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

Abstract

The present invention relates to a neodymium-iron-boron magnet, a preparation method therefor, and a use thereof. The neodymium-iron-boron magnet comprises a non-demagnetization-prone region, a transition region, and a demagnetization-prone region. The method for preparing a neodymium-iron-boron magnet comprises the following steps: on a neodymium-iron-boron substrate, separately applying a diffusion source to an upper surface and / or a lower surface perpendicular to a Z-axis direction, and performing grain boundary diffusion parallel to an orientation direction, a diffusion source Dy being applied to all regions of the upper surface and the lower surface, and a diffusion source Tb being applied to an outer edge annular region along the Z-axis direction, so as to form the demagnetization-prone region, the transition region, and the non-demagnetization-prone region. The neodymium-iron-boron magnet of the present invention can reduce attenuation of the surface magnetism and magnetic flux of the neodymium-iron-boron magnet while ensuring remanence, and has good anti-demagnetization performance.

Description

Neodymium iron boron magnets, their preparation methods and applications Technical Field

[0001] This invention relates to a neodymium iron boron magnet, its preparation method, and its application. Background Technology

[0002] Since its invention, neodymium iron boron (NdFeB) permanent magnet materials have been widely used in automobiles, wind power, home appliances, industrial robots, and other fields. Due to the different operating conditions in each field, the performance requirements for the magnets in these products also vary. In recent years, the booming development of new energy vehicles has led to a sharp increase in the demand for magnets in main drive motors. Since the normal operating temperature of main drive motors is mainly concentrated in the 120-180℃ range, NdFeB magnets require higher coercivity and thermal stability. To improve the temperature resistance of rare earth permanent magnets, large amounts of heavy rare earth elements (Dy and Tb) are typically added to increase the anisotropic field of the main phase magnetocrystalline structure. However, the scarcity and high price of heavy rare earth resources severely restrict the application of NdFeB magnets in various industries.

[0003] With the increasing demand for high-performance magnets, grain boundary diffusion technology is gradually becoming more widely known and accepted. Conventional grain boundary diffusion technology uses a physical vapor deposition method to deposit the diffusion source onto the magnet surface, then uses high temperature and pressure to allow the diffusion source to penetrate along the grain boundaries into the magnet's interior. The biggest advantage of this technology is that it significantly improves coercivity while maintaining almost no change in remanence using only a small amount of heavy rare earth elements. In terms of the effective utilization rate of heavy rare earth elements, traditional grain boundary diffusion products offer a substantial improvement over non-grain boundary diffusion products.

[0004] However, in the actual use of NdFeB magnets, the performance requirements for each part of the magnet are not the same. For example, in motors, the reverse magnetic field generated after the coil is energized is not a uniform magnetic field. Therefore, it is important to design a NdFeB magnet that meets the needs of different applications, ensuring coercivity and remanence while also having good anti-demagnetization ability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a neodymium iron boron magnet, its preparation method, and its applications. The neodymium iron boron magnet of this invention can reduce the attenuation of surface magnetism and magnetic flux while maintaining remanence, and exhibits good anti-demagnetization properties.

[0006] In a first aspect, the present invention provides a neodymium iron boron magnet, which establishes a three-dimensional rectangular coordinate system with the orientation direction as the Z-axis direction, and the origin of the three-dimensional rectangular coordinate system is located inside the neodymium iron boron magnet;

[0007] The neodymium iron boron magnet includes a non-demagnetizing region, a transition region, and a demagnetizing region; the demagnetizing region is an outer annular region located on the neodymium iron boron magnet along the Z-axis direction, the non-demagnetizing region is a central region located on the neodymium iron boron magnet along the Z-axis direction, and the transition region is the boundary region located between the demagnetizing region and the non-demagnetizing region;

[0008] The Tb content ratio of the non-demagnetizing region, the transition region, and the demagnetizing region is (0-0.05):(0.95-1):1;

[0009] The content ratio of Dy in the non-demagnetizing region, the transition region, and the demagnetizing region is 1:1:1.

[0010] In this invention, the central axis of the "outer annular region along the Z-axis" is parallel to the Z-axis.

[0011] Regarding parameters

[0012] In this invention, preferably, the content of heavy rare earth elements is the same at each location in the easily demagnetized region.

[0013] In this invention, preferably, the diffusion increment of heavy rare earth elements at the same XY position along the Z-axis in the transition region is the same. Preferably, the diffusion content of Tb decreases along the X-axis or Y-axis in the transition region away from the easily demagnetized region.

[0014] In this invention, preferably, the Tb content is the same at any two XY positions in the easily demagnetized region.

[0015] In this invention, preferably, the content of Dy is the same at any two locations in the easily demagnetized region, the transition region, and the non-easily demagnetized region.

[0016] In this invention, the diffusion increment of heavy rare earth elements (Tb) refers to the percentage of the mass of Tb introduced into a region by diffusion relative to the total mass of the magnet in that region. Specifically, the diffusion increment of Tb refers to the percentage of the mass of Tb introduced into a region by diffusion relative to the total mass of the magnet in that region; the diffusion increment of Dy refers to the percentage of the mass of Dy introduced into a region by diffusion relative to the total mass of the magnet in that region.

[0017] In this invention, "the same diffusion increment of heavy rare earth elements" means that the types of heavy rare earth elements introduced by diffusion are the same at all locations in a certain region, and the diffusion increment of each type of heavy rare earth element is the same. Specifically, the same diffusion increment of Tb means that the diffusion increment of Tb introduced by diffusion is the same; the same diffusion increment of Dy means that the diffusion increment of Dy introduced by diffusion is the same.

[0018] In this invention, the Tb content ratio of the transition region to the easily demagnetized region can be 0.8:1 or 0.9:1.

[0019] In this invention, the Tb content ratio of the transition region to the non-demagnetizing region can be 1:(0-0.1), preferably 1:(0-0.05).

[0020] In this invention, the Tb content ratio of the non-demagnetizing region to the demagnetizing region can be (0-0.9):1, for example, 0.1:1, 0.2:1 or 0.7:1.

[0021] In this invention, the ratio of the diffusion increment of Tb in the easily demagnetized region to the diffusion increment of Tb in the non-easily demagnetized region can be (1-100):1, for example 9:1, 36:1 or 55:1.

[0022] In this invention, the ratio of the diffusion increment of Tb in the easily demagnetized region to the diffusion increment of Tb in the transition region can be (1-1.1):1, for example 1:1, 36:34 or 55:52.

[0023] In this invention, the diffusion increment of Tb in the easily demagnetized region can be 0.1wt%-1wt%, for example 0.35wt%, 0.36wt%, 0.45wt% or 0.55wt%.

[0024] In this invention, the diffusion increment of Tb in the non-demagnetizing region can be 0-0.1wt%, preferably 0-0.05wt%, for example 0, 0.01wt%, or 0.05wt%.

[0025] In this invention, the diffusion increment of Tb in the transition region can be 0.1wt%-1wt%, for example 0.34wt%, 0.45wt%, or 0.52wt%.

[0026] In this invention, the diffusion increment of Dy in the easily demagnetized region can be 0.1wt%-1wt%, for example, 0.55wt%.

[0027] In this invention, the diffusion increment of Dy in the non-demagnetizing region can be 0.1wt%-1wt%, preferably 0.4wt%-0.7wt%, for example 0.55wt%.

[0028] In this invention, the diffusion increment of Dy in the transition region can be 0.1wt%-1wt%, for example 0.55wt%.

[0029] In this invention, there is an interface A between the transition region and the easily demagnetized region, and the content of heavy rare earth elements is the same at each position of the interface A.

[0030] The diffusion increment of Tb at interface A can be 0.3wt%-0.7wt%, for example 0.36wt%, 0.45wt%, or 0.55wt%.

[0031] Preferably, the diffusion increment ratio of the interface A to the Tb of the easily demagnetized region is (0.95-1):1.

[0032] The diffusion increment of Dy at interface A can be 0.4wt%-0.7wt%, for example, 0.55wt%.

[0033] In this invention, there is an interface B between the transition region and the non-demagnetizing region, and the content of heavy rare earth elements is the same at each position of the interface B.

[0034] The diffusion increment of Tb at the interface B can be 0.3wt%-0.7wt%, for example 0.34wt%, 0.43wt%, or 0.52wt%.

[0035] The diffusion increment ratio of the interface B to the Tb of the non-demagnetizing region is preferably (6-60):1, for example 43:5, 34:1 or 52:1.

[0036] The diffusion increment of Dy at interface B can be 0.4wt%-0.7wt%, for example, 0.55wt%.

[0037] In this invention, the coercivity ratio of the easily demagnetized region to the non-easily demagnetized region can be 1:(0.7-0.96), for example 1:0.876, 1:0.909 or 1:0.957.

[0038] In this invention, the coercivity ratio between the easily demagnetized region and the transition region can be 1:(0.93-1), for example 1:0.930, 1:0.959 or 1:0.970.

[0039] In this invention, the coercivity at each location of the easily demagnetized region can be the same.

[0040] In this invention, the coercivity at all positions along the Z-axis of the transition region can be the same. Preferably, the coercivity in the transition region decreases along the X-axis or Y-axis and away from the easily demagnetized region.

[0041] In this invention, the residual magnetism at each location in the easily demagnetized region can be the same.

[0042] In this invention, the residual magnetism at various positions along the Z-axis of the transition region can be the same. Preferably, the residual magnetism in the transition region decreases along the X-axis or Y-axis and away from the easily demagnetized region.

[0043] Regarding composition

[0044] In this invention, the neodymium iron boron magnet can be represented by the chemical formula R1-R2-TBM, wherein R1 can be one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 can be Dy and / or Tb; T can be one or more of Fe, Zn, Si, V, Cr, Mn, Ni, Ge, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F and P; and M can be one or more of Cu, Al, Co, Ga, Zr and Ti.

[0045] In some embodiments of the present invention, the M element is entirely derived from a NdFeB substrate.

[0046] In some embodiments of the invention, the M element comprises a diffusion-introduced M element, wherein the diffusion-introduced M element preferably accounts for 0-0.4% of the mass percentage of the NdFeB magnet.

[0047] In some embodiments of the present invention, the microstructure of the neodymium iron boron magnet includes Re2Fe 14 B-phase grains and Re-rich phase grain boundaries; the Re2Fe 14 The B-phase grains comprise a core and a shell; Re is one or more of Nd, Dy, and Tb.

[0048] Re2Fe 14 [B main phase grains]

[0049] Among them, the Re2Fe in the easily demagnetized region 14 The difference in grain size between the B main phase grains can not exceed 8 μm.

[0050] Wherein, the Re2Fe in the transition region 14 The difference in grain size between the B main phase grains can not exceed 8 μm.

[0051] Among them, the Re2Fe on the surface of the easily demagnetized region, the transition region and the non-easily demagnetized region. 14 The grain size of the B main phase can be equal, and the surface layer refers to the surface perpendicular to the orientation direction.

[0052] Among them, the Re2Fe at the center of the easily demagnetized region, the transition region, and the non-easily demagnetized region. 14 The grain size of the B main phase can be equal, where the center refers to the mid-plane along the orientation direction.

[0053] In certain specific embodiments of the present invention, in the easily demagnetized region, the transition region, and the non-easily demagnetized region, the surface Re2Fe 14The grain size of the B main phase is preferably 1 to 1.5 times the grain size of the central main phase grain.

[0054] In a specific embodiment of the present invention, the easily demagnetized region, the transition region, and the non-easily demagnetized region are on the same XY plane, and the Re2Fe... 14 The grain size ratio of the B main phase is 1:1:1.

[0055] In certain specific embodiments of the present invention, the Re2Fe on the surface of the easily demagnetized region, the transition region, and the non-easily demagnetized region is... 14 The grain size of the B main phase is preferably 1-12 μm.

[0056] In the above text, the grain size refers to the average grain size of all grains in a certain region. For example, Re2Fe in the easily demagnetized region. 14 The grain size of the B-phase main grains signifies the size of all Re2Fe grains in the easily demagnetized region. 14 The average grain size of the B main phase grains.

[0057] Re-rich grain boundaries

[0058] In this invention, the meaning of the Re-rich phase grain boundary is the conventional meaning in the art, that is, a two-particle grain boundary region with Re > 95%.

[0059] The thickness of the Re-rich phase grain boundaries in the easily demagnetized region can be equal, that is, the thickness of the Re-rich phase grain boundaries in each region of the easily demagnetized region remains unchanged.

[0060] The thickness of the Re-rich phase grain boundaries in the transition region can be equal, meaning that the thickness of the Re-rich phase grain boundaries in each region of the transition region remains unchanged.

[0061] In some specific embodiments of the present invention, the thickness of the Re-rich phase grain boundary of the easily demagnetized region is 0.4-1 μm, for example 0.5 μm or 0.55 μm.

[0062] In some specific embodiments of the present invention, the thickness of the Re-rich phase grain boundary in the transition region is 0.4-1 μm, for example 0.5 μm or 0.52 μm.

[0063] In certain specific embodiments of the present invention, the thickness of the Re-rich phase grain boundary in the non-demagnetizing region is 0.2-0.5 μm, for example 0.20 μm, 0.23 μm or 0.25 μm.

[0064] Core and shell

[0065] In some embodiments of the present invention, the shell is Re2Fe, which is conventional in the art. 14 B. Hard magnetic layer.

[0066] In some embodiments of the present invention, the shell of the easily demagnetized region is (Nd,Dy,Tb)2Fe. 14 B. Hard magnetic layer.

[0067] In some embodiments of the present invention, the shell of the non-demagnetizing region is (Nd,Dy)2Fe. 14 B. Hard magnetic layer.

[0068] The core and shell layers in the easily demagnetized region, the transition region, and the non-easily demagnetized region can each independently satisfy the following conditions: the R1 content in the core layer is not less than the R1 content in the shell layer; the R2 content in the core layer is less than the R2 content in the shell layer.

[0069] Wherein, R2 is Tb, and the content of R2 in the easily demagnetized region, the transition region and the non-easily demagnetized region can satisfy the following condition: easily demagnetized region ≥ transition region > non-easily demagnetized region.

[0070] Wherein, R2 is Dy, and the content of R2 in the easily demagnetized region, the transition region and the non-easily demagnetized region can satisfy the following condition: non-easily demagnetized region = transition region = easily demagnetized region.

[0071] The thickness of the shell layer in the easily demagnetized region can be equal, that is, the thickness of the shell layer in each region of the easily demagnetized region remains unchanged.

[0072] The thickness of the shell in the transition region can be equal, meaning that the thickness of the shell in each region of the transition region remains unchanged.

[0073] In some specific embodiments of the present invention, the thickness of the shell layer of the easily demagnetized region is 2-3 μm, for example 2 μm, 2.1 μm or 2.5 μm.

[0074] In some specific embodiments of the present invention, the shell thickness of the main phase grains in the transition region is 2-2.5 μm, for example 2 μm or 2.38 μm.

[0075] In some specific embodiments of the present invention, the shell thickness of the main phase grains in the non-demagnetizing region is 0.5-2 μm, for example 0.95 μm, 1.0 μm or 1.1 μm.

[0076] In certain specific embodiments of the present invention, the thickness of the shell layer and the Re-rich phase grain boundary of the easily demagnetized region is preferably (2-3):(0.4-1), for example 4:1, 2.1:0.5 or 2.5:0.55.

[0077] In certain embodiments of the present invention, the thickness of the shell and the Re-rich phase grain boundary of the transition region is preferably (2-2.5):(0.4-1), for example 4:1 or 2.38:0.52.

[0078] In certain specific embodiments of the present invention, the thickness of the shell layer of the main phase grains and the Re-rich phase grain boundary in the non-demagnetizing region is preferably (0.5-2):(0.2-0.5), for example 1.1:0.25, 1.0:0.23 or 0.95:0.20.

[0079] Regarding structure

[0080] In this invention, the neodymium iron boron magnet can be a cuboid. The origin can be located at the center of the upper surface of the cuboid. The X-axis of the three-dimensional rectangular coordinate system can be parallel to one side of the upper surface.

[0081] In this invention, the specific location of the upper surface is not specifically limited. Those skilled in the art will generally understand that the upper surface refers to the surface opposite to a plane when the magnet is placed on a plane.

[0082] The length-to-width ratio of the neodymium iron boron magnet is (2-5):1, preferably (2.42-3.7):1, for example 3:1, 3.65:1 or 39:10.7. The length refers to the distance of one side of the upper surface extending along the positive X-axis; the width refers to the distance of the cuboid extending from the upper surface along the positive Y-axis.

[0083] In this invention, the width of the easily demagnetized region can be equal, that is, the distance the easily demagnetized region extends from the edge of the NdFeB magnet along the X-axis or Y-axis remains unchanged.

[0084] Preferably, the width of the easily demagnetized area is no more than 5 mm, for example, 2-4 mm.

[0085] In this invention, the shape of the non-demagnetizing region can be elliptical on any plane perpendicular to the orientation direction.

[0086] The ratio of the major axis a to the minor axis b of the non-demagnetizing region can be (2-15):1, for example, 17.5:3.35.

[0087] In this invention, the width of the transition zone can be equal, that is, the distance the transition zone extends from the edge of the NdFeB magnet along the X-axis or Y-axis remains unchanged.

[0088] Preferably, the width of the transition zone is 0-2mm, not 0, for example 0.5mm.

[0089] In this invention, the volume of the easily demagnetized region accounts for 40%-90% of the volume of the neodymium iron boron magnet, for example, 47.85%.

[0090] In this invention, the volume of the transition region accounts for 0-28.4% of the volume of the neodymium iron boron magnet, for example, 8.04%.

[0091] In this invention, the volume of the non-demagnetizing region accounts for 15.7%-44.11% of the volume of the neodymium iron boron magnet.

[0092] In this invention, the non-demagnetizing region, transition region, and demagnetizing region can be obtained by simulating cloud maps under operating conditions.

[0093] In this invention, the thickness of the neodymium iron boron magnet may not exceed 5 mm, for example, it may be 3 mm.

[0094] Secondly, the present invention also provides a method for preparing a neodymium iron boron magnet, comprising the following steps: applying diffusion sources to the upper surface and / or lower surface perpendicular to the Z-axis direction on a neodymium iron boron substrate to perform grain boundary diffusion parallel to the orientation direction; wherein, diffusion source Dy is applied to the entire area of ​​the upper and lower surfaces, and diffusion source Tb is applied to the outer annular region along the Z-axis direction to form the easily demagnetized region, the transition region, and the non-easily demagnetized region.

[0095] As is known to those skilled in the art in this invention, during grain boundary diffusion, the Dy or Tb in the diffusion source does not completely diffuse into the magnet, and its utilization rate is generally 85%-95%. Therefore, in the actual preparation process, a larger amount of Dy or Tb is usually applied.

[0096] 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.

[0097] In this invention, the diffusion source can be applied using methods conventional in the art, such as coating.

[0098] The coating method is preferably spraying or printing. The dewaxing temperature for spraying can be 200-400℃. The dewaxing temperature for printing can be 100-500℃.

[0099] In this invention, when the diffusion source is applied by coating, it is generally mixed with a solvent and a binder in a certain proportion to form a slurry. The solvent can be water, alcohol, ketone, or ester. The mass percentage of Dy or Tb in the diffusion source in the slurry can be 0.3%-1%.

[0100] In this invention, the diffusion source Dy can be elemental Dy.

[0101] In this invention, the diffusion source Dy can be a Dy-M alloy, and M can be one or more of Cu, Al, Co, Ga, Zr, and Ti. The mass percentage of M in the Dy-M alloy may not exceed 40%.

[0102] In this invention, the diffusion source Dy can be a hydride of Dy or a fluoride of Dy.

[0103] In this invention, the diffusion source Tb can be elemental Tb.

[0104] In this invention, the diffusion source Tb can be a Tb-M alloy, and M can be one or more of Cu, Al, Co, Ga, Zr, and Ti. The mass percentage of M in the Tb-M alloy may not exceed 40%.

[0105] In this invention, the diffusion source Tb can be a hydride of Tb or a fluoride of Tb.

[0106] In this invention, the temperature for grain boundary diffusion can be 750-950℃, for example, 900℃.

[0107] In this invention, the time for grain boundary diffusion can be 5-30 hours, for example, 10 hours.

[0108] In this invention, aging treatment may also be included after the grain boundary diffusion.

[0109] The aging treatment temperature can be 300-600℃, for example, 500℃.

[0110] The time for the time-sensitive processing can be 1-10 hours, for example, 3 hours.

[0111] Thirdly, the present invention also provides a neodymium iron boron magnet prepared by the method described above.

[0112] Fourthly, the present invention also provides an application of the neodymium iron boron magnet as described above in magnetic steel.

[0113] Without violating common sense in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0114] The reagents and raw materials used in this invention are all commercially available.

[0115] The positive and progressive effects of this invention are as follows:

[0116] The neodymium iron boron (NdFeB) magnet of this invention includes a transition region. By controlling the Tb and Dy contents introduced by diffusion in the transition region, the easily demagnetized region, and the non-easily demagnetized region, the interdiffusion of Tb or Dy across regions caused by the Tb concentration gradient difference in the transition region can be reduced. This reduces the gradient decrease in the performance of the boundary region and weakens the anti-demagnetization effect. While maintaining the remanence of the NdFeB magnet, the attenuation of the surface magnetism and magnetic flux of the NdFeB magnet is reduced, thus improving the anti-demagnetization capability of the NdFeB magnet. Furthermore, this invention sets the easily demagnetized region, the non-easily demagnetized region, and the transition region as an inner ellipse and an outer square, which can improve the anti-demagnetization capability of the four long sides of the NdFeB magnet. Attached Figure Description

[0117] Figure 1 is a schematic diagram of the structure of each region of the neodymium iron boron magnet of the present invention;

[0118] Figure 2 is a schematic diagram of the coercivity of the neodymium iron boron magnet in Example 3 along test line 1 to test line 4 shown in Figure 1.

[0119] Figure 3 is a schematic diagram of the diffusion increment of Tb of the neodymium iron boron magnet in Example 3 along test line 1 to test line 4 shown in Figure 1. Detailed Implementation

[0120] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0121] Examples 1-3 and Comparative Examples 1-2

[0122] On the upper and lower surfaces of the neodymium iron boron substrate along the Z-axis, Dy is sprayed over the entire area of ​​both surfaces, and Tb is sprayed over the outer annular area along the Z-axis. The dewaxing temperature of the spraying is 200°C, and grain boundary diffusion parallel to the orientation direction is carried out to obtain the neodymium iron boron magnet, as shown in Figure 1. The utilization rate of Dy or Tb in the diffusion source is 85%-95%.

[0123] The heat treatment during grain boundary diffusion is carried out at a temperature of 900℃ for 10 hours. After the heat treatment, an aging treatment is also included, which is carried out at a temperature of 500℃ for 3 hours.

[0124] The parameters of each region of the NdFeB magnets in Examples 1-3 and Comparative Examples 1-2 are listed in Tables 1-3 below. The Tb content variation of the NdFeB magnet in Example 3 along test lines 1 to 4 shown in Figure 1 is shown in Figure 3. Test line 1 is parallel to the X-axis and passes through the easily demagnetized region, the transition region, and the non-easily demagnetized region, overlapping with the long axis of the non-easily demagnetized region. Test line 2 is parallel to the X-axis and passes through the easily demagnetized region, the transition region, and the non-easily demagnetized region. Test line 3 is parallel to the X-axis and passes through the easily demagnetized region and the transition region. Test line 4 is parallel to the X-axis and passes through the easily demagnetized region. The elemental contents of the NdFeB substrates used in Examples 1-3 and Comparative Examples 1-2 are shown in Table 4.

[0125] The NdFeB magnets in Examples 1-3 and Comparative Examples 1-2 have a thickness of 3 mm. The main phase grains in the easily demagnetized region and transition region both contain an inner shell and an outer shell, while the main phase grains in the non-easily demagnetized region only contain an inner shell. The grain size and shell structure of the main phase and Re phase in each region of the NdFeB magnets in Examples 1-3 and Comparative Examples 1-2 are shown in Tables 5-6.

[0126] Table 1. Diffusion increments of Dy and Tb in different regions of the NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-2.

[0127] Table 2. Diffusion increments of Dy and Tb at the interface of NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-2.

[0128] Table 3. Size ratios of different regions of the NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-2

[0129] Table 4. Mass concentration (wt%) of each element in the NdFeB substrates of Examples 1-3 and Comparative Examples 1-2

[0130] Table 5. Grain size and shell structure of the main phase and Re phase in each region of NdFeB in Examples 1-3 and Comparative Examples 1-2.

[0131] Table 6. Main phase particle size and shell structure of NdFeB in different regions of Examples 1-3 and Comparative Examples 1-2.

[0132] Effect Example

[0133] I. Test objects: Neodymium iron boron magnets of Examples 1-3 and Comparative Examples 1-2;

[0134] II. Testing Methods:

[0135] 1. Coercivity test: Samples of Examples 1-3 and Comparative Examples 1-2 were prepared with a sample size of W2~3±0.1*L19±0.1*T4±0.1mm. Two samples were stacked and tested at room temperature (temperature ≤200℃) using a coil with a size of W3*L19~20*T2.7mm on a permanent magnet precision measurement system NIM-62000.

[0136] 2. Demagnetization Rate Test: Using electromagnetic simulation software, Ansys Workbench, with an input speed of 13000 rpm, the motor temperature was adjusted to the corresponding operating condition. Back EMF data of the motor was collected over the same time period, and changes in the magnet contour plot were observed to determine whether demagnetization had occurred. The formula for calculating the demagnetization rate is: Demagnetization Rate = (High-Temperature Back EMF - Room-Temperature Back EMF) / Room-Temperature Back EMF.

[0137] 3. Line scan test: The selected area of ​​the magnet surface was photographed under the EMMA equipment. The equipment model was JEOL 8530f and the magnification was X3000. Line scan was performed on the two main phases to characterize the distribution of elements such as Dy / Nd.

[0138] III. Test Results: Listed in Tables 7-8 below:

[0139] Table 7. Coercivity and demagnetization resistance of different regions in the magnets of Examples 1-3 and Comparative Examples 1-2.

[0140] Table 8. Coercivity ratios of different regions in the magnets of Examples 1-3 and Comparative Examples 1-2.

[0141] As shown in the table above, the demagnetization rate of the NdFeB magnets in Examples 1-3 at 130℃ is only 2.0%-5.2%. The coercivity ratio between the transition region and the easily demagnetized region of the NdFeB magnets prepared in Examples 1-3 is between (0.93-0.97):1, and the difference in coercivity between the easily demagnetized region and the non-easily demagnetized region is between 0.75-1.67 kOe, exhibiting excellent anti-demagnetization ability. The coercivity variation of the NdFeB magnet in Example 3 along test line 1 to test line 4 shown in Figure 1 is shown in Figure 2.

[0142] The Tb diffusion increment in the easily demagnetized region of Comparative Example 1 is too low, with a ratio of 3:11 to the Dy increment in the non-easily demagnetized region. The coercivity ratio between the easily demagnetized region and the non-easily demagnetized region of the NdFeB magnet in Comparative Example 1 is approximately 1:0.936, and the difference in coercivity between the easily demagnetized region and the non-easily demagnetized region is 1.5 kOe. The NdFeB magnet prepared in Comparative Example 1 has poor demagnetization resistance, with a demagnetization rate of 20.2% at 130°C, which is higher than that of Examples 1-3.

[0143] The diffusion increment of Dy in the non-demagnetizing region of Comparative Example 2 was too low; while the diffusion increment of Tb in the demagnetizing region was slightly higher (specifically 1 wt%); the diffusion increment of Tb in the transition region was too low, with a ratio of 1:5 to the diffusion increment of Tb in the demagnetizing region; the diffusion increment of Dy in both the transition region and the non-demagnetizing region was ≤0.1 wt%, and the coercivity ratio of the non-demagnetizing region to the demagnetizing region of the neodymium iron boron magnet prepared therefrom was 0.668:1, and the difference in coercivity between the demagnetizing region and the non-demagnetizing region was 8.7 kOe. The demagnetization resistance of the neodymium iron boron magnet prepared in Comparative Example 2 was poor, and its demagnetization rate at 130°C was as high as 19.6%, which was much higher than that of Examples 1-3. The coercivity of the transition region and the non-demagnetizing region was lower than that of the demagnetization under this condition.

[0144] The embodiments described above are merely preferred embodiments of the present invention, enabling those skilled in the art to understand and use the invention. Obviously, anyone skilled in the art can make slight modifications or variations to these embodiments without creative effort and apply them to other embodiments. Therefore, the present invention is not limited to the above embodiments, and any equivalent changes, simple modifications, and alterations made within the scope of the present invention still fall within its coverage.

Claims

1. A neodymium iron boron magnet, characterized in that, A three-dimensional rectangular coordinate system is established, with the orientation direction as the Z-axis direction, and the origin of the three-dimensional rectangular coordinate system is located inside the neodymium iron boron magnet; The neodymium iron boron magnet includes a non-demagnetizing region, a transition region, and a demagnetizing region; the demagnetizing region is an outer annular region located on the neodymium iron boron magnet along the Z-axis direction, the non-demagnetizing region is a central region located on the neodymium iron boron magnet along the Z-axis direction, and the transition region is the boundary region located between the demagnetizing region and the non-demagnetizing region; The Tb content ratio of the non-demagnetizing region, the transition region, and the demagnetizing region is (0-0.05):(0.95-1):1; The content ratio of Dy in the non-demagnetizing region, the transition region, and the demagnetizing region is 1:1:

1.

2. The neodymium iron boron magnet according to claim 1, characterized in that, The content of heavy rare earth elements is the same at all locations in the easily demagnetized region; And / or, the diffusion increment of heavy rare earth elements at the same XY position along the Z-axis in the transition region is the same; preferably, the diffusion content of Tb in the transition region decreases along the X-axis or Y-axis and away from the easily demagnetized region. And / or, the content of Tb at any two XY positions in the easily demagnetized region is the same; And / or, the content of Dy at any two locations in the easily demagnetized region, transition region, and non-easily demagnetized region is the same; And / or, the Tb content ratio of the transition region to the easily demagnetized region is 0.8:1 or 0.9:1; And / or, the Tb content ratio of the transition region to the non-demagnetizing region is 1:(0-0.1), preferably 1:(0-0.05); And / or, the Tb content ratio of the non-demagnetizing region to the demagnetizing region is (0-0.9):1, for example 0.1:1, 0.2:1 or 0.7:1; And / or, the ratio of the diffusion increment of Tb in the easily demagnetized region to the diffusion increment of Tb in the non-easily demagnetized region is (1-100):1, for example 9:1, 36:1 or 55:1; And / or, the ratio of the diffusion increment of Tb in the easily demagnetized region to the diffusion increment of Tb in the transition region is (1-1.1):1, for example 1:1, 36:34 or 55:52; And / or, the diffusion increment of Tb in the easily demagnetized region is 0.1wt%-1wt%, for example 0.35wt%, 0.36wt%, 0.45wt% or 0.55wt%; And / or, the diffusion increment of Tb in the non-demagnetizing region is 0-0.1wt%, preferably 0-0.05wt%, for example 0, 0.01wt% or 0.05wt%; And / or, the diffusion increment of Tb in the transition region is 0.1wt%-1wt%, for example 0.34wt%, 0.45wt%, or 0.52wt%; And / or, the diffusion increment of Dy in the easily demagnetized region is 0.1wt%-1wt%, for example 0.55wt%; And / or, the diffusion increment of Dy in the non-demagnetizing region is 0.1wt%-1wt%, preferably 0.4wt%-0.7wt%, for example 0.55wt%; And / or, the diffusion increment of Dy in the transition region is 0.1wt%-1wt%, for example 0.55wt%; And / or, an interface A exists between the transition region and the easily demagnetized region, and the content of heavy rare earth elements is the same at all locations of the interface A; the diffusion increment of Tb at the interface A is preferably 0.3wt%-0.7wt%, for example 0.36wt%, 0.45wt%, or 0.55wt%; the diffusion increment ratio of Tb at the interface A to that at the easily demagnetized region is preferably (0.95-1):1; the diffusion increment of Dy at the interface A is preferably 0.4wt%-0.7wt%, for example 0.55wt%. And / or, an interface B exists between the transition region and the non-demagnetizing region, wherein the content of heavy rare earth elements is the same at all locations of the interface B; the diffusion increment of Tb at the interface B is preferably 0.3wt%-0.7wt%, for example 0.34wt%, 0.43wt%, or 0.52wt%; the diffusion increment ratio of Tb between the interface B and the non-demagnetizing region is preferably (6-60):1, for example 43:5, 34:1, or 52:1; the diffusion increment of Dy at the interface B is preferably 0.4wt%-0.7wt%, for example 0.55wt%. And / or, the coercivity ratio of the easily demagnetized region to the non-easily demagnetized region is 1:(0.7-0.96), for example 1:0.876, 1:0.909 or 1:0.957; And / or, the coercivity ratio of the easily demagnetized region to the transition region is 1:(0.93-1), for example 1:0.930, 1:0.959 or 1:0.970; And / or, the coercivity is the same at all locations in the easily demagnetized region; And / or, the coercivity is the same at all positions along the Z-axis of the transition region; preferably, the coercivity decreases along the X-axis or Y-axis of the transition region away from the easily demagnetized region. And / or, the residual magnetism is the same at each location in the easily demagnetized region; And / or, the residual magnetism at each position along the Z-axis of the transition region is the same; preferably, the residual magnetism in the transition region decreases along the X-axis or Y-axis and away from the easily demagnetized region.

3. The neodymium iron boron magnet according to claim 1, characterized in that, The neodymium iron boron magnet is represented by the chemical formula R1-R2-TBM, wherein R1 is one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd, and Ho; R2 is Dy and / or Tb; T is one or more of Fe, Zn, Si, V, Cr, Mn, Ni, Ge, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F, and P; and M is one or more of Cu, Al, Co, Ga, Zr, and Ti. Preferably, all M elements are derived from the neodymium iron boron substrate. Preferably, the M elements include diffusion-introduced M elements, wherein the diffusion-introduced M elements preferably account for 0-0.4% of the mass percentage of the neodymium iron boron magnet. And / or, the microstructure of the NdFeB magnet includes Re2Fe 14 B-phase grains and Re-rich phase grain boundaries; the Re2Fe 14 The B-phase grains comprise a core and a shell; Re is one or more of Nd, Dy, and Tb.

4. The neodymium iron boron magnet according to claim 3, characterized in that, The Re2Fe in the easily demagnetized region 14 The difference in grain size between the B main phase grains does not exceed 8 μm; And / or, the Re2Fe of the transition region 14 The difference in grain size between the B main phase grains does not exceed 8 μm; And / or, the Re2Fe on the surface of the easily demagnetized region, the transition region, and the non-easily demagnetized region. 14 The B main phase grains have equal grain size; And / or, the Re2Fe at the center of the easily demagnetized region, the transition region, and the non-easily demagnetized region. 14 The B main phase grains have equal grain size; And / or, in the easily demagnetized region, the transition region, and the non-easily demagnetized region, the surface Re2Fe 14 The grain size of the B main phase grain is 1-1.5 times the grain size of the central main phase grain; And / or, the Re2Fe in the same XY plane of the easily demagnetized region, the transition region, and the non-easily demagnetized region. 14 The grain size ratio of the B main phase is 1:1:1; And / or, the Re2Fe on the surface of the easily demagnetized region, the transition region, and the non-easily demagnetized region. 14 The grain size of the B main phase is 1-12 μm; And / or, the thickness of the Re-rich phase grain boundaries in the easily demagnetized region is equal; And / or, the thickness of the Re-rich phase grain boundaries in the transition region is equal; And / or, the thickness of the Re-rich phase grain boundaries in the easily demagnetized region is 0.4-1 μm, for example 0.5 μm or 0.55 μm; And / or, the thickness of the Re-rich phase grain boundaries in the transition region is 0.4-1 μm, for example 0.5 μm or 0.52 μm; And / or, the thickness of the Re-rich phase grain boundaries in the non-demagnetizing region is 0.2-0.5 μm, for example 0.20 μm, 0.23 μm or 0.25 μm.

5. The neodymium iron boron magnet according to claim 3, characterized in that, The shell of the easily demagnetized region is (Nd,Dy,Tb)2Fe. 14 B hard magnetic layer; And / or, the shell of the non-demagnetizing region is (Nd,Dy)2Fe 14 B hard magnetic layer; And / or, the core and shell layers in the easily demagnetized region, the transition region, and the non-easily demagnetized region each independently satisfy the following conditions: the R1 content in the core layer is not less than the R1 content in the shell layer; the R2 content in the core layer is less than the R2 content in the shell layer; And / or, R2 is Tb, and the content of R2 in the easily demagnetized region, the transition region and the non-easily demagnetized region satisfies the following condition: easily demagnetized region ≥ transition region > non-easily demagnetized region; And / or, R2 is Dy, and the content of R2 in the easily demagnetized region, the transition region and the non-easily demagnetized region satisfies the following condition: non-easily demagnetized region = transition region = easily demagnetized region; And / or, the shell thickness of the easily demagnetized region is equal; And / or, the thickness of the shell layers in the transition region may be equal; And / or, the thickness of the shell layer of the easily demagnetized region is 2-3 μm, for example 2 μm, 2.1 μm or 2.5 μm; And / or, the thickness of the shell layer of the main phase grains in the transition region is 2-2.5 μm, for example 2 μm or 2.38 μm; And / or, the shell thickness of the main phase grains in the non-demagnetizing region is 0.5-2 μm, for example 0.95 μm, 1.0 μm or 1.1 μm; And / or, the thickness ratio of the shell and Re-rich phase grain boundary of the easily demagnetized region is (2-3):(0.4-1), for example 4:1, 2.1:0.5 or 2.5:0.55; And / or, the thickness ratio of the shell and Re-rich phase grain boundary in the transition region is (2-2.5):(0.4-1), for example 4:1 or 2.38:0.52; And / or, the thickness ratio of the shell of the main phase grains and the Re-rich phase grain boundary in the non-demagnetizing region is (0.5-2):(0.2-0.5), for example, 1.1:0.25, 1.0:0.23 or 0.95:0.

20.

6. The neodymium iron boron magnet according to claim 1, characterized in that, The neodymium iron boron magnet is a cuboid; the origin is preferably located at the center of the upper surface of the cuboid; the X-axis of the three-dimensional rectangular coordinate system is preferably parallel to one side of the upper surface; the ratio of the length to the width of the neodymium iron boron magnet is preferably (2-5):1, more preferably (2.42-3.7):1, for example 3:1, 3.65:1 or 39:10.7; And / or, the widths of the easily demagnetized areas are equal; preferably, the width of the easily demagnetized areas is no greater than 5 mm, for example, 2-4 mm; And / or, on any plane perpendicular to the orientation direction, the non-demagnetizing region is elliptical in shape; the ratio of the major axis a to the minor axis b of the non-demagnetizing region is preferably (2-15):1, for example 17.5:3.35; And / or, the widths of the transition regions are equal; preferably, the width of the transition region is 0-2mm, not 0, for example 0.5mm; And / or, the volume of the easily demagnetized region accounts for 50%-90% of the volume of the NdFeB magnet, for example, 47.85%; And / or, the volume of the transition region accounts for 0-28.4% of the volume of the NdFeB magnet, for example, 8.04%; And / or, the volume of the non-demagnetizing region accounts for 15.7%-44.11% of the volume of the NdFeB magnet; And / or, the thickness of the neodymium iron boron magnet is not greater than 5 mm, for example, 3 mm.

7. A method for preparing a neodymium iron boron magnet, characterized in that, It includes the following steps: On a neodymium iron boron substrate, a diffusion source is applied to the upper surface and / or the lower surface perpendicular to the Z-axis direction to carry out grain boundary diffusion parallel to the orientation direction; wherein, a diffusion source Dy is applied to the entire area of ​​the upper and lower surfaces, and a diffusion source Tb is applied to the outer annular region along the Z-axis direction to form a demagnetizing region, a transition region and a non-demagnetizing region.

8. The method for preparing a neodymium iron boron magnet according to claim 7, characterized in that, The diffusion source is applied by coating; preferably by spraying or printing; the dewaxing temperature for spraying is preferably 200-400°C; the dewaxing temperature for printing is preferably 100-500°C; when applying the diffusion source by coating, it is preferable to mix the diffusion source with a solvent and a binder to form a slurry; the solvent is preferably water, alcohol, ketone, or ester; the mass percentage of Dy or Tb in the diffusion source in the slurry is preferably 0.3%-1%; And / or, the diffusion source Dy satisfies any one of the following conditions ①-③: ①The diffusion source Dy is elemental Dy; ② The diffusion source Dy is a Dy-M alloy, and M is preferably one or more of Cu, Al, Co, Ga, Zr and Ti; the mass percentage of M in the Dy-M alloy preferably does not exceed 40%; ③The diffusion source Dy is a hydride of Dy or a fluoride of Dy; And / or, the diffusion source Tb satisfies any one of the following conditions ①-③: ①The diffusion source Tb is elemental Tb; ② The diffusion source Tb is a Tb-M alloy, and M is preferably one or more of Cu, Al, Co, Ga, Zr and Ti; the mass percentage of M in the Tb-M alloy preferably does not exceed 40%; ③The diffusion source Tb is a hydride of Tb or a fluoride of Tb; And / or, the temperature at which the grain boundary diffuses is 750-950°C, for example 900°C; And / or, the time for grain boundary diffusion is 5-30 hours, for example, 10 hours; And / or, after the grain boundary diffusion, an aging treatment is further included; the temperature of the aging treatment is preferably 300-600°C, for example 500°C; and the time of the aging treatment is preferably 1-10h, for example 3h.

9. A neodymium iron boron magnet prepared by the method for preparing a neodymium iron boron magnet as described in claim 7 or 8.

10. An application of a neodymium iron boron magnet as described in any one of claims 1-6 and 9 in magnetic steel.

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