Neodymium-iron-boron magnets and methods of making and using the same

Abstract

The application discloses a neodymium-iron-boron magnet and a preparation method and application thereof. The neodymium-iron-boron magnet comprises a first easy demagnetization area, a first transition area, a non-easy demagnetization area, a second transition area and a second easy demagnetization area which are sequentially distributed along a direction perpendicular to an orientation direction; the first easy demagnetization area, the second easy demagnetization area, the non-easy demagnetization 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 concentration of the first transition area is the same as that of the second transition area; 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, HRE is Dy or Tb. The magnet can improve the anti-demagnetization capacity of the neodymium-iron-boron magnet under the premise of saving the HRE dosage through the cooperation of the HRE content between the easy demagnetization area, the transition area and the non-easy demagnetization area.

Description

TECHNICAL FIELD

[0001] The present application relates to a neodymium-iron-boron magnet and a preparation method and application thereof. BACKGROUND

[0002] Since the advent of neodymium-iron-boron permanent magnet, it has been widely used in the fields of automobile, wind power, household appliances, industrial robots, etc. Due to different working conditions in various fields, different performances of the magnetic steel products in the fields are required. In recent years, new energy vehicles have developed rapidly, and the demand for magnetic steel of main drive motor has increased dramatically. Since the normal working temperature of the main drive motor mainly concentrates in the range of 120-180℃, the neodymium-iron-boron needs higher coercivity and thermal stability. In order to improve the temperature resistance of rare earth permanent magnet, a large amount of heavy rare earth Dy and Tb is usually added to increase the anisotropic field of the main phase magnetic crystal. However, the heavy rare earth resources are scarce and the price is high, which seriously restricts the application of neodymium-iron-boron magnets in various industries.

[0003] With the increasing demand for high-performance magnets, the grain boundary diffusion technology has gradually been known and accepted by everyone. The conventional grain boundary diffusion technology adopts a physical vapor deposition method to deposit a diffusion source on the surface of the magnet, and then penetrates the diffusion source into the magnet along the grain boundary under high temperature and certain pressure. The biggest advantage of this technology is that it can greatly improve the coercivity using a small amount of heavy rare earth elements (HRE) without changing the remanence.

[0004] In terms of effective utilization rate of heavy rare earth, the traditional grain boundary diffusion product has been greatly improved compared with the non-grain boundary diffusion product. However, in order to further improve the utilization rate of heavy rare earth and reduce unnecessary waste of heavy rare earth, and to make the diffusion area more accurate and evaluate, another purpose of the present application is to identify the easy demagnetization and non-easy demagnetization areas of neodymium-iron-boron under the working condition of the main drive motor by means of electromagnetic simulation. We found that the easy demagnetization area appears near the rotor air gap corner, and the demagnetization is not obvious near the rotor and the middle area of the magnetic steel. Therefore, the coercivity of the easy demagnetization area can be strengthened, thereby saving the heavy rare earth in the non-easy demagnetization area.

[0005] In the actual use of neodymium-iron-boron, the performance requirements of each part of the magnet are not the same. For example, in the motor, since the reverse magnetic field generated after the coil is energized in the motor is not a uniform magnetic field, there will be an easy demagnetization area, a non-easy demagnetization area, and a transition area between the easy demagnetization area and the non-easy demagnetization area in the neodymium-iron-boron. Due to the characteristics of the performance of the above-mentioned areas, the coercivity of each area needs to reach a matching relationship to ensure that the coercivity of the easy demagnetization area and the transition area is high, the non-easy demagnetization area does not appear the decay of surface magnet and magnetic flux, and the remanence of the transition area and the non-easy demagnetization area is the highest. SUMMARY

[0006] The present application provides a neodymium-iron-boron magnet, a preparation method and application thereof, which can improve the demagnetization resistance of the neodymium-iron-boron magnet under the premise of saving the amount of HRE by matching the HRE content between the easy demagnetization zone, the transition zone and the non-easy demagnetization zone.

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

[0008] The present application provides a neodymium-iron-boron magnet, which comprises a first easy demagnetization zone, a first transition zone, a non-easy demagnetization zone, a second transition zone and a second easy demagnetization zone arranged in sequence along a direction perpendicular to an orientation direction.

[0009] The HRE mass concentration of the first easy demagnetization zone is the same as that of the second easy demagnetization zone; the HRE mass concentration of the first transition zone is the same as that of the second transition zone; the HRE mass concentration ratio of the non-easy demagnetization zone to the first easy demagnetization zone is (0.3-0.95):1; and the HRE mass concentration ratio of the first transition zone to the first easy demagnetization zone is (0.9-1):1.

[0010] In the present application, HRE is Dy or Tb.

[0011] In the present application, the HRE mass concentration refers to the percentage of the mass of HRE introduced into a certain zone by diffusion in the total mass of the magnet in the zone, for example, the HRE mass concentration of the first easy demagnetization zone refers to the percentage of the mass of HRE introduced into the first easy demagnetization zone by diffusion in the total mass of the magnet in the first easy demagnetization zone.

[0012] In the present application, the HRE mass concentration of the first easy demagnetization zone is preferably 0.3%-1%.

[0013] In the present application, the HRE mass concentration of the non-easy demagnetization zone is preferably 0.1%-0.9%.

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

[0015] In the present application, the HRE mass concentration of the first easy demagnetization zone is preferably higher than that of the non-easy demagnetization zone.

[0016] In the present application, a first interface is formed between the first transition zone and the non-easy demagnetization zone, and a second interface is formed between the second transition zone and the non-easy demagnetization zone, and the HRE mass concentration in the first interface is the same as that in the second interface.

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

[0018] Preferably, the HRE mass concentration of the first interface is higher than that of the non-soft-magnetic zone.

[0019] Preferably, the mass concentration ratio of the first transition zone, the first interface and the non-soft-magnetic zone is 1:(0.75-0.9):(0.3-0.75).

[0020] In the present application, the Nd-Fe-B magnet can be represented by the chemical formula R1-R2-T-B-M, wherein R1 includes one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 is 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; and M element contains one or more of Cu, Al, Co, Ga, Zr and Ti.

[0021] In some embodiments, the M element is entirely from the Nd-Fe-B base material.

[0022] In other embodiments, the M element contains a diffusion-introduced M element, and preferably, the mass percentage of the diffusion-introduced M element in the Nd-Fe-B magnet is 0%-0.4%.

[0023] In some preferred embodiments, the coercivity of the first soft-magnetic zone and the second soft-magnetic zone is the same, and the coercivity of the first transition zone and the second transition zone is the same.

[0024] Preferably, the coercivity of the first soft-magnetic zone is ≥ the coercivity of the first transition zone ≥ the coercivity of the non-soft-magnetic zone.

[0025] Preferably, the coercivity ratio of the first transition zone to the first soft-magnetic zone is (0.95-1):1, for example, 0.96:1 or 0.98:1.

[0026] Preferably, the coercivity ratio of the non-soft-magnetic zone to the first soft-magnetic zone is (0.8-95):1, for example, 0.85:1, 0.92:1 or 0.94:1.

[0027] Preferably, the coercivity difference between the first soft-magnetic zone and the non-soft-magnetic zone is 0-10 kOe.

[0028] wherein the coercivity ratio of the non-remanence zone to the first remanence zone is preferably (0.7-0.96): 1.

[0029] In some preferred embodiments, the remanence of the first remanence zone is the same as the remanence of the second remanence zone, and the remanence of the first transition zone is the same as the remanence of the second transition zone.

[0030] wherein the remanence ratio of the first remanence zone to the non-remanence zone is preferably (0.99-1): 1.

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

[0032] In some preferred embodiments, the width of the first remanence zone is the same as the width of the second remanence 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 perpendicularly to the orientation direction.

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

[0034] wherein the width ratio of the non-remanence zone to the neodymium-iron-boron magnet is preferably (0.2-0.7): 1.

[0035] wherein the width ratio of the first remanence zone to the neodymium-iron-boron 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] The grain boundary structure of the neodymium-iron-boron magnet known to those skilled in the art generally comprises R2Fe 14 B main phase grains, main phase grain shells, Nd-rich phases and grain boundary triangular regions. Wherein the meaning of the grain boundary triangular region described in the present application is conventional in the art, i.e. a triangular region formed by the intersection of three grains; wherein the meaning of the main phase grain shell described in the present application is conventional in the art, i.e. a (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 easy demagnetization region is the same as the grain size of the main phase grains in the second easy demagnetization region, the grain size of the main phase grains in the first transition region is the same as the grain size of the main phase grains in the second transition region; preferably, the grain size of the main phase grains in the first easy demagnetization region, the first transition region and the non-easy demagnetization region satisfies: first easy demagnetization region ≥ first transition region ≥ non-easy demagnetization region.

[0039] Preferably, the grain size of the surface layer main phase grains in the first easy demagnetization region is 1-1.5 times the grain size of the surface layer main phase grains in the non-easy demagnetization region.

[0040] Preferably, the grain size of the surface layer main phase grains in the first easy demagnetization region is 1-1.5 times the grain size of the surface layer main phase grains in the non-easy demagnetization region.

[0041] Preferably, the grain size of the surface layer main phase grains in the first easy demagnetization region is 1-1.5 times the grain size of the surface layer main phase grains in the non-easy demagnetization region.

[0042] Preferably, the grain size of the surface layer main phase grains in the first easy demagnetization region is 1-1.5 times the grain size of the surface layer main phase grains in the non-easy demagnetization region.

[0043] Preferably, the grain size of the surface layer main phase grains in the first easy demagnetization region is 1-1.5 times the grain size of the surface layer main phase grains in the non-easy demagnetization region.

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

[0045] In some preferred embodiments, the thickness of the main phase grain shell layer in the first easy demagnetization region is the same as the thickness of the main phase grain shell layer in the second easy demagnetization region, 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; preferably, the thickness of the main phase grain shell layer in the first easy demagnetization region, the first transition region and the non-easy demagnetization region satisfies: first easy demagnetization region ≥ first transition region ≥ non-easy demagnetization region.

[0046] Preferably, the thickness of the main phase grain shell layer in the first easy demagnetization region is 0-2 um.

[0047] Preferably, the thickness of the main phase grain shell layer in the first easy demagnetization region is 0-2 um.

[0048] Preferably, the thickness of the main phase grain shell layer of the non-freely demagnetizable region is 0-1 um.

[0049] Preferably, the thickness of the main phase grain shell layer of the first freely demagnetizable region and the thickness of the main phase grain shell layer of the first transition region are both 1-5 times the thickness of the main phase grain shell layer of the non-freely demagnetizable region.

[0050] In the present application, in the first freely demagnetizable region, the first transition region and the non-freely demagnetizable region, the main phase grain core and the main phase grain shell layer satisfy 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 layer; 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 layer; 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 layer; and the M content in the main phase grain core is preferably less than or equal to the M content in the grain boundary triangular region. The M refers to the M element introduced by diffusion.

[0051] In the present application, the R2 content in the main phase grain shell layer of the first freely demagnetizable region, the first transition region and the non-freely demagnetizable region preferably satisfies the following condition: first freely demagnetizable region≥first transition region≥non-freely demagnetizable region.

[0052] The present application also provides a preparation method of the above-mentioned neodymium-iron-boron magnet, which comprises the following steps: applying diffusion sources on different rectangular regions on the diffusion surface of a neodymium-iron-boron base material respectively, and performing grain boundary diffusion parallel to the orientation direction, thereby obtaining the neodymium-iron-boron magnet; wherein the diffusion surface is one surface of the neodymium-iron-boron base material perpendicular to the orientation direction, the rectangular regions are sequentially distributed along the direction perpendicular to the orientation direction, and the diffusion source contains HRE, and the HRE is Dy or Tb.

[0053] In the present application, it is known to those skilled in the art that when performing grain boundary diffusion, the HRE in the diffusion source is not completely diffused into the magnet, and the utilization rate is generally 85%-95%, so in the actual preparation process, a larger amount of HRE is generally applied.

[0054] In the present application, it is known to those skilled in the art that different grain boundary diffusion methods will have different coating thicknesses when diffusing the same amount of HRE into the magnet, so 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 HRE.

[0056] In some 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 some other embodiments, the diffusion source is HRE hydride or HRE fluoride.

[0058] In the present application, the diffusion source can be applied by conventional methods in the art, for example, by coating.

[0059] Preferably, the coating method is spraying or printing. Preferably, the dewaxing temperature of the spraying is 200-400°C, and the dewaxing temperature of the printing is 100-500°C.

[0060] When the diffusion source is applied by coating, the diffusion source is generally mixed with solvents and binders in certain proportions to form a slurry. The solvents are, for example, water, alcohol, ketone or ester.

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

[0062] In the present application, the time of the heat treatment in the grain boundary diffusion is preferably 5-30h, and more preferably 10-12h.

[0063] In the present application, the time of the heat treatment in the grain boundary diffusion is preferably 5-30h, and more preferably 10-12h.

[0064] The present application also provides a Nd-Fe-B magnet prepared by the above method.

[0065] The present application also provides a use of the above Nd-Fe-B magnet in magnetic steel.

[0066] On the basis of common knowledge in the art, the above preferred conditions can be combined in any manner to obtain various preferred examples of the present application.

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

[0068] The positive progress effect of the present application is that:

[0069] The Nd-Fe-B magnet described in the application comprises a transition zone, and by controlling the matching between the HRE content introduced by diffusion in the transition zone, the easy demagnetization zone and the non-easy demagnetization zone, the HRE cross-zone interdiffusion caused by the HRE concentration gradient difference of the transition zone can be reduced, so that the performance of the interface zone presents a gradient decline, causing the demagnetization resistance effect to weaken. The application can reduce the surface magnetic and magnetic flux decay of the Nd-Fe-B magnet under the premise of ensuring the remanence of the Nd-Fe-B magnet, improve the demagnetization resistance of the Nd-Fe-B magnet, and save the amount of HRE.

[0070] In addition, the application sets the easy demagnetization zone, the non-easy demagnetization zone and the transition zone to be rectangular, which can improve the demagnetization resistance of the four corners and the long side of the Nd-Fe-B magnet. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 It is a structure schematic diagram of each zone of the Nd-Fe-B magnet.

[0072] Figure 2 It is a structure schematic diagram of the main phase grain core and the shell layer in each zone of the Nd-Fe-B magnet.

[0073] Figure 3 It is a scanning electron microscope graph of the easy demagnetization zone of the Nd-Fe-B magnet in Example 1.

[0074] Figure 4 It is a scanning electron microscope graph of the non-easy demagnetization zone of the Nd-Fe-B magnet in Example 1.

[0075] Figure 5 It is a scanning electron microscope graph of the transition zone of the Nd-Fe-B magnet in Example 1. Figure 3 It is a scanning electron microscope graph of the transition zone of the Nd-Fe-B magnet in Example 1.

[0076] Figure 6 It is a line scanning graph of the HRE content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 1. Figure 5 It is a line scanning graph of the HRE content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 1.

[0077] Figure 7 It is a line scanning graph of the Nd content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 1. Figure 5 It is a line scanning graph of the Nd content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 1.

[0078] Figure 8 It is a scanning electron microscope graph of the easy demagnetization zone of the Nd-Fe-B magnet in Example 2. Figure 4 It is a scanning electron microscope graph of the easy demagnetization zone of the Nd-Fe-B magnet in Example 2.

[0079] Figure 9 It is a line scanning graph of the HRE content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 2. Figure 8 It is a line scanning graph of the HRE content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 2.

[0080] Figure 10 It is a line scanning graph of the Nd content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 2. Figure 8 It is a line scanning graph of the Nd content in the main phase grain shell layer of the Nd-Fe-B magnet in Example 2.

[0081] The reference signs are as follows:

[0082] 1 - first easy demagnetization zone, 2 - first transition zone, 3 - non-easy demagnetization zone, 4 - second transition zone, 5 - second easy demagnetization zone, 6 - main phase grain shell layer, 7 - main phase grain core. DETAILED DESCRIPTION

[0083] The present application is further illustrated by the following examples without thereby limiting the present application to the examples described. The experimental methods in the following examples, for which no specific conditions are indicated, are selected according to the conventional methods and conditions, or according to the instructions of the commercial products.

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

[0085] The structure of the Nd-Fe-B magnets of Examples 1-4 and Comparative Examples 1-2 is shown in Figure 1 and Figure 2 , wherein the direction of arrow M represents the magnetizing direction of the Nd-Fe-B magnet, the direction of arrow P represents the orientation direction of the Nd-Fe-B magnet; A surface represents the surface layer of the Nd-Fe-B magnet, and B surface represents the middle layer of the Nd-Fe-B 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 meaning of "first / second easy demagnetization zone" in the table is the first easy demagnetization zone and the second easy demagnetization zone; ② The meaning of "first transition zone / second transition zone" in the table is the first transition zone and the second transition zone.

[0090] The microstructure of the grain boundary of each zone of Examples 1-4 and Comparative Examples 1-2 is listed in Table 2 below. Figure 3 , 5 is the scanning electron microscope image of the easy demagnetization zone of the Nd-Fe-B magnet in Example 1, Figure 4 , 8 is the scanning electron microscope image of the non-easy demagnetization zone of the Nd-Fe-B magnet in Example 1. Figure 6 is the line scan image of the HRE content in the main phase grain shell layer of the easy demagnetization zone of Example 1, Figure 7 is the line scan image of the Nd content in the main phase grain shell layer of the easy demagnetization zone of Example 1, Figure 9 is the line scan image of the HRE content in the main phase grain shell layer of the non-easy demagnetization zone of Example 1, Figure 10 is the line scan image of the Nd content in the main phase grain shell layer of the non-easy demagnetization zone of Example 1.

[0091] Table 2

[0092]

[0093]

[0094] Note: The meaning of "first / second demagnetization easy zone" in the table is the first demagnetization easy zone and the second demagnetization easy zone.

[0095] The preparation method of the neodymium-iron-boron magnets of Examples 1-4 and Comparative Examples 1-2 comprises the following steps: applying diffusion sources on different rectangular zones on the diffusion surface of a neodymium-iron-boron substrate, respectively, performing grain boundary diffusion parallel to the orientation direction, and obtaining the neodymium-iron-boron magnets; wherein the diffusion surface is one surface of the neodymium-iron-boron substrate perpendicular to the orientation direction, and the rectangular zones are sequentially distributed along the direction perpendicular to the orientation direction.

[0096] In the grain boundary diffusion, the temperature of the heat treatment is 850-950℃, the time of the heat treatment is 10h, and after the heat treatment, aging treatment is further included, the temperature of the aging treatment is 500℃, and the time of the aging treatment is 5h.

[0097] In the neodymium-iron-boron substrates of Examples 1-4 and Comparative Examples 1-2, the mass concentrations of the elements and the HRE species in the diffusion sources are listed in Table 3 below.

[0098] Table 3

[0099]

[0100] Effect Example 1

[0101] The neodymium-iron-boron magnets of Examples 1-4 and Comparative Examples 1-2 are subjected to the following tests:

[0102] 1. Test of residual magnetism: the neodymium-iron-boron magnets of Examples 1-4 and Comparative Examples 1-2 are placed in a PFM-14 pulse magnetic property measuring instrument of China Institute of Metrology to measure the residual magnetism.

[0103] 2. Test of coercive force: the samples of Examples 1-4 and Comparative Examples 1-2 are prepared, the sample size is W2-3±0.1*L19±0.1*T4±0.1mm, two pieces are stacked for measurement, a W3*L19-20*T2.7mm coil is used in a permanent magnet precision measurement system NIM-62000 to perform normal temperature test (temperature ≤200℃).

[0104] 3. Test of demagnetization rate: an electromagnetic simulation software, Ansys Workbench, is used, the input rotation speed is 13000rmp, then the temperature is adjusted to the corresponding temperature working condition, the back electromotive force data of the motor and the magnetic steel cloud atlas changes are collected under the same time, and it is determined whether demagnetization occurs. The calculation formula of the 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 test instrument of the line scan map are: respectively, the selected area magnet surface is microphotographed under the equipment EMMA, the equipment model is JEOL 8530f, the shooting magnification is X3000, the two main phases are pulled and line scanned, and the Dy\Nd element distribution is represented.

[0106] The technical effects of examples 1-4 and comparative examples 1-2 are listed in the following table 4:

[0107] Table 4

[0108]

[0109] Note: ①The meaning of "first / second easy demagnetization area" in the table is the first easy demagnetization area and the second easy demagnetization area; ②The meaning of "first transition area / second transition area" in the table is the first transition area and the second transition area.

[0110] From tables 1-4, it can be seen that examples 1-4 all use the same neodymium iron boron base material. Examples 1-4 can realize that the demagnetization rate of the neodymium iron boron magnet at 130 DEG C is not more than 11%. Compared with examples 1 and 2, example 3 has a lower demagnetization rate at 130 DEG C, and for the non-easy demagnetization area, example 3 uses Dy as the HRE, and examples 1 and 2 both use Tb as the HRE, the diffusion of Dy coercive force is less than that of Tb, but the price of Dy raw material is cheaper than that of Tb. Therefore, compared with examples 1 and 2, example 3 can save the amount of Tb used and also reduce the demagnetization rate of the neodymium iron boron magnet at 130 DEG C.

[0111] Compared with example 4, example 3 uses relatively cheap Dy for diffusion, and by controlling the HRE mass concentration ratio of the non-easy demagnetization area to the first easy demagnetization area at (0.9-0.95):1 and the HRE mass concentration ratio of the first transition area to the first easy demagnetization area at (0.95-1):1, 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] Compared with example 3, comparative example 1 uses the same base material and has a comparable demagnetization rate. For the non-easy demagnetization area, comparative example 1 uses Tb as the diffusion source with a dosage of 1%, and example 3 uses Dy as the diffusion source with a dosage of 0.94%. In actual production, the price of Dy raw material is cheaper than that of Tb, so the comprehensive cost performance of example 3 is better.

[0113] Compared with example 1, comparative example 2 can reduce the amount of Tb used to a certain extent, but the demagnetization rate of comparative example 2 is as high as 25.7%, which cannot meet the actual needs of the motor.

[0114] Overall, embodiments 1-3 can reduce the use of heavy rare earths, especially the use of Tb, while meeting the actual needs of neodymium-iron-boron magnets, and have high comprehensive cost performance.

Claims

1. A neodymium iron boron magnet, characterized in that, The neodymium iron boron magnet includes 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 the orientation. 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. The HRE mass concentrations in the first easily demagnetized region and the second easily demagnetized region are the same; the HRE mass concentrations in the first transition region and the second transition region are the same; the HRE mass concentration ratio between the non-easily demagnetized region and the first easily demagnetized region is (0.3-0.95):1; the HRE mass concentration ratio between the first transition region and the first easily demagnetized region is (0.9-1):1; and the HRE mass concentration in the non-easily demagnetized region is 0.1%-0.9%. Where HRE is either Dy or Tb; The coercivity of the first easily demagnetized region and the second easily demagnetized region is the same, and the coercivity of the first transition region and the second transition region is the same; the coercivity of the first easily demagnetized region is greater than or equal to the coercivity of the first transition region is greater than or equal to the coercivity of the non-easily demagnetized region; the ratio of the coercivity of the first transition region to the first easily demagnetized region is (0.95-1):

1.

2. The neodymium iron boron magnet as described in claim 1, characterized in that, The HRE mass concentration in the first easily demagnetized region is 0.3%-1%; And / or, the HRE mass concentration in the first transition region is 0.25%-1%; And / or, the HRE mass concentration in the first easily demagnetized region is higher than that in the non-easily demagnetized region; And / or, a first interface is formed between the first transition region and the non-demagnetizing region, and a second interface is formed between the second transition region and the non-demagnetizing region, wherein the HRE mass concentration is the same in the first interface and the second interface.

3. The neodymium iron boron magnet as described in claim 2, characterized in that, The HRE concentration at the first interface is lower than that in the first transition region; And / or, the HRE mass concentration at the first interface is higher than the HRE mass concentration in the non-demagnetizing region; And / or, the mass concentration ratio of the first transition region, the first interface and the non-demagnetizing region is 1:(0.75-0.9):(0.3-0.75).

4. The neodymium iron boron magnet as described in claim 1, characterized in that, The coercivity ratio between the first transition region and the first easily demagnetized region is 0.96:1 or 0.98:1; And / or, the coercivity ratio of the non-demagnetizing region to the first demagnetizing region is (0.8-95):1; And / or, the coercivity difference between the first easily demagnetized region and the non-easily demagnetized region is 0-10 kOe; And / or, the coercivity ratio of the non-demagnetizing region to the first demagnetizing region is (0.7-0.96):

1.

5. The neodymium iron boron magnet as described in claim 4, characterized in that, The coercivity ratio between the non-demagnetizing region and the first demagnetizing region is 0.85:1, 0.92:1, or 0.94:

1.

6. The neodymium iron boron magnet as described in 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 refers to the length extending perpendicular to the orientation direction.

7. The neodymium iron boron magnet as described in claim 6, characterized in that, The width ratio of the first transition region to the width of the neodymium iron boron magnet is (0-0.1):1; And / or, the width ratio of the non-demagnetizing region to the width of the neodymium iron boron magnet is (0.2-0.7):1; And / or, the width ratio of the first easily demagnetized region to the width of the neodymium iron boron magnet is (0.05-0.4):1; And / or, the width of the first transition region and the second transition region is 0-1mm, and not 0.

8. The neodymium iron boron magnet as described in claim 7, characterized in that, The width ratio of the first transition region to the width of the neodymium iron boron magnet is 0.093:

1.

9. The neodymium iron boron magnet as described in claim 1, characterized in that, The grain size of the main phase grain in the first easily demagnetized region is the same as that of the main phase grain in the second easily demagnetized region, and the grain size of the main phase grain in the first transition region is the same as that of the main phase grain in the second transition region.

10. The neodymium iron boron magnet as described in claim 9, characterized in that, The grain size of the main phase grains in the first easily demagnetized region, the first transition region, and the non-easily demagnetized region satisfies the following condition: first easily demagnetized region ≥ first transition region ≥ non-easily demagnetized region; And / or, the grain size of the main phase grains on the surface of the first easily demagnetized region is 1-1.5 times the grain size of the main phase grains on the surface of the non-easily demagnetized region; And / or, the grain size of the surface main phase grains in the first easily demagnetized region is 1-12 μm; And / or, the grain size of the surface main phase grains in the first transition region is 1-12 μm; And / or, the grain size of the surface main phase grains in the non-demagnetizing region is 1-8 μm; And / or, in the first easily demagnetized region, the grain size of the surface main phase grains is 1-1.5 times the grain size of the central main phase grains; And / or, in the non-demagnetizing region, the grain size of the surface main phase grains is 1-1.3 times the grain size of the central main phase grains; And / or, in the first transition region, the grain size of the surface main phase grains is 1-1.5 times the grain size of the central main phase grains.

11. The neodymium iron boron magnet as described in claim 10, characterized in that, The grain size of the main phase grains on the surface of the first easily demagnetized region is 5-11 μm; And / or, the grain size of the surface main phase grains in the first transition region is 5-8 μm; And / or, the grain size of the surface main phase grains in the non-demagnetizing region is 1.3 μm or 1.4 μm.

12. The neodymium iron boron magnet as claimed in claim 1, characterized in that, The thickness of the main phase grain shell in the first easily demagnetized region is the same as the thickness of the main phase grain shell in the second easily demagnetized region, and the thickness of the main phase grain shell in the first transition region is the same as the thickness of the main phase grain shell in the second transition region.

13. The neodymium iron boron magnet as described in claim 12, characterized in that, In the first easily demagnetized region, the first transition region, and the non-easily demagnetized region, the thickness of the main phase grain shell layer satisfies the following: first easily demagnetized region ≥ first transition region ≥ non-easily demagnetized region; And / or, the thickness of the main phase grain shell in the first easily demagnetized region is 0-2 μm; And / or, the thickness of the main phase grain shell in the first transition region is 0-2 μm; And / or, the thickness of the principal phase grain shell in the non-demagnetizing region is 0-1 μm; And / or, the thickness of the main phase grain shell in the first easily demagnetized region and the thickness of the main phase grain shell in the first transition region are both 1-5 times the thickness of the main phase grain shell in the non-easily demagnetized region.

14. The neodymium iron boron magnet as described in claim 1, characterized in that, In the first easily demagnetized region, the first transition region, and the non-easily demagnetized region, the main phase grain nucleus and the main phase grain shell satisfy one or more of the following conditions: (a) The R1 content in the main phase grain nucleus is greater than or equal to the R1 content in the main phase grain shell; (b) The R2 content in the main phase grain nucleus is less than or equal to the R2 content in the main phase grain shell; (c) The M content in the main phase grain nucleus is less than or equal to the M content in the main phase grain shell; (d) The M content in the main phase grain nucleus is less than or equal to the M content in the grain boundary triangular region; And / or, the R2 content in the main phase grain shell of the first easily demagnetized region, the first transition region, and the non-easily demagnetized region satisfies the following condition: the first easily demagnetized region ≥ the first transition region ≥ the non-easily demagnetized region.

15. The method for preparing a neodymium iron boron magnet according to any one of claims 1-14, characterized in that, It includes the following steps: A diffusion source is applied to different rectangular regions on the diffusion surface of a NdFeB substrate to perform 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 regions are distributed sequentially along the orientation direction, and the diffusion source includes HRE, wherein the HRE is Dy or Tb.

16. A neodymium iron boron magnet prepared by the method for preparing a neodymium iron boron magnet according to claim 15.

17. An application of a neodymium iron boron magnet as described in any one of claims 1-14 or 16 in magnetic steel.

Images