Neodymium-iron-boron magnet and preparation method and application thereof

Abstract

The invention discloses a neodymium-iron-boron magnet and a preparation method and application thereof. The first easy-to-demagnetize area, the first transition area, the non-easy-to-demagnetize area, the second transition area and the second easy-to-demagnetize area are sequentially distributed in the direction perpendicular to the orientation direction, and the first easy-to-demagnetize area, the second easy-to-demagnetize area, the non-easy-to-demagnetize area, the first transition area and the second transition area are all rectangular; the HRE mass concentration of the first easy demagnetization area is the same as that of the second easy demagnetization area; the HRE mass concentrations of the first transition region and the second transition region are the same; the HRE mass concentration ratio of the non-easy demagnetization area to the first easy demagnetization area is (0.3-0.95): 1; the HRE mass concentration ratio of the first transition area to the first easy demagnetization area is (0.9-1): 1; wherein the HRE is Dy or Tb. According to the magnet, through the matching of the HRE content among the easily demagnetized area, the transition area and the difficultly demagnetized area, the demagnetization resistance of the neodymium-iron-boron magnet can be improved on the premise of saving the HRE consumption.

Description

Technical Field

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

[0002] Since the advent of NdFeB permanent magnet materials, they have been widely used in the fields of automobiles, wind power, home appliances, industrial robots, etc. Due to the different working conditions in various fields, the performance requirements of magnetic steel for products in their fields are also different. In recent years, new energy vehicles have flourished, and the demand for magnetic steel in the main drive motor has increased sharply. Since the normal operating temperature of the main drive motor is mainly concentrated in the range of 120-180°C, NdFeB requires higher coercivity and thermal stability. In order to improve the temperature resistance of rare earth permanent magnets, a large amount of heavy rare earth Dy and Tb is usually added to increase the main phase magnetocrystalline anisotropy field. However, the scarcity of heavy rare earth resources and high prices have seriously restricted the application of NdFeB magnets in various industries.

[0003] With the increasing demand for high-performance magnets, grain boundary diffusion technology has gradually become known and accepted by everyone. Conventional grain boundary diffusion technology uses a physical vapor deposition method to deposit the diffusion source on the surface of the magnet and then penetrate the diffusion source into the interior of the magnet along the grain boundary under high temperature and a certain pressure. The biggest advantage of this technology is that it can greatly improve the coercive force by using only a small amount of heavy rare earth elements (HRE) while keeping its remanence almost unchanged.

[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 NdFeB under the main drive motor working condition to identify the easily demagnetized and non-easy demagnetized areas. We found that the easily demagnetized areas all appear near the corners of the rotor air gap, while the demagnetization is not obvious near the rotor and the middle area of ​​the magnetic steel. Therefore, the coercive force of the easily demagnetized areas can be selectively strengthened, thereby saving the use of heavy rare earths in the non-easy demagnetized areas.

[0005] In the actual use of NdFeB, the performance requirements for each part of the magnet are not the same. For example, in the motor, since the reverse magnetic field generated after the coil in the motor is energized is not a uniform magnetic field, there will be an easy demagnetization area, a non-demagnetization area, and a transition area between the easy demagnetization area and the non-demagnetization area in the NdFeB. Due to the characteristics of the performance of each area mentioned above, the coercive force of each area needs to reach a matching relationship to ensure that the coercive force of the easy demagnetization area and the transition area is high, while the non-demagnetization area does not have surface magnetism and flux attenuation, and the remanence of the transition area and the non-demagnetization area is the highest. Summary of the invention

[0006] In order to solve the defects in the prior art, the present invention provides a neodymium iron boron magnet and a preparation method and application thereof. 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.

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

[0008] The present invention provides a neodymium iron boron magnet, the neodymium iron boron 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 an 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;

[0009] 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;

[0010] Wherein, HRE is Dy or Tb.

[0011] In the present invention, the HRE mass concentration means the percentage of the mass of 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 HRE introduced into the first easily demagnetized zone by diffusion to the total mass of the magnet in the first easily demagnetized zone.

[0012] In the present invention, the HRE mass concentration of the first easily demagnetized region is preferably 0.3%-1%.

[0013] In the present invention, the HRE mass concentration of the non-demagnetizable region is preferably 0.1%-0.9%.

[0014] In the present invention, the HRE mass concentration in the first transition zone is preferably 0.25%-1%.

[0015] 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.

[0016] In the present invention, 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.

[0017] Wherein, the HRE mass concentration of the first interface is preferably lower than that of the first transition zone.

[0018] Wherein, the HRE mass concentration of the first interface is preferably higher than the HRE mass concentration of the non-demagnetization-prone region.

[0019] Wherein, the mass concentration ratio of the first transition zone, the first interface and the non-demagnetization-prone zone is preferably: 1: (0.75-0.9): (0.3-0.75).

[0020] 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 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; M element includes one or more of Cu, Al, Co, Ga, Zr and Ti;

[0021] In some embodiments, the M elements are all from the NdFeB matrix.

[0022] In other embodiments, the M element includes M element introduced by diffusion, wherein the mass percentage of M element introduced by diffusion in the NdFeB magnet is preferably 0%-0.4%.

[0023] 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.

[0024] Preferably, the coercive force of the first easily demagnetized region ≥ the coercive force of the first transition region ≥ the coercive force of the non-easily demagnetized region.

[0025] 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.

[0026] The coercivity ratio of the non-demagnetizable region to the first demagnetizable region is preferably (0.8-95):1, for example, 0.85:1, 0.92:1 or 0.94:1.

[0027] Wherein, the coercive force difference between the first easily demagnetized region and the non-easily demagnetized region is preferably 0-10 kOe.

[0028] Wherein, the coercive force ratio of the non-easily demagnetized region to the first easily demagnetized region is preferably (0.7-0.96):1.

[0029] 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.

[0030] Wherein, the remanence ratio of the first easily demagnetized region to the non-easily demagnetized region is preferably (0.99-1):1.

[0031] Wherein, the remanence ratio of the first transition zone to the non-demagnetization-prone zone is preferably (0.99-1):1.

[0032] In some preferred embodiments, the width of the first easily demagnetized zone is the same as the width of the second easily demagnetized zone, and the width of the first transition zone is the same as the width of the second transition zone. The width means the length extending perpendicular to the orientation direction.

[0033] The width ratio of the first transition zone to the NdFeB magnet is preferably (0-0.1):1, for example, 0.093:1.

[0034] The width ratio between the non-demagnetization zone and the NdFeB magnet is preferably (0.2-0.7):1.

[0035] The width ratio of the first easily demagnetized region to the NdFeB magnet is preferably (0.05-0.4):1.

[0036] Wherein, the width of the first transition zone and the second transition zone is preferably 0-1 mm, and is not 0.

[0037] 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 described in the present invention have the same meaning as those in the art, i.e., the three grains intersect to form a triangle; the main phase grain shells described 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.

[0038] 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.

[0039] The grain size of the main phase grains on the surface of the first easily demagnetized region is preferably 1-1.5 times the grain size of the main phase grains on the surface of the non-easy demagnetized region.

[0040] 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-easy demagnetization zone is preferably 1-8um, for example, 1.3 or 1.4um.

[0041] 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.

[0042] 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 center main phase grains.

[0043] 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.

[0044] The surface layer means the surface perpendicular to the orientation direction, and the center means the median plane along the orientation direction.

[0045] 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.

[0046] Wherein, the thickness of the main phase grain shell layer of the first easily demagnetized area is preferably 0-2 um.

[0047] Wherein, the thickness of the main phase grain shell layer in the first transition zone is preferably 0-2 um.

[0048] Wherein, the thickness of the main phase grain shell layer of the non-demagnetized area is preferably 0-1um.

[0049] 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.

[0050] In the present invention, in the first easy demagnetization zone, the first transition zone and the non-easy demagnetization zone, the main phase grain core and the main phase grain shell meet the following conditions: the R1 content in the main phase grain core is preferably greater than or equal to the R1 content in the main phase grain shell; the R2 content in the main phase grain core is preferably less than or equal to the R2 content in the main phase grain shell; the M content in the main phase grain core is preferably less than or equal to the M content in the main phase grain shell; the M content in the main phase grain core is preferably less than or equal to the M content in the grain boundary triangle zone. Wherein, the M refers to the M element introduced by diffusion.

[0051] In the present invention, the R2 content in the main phase grain shell of the first easily demagnetized region, the first transition region and the non-easy demagnetized region preferably meets the following condition: first easily demagnetized region ≥ first transition region ≥ non-easy demagnetized region.

[0052] 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, 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 comprises HRE, and the HRE is Dy or Tb.

[0053] In the present invention, it is known to those skilled in the art 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.

[0054] 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.

[0055] In some embodiments, the diffusion source is a HRE.

[0056] In other embodiments, the diffusion source is HRE-M, wherein M comprises one or more of Cu, Al, Co, Ga, Zr and Ti; the mass percentage of M in the HRE-M is 0-40%, and is not 0. Those skilled in the art should understand that HRE-M represents an alloy formed by HRE and M elements.

[0057] In other embodiments, the diffusion source is a HRE hydride or a HRE fluoride.

[0058] In the present invention, the diffusion source can be applied by conventional methods in the art, such as coating.

[0059] 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.

[0060] 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.

[0061] In the present invention, the temperature of the heat treatment in the grain boundary diffusion is preferably 750 to 950°C, more preferably 800 to 950°C, and even more preferably 850 to 950°C.

[0062] 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.

[0063] Among them, an aging treatment is generally included after the heat treatment. 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.

[0064] The present invention also provides a NdFeB magnet prepared by the method for preparing the NdFeB magnet.

[0065] The present invention also provides an application of the above-mentioned NdFeB magnet in magnetic steel.

[0066] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0067] The reagents and raw materials used in the present invention are commercially available.

[0068] The positive and progressive effects of the present invention are:

[0069] 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 easy demagnetization zone and the non-easy demagnetization zone, the cross-zone mutual diffusion of HRE caused by the HRE concentration gradient difference in the transition zone can be reduced, thereby causing the performance of the boundary zone to show a gradient decrease and the anti-demagnetization effect to be weakened. Under the premise of ensuring the remanence of the NdFeB magnet, the attenuation of the surface magnetism and magnetic flux of the NdFeB magnet can be reduced, the anti-demagnetization ability of the NdFeB magnet can be improved, and at the same time, the amount of HRE can be saved.

[0070] In addition, the easy demagnetization area, the non-easy demagnetization area and the transition area of ​​the present invention are all rectangular, which can improve the anti-demagnetization ability of the four corners and long sides of the NdFeB magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 Schematic diagram of the structure of each area of ​​NdFeB magnet.

[0072] Figure 2 Schematic diagram of the structure of the main phase grain core and shell in each region of the NdFeB magnet.

[0073] Figure 3 This is a scanning electron microscope image of the easily demagnetized area of ​​the NdFeB magnet in Example 1.

[0074] Figure 4 This is a scanning electron microscope image of the non-demagnetized area of ​​the NdFeB magnet in Example 1.

[0075] Figure 5 for Figure 3 Scanning electron micrograph at 5x magnification.

[0076] Figure 6 for Figure 5 Line scan diagram of HRE content in the shell of the main phase grains.

[0077] Figure 7 for Figure 5 Line scan diagram of Nd content in the shell of the main phase grains.

[0078] Figure 8 for Figure 4 Scanning electron micrograph at 5x magnification.

[0079] Fig. 9 for Figure 8 Line scan diagram of HRE content in the shell of the main phase grains.

[0080] Fig.10 for Figure 8 Line scan diagram of Nd content in the shell of the main phase grains.

[0081] The reference numerals are as follows:

[0082] 1-first easily demagnetized region, 2-first transition region, 3-non-easy 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 described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

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

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

[0088]

[0089] Note: ① The “first / second easily demagnetized zone” in the table means the first easily demagnetized zone and the second easily demagnetized zone; ② The “first transition zone / second transition zone” in the table means the first transition zone and the second transition zone.

[0090] The microscopic grain boundary structures of each area of ​​Examples 1-4 and Comparative Examples 1-2 are listed in Table 2 below. Figure 3 , 5 is a scanning electron microscope image of the easily demagnetized area of ​​the NdFeB magnet in Example 1, Figure 4 , 8 This is a scanning electron microscope image of the non-demagnetized area of ​​the NdFeB magnet in Example 1. Figure 6 Corresponding to the line scan diagram of HRE content in the shell layer of the main phase grains in the easily demagnetized region of Example 1, Figure 7 Corresponding to the line scan diagram of the Nd content in the shell layer of the main phase grains in the easily demagnetized region of Example 1, Fig. 9 The line scan diagram of HRE content in the shell layer of the main phase grains in the non-easily demagnetized region corresponding to Example 1, Fig.10 Line scan diagram of Nd content in the shell layer of the main phase grains in the non-easily demagnetized region corresponding to Example 1.

[0091] Table 2

[0092]

[0093]

[0094] Note: The “first / second easily demagnetized area” in the table means the first easily demagnetized area and the second easily demagnetized area.

[0095] The preparation method of NdFeB magnets of Examples 1-4 and Comparative Examples 1-2 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 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.

[0096] The temperature of heat treatment in grain boundary diffusion is 850-950°C, and the time of heat treatment is 10 hours. After heat treatment, aging treatment is also included. The temperature of aging treatment is 500°C, and the time of aging treatment is 5 hours.

[0097] The mass concentration of each element in the NdFeB substrates of Examples 1-4 and Comparative Examples 1-2 and the types of HRE in the diffusion sources are listed in Table 3 below.

[0098] Table 3

[0099]

[0100] Effect Example 1

[0101] The following tests were performed on the NdFeB magnets of Examples 1-4 and Comparative Examples 1-2:

[0102] 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 of the China Institute of Metrology to measure the remanence.

[0103] 2. Coercive force test: Examples 1-4 and Comparative Examples 1-2 were prepared with samples of W2~3±0.1*L19±0.1*T4±0.1mm in specification. Two samples were stacked for testing. A coil with size W3*L19~20*T2.7mm was used in the permanent magnet precision measurement system NIM-62000 for room temperature testing (temperature ≤ 200°C).

[0104] 3. Demagnetization rate test: Use electromagnetic simulation software, model Ansys Workbench, input speed 13000rmp, then adjust its temperature to the corresponding temperature condition, collect the back electromotive force data of the motor under the same time and observe the change of magnetic steel cloud map to identify whether the magnetic steel is demagnetized. The calculation formula of demagnetization rate is: demagnetization rate = (high temperature back electromotive force - normal temperature back electromotive force) / normal temperature back electromotive force.

[0105] 4. The test method and instrument of line scan 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 scanned by pulling wires to characterize the distribution of elements such as Dy\Nd.

[0106] The technical effects of Examples 1-4 and Comparative Examples 1-2 are listed in Table 4 below:

[0107] Table 4

[0108]

[0109] Note: ① The “first / second easily demagnetized zone” in the table means the first easily demagnetized zone and the second easily demagnetized zone; ② The “first transition zone / second transition zone” in the table means the first transition zone and the second transition zone.

[0110] As can be seen from Tables 1-4, Examples 1-4 all use the same NdFeB substrate. Examples 1-4 can achieve a 130°C demagnetization rate of the NdFeB magnet of no more than 11%. Compared with Examples 1 and 2, Example 3 has a lower 130°C demagnetization rate. At the same time, for the non-easy demagnetization area, the HRE used in Example 3 is Dy, and the HRE used in Examples 1 and 2 are both Tb. The increase in coercive force of Dy diffusion is less than that of Tb diffusion, but the price of Dy raw materials is cheaper than Tb. Therefore, compared with Examples 1 and 2, Example 3 can reduce the 130°C demagnetization rate of the NdFeB magnet while saving the amount of Tb.

[0111] 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-demagnetized zone to the first demagnetized zone to be (0.9-0.95):1, and controls the HRE mass concentration ratio of the first transition zone to the first demagnetized zone to be (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.

[0112] Comparative Example 1 and Example 3 use the same substrate and have similar demagnetization rates. For the non-demagnetization-prone region, the diffusion source used in Comparative Example 1 is Tb, with a dosage of 1%, and the diffusion source used in Example 3 is Dy, with a dosage of 0.94%. In actual production, the price of Dy raw materials is cheaper than Tb, so Example 3 has a better overall cost performance.

[0113] 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 needs of the motor.

[0114] In general, embodiments 1-3 can reduce the usage of heavy rare earths, especially Tb, while NdFeB magnets meet the actual needs of electrodes, and have high overall cost performance.

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 region 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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