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 a use thereof. In the neodymium-iron-boron magnet, a first demagnetization-prone region, a second demagnetization-prone region, a third demagnetization-prone region, and a fourth demagnetization-prone region have the same heavy rare earth content; a first transition region, a second transition region, a third transition region, and a fourth transition region have the same heavy rare earth content; the content ratio of Tb in a demagnetization-resistant region to Tb in the first demagnetization-prone region is (0-0.9):1; the content ratio of Dy in the first demagnetization-prone region to Dy in the easy demagnetization-resistant region is (0-0.9):1; and the content ratio of Tb in the first transition region to Tb in the first demagnetization-prone region is (0.5-0.96):1. The neodymium-iron-boron magnet of the present invention can have good resistance to demagnetization while ensuring the remanence of the neodymium-iron-boron magnet.

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 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 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 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, 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 only 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, the reverse magnetic field generated after the coil is energized in the motor is not a uniform magnetic field. According to different application requirements, the shape of the magnet is also different. Therefore, how to design a neodymium-iron-boron magnet according to the requirements of different regions to meet the needs of different applications, and how to accurately use heavy rare earth elements to save costs, while ensuring the coercivity and remanence, and also having good demagnetization resistance, is a problem to be solved. SUMMARY

[0005] The present application mainly overcomes the defects of high cost and poor demagnetization resistance of the neodymium-iron-boron magnet in the prior art, and provides a neodymium-iron-boron magnet, a method for preparing the same and use thereof. The neodymium-iron-boron magnet of the present application has good demagnetization resistance performance while ensuring the remanence of the neodymium-iron-boron magnet.

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

[0007] The application provides a neodymium-iron-boron magnet, which 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;

[0008] 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 arranged at the four corners of the cuboid along the Z axis direction respectively and not in contact with each other;

[0009] The transition area is located at the junction area 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;

[0010] The heavy rare earth content of the first easy demagnetization area, the second easy demagnetization area, the third easy demagnetization area and the fourth easy demagnetization area is the same;

[0011] The heavy rare earth content of the first transition area, the second transition area, the third transition area and the fourth transition area is the same;

[0012] The content ratio of Tb in the non-easy demagnetization area and the first easy demagnetization area is (0-0.9):1;

[0013] The content ratio of Dy in the first easy demagnetization area and the non-easy demagnetization area is (0-0.9):1;

[0014] The content ratio of Tb in the first transition area and the first easy demagnetization area is (0.5-0.96):1.

[0015] In the application, the heavy rare earth element can be derived from a base material and / or a diffusion process.

[0016] In the application, the content of heavy rare earth refers to the percentage of the mass of heavy rare earth in a certain area in the total mass of the magnet in the area, for example, the content of Tb in the first easy demagnetization area refers to the percentage of the mass of Tb in the first easy demagnetization area in the total mass of the magnet in the first easy demagnetization area.

[0017] In the 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 area in the total mass of the magnet in the area, for example, the diffusion weight gain of Tb in the first easy demagnetization area refers to the percentage of the mass of Tb introduced by diffusion in the first easy demagnetization area in the total mass of the magnet in the first easy demagnetization area.

[0018] In the present application, the "diffusion weight gain of heavy rare earth is the same" means that 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.

[0019] 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.

[0020] In the present application, the content ratio of Tb in the non-reversible demagnetization region to the first reversible demagnetization region can be (0-0.2):1, for example, 0.08:1, 0.17:1 or 0.02:1.

[0021] In the present application, the diffusion weight gain ratio of Tb in the non-reversible demagnetization region to the first reversible demagnetization region can be (0-0.05):(0.3-1), preferably (0-0.05):(0.3-0.6), for example, 0.05:0.6, 0.05:0.3 or 0.01:0.6.

[0022] In the present application, the content ratio of Dy in the first reversible demagnetization region to the non-reversible demagnetization region can be (0-0.8):1, for example, 0.1:1.

[0023] In the present application, the diffusion weight gain ratio of Dy in the first reversible demagnetization region to the non-reversible demagnetization region can be (0-0.05):(0.3-1), preferably (0-0.05):(0.3-0.5), for example, 0.05:0.5.

[0024] In the present application, the diffusion weight gain ratio of Tb in the first transition region to the first reversible demagnetization region can be (0.5-0.8):1, for example, 0.8:1.

[0025] In the present application, the content ratio of Tb in the first transition region to the first reversible demagnetization region can be (0.5-0.9):1, for example, 0.8:1.

[0026] In the present application, the diffusion weight gain of Dy in the first reversible demagnetization region is 0.05wt% and below, for example, 0.05wt%.

[0027] In the present application, the content of Dy in the first reversible demagnetization region is 0-3.1wt%, for example, 0.05wt%.

[0028] In the present application, the diffusion weight gain of Dy in the first transition region can be 0.05wt%-0.9wt%, preferably 0.1wt%-0.4wt%, for example, 0.25wt%.

[0029] In the present application, the content of Dy in the first transition region can be 0.05-3.9wt%, for example, 0.25wt%.

[0030] In the present application, the Dy diffusion weight gain of the non-freely demagnetized region can be 0.1wt%-1wt%, preferably 0.4wt%-0.7wt%, for example 0.5wt%.

[0031] In the present application, the content of Dy of the non-freely demagnetized region can be 0.1-4wt%, for example 0.5wt%.

[0032] In the present application, the Tb diffusion weight gain of the first freely demagnetized region can be 0.1wt%-1wt%, for example 0.6wt%.

[0033] In the present application, the content of Tb of the first freely demagnetized region can be 0.1wt%-2.5wt%, for example 0.6wt%.

[0034] In the present application, the Tb diffusion weight gain of the non-freely demagnetized region can be 0.05wt% and below, for example 0.

[0035] In the present application, the content of Tb of the non-freely demagnetized region can be 0wt%-1.6wt%, for example 0.01wt%, 0.02wt% or 0.05wt%. In the present application, the Tb diffusion weight gain of the first transition region can be 0.05wt%-0.9wt%, for example 0.35wt%, 0.53wt% or 0.48wt%.

[0036] In the present application, the content of Tb of the first transition region can be 0.1wt%-2.4wt%, for example 0.35wt% or 0.48wt%.

[0037] In the present application, in any plane perpendicular to the orientation direction, the Tb diffusion weight gain ratio of the first freely demagnetized region to the non-freely demagnetized region is 1:(1 / L-1), wherein L is the interval between sampling regions, and the value of L is >1.

[0038] In the present application, the Nd-Fe-B magnet can be represented by the chemical formula R1-R2-T-B-M, wherein R1 includes one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 is Dy and / or Tb; T includes 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 element includes one or more of Cu, Al, Co, Ga, Zr and Ti.

[0039] In some embodiments, the M element is entirely from the Nd-Fe-B base material.

[0040] In some preferred embodiments, the first, second, third and fourth easy demagnetization regions have the same coercivity.

[0041] In some preferred embodiments, the first, second, third and fourth easy demagnetization regions have the same coercivity.

[0042] In some preferred embodiments, the first, second, third and fourth easy demagnetization regions have the same coercivity.

[0043] In the present application, the ratio of the coercivity of the non-easy demagnetization region to the first easy demagnetization region can be (0.7-0.96):1, more preferably (0.8-0.9):1, for example 0.86:1, 0.88:1 or 0.90:1.

[0044] In the present application, the difference of the coercivity of the first easy demagnetization region to the non-easy demagnetization region can be 0-10kOe, more preferably 2-5kOe, for example 2.6kOe, 3.1kOe or 3.6kOe.

[0045] In the present application, the ratio of the coercivity of the first transition region to the first easy demagnetization region can be (0.8-0.98):1, for example 0.96:1.

[0046] In the present application, 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.

[0047] In the present application, the remanence of the first, second, third and fourth easy demagnetization regions is the same; the remanence of the first, second, third and fourth transition regions is the same.

[0048] In the present application, the ratio of the remanence of the first easy demagnetization region to the non-easy demagnetization region can be (0.99-1):1, for example 1:1.

[0049] In the present application, the ratio of the remanence of the first transition region to the non-easy demagnetization region can be (0.99-1):1, for example 1:1.

[0050] In the present application, in any plane perpendicular to the orientation direction, the shape of the first, second, third and fourth easy demagnetization regions is independently selected from a rectangle, a sector or a triangle. The shape of the transition region and the non-easy demagnetization region corresponds to the shape of the easy demagnetization region.

[0051] When the first, second, third and fourth easy demagnetization regions are all rectangular, the first, second, third and fourth transition regions are all L-shaped, and the non-easy demagnetization region is cross-shaped.

[0052] In some preferred embodiments, the first, second, third and fourth easy demagnetization regions are all rectangular and have the same width, and the width of the easy demagnetization region refers to the distance extending along the X-axis or Y-axis from the edge of the Nd-Fe-B magnet.

[0053] In the present application, the first, second, third and fourth transition regions have the same width, and 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-axis or Y-axis.

[0054] In some embodiments, the ratio of the width of the first easy demagnetization region to the total width of the Nd-Fe-B magnet can be (0.05-0.6):1.

[0055] In some embodiments, the ratio of the width of the non-easy demagnetization region to the total width of the Nd-Fe-B magnet can be (0.2-1):1, and 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.

[0056] In some embodiments, the ratio of the width of the first transition region to the total width of the Nd-Fe-B magnet can be (0-0.1):1 and is not 0, for example, 0.08:1.

[0057] In some embodiments, the width of the first transition region is preferably 0-1 mm and is not 0.

[0058] In the present application, the ratio of the length to the thickness of the Nd-Fe-B magnet can be <3, and preferably the thickness of the Nd-Fe-B magnet is 0.5-5 mm; the length refers to the distance extending in the positive direction of the X-axis from one edge of the upper surface; and the thickness refers to the distance extending in the positive direction of the Z-axis from the upper surface of the cuboid.

[0059] In some specific embodiments, the ratio of the length to the thickness of the Nd-Fe-B magnet is 2.5.

[0060] In the present application, the thickness of the Nd-Fe-B magnet can be >5 mm, and the thickness refers to the distance extending in the positive direction of the Z-axis from the upper surface of the cuboid.

[0061] In the present application, the grain boundary structure of the Nd-Fe-B magnet comprises Re2Fe 14 B primary phase grains and Re-rich phase grain boundaries; the Re2Fe14 The B main phase grains comprise a core layer and a shell layer; the Re is Dy and / or Tb.

[0062] wherein the shell layer of the main phase grains is as conventionally understood in the art, i.e. (Nd, Dy / Tb)2Fe 14 B hard magnetic layer. The Re-rich phase grain boundary region is as conventionally understood in the art, i.e. a region of the grain boundary between two particles that is >95% Re.

[0063] In some embodiments, the thickness of the shell layer of the main phase grains in the first, second, third and fourth easy-remanence regions is the same.

[0064] In some embodiments, the thickness of the shell layer of the main phase grains in the first, second, third and fourth transition regions is the same.

[0065] In some embodiments, the thickness of the Re-rich phase grain boundary in the first, second, third and fourth easy-remanence regions is the same.

[0066] In some embodiments, the thickness of the Re-rich phase grain boundary in the first, second, third and fourth transition regions is the same.

[0067] In some embodiments, the thickness of the shell layer of the main phase grains in the first easy-remanence region, the first transition region and the non-easy-remanence region is preferably 0-4 μm, more preferably 0-2 μm.

[0068] In some embodiments, the thickness of the Re-rich phase grain boundary in the first easy-remanence region, the first transition region and the non-easy-remanence region is preferably 0-1 μm, but not 0.

[0069] In some embodiments, the ratio of the thickness of the shell layer of the main phase grains to the thickness of the Re-rich phase grain boundary in the first easy-remanence region, the first transition region and the non-easy-remanence region is preferably (0-2.0):(0-1), but not 0.

[0070] In some embodiments, the particle size of the main phase grains in the first, second, third and fourth easy-remanence regions is the same.

[0071] In some embodiments, the particle size of the main phase grains in the first, second, third and fourth transition regions is the same.

[0072] In some embodiments, the ratio of the particle size of the main phase grains in the first easy-remanence region, the first transition region and the non-easy-remanence region is 1:1:1.

[0073] In some embodiments, the grain size of the surface layer main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone is the same, preferably 1-12 μm.

[0074] In some embodiments, the grain size of the surface layer main phase grains of 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 center main phase grains.

[0075] In some embodiments, 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 comprises one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; and R2 is Dy and / or Tb.

[0076] In some embodiments, the content of R2 in the shell layer of the main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone satisfies the following conditions:

[0077] When the R2 is Tb, the first easy demagnetization zone ≥ the first transition zone > the non-easy demagnetization zone.

[0078] When the R2 is Dy, the non-easy demagnetization zone ≥ the first transition zone > the first easy demagnetization zone.

[0079] The present application also provides a preparation method of the above-mentioned Nd-Fe-B magnet, comprising the following steps: applying a diffusion source of Dy on the non-quadrangular regions of the upper surface and the lower surface of an Nd-Fe-B substrate, and applying a diffusion source of Tb on the portions of the four side surfaces perpendicular to the upper surface corresponding to the quadrangular regions of the upper surface, so that the diffusion source of Tb performs grain boundary diffusion perpendicular to the orientation direction, thereby obtaining the Nd-Fe-B magnet; wherein the quadrangular regions form the easy demagnetization zone through grain boundary diffusion; and the non-quadrangular regions form the non-easy demagnetization zone and the transition zone.

[0080] 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.

[0081] In some preferred embodiments, the preparation method of the Nd-Fe-B magnet preferably comprises the following steps: applying a Tb diffusion source on the easy demagnetization zone of the side surface of the Nd-Fe-B substrate, applying a Dy diffusion source on the non-easy demagnetization zone of the upper surface or the side surface of the Nd-Fe-B substrate, and performing grain boundary diffusion, thereby obtaining the Nd-Fe-B magnet.

[0082] In the preferred embodiment described above, during the diffusion process, a Tb diffusion source is applied only to the side surface of the easily demagnetized region, while no Tb diffusion source is applied to the non-easily demagnetized region. However, after diffusion, a small amount of Tb applied to the easily demagnetized region may diffuse toward the center of the magnet. The diffused Tb will be distributed at the boundary between the easily demagnetized region and the non-easily demagnetized region, where the Tb content is low.

[0083] In this invention, those skilled in the art know that different grain boundary diffusion methods will result in different coating thicknesses when diffusing the same amount of Dy or Tb into the magnet. Therefore, in the actual preparation process, the coating thickness is not limited, as long as the corresponding amount of Dy or Tb diffusion is achieved.

[0084] In some implementations, the diffusion source is pure Dy.

[0085] In other embodiments, the diffusion source is a Dy-M alloy, where M comprises 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 not zero.

[0086] In other embodiments, the diffusion source is a Dy hydride or a Dy fluoride.

[0087] In some implementations, the diffusion source is pure Tb.

[0088] In other embodiments, the diffusion source is a Tb-M alloy, where M comprises one or more of Cu, Al, Co, Ga, Zr, and Ti. The mass percentage of M in the Tb-M alloy is 0-40%, and not zero.

[0089] In other embodiments, the diffusion source is a Tb hydride or a Tb fluoride.

[0090] In some implementations, the diffusion source is pure Tb.

[0091] In other embodiments, the diffusion source is a Tb-M alloy, where M comprises one or more of Cu, Al, Co, Ga, Zr, and Ti. The mass percentage of M in the Tb-M alloy is 0-40%, and not zero.

[0092] In other embodiments, the diffusion source is a Tb hydride or a Tb fluoride.

[0093] In this invention, the diffusion source can be applied using methods conventional in the art, such as coating.

[0094] The coating method is preferably spraying or printing. The dewaxing temperature of the spraying is preferably 200-400℃, and the dewaxing temperature of the printing is preferably 100-500℃.

[0095] When the diffusion source is applied by the coating method, the diffusion source, solvent and binder are mixed in a certain proportion to form a slurry.

[0096] The solvent is, for example, water, alcohol, ketone or ester.

[0097] In some preferred embodiments, the diffusion source is applied by the coating method, and the mass concentration of Dy in the diffusion source used in the non-easy demagnetization area is preferably 0.3%-1%; the mass concentration of Tb in the diffusion source used in the easy demagnetization 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 is preferably 0.3%-1%. The percentage is the mass percentage of Dy or Tb in the diffusion source.

[0098] In the present application, the heat treatment temperature in the grain boundary diffusion is preferably 750-950℃, for example, 900℃.

[0099] In the present application, the heat treatment time in the grain boundary diffusion is preferably 5-30h, for example, 10h.

[0100] In the present application, the heat treatment in the grain boundary diffusion is generally followed by aging treatment.

[0101] The aging treatment temperature is preferably 300-600℃, for example, 500℃.

[0102] The aging treatment time is preferably 1-10h, for example, 3h.

[0103] The present application also provides a use of the above-mentioned neodymium-iron-boron magnet in a magnetic steel.

[0104] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined in any manner to obtain preferred examples of the present application.

[0105] The reagents and raw materials used in the present application are commercially available.

[0106] The positive progress effect of the present application is that:

[0107] The present application can reduce the attenuation of the surface magnetic and magnetic flux of the Nd-Fe-B magnet, improve the anti-demagnetization ability of the Nd-Fe-B magnet, and match the characteristics of the easy demagnetization of the four corner parts and the difficult demagnetization of the center part of the magnetic steel in the actual application process, by setting the easy demagnetization area, the transition area and the non-easy demagnetization area, and controlling the diffusion weight gain ratio of Tb and Dy introduced by diffusion. BRIEF DESCRIPTION OF DRAWINGS

[0108] Fig. 1 is a structural schematic diagram of each area of the Nd-Fe-B magnet.

[0109] Fig. 2 is a structural schematic diagram of the main phase grain core and shell layer in each area of the Nd-Fe-B magnet.

[0110] Fig. 3 is a diffusion weight gain distribution 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.

[0111] Fig. 4 is a diffusion weight gain distribution 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.

[0112] Fig. 1 is a structural schematic diagram of each area of the Nd-Fe-B magnet. DETAILED DESCRIPTION

[0113] The present application will be further described below 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 commercial instructions.

[0114] Examples 1-3 and Comparative Examples 1-3

[0115] The diffusion source Dy is applied to the non-corner area of the upper surface and the lower surface of the Nd-Fe-B substrate, and the diffusion source Tb is applied to the part corresponding to the upper surface corner area on the four side surfaces perpendicular to the upper surface, so that the diffusion source Tb performs grain boundary diffusion perpendicular to the orientation direction, thereby obtaining the Nd-Fe-B magnet; wherein the utilization rate of Dy or Tb in the diffusion source is 85%-95%.

[0116] 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.

[0117] The parameters of each zone of the Nd-Fe-B magnets of Examples 1-3 and Comparative Examples 1-3 are listed in Table 1-2 below, and the element contents of the Nd-Fe-B substrates used in Examples 1-3 and Comparative Examples 1-3 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 1-3 and Comparative Examples 1-3 is equal to its content.

[0118] The structural schematic diagram of the Nd-Fe-B magnets of Examples 1-3 and Comparative Examples 1-3 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 2.5. 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 structure of the main phase grain core and the shell layer 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 the diffusion weight gain distribution diagram 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. It can be seen that along the test line 1, from the first easy demagnetization zone to the non-easy demagnetization zone, the distribution of Tb is close to a linear function distribution. Figure 4 is the diffusion weight gain distribution diagram 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.

[0119] Table 1 Diffusion weight gain of Dy and Tb of each zone of Examples 1-3 and Comparative Examples 1-3

[0120] Table 2 Coercive force ratio and width ratio of transition zone to Nd-Fe-B magnet of each zone of Examples 1-3 and Comparative Examples 1-3

[0121] Table 3 Mass concentration of each element in the substrate of Examples 1-3 and Comparative Examples 1-3

[0122] Effect Example 1

[0123] The Nd-Fe-B magnets of Examples 1-3 and Comparative Examples 1-3 were tested as follows:

[0124] 1. Coercive force test: The samples of Examples 1-3 and Comparative Examples 1-3 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 at room temperature (temperature ≤200℃) on a permanent magnet precision measurement system NIM-62000.

[0125] 2. demagnetization rate test: using electromagnetic simulation software, model Ansys Workbench, inputting rotating speed 1300rmp, then adjusting its temperature to corresponding temperature working condition, collecting motor back electromotive force data and observing magnetic steel cloud map change under same time, identifying whether demagnetization of magnetic steel occurs. Demagnetization rate calculation formula: demagnetization rate=(high-temperature back electromotive force-normal-temperature back electromotive force) / normal-temperature back electromotive force.

[0126] Technical effects of examples 1-3 and comparative examples 1-3 are listed in the following table 4:

[0127] Table 4 coercivity and demagnetization resistance of each zone in the magnet of examples 1-3 and comparative examples 1-3 ①The meaning of "easy demagnetization zone" in tables 1, 2 and 4 is the first easy demagnetization zone, the second easy demagnetization zone, the third easy demagnetization zone or the fourth easy demagnetization zone; ②The meaning of "transition zone" in the table is the first transition zone, the second transition zone, the third transition zone or the fourth transition zone.

[0128] From the above table, it can be seen that the remanence of the Nd-Fe-B magnet prepared by examples 1-3 is maintained at 14.31kGs and above, and the demagnetization rate at 130℃ is only 6.1% or less, which has excellent demagnetization resistance.

[0129] The easy demagnetization zone, transition zone and non-easy demagnetization zone of comparative example 1 all only use Dy diffusion, and the Tb diffusion weight gain is all 0. The demagnetization resistance of the Nd-Fe-B magnet prepared thereby is poor, and its demagnetization rate at 130℃ is 15.5%, which is higher than that of the examples.

[0130] The easy demagnetization zone, transition zone and non-easy demagnetization zone of comparative example 2 all only use Tb diffusion, and the Dy diffusion weight gain is all 0. The demagnetization resistance of the Nd-Fe-B magnet prepared thereby is poor, and its demagnetization rate at 130℃ is as high as 39.2%, which is much higher than that of the examples.

[0131] In comparative example 3, the Tb diffusion weight gain ratio of the non-easy demagnetization zone to the first easy demagnetization zone, the Dy diffusion weight gain ratio of the first easy demagnetization zone to the non-easy demagnetization zone, and the Tb diffusion weight gain ratio of the first transition zone to the first easy demagnetization zone are all not within the scope of the present application. The demagnetization resistance of the Nd-Fe-B magnet prepared thereby is poor, and its demagnetization rate at 130℃ is as high as 15%, which is much higher than that of the examples.

[0132] The above examples are only better examples of the present application, which are convenient for 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 examples without creative labor and apply them to other examples. Therefore, the present application is not limited to the above 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 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 heavy rare earth content of 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 heavy rare earth content of 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 and the first easy demagnetization area is (0-0.9):1; The content ratio of Dy in the first easy demagnetization area and the non-easy demagnetization area is (0-0.9):1; The content ratio of Tb in the first transition area and the first easy demagnetization area is (0.5-0.96):

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 and the first easy demagnetization area is (0-0.2):1, for example 0.08:1, 0.17:1 or 0.02:1; And / or, the diffusion weight gain ratio of Tb in the non-easy demagnetization area and the first easy demagnetization area is (0-0.05):(0.3-1), preferably (0-0.05):(0.3-0.6), for example 0.05:0.6, 0.05:0.3 or 0.01:0.6; And / or, the content ratio of Dy in the first easy demagnetization area and the non-easy demagnetization area is (0-0.8):1, for example 0.1:1; And / or, the diffusion weight gain ratio of Dy in the first easy demagnetization area and the non-easy demagnetization area is (0-0.05):(0.3-1), preferably (0-0.05):(0.3-0.5), for example 0.05:0.5; And / or, the content ratio of Tb in the first transition area and the first easy demagnetization area is (0.5-0.9):1, for example 0.8:1; And / or, the diffusion weight gain ratio of Tb in the first transition area and the first easy demagnetization area is (0.5-0.9):1, preferably (0.5-0.8):1, for example 0.8:

1.

3. The neodymium-iron-boron magnet of claim 1, wherein, The diffusion weight gain of Dy in the first easy demagnetization area is 0.05wt% and below, for example 0.05wt%; And / or, the content of Dy in the first easy demagnetization area is 0-3.1wt%, for example 0.05wt%; And / or, the diffusion weight gain of Dy in the first transition area is 0.05-0.9wt%, preferably 0.05-0.4wt%, for example 0.25wt%. and / or, the Dy content of the first transition zone is 0.05-3.9wt%, for example 0.25wt%; and / or, the Dy diffusion weight gain of the non-coercive zone is 0.1wt%-1wt%, preferably 0.4wt%-0.7wt%, for example 0.5wt%; and / or, the Dy content of the non-coercive zone is 0.1-4wt%, for example 0.5wt%; and / or, the Tb diffusion weight gain of the first coercive zone is 0.1wt%-1wt%, for example 0.6wt%; and / or, the Tb content of the first coercive zone is 0.1wt%-2.5wt%, for example 0.6wt%; and / or, the Tb diffusion weight gain of the non-coercive zone is 0.05wt% and below, for example 0.01wt%, 0.02wt% or 0.05wt%; and / or, the Tb content of the non-coercive zone is 0wt%-1.6wt%, for example 0.01wt%, 0.02wt% or 0.05wt%; and / or, the Tb diffusion weight gain of the first transition zone is 0.05-0.9wt%, preferably 0.2-0.5wt%, for example 0.35wt% or 0.48wt%; and / or, the Tb content of the first transition zone is 0.1wt%-2.4wt%, for example 0.35wt% or 0.48wt%; and / or, in any plane perpendicular to the orientation direction, the ratio of the Tb diffusion weight gain of the first coercive zone to the non-coercive zone is 1:(1 / L-1), where L is the distance between the sampling regions, and L>1.

4. The neodymium-iron-boron magnet of claim 1, wherein, The coercivity of the first coercive zone, the second coercive zone, the third coercive zone and the fourth coercive zone is the same; the coercivity of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone is the same; Preferably, the ratio of the coercivity of the non-coercive zone to the first coercive zone is (0.7-0.96):1, more preferably (0.8-0.9):1, for example 0.86:1, 0.88:1 or 0.90:1; Preferably, the difference of the coercivity of the first coercive zone and the non-coercive zone is 0-10kOe, more preferably 2-5kOe, for example 2.6kOe, 3.1kOe or 3.6kOe; Preferably, the ratio of the coercivity of the first transition zone to the first coercive zone is (0.8-0.98):1, for example 0.96:1; Preferably, the coercivity of the first coercive 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-coercive zone; The remanence of the first coercive zone, the second coercive zone, the third coercive zone and the fourth coercive zone is the same; the remanence of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone is the same; Preferably, the ratio of the remanence of the first coercive zone to the non-coercive zone is (0.99-1):1, for example 1:1; Preferably, the ratio of the remanence of the first transition zone to the non-coercive zone is (0.99-1):1, for example 1:

1.

5. The neodymium-iron-boron magnet of claim 1, wherein, In any plane perpendicular to the orientation direction, the shape of the first, second, third and fourth easy demagnetization regions 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 the easy demagnetization region refers to the distance extending along the X-axis or Y-axis from the edge of the Nd-Fe-B magnet; And / or, 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 of the first transition region and the first easy demagnetization region and the interface of the first transition region and the non-easy demagnetization region along the X-axis or Y-axis direction; And / or, 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; And / or, 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; the width of the non-easy demagnetization region refers to the distance extending along the X-axis or Y-axis from the interface of the transition region and the non-easy demagnetization region or the edge of the Nd-Fe-B magnet; And / or, 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 and is not 0, for example, 0.08:1; And / or, the width of the first transition region is 0-1 mm and is not 0; And / or, the ratio of the length to the thickness of the Nd-Fe-B magnet is <3, preferably, the thickness of the Nd-Fe-B magnet is 0.5-5 mm; 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 along the positive direction of the Z-axis from the upper surface; And / or, the thickness of the Nd-Fe-B magnet is >5 mm, the thickness refers to the extension distance of the cuboid along the positive direction of the Z-axis from the upper surface.

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; In the first, second, third and fourth easy demagnetization regions, the thickness of the shell layer of the main phase grains is the same; in the first, second, third and fourth transition regions, the thickness of the shell layer of the main phase grains is the same; In the first, second, third and fourth easy demagnetization regions, the thickness of the Re-rich phase grain boundary is the same; in the first, second, third and fourth transition regions, the thickness of the Re-rich phase grain boundary is the same; In the first easy demagnetization region, the first transition region and the non-easy demagnetization region, the thickness of the shell layer of the main phase grains is preferably 0-4 μm, more preferably 0-2 μm; In the first easy demagnetization region, the first transition region and the non-easy demagnetization region, the thickness of the Re-rich phase grain boundary is preferably 0-1 μm, but not 0; In the first easy demagnetization region, the first transition region and the non-easy demagnetization region, the ratio of the thickness of the shell layer of the main phase grains to the thickness of the Re-rich phase grain boundary 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 grains in the first, second, third and fourth easy demagnetization regions is the same; And / or, the grain size of the main phase grains of the first transition zone, the second transition zone, the third transition zone and the fourth transition zone is the same; And / or, the grain size ratio of the main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone is 1:1:1; And / or, the grain size of the surface layer main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone is the same, preferably 1-12 μm; And / or, the grain size of the center main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone is the same, preferably 1-12 μm; And / or, the grain size of the surface layer main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone is 1-1.5 times of the grain size of the center main phase grains; And / or, 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; R2 is Dy and / or Tb; And / or, the content of R2 in the shell layer of the main phase grains of the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone satisfies the following conditions: When the R2 is Tb, the first easy demagnetization zone≥the first transition zone>the non-easy demagnetization zone; When the R2 is Dy, the non-easy demagnetization zone≥the first transition zone>the first easy demagnetization 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 Dy on the non-quadrangular area of the upper surface and the lower surface of the neodymium iron boron substrate, and applying diffusion source Tb on the part corresponding to the quadrangular area of the upper surface on the four side surfaces perpendicular to the upper surface, so that the diffusion source Tb performs grain boundary diffusion perpendicular to the orientation direction, thereby obtaining the neodymium iron boron magnet; wherein the quadrangular area forms the easy demagnetization zone through grain boundary diffusion; and the non-quadrangular area forms the non-easy demagnetization zone and the transition zone.

9. The method of producing a neodymium-iron-boron magnet according to claim 8, characterized by, The application mode of the diffusion source is coating; Preferably, the coating mode is spraying or printing; the dewaxing temperature of the spraying is preferably 200-400 ℃; the dewaxing temperature of the printing is preferably 100-500 ℃; And / or, the heat treatment temperature in the grain boundary diffusion is 750-950 ℃, for example, 900 ℃; And / or, the heat treatment time in the grain boundary diffusion is 5-30 h, for example, 10 h; And / or, the grain boundary diffusion is generally followed by aging treatment; Preferably, the aging treatment temperature is 300-600 ℃, for example, 500 ℃; Preferably, the aging treatment time is 1-10 h, for example, 3 h.

10. The application of the neodymium iron boron magnet according to any one of claims 1-7 in a magnetic steel.

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