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

Abstract

Disclosed in the present invention are a neodymium-iron-boron magnet, and a preparation method therefor and the use thereof. The neodymium-iron-boron magnet comprises an invulnerable-to-demagnetization region, a transition region and a vulnerable-to-demagnetization region, wherein the ratio of the content of Tb in the transition region to the content of Tb in the vulnerable-to-demagnetization region is (0.7-1):1; the ratio of the content of Tb in the transition region to the content of Tb in the invulnerable-to-demagnetization region is 1:(0-0.9); the ratio of the content of Dy in the transition region to the content of Dy in the vulnerable-to-demagnetization region is (0-1):(0-0.9); and the ratio of the content of Dy in the transition region to the content of Dy in the invulnerable-to-demagnetization region is (0-0.98):1. The neodymium-iron-boron magnet has a good anti-demagnetization capability.

Description

Neodymium-iron-boron magnet, preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to a neodymium-iron-boron magnet, a preparation method and application 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 appliances, industrial robots, 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 higher coercivity and thermal stability. In order to improve the temperature resistance of 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 resources of heavy rare earth are scarce and the price is high, which seriously restricts the application of neodymium-iron-boron magnet in various industries.

[0003] With the increasing demand for high-performance magnets, 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 without changing the remanence. In terms of effective utilization 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 provides a neodymium-iron-boron magnet, a preparation method and application thereof, which has excellent anti-demagnetization ability.

[0006] The present application mainly solves the above technical problems through the following technical solutions.

[0007] The present application provides a neodymium-iron-boron magnet, a preparation method and application thereof, which has excellent anti-demagnetization ability.

[0008] The Nd-Fe-B magnet comprises a non-remanence-easy region, a transition region and a remanence-easy region; the remanence-easy region is an annular region on the upper surface of the Nd-Fe-B magnet along the Z-axis direction; the non-remanence-easy region is a central region on the upper surface of the Nd-Fe-B magnet along the Z-axis direction; and the transition region is a boundary region between the remanence-easy region and the non-remanence-easy region.

[0009] The content ratio of Tb in the transition region to the remanence-easy region is (0.7-1):1.

[0010] The content ratio of Tb in the transition region to the non-remanence-easy region is 1:(0-0.9).

[0011] The content ratio of Dy in the transition region to the remanence-easy region is (0-1):(0-0.9).

[0012] The content ratio of Dy in the transition region to the non-remanence-easy region is (0-0.98):1.

[0013] In the present application, the heavy rare earth element can be derived from the substrate and / or the diffusion process, and preferably from the diffusion process. The percentage of the mass of the heavy rare earth element introduced into a certain region to the total mass of the magnet in the region is referred to as the diffusion weight gain of the heavy rare earth element.

[0014] In the present application, the content of the heavy rare earth element refers to the percentage of the mass of the heavy rare earth element in a certain region to the total mass of the magnet in the region, for example, the content of Tb in the first remanence-easy region means the percentage of the mass of Tb in the first remanence-easy region to the total mass of the magnet in the first remanence-easy region.

[0015] 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.

[0016] In the present application, preferably, the content ratio of Tb in the transition region to the remanence-easy region is 0.71:1, 0.8:1 or 0.83:1.

[0017] In the present application, preferably, the diffusion weight gain ratio of Tb in the transition region to the remanence-easy region is (0.7-1):1, more preferably 0.71:1, 0.8:1 or 0.83:1.

[0018] In the present application, preferably, the content ratio of Tb in the transition region to the non-remanence-easy region is 1:(0-0.2), more preferably 1:(0-0.05), for example, 1:0.02 or 1:0.05.

[0019] In the present invention, preferably, the ratio of the diffusion weight gain of Tb in the transition zone to that in the non-soft magnetic zone is 1:(0-0.2), more preferably 1:(0-0.05), for example 1:0.02 or 1:0.05.

[0020] In the present invention, preferably, the ratio of the content of Dy in the transition zone to that in the soft magnetic zone is (0.05-0.9):(0-0.05), more preferably 1:(0-0.9), further more preferably 1:(0-0.8), for example 8:1, 37:5 or 23:5.

[0021] In the present invention, preferably, the ratio of the diffusion weight gain of Dy in the transition zone to that in the soft magnetic zone is (0.05-0.9):(0-0.05), more preferably 1:(0-0.9), further more preferably 1:(0-0.8), for example 8:1, 37:5 or 23:5.

[0022] In the present invention, preferably, the ratio of the content of Dy in the transition zone to that in the non-soft magnetic zone is (0.05-0.9):1, more preferably 0.57:1, 0.58:1 or 0.67:1.

[0023] In the present invention, preferably, the ratio of the diffusion weight gain of Dy in the transition zone to that in the non-soft magnetic zone is (0.05-0.9):1, more preferably 0.57:1, 0.58:1 or 0.67:1.

[0024] In the present invention, preferably, the ratio of the content of Tb in the non-soft magnetic zone to that in the soft magnetic zone is (0-0.05):1, more preferably (0-0.03):1, for example 0.01:1 or 0.02:1.

[0025] In the present invention, preferably, the ratio of the diffusion weight gain of Tb in the non-soft magnetic zone to that in the soft magnetic zone is (0-0.05):1, more preferably (0-0.03):1, for example 0.01:1 or 0.02:1.

[0026] In the present invention, preferably, the ratio of the content of Dy in the soft magnetic zone to that in the non-soft magnetic zone is (0-0.05):(0.3-1), and not 0, more preferably (0-0.03):(0.3-0.7), and not 0, for example 0.07:1, 0.09:1 or 0.13:1.

[0027] In the present invention, preferably, the ratio of the diffusion weight gain of Dy in the soft magnetic zone to that in the non-soft magnetic zone is (0-0.05):(0.3-1), and not 0, more preferably (0-0.03):(0.3-0.7), and not 0, for example 0.07:1, 0.09:1 or 0.13:1.

[0028] In the present application, preferably, the content of Tb in the easy demagnetization zone is 0.1wt%-2.5wt%, for example, 0.4wt%, 0.55wt% or 0.7wt%.

[0029] In the present application, preferably, the content of Tb in the non-easy demagnetization zone is 0-1.6wt%, for example, 0.015wt% or 0.01wt%.

[0030] In the present application, preferably, the content of Tb in the transition zone is 0.1wt%-2.5wt%, for example, 0.33wt%, 0.4wt% or 0.5wt%.

[0031] In the present application, preferably, the content of Dy in the easy demagnetization zone is 0-3.1wt%, for example, 0.05wt%.

[0032] In the present application, preferably, the content of Dy in the non-easy demagnetization zone is 0.1wt%-4wt%, more preferably 0.4wt%-0.7wt%, for example, 0.5wt% or 0.55wt%.

[0033] In the present application, preferably, the content of Dy in the transition zone is 0.05wt%-3.9wt%, more preferably 0.05wt%-0.4wt%, for example, 0.23wt% or 0.37wt%.

[0034] In the present application, preferably, the volume percentage of the easy demagnetization zone in the volume of the Nd-Fe-B magnet is 20%-80%, more preferably 29%-70%, for example, 54.6% or 42.48%.

[0035] In the present application, preferably, the diffusion weight gain of Tb at any two points in the non-easy demagnetization zone is equal.

[0036] In the present application, preferably, the diffusion weight gain of Dy at any two points in the non-easy demagnetization zone is equal.

[0037] In the present application, preferably, the content of Tb at any two points in the easy demagnetization zone is equal.

[0038] In the present application, preferably, the content of Dy at any two points in the non-easy demagnetization zone is equal.

[0039] In the present application, preferably, the volume percentage of the transition zone in the volume of the Nd-Fe-B magnet is 5%-15%, more preferably 10%-14%, further more preferably 10.6%-13.65%.

[0040] In the present application, the volume percentage of the non-remanence easy magnetization area in the volume of the Nd-Fe-B magnet is preferably 20%-75%, more preferably 24.18%-70.66%, and further more preferably 34.27%-57.5%.

[0041] In the present application, the coercivity of the non-remanence easy magnetization area and the remanence easy magnetization area is preferably 1:(0.7-0.96), more preferably 1:(0.8-0.9), for example 1:0.85.

[0042] In some embodiments, the shape of the non-remanence easy magnetization area in any plane perpendicular to the orientation direction is rectangular.

[0043] In some embodiments, the shape of the non-remanence easy magnetization area in any plane perpendicular to the orientation direction is rectangular.

[0044] In some embodiments, the Nd-Fe-B magnet is a cuboid.

[0045] In the present application, the ratio of the length to the thickness of the Nd-Fe-B magnet is preferably (3-25):1, more preferably (3.64-24.27):1, and further more preferably (8.74-24.27):1, for example 12.85:1; the length refers to the extension distance of one side of the upper surface along the positive direction of the X axis; and the thickness refers to the extension distance of the cuboid from the upper surface along the positive direction of the Z axis.

[0046] In the present application, the width of the non-remanence easy magnetization area is preferably 0-5mm and not 0, more preferably 2-4mm; the width refers to the length covered by the non-remanence easy magnetization area along the direction perpendicular to the periphery of the origin.

[0047] In the present application, there is an interface A between the transition area and the corresponding non-remanence easy magnetization area, and the interface A is annular.

[0048] In the present application, the content of Tb in the interface A is preferably 0.1wt%-2.5wt%, for example 0.35wt%, 0.4wt%, 0.5wt% or 0.55wt%.

[0049] In the present application, the diffusion weight gain of Tb in the interface A is preferably 0.1wt%-2.5wt%, for example 0.35wt%, 0.4wt%, 0.5wt% or 0.55wt%.

[0050] In the present application, the content ratio of Tb in the interface A and the non-remanence easy magnetization area is preferably (0.9-1):1.

[0051] In the present application, the diffusion weight gain ratio of Tb in the interface A and the non-remanence easy magnetization area is preferably (0.9-1):1.

[0052] The content of Dy in the interface A is preferably 0.01wt%-3.5wt%, for example 0.05wt%.

[0053] The diffusion weight gain of Dy in the interface A is preferably 0.01wt%-3.5wt%, for example 0.05wt%.

[0054] The content ratio of Dy in the interface A and the easy demagnetization area is preferably (0.02-0.2):(0-0.05), more preferably 1:(0.8-1), for example 1:1.

[0055] The diffusion weight gain ratio of Dy in the interface A and the easy demagnetization area is preferably (0.02-0.2):(0-0.05), more preferably 1:(0.8-1), for example 1:1.

[0056] In the present application, there is an interface B between the transition area and the corresponding non-easy demagnetization area, and the interface B is annular.

[0057] The content of Tb in the interface B is preferably 0.05wt%-2.4wt%, for example 0.22wt% or 0.23wt%.

[0058] The diffusion weight gain of Tb in the interface B is preferably 0.05wt%-2.4wt%, for example 0.22wt% or 0.23wt%.

[0059] The content ratio of Tb in the interface B and the non-easy demagnetization area is preferably 1:(0-0.94), more preferably 1:(0-0.05), for example 1:0.04 or 1:0.045.

[0060] The content ratio of Tb in the interface B and the non-easy demagnetization area is preferably 1:(0-0.94), more preferably 1:(0-0.2), further more preferably 1:(0-0.05), for example 1:0.04 or 1:0.045.

[0061] The diffusion weight gain ratio of Tb in the interface B and the non-easy demagnetization area is preferably 1:(0-0.94), more preferably 1:(0-0.2), further more preferably 1:(0-0.05), for example 1:0.04 or 1:0.045.

[0062] The content of Dy in the interface B is preferably 0.08wt%-4wt%, for example 0.37wt% or 0.23wt%.

[0063] The Dy diffusion weight gain of the interface B is preferably 0.05wt% to 1wt%, for example 0.37wt%.

[0064] The Dy content of the interface B to the non-soft magnetic region is preferably (0.5-1) : 1, for example 0.57:1, 0.67:1 or 0.58:1.

[0065] The Dy diffusion weight gain ratio of the interface B to the non-soft magnetic region is preferably (0.1-0.7) : 1, for example 0.13:1, 0.14:1, 0.22:1 or 0.4:1.

[0066] 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.

[0067] In some embodiments, the M element is entirely from the Nd-Fe-B base material.

[0068] In other embodiments, the M element comprises a diffusion-introduced M element, wherein the diffusion-introduced M element preferably accounts for 0% to 0.4% of the mass percentage of the Nd-Fe-B magnet.

[0069] In some preferred embodiments of the present application, the grain boundary structure of the Nd-Fe-B magnet comprises Re2Fe 14 B main phase grains and Re-rich grain boundaries; the Re2Fe 14 B main phase grains comprise a core layer and a shell layer; the Re is Dy and / or Tb. The Re2Fe 14 The shell layer of the Re2Fe 14 B hard magnetic layer; the Re-rich grain boundary has the meaning of a conventional meaning in the art, i.e. a two-particle grain boundary region with Re>95%.

[0070] In some specific embodiments of the present application, the Re2Fe 14 B main phase grains comprises a core layer and a shell layer; the Re is Dy and / or Tb. The Re2Fe 14 B hard magnetic layer.

[0071] In some specific embodiments of the present application, the Re2Fe 14The shell of the B main phase crystal grain comprises (Nd, Dy)2Fe 14 The B hard magnetic layer.

[0072] In some embodiments of the present application, the Re2Fe 14 The difference of the size of the B main phase crystal grain is not more than 1-8 μm.

[0073] In some embodiments of the present application, the Re2Fe 14 The difference of the size of the B main phase crystal grain is not more than 1-8 μm.

[0074] In some embodiments of the present application, the Re2Fe 14 The size of the B main phase crystal grain is equal, wherein the surface means the surface perpendicular to the orientation direction.

[0075] In some embodiments of the present application, the Re2Fe 14 The size of the B main phase crystal grain is equal, wherein the center means the median plane along the orientation direction.

[0076] In the present application, the size of the crystal grain means the average value of the size of all the crystal grains in a certain region. For example, the size of the main phase crystal grain in the easy demagnetization region means the average value of the size of all the crystal grains in the easy demagnetization region.

[0077] In some preferred embodiments of the present application, the Re2Fe 14 The core of the B main phase crystal grain and the Re2Fe 14 The shell of the B main phase crystal grain satisfies the following conditions: the content of R1 in the core is greater than or equal to the content of R1 in the shell; the content of R2 in the core is less than the content of R2 in the shell; wherein R1 comprises one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; and R2 is Dy and / or Tb.

[0078] In some embodiments of the present application, in the easy demagnetization region, the Re2Fe 14 The thickness of the shell of the B main phase crystal grain is equal. Wherein the equal distance means that the vertical distance from any point in the easy demagnetization region to the interface is equal, and wherein the equal thickness means that the Re2Fe 14 The difference of the thickness of the shell of the B main phase crystal grain is less than 0.1 μm.

[0079] In some embodiments of the present application, in the soft magnetic region, the thickness of the Re2Fe 14 The difference of the thickness of the shell of the B main phase grains is less than 0.1 μm.

[0080] In some embodiments of the present application, in the transition region, the thickness of the Re2Fe 14 The thickness of the shell of the B main phase grains is equal. Wherein, the meaning of equal distance is that the vertical distance of any point in the transition region to the interface is equal, and the meaning of equal thickness is that the Re2Fe 14 The difference of the thickness of the shell of the B main phase grains is less than 0.1 μm.

[0081] In some embodiments of the present application, in the transition region, the thickness of the Re2Fe 14 The difference of the thickness of the shell of the B main phase grains is less than 0.1 μm.

[0082] In some embodiments of the present application, the Re2Fe 14 The size ratio of the B main phase grains is 1:1:1.

[0083] Preferably, in the soft magnetic region, the transition region and the non-soft magnetic region, the surface Re2Fe 14 The size of the B main phase grains is center Re2Fe 14 1-1.5 times of the size of the B main phase grains.

[0084] Preferably, in the soft magnetic region, the transition region and the non-soft magnetic region, the surface Re2Fe 14 The size of the B main phase grains is 1-12 μm.

[0085] When the R2 is Tb, the content of R2 in the soft magnetic region, the transition region and the non-soft magnetic region satisfies the following condition: soft magnetic region≥transition region>non-soft magnetic region.

[0086] wherein, when the R2 is Dy, the content of R2 in the easy demagnetization region, the transition region and the non-easy demagnetization region satisfies the following conditions: non-easy demagnetization region ≥ transition region > easy demagnetization region.

[0087] wherein, preferably, the Re-rich phase grain boundary and the Re2Fe 14 The thickness ratio of the shell layer of the B main phase grain is (0-1):(0.5-1.5) and is not 0.

[0088] wherein, preferably, the thickness of the shell layer of the main phase grain of the easy demagnetization region is 0-4 μm, more preferably 0-2 μm, and further more preferably 0.5-1.5 μm.

[0089] wherein, preferably, the thickness of the Re-rich phase grain boundary of the easy demagnetization region is 0-1 μm and is not 0.

[0090] In a specific embodiment of the present application, the Re2Fe 14 The thickness of the shell layer of the B main phase grain is 1 μm, and the thickness of the Re-rich phase grain boundary of the easy demagnetization region is 0.3 μm.

[0091] wherein, preferably, the Re2Fe 14 The thickness ratio of the shell layer and the Re-rich phase grain boundary of the B main phase grain is preferably (0-2.5):(0-1), and the Re2Fe 14 The thickness of the shell layer and the Re-rich phase grain boundary of the B main phase grain is not 0.

[0092] wherein, preferably, the Re2Fe 14 The thickness of the shell layer of the B main phase grain is preferably 0-4 μm, and more preferably 0-2.5 μm.

[0093] wherein, preferably, the thickness of the Re-rich phase grain boundary of the transition region is 0-1 μm and is not 0.

[0094] In a specific embodiment of the present application, the Re2Fe 14 The thickness of the shell layer of the B main phase grain is 1 μm, and the thickness of the Re-rich phase grain boundary of the transition region is 0.4 μm.

[0095] wherein, preferably, the Re-rich phase grain boundary and the Re2Fe 14 The thickness ratio of the shell layer of the B main phase grain is (0-1):(0.5-1.5) and is not 0.

[0096] wherein, preferably, the Re2Fe 14 The thickness of the shell layer of the B main phase grain is preferably 0-4 μm, more preferably 0-2 μm, and further more preferably 0.5-1 μm.

[0097] Preferably, the thickness of the Re-rich phase grain boundary of the non-soft-remanence region is 0-1 μm and is not 0.

[0098] In one embodiment of the present application, the Re2Fe 14 The thickness of the shell layer of the B main phase grain is 1 μm, and the thickness of the Re-rich phase grain boundary of the non-soft-remanence region is 0.2 μm.

[0099] In the present application, the non-soft-remanence region, the transition region and the soft-remanence region are preferably obtained by simulation cloud diagram under working conditions.

[0100] The present application also provides a preparation method of the above-mentioned Nd-Fe-B magnet, which comprises the following steps: applying a first diffusion source, a second diffusion source and a third diffusion source to the center direction respectively around the annular edge of the upper surface and / or the lower surface perpendicular to the orientation direction of the Nd-Fe-B substrate and performing grain boundary diffusion to form a soft-remanence region, a transition region and a non-soft-remanence region; the first diffusion source, the second diffusion source and the third diffusion source each independently contain Dy and / or Tb.

[0101] 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 the grain boundary diffusion, and the utilization rate is generally 85%-95%, so a larger amount of Dy or Tb is generally applied in the actual preparation process.

[0102] In the present application, preferably, the first diffusion source is a Tb-containing diffusion source, and more preferably, the third diffusion source is a Dy-containing diffusion source. In the present application, the first diffusion source is a Tb-containing diffusion source, and the third diffusion source is a Dy-containing diffusion source, and a small amount of Tb in the applied first diffusion source may diffuse to the non-soft-remanence region after diffusion.

[0103] In some embodiments of the present application, the first diffusion source, the second diffusion source and the third diffusion source each independently are elemental Dy.

[0104] In other embodiments of the present application, the first diffusion source, the second diffusion source and the third diffusion source each independently are a Dy-M alloy, and M contains one or more of Cu, Al, Co, Ga, Zr and Ti. Preferably, the mass percentage of M in the Dy-M is 0-40% and is not 0.

[0105] In other embodiments of the present application, the first diffusion source, the second diffusion source and the third diffusion source each independently are a hydride of Dy or a fluoride of Dy.

[0106] In some embodiments of the present application, the first diffusion source, the second diffusion source and the third diffusion source are each independently elemental Tb.

[0107] In some embodiments of the present application, the first diffusion source, the second diffusion source and the third diffusion source are each independently a Tb-M alloy, M comprises one or more of Cu, Al, Co, Ga, Zr and Ti. Preferably, the mass percentage of M in the Tb-M is 0-40%, and is not 0.

[0108] In some embodiments of the present application, the first diffusion source, the second diffusion source and the third diffusion source are each independently a hydride of Tb or a fluoride of Tb.

[0109] In the present application, the application mode can be performed by conventional methods in the art, for example, by coating.

[0110] In the present application, it is generally 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 a magnet, therefore the coating thickness is not limited in the present application, as long as the corresponding content is achieved.

[0111] Preferably, the coating method is spraying or printing.

[0112] Preferably, the dewaxing temperature of the spraying is 200-400°C.

[0113] Preferably, the dewaxing temperature of the printing is 100-500°C.

[0114] In some embodiments of the present application, when the first diffusion source, the second diffusion source and the third diffusion source are applied by the coating method, the first diffusion source, the second diffusion source and the third diffusion source further comprise a solvent and a binder.

[0115] Preferably, the solvent is conventional in the art, for example, water, alcohol, ketone or ester.

[0116] In the present application, preferably, the mass percentage of Dy in the third diffusion source is 0.3%-1.2%, the mass percentage of Tb in the first diffusion source is 0.3%-1.2%, the mass percentage of Tb in the second diffusion source is 0.3%-1.2%, and the mass percentage of Dy in the second diffusion source is 0.3%-1%.

[0117] In the present application, preferably, the temperature of the grain boundary diffusion is 750-950°C, for example, 900°C.

[0118] In the present application, preferably, the time for the grain boundary diffusion is 5-30h, for example, 10h.

[0119] In the present application, preferably, the grain boundary diffusion is followed by an aging treatment.

[0120] In the present application, preferably, the temperature for the aging treatment is 300-600℃, for example, 500℃.

[0121] In the present application, preferably, the time for the aging treatment is 1-10h, for example, 3h.

[0122] The present application also provides a Nd-Fe-B magnet prepared by the above method.

[0123] On the basis of common general knowledge in the art, the above preferred conditions can be combined arbitrarily, i.e. to obtain each preferred example of the present application.

[0124] The reagents and raw materials used in the present application are commercially available.

[0125] The positive progress effect of the present application is that:

[0126] The present application can reduce the mutual diffusion of Tb or Dy across the region due to the difference in the Tb concentration gradient in the transition region, thereby causing the performance of the interface region to present a gradient decline and weakening the anti-demagnetization effect, can reduce the surface magnetic and magnetic flux decay of the Nd-Fe-B magnet under the premise of ensuring the remanence of the Nd-Fe-B magnet, and improve the anti-demagnetization ability of the Nd-Fe-B magnet. BRIEF DESCRIPTION OF DRAWINGS

[0127] Fig. 1 is a structural schematic diagram of the Nd-Fe-B magnet of Examples 1-3 and Comparative Examples 1-2.

[0128] The reference signs are as follows: 1-non-easy-demagnetization region; 2-transition region; 3-easy-demagnetization region. DETAILED DESCRIPTION

[0129] The present application will be further described by way of examples, but the present 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 instructions of the commercial products.

[0130] Examples 1-3 and Comparative Example 1

[0131] The Nd-Fe-B magnet provided in Examples 1-3 and Comparative Example 1 is a cuboid, and the structural schematic diagram of the Nd-Fe-B magnet is shown in Fig. 1, wherein the orientation direction is the positive direction of Z axis, the X axis is parallel to one side of the upper surface, and the origin of the three-dimensional rectangular coordinate system is located in the Nd-Fe-B magnet.

[0132] The Nd-Fe-B magnet comprises a non-remanence easy zone, a transition zone and a remanence easy zone; the remanence easy zone is a rectangular outer edge annular region on the Nd-Fe-B magnet along the Z-axis direction, the non-remanence easy zone is a central region on the Nd-Fe-B magnet along the Z-axis direction and is rectangular; the transition zone is an interface region between the remanence easy zone and the non-remanence easy zone; the content of heavy rare earth in each zone is listed in Table 2. Since the content of heavy rare earth metal in the substrate is 0, the content of heavy rare earth in Examples 1-3 and Comparative Example 1 is equal to its diffusion weight gain.

[0133] The volume percentage of the remanence easy zone, the transition zone and the non-remanence easy zone in the volume of the Nd-Fe-B magnet, the coercivity ratio of the remanence easy zone and the non-remanence easy zone and other parameters are listed in Table 3.

[0134] In Examples 1-3 and Comparative Example 1, there is an interface A between the transition zone and the corresponding remanence easy zone, the interface A is annular; there is an interface B between the transition zone and the corresponding non-remanence easy zone, the interface B is annular. The content ratio of the interface A, B and the remanence easy zone is listed in Table 4.

[0135] The mass concentration of each element in the substrate of Examples 1-3 and Comparative Example 1 is the same and is listed in Table 5.

[0136] The microstructure of Examples 1-3 and Comparative Example 1 is listed in Table 1:

[0137] Table 1

[0138] Table 2

[0139] Table 3

[0140] Table 4

[0141] Table 5

[0142] The preparation method of Examples 1-3 and Comparative Example 1 comprises the following steps: coating a first diffusion source, a second diffusion source and a third diffusion source on the upper surface of the Nd-Fe-B substrate in the direction perpendicular to the orientation direction and towards the center of the annular edge respectively and performing grain boundary diffusion to form a remanence easy zone, a transition zone and a non-remanence easy zone; the first diffusion source, the second diffusion source and the third diffusion source are each independently elemental Dy and elemental Tb;

[0143] The temperature of the grain boundary diffusion is 900℃; the time of the grain boundary diffusion is 10h; the grain boundary diffusion is followed by aging treatment; the temperature of the aging treatment is 500℃; the time of the aging treatment is 3h; the coating method is spraying; and the dewaxing temperature of the spraying is 300℃.

[0144] Example 1

[0145] The Nd-Fe-B magnets of Examples 1-3 and Comparative Example 1 were subjected to the following tests:

[0146] 1. Coercivity test: The samples of Examples 1-3 and Comparative Example 1 were prepared, and the sample size was W2-3±0.1*L19±0.1*T4±0.1mm. Two pieces were stacked and tested, and a W3*L19-20*T2.7mm coil was used to measure the permanent magnet in a permanent magnet precision measurement system NIM-62000 at room temperature (temperature ≤200℃).

[0147] 2. Demagnetization rate test: An electromagnetic simulation software, Ansys Workbench, was used to input the speed of 13000rmp, and then the temperature was adjusted to the corresponding temperature working condition. The back electromotive force data of the motor and the magnetic steel cloud atlas changes were collected under the same time to identify whether the magnetic steel demagnetized. The calculation formula of the demagnetization rate was: demagnetization rate=(high-temperature back electromotive force- room-temperature back electromotive force) / room-temperature back electromotive force.

[0148] 3. The test method and test instrument of the line scan were as follows: the selected area of the magnet surface was microphotographed under the equipment EMMA, the equipment model was JEOL 8530f, the shooting magnification was X3000, and the two main phases were pulled and scanned, which represented the distribution of Dy / Nd and other elements.

[0149] The technical effects of Examples 1-3 and Comparative Example 1 are listed in Table 6 below:

[0150] Table 6

[0151] As shown in Table 6 above, the coercivity ratio of the transition zone to the easy demagnetization zone of the Nd-Fe-B magnets prepared in Examples 1-3 was between (0.94-0.99): 1, the coercivity difference between the easy demagnetization zone and the non-easy demagnetization zone was between 2.0-5kOe, and the magnets had excellent demagnetization resistance. The demagnetization rate of the Nd-Fe-B magnets of Examples 1-3 at 130℃ was only 2.0%-5.2%.

[0152] The Tb content of the easy demagnetization zone of Comparative Example 1 is too low, and the content of Dy in the non-easy demagnetization zone is slightly high, specifically 4:1. The ratio of coercivity of the easy demagnetization zone to the non-easy demagnetization zone of the Nd-Fe-B magnet of Comparative Example 1 is about 0.96:1, and the difference in coercivity between the easy demagnetization zone and the non-easy demagnetization zone is -1 kOe. The anti-demagnetization ability of the Nd-Fe-B magnet prepared in Comparative Example 1 is poor, and the demagnetization rate thereof at 130°C is 8.1%, which is higher than that of Examples 1-3.

[0153] The above-described examples are only better embodiments of the present application, and facilitate those skilled in the art to understand and use the present application. Obviously, any skilled person in the art can make slight modifications or changes to the present embodiments without creative labor, and apply them to other embodiments. Therefore, the present application is not limited to the above-described examples, and any equivalent changes, simple modifications and modifications within the scope of the present application still belong to the scope of the present application.

Claims

1. A neodymium-iron-boron magnet, characterized in that A three-dimensional rectangular coordinate system is established, wherein the orientation direction is the positive direction of the Z axis, the X axis is parallel to the upper surface, and the origin of the three-dimensional rectangular coordinate system is located in the Nd-Fe-B magnet; The Nd-Fe-B magnet comprises a non-easy demagnetization area, a transition area and an easy demagnetization area; the easy demagnetization area is an annular area located on the outer edge of the Nd-Fe-B magnet along the Z axis direction, and the non-easy demagnetization area is a central area located on the Nd-Fe-B magnet along the Z axis direction; the transition area is an interface area located between the easy demagnetization area and the non-easy demagnetization area; The content ratio of Tb in the transition area to the easy demagnetization area is (0.7-1):1; The content ratio of Tb in the transition area to the non-easy demagnetization area is 1:(0-0.9); The content ratio of Dy in the transition area to the easy demagnetization area is (0-1):(0-0.9); The content ratio of Dy in the transition area to the non-easy demagnetization area is (0-0.98):

1.

2. The neodymium-iron-boron magnet according to claim 1, characterized in that The content ratio of Tb in the transition area to the easy demagnetization area is 0.71:1, 0.8:1 or 0.83:1; And / or, the diffusion weight gain ratio of Tb in the transition area to the easy demagnetization area is (0.7-1):1, preferably 0.71:1, 0.8:1 or 0.83:1; And / or, the content ratio of Tb in the transition area to the non-easy demagnetization area is 1:(0-0.2), preferably 1:(0-0.05), for example 1:0.02 or 1:0.05; And / or, the diffusion weight gain ratio of Tb in the transition area to the non-easy demagnetization area is 1:(0-0.2), preferably 1:(0-0.05), for example 1:0.02 or 1:0.05; And / or, the content ratio of Dy in the transition area to the easy demagnetization area is (0.05-0.9):(0-0.05), preferably 1:(0-0.9), more preferably 1:(0-0.8), for example 8:1, 37:5 or 23:5; And / or, the diffusion weight gain ratio of Dy in the transition area to the easy demagnetization area is (0.05-0.9):(0-0.05), preferably 1:(0-0.9), more preferably 1:(0-0.8), for example 8:1, 37:5 or 23:5; And / or, the content ratio of Dy in the transition area to the non-easy demagnetization area is (0.05-0.9):1, preferably 0.57:1, 0.58:1 or 0.67:1; And / or, the diffusion weight gain ratio of Dy in the transition area to the non-easy demagnetization area is (0.05-0.9):1, preferably 0.57:1, 0.58:1 or 0.67:1; And / or, the content ratio of Tb in the non-easy demagnetization area to the easy demagnetization area is (0-0.05):1, preferably (0-0.03):1, for example 0.01:1 or 0.02:1; And / or, the diffusion weight gain ratio of Tb in the non-easy demagnetization area to the easy demagnetization area is (0-0.05):1, preferably (0-0.03):1, for example 0.01:1 or 0.02:1; and / or, the content ratio of Dy in the easy demagnetization region and the non-easy demagnetization region is (0-0.05):(0.3-1) and not 0, preferably (0-0.03):(0.3-0.7) and not 0, for example 0.07:1, 0.09:1 or 0.13:1; and / or, the content ratio of Dy in the easy demagnetization region and the non-easy demagnetization region is (0-0.05):(0.3-1) and not 0, preferably (0-0.03):(0.3-0.7) and not 0, for example 0.07:1, 0.09:1 or 0.13:1; and / or, the content of Tb in the easy demagnetization region is 0.1wt%-2.5wt%, for example 0.4wt%, 0.55wt% or 0.7wt%; and / or, the content of Tb in the non-easy demagnetization region is 0-1.6wt%, for example 0.015wt% or 0.01wt%; and / or, the content of Tb in the transition region is 0.1wt%-2.5wt%, for example 0.33wt%, 0.4wt% or 0.5wt%; and / or, the content of Dy in the easy demagnetization region is 0-3.1wt%, for example 0.05wt%; and / or, the content of Dy in the non-easy demagnetization region is 0.1wt%-4wt%, preferably 0.4wt%-0.7wt%, for example 0.5wt% or 0.55wt%; and / or, the content of Dy in the transition region is 0.05wt%-3.9wt%, preferably 0.05wt%-0.4wt%, for example 0.23wt% or 0.37wt%; and / or, the volume percentage of the easy demagnetization region in the volume of the Nd-Fe-B magnet is preferably 20%-80%, more preferably 29%-70%, for example 54.6% or 42.48%; and / or, the content of Tb at any two points in the easy demagnetization region is equal; and / or, the diffusion weight gain of Tb at any two points in the non-easy demagnetization region is equal; and / or, the content of Dy at any two points in the non-easy demagnetization region is equal; and / or, the diffusion weight gain of Dy at any two points in the non-easy demagnetization region is equal.

3. The neodymium-iron-boron magnet of claim 1, wherein, The width of the easy demagnetization region is preferably 0-5mm and not 0, more preferably 2-4mm; the width means the length covered by the easy demagnetization region along the direction perpendicular to the circumference at the origin; and / or, the volume percentage of the transition region in the volume of the Nd-Fe-B magnet is 5%-15%, preferably 10%-14%, more preferably 10.6%-13.65%; and / or, the volume percentage of the non-easy demagnetization region in the volume of the Nd-Fe-B magnet is 20%-75%, preferably 24.18%-70.66%, more preferably 34.27%-57.5%; and / or, the coercivity ratio of the easy demagnetization region and the non-easy demagnetization region is 1:(0.7-0.96), preferably 1:(0.8-0.9), for example 1:0.85; and / or, the shape of the easy demagnetization region in any plane perpendicular to the orientation direction is a rectangular outer annular region; And / or, the shape of the non-remanence easy area is rectangular in any plane perpendicular to the orientation direction; And / or, the neodymium iron boron magnet is a cuboid; And / or, the ratio of the length to the thickness of the neodymium iron boron magnet is (3-25):1, preferably (3.64-24.27):1, more preferably (8.74-24.27):1, for example 12.85:1; the length refers to the extension distance of one side of the upper surface along the positive direction of the X axis; the thickness refers to the extension distance of the cuboid from the upper surface along the positive direction of the Z axis.

4. The neodymium-iron-boron magnet of claim 1, wherein, The transition area and the remanence easy area exist an interface A, and the interface A is annular; Preferably, the content of Tb of the interface A is 0.1wt%-2.5wt%, for example 0.35wt%, 0.4wt%, 0.5wt% or 0.55wt%; Preferably, the diffusion weight gain of Tb of the interface A is 0.1wt%-2.5wt%, for example 0.35wt%, 0.4wt%, 0.5wt% or 0.55wt%; Preferably, the content ratio of Tb of the interface A to the remanence easy area is (0.9-1):1; Preferably, the diffusion weight gain ratio of Tb of the interface A to the remanence easy area is (0.9-1):1; Preferably, the content of Dy of the interface A is 0.01wt%-3.5wt%, for example 0.05wt%; Preferably, the diffusion weight gain of Dy of the interface A is 0.01wt%-3.5wt%, for example 0.05wt%; Preferably, the content ratio of Dy of the interface A to the remanence easy area is (0.02-0.2):(0-0.05), more preferably 1:(0.8-1), for example 1:1; Preferably, the diffusion weight gain ratio of Dy of the interface A to the remanence easy area is (0.02-0.2):(0-0.05), more preferably 1:(0.8-1), for example 1:1; And / or, the transition area and the corresponding non-remanence easy area exist an interface B, and the interface B is annular; Preferably, the content of Tb of the interface B is 0.05wt%-2.4wt%, for example 0.22wt% or 0.23wt%; Preferably, the diffusion weight gain of Tb of the interface B is 0.05wt%-2.4wt%, for example 0.22wt% or 0.23wt%; Preferably, the content ratio of Tb of the interface B to the non-remanence easy area is 1:(0-0.94), more preferably 1:(0-0.2), further more preferably 1:(0-0.05), for example 1:0.04 or 1:0.045; Preferably, the diffusion weight gain ratio of Tb of the interface B to the non-remanence easy area is 1:(0-0.94), more preferably 1:(0-0.2), further more preferably 1:(0-0.05), for example 1:0.04 or 1:0.045; wherein the content of Dy in the interface B is preferably 0.08wt%-4wt%, for example 0.37wt% or 0.23wt%; wherein the diffusion weight gain of Dy in the interface B is 0.05wt%-1wt%, for example 0.37wt%; wherein the content of Dy in the interface B and the non-freemagnetic region is preferably (0.5-1):1, for example 0.57:1, 0.67:1 or 0.58:1; wherein the diffusion weight gain ratio of Dy in the interface B and the non-freemagnetic region is preferably (0.1-0.7):1, for example 0.13:1, 0.14:1, 0.22:1 or 0.4:

1.

5. 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 core layer and a shell layer; the Re is Dy and / or Tb; wherein, preferably, the Re2Fe 14 The shell of the B main phase grains comprises (Nd, Tb)2Fe 14 B hard magnetic layer; wherein, preferably, the Re2Fe 14 The shell of the B main phase grains comprises (Nd, Dy)2Fe 14 B hard magnetic layer; wherein, preferably, the Re2Fe 14 the difference between the size of the B main phase crystal grains is not more than 1-8 μm; wherein, preferably, the Re2Fe 14 The difference of the size of the B main phase crystal grains is not more than 1-8 μm. wherein, preferably, the surface layer of the soft magnetic region, the transition region and the non-soft magnetic region has a Re2Fe 14 The B main phase crystal grains have equal particle sizes, wherein the surface layer means a surface perpendicular to the orientation direction. Preferably, the Re2Fe at the center of the easily demagnetized region, the transition region, and the non-easily demagnetized region. 14 The B principal phase grains have equal grain size, where the center refers to the mid-plane along the orientation direction; wherein, preferably, the Re2Fe 14 the core layer of the B main phase crystal grain and the Re2Fe 14 the shell layer of the B main phase crystal grain satisfies 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; and R2 is Dy and / or Tb. wherein, preferably, in the easy-remanence region, on a plane equidistant from the interface between the transition region and the easy-remanence region, the Re2Fe 14 the thickness of the shell of B main phase grains is equal; wherein preferably, in the freemagnetic region, the thickness of the Re-rich phase grain boundary on the surface equidistant to the interface between the transition region and the freemagnetic region is equal; wherein, preferably, in the transition zone, the Re2Fe 14 the thickness of the shell of B main phase grains is equal; wherein preferably, in the transition region, the thickness of the Re-rich phase grain boundary on the surface equidistant to the interface between the transition region and the freemagnetic region is equal.

6. The neodymium-iron-boron magnet of claim 5, wherein, Re2Fe 14 The size ratio of the B main phase crystal grains is 1:1:

1. and / or, in the easy demagnetization zone, the transition zone, and the non-easy demagnetization zone, the surface layer Re2Fe 14 The particle size of the B main phase crystal grains is 1-1.5 times the particle size of the center Re2Fe 14 The particle size of the B main phase crystal grains is 1-1.5 times the particle size of the center Re2Fe and / or, the surface layer Re2Fe of the demagnetization easy region, the transition region and the non-demagnetization easy region 14 The particle size of the B main phase crystal grains is 1-12 μm. and / or, when R2 is Tb, the content of R2 in the freemagnetic region, the transition region and the non-freemagnetic region satisfies the following condition: freemagnetic region≥transition region>non-freemagnetic region; and / or, when R2 is Dy, the content of R2 in the freemagnetic region, the transition region and the non-freemagnetic region satisfies the following condition: non-freemagnetic region≥transition region>freemagnetic region.

7. The neodymium-iron-boron magnet of claim 5, wherein, Re-rich phase grain boundaries and Re2Fe 14 the thickness ratio of the shell layer of the B main phase grains is (0-1):(0.5-1.5) and is not 0; and / or, Re2Fe 14 The thickness of the shell layer of the B main phase crystal grains is 0-4 μm, preferably 0-2 μm, and more preferably 0.5-1.5 μm. and / or, the thickness of the Re-rich phase grain boundary in the freemagnetic region is 0-1μm and not 0; and / or, the Re2Fe 14 The thickness of the shell layer of the B main phase crystal grains is 1 pm, and the thickness of the Re-rich phase grain boundary of the easy demagnetization region is 0.3 pm. and / or, the transition zone has a Re2Fe 14 the ratio of the thickness of the shell of B main phase grains and the Re-rich phase grain boundary is (0-2.5):(0-1), and the Re2Fe 14 the thickness of the shell of B main phase grains and the Re-rich phase grain boundary are not both 0; and / or the transition zone has a Re2Fe 14 The shell of the B main phase grains has a thickness of 0-4 μm, preferably 0-2.5 μm. and / or, the thickness of the Re-rich phase grain boundary in the transition region is 0-1μm and not 0; and / or, the transition zone has a Re2Fe 14 The shell of the B main phase grains has a thickness of 1 pm and the Re-rich phase grain boundary of the transition zone has a thickness of 0.4 pm. and / or, the Re-rich phase grain boundaries of the non-coercive region and the Re2Fe 14 the ratio of the thickness of the shell layer of the B main phase grains is (0-1):(0.5-1.5) and is not 0; and / or, Re2Fe 14 The thickness of the shell layer of the B main phase crystal grains is 0-4 μm, preferably 0-2 μm, and more preferably 0.5-1 μm. and / or, the thickness of the Re-rich phase grain boundary in the non-freemagnetic region is 0-1μm and not 0; and / or, the Re2Fe 14 The thickness of the shell of B main phase grains is 1 μm and the thickness of the Re-rich phase grain boundary of the non-reversible magnetic region is 0.2 μm.

8. A method of producing a neodymium-iron-boron magnet as claimed in any one of claims 1 to 7, characterized in that which comprises the following steps: applying a first diffusion source, a second diffusion source and a third diffusion source to the center direction respectively on the upper surface and / or the lower surface of the neodymium-iron-boron substrate around the annular edge perpendicular to the orientation direction and performing grain boundary diffusion to form a freemagnetic region, a transition region and a non-freemagnetic region; the first diffusion source, the second diffusion source and the third diffusion source each independently contains Dy and / or Tb.

9. The method of producing a neodymium-iron-boron magnet according to claim 8, characterized by, the first diffusion source is a Tb-containing diffusion source, preferably the third diffusion source is a Dy-containing diffusion source; and / or, the first diffusion source, the second diffusion source and the third diffusion source each independently is elemental Dy; and / or, the first diffusion source, the second diffusion source and the third diffusion source each independently is a Dy-M alloy, M contains one or more of Cu, Al, Co, Ga, Zr and Ti; wherein the mass percentage of M in the Dy-M is preferably 0-40% and not 0; and / or, the first diffusion source, the second diffusion source and the third diffusion source each independently is a hydride of Dy or a fluoride of Dy; and / or, the first diffusion source, the second diffusion source and the third diffusion source each independently is elemental Tb. and / or, each of the first diffusion source, the second diffusion source and the third diffusion source is independently a Tb-M alloy, M comprises one or more of Cu, Al, Co, Ga, Zr and Ti; wherein the mass percentage of M in the Tb-M is preferably 0-40%, and is not 0; and / or, each of the first diffusion source, the second diffusion source and the third diffusion source is independently a hydride of Tb or a fluoride of Tb; and / or, the mass percentage of Dy in the third diffusion source is 0.3%-1.2%, the mass percentage of Tb in the first diffusion source is 0.3%-1.2%, the mass percentage of Tb in the second diffusion source is 0.3%-1.2%, and the mass percentage of Dy in the second diffusion source is 0.3%-1%; and / or, the temperature of the grain boundary diffusion is 750-950℃, for example 900℃; and / or, the time of the grain boundary diffusion is 5-30h, for example 10h; and / or, the grain boundary diffusion further comprises an aging treatment; wherein the temperature of the aging treatment is preferably 300-600℃, for example 500℃; wherein the time of the aging treatment is preferably 1-10h, for example 3h; and / or, the application is for example coating; wherein, Preferably, the coating is spraying or printing; wherein the dewaxing temperature of the spraying is preferably 200-400℃; wherein the dewaxing temperature of the printing is preferably 100-500℃; Preferably, the first diffusion source, the second diffusion source and the third diffusion source further comprise a solvent and a binder; wherein the solvent is for example water, alcohol, ketone or ester.

10. A neodymium-iron-boron magnet prepared by the method of claim 8 or 9.

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