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

Abstract

Disclosed in the present invention are a neodymium-iron-boron magnet, a preparation method therefor and a use thereof. The neodymium-iron-boron magnet comprises a first demagnetization-prone area, a first transition area, a non-demagnetization-prone area, a second transition area and a second demagnetization-prone area which are sequentially distributed in a direction perpendicular to the orientation direction; the first demagnetization-prone area, the second demagnetization-prone area, the non-demagnetization-prone area, the first transition area and the second transition area are all rectangular; the HRE mass concentration in the first demagnetization-prone area is the same as that in the second demagnetization-prone area; the HRE mass concentration in the first transition area is the same as that in the second transition area; the HRE mass concentration ratio of the non-demagnetization-prone area to the first demagnetization-prone area is (0.3-0.95):1; and the HRE mass concentration ratio of the first transition area to the first demagnetization-prone area is (0.9-1):1, wherein HRE is Dy or Tb. According to the magnet, by means of HRE content coordination of the demagnetization-prone areas, the transition areas and the non-demagnetization-prone area, the demagnetization resistance of the neodymium-iron-boron magnet can be improved while reducing the usage amount of HRE.

Description

Neodymium iron boron magnet and its preparation method and application Technical Field

[0001] The invention relates to a neodymium iron boron magnet and a preparation method and application thereof. Background Art

[0002] Since its introduction, neodymium iron boron (NdFeB) permanent magnets have been widely used in automotive, wind power, home appliances, industrial robotics, and other fields. Due to the varying operating conditions in each field, the performance requirements for magnetic steel used in these fields also vary. In recent years, with the booming development of new energy vehicles, the demand for magnetic steel in the main drive motors has increased dramatically. Since the normal operating temperature of main drive motors is primarily concentrated in the 120-180°C range, NdFeB requires higher coercivity and thermal stability. To improve the temperature resistance of rare earth permanent magnets, large amounts of heavy rare earths (Dy and Tb) are typically added to increase the main phase magnetocrystalline anisotropy field. However, the scarcity and high price of heavy rare earth resources have severely restricted the application of NdFeB magnets in various industries.

[0003] With the increasing demand for high-performance magnets, grain boundary diffusion (GBD) technology has gradually become well-known and accepted. Conventional GBD uses a physical vapor deposition method to deposit a diffusion source on the magnet surface. The source is then infiltrated into the magnet's interior along the grain boundaries under high temperature and pressure. The greatest advantage of this technology is that it can significantly increase coercivity using only a small amount of heavy rare earth elements (HRE) while maintaining virtually unchanged remanence.

[0004] In terms of the effective utilization rate of heavy rare earths, traditional grain boundary diffusion products have been greatly improved compared with non-grain boundary diffusion products. However, in order to further improve the utilization rate of heavy rare earths, reduce unnecessary waste of heavy rare earths, and at the same time to make the diffusion area more accurate and evaluated, another purpose of the present invention is to use electromagnetic simulation of neodymium iron boron under the main drive motor working conditions to identify the easily demagnetized and non-easy demagnetization areas. We found that the easily demagnetized areas all appear near the corners of the rotor air gap, while the demagnetization is not obvious in the middle area near the rotor and the magnet. Therefore, the coercive force of the easily demagnetized areas can be selectively strengthened, thereby saving the use of heavy rare earth in the non-easy demagnetization areas.

[0005] In the actual use of NdFeB magnets, the performance requirements for each part of the magnet vary. For example, in motors, the reverse magnetic field generated when the motor coil is energized is not uniform. Therefore, the NdFeB magnet will have an easily demagnetized region, a non-demagnetized region, and a transition region between the easy and non-demagnetized regions. Due to the performance characteristics of these regions, the coercivity of each region must be matched to ensure that the coercivity of the easily demagnetized and transition regions is high while the non-demagnetized region does not experience surface magnetism and flux attenuation. At the same time, the remanence in the transition and non-demagnetized regions is the highest.

[0006] Summary of the Invention

[0007] In order to solve the defects existing in the prior art, the present invention provides a neodymium iron boron magnet and its preparation method and application. The magnet can improve the anti-demagnetization ability of the neodymium iron boron magnet while saving the amount of HRE by coordinating the HRE content between the easy demagnetization zone, the transition zone and the non-demagnetization zone.

[0008] The present invention mainly solves the above technical problems through the following technical solutions.

[0009] The present invention provides a neodymium iron boron magnet, comprising a first easily demagnetized region, a first transition region, a non-easily demagnetized region, a second transition region, and a second easily demagnetized region, which are sequentially distributed along a direction perpendicular to an orientation direction, wherein the first easily demagnetized region, the second easily demagnetized region, the non-easily demagnetized region, the first transition region, and the second transition region are all rectangular;

[0010] The HRE mass concentration of the first easily demagnetized region is the same as that of the second easily demagnetized region; the HRE mass concentration of the first transition region is the same as that of the second transition region; the HRE mass concentration ratio of the non-easily demagnetized region to the first easily demagnetized region is (0.3-0.95):1; the HRE mass concentration ratio of the first transition region to the first easily demagnetized region is (0.9-1):1;

[0011] Wherein, HRE is Dy or Tb.

[0012] In the present invention, the HRE mass concentration means the percentage of the mass of the HRE introduced into a certain area by diffusion to the total mass of the magnet in that area. For example, the HRE mass concentration of the first easily demagnetized zone means the percentage of the mass of the HRE introduced into the first easily demagnetized zone by diffusion to the total mass of the magnet in the first easily demagnetized zone.

[0013] In the present invention, the HRE mass concentration of the first easily demagnetized region is preferably 0.3%-1%.

[0014] In the present invention, the HRE mass concentration of the non-easily demagnetized region is preferably 0.1%-0.9%.

[0015] In the present invention, the HRE mass concentration in the first transition zone is preferably 0.25%-1%.

[0016] In the present invention, the HRE mass concentration of the first easily demagnetized region is preferably higher than that of the non-easily demagnetized region.

[0017] In the present invention, a first interface is formed between the first transition region and the non-demagnetizable region, and a second interface is formed between the second transition region and the non-demagnetizable region. The HRE mass concentration in the first interface and the second interface is the same.

[0018] The HRE mass concentration at the first interface is preferably lower than that in the first transition zone.

[0019] The HRE mass concentration at the first interface is preferably higher than the HRE mass concentration at the non-demagnetizable region.

[0020] Wherein, the mass concentration ratio of the first transition region, the first interface and the non-demagnetizable region is preferably: 1: (0.75-0.9): (0.3-0.75).

[0021] In the present invention, the NdFeB magnet can be represented by the chemical formula R1-R2-TBM, wherein R1 includes one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 is HRE introduced by diffusion, and HRE is Dy or Tb; T contains 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; M element contains one or more of Cu, Al, Co, Ga, Zr and Ti;

[0022] In some embodiments, the M elements are all derived from a NdFeB matrix.

[0023] In other embodiments, the M element includes M element introduced by diffusion, wherein the mass percentage of the M element introduced by diffusion in the NdFeB magnet is preferably 0%-0.4%.

[0024] In some preferred embodiments, the coercive forces of the first easily demagnetized region and the second easily demagnetized region are the same, and the coercive forces of the first transition region and the second transition region are the same.

[0025] Preferably, the coercive force of the first easily demagnetized region is greater than or equal to the coercive force of the first transition region and greater than or equal to the coercive force of the non-easily demagnetized region.

[0026] The coercivity ratio of the first transition region to the first easily demagnetized region is preferably (0.95-1):1, for example, 0.96:1 or 0.98:1.

[0027] The coercivity ratio of the non-easily demagnetized region to the first easily demagnetized region is preferably (0.8-95):1, for example, 0.85:1, 0.92:1 or 0.94:1.

[0028] The coercive force difference between the first easily demagnetized region and the non-easily demagnetized region is preferably 0-10 kOe.

[0029] The coercive force ratio of the non-easily demagnetized region to the first easily demagnetized region is preferably (0.7-0.96):1.

[0030] In some preferred embodiments, the remanence of the first easily demagnetized region is the same as the remanence of the second easily demagnetized region, and the remanence of the first transition region is the same as the remanence of the second transition region.

[0031] The remanence ratio of the first easily demagnetized region to the non-easily demagnetized region is preferably (0.99-1):1.

[0032] The remanence ratio of the first transition region to the non-demagnetizable region is preferably (0.99-1):1.

[0033] In some preferred embodiments, the width of the first easily demagnetized region is the same as the width of the second easily demagnetized region, and the width of the first transition region is the same as the width of the second transition region. The width refers to the length extending perpendicular to the orientation direction.

[0034] The width ratio of the first transition region to the NdFeB magnet is preferably (0-0.1):1, for example, 0.093:1.

[0035] The width ratio of the non-demagnetized region to the NdFeB magnet is preferably (0.2-0.7):1.

[0036] The width ratio of the first easily demagnetized region to the NdFeB magnet is preferably (0.05-0.4):1.

[0037] The width of the first transition zone and the second transition zone is preferably 0-1 mm, and is not 0.

[0038] It is known to those skilled in the art that the grain boundary structure of NdFeB magnets generally includes R2Fe 14 B main phase grains, main phase grain shells, Nd-rich phase and grain boundary triangles. The grain boundary triangles mentioned in the present invention have the same meaning as those in the art, i.e., the intersection of three grains forms a triangle region; the main phase grain shells mentioned in the present invention have the same meaning as those in the art, i.e., (Nd / Dy)2Fe 14 B or (Nd / Tb)2Fe 14 B hard magnetic layer.

[0039] In some preferred embodiments, the grain size of the main phase grains in the first easily demagnetized zone is the same as the grain size of the main phase grains in the second easily demagnetized zone, and the grain size of the main phase grains in the first transition zone is the same as the grain size of the main phase grains in the second transition zone; wherein, preferably, the grain sizes of the main phase grains in the first easily demagnetized zone, the first transition zone and the non-easy demagnetized zone satisfy: first easily demagnetized zone ≥ first transition zone ≥ non-easy demagnetized zone.

[0040] The particle size of the main phase grains in the surface layer of the first easily demagnetized region is preferably 1-1.5 times the particle size of the main phase grains in the surface layer of the non-easily demagnetized region.

[0041] Among them, the particle size of the surface main phase grains in the first easily demagnetized zone is preferably 1-12um, more preferably 5-11um; the particle size of the surface main phase grains in the first transition zone is preferably 1-12um, more preferably 5-8um; the particle size of the surface main phase grains in the non-easily demagnetized zone is preferably 1-8um, for example, 1.3 or 1.4um.

[0042] Wherein, in the first easily demagnetized region, the particle size of the surface main phase grains is preferably 1-1.5 times the particle size of the central main phase grains.

[0043] Wherein, in the non-easily demagnetized region, the particle size of the surface main phase grains is preferably 1-1.3 times the particle size of the central main phase grains.

[0044] Wherein, in the first transition zone, the particle size of the surface main phase grains is preferably 1-1.5 times the particle size of the center main phase grains.

[0045] The surface layer means the surface perpendicular to the orientation direction, and the center means the median plane along the orientation direction.

[0046] In some preferred embodiments, the thickness of the main phase grain shell layer of the first easily demagnetized zone is the same as the thickness of the main phase grain shell layer of the second easily demagnetized zone, and the thickness of the main phase grain shell layer of the first transition zone is the same as the thickness of the main phase grain shell layer of the second transition zone; wherein, in the first easily demagnetized zone, the first transition zone and the non-easy demagnetized zone, the thickness of the main phase grain shell layer preferably satisfies: first easily demagnetized zone ≥ first transition zone ≥ non-easy demagnetized zone.

[0047] Wherein, the thickness of the main phase grain shell layer of the first easily demagnetized region is preferably 0-2 μm.

[0048] Wherein, the thickness of the main phase grain shell layer in the first transition zone is preferably 0-2 μm.

[0049] Wherein, the thickness of the main phase grain shell layer of the non-easily demagnetized region is preferably 0-1 μm.

[0050] The thickness of the main phase grain shell layer in the first easily demagnetized region and the thickness of the main phase grain shell layer in the first transition region are preferably 1-5 times the thickness of the main phase grain shell layer in the non-easily demagnetized region.

[0051] In the present invention, in the first easily demagnetized region, the first transition region, and the non-easily demagnetized region, the main phase grain cores and main phase grain shells meet the following conditions: the R1 content in the main phase grain cores is preferably greater than or equal to the R1 content in the main phase grain shells; the R2 content in the main phase grain cores is preferably less than or equal to the R2 content in the main phase grain shells; the M content in the main phase grain cores is preferably less than or equal to the M content in the main phase grain shells; and the M content in the main phase grain cores is preferably less than or equal to the M content in the grain boundary triangle region. The M refers to the M element introduced by diffusion.

[0052] In the present invention, the R2 content in the main phase grain shells of the first easily demagnetized region, the first transition region and the non-easily demagnetized region preferably meets the following condition: first easily demagnetized region ≥ first transition region ≥ non-easily demagnetized region.

[0053] The present invention also provides a method for preparing the above-mentioned NdFeB magnet, which comprises the following steps: applying diffusion sources to different rectangular areas on the diffusion surface of the NdFeB substrate respectively, and performing grain boundary diffusion parallel to the orientation direction, thereby obtaining the NdFeB magnet; wherein the diffusion surface is a surface of the NdFeB substrate perpendicular to the orientation direction, the rectangular areas are distributed sequentially along the direction perpendicular to the orientation direction, and the diffusion source comprises HRE, which is Dy or Tb.

[0054] In the present invention, those skilled in the art know that the HRE in the diffusion source is not completely diffused into the magnet during grain boundary diffusion, and its utilization rate is generally 85%-95%. Therefore, in the actual preparation process, a larger amount of HRE is generally applied.

[0055] In the present 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 HRE into the magnet. Therefore, in the actual preparation process, the coating thickness is not limited as long as the corresponding HRE diffusion amount is achieved.

[0056] In some embodiments, the diffusion source is a HRE.

[0057] In other embodiments, the diffusion source is HRE-M, wherein M comprises one or more of Cu, Al, Co, Ga, Zr, and Ti; and the mass percentage of M in the HRE-M is 0-40%, and is not 0. Those skilled in the art will understand that HRE-M represents an alloy formed by HRE and M elements.

[0058] In other embodiments, the diffusion source is a HRE hydride or a HRE fluoride.

[0059] In the present invention, the diffusion source can be applied by conventional methods in the art, such as coating.

[0060] The coating method is preferably spraying or printing. The dewaxing temperature of the spraying is preferably 200-400°C, and the dewaxing temperature of the printing is preferably 100-500°C.

[0061] When the diffusion source is applied by coating, the diffusion source is generally mixed with a solvent and a binder in a certain proportion to form a slurry, wherein the solvent is, for example, water, alcohol, ketone or ester.

[0062] In the present invention, the temperature of the heat treatment during the grain boundary diffusion is preferably 750-950°C, more preferably 800-950°C, and even more preferably 850-950°C.

[0063] In the present invention, the heat treatment time in the grain boundary diffusion is preferably 5 to 30 hours, more preferably 10 to 12 hours.

[0064] The heat treatment generally includes an aging treatment, wherein the temperature of the aging treatment is preferably 300-600° C., more preferably 480-550° C.; the time of the aging treatment is preferably 1-10 hours, more preferably 5-10 hours.

[0065] The present invention also provides a NdFeB magnet produced by the above-mentioned NdFeB magnet production method.

[0066] The present invention also provides an application of the above-mentioned NdFeB magnet in magnetic steel.

[0067] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0068] The reagents and raw materials used in the present invention are commercially available.

[0069] The positive progress effect of the present invention is:

[0070] The NdFeB magnet described in the present invention includes a transition zone, and by controlling the coordination between the HRE contents introduced by diffusion in the transition zone, the easily demagnetized zone, and the non-easily demagnetized zone, it is possible to reduce the cross-zone mutual diffusion of HRE caused by the HRE concentration gradient difference in the transition zone, thereby reducing the gradient decline in the performance of the boundary zone and weakening the anti-demagnetization effect. Under the premise of ensuring the remanence of the NdFeB magnet, it is possible to reduce the attenuation of the surface magnetism and magnetic flux of the NdFeB magnet, improve the anti-demagnetization ability of the NdFeB magnet, and at the same time, save the amount of HRE.

[0071] In addition, the easy demagnetization area, the non-easy demagnetization area and the transition area are all rectangular in the present invention, which can improve the anti-demagnetization ability of the four corners and long sides of the NdFeB magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 is a schematic diagram of the structure of each area of ​​the NdFeB magnet.

[0073] FIG2 is a schematic diagram of the structure of the core and shell of the main phase grains in each region of the NdFeB magnet.

[0074] FIG3 is a scanning electron microscope image of the easily demagnetized region of the NdFeB magnet in Example 1.

[0075] FIG4 is a scanning electron microscope image of the non-demagnetized area of ​​the NdFeB magnet in Example 1.

[0076] FIG5 is a scanning electron microscope image of FIG3 magnified 5 times.

[0077] FIG6 is a line scan diagram of the HRE content in the shell layer of the main phase grains in FIG5.

[0078] FIG. 7 is a line scan diagram of the Nd content in the shell layer of the main phase grains in FIG. 5 .

[0079] FIG8 is a scanning electron microscope image of FIG4 magnified 5 times.

[0080] FIG9 is a line scan diagram of the HRE content in the shell layer of the main phase grains in FIG8.

[0081] FIG10 is a line scan diagram of the Nd content in the shell layer of the main phase grains in FIG8 .

[0082] The reference numerals are as follows: 1 - first easily demagnetized region, 2 - first transition region, 3 - non-easily demagnetized region, 4 - second transition region, 5 - second easily demagnetized region, 6 - main phase grain shell, 7 - main phase grain core. DETAILED DESCRIPTION

[0083] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0084] Examples 1-4 and Comparative Examples 1-2

[0085] The structural schematic diagrams of the NdFeB magnets of Examples 1-4 and Comparative Examples 1-2 are shown in Figures 1 and 2, wherein the direction of the arrow M represents the magnetization direction of the NdFeB magnet, and the direction of the arrow P represents the orientation direction of the NdFeB magnet; the A surface represents the surface layer of the NdFeB magnet, and the B surface represents the middle layer of the NdFeB magnet.

[0086] The parameters of each zone of Examples 1-4 and Comparative Examples 1-2 are listed in Table 1 below.

[0087] Table 1 Note: ① The “first / second easily demagnetized zone” in the table refers to the first easily demagnetized zone and the second easily demagnetized zone; ② The “first transition zone / second transition zone” in the table refers to the first transition zone and the second transition zone.

[0088] The microscopic grain boundary structures of each region of Examples 1-4 and Comparative Examples 1-2 are listed in Table 2 below. Figures 3 and 5 are scanning electron microscope images of the easily demagnetized region of the NdFeB magnet in Example 1, and Figures 4 and 8 are scanning electron microscope images of the non-easily demagnetized region of the NdFeB magnet in Example 1. Figure 6 corresponds to a line scan of the HRE content in the shell of the main phase grains in the easily demagnetized region of Example 1, Figure 7 corresponds to a line scan of the Nd content in the shell of the main phase grains in the easily demagnetized region of Example 1, Figure 9 corresponds to a line scan of the HRE content in the shell of the main phase grains in the non-easily demagnetized region of Example 1, and Figure 10 corresponds to a line scan of the Nd content in the shell of the main phase grains in the non-easily demagnetized region of Example 1.

[0089] Table 2 Note: “First / Second Easy Demagnetization Zone” in the table means the first easy demagnetization zone and the second easy demagnetization zone.

[0090] The preparation method of the NdFeB magnets of Examples 1-4 and Comparative Examples 1-2 includes the following steps: applying diffusion sources to different rectangular areas on the diffusion surface of the NdFeB substrate, respectively, and performing grain boundary diffusion parallel to the orientation direction to obtain NdFeB magnets; wherein the diffusion surface is a surface of the NdFeB substrate perpendicular to the orientation direction, and the rectangular areas are distributed sequentially along the direction perpendicular to the orientation direction.

[0091] The heat treatment temperature in the grain boundary diffusion is 850-950° C., and the heat treatment time is 10 hours. After the heat treatment, an aging treatment is also included, and the aging treatment temperature is 500° C., and the aging treatment time is 5 hours.

[0092] The mass concentrations of the elements in the NdFeB substrates and the types of HRE in the diffusion sources of Examples 1-4 and Comparative Examples 1-2 are listed in Table 3 below.

[0093] Table 3

[0094] Effect Example 1

[0095] The following tests were performed on the NdFeB magnets of Examples 1-4 and Comparative Examples 1-2:

[0096] 1. Remanence test: The NdFeB magnets of Examples 1-4 and Comparative Examples 1-2 were placed in a PFM-14 pulse magnetic property measuring instrument produced by the China National Institute of Metrology to measure the remanence.

[0097] 2. Coercive force test: Samples of Examples 1-4 and Comparative Examples 1-2 were prepared with sample specifications of W2~3±0.1*L19±0.1*T4±0.1mm. Two samples were stacked for testing. Coils with dimensions of W3*L19~20*T2.7mm were used in the permanent magnet precision measurement system NIM-62000 for room temperature testing (temperature ≤200°C).

[0098] 3. Demagnetization Rate Test: Using electromagnetic simulation software (Ansys Workbench), we set the motor speed to 13,000 rpm and then adjusted the temperature to the corresponding operating temperature. We then collected back-EMF data and observed changes in the magnetic steel cloud map over the same period of time to determine if the magnet was demagnetized. The demagnetization rate is calculated using the formula: Demagnetization Rate = (High-Temperature Back-EMF - Room-Temperature Back-EMF) / Room-Temperature Back-EMF.

[0099] 4. The testing method and instrument for line scan images are as follows: the surface of the magnet in the selected area is microscopically photographed under the EMMA equipment. The equipment model is JEOL 8530f, and the shooting magnification is X3000. The two main phases are subjected to line scanning to characterize the distribution of elements such as Dy\Nd.

[0100] The technical effects of Examples 1-4 and Comparative Examples 1-2 are listed in Table 4 below:

[0101] Table 4 Note: ① The “first / second easily demagnetized zone” in the table refers to the first easily demagnetized zone and the second easily demagnetized zone; ② The “first transition zone / second transition zone” in the table refers to the first transition zone and the second transition zone.

[0102] As shown in Tables 1-4, Examples 1-4 all utilize the same NdFeB substrate. Examples 1-4 achieve a 130°C demagnetization rate of no more than 11% for NdFeB magnets. Compared to Examples 1 and 2, Example 3 achieves a lower 130°C demagnetization rate. Furthermore, for the non-easily demagnetized region, Example 3 utilizes Dy as the HRE, while Examples 1 and 2 both utilize Tb. Dy diffusion improves coercivity less than Tb diffusion, but Dy raw material is cheaper than Tb. Therefore, compared to Examples 1 and 2, Example 3 reduces the 130°C demagnetization rate of the NdFeB magnet while saving Tb.

[0103] Compared with Example 3 and Example 4, both use relatively cheap Dy for diffusion. Example 3 controls the HRE mass concentration ratio of the non-easily demagnetized region to the first easily demagnetized region to (0.9-0.95):1, and controls the HRE mass concentration ratio of the first transition region to the first easily demagnetized region to (0.95-1):1, so that the demagnetization rate of Example 3 is reduced from 10.2% to 1.6%, which can better meet the actual needs of the motor.

[0104] Comparing Comparative Example 1 and Example 3, both utilize the same substrate and exhibit comparable demagnetization rates. For the non-demagnetized region, Comparative Example 1 uses a diffusion source of 1% Tb, while Example 3 uses a diffusion source of 0.94% Dy. In actual production, Dy is cheaper than Tb, so Example 3 offers a better overall cost-effectiveness.

[0105] Compared with Example 1, although Comparative Example 2 can reduce the amount of Tb to a certain extent, the demagnetization rate of Comparative Example 2 is as high as 25.7%, which cannot meet the actual requirements of the motor.

[0106] In general, Examples 1-3 can reduce the usage of heavy rare earths, especially Tb, while ensuring that the NdFeB magnets meet the actual needs of the electrode, and have a high overall cost-effectiveness.

Claims

1. A neodymium iron boron magnet, characterized in that: The NdFeB magnet comprises a first easily demagnetized region, a first transition region, a non-easy demagnetized region, a second transition region, and a second easily demagnetized region, which are sequentially distributed along a direction perpendicular to the orientation direction, wherein the first easily demagnetized region, the second easily demagnetized region, the non-easy demagnetized region, the first transition region, and the second transition region are all rectangular; The HRE mass concentration of the first easily demagnetized region is the same as that of the second easily demagnetized region; the HRE mass concentration of the first transition region is the same as that of the second transition region; the HRE mass concentration ratio of the non-easily demagnetized region to the first easily demagnetized region is (0.3-0.95):1; the HRE mass concentration ratio of the first transition region to the first easily demagnetized region is (0.9-1):1; Wherein, HRE is Dy or Tb.

2. The NdFeB magnet according to claim 1, wherein: The HRE mass concentration of the first easily demagnetized region is 0.3%-1%; And / or, the HRE mass concentration of the non-demagnetizable region is 0.1%-0.9%; and / or, the HRE mass concentration in the first transition zone is 0.25%-1%; and / or, the HRE mass concentration of the first easily demagnetized region is higher than that of the non-easily demagnetized region; And / or, a first interface is formed between the first transition zone and the non-demagnetizable zone, a second interface is formed between the second transition zone and the non-demagnetizable zone, and the HRE mass concentration in the first interface is the same as that in the second interface; wherein the HRE mass concentration at the first interface is preferably lower than that in the first transition zone; wherein the HRE mass concentration at the first interface is preferably higher than that in the non-demagnetizable zone; wherein the mass concentration ratio of the first transition zone, the first interface and the non-demagnetizable zone is preferably: 1:(0.75-0.9):(0.3-0.75).

3. The NdFeB magnet according to claim 1, wherein: The first easily demagnetized region and the second easily demagnetized region have the same coercive force, and the first transition region and the second transition region have the same coercive force; Preferably, the coercive force of the first easily demagnetized region ≥ the coercive force of the first transition region ≥ the coercive force of the non-easy demagnetized region; Wherein, the coercivity ratio of the first transition region to the first easily demagnetized region is preferably (0.95-1):1, for example, 0.96:1 or 0.98:1; Wherein, the coercivity ratio of the non-demagnetized region to the first demagnetized region is preferably (0.8-95):1, for example, 0.85:1, 0.92:1 or 0.94:1; Wherein, the coercive force difference between the first easily demagnetized region and the non-easy demagnetized region is preferably 0-10 kOe; Wherein, the coercive force ratio of the non-easily demagnetized region to the first easily demagnetized region is preferably (0.7-0.96):

1.

4. The NdFeB magnet according to claim 1, characterized in that: The width of the first easily demagnetized region is the same as the width of the second easily demagnetized region, and the width of the first transition region is the same as the width of the second transition region; the width means the length extending perpendicular to the orientation direction; Wherein, the width ratio between the first transition zone and the NdFeB magnet is preferably (0-0.1):1, for example, 0.093:1; Wherein, the width ratio between the non-demagnetization zone and the NdFeB magnet is preferably (0.2-0.7):1; Wherein, the width ratio between the first easily demagnetized region and the NdFeB magnet is preferably (0.05-0.4):1; Wherein, the width of the first transition zone and the second transition zone is preferably 0-1 mm, and is not 0.

5. The NdFeB magnet according to claim 1, characterized in that: The grain size of the main phase grains in the first easy demagnetization zone is the same as the grain size of the main phase grains in the second easy demagnetization zone, and the grain size of the main phase grains in the first transition zone is the same as the grain size of the main phase grains in the second transition zone; Preferably, the grain sizes of the main phase grains of the first easily demagnetized region, the first transition region and the non-easy demagnetized region satisfy: first easily demagnetized region ≥ first transition region ≥ non-easy demagnetized region; Wherein, the grain size of the main phase grains on the surface of the first easily demagnetized area is preferably 1-1.5 times the grain size of the main phase grains on the surface of the non-easy demagnetized area; The particle size of the surface main phase grains in the first easily demagnetized zone is preferably 1-12um, more preferably 5-11um; the particle size of the surface main phase grains in the first transition zone is preferably 1-12um, more preferably 5-8um; the particle size of the surface main phase grains in the non-easy demagnetized zone is preferably 1-8um, for example, 1.3 or 1.4um; Wherein, in the first easily demagnetized region, the particle size of the surface main phase grains is preferably 1-1.5 times the particle size of the center main phase grains; Wherein, in the non-demagnetized region, the particle size of the surface main phase grains is preferably 1-1.3 times the particle size of the center main phase grains; Wherein, in the first transition zone, the particle size of the surface main phase grains is preferably 1-1.5 times the particle size of the center main phase grains.

6. The NdFeB magnet according to claim 1, characterized in that: The thickness of the main phase grain shell layer in the first easily demagnetized region is the same as the thickness of the main phase grain shell layer in the second easily demagnetized region, and the thickness of the main phase grain shell layer in the first transition region is the same as the thickness of the main phase grain shell layer in the second transition region; Among them, in the first easily demagnetized region, the first transition region and the non-easy demagnetized region, the thickness of the main phase grain shell preferably satisfies: the first easily demagnetized region ≥ the first transition region ≥ the non-easy demagnetized region; Wherein, the thickness of the main phase grain shell layer of the first easily demagnetized area is preferably 0-2um; Wherein, the thickness of the main phase grain shell layer in the first transition zone is preferably 0-2um; Wherein, the thickness of the main phase grain shell layer of the non-demagnetized area is preferably 0-1um; Preferably, the thickness of the main phase grain shell layer in the first easily demagnetized region and the thickness of the main phase grain shell layer in the first transition region are both 1-5 times the thickness of the main phase grain shell layer in the non-easy demagnetized region.

7. The NdFeB magnet according to claim 1, wherein: In the first easily demagnetized region, the first transition region, and the non-easy demagnetized region, the main phase grain cores and the main phase grain shells satisfy one or more of the following conditions: (a) The R1 content in the core of the main phase grain is greater than or equal to the R1 content in the shell of the main phase grain; (b) The R2 content in the core of the main phase grain is less than or equal to the R2 content in the shell of the main phase grain; (c) The M content in the core of the main phase grain is less than or equal to the M content in the shell of the main phase grain; (d) The M content in the main phase grain core is less than or equal to the M content in the grain boundary triangle area; And / or, the R2 content in the main phase grain shell layer of the first easily demagnetized region, the first transition region and the non-easy demagnetized region meets the following condition: first easily demagnetized region ≥ first transition region ≥ non-easy demagnetized region.

8. The method for preparing a NdFeB magnet according to any one of claims 1 to 7, characterized in that: It includes the following steps: Diffusion sources are applied to different rectangular areas on the diffusion surface of the NdFeB substrate respectively to carry out grain boundary diffusion parallel to the orientation direction, so as to obtain the NdFeB magnet; wherein the diffusion surface is a surface of the NdFeB substrate perpendicular to the orientation direction, the rectangular areas are distributed in sequence along the direction perpendicular to the orientation direction, the diffusion source includes HRE, and the HRE is Dy or Tb.

9. A NdFeB magnet obtained by the method for preparing a NdFeB magnet according to claim 8.

10. Use of the NdFeB magnet according to any one of claims 1 to 7 or 9 in magnetic steel.

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