Permanent magnet material, and preparation method therefor and use thereof

Abstract

Disclosed in the present disclosure are a permanent magnet material having a polyhedral structure, and a preparation method therefor and a use thereof. In the R-T-B system of the permanent magnet material, R comprises a light rare earth element and a heavy rare earth element; the light rare earth element (RL) at least comprises one or two selected from neodymium (Nd) and praseodymium (Pr); the heavy rare earth element (RH) at least comprises one or two selected from dysprosium (Dy) and terbium (Tb); T at least comprises iron (Fe); and B is boron. The permanent magnet material has a polyhedral structure, and the polyhedral structure comprises at least three outer surfaces, wherein the heavy rare earth content of the outer surfaces of the polyhedral structure is different. In the present disclosure, by controlling the coercivity gradient in specific directions, the coercivity distribution can meet the actual requirements of a motor for a magnet, and the content of heavy rare earth in the magnet can be effectively reduced, reducing the product costs; in addition, the process method is conducive to batch production.

Description

Permanent magnetic material and its preparation method and application

[0001] This application claims priority to the following prior applications: Patent Application No. 202311857881.4, filed with the State Intellectual Property Office of China on December 29, 2023, entitled “Permanent Magnetic Material with Polyhedral Structure, Preparation Method and Application thereof,” and Patent Application No. 202311857879.7, filed with the State Intellectual Property Office of China on December 29, 2023, entitled “A Permanent Magnetic Material, Preparation Method and Application thereof.” The entire texts of the above two prior patent applications are incorporated herein by reference. Technical Field

[0002] The present invention belongs to the field of permanent magnetic materials and relates to permanent magnetic materials, preparation methods and applications thereof. Background Art

[0003] Sintered NdFeB, a third-generation rare earth permanent magnet material, is widely used due to its excellent magnetic properties. In particular, with the rapid development of new energy vehicles, wind power generation, smart consumer electronics, energy-saving motors and other fields in recent years, sintered NdFeB materials have been more widely used.

[0004] The basic performance of rare earth permanent magnet materials can be evaluated by the following four performance parameters: remanence (i.e. residual magnetic induction intensity) Br, magnetic coercivity Hcb, intrinsic coercivity Hcj, and maximum magnetic energy product (BH) max. At present, when applied to fields such as automotive motors, the local demagnetization problem of NdFeB permanent magnet materials is a key factor affecting the stability of the motor. In order to improve such problems, the industry has proposed grain boundary diffusion technology, which arranges heavy rare earth on the surface of the magnet and allows it to enter the interior of the magnet along the grain boundary to improve the magnet performance and reduce the reduction of remanence. However, the methods of the prior art mainly achieve the grain boundary diffusion effect by completely coating multiple surfaces of the permanent magnet material or coating in local corner areas, but these methods have problems such as high heavy rare earth dosage, difficulty in controlling local coercivity, unstable performance, etc., and the existing methods are difficult to achieve large-scale production.

[0005] Therefore, there is an urgent need to develop permanent magnetic materials with improved performance and their preparation methods to meet the needs of their downstream application fields. Summary of the Invention

[0006] In order to improve the above-mentioned problems, the present disclosure provides, in a first aspect, an RTB-based permanent magnet material having a polyhedral structure, characterized in that:

[0007] R includes light rare earth elements and heavy rare earth elements;

[0008] The light rare earth element (RL) includes at least one or two selected from neodymium (Nd) and praseodymium (Pr);

[0009] The heavy rare earth element (RH) includes at least one or two selected from dysprosium (Dy) and terbium (Tb);

[0010] T contains at least iron (Fe);

[0011] B is boron;

[0012] The permanent magnetic material has a polyhedral structure, and the polyhedral structure includes at least three outer surfaces, wherein the heavy rare earth contents of the outer surfaces of the polyhedral structure are different.

[0013] According to an embodiment of the present disclosure, the permanent magnetic material is an anisotropic magnet having a polyhedral structure. Preferably, the polyhedral structure includes 3, 4, 5, 6, 7, 8 or more outer surfaces. For example, the polyhedral structure consists of 3, 4, 5, 6, 7 or 8 outer surfaces. It is understood by those skilled in the art that the polyhedral structure can also be named according to the number of its outer surfaces. For example, the above-mentioned polyhedral structure can also be called a trihedron, a tetrahedron, a pentahedron, a hexahedron, a heptahedron or an octahedron.

[0014] According to the embodiment of the present disclosure, the motor output peak torque loss rate of the permanent magnet material after running the endurance test at 150°C is less than 5%, preferably less than 4.5%, and more preferably less than 2.5%.

[0015] According to the embodiment of the present disclosure, among the outer surfaces of the polyhedral structure, there is at least one outer surface S H , the outer surface S H The weight percentage content of heavy rare earth elements in the polyhedron core is higher than the weight percentage content of heavy rare earth elements in the polyhedron core. H The other outer surfaces are called S L .

[0016] According to the embodiment of the present disclosure, preferably, when the number of outer surfaces of the polyhedron is n, the outer surface S H The number n H =1≤n H ≤n.

[0017] According to an embodiment of the present disclosure, the outer surface S H The number of the outer surface S is greater than L , or the outer surface S H The number of the outer surface S L , or the outer surface S H The number of is less than the outer surface S L .

[0018] For ease of description, when there are multiple outer surfaces S H When different outer surface S H Can be numbered such as S H1 、S H2 、S H3 etc.

[0019] Preferably, the weight percentage of the heavy rare earth element (measured by X-ray fluorescence spectrometer) on each outer surface is less than 10 wt %, for example, 0-7 wt %.

[0020] According to the embodiments of the present disclosure, the heavy rare earth element (RH) has a meaning well known in the art, and includes at least one or two selected from dysprosium (Dy) and terbium (Tb), and may also be selected from one or more of gadolinium (Gd), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y).

[0021] According to the embodiments of the present disclosure, the light rare earth element has a meaning well known in the art, and includes at least one or two selected from neodymium (Nd) and praseodymium (Pr); it can also be selected from one or more of lanthanum (La), cerium (Ce), promethium (Pm), samarium (Sm), and europium (Eu).

[0022] According to the embodiment of the present disclosure, preferably, the outer surface S L Parallel to the magnet orientation direction of the permanent magnetic material, and / or the outer surface S L The direction of the permanent magnetic material is not parallel to the central axis of the motor.

[0023] According to an embodiment of the present disclosure, the permanent magnetic material may further contain or not contain M, wherein M is selected from one or more transition metal elements and non-metallic elements.

[0024] According to an embodiment of the present disclosure, T is selected from iron (Fe) or a mixture of iron and other metal elements. Preferably, the other metals may be selected from one or more transition metal elements other than iron.

[0025] Transition metal elements, as used herein, have a meaning generally known in the art and refer to metal elements in the d-block and ds-block of the periodic table. D-block elements include elements from Groups IIIB to VIIB, and Groups VIII, but exclude lanthanides and actinides; and ds-block elements include elements from Groups IB to IIB. Generally speaking, transition metal elements include elements from ten groups, from Groups 3 to 12, but exclude inner transition elements from the f-block (elements 58 to 71 in the periodic table are called 4f inner transition elements, and elements 90 to 103 are called 5f inner transition elements, all of which belong to the f-block).

[0026] According to an embodiment of the present disclosure, the other metals may be selected from one or more of copper (Cu), gallium (Ga), aluminum (Al), zirconium (Zr), titanium (Ti), Nb (niobium), tin (Sn), tantalum (Ta) and manganese (Mn).

[0027] According to an embodiment of the present disclosure, M is preferably selected from one or more of Cu, Ga, Al, Zr, Ti, Nb, Sn, Ta and Mn, such as one or more of Zr, Cu, Ga and Al.

[0028] According to an embodiment of the present disclosure, based on the mass of the permanent magnetic material, the mass percentage content of R is greater than or equal to 28.5% and less than or equal to 32.5%, examples of which may be 28.5%, 29.0%, 29.5%, 30.0%, 30.5%, 31.0%, 31.5%, 32.0% or 32.5%.

[0029] According to an embodiment of the present disclosure, based on the mass of the permanent magnet material, the mass percentage content of B is 0.88% or more and 1.05% or less, and examples thereof may be 0.88%, 0.90%, 0.92%, 0.95%, 0.98%, 1.00%, 1.02% or 1.05%.

[0030] According to an embodiment of the present disclosure, based on the mass of the permanent magnetic material, the total mass percentage content of M is greater than 0.1% and less than 4.0%, preferably greater than 0.3% and less than 3.5%, examples of which may be 0.3%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% or 3.5%.

[0031] According to an embodiment of the present disclosure, the permanent magnetic material contains Ga. Preferably, based on the mass of the permanent magnetic material, the mass percentage content of Ga is 0.1% or more and 0.6% or less, and examples thereof may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or 0.6%.

[0032] According to an embodiment of the present disclosure, the permanent magnetic material contains Co. Preferably, based on the mass of the permanent magnetic material, the mass percentage content of Co is 0% or more and 3.0% or less, preferably greater than 0% and 3.0% or less, and examples thereof may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3.0%.

[0033] According to an embodiment of the present disclosure, the permanent magnetic material includes Cu. Preferably, based on the mass of the permanent magnetic material, the Cu content is greater than 0% and less than 0.8%, preferably greater than 0% and less than 0.4%, and examples thereof may include 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%.

[0034] According to an embodiment of the present disclosure, the balance of the permanent magnetic material is Fe and inevitable impurities, and the inevitable impurities are, for example, at least one of C, S, N, O, etc.

[0035] According to an embodiment of the present disclosure, when present, the C content is 400 to 800 ppm by mass based on the mass of the permanent magnetic material.

[0036] According to an embodiment of the present disclosure, when present, the O content is 300 to 900 ppm by mass based on the mass of the permanent magnetic material.

[0037] According to an embodiment of the present disclosure, when present, the N content is 400 to 800 ppm by mass based on the mass of the permanent magnetic material.

[0038] According to an embodiment of the present disclosure, when present, the S content is 0 to 100 ppm by mass based on the mass of the permanent magnetic material.

[0039] According to an embodiment of the present disclosure, the coercive force of the permanent magnetic material tends to decrease from the surface toward the core of the permanent magnetic material;

[0040] For S parallel to the magnet orientation direction H The absolute value of the coercivity difference at the distance D1 is ΔHcjm. For example, within the distance D1, ΔHcjm = |ΔHcj| / D1;

[0041] For other S H Face and / or S L The absolute value of the coercivity difference at distance D2 is ΔHcjn; for example, within the range of distance D2, ΔHcjn = |ΔHcj| / D2;

[0042] When D1=D2, and the starting points of D1 and D2 are equidistant from the magnet surface, ΔHcjm>ΔHcjn.

[0043] According to the embodiment of the present disclosure, the distance D1 or D2 represents the distance between any two points between the surface of the permanent magnetic material and its core. Preferably, for S parallel to the orientation direction of the magnet and parallel to the central axis of the motor, H The absolute value of the coercivity difference per unit distance is ΔHcjm.

[0044] According to an embodiment of the present disclosure, when the polyhedron is a non-hexahedral structure, the magnet S H The angle between the plane and the orientation direction of the magnet is α, and α≤45°.

[0045] According to an embodiment of the present disclosure, ΔHcjn≤0.3 kOe / mm, and ΔHcjm≥0.3 kOe / mm.

[0046] According to an embodiment of the present disclosure, the permanent magnetic material is a sintered permanent magnet.

[0047] The present disclosure also provides a method for preparing the permanent magnetic material, wherein the method comprises the following steps:

[0048] (a) applying the mixture A and / or the mixture B on a plane perpendicular to the orientation direction of the magnet substrate, and applying the mixture A and / or the mixture B on a plane parallel to the orientation direction of the magnet substrate;

[0049] (b) subjecting the NdFeB magnet material obtained in step (a) to grain boundary diffusion treatment and aging treatment to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0050] According to the embodiment of the present disclosure, in step (a), the number of coated surfaces is 1, 2, 3 or 4, and the coated surface includes at least one plane parallel to the central axis of the motor, wherein the area of ​​the coated region accounts for ≤100% of the area of ​​the magnet plane.

[0051] According to an embodiment of the present disclosure, the mixture A and / or the mixture B may both include: powder of RH and / or powder of RL, wherein RH and RL have the meanings as described above.

[0052] Preferably, the RH powder is at least one selected from the group consisting of a single metal of RH, an alloy of RH, an oxide of RH, a fluoride, a hydride, and an oxyfluoride.

[0053] Preferably, the RL powder is at least one selected from the group consisting of a single metal of RL, an alloy of RL, an oxide of RL, a fluoride, a hydride, and an oxyfluoride.

[0054] Preferably, the mixture A and / or mixture B may further include an organic solvent.

[0055] Preferably, the mixture A and / or the mixture B may further include an antioxidant and / or a dispersant to reduce the agglomeration of the rare earth in the slurry, thereby making the rare earth in the slurry more evenly distributed.

[0056] The antioxidant is, for example, at least one selected from toluene, 4-hexylresorcinol, and dibutylhydroxytoluene.

[0057] The present disclosure has no particular limitation on the dispersant. Any dispersant for such reactions familiar to those skilled in the art can be used. Those skilled in the art can select and adjust the dispersant based on actual production conditions, product requirements, quality control and other factors. The dispersant in the present disclosure preferably includes at least one of polyethylene glycol-400 and terpineol.

[0058] The organic solvent is preferably an alcohol, ketone, or ether that can dissolve the antioxidant, is easily volatile, and has low viscosity, and may be ethanol, acetone, or butanone.

[0059] According to an embodiment of the present disclosure, when the mixture A and / or mixture B contains Dy, the percentage of Dy element in the weight of the magnet matrix is ​​0.3-1.2%; when the mixture A and / or mixture B contains Tb, the percentage of Tb element in the weight of the magnet matrix is ​​0.1-0.7%.

[0060] According to an embodiment of the present disclosure, when the mixture A and / or the mixture B contains Pr and / or Nd, the percentage of Pr and / or Nd in the magnet matrix is ​​0.3-1.2% by weight.

[0061] According to an embodiment of the present disclosure, the method further includes preparing a magnet matrix, and the preparation of the magnet matrix is ​​a conventional method in the art.

[0062] According to an embodiment of the present disclosure, the grain boundary diffusion treatment may be a method known to those skilled in the art. For example, the method may include a thermal diffusion treatment and a tempering treatment.

[0063] According to an embodiment of the present disclosure, the thermal diffusion treatment is a grain boundary diffusion treatment, and its treatment method is a process known in the art. The temperature of the thermal diffusion treatment may be above 800°C, for example, 850-950°C, and examples thereof may be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, or 900°C. The thermal diffusion treatment time may be above 5 hours, such as 10-50 hours, for example, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, or 50 hours.

[0064] According to an embodiment of the present disclosure, the tempering temperature may be 700° C. or lower, for example, 450 to 650° C., and examples thereof may be 450° C., 460° C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540° C., 550° C., 560° C., 570° C., 580° C., 590° C., 600° C., 610° C., 620° C., 630° C., 640° C., or 650° C. The tempering time may be 1 hour or longer, for example, 1 to 10 hours, and examples thereof may be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0065] According to an embodiment of the present disclosure, the aging treatment may be a method known to those skilled in the art.

[0066] The present disclosure also provides applications of the above-mentioned Re-Fe-B permanent magnet materials in the fields of motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment, etc., preferably applications in embedded motors, especially applications as motor rotor magnets in embedded motors.

[0067] The present disclosure further provides a motor, wherein the motor comprises the Re-Fe-B permanent magnet material described above. Preferably, the motor is an embedded motor, wherein the Re-Fe-B permanent magnet material is embedded in the embedded motor.

[0068] A second aspect of the present disclosure provides an RTB-based permanent magnet material, which may optionally have or not have any one or more of the above-mentioned characteristics.

[0069] As for the RTB-based permanent magnet material described in the second aspect, the permanent magnet material has at least one cross-section, and the cross-section is divided into N regions from the magnet surface to the magnet core, where 3≤N≤10, and the coercive force at the junction of adjacent regions is the same, and along the magnet surface to the magnet core, the coercive force at the junction of each region gradually decreases in a direction parallel to the orientation direction.

[0070] According to the embodiment of the present disclosure, the coercivity at the boundary between adjacent regions is recorded as Hcj A The permanent magnetic material includes at least N regions, which are sequentially recorded as the first region, the second region, the third region, ..., and the Nth region from the surface of the magnet to the core of the magnet; for example, the coercive force at the junction of the first region and the second region is recorded as Hcj A12 The area ratio of the first region is recorded as S1; the coercivity at the junction of the second and third regions is recorded as Hcj A23 The area ratio of the second region is recorded as S2; the coercivity at the junction of the third and fourth regions is recorded as Hcj A34, the area ratio of the third region is recorded as S3; and so on; the coercivity at the junction of the (N-1)th region and the Nth region is recorded as Hcj A(n-1)n , the area proportion of the (N-1)th region is recorded as S (n-1) ; The coercivity at the junction of each region satisfies: Hcj A12 >Hcj A23 >Hcj A34 …>Hcj A(n-1)n .

[0071] According to an embodiment of the present disclosure, the permanent magnetic material is also referred to as a magnet.

[0072] According to an embodiment of the present disclosure, there is at least one cross section that divides the permanent magnetic material into N regions, with the core of the magnet as the center, and the N regions are symmetrically distributed. Preferably, the coercive force of the magnet is the same in the mirror-image regions.

[0073] According to the embodiment of the present disclosure, if the coercivity difference at the junction of adjacent regions is the same, that is, Hcj A12 -Hcj A23 =Hcj A23 -Hcj A34 =HcjA(n-2)(n-1)-Hcj A(n-1)n When the area of ​​each region satisfies: S1<S2<S3……<S n .

[0074] According to an embodiment of the present disclosure, the boundary between adjacent regions is an irregular curve.

[0075] According to an embodiment of the present disclosure, the boundaries of adjacent areas are non-linearly distributed without intersection points.

[0076] According to an embodiment of the present disclosure, the boundary between adjacent areas is arc-shaped.

[0077] According to an embodiment of the present disclosure, the arc shape is a regular curve, and the arc shape is symmetrical along its center line.

[0078] According to the embodiment of the present disclosure, the permanent magnetic material has at least one cross section with ΔHcj≥20kA / m; wherein ΔHcj is the coercivity difference between adjacent junctions, i.e. Hcj A12 -Hcj A23 or Hcj A23 -Hcj A34 , and so on.

[0079] According to the embodiment of the present disclosure, the cross-sectional area of ​​the permanent magnetic material from the magnet surface to the magnet core is S, the ratio of the area S1 of the first region to S satisfies: S1 / S≤1 / (2*N), and the area S of the Nth regionn The ratio to S is: 1 / N≤S n / S≤2 / N.

[0080] According to an embodiment of the present disclosure, in the cross section, the average content of heavy rare earth in each region of the permanent magnetic material is different.

[0081] According to an embodiment of the present disclosure, on the cross section, along the orientation direction, the heavy rare earth content of each region gradually decreases from the surface of the magnet to the core of the magnet.

[0082] According to an embodiment of the present disclosure, the difference in heavy rare earth content between the first region and the last region is ≤5 wt %; specifically, the difference is greater than 0.

[0083] According to an embodiment of the present disclosure, the difference in heavy rare earth content between adjacent regions is ≤3 wt %; specifically, the difference is greater than 0.

[0084] According to an embodiment of the present disclosure, there are at least three non-parallel planes in the permanent magnetic material, wherein in the three planes, along the direction perpendicular to the planes, the absolute value of the difference between the maximum coercive force at the edge position and the minimum coercive force at the core position is different:

[0085] In at least one plane, the absolute value of the difference between the maximum coercivity at the edge and the minimum coercivity at the core is δHcj a ≥40kA / m, for example, 40kA / m≤δHcj a ≤160kA / m;

[0086] In at least one plane, the absolute value of the difference between the maximum coercivity at the edge and the minimum coercivity at the core is δHcj b ≥20kA / m, for example, 20kA / m≤δHcj b ≤80kA / m;

[0087] In at least one plane, the absolute value of the difference between the maximum coercivity at the edge and the minimum coercivity at the core is δHcj c ≥5kA / m, for example, 5kA / m≤δHcj c ≤40kA / m.

[0088] According to an embodiment of the present disclosure, the demagnetization rate of the permanent magnetic material is 3% or less, preferably 2% or less, and more preferably 0.5% or less.

[0089] According to an embodiment of the present disclosure, R is a heavy rare earth element (HRE) or a light rare earth element; the heavy rare earth element (HRE) has a meaning well known in the art, and can be selected from one or more of gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y).

[0090] According to an embodiment of the present disclosure, T is selected from iron (Fe) or a mixture of iron and other metal elements. Preferably, the other metals may be selected from one or more transition metal elements other than iron.

[0091] Transition metal elements, as used herein, have a meaning generally known in the art and refer to metal elements in the d-block and ds-block of the periodic table. D-block elements include elements from Groups IIIB to VIIB, and Groups VIII, but exclude lanthanides and actinides; and ds-block elements include elements from Groups IB to IIB. Generally speaking, transition metal elements include elements from ten groups, from Groups 3 to 12, but exclude inner transition elements from the f-block (elements 58 to 71 in the periodic table are called 4f inner transition elements, and elements 90 to 103 are called 5f inner transition elements, all of which belong to the f-block).

[0092] According to an embodiment of the present disclosure, the other metals may be selected from one or more of copper (Cu), gallium (Ga), aluminum (Al), zirconium (Zr), titanium (Ti), tin (Sn), tantalum (Ta), and manganese (Mn).

[0093] According to an embodiment of the present disclosure, the permanent magnetic material may further contain M, wherein M is selected from one or more of transition metal elements, non-metallic elements, and light rare earth elements.

[0094] According to an embodiment of the present disclosure, the light rare earth element may be selected from cerium group rare earth elements, such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu).

[0095] According to an embodiment of the present disclosure, M is preferably selected from one or more of Cu, Ga, Al, Zr, Ti, Sn, Ta and Mn, such as one or more of Cu, Ga and Al.

[0096] According to an embodiment of the present disclosure, based on the mass of the permanent magnetic material, the mass percentage content of R is greater than or equal to 28.5% and less than or equal to 32.5%, examples of which may be 28.5%, 29.0%, 29.5%, 30.0%, 30.5%, 31.0%, 31.5%, 32.0% or 32.5%.

[0097] According to an embodiment of the present disclosure, based on the mass of the permanent magnet material, the mass percentage content of B is 0.88% or more and 1.05% or less, and examples thereof may be 0.88%, 0.90%, 0.92%, 0.95%, 0.98%, 1.00%, 1.02% or 1.05%.

[0098] According to an embodiment of the present disclosure, based on the mass of the permanent magnetic material, the total mass percentage content of M is greater than 0.1% and less than 4.0%, preferably greater than 0.3% and less than 3.5%, examples of which may be 0.3%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% or 3.5%.

[0099] According to an embodiment of the present disclosure, the permanent magnetic material contains Ga. Preferably, based on the mass of the permanent magnetic material, the mass percentage content of Ga is 0.1% or more and 0.6% or less, and examples thereof may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or 0.6%.

[0100] According to an embodiment of the present disclosure, the permanent magnetic material contains Co. Preferably, based on the mass of the permanent magnetic material, the mass percentage content of Co is 0% or more and 3.0% or less, preferably greater than 0% and 3.0% or less, and examples thereof may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9% or 3.0%.

[0101] According to an embodiment of the present disclosure, the permanent magnetic material includes Cu. Preferably, based on the mass of the permanent magnetic material, the mass percentage content of Cu is 0% or more and 0.4% or less, preferably greater than 0% and 0.4% or less, and examples thereof may be 0.1%, 0.2%, 0.3% or 0.4%.

[0102] According to an embodiment of the present disclosure, the balance of the permanent magnetic material is Fe and inevitable impurities, and the inevitable impurities are, for example, at least one of C, N, O, etc.

[0103] According to an embodiment of the present disclosure, when present, the C content is 400 to 800 ppm by mass based on the mass of the permanent magnetic material.

[0104] According to an embodiment of the present disclosure, when present, the O content is 300 to 900 ppm by mass based on the mass of the permanent magnetic material.

[0105] According to an embodiment of the present disclosure, when present, the N content is 400 to 800 ppm by mass based on the mass of the permanent magnetic material.

[0106] According to an embodiment of the present disclosure, when present, the sum of the mass of C, the mass of O and the mass of N based on the mass of the permanent magnetic material does not exceed 2000 ppm.

[0107] According to the embodiment of the present disclosure, the remanent magnetization at the boundary between adjacent regions is the same, and the remanent magnetization at the boundary gradually increases along the orientation direction.

[0108] According to the embodiment of the present disclosure, the residual magnetism at the junction of adjacent regions is Br T The remanent magnetization at the junction of the first and second regions is denoted as Br T12 The remanent magnetization at the junction of the second and third regions is denoted as Br T23 The remanent magnetism at the junction of the third and fourth regions is denoted as Br T34 ; And so on; The remanence at the junction of the (N-1)th region and the Nth region is denoted as Br T(n-1)n ; The remanent magnetism at the junction of each region satisfies, Br T12 <Br T23 <Br T34 ...<Br T(n-1)n。

[0109] According to the embodiment of the present disclosure, ΔBr≤0.04T; wherein ΔBr is the residual magnetization difference between adjacent junctions, i.e., Br T23 -Br T23 or Br T34 -Br T23 , and so on.

[0110] The present disclosure also provides a method for preparing a permanent magnetic material, the method comprising the following steps:

[0111] (a) Preparation of RTB magnet matrix;

[0112] (b) placing a diffusion source containing heavy rare earth on the surface of the substrate;

[0113] (c) subjecting the magnet material obtained in step (b) to grain boundary diffusion treatment and aging treatment to obtain a permanent magnet material.

[0114] According to an embodiment of the present disclosure, in step (a), the RTB-based magnet matrix can be a matrix known in the art, for example, a matrix prepared using raw materials known in the art.

[0115] According to an embodiment of the present disclosure, in step (b), the diffusion source containing heavy rare earth is selected from pure metals of Dy and / or Tb, or alloys of Dy and / or Tb such as hydrides, oxides, hydroxides, fluorides, etc.

[0116] According to an embodiment of the present disclosure, in step (b), the diffusion source containing heavy rare earth may further include RH, and the RH is selected from one or two or more of Nd, La, Ce, Pr, Ho, and Gd to form a mixed rare earth diffusion source.

[0117] According to an embodiment of the present disclosure, in step (b), the proportion of pure metal, compound, or alloy containing Dy and / or Tb in the diffusion source containing heavy rare earths accounts for more than 50% of the total amount of the diffusion source containing heavy rare earths. Because heavy rare earths play an irreplaceable role in improving heat resistance, it is necessary to control the proportion of pure metal, compound, or alloy containing Dy and / or Tb in the heavy rare earth diffusion source. If the proportion of pure metal, compound, or alloy containing Dy and / or Tb is lower than the above ratio, the effect of improving the heat resistance of the NdFeB magnet will be insignificant.

[0118] According to an embodiment of the present disclosure, in step (b), the diffusion source containing heavy rare earth can be in the form of a powder or a slurry containing an organic solvent.

[0119] According to the embodiment of the present disclosure, in step (b), the diffusion source containing heavy rare earth is arranged on the surface of the magnet to form a coating surface, and the coating surface is 1, 2, 3, 4, 5 or 6, and the coating surface includes at least one plane parallel to the central axis of the motor, wherein the area of ​​the coating area accounts for less than 100% of the area of ​​the plane of the magnet.

[0120] According to an embodiment of the present disclosure, in step (b), the diffusion source containing heavy rare earth is arranged on the surface of the magnet to form multiple coating surfaces, and at least one coating surface has a coating amount different from that of the other coating surfaces.

[0121] Preferably, among the plurality of coating surfaces, the coating amounts of any three or more coating surfaces are different.

[0122] According to the embodiments of the present disclosure, the coating amount refers to: RH category, RH content, weight, concentration, thickness, coating area, etc. have certain differences.

[0123] Preferably, in step (b), when the diffusion source containing heavy rare earth is in powder form, the average particle size of the powder containing heavy rare earth is 2-200 μm;

[0124] Preferably, in step (b), when the diffusion source containing heavy rare earth is an organic solvent slurry, the organic solvent is preferably an alcohol, ketone, or ether that is easily volatile and has low viscosity, and ethanol, acetone, or butanone may be selected.

[0125] Preferably, in step (b), when the diffusion source containing heavy rare earth is an organic solvent slurry, the weight ratio of the diffusion source containing heavy rare earth to the organic solvent is (70-95): (5-30).

[0126] According to the embodiment of the present disclosure, in step (b), the method of arranging the heavy rare earth-containing diffusion source on the magnet substrate can be carried out by vacuum evaporation, magnetron sputtering, screen printing, coating or burying.

[0127] According to an embodiment of the present disclosure, in step (c), the grain boundary diffusion treatment may be a method known to those skilled in the art, for example, a high-temperature diffusion treatment.

[0128] According to an embodiment of the present disclosure, the temperature of the grain boundary diffusion treatment may be 800° C. or higher, for example, 850 to 950° C., and examples thereof may be 800° C., 810° C., 820° C., 830° C., 840° C., 850° C., 860° C., 870° C., 880° C., 890° C., or 900° C. The time of the grain boundary diffusion treatment may be 5 hours or higher, for example, 10 to 50 hours, for example, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, or 50 hours.

[0129] Preferably, in step (c), the diffusion aging treatment further comprises a diffusion cooling temperature below 100°C.

[0130] According to an embodiment of the present disclosure, in step (c), the temperature of the aging treatment may be 700° C. or less, for example, 450 to 650° C., and examples thereof may be 450° C., 460° C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540° C., 550° C., 560° C., 570° C., 580° C., 590° C., 600° C., 610° C., 620° C., 630° C., 640° C., or 650° C. The aging treatment time may be 1 hour or more, for example, 1 to 10 hours, and examples thereof may be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0131] Alternatively, the aging treatment step may be performed after the following processing steps. The processing steps may be used to process the sintered magnet into a desired shape as needed. For example, the processing steps may include shaping processes such as cutting and grinding, and chamfering such as barrel polishing.

[0132] The present disclosure also provides applications of the above-mentioned Re-Fe-B permanent magnet materials in the fields of motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment, etc., preferably applications in embedded motors, especially applications as motor rotor magnets in embedded motors.

[0133] The present disclosure further provides a motor comprising the above-mentioned permanent magnetic material. Preferably, the motor is an embedded motor. Preferably, the permanent magnetic material is assembled in the embedded motor in an embedded manner.

[0134] It should be understood that the RTB-based permanent magnet material of the present disclosure can independently possess the technical features described in the first or second aspects above. However, this does not mean that the technical features of the first and second aspects must exist independently. Alternatively, the present disclosure also provides an RTB-based permanent magnet material having the technical features described in the first and second aspects above.

[0135] In other words, the RTB-based permanent magnet material can have both the technical features of the first aspect and the technical features of the second aspect described above. However, since the technical features of the first and second aspects have been described separately in this disclosure, the inventors have not repeated these combinations of features for the sake of space.

[0136] For example, the RTB-based permanent magnet material having a polyhedral structure provided in the first aspect of the present disclosure may also have at least one cross-section divided into N regions from the magnet surface to the magnet core, where 3≤N≤10, the coercivity at the junctions of adjacent regions being the same, and the coercivity at the junctions of the regions gradually decreasing in a direction parallel to the orientation direction from the magnet surface to the magnet core. The cross-section, N regions, and coercivity of the RTB-based permanent magnet material may further have any one or more of the characteristics described in the second aspect of the present disclosure.

[0137] For example, the RTB-based permanent magnet material provided in the second aspect of the present disclosure is characterized in that: R comprises a light rare earth element and a heavy rare earth element; the light rare earth element (RL) comprises at least one or two selected from neodymium (Nd) and praseodymium (Pr); the heavy rare earth element (RH) comprises at least one or two selected from dysprosium (Dy) and terbium (Tb); T comprises at least iron (Fe); and B is boron; the permanent magnet material has a polyhedral structure comprising at least three external surfaces, wherein the heavy rare earth content of the external surfaces of the polyhedral structure is different. The elemental composition, polyhedral structure, and heavy rare earth content of the external surfaces of the polyhedral structure of the RTB-based permanent magnet material may further have any one or more of the characteristics described in the first aspect of the present disclosure. Beneficial effects

[0138] On the one hand, the present disclosure can achieve the coercive force distribution that meets the actual needs of the motor for magnets by controlling the coercive force reduction in a specific direction, while effectively reducing the heavy rare earth content in the magnet and reducing product costs. The process method is also convenient for mass production.

[0139] The coercive force distribution characteristics of traditional homogeneous NdFeB permanent magnets or heavy rare earth diffused magnets are not fully compatible with the motor and cannot fully meet the optimal demagnetization strategy requirements of the motor. When the NdFeB permanent magnet disclosed in this invention is used in the motor, the permanent magnet cutting the magnetic field will also generate induced potential and induced current, and the generated reverse magnetic field is subject to the magnetic circuit design of the motor, and is often concentrated in two directions perpendicular to the central axis of the motor rotor. By adjusting the coercive force in the magnet, appropriately increasing the coercive force deceleration in the direction perpendicular to the central axis of the motor rotor, and appropriately reducing the coercive force deceleration in the direction parallel to the central axis of the motor rotor, the coercive force is gradually distributed and consistent with the reverse field distribution law in the motor. By distributing the heavy rare earth that increases the coercive force of the magnet to the area where the anti-demagnetization ability is most needed, the heavy rare earth content distribution in the magnet, the coercive force distribution of the magnet, and the reverse field distribution in the motor can be matched to the maximum extent, thereby being more in line with the safety protection strategy of the motor.

[0140] Under the condition of the same amount of heavy rare earth diffusion source, the present invention can obtain a magnet with a higher intrinsic coercive force increase, thereby reducing the production cost of the magnet.

[0141] On the other hand, the permanent magnet material disclosed in the present invention controls the coercive force gradient in a specific direction so that the coercive force distribution of the permanent magnet material meets the actual needs of the motor for magnets, while effectively reducing the heavy rare earth content in the magnet, reducing product costs, and the disclosed method is convenient for mass production. At the same time, the use of a NdFeB magnet matrix with a lower C, O, and N impurity content for diffusion treatment can provide better grain boundaries and better diffusion channels. The coercive force and remanence characteristics of the permanent magnet material disclosed in the present invention are different in different regions, so that the anti-demagnetization effect of different regions is different. From the surface of the magnet to the core, it can ensure that the magnet resists magnetic performance attenuation during application, achieving stable application. BRIEF DESCRIPTION OF THE DRAWINGS

[0142] FIG1 is a schematic structural diagram of the permanent magnetic material of Examples 1-5 of the present disclosure, where AA′ is the magnetization direction.

[0143] FIG2 is a schematic diagram of the coating method of heavy rare earth elements in Comparative Example 3.

[0144] FIG3 is a schematic diagram of specific positions of permanent magnetic materials in Examples 1-5 of the present disclosure.

[0145] FIG4 is a schematic diagram of the cutting method of the magnet material in Examples 6-9 of the present disclosure.

[0146] FIG5 is a schematic diagram showing the division of different regions on the cross section SCF1 in Example 6-1. DETAILED DESCRIPTION

[0147] The technical solutions of the present disclosure will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present disclosure and should not be construed as limiting the scope of protection of the present disclosure. All technologies implemented based on the above content of the present disclosure are included within the scope of protection intended by the present disclosure.

[0148] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0149] After diffusion, standard 7-7-Tmm blocks were machined to test overall performance. Overall magnetic properties were tested on a NIM-62000 machine. 1-1-1mm blocks were machined on the magnet surface and at a distance D from the surface to the core, and local magnetic properties were tested using PFM.

[0150] Outer surface S H The method for measuring the weight percentage content of heavy rare earth elements is as follows: an X-ray fluorescence spectrometer (XRF) is used to measure the heavy rare earth content x at a position 0.08-0.12 mm from the surface of the permanent magnet to the inside of the magnet (taking four corners + the center, a total of 5 measurement points, and taking the average of the heavy rare earth contents at these 5 positions).

[0151] Method for measuring the weight percentage content of heavy rare earth in the core of the magnet: Use an X-ray fluorescence spectrometer (XRF) to measure the heavy rare earth content within a radius of 2 mm around the geometric center point of any cross-section as y (take a total of 5 measurement points including the geometric center point of the cross-section, and take the average of the heavy rare earth contents at these 5 positions).

[0152] Demagnetization rate test method: A flux meter is used to measure the attenuation ratio of the magnetic flux of a single-piece magnet at room temperature (26°C) and high temperature (130°C*2h followed by air cooling).

[0153] Example 1

[0154] (1) Prepare the following raw materials for sintered NdFeB permanent magnets in weight percentage: 31% PrNd, 2% Co, 0.2% Cu, 0.1% Ga, 0.4% Al, 0.1% Zr, 1% B, and the balance Fe. Alloy flakes were prepared from the raw materials using a rapid-setting strip spinning method, and further processed into NdFeB blanks. 120 40-10-5 mm hexahedral samples were machined, with the surfaces divided into AA', BB', and CC' planes.

[0155] (2) a mixture of 50 wt% of metallic Tb powder, 3.5 wt% of toluene as an antioxidant, 1.5 wt% of polyethylene glycol-400 as a dispersant, and the balance of alcohol (hereinafter referred to as "Tb powder");

[0156] A mixture of 50 wt% of metal Dy powder, 3.5 wt% of toluene as an antioxidant, 1.5 wt% of polyethylene glycol-400 as a dispersant, and the balance of alcohol (referred to as "Dy powder") was prepared;

[0157] (3) Surfaces A and A', which are perpendicular to the orientation direction, are coated with 0.7% Tb powder (based on the magnet substrate). Surfaces B and B', which are parallel to the orientation direction and parallel to the motor's central axis, are coated with 0.4% Dy powder. Surfaces C and C', which are parallel to the orientation direction and perpendicular to the motor's central axis, are not coated. The coated magnets are subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0158] Example 2

[0159] Step (1) of Example 2 is the same as step (1) of Example 1.

[0160] (2) The preparation method of Tb powder is the same as that of Example 1;

[0161] Mixed metal PrNd powder (referred to as "PrNd powder") is prepared by mixing 50 wt% PrNd powder, 3.5 wt% toluene as an antioxidant, 1.5 wt% polyethylene glycol-400 as a dispersant, and the balance being alcohol;

[0162] (3) A mixture of 0.7% Tb powder and 0.5% PrNd powder was applied to the surfaces of surface A and surface A' perpendicular to the orientation direction. 0.2% Tb powder was applied to the surfaces of surface B and surface B' parallel to the orientation direction and the motor's central axis. Surfaces C and surface C' parallel to the orientation direction and perpendicular to the motor's central axis were not coated. The coated magnets were subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0163] Example 3

[0164] Step (1) of Example 3 is the same as step (1) of Example 1.

[0165] The Tb powder of Example 1 was used; 0.35% by weight of the sample was coated on surface A, perpendicular to the orientation direction; 0.2% by weight of the sample was coated on surfaces B and B', parallel to the orientation direction and the motor's central axis; and surfaces C and C', parallel to the orientation direction and perpendicular to the motor's central axis, were left uncoated. The coated magnets were subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0166] Example 4

[0167] Step (1) of Example 4 is the same as step (1) of Example 1.

[0168] The Tb powder of Example 1 was used; 0.35% Tb powder by weight was applied to surface B, which was parallel to the orientation direction and the motor's central axis. Surfaces C and C', which were parallel to the orientation direction and perpendicular to the motor's central axis, were left uncoated; and Surfaces A and A', which were perpendicular to the orientation direction, were left uncoated. The coated magnets were subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0169] Example 5

[0170] Step (1) of Example 5 is the same as step (1) of Example 1.

[0171] The Tb powder of Example 1 was used; 0.7% Tb powder by weight was applied to surfaces A and A', which were perpendicular to the orientation direction. 0.2% Tb powder was applied to four areas 1 mm inward from the edges of surfaces B and B', which were parallel to the orientation direction and the motor's central axis. Surfaces C and C', which were parallel to the orientation direction and perpendicular to the motor's central axis, were left uncoated. The coated magnets were subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0172] Comparative Example 1

[0173] The step (1) of Comparative Example 1 is the same as the step (1) of Example 1.

[0174] The Tb powder from Example 1 was used; 0.7% Tb powder by weight was applied to the surfaces of surface A and surface A' perpendicular to the orientation direction. The coated magnet was subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0175] Comparative Example 2

[0176] The step (1) of Comparative Example 2 is the same as the step (1) of Example 1.

[0177] The Tb and Dy powders described in Example 1 were used. 0.7% Tb powder by weight was applied to surfaces A and A' perpendicular to the orientation direction. 0.4% Dy powder was applied to surfaces B and B' parallel to the orientation direction and the motor's central axis. 0.4% Dy powder was applied to surfaces C and C' parallel to the orientation direction and perpendicular to the motor's central axis. The coated magnets were subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain gradient-distributed sintered NdFeB permanent magnets.

[0178] Comparative Example 3

[0179] The step (1) of Comparative Example 3 is the same as the step (1) of Example 1.

[0180] Using the Tb powder described in Example 1, as shown in Figure 2, taking surface A as an example, a coating of 0.7% Tb powder by weight was applied to a portion of the surface of surface A perpendicular to the orientation direction and half the total length of surface A. That is, the central 25% of the surface was coated with 0.7% Tb powder. The remaining area of ​​surface A was coated with 0.9% Tb powder by weight. Surface A' was coated in the same manner and over the same area as surface A. The coated magnet was then subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain a sintered NdFeB permanent magnet with a gradient distribution.

[0181] Comparative Example 4

[0182] The step (1) of Comparative Example 4 is the same as the step (1) of Example 1.

[0183] The Tb powder of Example 1 was used; 0.7% Tb powder by weight was applied to surfaces A and A' perpendicular to the orientation direction; surfaces B and B' parallel to the orientation direction and the motor's central axis were left uncoated; and 0.4% Dy powder was applied to surfaces C and C' parallel to the orientation direction and perpendicular to the motor's central axis. The coated magnets were subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 530°C for 5 hours to obtain sintered NdFeB permanent magnets with a gradient distribution.

[0184] The surface heavy rare earth content of each surface in Examples 1-5 and Comparative Examples 1-4 is shown in Table 2 below, and the corresponding Hcj, △Hcj on different surfaces and at a distance D from the surface, as well as the peak torque loss rate of the motor output after the 150°C endurance test are shown in Table 3 below, wherein Hcj-A1 is the Hcj at the geometric center of the surface of surface A, that is, the Hcj at the center point A1 in Figure 3, Hcj-A2 is the Hcj at a distance D = 2 mm from the surface in the vertical direction of plane A, that is, the Hcj at the center point A2 in Figure 3, △Hcj1 = (Hcj-A1) - (Hcj-A2), and the other B surfaces and C surfaces have the same definition.

[0185] Table 1: Coating methods and coating contents of heavy rare earth on the outer surfaces of Examples 1-5 and Comparative Examples 1-4

[0186] In Table 1: Surface A, A': perpendicular to the orientation direction; Surface B, B': parallel to the orientation direction and parallel to the motor center axis; Surface C, C': parallel to the orientation direction and perpendicular to the motor center axis.

[0187] The heavy rare earth content of the outer surfaces of the permanent magnetic materials prepared in Examples 1-5 and Comparative Examples 1-4 was tested; the test results are shown in Table 2 below.

[0188] Table 2 Heavy rare earth content on the outer surface (wt%)

[0189] In Table 2, “-” means that the heavy rare earth element was not coated or was not detected.

[0190] The magnetic properties of the permanent magnetic material prepared in the embodiment were tested at different positions (the material was divided and tested separately). The test results are shown in Table 3 below.

[0191] Table 3 Magnetic properties test results of permanent magnetic materials in Examples 1-5 and Comparative Examples 1-4

[0192] In the present disclosure, ΔHcjn≤0.3 kOe / mm, ΔHcjm≥0.3 kOe / mm, 0.3 kOe / mm=47.76 (KA / m) / 2 mm, therefore ΔHcjn≤47.76 (KA / m) / 2 mm, ΔHcjm≥47.76 (KA / m) / 2 mm.

[0193] S parallel to the magnet orientation direction H The absolute value of the coercivity difference at the distance D1 is ΔHcjm, and within the range of distance D1 (D1 = 2 mm), ΔHcjm = |ΔHcj2| / D1 / 79.6;

[0194] For surface A, the absolute value of the coercivity difference at distance D2 is ΔHcjnA; within the range of distance D2 (D2 = 2 mm), ΔHcjnA = |ΔHcj1| / D2;

[0195] For the C surface, the absolute value of the coercivity difference at the distance D2 is ΔHcjnB; within the range of the distance D2 (D2=2mm), ΔHcjnB=|ΔHcj3| / D2.

[0196] The calculation results of ΔHcjm, ΔHcjnA and ΔHcjnB are shown in Table 4 below.

[0197] Table 4 Magnetic properties test results of permanent magnetic materials in Examples 1-5 and Comparative Examples 1-4

[0198] Through the test data of Example 1 and Comparative Example 1, it can be concluded that in Example 1, the S parallel to the orientation direction of the magnet H , the absolute value of the coercivity difference per unit distance is ΔHcjm=ΔHcj2 / 2mm / 79.6=0.45kOe / mm, other S H Face and / or S L The ΔHcjn of the surfaces are 0.11kOe / mm and 0.03kOe / mm respectively, with ΔHcjm>ΔHcjnA or ΔHcjnB (that is, ΔHcjm>ΔHcjnA, and ΔHcjm>ΔHcjnB), ΔHcjnA or ΔHcjnB≤0.3kOe / mm, ΔHcjm≥0.3kOe / mm, and the NdFeB permanent magnet with a specific characteristic coercive force distribution has enhanced Hcj at its characteristic position, and the magnet's resistance to specific reverse demagnetization field has been significantly improved. Therefore, the peak torque loss rate of the motor using the magnet of Example 1 after high-temperature durability test is low, which is 1.67%, which can meet the needs of most high-performance motors. Similarly, Examples 2-5, which use different diffusion methods and different diffusion sources, also meet the coercive force distribution requirements of the specific characteristics of ΔHcjm>ΔHcjnA or ΔHcjnB, ΔHcjnA or ΔHcjnB≤0.3kOe / mm, and ΔHcjm≥0.3kOe / mm. Similarly, the peak torque loss rate of the motors using Examples 2-5 is low, which can meet the needs of most high-performance motors.

[0199] Comparative Example 1, although other S H Face and / or S LThe ΔHcjn of the surface meets the requirement of ΔHcjn≤0.3kOe / mm, but ΔHcjm is only 0.02kOe / mm, which does not meet the requirements of ΔHcjm>ΔHcjn and ΔHcjm≥0.3kOe / mm. Similarly, Examples 2-4 cannot simultaneously meet the characteristics of ΔHcjm>ΔHcjn, ΔHcjn≤0.3kOe / mm, and ΔHcjm≥0.3kOe / mm. Therefore, the coercive force distribution in its magnet does not match the actual operating conditions of high-performance motors, and there is insufficient performance or excess performance. At the same time, even though the peak torque loss rate of Example 4 is also low, it uses an excessive diffusion method, which increases rare earth consumption, resulting in a waste of resources and costs, and is not the preferred protection method of this application.

[0200] Example 6

[0201] (1) Substrate Preparation: The permanent magnet material was prepared by high-frequency melting NdPr, Co, Al, Fe, Cu, Ga, Ti, and ferroboron with a purity of at least 99% by weight in an argon atmosphere, and casting the melt onto a chill roll to form an alloy sheet, wherein the raw material contents were 31.5 wt% NdPr, 1.0 wt% Co, 0.5 wt% Al, 0.2 wt% Cu, 0.2 wt% Ga, 0.18 wt% Ti, 0.98 wt% B, and the balance was iron and unavoidable impurities. The alloy was hydrogenated and pulverized into a coarse powder, which was then jet-milled to obtain a magnetic powder with a particle size of D50 = 3.5 μm. The above-mentioned air flow milled powder was added with 0.2wt% of lubricant zinc stearate and mixed for 2 hours. The mixture was then formed at room temperature and in an orientation field environment with a magnetic field strength of 2T. The green body was then placed in a vacuum sintering furnace, sintered at 1070°C for 6 hours, and aged at 520°C for 5 hours to obtain the NdFeB magnet matrix M10.

[0202] The above-mentioned NdFeB matrix is ​​cut into hexahedral magnet pieces with a size of 10-8-6 mm along the orientation direction, which are divided into ABCDEF faces, among which face A and face D, face B and face E, face C and face F are opposite faces, and the direction perpendicular to face AD ​​is the orientation direction, as shown in Figure 1.

[0203] A D10-10mm sample column (10mm diameter, 10mm length) was machined onto an M10 magnet for performance testing. Magnetic properties were tested using a NIM-62000 at a temperature of 20±3°C, yielding a matrix Br of 1.412T and a matrix Hcj of 1169kA / m. Using a Bruker carbon-sulfur analyzer and an oxygen-nitrogen-hydrogen analyzer, the M10 magnet matrix exhibited a carbon content of 640ppm, an oxygen content of 510ppm, and a nitrogen content of 460ppm.

[0204] (2) Preparation of a diffusion source containing heavy rare earth: TbF3 powder with an average particle size of 4 μm was mixed with anhydrous ethanol to prepare a diffusion source Y1, wherein the concentration of the TbF3 powder was 80 wt%;

[0205] (3) Apply the diffusion source Y1 to the four surfaces parallel to the orientation direction of the magnet, namely, the C, F, B, and E surfaces in Figure 1; the thickness between the C and F surfaces is 20 μm; the thickness between the B and E surfaces is 15 μm;

[0206] (4) The NdFeB magnet material obtained in step (3) is subjected to a grain boundary diffusion treatment at 900°C for 15 hours and an aging treatment at 550°C for 4 hours to prepare multiple groups of diffused NdFeB magnets M11.

[0207] (5) The diffused NdFeB magnet M11 is cut arbitrarily according to different cutting methods to obtain different cross sections, where Hcj B is the coercive force of any cross section intersecting the magnet surface; Hcj C The magnet pieces of Examples 6-1 to 6-6 below are all derived from Example 6.

[0208] Example 6-1

[0209] Along the center point AE of the adjacent side of the hexahedral magnet sheet A and E, and the center point AB of the adjacent side of the A and B sides, that is, the dotted line ① perpendicular to the ground in Figure 1, the A and D sides are bisected to obtain a cross section S parallel to the C and F sides. CF1 ;

[0210] Hc CF1B Hcj is the coercive force of the surface where the cross section SCF1 intersects the B surface; CF1C is the coercive force of the core of cross section SCF1; CF1 On the cross section, the coercivity is calculated according to Hcj A12 =Hcj CF1B -(Hcj CF1B -Hcj CF1C ) / 3、Hcj A23 =Hcj CF1B -2*(Hcj CF1B -Hcj CF1C ) / 3, the cross section was divided into three equal regions. The specific distribution is shown in Figure 2. The intersection of adjacent regions is a regular curve, and the arc is symmetrical along its centerline. The area proportions of different regions are measured as S1, S2, and S3. The difference between the maximum and minimum coercivity values ​​measured within the cross section is recorded as δHcj.

[0211] Example 6-2

[0212] Along the center point AF of the adjacent sides of the hexahedral magnet sheet A and F, and the center point AC of the adjacent sides of the A and C surfaces, that is, the dotted line ② perpendicular to the ground in Figure 1, the A and D surfaces are bisected to obtain a cross section S parallel to the B and E surfaces. BE1 ;

[0213] Hc BE1B is the cross section S BE1 The coercivity of the surface intersecting with the B surface; Hcj BE1C is the cross section S BE1 The coercive force of the core; in the S BE1 On the cross section, the coercivity is calculated according to Hcj A12 =Hcj BE1B -(Hcj BE1B -Hcj BE1C ) / 3、Hcj A23 =Hcj BE1B -2*(Hcj BE1B -Hcj BE1C ) / 3 differences are evenly distributed, and the cross section is divided into three areas. The junctions of adjacent areas are regular curves, and the arcs are symmetrical along their center lines. The area proportions of different areas are measured.

[0214] Example 6-3

[0215] Along the adjacent edges of the A and B faces of the hexahedral magnet sheet, and the adjacent edges of the D and E faces (cut diagonally along the C and F faces), that is, the dotted line ③ in Figure 1, the C and F faces are divided into two equal parts along the diagonal line; the division method of each cross-sectional area is the same as that of Example 6-1.

[0216] Example 6-4

[0217] The same as in Example 6-1, the C surface and the F surface are cut into two equal parts, that is, the dotted line ④ in Figure 1; the division method of each cross-sectional area is the same as in Example 6-1.

[0218] Example 6-5

[0219] The same as in Example 6-2, the C surface and the F surface are cut into two equal parts, that is, the dotted line ⑤ in Figure 1; the division method of each cross-sectional area is the same as in Example 6-2.

[0220] Example 6-6

[0221] The same as Example 6-1, the point between the C surface and the F surface is the dotted line ⑥ perpendicular to the ground in Figure 1; the division method of each area of ​​the cross section is the same as Example 6-1.

[0222] Example 7

[0223] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0224] Step (2) Preparation of a diffusion source containing heavy rare earth: TbF3 powder with an average particle size of 4 μm is mixed with anhydrous ethanol to prepare a diffusion source Y1, wherein the concentration of the TbF3 powder is 80 wt%;

[0225] The diffusion source Y2 was prepared by mixing DyF3 powder with an average particle size of 3 μm with anhydrous ethanol, wherein the concentration of the DyF3 powder was 85 wt %.

[0226] Step (3) Diffusion sources Y1 and Y2 are coated on four surfaces parallel to the orientation direction of the magnet, wherein the C and F surfaces have diffusion sources Y1, 50 μm; the B and E surfaces have diffusion sources Y2, 10 μm;

[0227] Example 7-1

[0228] The cutting method of the sintered NdFeB permanent magnet of this embodiment is the same as that of Example 6-1; however, the cut magnets are derived from Example 7.

[0229] Example 8

[0230] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0231] Step (2) Preparation of a diffusion source containing heavy rare earth: TbH powder with an average particle size of 3.5 μm is mixed with anhydrous ethanol to prepare a diffusion source Y3, wherein the concentration of the TbH powder is 60 wt%;

[0232] Diffusion source Y4 was prepared by mixing TbH powder with an average particle size of 3.5 μm and DyH powder with an average particle size of 3 μm in a ratio of 1:1 to form a mixed powder, which was then mixed and stirred with anhydrous ethanol. The concentration of the mixed powder was 75 wt %.

[0233] Step (3) Diffusion sources Y3 and Y4 are coated on the six surfaces of the magnet, wherein the C and F surfaces have diffusion sources Y3, 30 μm; the B and E surfaces have diffusion sources Y4, 15 μm; the A and D surfaces have diffusion sources Y4, 5 μm;

[0234] Example 8-1

[0235] The cutting method of the sintered NdFeB permanent magnet of this embodiment is the same as that of Example 6-2; however, the cut magnets are from Example 8.

[0236] Example 9

[0237] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0238] Step (2) Preparation of a diffusion source containing heavy rare earth: TbH powder with an average particle size of 3.5 μm is mixed with anhydrous ethanol to prepare a diffusion source Y3, wherein the concentration of the TbH powder is 60 wt%;

[0239] Step (3) coating the diffusion source Y3 on two surfaces perpendicular to the orientation direction of the magnet, namely, surface A and surface D, wherein surface A: diffusion source Y3, 40 μm; surface D: diffusion source Y3, 20 μm;

[0240] Example 9-1

[0241] The cutting method of the sintered NdFeB permanent magnet of this embodiment is the same as that of Example 6-3; however, the cut magnets are derived from Example 9.

[0242] Comparative Example 5

[0243] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0244] In step (1), the substrate is prepared as follows: the permanent magnet material is prepared by high-frequency melting NdPr, Co, Al, Fe, Cu, Ga, Zr, and ferroboron with a purity of at least 99% by weight in an argon atmosphere, and the melt is cast onto a chill roll to form an alloy sheet, wherein the raw material content is 31wt% NdPr, 0.8wt% Co, 0.5wt% Al, 0.2wt% Cu, 0.15wt% Ga, 0.10wt% Zr, 0.94wt% B, and the balance is iron and unavoidable impurities. The alloy is hydrogenated and crushed into a coarse powder, which is then jet-milled to obtain a magnetic powder with a particle size D50 of 3.5μm. The above-mentioned air flow milled powder was added with 1.0wt% of lubricant zinc stearate and mixed for 2 hours. The mixture was then formed at room temperature and in an orientation field with a magnetic field strength of 2T. The green body was then placed in a vacuum sintering furnace, sintered at 1030°C for 6 hours, and aged at 550°C for 6 hours to obtain the NdFeB magnet matrix M20.

[0245] A D10-10mm sample column (10mm diameter, 10mm length) was machined on an M20 magnet for performance testing. The matrix Br was measured to be 1.358T and the matrix Hcj was 1480kA / m. Using a Bruker carbon-sulfur analyzer and an oxygen-nitrogen-hydrogen analyzer, the carbon content of M1 was 767ppm, the oxygen content was 683ppm, and the nitrogen content was 670ppm.

[0246] Comparative Example 5-1

[0247] The cutting method of the sintered NdFeB permanent magnets in this embodiment is the same as that in Example 6-4; however, the cut magnets are from Comparative Example 5.

[0248] Comparative Example 6

[0249] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0250] Step (2) Preparation of a diffusion source containing heavy rare earth: TbH powder with an average particle size of 3.5 μm is mixed with anhydrous ethanol to prepare a diffusion source Y3, wherein the concentration of the TbH powder is 60 wt%;

[0251] Step (3) applying the diffusion source Y1 to the B, C, E, and F surfaces parallel to the orientation direction of the magnet with a thickness of 20 μm;

[0252] Comparative Example 6-1

[0253] The cutting method of the sintered NdFeB permanent magnets in this embodiment is the same as that in Example 6-5; however, the cut magnets are from Comparative Example 6.

[0254] Comparative Example 7

[0255] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0256] Step (2) Preparation of a diffusion source containing heavy rare earth: TbH powder with an average particle size of 3.5 μm is mixed with anhydrous ethanol to prepare a diffusion source Y3, wherein the concentration of the TbH powder is 60 wt%;

[0257] Step (3) applying the diffusion source Y1 to the A, B, C, D, E, and F surfaces of the magnet with a thickness of 20 μm;

[0258] Comparative Example 7-1

[0259] The cutting method of the sintered NdFeB permanent magnets in this embodiment is the same as that in Example 6-5; however, the cut magnets are from Comparative Example 7.

[0260] Comparative Example 8

[0261] The preparation method of the sintered NdFeB permanent magnet of this embodiment is basically the same as that of Example 6, except that:

[0262] Step (2) Preparation of a diffusion source containing heavy rare earth: TbH powder with an average particle size of 3.5 μm is mixed with anhydrous ethanol to prepare a diffusion source Y3, wherein the concentration of the TbH powder is 60 wt%;

[0263] Step (3) coating the diffusion source Y1 on the A, B, C, D, E, and F surfaces of the magnet, 2 mm away from the edge of the magnet, and leaving the remaining central area uncoated, with a thickness of 40 μm;

[0264] Comparative Example 8-1

[0265] The cutting method of the sintered NdFeB permanent magnets in this embodiment is the same as that in Example 6-5; however, the cut magnets are from Comparative Example 8.

[0266] Table 5 Detection performance, area and heavy rare earth content of each magnet in the examples and comparative examples

[0267] Table 1 (continued)

[0268] Through Example 6-1 to Example 8-1, it was found that: A As the dividing line, the magnet satisfies the coercivity Hcj of each region A12 >Hcj A23 >Hcj A34 …>Hcj A(n-1)n , satisfying the remanence: Br T12 <Br T23 <Br T34 ...<Br T(n-1)n , when the magnet satisfies the magnet S1<S2<S3……<S n , and the area of ​​the first region S1 / S≤1 / (2*N), and the area of ​​the Nth region 1 / N≤S n When / S≤2 / N, the demagnetization rate of the permanent magnet material is less than 2%, the product has excellent stability and is more suitable for embedded motor applications.

[0269] The product of Comparative Example 5-1 has a combined C, O, and N content of 2120 ppm. Increasing the C, O, and N contents hinders the deep diffusion of the magnet, leading to uneven diffusion and an excessively large S3 area. The demagnetization rate of the magnet is 3.21, resulting in poor stability. Furthermore, in Comparative Examples 6-1 and 7-1, where four or six surfaces are evenly coated, excessive diffusion of the magnet can lead to waste of heavy rare earth resources. Furthermore, by employing a diffusion coating method with varying coating amounts on at least three planes, the diffusion depth and effect more closely align with the actual demagnetization-prone areas of the magnet during motor operation, achieving efficient application of heavy rare earths. Furthermore, the squareness can be guaranteed to be ≥0.9, ensuring the magnet's anti-demagnetization capability.

[0270] Comparative Example 8-1 adopts the method of coating only the edge and corner areas of the magnet. This method ignores the fact that the diffusion speed of the magnet increases sharply with the increase of diffusion depth. The core will lack sufficient anti-demagnetization ability and the demagnetization rate of the magnet will also increase.

[0271] The above is an exemplary description of the embodiments of the present disclosure. However, the scope of protection of the present disclosure is not limited to the above-mentioned embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. An R-T-B series permanent magnetic material with a polyhedral structure, characterized in that, R includes light rare earth elements and heavy rare earth elements; The light rare earth element RL includes at least one or both selected from neodymium and praseodymium; The heavy rare earth element RH includes at least one or both selected from dysprosium and terbium; T contains at least iron; B is boron; The permanent magnet material has a polyhedral structure, and the polyhedral structure includes at least 3 outer surfaces, and the heavy rare earth contents on the outer surfaces of the polyhedral structure are different; Among the outer surfaces of the polyhedral structure, there is at least one outer surface S H , and the weight percentage content of heavy rare earth elements of this outer surface S H is higher than the weight percentage content of heavy rare earth in the polyhedral core; In the polyhedral structure, other outer surfaces except the outer surface S H are called S L ; the outer surface S L is parallel to the magnet orientation direction of the permanent magnet material, and / or, the outer surface S L is not parallel to the central axis direction of the electric machine in which the permanent magnet material is located.

2. The permanent magnetic material according to claim 1, wherein After the permanent magnet material undergoes a durability test at 150 °C, the loss rate of the motor output peak torque is 5% or less. Preferably, when the number of outer surfaces of the polyhedron is n, the number n of the outer surfaces S H is H such that: 1 ≤ n H ≤ n. Preferably, the permanent magnet material further contains or does not contain M, and M is selected from one or more of transition metal elements and non-metal elements. Preferably, based on the mass of the permanent magnet material, the mass percentage content of R is 28.5% or more and 32.5% or less. Preferably, based on the mass of the permanent magnet material, the mass percentage content of B is 0.88% or more and 1.05% or less. Preferably, based on the mass of the permanent magnet material, the total mass percentage content of M is 0.1% or more and 4.0% or less. Preferably, based on the mass of the permanent magnet material, the sum of the masses of C, O, and N does not exceed 2000 ppm.

3. The permanent magnetic material according to claim 1 or 2, characterized in that, The coercivity of the surface of the permanent magnet material to the core of the permanent magnet material shows a decreasing trend; For S parallel to the magnet orientation direction H For the plane, the absolute value of the coercivity difference of the distance D1 is ΔHcjm. For example, within the range of the distance D1, ΔHcjm = |ΔHcj| / D1; For other S H plane and / or S L plane, the absolute value of the coercivity difference at distance D2 is ΔHcjn; for example, within the range of distance D2, ΔHcjn = |ΔHcj| / D2; When D1 = D2, and the starting points of D1 and D2 are at equal distances from the magnet surface, ΔHcjm > ΔHcjn.

4. The permanent magnet material according to any one of claims 1-3, characterized in that, The distance D1 or D2 represents the distance between any two points between the surface of the permanent magnet material and its core. Preferably, for the S surface that is parallel to the magnet orientation direction and parallel to the central axis of the motor, the absolute value of the difference in coercive force per unit distance is ΔHcjm. H The absolute value of the difference in coercive force per unit distance is ΔHcjm. Preferably, when the polyhedron has a non - hexahedron structure, the angle between the S H face of the magnet and the orientation direction of the magnet is α, and α ≤ 45°. Preferably, ΔHcjn ≤ 0.3 kOe / mm, ΔHcjm ≥ 0.3 kOe / mm.

5. The permanent magnet material according to any one of claims 1-4, characterized in that, The permanent magnet material has at least one cross-section. From the magnet surface to the magnet core, the cross-section is divided into N regions, where 3 ≤ N ≤ 10. The coercivity at the junction of adjacent regions is the same, and along the direction from the magnet surface to the magnet core, in the direction parallel to the orientation direction, the coercivity at the junction of each region gradually decreases. Preferably, when the difference in coercive force at the junction of adjacent regions is the same, i.e., Hcj A12 -Hcj A23 =Hcj A23 -Hcj A34 ……=HcjA(n - 2)(n - 1)-Hcj A(n-1)n , the areas of the regions satisfy: S1 < S2 < S3…… < S n ; The material includes at least N regions, which are sequentially denoted as the first region, the second region, the third region, ……, and the Nth region from the magnet surface to the magnet core; the coercivity at the junction of the first region and the second region is denoted as Hcj A12 , the area ratio of the first region is denoted as S1; the coercivity at the junction of the second region and the third region is denoted as Hcj A23 , the area ratio of the second region is denoted as S2; the coercivity at the junction of the third region and the fourth region is denoted as Hcj A34 , the area ratio of the third region is denoted as S3; and so on; the coercivity at the junction of the (N - 1)th region and the Nth region is denoted as Hcj A(n-1)n , the area ratio of the (N - 1)th region is denoted as S (n-1) ; Preferably, the coercive force at the junction of each region satisfies: Hcj A12 > Hcj A23 > Hcj A34 …… > Hcj A(n-1)n . Preferably, the junction of adjacent regions is an irregular curve; Preferably, the junction of adjacent regions is a non-linear distribution without intersections; Preferably, the junction of adjacent regions is arc-shaped; Preferably, the arc shape is a regular curve and is symmetric along its center line.

6. The permanent magnetic material according to claim 5, wherein The permanent magnetic material has at least one cross-section where △Hcj ≥ 20 kA / m; where △Hcj is the difference in coercivity at the adjacent junction, i.e., Hcj A12 - Hcj A23 or Hcj A23 - Hcj A34 , and so on. Preferably, the cross-sectional area of the permanent magnetic material from the magnet surface to the magnet core is S, the ratio of the area S1 of the first region to S is S1 / S ≤ 1 / (2*N), and the ratio of the area of the Nth region to S is: 1 / N ≤ S n / S ≤ 2 / N. n / S ≤ 2 / N. Preferably, on the cross-section, the average heavy rare earth content of each region of the permanent magnet material is different. Preferably, on the cross-section, along the orientation direction, the heavy rare earth content of each region gradually decreases from the magnet surface to the magnet core. Preferably, the difference in the heavy rare earth content between the first region and the last region is ≤ 5 wt%. Preferably, the difference in the heavy rare earth content between adjacent regions is ≤ 3 wt%. Preferably, there are at least three non-parallel planes in the permanent magnet material. Among the three planes, along the direction perpendicular to the plane, the absolute values of the differences between the maximum coercivity at the edge position and the minimum coercivity at the core position are different: In at least one plane, the absolute value δHcj of the difference between the maximum value of the edge position coercivity and the minimum value of the core position coercivity a ≥ 40 kA / m, for example 40 kA / m ≤ δHcj a ≤ 160 kA / m; In at least one plane, the absolute value δHcj of the difference between the maximum value of the edge position coercivity and the minimum value of the core position coercivity b ≥ 20 kA / m, for example 20 kA / m ≤ δHcj b ≤ 80 kA / m; In at least one plane, the absolute value of the difference δHcj between the maximum value of the coercivity at the edge position and the minimum value of the coercivity at the core position c ≥ 5 kA / m, for example 5 kA / m ≤ δHcj c ≤ 40 kA / m. Preferably, the demagnetization rate of the permanent magnet material is 3% or less. Preferably, the remanence at the junction of adjacent regions is the same, and the remanence at the junction gradually increases along the orientation direction; The residual magnetism at the junction of adjacent regions is denoted as Br T， The residual magnetism at the junction of the first region and the second region is denoted as Br T12 ; The residual magnetism at the junction of the second region and the third region is denoted as Br T23 ; The residual magnetism at the junction of the third region and the fourth region is denoted as Br T34 ; And so on; The residual magnetism at the junction of the (N - 1)th region and the Nth region is denoted as Br T(n-1)n ; The residual magnetism at the junction of each region satisfies that Br T12 <Br T23 <Br T34 ……<Br T(n-1)n。 Preferably, △Br ≤ 0.04T; where △Br is the residual magnetic difference at the adjacent junction, that is, Br T23 -Br T23 or Br T34 -Br T23 , and so on.

7. The preparation method of the permanent magnetic material according to any one of claims 1-6, characterized in that, Wherein the method includes the following steps: (a) Coating mixture A and / or mixture B on a plane perpendicular to the orientation direction of the magnet substrate, and coating mixture A and / or mixture B on a plane parallel to the orientation direction of the magnet substrate; (b) Subjecting the neodymium iron boron magnet material obtained in step (a) to grain boundary diffusion treatment and aging treatment to obtain a sintered neodymium iron boron permanent magnet with a gradient distribution.

8. The method according to claim 7, wherein Both mixture A and / or mixture B include: powder of RH and / or powder of RL. Preferably, when mixture A and / or mixture B contains Dy, the percentage of Dy element in the weight of the magnet substrate is 0.3-1.2%, and when mixture A and / or mixture B contains Tb, the percentage of Tb element in the weight of the magnet substrate is 0.1-0.7%. According to an embodiment of the present disclosure, when mixture A and / or mixture B contains Pr and / or Nd, the percentage of Pr and / or Nd in the weight of the magnet substrate is 0.3-1.2%.

9. The method according to claim 7, wherein The method includes thermal diffusion treatment and tempering treatment.

10. Application of the permanent magnet material according to any one of claims 1-6 in fields such as motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment, etc., preferably in embedded motors, and particularly as a motor rotor magnet steel in embedded motors. Preferably, a motor, wherein the motor includes the Re-Fe-B series permanent magnet material according to any one of claims 1-6.

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