Neodymium-iron-boron magnet, manufacturing method therefor, and use thereof

Abstract

Disclosed in the present invention are a neodymium-iron-boron magnet, a manufacturing method therefor, and the use thereof. In the neodymium-iron-boron magnet, a first easy-demagnetization zone, a second easy-demagnetization zone, a third easy-demagnetization zone and a fourth easy-demagnetization zone have the same heavy-rare-earth content; a first transition zone, a second transition zone, a third transition zone and a fourth transition zone have the same heavy-rare-earth content; the content ratio of Tb in a non-easy demagnetization zone to that in the first easy-demagnetization zone is (0-0.9):1; the content ratio of Dy in the first easy-demagnetization zone to that in the non-easy demagnetization zone is (0-0.9):1; the content ratio of Tb in the first transition zone to that in the first easy-demagnetization zone is (0.8-1):1. The neodymium-iron-boron magnet of the present invention can reduce the attenuation of a surface magnetic field strength and magnetic flux of the neodymium-iron-boron magnet while ensuring remanence, and has good anti-demagnetization performance.

Description

Neodymium-iron-boron magnet, method for preparing the same and use thereof TECHNICAL FIELD

[0001] The present application relates to a neodymium-iron-boron magnet, a method for preparing the same and use thereof. BACKGROUND

[0002] Since the advent of neodymium-iron-boron permanent magnet, it has been widely used in the fields of automobile, wind power, household appliance, industrial robot, etc. Due to different working conditions in different fields, the performance of the magnetic steel in the field is also required to be different. In recent years, new energy vehicles have developed rapidly, and the demand for magnetic steel of main drive motor has increased dramatically. Since the normal working temperature of the main drive motor mainly concentrates in the range of 120-180℃, the neodymium-iron-boron material needs to have higher coercivity and thermal stability. In order to improve the temperature resistance of the neodymium-iron-boron permanent magnet, a large amount of heavy rare earth Dy and Tb is usually added to increase the anisotropic field of the main phase magnetic crystal. However, the heavy rare earth resources are scarce and expensive, which seriously restricts the application of the neodymium-iron-boron magnet in various industries.

[0003] With the increasing demand for high-performance magnets, the grain boundary diffusion technology has gradually been known and accepted by everyone. The conventional grain boundary diffusion technology adopts a physical vapor deposition method to deposit a diffusion source on the surface of the magnet, and then penetrates the diffusion source into the magnet along the grain boundary under high temperature and certain pressure. The biggest advantage of this technology is that it can greatly improve the coercivity using a small amount of heavy rare earth while keeping the remanence almost unchanged. In terms of effective utilization rate of heavy rare earth, the traditional grain boundary diffusion product has been greatly improved compared with the non-grain boundary diffusion product.

[0004] However, in the actual use of neodymium-iron-boron, the performance requirements of each part of the magnet are not the same. For example, in the motor, since the reverse magnetic field generated after the coil is energized in the motor is not a uniform magnetic field, how to design a neodymium-iron-boron magnet according to the needs of different regions to meet the needs of different applications while ensuring the coercivity and remanence, and also having good anti-demagnetization ability. SUMMARY

[0005] The present application mainly provides a neodymium-iron-boron magnet, a method for preparing the same and use thereof to overcome the poor anti-demagnetization performance of the neodymium-iron-boron magnet in the prior art. The neodymium-iron-boron magnet of the present application can reduce the decay of the surface magnetic and magnetic flux of the neodymium-iron-boron magnet while ensuring the remanence, and has good anti-demagnetization performance.

[0006] The present application provides a neodymium-iron-boron magnet, a method for preparing the same and use thereof to overcome the defects in the prior art.

[0007] The present application mainly solves the above technical problems through the following technical solutions.

[0008] In the research process of the present application, by means of Nd-Fe-B magnet under the working condition of the main drive motor, the easy demagnetization and non-easy demagnetization regions are identified by electromagnetic simulation, it is found that the easy demagnetization regions appear near the rotor air gap corner, and the demagnetization is not obvious near the middle region of the rotor and the magnetic steel, in order to further improve the utilization rate of heavy rare earth and reduce unnecessary waste of heavy rare earth, and to make the diffusion region more accurate and evaluate, for the easy demagnetization region, the same remanence high performance magnet and the same remanence low performance magnet in the non-easy demagnetization region are bonded to prepare the required combined magnet, so as to save the heavy rare earth in the non-easy demagnetization region. And according to the characteristics of the performance of each region, different heavy rare earth metal content is designed, so that the coercive force of each region reaches a matching relationship, so as to ensure the coercive force and remanence, and improve the anti-demagnetization performance.

[0009] The present application provides a kind of Nd-Fe-B magnet, the Nd-Fe-B magnet is cuboid, with the center of the upper surface of the cuboid as the origin to establish three-dimensional rectangular coordinate system, wherein, with orientation direction as Z axis positive direction, X axis is parallel to one side of the upper surface;

[0010] The Nd-Fe-B magnet includes non-easy demagnetization region, transition region and easy demagnetization region;The easy demagnetization region includes first easy demagnetization region, second easy demagnetization region, third easy demagnetization region and fourth easy demagnetization region respectively arranged in the four corners of the cuboid along the Z axis direction and do not contact each other;

[0011] The transition region is located at the junction of the easy demagnetization region and the non-easy demagnetization region, and includes first transition region, second transition region, third transition region and fourth transition region corresponding to the first easy demagnetization region, the second easy demagnetization region, the third easy demagnetization region and the fourth easy demagnetization region;

[0012] The content of heavy rare earth in the first easy demagnetization region, the second easy demagnetization region, the third easy demagnetization region and the fourth easy demagnetization region is the same;

[0013] The content of heavy rare earth in the first transition region, the second transition region, the third transition region and the fourth transition region is the same;

[0014] The content ratio of Tb in the non-easy demagnetization region and the first easy demagnetization region is (0-0.9) : 1;

[0015] The content ratio of Dy in the first easy demagnetization region and the non-easy demagnetization region is (0-0.9) : 1;

[0016] The content ratio of Tb in the first transition region and the first easy demagnetization region is (0.8-1) : 1.

[0017] In the present application, the heavy rare earth element can be derived from the substrate and / or the diffusion process.

[0018] In the present application, the content of heavy rare earth refers to the percentage of the mass of heavy rare earth in a certain region to the total mass of the magnet in the region, for example, the content of Tb in the first easy demagnetization region refers to the percentage of the mass of Tb in the first easy demagnetization region to the total mass of the magnet in the first easy demagnetization region.

[0019] In the present application, the diffusion weight gain of heavy rare earth refers to the percentage of the mass of heavy rare earth introduced by diffusion in a certain region to the total mass of the magnet in the region, for example, the diffusion weight gain of Tb in the first easy demagnetization region refers to the percentage of the mass of Tb introduced by diffusion in the first easy demagnetization region to the total mass of the magnet in the first easy demagnetization region.

[0020] In the present application, the "the diffusion weight gain of heavy rare earth is the same" refers to the type of heavy rare earth introduced by diffusion in each region is the same, and the diffusion weight gain of each type of heavy rare earth is the same.

[0021] In the present application, the specific position of the upper surface is not specifically limited, and those skilled in the art can generally understand that the upper surface refers to the surface opposite to the plane when the magnet is placed on the plane.

[0022] In the present application, the content ratio of Tb in the non-easy demagnetization region to the first easy demagnetization region can be (0-0.2):1, for example, 0.03:1, 0.05:1 or 0.02:1.

[0023] In the present application, the diffusion weight gain ratio of Tb in the non-easy demagnetization region to the first easy demagnetization region can be (0-0.05):(0.50-0.70), for example, 0.02:0.60, 0.03:0.60, 0.01:0.55, 0.01:0.50 or 0.01:0.60.

[0024] In the present application, the content ratio of Dy in the first easy demagnetization region to the non-easy demagnetization region can be (0-0.8):1, for example, 0:1, 0.02:1 or 0.04:1.

[0025] In the present application, the diffusion weight gain ratio of Dy in the first easy demagnetization region to the non-easy demagnetization region can be (0-0.05):(0.5-0.7), for example, 0:0.3, 0.01:0.5, 0.03:0.7 or 0:0.5.

[0026] In the present application, the content ratio of Tb in the first transition region to the first easy demagnetization region can be (0.9-1):1, for example, 0.97:1, 0.98:1 or 1:1.

[0027] In the present application, the diffusion weight gain ratio of Tb in the first transition region to the first easy demagnetization region can be (0.9-1):1, for example, 0.97:1, 0.98:1 or 1:1.

[0028] In the present application, the diffusion weight gain ratio of Dy in the first transition zone and the first easy demagnetization zone can be (0.05-0.6):(0-0.05), for example 0.1:0, 0.32:0.01, 0.1:0.03 or 0.1:0.01.

[0029] In the present application, the diffusion weight gain ratio of Dy in the first transition zone and the first easy demagnetization zone can be (0.05-0.6):(0-0.05), for example 0.1:0, 0.32:0.01, 0.1:0.03 or 0.1:0.01.

[0030] In the present application, the diffusion weight gain of Tb in the first easy demagnetization zone can be 0.1wt%-1wt%, for example 0.50wt%, 0.55wt% or 0.60wt%.

[0031] In the present application, the content of Tb in the first easy demagnetization zone can be 0.1wt%-2.5wt%, for example 0.50wt%, 0.55wt% or 0.60wt%.

[0032] In the present application, the diffusion weight gain of Dy in the first easy demagnetization zone can be 0.05wt% and below, for example 0, 0.01wt%, 0.02wt% or 0.03wt%.

[0033] In the present application, the content of Dy in the first easy demagnetization zone can be 0wt%-3.1wt%, for example 0, 0.01wt%, 0.02wt% or 0.03wt%.

[0034] In the present application, the diffusion weight gain of Tb in the first transition zone can be 0.1wt%-1wt%, preferably 0.3wt%-0.7wt%, for example 0.49wt%, 0.55wt%, 0.58wt% or 0.59wt%.

[0035] In the present application, the content of Tb in the first transition zone can be 0.1wt%-2.5wt%, for example 0.49wt%, 0.55wt%, 0.58wt% or 0.59wt%.

[0036] In the present application, the diffusion weight gain of Dy in the first transition zone can be 0.05wt%-0.9wt%, preferably 0.1wt%-0.5wt%, for example 0.1wt% or 0.32wt%.

[0037] In the present application, the content of Dy in the first transition zone can be 0.05wt%-3.9wt%, for example 0.1wt% or 0.32wt%.

[0038] In the present application, the diffusion weight gain of Tb in the non-easy demagnetization area can be 0.05wt% or less, for example, 0.01wt%, 0.02wt% or 0.03wt%.

[0039] In the present application, the content of Tb in the non-easy demagnetization area can be 0wt%-1.6wt%, for example, 0.01wt%, 0.02wt% or 0.03wt%.

[0040] In the present application, the diffusion weight gain of Dy in the non-easy demagnetization area can be 0.1wt%-1wt%, preferably 0.2wt%-0.7wt%, for example, 0.3wt%, 0.5wt% or 0.7wt%.

[0041] In the present application, the content of Dy in the non-easy demagnetization area can be 0.1wt%-4wt%, for example, 0.3wt%, 0.5wt% or 0.7wt%.

[0042] In some specific embodiments, the diffusion weight gain of Tb in the first easy demagnetization area is greater than the diffusion weight gain of Tb in the first transition area.

[0043] In some specific embodiments, the diffusion weight gain of Tb in the first transition area is higher than the diffusion weight gain of Tb in the non-easy demagnetization area.

[0044] In some specific embodiments, the diffusion weight gain of Dy in the first easy demagnetization area, the first transition area and the non-easy demagnetization area increases in turn.

[0045] In the present application, there is an interface A between the transition area and the easy demagnetization area, which includes first interface A, second interface A, third interface A and fourth interface A corresponding to the first transition area, the second transition area, the third transition area and the fourth transition area, and the diffusion weight gain of heavy rare earth in the first interface A, the second interface A, the third interface A and the fourth interface A is the same. In the present application, the first interface A refers to the interface between the first easy demagnetization area and the first transition area, the second interface A refers to the interface between the second easy demagnetization area and the second transition area, the third interface A refers to the interface between the third easy demagnetization area and the third transition area, and the fourth interface A refers to the interface between the fourth easy demagnetization area and the fourth transition area.

[0046] In the present application, the diffusion weight gain of Tb in the first interface A and the first easy demagnetization area is preferably (0.9-1):1, for example, 0.98:1 or 1:1.

[0047] In the present application, the content of Tb in the first interface A and the first easy demagnetization area is preferably (0.9-1):1, for example, 0.98:1 or 1:1.

[0048] The first interface A and the first easy demagnetization area have a better ratio of Dy diffusion weight gain of (0.02-0.2):(0-0.05), for example, 0.03:0, 0.1:0.01, 0.03:0.03, 0.02:0.03 or 0.03:0.01.

[0049] The first interface A and the first easy demagnetization area have a better ratio of Dy content of 1:(0.8-1), for example, 1:0.1 or 1:1.

[0050] In the present application, there is an interface B between the transition area and the non-easy demagnetization area, which includes a first interface B, a second interface B, a third interface B and a fourth interface B corresponding to the first transition area, the second transition area, the third transition area and the fourth transition area, and the first interface B, the second interface B, the third interface B and the fourth interface B have the same diffusion weight gain of heavy rare earth. In the present application, the first interface B refers to the interface between the first transition area and the non-easy demagnetization area, the second interface B refers to the interface between the second transition area and the non-easy demagnetization area, the third interface B refers to the interface between the third transition area and the non-easy demagnetization area, and the fourth interface B refers to the interface between the fourth transition area and the non-easy demagnetization area.

[0051] The first interface B and the non-easy demagnetization area have a better ratio of Tb diffusion weight gain of (0.5-0.9):(0-0.05), for example, 0.47:0.02, 0.48:0.03, 0.46:0.01, 0.4:0.01, 0.52:0.01 or 0.47:0.03.

[0052] The first interface B and the first easy demagnetization area have a better ratio of Tb content of (0.5-0.96):1.

[0053] The first interface B and the non-easy demagnetization area have a better ratio of Dy diffusion weight gain of (0.3-1):1, for example, 0.67:1, 0.86:1, 0.43:1, 0.44:1 or 0.50:1.

[0054] The first interface B and the first easy demagnetization area have a better ratio of Dy content of (0.5-1):1.

[0055] In the present application, the Nd-Fe-B magnet can be represented by the chemical formula R1-R2-T-B-M, wherein R1 comprises one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 is Dy and / or Tb; T comprises one or more of Zn, Si, V, Cr, Mn, Ni, Ge, Ti, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F and P; and M comprises one or more of Cu, Al, Co, Ga, Zr and Ti.

[0056] In some embodiments, the M element is entirely from the Nd-Fe-B base material.

[0057] In other embodiments, the M element comprises a diffusion-introduced M element, wherein the diffusion-introduced M element preferably accounts for 0%-0.4% of the mass percentage of the Nd-Fe-B magnet.

[0058] In the present application, in any plane perpendicular to the orientation direction, the shapes of the first, second, third and fourth easy demagnetization regions are each independently selected from a rectangle, a sector or a triangle. The shapes of the transition regions and the non-easy demagnetization region correspond to the shapes of the easy demagnetization regions.

[0059] When the first, second, third and fourth easy demagnetization regions are each a rectangle, the shapes of the first, second, third and fourth transition regions are each an L shape, and the shape of the non-easy demagnetization region is a cross shape.

[0060] In some preferred embodiments, the widths of the first, second, third and fourth easy demagnetization regions are the same, the width of an easy demagnetization region refers to the distance extending along the X or Y axis from the edge of the Nd-Fe-B magnet, and the width of the first easy demagnetization region is preferably (0.05-0.4):1 of the total width of the Nd-Fe-B magnet.

[0061] In the present application, the widths of the first, second, third and fourth transition regions are the same, the width of the first transition region refers to the distance between the interface between the first transition region and the first easy demagnetization region and the interface between the first transition region and the non-easy demagnetization region in the direction of the X or Y axis, and the width of the first transition region is preferably (0-0.1):1, for example 0.078:1, of the total width of the Nd-Fe-B magnet.

[0062] In the present application, the ratio of the width of the non-reversible demagnetization zone to the total width of the neodymium-iron-boron magnet is (0.2-1):1, for example 0.522:1, 0.7:1 or 1:1, wherein the width of the non-reversible demagnetization zone refers to the distance along the X-axis or Y-axis that the interface between the transition zone and the non-reversible demagnetization zone or the edge of the neodymium-iron-boron magnet extends.

[0063] In some embodiments, the width of the first transition zone is preferably 0-1 mm and is not 0.

[0064] In the present application, the ratio of the length to the thickness of the neodymium-iron-boron magnet is ≥3, preferably the thickness of the neodymium-iron-boron magnet is 0.5-5 mm; the length refers to the extension distance of one side of the upper surface in the positive direction of the X-axis; and the thickness refers to the extension distance of the cuboid from the upper surface in the positive direction of the Z-axis.

[0065] In the present application, the ratio of the coercivity of the non-reversible demagnetization zone to the first reversible demagnetization zone can be (0.7-0.96):1, more preferably (0.8-0.9):1, for example 0.85:1.

[0066] In the present application, the difference in coercivity between the first reversible demagnetization zone and the non-reversible demagnetization zone can be 0-10 kOe, more preferably 2-5 kOe, for example 2.5 kOe or 4 kOe.

[0067] In the present application, the ratio of the coercivity of the first transition zone to the first reversible demagnetization zone can be (0.95-1):1, more preferably (0.98-1):1, for example 0.99:1.

[0068] In the present application, the coercivity of the first reversible demagnetization zone, the second reversible demagnetization zone, the third reversible demagnetization zone and the fourth reversible demagnetization zone can be the same.

[0069] In the present application, the coercivity of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone can be the same.

[0070] In the present application, the coercivity of the first reversible demagnetization zone is not lower than the coercivity of the first transition zone, and the coercivity of the first transition zone is not lower than the coercivity of the non-reversible demagnetization zone.

[0071] In the present application, the remanence of the first reversible demagnetization zone, the second reversible demagnetization zone, the third reversible demagnetization zone and the fourth reversible demagnetization zone can be the same.

[0072] In the present application, the remanence of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone can be the same.

[0073] In the present application, the ratio of the remanence of the first reversible demagnetization zone to the non-reversible demagnetization zone can be (0.99-1):1.

[0074] In the present application, the remanence ratio of the first transition zone to the non-reversible magnetization zone can be (0.99-1):1.

[0075] In the present application, the grain boundary structure of the neodymium-iron-boron magnet comprises Re2Fe 14 B main phase grains and Re-rich phase grain boundaries; the Re2Fe 14 B main phase grains comprise a core layer and a shell layer; the Re is Dy and / or Tb.

[0076] Preferably, the thickness of the shell layer of the main phase grains of the first, second, third and fourth reversible magnetization zones is the same.

[0077] Preferably, the thickness of the shell layer of the main phase grains of the first, second, third and fourth transition zones is the same.

[0078] Preferably, the thickness of the Re-rich phase grain boundaries of the first, second, third and fourth reversible magnetization zones is the same.

[0079] Preferably, the thickness of the Re-rich phase grain boundaries of the first, second, third and fourth transition zones is the same.

[0080] Preferably, the thickness of the shell layer of the main phase grains in the first reversible magnetization zone, the first transition zone and the non-reversible magnetization zone is preferably 0-4 μm, more preferably 0-2 μm.

[0081] Preferably, the thickness of the Re-rich phase grain boundaries in the first reversible magnetization zone, the first transition zone and the non-reversible magnetization zone is preferably 0-1 μm, but not 0.

[0082] Preferably, the ratio of the thickness of the shell layer of the main phase grains to the thickness of the Re-rich phase grain boundaries in the first reversible magnetization zone, the first transition zone and the non-reversible magnetization zone is preferably (0-2.0):(0-1), but not 0.

[0083] Preferably, the particle size of the main phase grains of the first, second, third and fourth reversible magnetization zones is the same.

[0084] Preferably, the particle size of the main phase grains of the first, second, third and fourth transition zones is the same.

[0085] Preferably, the ratio of the particle size of the main phase grains of the first reversible magnetization zone, the first transition zone and the non-reversible magnetization zone is 1:1:1.

[0086] Preferably, the particle size of the surface main phase grains of the first reversible magnetization zone, the first transition zone and the non-reversible magnetization zone is the same, preferably 1-12 μm.

[0087] Preferably, the grain size of the surface layer of the main phase grains in the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone is 1-1.5 times the grain size of the central main phase grains.

[0088] Preferably, the core layer of the main phase grains and the shell layer of the main phase grains in the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone satisfy the following conditions: the content of R1 in the core layer is greater than or equal to the content of R1 in the shell layer; the content of R2 in the core layer is less than the content of R2 in the shell layer; wherein R1 includes one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; and R2 is Dy and / or Tb.

[0089] Preferably, the content of R2 in the shell layer of the main phase grains in the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone satisfies the following conditions:

[0090] When the R2 is Tb, the first easy demagnetization zone ≥ the first transition zone > the non-easy demagnetization zone.

[0091] When the R2 is Dy, the non-easy demagnetization zone ≥ the first transition zone > the first easy demagnetization zone.

[0092] The present application also provides a preparation method of the above-mentioned neodymium-iron-boron magnet, which comprises the following steps: applying a diffusion source Tb to a quadrilateral region and a diffusion source Dy to a non-quadrilateral region on the upper and lower surfaces of a neodymium-iron-boron substrate along the Z-axis direction, and performing grain boundary diffusion parallel to the orientation direction to obtain the neodymium-iron-boron magnet; wherein the quadrilateral region forms an easy demagnetization zone after grain boundary diffusion; and the non-quadrilateral region forms a non-easy demagnetization zone and a transition zone.

[0093] In the present application, the content of Tb in the neodymium-iron-boron substrate can be conventional in the art, and is preferably 0-1.5wt%.

[0094] In the present application, the content of Dy in the neodymium-iron-boron substrate can be conventional in the art, and is preferably 0-3wt%.

[0095] In the present application, it is known to those skilled in the art that the Dy or Tb in the diffusion source is not completely diffused into the magnet during grain boundary diffusion, and the utilization rate is generally 85%-95%, so that a larger amount of Dy or Tb is generally applied in the actual preparation process.

[0096] In some embodiments, the diffusion source is pure Dy.

[0097] In other embodiments, the diffusion source is a Dy-M alloy, and M includes one or more of Cu, Al, Co, Ga, Zr and Ti. The mass percentage of M in the Dy-M alloy is 0-40%, and is not 0.

[0098] In some embodiments, the diffusion source is pure Tb.

[0099] In some embodiments, the diffusion source is pure Tb.

[0100] In some embodiments, the diffusion source is a Tb-M alloy, M comprising one or more of Cu, Al, Co, Ga, Zr and Ti. Wherein, the mass percentage of M in the Tb-M is 0-40%, and is not 0.

[0101] In some embodiments, the diffusion source is pure Tb.

[0102] In some embodiments, the diffusion source is pure Tb.

[0103] In some embodiments, the diffusion source is a Tb-M alloy, M comprising one or more of Cu, Al, Co, Ga, Zr and Ti. Wherein, the mass percentage of M in the Tb-M is 0-40%, and is not 0.

[0104] In some embodiments, the diffusion source is pure Tb.

[0105] In the present application, the diffusion source can be applied in a manner known in the art, for example, by coating. It is known to those skilled in the art that different grain boundary diffusion methods will have different coating thicknesses when the same amount of Dy or Tb is diffused into the magnet, and therefore the coating thickness is not limited in the actual preparation process, as long as the corresponding amount of Dy or Tb diffusion is achieved.

[0106] Wherein, the coating method is preferably spraying or printing; the dewaxing temperature of the spraying is preferably 200-400℃; the dewaxing temperature of the printing is preferably 100-500℃.

[0107] When the diffusion source is applied by the coating method, the diffusion source, solvent and binder are generally mixed in a certain proportion to form a slurry.

[0108] Wherein, the solvent can be conventional in the art, for example, water, alcohol, ketone or ester.

[0109] In some preferable embodiments, the diffusion source is applied by coating, and the mass concentration of Dy in the diffusion source used in the non-remanence area is preferably 0.3%-1%; the mass concentration of Tb in the diffusion source used in the remanence area is preferably 0.3%-1.2%; the mass concentration of Tb in the diffusion source used in the first transition area is preferably 0.3%-1.2%; and the mass concentration of Dy in the diffusion source is preferably 0.3%-1%, and the percentage is the mass percentage of Dy or Tb in the diffusion source.

[0110] In the present application, the temperature of heat treatment in the grain boundary diffusion is 750-950℃, for example, 900℃.

[0111] In the present application, the time of heat treatment in the grain boundary diffusion is 5-30h, for example, 10h.

[0112] In the present application, the heat treatment in the grain boundary diffusion is generally followed by aging treatment.

[0113] In the present application, the temperature of aging treatment is preferably 300-600℃, for example, 500℃.

[0114] In the present application, the time of aging treatment is preferably 1-10h, for example, 3h.

[0115] In some preferable embodiments, the method for preparing the Nd-Fe-B magnet comprises the following steps: applying a Tb diffusion source on the upper surface of the remanence area, applying a Dy diffusion source on the upper surface of the non-remanence area, and performing grain boundary diffusion parallel to the orientation direction, thereby obtaining the Nd-Fe-B magnet.

[0116] In the above preferable embodiments, only a Tb diffusion source is applied on the surface of the remanence area during the diffusion process, and no Tb diffusion source is applied on the non-remanence area. However, after diffusion, a small amount of Tb applied on the remanence area may diffuse towards the center of the non-remanence area, and the Tb after diffusion is mainly distributed at the junction of the remanence area and the non-remanence area, and the Tb content in the center of the non-remanence area is low.

[0117] The present application also provides the use of the above Nd-Fe-B magnet in magnetic steel.

[0118] On the basis of common knowledge in the art, the above preferable conditions can be combined arbitrarily, thereby obtaining preferable examples of the present application.

[0119] The reagents and raw materials used in the present application are commercially available.

[0120] The positive progress effect of the present application is that:

[0121] The Nd-Fe-B magnet provided by the application comprises an easy demagnetization zone, a non-easy demagnetization zone and a transition zone, and the problem of poor anti-demagnetization effect caused by the gradient decrease of the performance of the junction zone is solved by controlling the diffusion weight gain ratio of Tb and Dy introduced by diffusion in the transition zone, the easy demagnetization zone and the non-easy demagnetization zone, so that the surface magnetic flux and the magnetic flux decay of the Nd-Fe-B magnet are reduced and the anti-demagnetization capacity of the Nd-Fe-B magnet is improved under the premise of ensuring the remanence of the Nd-Fe-B magnet. BRIEF DESCRIPTION OF DRAWINGS

[0122] Fig. 1 is a structural schematic diagram of each zone of the Nd-Fe-B magnet.

[0123] Fig. 2 is a structural schematic diagram of the main phase grain core and the shell layer in each zone of the Nd-Fe-B magnet.

[0124] Fig. 3 is a diffusion weight gain distribution schematic diagram of Tb of the Nd-Fe-B magnet of Example 1 along the test line 1 and the test line 2 shown in Fig. 1.

[0125] Fig. 4 is a diffusion weight gain distribution schematic diagram of Dy of the Nd-Fe-B magnet of Example 1 along the test line 1 and the test line 2 shown in Fig. 1.

[0126] Reference signs: 1-first easy demagnetization zone, 2-first transition zone, 3-non-easy demagnetization zone, 4-second transition zone, 5-second easy demagnetization zone, 6-third easy demagnetization zone, 7-third transition zone, 8-fourth transition zone, 9-fourth easy demagnetization zone, 10-main phase grain shell layer, 11-main phase grain core layer. DETAILED DESCRIPTION

[0127] The application will be further described by way of examples below, but the application is not limited in the scope of the examples. The experimental methods not specified in the following examples are selected according to the conventional methods and conditions, or according to the commercial instruction.

[0128] Examples 1-7 and Comparative Examples 1-5

[0129] Tb is sprayed on the four-corner region and Dy is sprayed on the non-four-corner region on the upper and lower surfaces of the Nd-Fe-B substrate along the Z-axis direction, the dewaxing temperature of the spraying is 300℃, and the grain boundary diffusion parallel to the orientation direction is performed, so as to obtain the Nd-Fe-B magnet; wherein the utilization rate of Dy or Tb is 85%-95%.

[0130] The temperature of the heat treatment in the grain boundary diffusion is 900℃, the time of the heat treatment is 10h, and the aging treatment is further included after the heat treatment, the temperature of the aging treatment is 500℃, and the time of the aging treatment is 3h.

[0131] The parameters of the Nd-Fe-B magnets of Examples 1-7 and Comparative Examples 1-5 are listed in Table 1-2 below, and the element contents of the Nd-Fe-B substrates used in Examples 1-7 and Comparative Examples 1-5 are shown in Table 3. Since the content of heavy rare earth metal in the substrate is 0, the diffusion weight gain of heavy rare earth in Examples 1-7 and Comparative Examples 1-5 is equal to its content.

[0132] The structural schematic diagram of the Nd-Fe-B magnets of Examples 1-7 and Comparative Examples 1-5 is shown in Figure 1, wherein the first easy demagnetization zone 1, the second easy demagnetization zone 5, the third easy demagnetization zone 6 and the fourth easy demagnetization zone 9 are all rectangular; the first transition zone 2, the second transition zone 4, the third transition zone 7 and the fourth transition zone 8 are all L-shaped, and the non-easy demagnetization zone 3 is cross-shaped; the thickness of the Nd-Fe-B magnet is 3 mm, and the ratio of length to thickness is 3. The direction of arrow M represents the magnetization direction of the Nd-Fe-B magnet, and the direction of arrow P represents the orientation direction of the Nd-Fe-B magnet; the A surface represents the surface layer of the Nd-Fe-B magnet, and the B surface represents the middle layer of the Nd-Fe-B magnet. The grain structure is shown in Figure 2, wherein 10 is the main phase grain shell layer, and 11 is the main phase grain core. Figure 3 is a schematic diagram of the diffusion weight gain distribution of Tb of the Nd-Fe-B magnet of Example 1 along the test line 1 and the test line 2 shown in Figure 1. Figure 4 is a schematic diagram of the diffusion weight gain distribution of Dy of the Nd-Fe-B magnet of Example 1 along the test line 1 and the test line 2 shown in Figure 1.

[0133] Table 1 Diffusion weight gain of Dy and Tb in each zone of Examples 1-7 and Comparative Examples 1-5

[0134] Table 1 (continued)

[0135] Table 2 Coercivity ratio and width ratio of transition zone to Nd-Fe-B magnet in each zone of Examples 1-7 and Comparative Examples 1-5

[0136] Table 3 Mass concentration (wt%) of each element in the substrate of Examples 1-7 and Comparative Examples 1-5

[0137] Effect Example 1

[0138] The following tests were performed on the Nd-Fe-B magnets of Examples 1-7 and Comparative Examples 1-5:

[0139] 1. Coercivity and remanence test: The samples of Examples 1-7 and Comparative Examples 1-5 were prepared, and the sample size was W2-3±0.1*L15±0.1*T5.6±0.1 mm. Single piece test was performed, and a size W3*L15-16*T2.7 mm coil was used to test the samples in a permanent magnet precision measurement system NIM-62000 at room temperature (temperature ≤200℃).

[0140] 2. Test of demagnetization rate: using electromagnetic simulation software, model Ansys Workbench, inputting rotation speed 1300 rpm, then adjusting the temperature to the corresponding temperature working condition, collecting back electromotive force data of the motor and observing the magnetic steel cloud map change under the same time, identifying whether demagnetization of the magnetic steel occurs. The calculation formula of demagnetization rate: demagnetization rate = (high-temperature back electromotive force - normal-temperature back electromotive force) / normal-temperature back electromotive force.

[0141] The technical effects of Examples 1-7 and Comparative Examples 1-5 are listed in Table 4 below:

[0142] Table 4 Coercivity and demagnetization resistance of each zone in the magnet of Examples 1-7 and Comparative Examples 1-5 Note: ① The meaning of "easy demagnetization zone" in Tables 1, 2 and 4 is the first, second, third or fourth easy demagnetization zone; ② The meaning of "transition zone" in the table is the first, second, third or fourth transition zone.

[0143] From the above table, the remanence of the easy demagnetization zone, transition zone and non-easy demagnetization zone of the Nd-Fe-B magnets prepared in Examples 1-7 are all maintained above 14.30 kGs, and at the same time have excellent demagnetization resistance, the demagnetization rate of the Nd-Fe-B magnets of Examples 1-7 at 130℃ is only 2.5%-9.1%.

[0144] The Tb diffusion weight gain ratio of the first transition zone to the first easy demagnetization zone of Comparative Example 1 is too low, specifically 0.17:1, and the demagnetization resistance of the Nd-Fe-B magnet prepared in Comparative Example 1 is poor, and its demagnetization rate at 130℃ is 10.5%, higher than that of Examples 1-7, and the demagnetization resistance is poor.

[0145] The Tb diffusion weight gain ratio of the first transition zone to the first easy demagnetization zone of Comparative Example 2 is too low, specifically 0.6:1, and the Dy diffusion weight gain of the transition zone and the non-easy demagnetization zone is 0, and the demagnetization resistance of the Nd-Fe-B magnet prepared in Comparative Example 2 is poor, and its demagnetization rate at 130℃ is as high as 39.2%, much higher than that of Examples 1-7.

[0146] The Tb diffusion weight gain ratio of the first transition zone to the first easy demagnetization zone of Comparative Example 3 is within the scope of the application, but the diffusion weight gain of Dy in the transition zone and the non-easy demagnetization zone is 0, and its demagnetization resistance at 130℃ is as high as 36.5%, and the demagnetization resistance is poor.

[0147] The Tb diffusion weight gain ratio of the non-easy demagnetization zone to the easy demagnetization zone in Comparative Example 4 is not within the scope of the application, specifically 1:1; its demagnetization resistance at 130℃ is as high as 24.2%, and the demagnetization resistance is poor.

[0148] In the comparative example 5, no transition zone is provided, and the diffusion weight ratio of Dy in the first easy demagnetization zone to the non-easy demagnetization zone is 0.1:0.5. The diffusion weight of Dy in the easy demagnetization zone is too high, and the anti-demagnetization rate of the Nd-Fe-B magnet prepared is as high as 13.2% at 130°C, and the anti-demagnetization performance is poor.

[0149] The above-described embodiments are only the preferred embodiments of the present application, and are convenient for those skilled in the art to understand and use the present application. Obviously, any modification or change of the present embodiments made by those skilled in the art without creative labor should be within the scope of the present application. Therefore, the present application is not limited to the above-described embodiments, and any equivalent change, simple modification and modification within the scope of the present application should be within the scope of the present application.

Claims

1. A neodymium-iron-boron magnet, characterized in that The neodymium-iron-boron magnet is a cuboid, and a three-dimensional rectangular coordinate system is established with the center of the upper surface of the cuboid as the origin, wherein the orientation direction is the positive direction of the Z axis, and the X axis is parallel to one side of the upper surface; The neodymium-iron-boron magnet comprises a non-easy demagnetization area, a transition area and an easy demagnetization area; the easy demagnetization area comprises a first easy demagnetization area, a second easy demagnetization area, a third easy demagnetization area and a fourth easy demagnetization area respectively arranged at four corners of the cuboid along the Z axis direction and not in contact with each other; The transition area is located at the junction of the easy demagnetization area and the non-easy demagnetization area, and comprises a first transition area, a second transition area, a third transition area and a fourth transition area corresponding to the first easy demagnetization area, the second easy demagnetization area, the third easy demagnetization area and the fourth easy demagnetization area respectively; The content of heavy rare earth in the first easy demagnetization area, the second easy demagnetization area, the third easy demagnetization area and the fourth easy demagnetization area is the same; The content of heavy rare earth in the first transition area, the second transition area, the third transition area and the fourth transition area is the same; The content ratio of Tb in the non-easy demagnetization area to the first easy demagnetization area is (0-0.9):1; The content ratio of Dy in the first easy demagnetization area to the non-easy demagnetization area is (0-0.9):1; The content ratio of Tb in the first transition area to the first easy demagnetization area is (0.8-1):

1.

2. The neodymium-iron-boron magnet according to claim 1, characterized in that The content ratio of Tb in the non-easy demagnetization area to the first easy demagnetization area is (0-0.2):1, for example 0.03:1, 0.05:1 or 0.02:1; And / or, the diffusion weight gain ratio of Tb in the non-easy demagnetization area to the first easy demagnetization area is (0-0.05):(0.3-1), preferably (0-0.05):(0.50-0.70), for example 0.02:0.60, 0.03:0.60, 0.01:0.55, 0.01:0.50 or 0.01:0.60; And / or, the content ratio of Dy in the first easy demagnetization area to the non-easy demagnetization area is (0-0.8):1, for example 0:1, 0.02:1 or 0.04:1; And / or, the diffusion weight gain ratio of Dy in the first easy demagnetization area to the non-easy demagnetization area is (0-0.05):(0.3-1), preferably (0-0.05):(0.5-0.7), for example 0:0.3, 0.01:0.5, 0.03:0.7 or 0:0.5; And / or, the content ratio of Tb in the first transition area to the first easy demagnetization area is (0.9-1):1, for example 0.97:1, 0.98:1 or 1:1; And / or, the diffusion weight gain ratio of Tb in the first transition area to the first easy demagnetization area is (0.8-1):1, preferably (0.9-1):1, for example 0.97:1, 0.98:1 or 1:1; And / or, the diffusion weight gain ratio of Dy in the first transition area to the first easy demagnetization area is (0.05-0.6):(0-0.05), for example 0.1:0, 0.32:0.01, 0.1:0.03 or 0.1:0.

01. and / or the first transition zone has a ratio of diffusion weight gain of Dy to the non-finely reversible zone of (0.05-0.9): 1, preferably (0.14-0.90): 1, such as 0.33:1, 0.14:1 or 0.20:1; and / or the first finely reversible zone has a diffusion weight gain of Tb of 0.1wt% - 1wt%, such as 0.50wt%, 0.55wt% or 0.60wt%; and / or the first finely reversible zone has a content of Tb of 0.1wt% - 2.5wt%, such as 0.50wt%, 0.55wt% or 0.60wt%; and / or the first finely reversible zone has a diffusion weight gain of Dy of 0.05wt% and below, such as 0, 0.01wt%, 0.02wt% or 0.03wt%; and / or the first finely reversible zone has a content of Dy of 0wt% - 3.1wt%, such as 0, 0.01wt%, 0.02wt% or 0.03wt%; and / or the first transition zone has a diffusion weight gain of Tb of 0.1wt% - 1wt%, preferably 0.3wt% - 0.7wt%, such as 0.49wt%, 0.55wt%, 0.58wt% or 0.59wt%; and / or the first transition zone has a content of Tb of 0.1wt% - 2.5wt%, such as 0.49wt%, 0.55wt%, 0.58wt% or 0.59wt%; and / or the first transition zone has a diffusion weight gain of Dy of 0.05wt% - 0.9wt%, preferably 0.1wt% - 0.5wt%, such as 0.1wt% or 0.32wt%; and / or the first transition zone has a content of Dy of 0.05wt% - 3.9wt%, such as 0.1wt% or 0.32wt%; and / or the non-finely reversible zone has a diffusion weight gain of Tb of 0.05wt% and below, such as 0.01wt%, 0.02wt% or 0.03wt%; and / or the non-finely reversible zone has a content of Tb of 0wt% - 1.6wt%, such as 0.01wt%, 0.02wt% or 0.03wt%; and / or the non-finely reversible zone has a diffusion weight gain of Dy of 0.1wt% - 1wt%, preferably 0.2wt% - 0.7wt%, such as 0.3wt%, 0.5wt% or 0.7wt%; and / or the non-finely reversible zone has a content of Dy of 0.1wt% - 4wt%, such as 0.3wt%, 0.5wt% or 0.7wt%; and / or the first finely reversible zone has a higher diffusion weight gain of Tb than the first transition zone; and / or the first transition zone has a higher diffusion weight gain of Tb than the non-finely reversible zone; and / or the first finely reversible zone, the first transition zone and the non-finely reversible zone have diffusion weight gains of Dy that increase in order.

3. The neodymium-iron-boron magnet of claim 1, wherein, There is an interface A between the transition zone and the easy demagnetization zone, the interface A includes first interface A, second interface A, third interface A and fourth interface A corresponding to the first transition zone, the second transition zone, the third transition zone and the fourth transition zone, the diffusion weight of heavy rare earth of the first interface A, the second interface A, the third interface A and the fourth interface A is the same; Wherein, the Tb diffusion weight of the first interface A compared to the first easy demagnetization zone is preferably (0.9-1):1, such as 0.98:1 or 1:1; Wherein, the Tb content of the first interface A compared to the first easy demagnetization zone is preferably (0.9-1):1, such as 0.98:1 or 1:1; Wherein, the Dy diffusion weight of the first interface A compared to the first easy demagnetization zone is preferably (0.02-0.2):(0-0.05), such as 0.03:0, 0.1:0.01, 0.03:0.03, 0.02:0.03 or 0.03:0.01; Wherein, the Dy content of the first interface A compared to the first easy demagnetization zone is preferably 1:(0.8-1), such as 1:0.1 or 1:1; And / or, there is an interface B between the transition zone and the non-easy demagnetization zone, the interface B includes first interface B, second interface B, third interface B and fourth interface B corresponding to the first transition zone, the second transition zone, the third transition zone and the fourth transition zone, the diffusion weight of heavy rare earth of the first interface B, the second interface B, the third interface B and the fourth interface B is the same; Wherein, the Tb diffusion weight of the first interface B compared to the non-easy demagnetization zone is preferably (0.5-0.9):(0-0.05), such as 0.47:0.02, 0.48:0.03, 0.46:0.01, 0.4:0.01, 0.52:0.01 or 0.47:0.03; Wherein, the Tb content of the first interface B compared to the first easy demagnetization zone is preferably (0.5-0.96):1; Wherein, the Dy diffusion weight of the first interface B compared to the non-easy demagnetization zone is preferably (0.3-1):1, such as 0.67:1, 0.86:1, 0.43:1, 0.44:1 or 0.50:

1. Wherein, the Dy content of the first interface B compared to the first easy demagnetization zone is preferably (0.5-1):1; 4. The neodymium-iron-boron magnet of claim 1, wherein, In any plane perpendicular to the orientation direction, the shape of the first easy demagnetization zone, the second easy demagnetization zone, the third easy demagnetization zone and the fourth easy demagnetization zone is independently selected from a rectangle, a sector or a triangle; Preferably, the first, second, third and fourth easy demagnetization regions are rectangular and have the same width; the width of an easy demagnetization region refers to the distance extending along the X-axis or Y-axis from the edge of the Nd-Fe-B magnet; the first, second, third and fourth transition regions have the same width; the width of the first transition region refers to the distance between the interface between the first transition region and the first easy demagnetization region and the interface between the first transition region and the non-easy demagnetization region along the X-axis or Y-axis direction; Preferably, the ratio of the width of the first easy demagnetization region to the total width of the Nd-Fe-B magnet is (0.05-0.4):1, for example 0.20:1; Preferably, the ratio of the width of the non-easy demagnetization region to the total width of the Nd-Fe-B magnet is (0.2-1):1, for example 0.522:1, 0.7:1 or 1:1; the width of the non-easy demagnetization region refers to the distance extending along the X-axis or Y-axis from the interface between the transition region and the non-easy demagnetization region or the edge of the Nd-Fe-B magnet; Preferably, the ratio of the width of the first transition region to the total width of the Nd-Fe-B magnet is (0-0.1):1, for example 0.078:1; Preferably, the width of the first transition region is 0-1mm and is not 0; Preferably, the ratio of the length to the thickness of the Nd-Fe-B magnet is ≥3, and preferably the thickness of the Nd-Fe-B magnet is 0.5-5mm; the length refers to the distance extending along the positive direction of the X-axis of one side of the upper surface; the thickness refers to the distance extending along the positive direction of the Z-axis of the cuboid from the upper surface.

5. The neodymium-iron-boron magnet of claim 1, wherein, The coercivities of the first, second, third and fourth easy demagnetization regions are the same; the coercivities of the first, second, third and fourth transition regions are the same; Preferably, the ratio of the coercivity of the non-easy demagnetization region to the coercivity of the first easy demagnetization region is (0.7-0.96):1, for example 0.79:1, 0.85:1, 0.89:1, 0.92:1, 0.92:1 or 0.94:1; Preferably, the difference between the coercivity of the first easy demagnetization region and the coercivity of the non-easy demagnetization region is 0-10kOe, more preferably 1-5kOe, for example 1.5kOe, 2.1kOe, 2.6kOe, 2.8kOe, 4kOe or 5.5kOe; Preferably, the ratio of the coercivity of the first transition region to the coercivity of the first easy demagnetization region is (0.95-1):1, more preferably (0.98-1):1, for example 0.99:1 or 0.98:1; Preferably, the coercivity of the first easy demagnetization region is not lower than the coercivity of the first transition region, and the coercivity of the first transition region is not lower than the coercivity of the non-easy demagnetization region; Preferably, the remanences of the first, second, third and fourth easy demagnetization regions are the same; the remanences of the first, second, third and fourth transition regions are the same; Preferably, the ratio of the remanence of the first easy demagnetization region to the remanence of the non-easy demagnetization region is (0.99-1):1, for example 1:

1. Preferably, the ratio of remanence of the first transition zone to the non-remanence zone is (0.99-1):1, for example 1:

1.

6. The neodymium-iron-boron magnet of claim 1, wherein, The grain boundary structure of the neodymium-iron-boron magnet comprises Re2Fe 14 B main phase grains and Re-rich phase grain boundaries; the Re2Fe 14 The B main phase grains comprise a main phase grain shell layer; the Re is Dy and / or Tb; The thickness of the main phase grain shell layer of the first remanence zone, the second remanence zone, the third remanence zone and the fourth remanence zone is the same; the thickness of the main phase grain shell layer of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone is the same. The thickness of the Re-rich phase grain boundary of the first remanence zone, the second remanence zone, the third remanence zone and the fourth remanence zone is the same; the thickness of the Re-rich phase grain boundary of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone is the same. The thickness of the main phase grain shell layer in the first remanence zone, the first transition zone and the non-remanence zone is preferably 0-4 μm, more preferably 0-2 μm. The thickness of the Re-rich phase grain boundary in the first remanence zone, the first transition zone and the non-remanence zone is preferably 0-1 μm, but not 0. The ratio of the thickness of the main phase grain shell layer to the thickness of the Re-rich phase grain boundary in the first remanence zone, the first transition zone and the non-remanence zone is preferably (0-2.0):(0-1), but not 0.

7. The neodymium-iron-boron magnet of claim 6, wherein, The particle size of the main phase grain of the first remanence zone, the second remanence zone, the third remanence zone and the fourth remanence zone is the same; The particle size of the main phase grain of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone is the same; The ratio of the particle size of the main phase grain of the first remanence zone, the first transition zone and the non-remanence zone is 1:1:1; The surface layer main phase grain of the first remanence zone, the first transition zone and the non-remanence zone has the same particle size, preferably 1-12 μm; The surface layer main phase grain of the first remanence zone, the first transition zone and the non-remanence zone has a particle size of 1-1.5 times that of the center main phase grain; The core layer of the main phase grain and the shell layer of the main phase grain in the first remanence zone, the first transition zone and the non-remanence zone satisfy the following conditions: the R1 content in the core layer is greater than or equal to the R1 content in the shell layer; the R2 content in the core layer is less than the R2 content in the shell layer; wherein R1 includes one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 is Dy and / or Tb; The R2 content in the shell layer of the main phase grain of the first remanence zone, the first transition zone and the non-remanence zone satisfies the following conditions: When the R2 is Tb, the first remanence zone≥the first transition zone>the non-remanence zone; When the R2 is Dy, the non-remanence zone≥the first transition zone>the first remanence zone.

8. A method of producing a neodymium-iron-boron magnet as claimed in any one of claims 1 to 7, characterized in that It comprises the following steps: applying diffusion source Tb in the four-corner region and applying diffusion source Dy in the non-four-corner region on the upper and lower surfaces of the neodymium iron boron substrate along the Z-axis direction, and performing grain boundary diffusion parallel to the orientation direction, thereby obtaining the neodymium iron boron magnet; wherein the four-corner region forms a remanence zone after grain boundary diffusion; the non-four-corner region forms a non-remanence zone and a transition zone.

9. The method of producing a neodymium-iron-boron magnet according to claim 8, characterized by, The diffusion source is applied by coating; Preferably, the coating is spraying or printing; the spraying is preferably at a temperature of 200-400°C; the printing is preferably at a temperature of 100-500°C; Preferably, the heat treatment in the grain boundary diffusion is at a temperature of 750-950°C, for example 900°C; Preferably, the heat treatment in the grain boundary diffusion is for a time of 5-30h, for example 10h; Preferably, the heat treatment in the grain boundary diffusion is followed by an aging treatment; Preferably, the aging treatment is at a temperature of 300-600°C, for example 500°C; Preferably, the aging treatment is for a time of 1-10h, for example 3h; Preferably, the Nd-Fe-B substrate contains 0-1.5wt% Tb; Preferably, the Nd-Fe-B substrate contains 0-3wt% Dy.

10. Use of a Nd-Fe-B magnet according to any one of claims 1-7 as a magnetic steel.

Images