalt precursor powder, and / or iron precursor powder.

2. The method as described in claim 1, characterized in that, The calcium source includes calcium metal; And / or, the material of the samarium precursor powder includes Sm2O3 and / or Sm(OH)3; And / or, the material of the cobalt precursor powder includes any one or a combination of at least two of Co, CoO, Co3O4 or Co(OH)2; And / or, the precursor powder of the iron is made of any one or a combination of at least two of Fe, Fe2O3, Fe3O4 or Fe(OH)3; And / or, the average particle size of the rare earth magnetic alloy precursor powder is above 150 μm; And / or, the mass ratio of the rare earth magnetic alloy precursor powder to the calcium source is 1:(0.2~1).

3. The method as described in claim 1 or 2, characterized in that, The vacuum level of the vacuum container is 10. -3 Pa or above; And / or, the temperature of the heat treatment is 600℃~850℃; And / or, the heat treatment time is 1h to 4h; And / or, the heat treatment process also includes stirring the rare earth magnetic alloy precursor powder; And / or, after the heat treatment is completed, the rare earth magnetic alloy powder is further cooled.

4. An apparatus used in the method for preparing rare earth magnetic alloy powder by reduction of gaseous calcium as described in any one of claims 1 to 3, characterized in that, The device includes: A cavity, wherein at least one heating system is provided on the inner wall of the cavity; An inner cylinder, which extends through the cavity and extends to the outside of the cavity at both ends; The container is fixed inside the inner cylinder by a fastener and corresponds to the heating system; the container is divided into a first region and a second region by a porous partition or a mesh partition, the first region and the second region are spatially independent, and gas flow is maintained between the first region and the second region; A trachea, one end of which is connected to a container and the other end is connected to a vacuum pump or a gas source.

5. The apparatus as described in claim 4, characterized in that, The device further includes at least two support parts, each support part including a rotary bearing, which is nested with both ends of an inner cylinder extending outside the cavity, thereby driving the inner cylinder to rotate. And / or, the device further includes an air-cooling system disposed adjacent to the heating system on the inner wall of the cavity.

6. The apparatus as described in claim 4 or 5, characterized in that, The inner wall of the first region of the container is provided with a number of turning plates. The length direction of the turning plates is consistent with the axial direction of the inner cylinder, and the angle between the height direction and the inner wall of the container is 30° to 45°.

7. The apparatus according to any one of claims 4 to 6, characterized in that, Along the axial direction of the inner cylinder, an end cap is provided on one side surface of the container, and a connection hole is provided on the opposite side surface of the end cap. The connection hole is connected to the gas pipe of the vacuum pump.

8. The apparatus as claimed in claim 7, characterized in that, In the container, a porous partition or a mesh partition is arranged along the axial direction of the inner cylinder.

9. The apparatus as claimed in claim 7, characterized in that, In the container, the second region is enclosed by a porous partition or a mesh partition to form a cage-like cavity, which is fixedly connected to the end cap.

10. The apparatus as claimed in claim 5, characterized in that, During the heat treatment process, the rotation speed of the inner cylinder is 15 r / min-30 r / min; And / or, during the cooling process, the rotation speed of the inner cylinder is 5 r / min to 10 r / min.

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