Magnet diffusion source foil, diffusion magnet and preparation method

Abstract

The invention discloses a magnet diffusion source foil, a diffusion magnet and a preparation method. The invention discloses a preparation method of a magnet diffusion source foil. The preparation method comprises the following steps: 1) providing a foam metal foil and rare earth slurry; 2) filling the rare earth slurry into pores of the foam metal foil to obtain a filler; 3) heating and compressing the filler to obtain a magnet diffusion source foil; or covering at least one surface of the filler with the metal foil, and then heating and compressing to obtain the magnet diffusion source foil. When the magnet diffusion source foil is used as a diffusion source of a sintered neodymium-iron-boron magnet, the coercive force of the magnet can be further improved, and the coercive force is greatly improved.

Description

Technical Field

[0001] The invention relates to a magnet diffusion source foil, a diffusion magnet and a preparation method. Background Art

[0002] Grain boundary diffusion (GBD) adds Dy and Tb heavy rare earth (HRE) elements to replace Nd in the main phase to form (HRE, Nd)2Fe with a higher magnetic anisotropy field. 14 B phase (HRE = Dy, Tb) increases the coercive force of the magnet. High coercive force can effectively resist the demagnetization field inherent in the magnet at high temperatures.

[0003] Appropriate rare earth alloy diffusion source during grain boundary diffusion can improve the depth of grain boundary diffusion layer and uniformity of element distribution of Nd-Fe-B magnets, which is the key to solving the problem of low coercivity.

[0004] CN118366773A discloses a method for preparing a diffusion source slurry for NdFeB magnets, comprising: preparing a diffusion source slurry according to the chemical formula RE1 a RE2 b RE3 c M1 d M2 e The composition ratio of each element is used for smelting and slicing to obtain a multi-component alloy quick-setting sheet; wherein RE1 is selected from terbium and / or dysprosium, RE2 is selected from praseodymium and / or neodymium, RE3 is selected from yttrium and / or gadolinium, M1 is selected from any one or more combinations of copper, aluminum, gallium, magnesium, iron, and cobalt, and M2 is selected from silicon and / or calcium; a, b, c, d, and e are the mass percentage contents of the corresponding elements, and satisfy 10≤a≤50, 0≤b≤20, 20≤c≤50, 0≤d≤30, 2≤e≤10, and a+b+c+d+e=100; the chemical formula of the multi-component alloy quick-setting sheet is RE1 a RE2 b RE3 c M1 d M2 e ; The multi-component alloy quick-setting sheet is subjected to jaw crushing and rolling ball milling to obtain a diffusion source coarse powder; The diffusion source coarse powder is subjected to air flow milling to obtain a diffusion source fine powder; and the diffusion source fine powder is mixed with an organic solvent and a binder to obtain a diffusion source slurry for NdFeB magnets. The diffusion source slurry has a good diffusion modification effect, but it is difficult to form a film for magnets with complex shapes. The use of a large amount of organic solvents and adhesives affects the performance of the magnet, pollutes the heat treatment equipment, causes product performance fluctuations, and the consistency needs to be improved. The increase in coercive force is still small.

[0005] CN118136395A discloses a slurry for sintered NdFeB screen printing, and its preparation method and application. The slurry contains the following components in weight percentage: 65-90% rare earth alloy RM powder, 8-30% deionized water, 0.25-5% binder, and 0.25-2% dispersant; in the rare earth alloy RM, R is selected from one or more of La, Ce, Pr, Nd, Dy, and Tb, and M is selected from one or more of Cu, Al, Ga, Mg, Fe, Co, and Ni.

[0006] CN110890210A discloses a method for improving the coercive force of arc-shaped NdFeB magnets, including mixing and stirring heavy rare earth powder with an organic adhesive and an organic solvent to form a heavy rare earth slurry, applying a layer of heavy rare earth slurry on a flexible film by screen printing and curing to form a heavy rare earth coating, then transferring the heavy rare earth coating to the surface to be diffused of the arc-shaped magnet and using pressure to keep the heavy rare earth coating and the surface to be diffused tightly, and then subjecting the arc-shaped NdFeB magnet with the heavy rare earth coating to high-temperature diffusion aging treatment. This patent partially solves the problem of film formation of diffusion sources of special-shaped magnets, but it does not eliminate or reduce the problem of the presence of a large amount of organic matter in the diffusion source film layer. The increase in coercive force is still relatively small.

[0007] CN118609942A discloses a magnet diffusion source film and its preparation method and application, wherein the diffusion source film comprises an upper substrate film, a diffusion source and a lower substrate film in sequence. The preparation method comprises the following steps: preparing a diffusion source sol; attaching the diffusion source sol to the lower substrate film; covering the upper substrate film to form an initial diffusion source film of a "sandwich" structure; heating, drying and cooling the initial diffusion source film to obtain a diffusion source film. The rare earth alloy diffusion source uses polyvinyl alcohol, polyurethane, polycarbonate and polyethylene terephthalate as the upper and lower layer carriers of the rare earth alloy diffusion source, which solves the problem of flexible diffusion source film formation. However, the organic adhesive in the diffusion source and the polymer film of the upper and lower layers of the "sandwich" structure are very unfavorable for the utilization of diffusion elements, and the use of a large amount of carbon-forming polymer substances further increases the content of impurity element carbon, affecting the improvement of magnet performance and quality stability. The increase in coercivity is still small. Summary of the invention

[0008] In view of this, one object of the present invention is to provide a method for preparing a magnet diffusion source foil, and the obtained magnet diffusion source foil can make the coercive force increase to a greater extent when used as a diffusion source for sintering NdFeB magnets. Furthermore, during grain boundary diffusion, no organic matter will be introduced to contaminate the magnet and the equipment. Another object of the present invention is to provide a magnet diffusion source foil prepared according to the preparation method as described above. Another object of the present invention is to provide a method for preparing a diffusion magnet. Another object of the present invention is to provide a diffusion magnet prepared according to the preparation method as described above. The present invention adopts the following technical scheme to achieve the above objects.

[0009] In one aspect, the present invention provides a method for preparing a magnet diffusion source foil, comprising the following steps:

[0010] 1) Providing foam metal foil and rare earth slurry;

[0011] 2) filling the pores of the foam metal foil with the rare earth slurry to obtain a filler;

[0012] 3) heating and compressing the filler to obtain a magnet diffusion source foil; or covering at least one surface of the filler with a metal foil, and then heating and compressing it to obtain a magnet diffusion source foil;

[0013] in,

[0014] The metal in the foam metal foil is a metal element or an alloy, and the porosity of the foam metal foil is above 80%; the rare earth element in the rare earth slurry is selected from at least one of light rare earth elements and heavy rare earth elements, and must contain heavy rare earth elements.

[0015] According to the preparation method of the present invention, preferably, the foam metal foil has a thickness of 0.1 to 3 mm, a pore size of 0.01 to 0.3 mm, and a through-porosity of greater than or equal to 95%.

[0016] According to the preparation method of the present invention, preferably:

[0017] The foamed metal foil is selected from a foamed metal foil of a single metal or a foamed metal foil covered with a different metal film; wherein the foamed metal foil of a single metal is selected from one of foamed copper foil, foamed cobalt foil, foamed nickel foil and foamed iron foil;

[0018] The metal foil is a metal foil or a metal alloy foil, and the metal element in the metal foil is selected from at least one of aluminum, copper, magnesium, zirconium and titanium.

[0019] According to the preparation method of the present invention, preferably:

[0020] The light rare earth element is selected from praseodymium and / or neodymium, and the heavy rare earth element is selected from dysprosium or terbium;

[0021] The rare earth slurry is a slurry formed by dispersing particles of rare earth metal single substance, rare earth metal alloy or rare earth compound in an organic solvent, and the particle size of the particles is less than 9.6 μm; the solute content in the rare earth slurry is 62.5-84.5 wt%.

[0022] According to the preparation method of the present invention, preferably, the rare earth slurry also includes a polymer compound, and the polymer compound is selected from at least one of thermosetting resins, thermoplastic resins, synthetic rubber, polyacrylic acid, polytetrafluoroethylene, polyimide and polyvinyl pyrrolidone; wherein the mass ratio of the polymer compound to the organic solvent is 1:8 to 25.

[0023] According to the preparation method of the present invention, preferably, in step 2), the rare earth slurry is reinforced and filled into the pores of the foam metal foil, and the reinforcement method is selected from ultrasound, vacuum or centrifugation.

[0024] According to the preparation method of the present invention, preferably, in step 3), heating and compression are carried out under vacuum or inert atmosphere; the heating temperature is 128-560°C; compression is carried out by rolling or rolling, and the number of compressions is more than one; the thickness of the obtained magnet diffusion source foil is 20-90% of the thickness of the foam metal foil.

[0025] On the other hand, the present invention also provides a magnet diffusion source foil, which is prepared according to the preparation method described above.

[0026] In another aspect, the present invention further provides a method for preparing a diffusion magnet, comprising the following steps:

[0027] One or more layers of the magnet diffusion source foil as described above are covered on the surface of the sintered NdFeB magnet, and vacuum heat treatment is performed to obtain a diffusion magnet.

[0028] In another aspect, the present invention further provides a diffused magnet, which is prepared according to the preparation method as described above.

[0029] The magnet diffusion source foil of the present invention can significantly improve the coercive force when used as a diffusion source for grain boundary diffusion of sintered NdFeB magnets, and the coercive force is improved to a large extent. In addition, the magnet diffusion source foil of the present invention is a separate diffusion source, which can avoid contamination of the magnet surface and equipment when removing the organic phase of the rare earth slurry. The present invention can also cut a suitable magnet diffusion source foil as a diffusion source to cover the surface of the magnet to be diffused according to the geometric size and performance requirements of the sintered NdFeB magnet to be diffused. The method of the present invention can simplify the rare earth slurry film-forming technology, reduce the difficulty and reduce the restrictions, and facilitate industrial production. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0031] The "remanent magnetism" mentioned in the present invention refers to the value of the magnetic flux density corresponding to the point where the magnetic field intensity is zero on the saturation hysteresis loop, usually denoted as Br, and the unit is Tesla (T) or Gauss (Gs). 1Gs = 0.0001T.

[0032] The "coercive force" mentioned in the present invention, also known as the intrinsic coercive force, refers to the magnetic field intensity when the magnetic field is monotonically reduced to zero and then increased in the opposite direction from the saturated magnetization state of the magnet, so that the magnetization intensity decreases to zero along the saturation hysteresis loop, usually denoted as H cj , the unit is Oersted (Oe) or Ampere / meter (A / m). 1Oe=79.6A / m. cj is the intrinsic coercivity at room temperature.

[0033] Compared with the prior art, the magnet diffusion source foil provided by the present invention can further improve the coercive force of the magnet when used as a diffusion source for grain boundary diffusion of a sintered NdFeB magnet, and the improvement is greater.

[0034] <Magnetic diffusion source foil and preparation method>

[0035] The present invention provides a method for preparing a magnet diffusion source foil, comprising the following steps:

[0036] (1) providing a foamed metal foil; (2) providing a rare earth slurry; (3) filling; (4) heating and compressing. Step (1) and step (2) are performed in no particular order. Optionally, the step of covering at least one surface of the filler with metal foil is also included. This is described in detail below. In the prior art, rare earth slurry is directly coated on the surface of the magnet to be diffused, which easily contaminates the magnet when the organic phase is removed, thereby affecting the performance of the magnet. The present invention uses foamed metal foil as a rare earth slurry carrier, removes the organic phase by heating, and can be rolled / pressed to obtain a dense magnet diffusion source foil.

[0037] Foam foil available

[0038] In the present invention, the foam metal foil is a thin sheet formed by foam metal. Foam metal refers to a special metal material containing foam pores. The foam metal foil can be commercially available. According to one embodiment of the present invention, the initial foam metal foil can be ultrasonically cleaned to obtain a clean foam metal foil with no surface contamination.

[0039] In the present invention, the metal in the foam metal foil is a metal element or a metal alloy, and the porosity of the foam metal foil is greater than 80%, for example, greater than 85%, or even greater than 95%. The thickness of the foam metal foil is 0.1 to 3 mm, preferably 0.15 to 3 mm, more preferably 0.2 to 1.8 mm, and even more preferably 0.2 to 1.1 mm. The pore size is 0.01 to 0.3 mm, preferably 0.05 to 0.25 mm, for example, 0.05 mm, 0.1 mm, or 0.15 mm. The through-porosity is greater than or equal to 95%, preferably greater than or equal to 96%, and even greater than 98%.

[0040] According to one embodiment of the present invention, the foam metal foil is selected from a foam metal foil of a single metal or a foam metal foil covered with a different metal film.

[0041] According to a specific embodiment of the present invention, the foam metal foil is a foam metal foil of a single metal substance, and the foam metal foil of a single metal substance is selected from one of foam copper foil, foam cobalt foil, foam nickel foil and foam iron foil.

[0042] According to another specific embodiment of the present invention, the foam metal foil is a foam metal foil covered with different metal films, that is, the metal in the foam metal foil is a metal alloy. The foam metal alloy foil can be obtained by depositing other metal single substances or alloy film layers on the surface of the foam metal, for example, electroplating copper on the surface of foam cobalt, physically vapor depositing aluminum film on the surface of foam iron, electroplating copper-cobalt alloy film on the surface of foam iron, etc.

[0043] Provide rare earth slurry

[0044] In the present invention, the rare earth element in the rare earth slurry is selected from at least one of light rare earth elements and heavy rare earth elements, and must contain heavy rare earth elements.

[0045] The light rare earth element is selected from at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm) and samarium (Sm), preferably selected from at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), more preferably selected from praseodymium (Pr) and / or neodymium (Nd). The heavy rare earth element is selected from at least one of gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er) and yttrium (Y), preferably selected from terbium or dysprosium.

[0046] According to one embodiment of the present invention, the rare earth slurry is a slurry formed by dispersing particles of a rare earth metal, a rare earth metal alloy or a rare earth compound in an organic solvent, and the particle size of the particles is less than 9.6 μm, preferably 2 to 8.5 μm, more preferably 2.2 to 7.6 μm, and more preferably 2.2 to 5.5 μm. The solute content in the rare earth slurry is 62.5 to 84.5 wt%, preferably 65 to 82 wt%, and more preferably 75 to 81 wt%. The solute here refers to particles of a rare earth metal, particles of a rare earth metal alloy or particles of a rare earth compound. The rare earth compound may be a rare earth hydride or a rare earth halide. For example, a rare earth halide may be a rare earth fluoride. The rare earth metal alloy may be an alloy formed by a rare earth element and other metals, for example, a praseodymium terbium copper aluminum alloy or a terbium copper alloy.

[0047] The organic solvent in the rare earth slurry is selected from one or more of p-methoxybenzyl alcohol, diethylene glycol butyl ether acetate, ethylene glycol diacetate, ethylene glycol ethyl ether acetate, tributyl citrate, α-terpineol, ethanol, acetone and petroleum ether.

[0048] According to one embodiment of the present invention, a polymer compound is further added to the rare earth slurry, and the mass ratio of the polymer compound to the organic solvent is 1:8 to 25, preferably 1:10 to 25, and more preferably 1:15 to 20. That is, the particles containing rare earth elements, the polymer compound and the organic solvent are evenly mixed to obtain a rare earth slurry. The polymer compound is used as a binder. The polymer compound is selected from at least one of a thermosetting resin, a thermoplastic resin, a synthetic rubber, polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), polyimide (PI), and polyvinyl pyrrolidone (PVP). Among them, thermosetting resins include but are not limited to epoxy resins, phenolic resins, urea-formaldehyde resins, and polyurethanes. Thermoplastic resins include but are not limited to polyvinyl acetal and perchlorethylene resin. Synthetic rubbers include but are not limited to styrene-butadiene rubber, chloroprene rubber, and nitrile rubber.

[0049] According to one specific embodiment of the present invention, the polymer compound is polyacrylic acid. According to another specific embodiment of the present invention, the polymer compound is phenolic resin.

[0050] Filling Steps

[0051] The rare earth slurry is filled into the pores of the foam metal foil to obtain a filler. In this way, the pores in the foam metal constrain the slurry rare earth material particles, making it easy to accurately control the rare earth material content, thereby avoiding the problem of performance deviation of the diffusion magnet.

[0052] In certain specific embodiments, the rare earth slurry is intensified and filled into the pores of the foamed metal foil, and the intensification method is selected from ultrasound, vacuum or centrifugation.

[0053] Heating and compression steps

[0054] In some embodiments, the filler is heated and compressed to obtain a magnet diffusion source foil. In other embodiments, at least one surface of the filler is covered with a metal foil, and then heated and compressed to obtain a magnet diffusion source foil.

[0055] In this way, the organic phase in the slurry can be removed by heating, and the content of harmful impurity elements in the diffusion source can be reduced; the filler can be densified by compression, and the rare earth particles in the densified diffusion source foil are in close contact. During the vacuum heat treatment process, the contact area with the base magnet to be diffused can be increased, which is beneficial to the migration of diffused atoms. The coercive force of the magnet can be further improved, and the coercive force can be improved by a large margin. In addition, the densified magnet diffusion source foil, as a grain boundary diffusion source, creates conditions for the extreme utilization of low-temperature grain boundary diffusion and high-value elements such as heavy rare earths while ensuring the performance of the magnet, and solves the problems of low utilization rate of heavy rare earths, long diffusion time and high temperature in grain boundary diffusion.

[0056] Covering at least one surface of the filler with metal foil is conducive to obtaining a diffusion source alloy component that is substantially completely dense and adjustable in combination. According to one embodiment of the present invention, at least one surface of the filler is covered with metal foil, the metal foil is a metal foil or a metal alloy foil, and the metal element in the metal foil is selected from at least one of aluminum, copper, magnesium, zirconium and titanium. In certain specific embodiments, the metal foil is selected from pure aluminum foil, aluminum alloy foil, pure copper foil, copper alloy foil, pure magnesium foil or magnesium alloy foil.

[0057] In the present invention, the densified magnet diffusion source foil has the capability of cutting, winding and splicing, etc. In the present invention, heating and compression are both performed under vacuum or inert atmosphere.

[0058] According to one embodiment of the present invention, the heating temperature may be 128 to 560° C., preferably 128 to 420° C., and more preferably 130 to 400° C. The heating may be first performed at 128 to 280° C., while applying pressure to the upper and lower surfaces of the filler for compression, and the heating temperature may be gradually increased to 280 to 560° C., preferably to 350 to 560° C. during the compression process.

[0059] According to a specific embodiment of the present invention, the heating can be performed under vacuum using an infrared heating apparatus.

[0060] In certain embodiments, the compression is performed by rolling or pressing, and the number of compressions is one or more, and may be two or more.

[0061] The thickness of the magnet diffusion source foil obtained by the present invention can be 20-90% of the thickness of the foam metal foil, preferably 30-89%, and more preferably 50-88%.

[0062] <Diffused magnet and preparation method>

[0063] One or more layers of the magnet diffusion source foil as described above are covered on the surface of the sintered NdFeB magnet, and vacuum heat treatment is performed to obtain a diffusion magnet.

[0064] The sintered NdFeB magnet of the present invention is R2Fe 14 A rare earth sintered permanent magnet with B-type compound as the main phase. R is selected from at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm) and europium (Eu), and must contain Nd. The sintered NdFeB magnet of the present invention may contain or not contain heavy rare earth elements. Among them, the heavy rare earth elements here are selected from gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y).

[0065] According to one embodiment of the present invention, R is selected from at least one element of Pr and Nd, and must contain Nd. According to a preferred embodiment of the present invention, R is Nd and Pr. In the present invention, B is boron.

[0066] In the present invention, the sintered NdFeB magnet may contain M, wherein M is selected from one or more of Cu, Co, Al, Ti, Ga and Zr.

[0067] According to a specific embodiment of the present invention, the grade of the sintered NdFeB magnet may be N grade or M grade.

[0068] In the present invention, the vacuum degree during vacuum heat treatment is less than or equal to 1.0×10 -1 Pa is preferably less than or equal to 1.0×10 -2 Pa, more preferably less than or equal to 1.0×10 -3 Pa. Vacuum heat treatment includes primary vacuum heat treatment, secondary vacuum heat treatment and aging treatment.

[0069] During the primary vacuum heat treatment, the temperature is raised from room temperature to the holding temperature of the primary vacuum heat treatment, and the heating rate can be 4 to 12°C / min, preferably 5 to 11°C / min, and more preferably 5 to 10°C / min. The holding temperature of the primary vacuum heat treatment can be 520 to 845°C, preferably 580 to 800°C, and more preferably 600 to 780°C, for example, 650°C, 685°C, 700°C, 750°C, and 780°C. The holding time of the primary vacuum heat treatment can be 30 to 300 min, preferably 60 to 260 min, more preferably 90 to 200 min, and further preferably 90 to 150 min.

[0070] The holding temperature of the secondary vacuum heat treatment may be 850 to 950° C., preferably 860 to 920° C., more preferably 880 to 920° C. For example, it may be 900° C. or 910° C. The holding time of the secondary vacuum heat treatment may be 180 to 480 min., preferably 220 to 420 min., more preferably 300 to 380 min.

[0071] After the secondary vacuum heat treatment, cool to room temperature.

[0072] During the aging treatment, the temperature is increased from room temperature to the holding temperature of the aging treatment, and the heating rate can be 4-12°C / min, preferably 5-11°C / min, and more preferably 5-10°C / min. The holding temperature of the aging treatment can be 400-658°C, preferably 450-640°C, and more preferably 480-530°C. For example, it can be 490°C, 505°C, and 520°C. The holding time of the aging treatment can be 60-300min, preferably 90-260min, and more preferably 90-200min. After the aging treatment is completed, it is quickly cooled to room temperature. This is conducive to improving the coercive force of the obtained diffused magnet, and the residual magnetism is less reduced.

[0073] The coercive force of the diffused magnet obtained by the present invention is further improved, and the improvement is relatively large, the improvement is greater than or equal to 10 kOe, preferably greater than or equal to 10.3 kOe, and the remanence is not significantly reduced.

[0074] According to a specific embodiment of the present invention, two layers of magnet diffusion source foils as described above are stacked together, and then the stacked foils are covered on the upper and lower surfaces of the sintered NdFeB magnets, and then the sintered NdFeB magnets coated with the magnet diffusion source foils are placed in a vacuum furnace for vacuum heat treatment. When the vacuum degree of the vacuum furnace is less than 10 -3Pa, control the heating rate from room temperature to 520-845℃ at 4-12℃ / min, keep at 520-845℃ for 30-300min, and then heat from 520-845℃ to 850-950℃, keep at 850-950℃ for 180-480min, and cool to room temperature after the end of the insulation. Then carry out aging treatment. When the vacuum degree of the vacuum furnace reaches 10 -3 Pa, control the heating rate from room temperature (~25℃) to 400~658℃ to be 4~12℃ / min, keep warm at 400~658℃ for 60~300min, and quickly cool to room temperature after the end of the heat preservation to obtain the diffusion magnet.

[0075] <Test Method>

[0076] Determination of magnetic properties: Use a BH magnetometer to measure the magnetic properties of sintered NdFeB permanent magnets and diffused magnets at room temperature to obtain their room temperature remanence Br and room temperature coercivity Hcj.

[0077] Example 1

[0078] The initial foam copper foil is ultrasonically treated in anhydrous ethanol to obtain a foam copper foil with a clean surface and no pollution. The foam copper foil has a thickness of 200 μm, a pore size of 0.05 mm, a porosity of 85%, and a through-pore rate of 95%.

[0079] Terbium hydride particles, polyacrylic acid (PAA), and an organic solvent are mixed and stirred to obtain a rare earth slurry. 50 The particle size of the terbium hydride particles in the rare earth slurry is 70.6 wt %. The organic solvent is a mixed solvent of p-methoxybenzyl alcohol and anhydrous ethanol in a volume ratio of 70:30; the mass ratio of PAA to the organic solvent is 1:18.

[0080] The rare earth slurry was evenly coated on the upper and lower surfaces of a 200 μm thick foam copper foil, and the total thickness of the foil was 284 μm to obtain a filler. The filler was dried and solidified at 130°C using an infrared heating instrument under vacuum, and a roller press was used to apply pressure to the upper and lower surfaces of the filler. The roller press was repeated multiple times while gradually increasing the heating temperature to 420°C to remove the organic phase in the filler, and a magnet diffusion source foil with a flat surface and close contact of rare earth particles inside was obtained, and the thickness was 148 μm.

[0081] Stack two layers of magnet diffusion source foil together and cover the upper and lower surfaces of the sintered NdFeB magnet with the grade of N52 respectively. The magnet surface covered with the magnet diffusion source foil is perpendicular to the C-axis orientation direction (that is, the magnet diffusion source foil is covered on the two surfaces perpendicular to the thickness direction). The specifications of the sintered NdFeB magnet are 35mm in length and width and 3mm in thickness. Then place the magnet coated with the magnet diffusion source foil in a vacuum furnace for heat treatment. When the vacuum degree of the vacuum furnace is less than 10 -3 Pa, and control the heating rate from room temperature to 665℃ to be 10℃ / min. Keep at 665℃ for 90min, and then heat from 665℃ to 910℃, and keep at 910℃ for 350min. Then cool to room temperature. Then carry out aging treatment. When the vacuum degree of the vacuum furnace reaches 10 -3 Pa, and control the heating rate from room temperature (~25℃) to 505℃ to be 10℃ / min. Keep it at 505℃ for 180min, and quickly cool it to room temperature after the end of the insulation to obtain the diffusion magnet.

[0082] Table 1

[0083] project <![CDATA[B r / kGs]]> <![CDATA[H cj / kOe]]> Initial sintered NdFeB magnets 14.32 12.64 Diffusion magnet of Example 1 14.24 23.45

[0084] As shown in Table 1, the coercivity of the diffused magnet obtained by diffusing the magnet diffusion source foil of the present invention on the surface of the sintered NdFeB magnet is significantly improved, and the coercivity improvement range △H cj The magnet grade is improved from the original N52 grade to 50SH grade.

[0085] Example 2

[0086] The initial foamed cobalt foil was ultrasonically treated in anhydrous ethanol to obtain a foamed cobalt foil with a clean surface and no pollution. The foamed cobalt foil had a thickness of 200 μm, a pore size of 0.15 mm, a porosity of 92%, and a through-pore rate of 98%.

[0087] The terbium copper alloy particles, polyvinyl pyrrolidone (PVP), and organic solvent were mixed and stirred to obtain a rare earth slurry. The mass ratio of terbium to copper in the terbium copper alloy particles was 78:22. The D 50 The particle size of the terbium copper alloy particles in the rare earth slurry is 75.8 wt %. The organic solvent is a mixed solvent formed by diethylene glycol butyl ether acetate and anhydrous ethanol in a volume ratio of 1:1, and the mass ratio of PVP to the organic solvent is 1:20.

[0088] The rare earth slurry was evenly coated on the upper and lower surfaces of the foamed cobalt foil with a thickness of 200 μm, and the total thickness of the foil was 285 μm, thus obtaining a filler. A pure aluminum foil with a thickness of 10 μm was covered on one side of the filler, and then the filler was dried and solidified at 130°C using an infrared heating instrument under vacuum, and a roller press was used to apply pressure to the upper and lower surfaces of the filler. The heating temperature was gradually increased to 450°C during multiple roller pressing to remove the organic phase in the filler, and a magnet diffusion source foil with a smooth surface and close contact of the rare earth particles inside was obtained, with a thickness of 176 μm.

[0089] Stack two layers of magnet diffusion source foil together and cover the upper and lower surfaces of the sintered NdFeB magnet with the brand of 52M respectively. The magnet surface covered with the magnet diffusion source foil is perpendicular to the C-axis orientation direction (that is, the magnet diffusion source foil is covered on two surfaces perpendicular to the thickness direction). The specifications of the sintered NdFeB magnet are 40mm in length and width and 8mm in thickness. Then place the magnet covered with the magnet diffusion source foil in a vacuum furnace for heat treatment. When the vacuum degree of the vacuum furnace is less than 10 -3 Pa, and control the heating rate from room temperature to 700℃ to be 10℃ / min. Keep at 700℃ for 125min. After the insulation, heat from 700℃ to 900℃, keep at 900℃ for 360min, and cool to room temperature after the insulation. Then carry out aging treatment. When the vacuum degree of the vacuum furnace reaches 10 -3 Pa, and control the heating rate from room temperature (~25℃) to 520℃ to be 5℃ / min. Keep it at 520℃ for 90min, and quickly cool it to room temperature after the end of the insulation to obtain the diffusion magnet.

[0090] Table 2

[0091] project <![CDATA[B r / kGs]]> <![CDATA[H cj / kOe]]> Initial sintered NdFeB magnets 14.52 15.52 Diffusion magnet of Example 2 14.43 25.87

[0092] As shown in Table 2, the coercivity of the diffused magnet obtained by diffusing the magnet diffusion source foil of the present invention on the surface of the sintered NdFeB magnet is significantly improved, ΔH cj The magnet grade is upgraded from the original 52M grade to 50UH grade.

[0093] Example 3

[0094] The initial foam metal foil is a foam nickel foil, and a copper metal film is electroplated on the surface of the foam nickel foil, and the thickness of the electroplated copper film is 10 μm. The initial foam metal foil is ultrasonically treated in anhydrous ethanol to obtain a foam metal foil with a clean and pollution-free surface. The total thickness of the foam metal foil is 280 μm, the pore size is 0.1 mm, the porosity is 98%, and the through-pore rate is 98%.

[0095] The praseodymium terbium copper aluminum alloy particles, phenolic resin, and organic solvent are mixed and stirred to obtain a rare earth slurry. The mass ratio of praseodymium, terbium, copper, and aluminum in the praseodymium terbium copper aluminum alloy particles is 58.57:12.56:24.46:4.41. The D 50 The particle size of the rare earth slurry is 2.84 μm. The content of the praseodymium terbium copper aluminum alloy particles is 78.4 wt %. The organic solvent is a mixed solvent formed by diethylene glycol butyl ether acetate and acetone in a volume ratio of 1:1; the mass ratio of the phenolic resin to the organic solvent is 1:20.

[0096] The rare earth slurry was evenly coated on the upper and lower surfaces of a foam metal foil with a thickness of 280 μm, and the total thickness of the foil was 430 μm, thereby obtaining a filler. The filler was dried and solidified at 130°C using an infrared heating instrument under vacuum, and a roller press was used to apply pressure to the upper and lower surfaces of the filler. The roller press was repeated multiple times while gradually increasing the heating temperature to 380°C to remove the organic phase in the filler, thereby obtaining a magnet diffusion source foil with a flat surface and close contact between the rare earth particles inside, and a thickness of 150.5 μm.

[0097] Stack two layers of magnet diffusion source foil together and cover the upper and lower surfaces of the sintered NdFeB magnet with the grade of N52 respectively. The magnet surface covered with the magnet diffusion source foil is perpendicular to the C-axis orientation direction (that is, the magnet diffusion source foil is covered on the two surfaces perpendicular to the thickness direction). The specifications of the sintered NdFeB magnet are 20mm in length and width and 6mm in thickness. Then place the magnet coated with the magnet diffusion source foil in a vacuum furnace for heat treatment. When the vacuum degree of the vacuum furnace is less than 10 -3 Pa, the heating rate from room temperature to 700℃ was controlled at 10℃ / min, and the temperature was kept at 700℃ for 90min. After the temperature was kept at 700℃, the temperature was raised from 700℃ to 900℃, and the temperature was kept at 900℃ for 420min. After the temperature was kept at 900℃, the temperature was cooled to room temperature. Then the aging treatment was carried out. When the vacuum degree of the vacuum furnace reached 10 -3 Pa, and control the heating rate from room temperature (~25℃) to 490℃ to be 10℃ / min. Keep it at 490℃ for 90min, and quickly cool it to room temperature after the end of the insulation to obtain the diffusion magnet.

[0098] Table 3

[0099] project <![CDATA[B r / kGs]]> <![CDATA[H cj / kOe]]> Initial sintered NdFeB magnets 14.35 12.49 Diffusion magnet of Example 3 14.12 23.89

[0100] As shown in Table 3, the coercivity of the diffused magnet obtained by diffusing the magnet diffusion source foil of the present invention on the surface of the sintered NdFeB magnet is significantly improved, ΔH cj The magnet grade is improved from the original N52 to 50SH.

[0101] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for preparing a magnet diffusion source foil, characterized in that: The following steps are involved: 1) Providing foam metal foil and rare earth slurry; 2) filling the pores of the foam metal foil with the rare earth slurry to obtain a filler; 3) heating and compressing the filler to obtain a magnet diffusion source foil; or covering at least one surface of the filler with a metal foil, and then heating and compressing it to obtain a magnet diffusion source foil; in, The metal in the foam metal foil is a metal element or an alloy, and the porosity of the foam metal foil is above 80%; the rare earth element in the rare earth slurry is selected from at least one of light rare earth elements and heavy rare earth elements, and must contain heavy rare earth elements.

2. The preparation method according to claim 1, characterized in that: The foam metal foil has a thickness of 0.1 to 3 mm, a pore size of 0.01 to 0.3 mm, and a through-porosity of greater than or equal to 95%.

3. The preparation method according to claim 1, characterized in that: The foamed metal foil is selected from a foamed metal foil of a single metal or a foamed metal foil covered with a different metal film; wherein the foamed metal foil of a single metal is selected from one of foamed copper foil, foamed cobalt foil, foamed nickel foil and foamed iron foil; The metal foil is a metal foil or a metal alloy foil, and the metal element in the metal foil is selected from at least one of aluminum, copper, magnesium, zirconium and titanium.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The light rare earth element is selected from praseodymium and / or neodymium, and the heavy rare earth element is selected from dysprosium or terbium; The rare earth slurry is a slurry formed by dispersing particles of rare earth metal single substance, rare earth metal alloy or rare earth compound in an organic solvent, and the particle size of the particles is less than 9.6 μm; the solute content in the rare earth slurry is 62.5-84.5 wt%.

5. The preparation method according to claim 4, characterized in that: The rare earth slurry also includes a polymer compound, which is selected from at least one of thermosetting resins, thermoplastic resins, synthetic rubber, polyacrylic acid, polytetrafluoroethylene, polyimide and polyvinyl pyrrolidone; wherein the mass ratio of the polymer compound to the organic solvent is 1:8 to 25.

6. The preparation method according to claim 5, characterized in that: In step 2), the rare earth slurry is reinforced and filled into the pores of the foam metal foil, and the reinforcement method is selected from ultrasound, vacuum or centrifugation.

7. The preparation method according to claim 5, characterized in that: In step 3), heating and compression are carried out under vacuum or inert atmosphere; the heating temperature is 128-560° C.; compression is carried out by rolling or rolling, and the number of compressions is more than one; the thickness of the obtained magnet diffusion source foil is 20-90% of the thickness of the foam metal foil.

8. A magnet diffusion source foil, characterized in that: It is prepared according to the preparation method according to any one of claims 5 to 7.

9. A method for preparing a diffusion magnet, characterized in that: The following steps are involved: One or more layers of the magnet diffusion source foil according to claim 8 are covered on the surface of the sintered NdFeB magnet, and vacuum heat treatment is performed to obtain a diffusion magnet.

10. A diffusion magnet, characterized in that: It is prepared according to the preparation method according to claim 9.