Neodymium-iron-boron magnet and method for producing and using same

Abstract

This invention discloses a neodymium iron boron (NdFeB) magnet, its preparation method, and its applications. The NdFeB magnet of this invention 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, sequentially distributed along a direction perpendicular to the orientation. All three regions—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 rectangular. By controlling the Tb content introduced by diffusion in the transition region, the easily demagnetized region, and the non-easily demagnetized region, as well as the Dy content in all regions, this invention can reduce inter-regional Tb diffusion caused by the Tb concentration gradient difference in the transition region. This reduces the attenuation of the surface magnetism and magnetic flux of the NdFeB magnet while maintaining its remanence, thereby improving the demagnetization resistance of the NdFeB magnet. Furthermore, by setting the easily demagnetized region, the non-easily demagnetized region, and the transition region to be rectangular, this invention can improve the demagnetization resistance of the four corners and the long side of the NdFeB magnet.

Description

Technical Field

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

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

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

[0004] In terms of the effective utilization rate of heavy rare earth elements, traditional grain boundary diffusion products have significantly improved compared to non-grain boundary diffusion products. However, in order to further improve the utilization rate of heavy rare earth elements and reduce unnecessary waste, and to make the diffusion area more accurate and quantifiable, another objective of this invention is to use neodymium iron boron magnets to identify easily demagnetized and non-easily demagnetized regions under the operating conditions of a main drive motor. We found that easily demagnetized regions are all located near the corners of the rotor air gap, while demagnetization is not obvious in the area near the rotor and the middle of the magnets. Therefore, for easily demagnetized regions, high-performance magnets with the same remanence and low-performance magnets with the same remanence are bonded together to prepare the required combined magnets, thereby saving the use of heavy rare earth elements in the non-easily demagnetized regions.

[0005] In practical applications of NdFeB magnets, the performance requirements for each part of the magnet are not the same. For example, in a motor, because the reverse magnetic field generated when the coil is energized is not uniform, NdFeB magnets exhibit easily demagnetized regions, difficult-to-demagnetize regions, and transitional regions between these two regions. Due to the characteristics of these regions, the coercivity of each region needs to be matched to ensure that the easily demagnetized and transitional regions have sufficient coercivity while preventing attenuation of surface magnetism and magnetic flux in the difficult-to-demagnetize regions. Simultaneously, the transitional and difficult-to-demagnetize regions should have the highest remanence. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a neodymium iron boron magnet, its preparation method, and its applications. By adjusting the HRE content in the easily demagnetized region, transition region, and non-easily demagnetized region, this material can improve the demagnetization resistance of neodymium iron boron magnets.

[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 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 distributed sequentially along a direction perpendicular to the 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;

[0009] The Dy diffusion weight gain is the same in the first easily demagnetized region, the second easily demagnetized region, the non-easily demagnetized region, the first transition region, and the second transition region;

[0010] The Tb diffusion weight gain is the same in the first and second easily demagnetized regions.

[0011] The Tb diffusion weight gain is the same in the first transition region and the second transition region;

[0012] The Tb diffusion weight gain ratio between the first transition region and the first easily demagnetized region is (0.95-1):1;

[0013] The Tb diffusion weight gain ratio between the non-demagnetizing region and the first demagnetizing region is (0-0.05):1.

[0014] In this invention, the Tb diffusion weight gain means the percentage of the mass of Tb introduced into a certain region by diffusion to the total mass of the magnet in that region; the Dy diffusion weight gain means the percentage of the mass of Dy introduced into a certain region by diffusion to the total mass of the magnet in that region.

[0015] In this invention, the Tb diffusion weight gain ratio of the first transition region to the first easily demagnetized region is preferably 0.98:1.

[0016] In this invention, the Tb diffusion weight gain ratio between the non-demagnetizing region and the first demagnetizing region is 0:1.

[0017] In this invention, the Dy diffusion weight gain of the first easily demagnetized region, the second easily demagnetized region, the non-easily demagnetized region, the first transition region, and the second transition region can be 0.1wt%-1wt%, for example, 0.5wt%, 0.6wt%, or 0.7wt%.

[0018] In this invention, the Tb diffusion weight gain of the first easily demagnetized region is preferably 0.1wt%-1wt%, for example, 0.6wt%.

[0019] In this invention, the Tb diffusion weight gain in the non-demagnetizing region is preferably 0.05 wt% or less.

[0020] In this invention, the Tb diffusion weight gain in the first transition region is preferably 0.1wt%-1wt%.

[0021] In this invention, the Tb diffusion weight gain in the first easily demagnetized region is preferably higher than that in the first transition region.

[0022] In this invention, the Tb diffusion weight gain in the first transition region is preferably higher than that in the non-demagnetizing region.

[0023] In this invention, a first interface is formed between the first transition region and the first easily demagnetized region, and a second interface is formed between the second transition region and the second easily demagnetized region. The Tb diffusion weight gain in the first interface and the second interface is the same, and the Tb diffusion weight gain of the first interface and the first easily demagnetized region is preferably (0.95-1):1.

[0024] In this invention, a third interface is formed between the first transition region and the non-demagnetizing region, and a fourth interface is formed between the second transition region and the non-demagnetizing region. The Tb diffusion weight gain in the third interface and the fourth interface is the same. Preferably, the Tb diffusion weight gain ratio between the third interface and the center of the non-demagnetizing region is 1:(0-0.05).

[0025] In this invention, the neodymium iron boron magnet can be represented by the chemical formula R1-R2-R3-TBM, wherein R1 includes one or more of Pr, Nd, Ce, Er, Tm, Y, Lu, Gd and Ho; R2 is Tb introduced by diffusion; R3 is Dy introduced by diffusion; T includes one or more of Zn, Si, V, Cr, Mn, Ni, Ge, Ti, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F and P; and M includes one or more of Cu, Al, Co, Ga, Zr and Ti.

[0026] In some implementations, the M element is entirely derived from a NdFeB substrate.

[0027] In other embodiments, the M element comprises a diffusion-introduced M element, wherein the diffusion-introduced M element accounts for a preferred mass percentage of 0 wt% to 0.4 wt% of the NdFeB magnet.

[0028] In some preferred embodiments, 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, for example, 0.97:1 or 0.98:1.

[0029] The coercivity difference between the first easily demagnetized region and the non-easily demagnetized region is preferably 0-10 kOe, for example, 2.6 kOe, 3.5 kOe or 3.9 kOe.

[0030] The coercivity ratio between the non-demagnetizing region and the first demagnetizing region is preferably (0.7-0.96):1, for example, 0.85:1, 0.865:1 or 0.9:1.

[0031] In some preferred embodiments, the residual magnetism of the first easily demagnetized region is the same as that of the second easily demagnetized region, and the residual magnetism of the first transition region is the same as that of the second transition region.

[0032] The remanence ratio of the first easily demagnetized region to the non-easily demagnetized region is preferably (0.99-1):1, for example, 14.30:14.32 or 14.35:14.36.

[0033] The remanence ratio of the first transition region to the non-demagnetizing region is preferably (0.99-1):1, for example, 14.32:14.35, 14.33:14.35 or 14.36:14.38.

[0034] In some preferred embodiments, the width of the first demagnetizing region is the same as the width of the second demagnetizing 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.

[0035] Preferably, the width ratio of the first transition region to the width of the neodymium iron boron magnet is (0-0.1):1, for example, 0.093:1.

[0036] The width ratio of the non-demagnetizing region to the width of the neodymium iron boron magnet is preferably (0.2-0.7):1, for example, 0.527:1.

[0037] Preferably, the width of the first easily demagnetized region and the width of the neodymium iron boron magnet are (0.05-0.4):1.

[0038] Preferably, the widths of the first transition zone and the second transition zone are 0-1 mm and are not 0.

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

[0040] Preferably, 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.

[0041] Preferably, the grain size of the main phase grains on the surface of the first easily demagnetized region is 1-12 μm; the grain size of the main phase grains on the surface of the first transition region is 1-12 μm; and the grain size of the main phase grains on the surface of the non-easily demagnetized region is 1-8 μm.

[0042] In some preferred embodiments, 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; in the non-easily demagnetized 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 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.

[0043] The term "surface" refers to a surface perpendicular to the orientation direction, and "center" refers to the mid-plane along the orientation direction.

[0044] In this invention, the grain boundary structure of the magnet includes Re2Fe. 14 B-phase grains and Re-rich phase grain boundaries; the Re2Fe 14 The B main phase grains contain a main phase grain shell; Re is one or more of Nd, Dy, and Tb.

[0045] The term "main phase grain shell" is conventional in the art, namely (Nd, Dy / Tb)2Fe. 14 B. Hard magnetic layer. The meaning of the Re-rich phase grain boundary region is unconventional in the art, that is, a two-particle grain boundary region with Re > 95%.

[0046] In some preferred embodiments, the Tb content in the main phase grain shell of the first easily demagnetized region and the second easily demagnetized region is the same; the Tb content in the main phase grain shell of the first transition region and the second transition region is the same; and the Tb content in the main phase grain shell of the first easily demagnetized region is ≥ the Tb content in the main phase grain shell of the first transition region.

[0047] In some preferred embodiments, the ratio of Tb content in the non-demagnetizing region to that in the main phase grain shell of the first demagnetizing region is (0-0.05):(0.3-0.65), for example, 0.02:0.60, 0.01:0.59 or 0.02:0.57.

[0048] In some preferred embodiments, the ratio of Tb content in the first transition region to the main phase grain shell of the first easily demagnetized region is (0.2-0.65):(0.2-0.65), for example, 0.59:0.60, 0.58:0.59 or 0.57:0.57.

[0049] In some preferred embodiments, 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, 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, the thickness of the Re-rich grain boundary in the first easily demagnetized region is the same as the thickness of the Re-rich grain boundary in the second easily demagnetized region, and the thickness of the Re-rich grain boundary in the first transition region is the same as the thickness of the Re-rich grain boundary in the second transition region.

[0050] Among them, the thickness of the main phase grain shell in the first easily demagnetized region, the first transition region, and the non-easily demagnetized region preferably satisfies the following condition: first easily demagnetized region ≥ first transition region ≥ non-easily demagnetized region.

[0051] Among them, in the first easily demagnetized region, the first transition region and the non-easily demagnetized region, the thickness of the Re-rich grain boundary of the main phase grain preferably satisfies: the first easily demagnetized region ≥ the first transition region ≥ the non-easily demagnetized region.

[0052] The shells and Re-rich grain boundaries between the main phase grains in the first easily demagnetized region contain a high concentration of Dy and Tb, with a preferred thickness of 0-3 μm; the shells and Re-rich grain boundaries between the main phase grains in the first transition region contain a high concentration of Dy and Tb, with a preferred thickness of 0-3 μm; and the shells and Re-rich grain boundaries between the main phase grains in the non-easily demagnetized region contain a high concentration of Dy, with a preferred thickness of 0-2 μm.

[0053] Preferably, 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.

[0054] In the first easily demagnetized region, the thickness of the main phase grain shell is preferably 0-4 μm, more preferably 0.5-1.5 μm; the thickness of the Re grain boundary is preferably 0-1 μm, but not 0; the ratio of the thickness of the main phase grain shell to the thickness of the Re-rich grain boundary is preferably (0.5-1.5):(0-1), but not 0.

[0055] In the first transition region, the thickness of the main phase grain shell is preferably 0-4 μm, preferably 0.5-1.5 μm; the thickness of the Re-rich grain boundary is preferably 0-1 μm, but not 0; the ratio of the thickness of the main phase grain shell to the thickness of the Re-rich grain boundary is preferably (0.5-1.5):(0-1), but not 0.

[0056] In the non-demagnetizing region, the thickness of the main phase grain shell is preferably 0-2 μm, preferably 0.5-1 μm; the thickness of the Re-rich grain boundary is preferably 0-1 μm, but not 0; the ratio of the thickness of the main phase grain shell to the thickness of the Re-rich grain boundary is preferably (0.5-1.5):(0-1), but not 0.

[0057] In some preferred embodiments, the main phase grain shell of the first easily demagnetized region includes a first inner shell and a first outer shell; the main phase grain shell of the first transition region includes a second inner shell and a second outer shell; and the main phase grain shell of the non-easily demagnetized region includes a third inner shell.

[0058] The inner shell refers to the region where the Dy content in the main phase grain shell accounts for 80% or more of the sum of the total Tb and Dy element content; the outer shell refers to the region where the Tb content in the main phase grain shell accounts for 80% or more of the sum of the total Tb and Dy element content.

[0059] Preferably, the Tb diffusion weight gain of the first outer shell layer and the second outer shell layer satisfies the condition that the first outer shell layer ≥ the second outer shell layer.

[0060] Preferably, the Tb diffusion weight gain in the first outer shell layer is 0.1wt%-0.9wt%, for example, 0.6wt%.

[0061] Preferably, the Tb diffusion weight gain in the second outer shell layer is 0.1wt%-0.8wt%, for example, 0.6wt%.

[0062] The Dy diffusion weight gain of the first inner shell, the second inner shell, and the third inner shell preferably satisfies the following condition: third inner shell ≥ second inner shell ≥ first inner shell.

[0063] Preferably, the Dy diffusion weight gain in the first inner shell is 0.1wt%-0.9wt%, for example, 0.5wt%, 0.6wt%, or 0.7wt%.

[0064] The Dy diffusion weight gain in the second inner shell is preferably 0.1wt%-0.9wt%, for example, 0.5wt%, 0.6wt%, or 0.7wt%.

[0065] The Dy diffusion weight gain in the third inner shell is preferably 0.1wt%-0.9wt%, for example, 0.5wt%, 0.6wt%, or 0.7wt%.

[0066] Preferably, the thicknesses of the first outer shell layer and the second outer shell layer satisfy the following condition: the thickness of the first outer shell layer is greater than or equal to that of the second outer shell layer.

[0067] Preferably, the thicknesses of the first inner shell layer, the second inner shell layer, and the third inner shell layer satisfy the following condition: third inner shell layer ≥ second inner shell layer ≥ first inner shell layer.

[0068] Preferably, the thicknesses of the first inner shell layer and the first outer shell layer satisfy the following condition: the thickness of the first outer shell layer is less than or equal to the thickness of the first inner shell layer.

[0069] Preferably, the thicknesses of the second inner shell layer and the second outer shell layer satisfy the condition that the thickness of the second outer shell layer is less than or equal to the thickness of the second inner shell layer.

[0070] The thickness of the first inner shell layer is preferably 0-2 μm, for example, 1.8 μm or 1.9 μm.

[0071] The thickness of the first outer shell layer is preferably 0-2 μm, for example, 1.7 μm, 1.8 μm or 1.9 μm.

[0072] The thickness of the second inner shell layer is preferably 0-2 μm, for example 1.8 μm or 1.9 μm.

[0073] The thickness of the second outer shell layer can be 0-2 μm, for example, 1.6 μm or 1.7 μm.

[0074] The thickness of the third inner shell layer can be 0-2 μm, for example, 2.0 μm or 1.9 μm.

[0075] In the preferred embodiment described above, the main phase grain shell of the non-demagnetizing region may further include a third outer shell layer.

[0076] The Tb diffusion weight gain in the third outer shell of the main phase grain shell in the non-demagnetizing region can be 0-0.05 wt%.

[0077] Among them, in the main phase grain shells of the first easily demagnetized region, the first transition region and the non-easily demagnetized region, the Tb diffusion weight gain of the first outer shell layer, the second outer shell layer and the third outer shell layer preferably satisfies: first outer shell layer ≥ second outer shell layer > third outer shell layer.

[0078] Among them, in the main phase grain shell layers of the first easily demagnetized region, the first transition region and the non-easily demagnetized region, the thicknesses of the first outer shell layer, the second outer shell layer and the third outer shell layer preferably satisfy: first outer shell layer ≥ second outer shell layer > third outer shell layer.

[0079] Preferably, the thicknesses of the third inner shell and the third outer shell in the main phase grain shell of the non-demagnetizing region satisfy the following condition: the thickness of the third inner shell is greater than that of the third outer shell.

[0080] The thickness of the third outer shell layer of the main phase grain shell layer in the non-demagnetizing region can be 0-0.5 μm.

[0081] The present invention also provides a method for preparing the NdFeB magnet, comprising the following steps: applying a diffusion source to a first easily demagnetized region, a first transition region, a non-easily demagnetized region, a second transition region, and a second easily demagnetized region distributed perpendicular to the orientation direction on a NdFeB substrate, and performing grain boundary diffusion parallel to the orientation direction to obtain the NdFeB magnet; wherein the diffusion source contains Dy and / or Tb.

[0082] As is known to those skilled in the art in this invention, during grain boundary diffusion, the Dy or Tb in the diffusion source does not completely diffuse into the magnet, and its utilization rate is generally 85%-95%. Therefore, in the actual preparation process, a larger amount of Dy or Tb is usually applied.

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

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

[0085] In other embodiments, the diffusion source is a Dy-M alloy, where M comprises one or more of Cu, Al, Co, Ga, Zr, and Ti. The mass percentage of M in the Dy-M alloy is 0-40%, and not zero.

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

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

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

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

[0090] In this invention, the diffusion source can be applied using methods conventional in the art, such as coating.

[0091] The coating method is preferably spraying or printing. The dewaxing temperature for spraying is preferably 200–400°C, and the dewaxing temperature for printing is preferably 100–500°C.

[0092] When the diffusion source is applied by the coating method, the diffusion source is generally mixed with solvent and binder in a certain proportion to form a slurry.

[0093] The solvent may be, for example, water, alcohol, ketone or ester.

[0094] In this invention, the temperature of the heat treatment during grain boundary diffusion is preferably 750–950°C, for example, 850°C.

[0095] In this invention, the heat treatment time during grain boundary diffusion is preferably 5 to 30 hours, for example, 25 hours.

[0096] In this invention, the heat treatment in the grain boundary diffusion generally includes an aging treatment.

[0097] The aging treatment temperature is preferably 300–600°C, for example, 490°C.

[0098] The aging process is preferably carried out over a period of 1 to 10 hours, for example, 6 hours.

[0099] The present invention also provides a neodymium iron boron magnet prepared by the above-described method for preparing neodymium iron boron magnets.

[0100] The present invention also provides an application of the above-mentioned neodymium iron boron magnet in magnetic steel.

[0101] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0102] The reagents and raw materials used in this invention are all commercially available.

[0103] The positive and progressive effects of this invention are as follows:

[0104] The neodymium iron boron magnet described in this invention includes a transition region. By controlling the Tb content introduced by diffusion in the transition region, the easily demagnetized region, and the non-easily demagnetized region, as well as the Dy content in all regions, the problem of gradient decrease in the performance of the boundary region and weakened anti-demagnetization effect caused by the Tb concentration gradient difference in the transition region can be reduced. This can reduce the attenuation of the surface magnetism and magnetic flux of the neodymium iron boron magnet while ensuring the remanence of the neodymium iron boron magnet, thereby improving the anti-demagnetization ability of the neodymium iron boron magnet.

[0105] In addition, the present invention sets the easily demagnetized area, the non-easily demagnetized area and the transition area to be rectangular, which can improve the demagnetization resistance of the four corners and the long side of the neodymium iron boron magnet. Attached Figure Description

[0106] Figure 1 This is a schematic diagram of the structure of each region of a neodymium iron boron magnet.

[0107] Figure 2 This is a schematic diagram of the structure of the main phase grain nuclei and shells in each region of a neodymium iron boron magnet.

[0108] Figure 3 This is a scanning electron microscope image of the NdFeB transition region in Example 1.

[0109] Figure 4 for Figure 3 Line scan of Cu content in the grain shell.

[0110] Figure 5 for Figure 3 Line scan of Al content in the grain shell.

[0111] Figure 6 for Figure 3 Line scan of the Dy content in the grain shell.

[0112] Figure 7 for Figure 3 Line scan of Tb content in the grain shell.

[0113] Figure 8 for Figure 3 Line scan image of Nd content in the grain shell.

[0114] Possession Mark:

[0115] 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 nucleus, 8-First inner shell, 9-First outer shell, 10-Second inner shell, 11-Second outer shell, 12-Third inner shell. Detailed Implementation

[0116] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0117] Examples 1-3 and Comparative Examples 1-2

[0118] A diffusion source is applied to a NdFeB substrate along a first easily demagnetized region, a first transition region, a non-easily demagnetized region, a second transition region, and a second easily demagnetized region distributed perpendicular to the orientation direction, and grain boundary diffusion is performed parallel to the orientation direction to obtain the NdFeB magnet; the diffusion source contains Dy and / or Tb; wherein the utilization rate of Dy or Tb in the diffusion source is 85%-95%.

[0119] The heat treatment during grain boundary diffusion is carried out at a temperature of 850℃ for 25 hours. After the heat treatment, an aging treatment is also included, which is carried out at a temperature of 490℃ for 6 hours.

[0120] The parameters of each region of the NdFeB magnets in Examples 1-3 and Comparative Examples 1-2 are listed in Tables 1, 2 and 3 below. The elemental content of the NdFeB substrates used in Examples 1-3 and Comparative Examples 1-2 is shown in Table 4.

[0121] Schematic diagrams of the neodymium iron boron magnets in Examples 1-3 and Comparative Examples 1-2 are shown below. Figure 1 and Figure 2 As shown, the direction of arrow M represents the magnetization direction of the NdFeB magnet, and 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.

[0122] Table 1. Diffusion weight gain of Dy and Tb in each region of the NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-2, and the ratio of Tb content in the main phase grain shell of each region.

[0123]

[0124] The scanning electron microscope (SEM) image of the transition region of the neodymium iron boron magnet prepared in Example 1 and the line scan images of the Cu, Al, Dy, Tb, and Nd contents in the main phase grain shell are shown below. Figure 3-8 As shown.

[0125] Table 2. Coercivity ratios, width ratios, and main phase grain sizes of NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-2

[0126]

[0127] Table 3. Inner and outer shell layer thicknesses of the main phase grains in each region of the NdFeB magnets prepared in Examples 1-3 and Comparative Examples 1-2, as well as the diffusion weight gain of Dy and Tb.

[0128]

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

[0130] Pr Nd Dy Gd Co Ho Cu Al Ga B Zr Ti Fe Total rare earth content 3 27 0 0 0.5 0 0.2 0.1 0.3 0.98 0 0.2 margin 3

[0131] Example 1

[0132] The neodymium iron boron magnets of Examples 1-3 and Comparative Examples 1-2 were tested as follows, and the results are listed in Table 5.

[0133] 1. Coercivity test: Samples of Examples 1-3 and Comparative Examples 1-2 were prepared with a sample size of W2~3±0.1*L19±0.1*T4±0.1mm. Two samples were stacked and tested at room temperature (temperature ≤200℃) using a coil with a size of W3*L19~20*T2.7mm on a permanent magnet precision measurement system NIM-62000.

[0134] 2. Demagnetization Rate Test: Using electromagnetic simulation software, Ansys Workbench, with an input speed of 1300 rpm, and the temperature adjusted to the corresponding operating condition, back EMF data of the motor was collected over the same time period, and changes in the magnet contour plot were observed to determine whether demagnetization had occurred. The formula for calculating the demagnetization rate is: Demagnetization Rate = (High-Temperature Back EMF - Room-Temperature Back EMF) / Room-Temperature Back EMF.

[0135] 3. Remanence test: The neodymium iron boron magnets of Examples 1-4 and Comparative Examples 1-2 were placed in the PFM-14 pulse magnetic property measuring instrument of the National Institute of Metrology of China to measure the remanence.

[0136] 4. The test method and instrument for line scan images are as follows: The selected area of ​​the magnet surface is microscopically photographed under the EMMA equipment. The equipment model is JEOL 8530f, and the magnification is X3000. Line scans are performed on the two main phase grains to characterize the distribution of elements such as Cu, Al, Dy, Tb and Nd.

[0137] Table 5. Coercivity and demagnetization resistance of different regions in the magnets of Examples 1-3 and Comparative Examples 1-2.

[0138]

[0139] Note: ① In the table, "First Demagnetization Zone / Second Easy Demagnetization Zone" means either the first easy demagnetization zone or the second easy demagnetization zone; ② In the table, "First Transition Zone / Second Transition Zone" means either the first transition zone or the second transition zone.

[0140] As shown in Table 5, the coercivity ratio between the first transition region and the first easily demagnetized region of the NdFeB magnets prepared in Examples 1-3 is between (0.95-1):1, and the coercivity difference between the first easily demagnetized region and the non-easily demagnetized region is between 2.6-3.9 kOe. The demagnetization rate of the NdFeB magnets in Examples 1-3 at 130℃ is only 2.5%-6.1%, indicating that Examples 1-3 have more remanence and excellent anti-demagnetization ability.

[0141] The Tb diffusion weight gain ratio of the first transition region to the first easily demagnetized region in Comparative Example 1 is 0.5:1, which affects the Tb content in the main phase grain shell, the shell thickness, and the width of the transition region. All other aspects are the same as in Example 1. The coercivity ratio of the first transition region to the first easily demagnetized region of the NdFeB magnet in Comparative Example 1 is about 0.903:1, but the coercivity ratio of its non-easily demagnetized region to the first easily demagnetized region is relatively large, about 0.966:1. Moreover, the demagnetization rate of the NdFeB magnet prepared in Comparative Example 1 at 130°C is 18%, which is higher than that in Example 1, indicating that the demagnetization resistance of Comparative Example 1 is worse than that in Example 1.

[0142] In Comparative Example 2, Dy diffusion was not performed in the first easily demagnetized region, the second easily demagnetized region, the first transition region, the second transition region, and the non-easily demagnetized region. Tb diffusion was performed in the transition region and the easily demagnetized region. The coercivity ratio of the first transition region to the first easily demagnetized region of the neodymium iron boron magnet prepared in Comparative Example 2 was approximately 0.96:1. However, the coercivity ratio of the non-easily demagnetized region to the first easily demagnetized region was relatively low, approximately 0.635:1. Furthermore, the demagnetization rate of the neodymium iron boron magnet prepared in Comparative Example 2 at 130°C was as high as 26.9%, which was much higher than that of Examples 1-3, indicating that the demagnetization resistance of Comparative Example 2 was worse than that of the Examples.

[0143] The embodiments described above are merely preferred embodiments of the present invention, enabling those skilled in the art to understand and use the invention. Obviously, anyone skilled in the art can make slight modifications or variations to these embodiments without creative effort and apply them to other embodiments. Therefore, the present invention is not limited to the above embodiments, and any equivalent changes, simple modifications, and alterations made within the scope of the present invention still fall within its coverage.

Claims

1. A neodymium iron boron magnet, characterized in that, 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 Dy diffusion weight gain is the same in the first easily demagnetized region, the second easily demagnetized region, the non-easily demagnetized region, the first transition region, and the second transition region; The Dy diffusion weight gain in the first easily demagnetized region, the second easily demagnetized region, the non-easily demagnetized region, the first transition region, and the second transition region is 0.1wt%-1wt%; The Tb diffusion weight gain is the same in the first and second easily demagnetized regions. The Tb diffusion weight gain is the same in the first transition region and the second transition region; The Tb diffusion weight gain ratio between the first transition region and the first easily demagnetized region is (0.95-1):1; The Tb diffusion weight gain ratio between the non-demagnetizing region and the first demagnetizing region is (0-0.05):1; The Tb diffusion weight gain in the first easily demagnetized region is 0.1wt%-1wt%; The Tb diffusion weight gain in the non-demagnetizing region is 0.05 wt% or less.

2. The neodymium iron boron magnet as described in claim 1, characterized in that, The Dy diffusion weight gain in the first easily demagnetized region, the second easily demagnetized region, the non-easily demagnetized region, the first transition region, and the second transition region is 0.5 wt%, 0.6 wt%, or 0.7 wt%, respectively. And / or, the Tb diffusion weight gain in the first easily demagnetized region is 0.6 wt%; And / or, the Tb diffusion weight gain in the first transition region is 0.1wt%-1wt%; And / or, a first interface is formed between the first transition region and the first easily demagnetized region, and a second interface is formed between the second transition region and the second easily demagnetized region; Wherein, the Tb diffusion weight gain in the first interface and the second interface is the same; And / or, a third interface is formed between the first transition region and the non-demagnetizing region, and a fourth interface is formed between the second transition region and the non-demagnetizing region; The Tb diffusion weight gain at the third interface is the same as that at the fourth interface.

3. The neodymium iron boron magnet as described in claim 2, characterized in that, The Tb diffusion weight gain ratio between the first interface and the first easily demagnetized region is (0.95-1):1; And / or, the Tb diffusion weight gain ratio between the third interface and the center of the non-demagnetizing region is 1:(0-0.05).

4. The neodymium iron boron magnet as described in claim 1, characterized in that, 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 ≥ the coercivity of the first transition region is ≥ 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; And / or, the residual magnetism of the first easily demagnetized region is the same as that of the second easily demagnetized region, and the residual magnetism of the first transition region is the same as that of the second transition region; And / or, 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.

5. The neodymium iron boron magnet as described in claim 4, characterized in that, The coercivity ratio between the first transition zone and the first easily demagnetized zone is 0.97:1 or 0.98:1; 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. And / or, the remanence ratio of the first easily demagnetized region to the non-easily demagnetized region is (0.99-1):

1. And / or, the remanence ratio of the first transition region to the non-demagnetizing region is (0.99-1):

1. And / or, the width ratio of the first transition region to the width of the NdFeB magnet is (0-0.1):

1. And / or, the width ratio of the non-demagnetizing region to the width of the NdFeB 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 0-1 mm, and not 0.

6. The neodymium iron boron magnet as described in claim 4, characterized in that, The coercivity difference between the first easily demagnetized region and the non-easily demagnetized region is 2.6 kOe, 3.5 kOe, or 3.9 kOe; And / or, the coercivity ratio of the non-demagnetizing region to the first demagnetizing region is 0.85:1, 0.865:1, or 0.9:1; And / or, the remanence ratio of the first easily demagnetized region to the non-easily demagnetized region is 14.30:14.32 or 14.35:14.36; And / or, the remanence ratio of the first transition region to the non-demagnetizing region is 14.32:14.35, 14.33:14.35, or 14.36:14.38; And / or, the width ratio of the first transition region to the width of the NdFeB magnet is 0.093:1; And / or, the width ratio of the non-demagnetizing region to the width of the neodymium iron boron magnet is 0.527:

1.

7. The neodymium iron boron magnet as described in claim 1, characterized in that, The grain size of the main phase grains in the first easily demagnetized region is the same as that in the second easily demagnetized region, and the grain size of the main phase grains in the first transition region is the same as that in the second transition region; wherein, 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: first easily demagnetized region ≥ first transition region ≥ non-easily demagnetized region; 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; in the non-easily demagnetized region, the grain size of the surface main phase grains is 1-1.3 times the grain size of the central main phase grains; 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.

8. The neodymium iron boron magnet as described in claim 7, characterized in that, 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 main phase grains on the surface of the first easily demagnetized region is 1-12 μm; the grain size of the main phase grains on the surface of the first transition region is 1-12 μm; and the grain size of the main phase grains on the surface of the non-easily demagnetized region is 1-8 μm.

9. The neodymium iron boron magnet as described in claim 1, characterized in that, The grain boundary structure of the magnet includes Re2Fe 14 B-phase grains and Re-rich phase grain boundaries; the Re2Fe 14 B main phase grains include a main phase grain shell; Re is one or more of Nd, Dy and Tb; Wherein, the content of Tb in the main phase grain shell layer is the same in the first easily demagnetized region and the second easily demagnetized region; the content of Tb in the main phase grain shell layer is the same in the first transition region and the second transition region; the Tb content in the main phase grain shell layer of the first easily demagnetized region is ≥ the Tb content in the main phase grain shell layer of the first transition region. Specifically, 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; the thickness of the Re-rich grain boundary in the first easily demagnetized region is the same as the thickness of the Re-rich grain boundary in the second easily demagnetized region, and the thickness of the Re-rich grain boundary in the first transition region is the same as the thickness of the Re-rich grain boundary in the second transition region.

10. The neodymium iron boron magnet as described in claim 9, characterized in that, The ratio of Tb content in the non-demagnetizing region to that in the main phase grain shell of the first demagnetizing region is (0-0.05):(0.3-0.65). And / or, the ratio of Tb content in the first transition region to the main phase grain shell of the first easily demagnetized region is (0.2-0.65):(0.2-0.65); And / or, 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 first easily demagnetized region ≥ the first transition region ≥ the non-easily demagnetized region; And / or, in the first easily demagnetized region, the first transition region, and the non-easily demagnetized region, the thickness of the Re-rich grain boundary of the main phase grain satisfies: first easily demagnetized region ≥ first transition region ≥ non-easily demagnetized region; And / or, in the first easily demagnetized region, the thickness of the main phase grain shell is 0-4 μm; the thickness of the Re grain boundary is 0-1 μm, but not 0; the ratio of the thickness of the main phase grain shell to the thickness of the Re-rich grain boundary is (0.5-1.5):(0-1), but not 0; And / or, in the first transition region, the thickness of the main phase grain shell is 0-4 μm; the thickness of the Re-rich grain boundary is 0-1 μm, but not 0; the ratio of the thickness of the main phase grain shell to the thickness of the Re-rich grain boundary is (0.5-1.5):(0-1), but not 0; And / or, in the non-demagnetizing region, the thickness of the main phase grain shell is 0-2 μm; the thickness of the Re-rich grain boundary is 0-1 μm, but not 0; the ratio of the thickness of the main phase grain shell to the thickness of the Re-rich grain boundary is (0.5-1.5):(0-1), but not 0.

11. The neodymium iron boron magnet as described in claim 9, characterized in that, The ratio of Tb content in the non-demagnetizing region to the main phase grain shell of the first demagnetizing region is 0.02:0.60, 0.01:0.59, or 0.02:0.

57. And / or, the Tb content in the main phase grain shell of the first transition region and the first easily demagnetized region is 0.59:0.60, 0.58:0.59, or 0.57:0.57; And / or, in the first easily demagnetized region, the thickness of the main phase grain shell is 0.5-1.5 μm; And / or, in the first transition region, the thickness of the main phase grain shell is 0.5-1.5 μm; And / or, in the non-demagnetizing region, the thickness of the main phase grain shell is 0.5-1 μm.

12. The neodymium iron boron magnet as claimed in claim 1, characterized in that, The main phase grain shell of the first easily demagnetized region includes a first inner shell and a first outer shell; the main phase grain shell of the first transition region includes a second inner shell and a second outer shell; and the main phase grain shell of the non-easily demagnetized region includes a third inner shell.

13. The neodymium iron boron magnet as described in claim 12, characterized in that, The Tb diffusion weight gain of the first outer shell layer and the second outer shell layer satisfies: the first outer shell layer ≥ the second outer shell layer; And / or, the Tb diffusion weight gain in the first outer shell layer is 0.1wt%-0.9wt%; And / or, the Tb diffusion weight gain in the second outer shell layer is 0.1wt%-0.8wt%; And / or, the Dy diffusion weight gain of the first inner shell, the second inner shell, and the third inner shell satisfies: the third inner shell ≥ the second inner shell ≥ the first inner shell; And / or, the Dy diffusion weight gain in the first inner shell is 0.1wt%-0.9wt%; And / or, the Dy diffusion weight gain in the second inner shell is 0.1wt%-0.9wt%; And / or, the Dy diffusion weight gain in the third inner shell is 0.1wt%-0.9wt%; And / or, the thicknesses of the first outer shell layer and the second outer shell layer satisfy: the thickness of the first outer shell layer ≥ the thickness of the second outer shell layer; And / or, the thicknesses of the first inner shell, the second inner shell, and the third inner shell satisfy the following: the third inner shell ≥ the second inner shell ≥ the first inner shell; And / or, the thicknesses of the first inner shell layer and the first outer shell layer satisfy: the thickness of the first outer shell layer ≤ the thickness of the first inner shell layer; And / or, the thicknesses of the second inner shell layer and the second outer shell layer satisfy: the thickness of the second outer shell layer ≤ the thickness of the second inner shell layer; And / or, the thickness of the first inner shell layer is 0-2 μm; And / or, the thickness of the first outer shell layer is 0-2 μm; And / or, the thickness of the second inner shell layer is 0-2 μm; And / or, the thickness of the second outer shell layer is 0-2 μm; And / or, the thickness of the third inner shell layer is 0-2 μm.

14. The neodymium iron boron magnet as described in claim 12, characterized in that, The Tb diffusion weight gain in the first outer shell layer is 0.6 wt%; And / or, the Tb diffusion weight gain in the second outer shell layer is 0.6 wt%; And / or, the Dy diffusion weight gain in the first inner shell is 0.5wt%, 0.6wt%, or 0.7wt%; And / or, the Dy diffusion weight gain in the second inner shell is 0.5wt%, 0.6wt%, or 0.7wt%; And / or, the Dy diffusion weight gain in the third inner shell is 0.5wt%, 0.6wt%, or 0.7wt%; And / or, the thickness of the first inner shell layer is 1.8 μm or 1.9 μm; And / or, the thickness of the first outer shell layer is 1.7 μm, 1.8 μm, or 1.9 μm; And / or, the thickness of the second inner shell is 1.8 μm or 1.9 μm; And / or, the thickness of the second outer shell layer is 1.6 μm or 1.7 μm; And / or, the thickness of the third inner shell layer is 1.8 μm or 1.9 μm.

15. The neodymium iron boron magnet as described in claim 12, characterized in that, The main phase grain shell of the non-demagnetizing region also includes a third outer shell layer.

16. The neodymium iron boron magnet as described in claim 15, characterized in that, The Tb diffusion weight gain in the third outer shell of the main phase grain shell in the non-demagnetizing region is 0-0.05 wt%. And / or, the Tb diffusion weight gain of the first outer shell layer, the second outer shell layer, and the third outer shell layer satisfies: first outer shell layer ≥ second outer shell layer > third outer shell layer; And / or, the thicknesses of the first outer shell layer, the second outer shell layer, and the third outer shell layer satisfy the following condition: first outer shell layer ≥ second outer shell layer > third outer shell layer; And / or, the thicknesses of the third inner shell and the third outer shell in the principal phase grain shell of the non-demagnetizing region satisfy the following: the thickness of the third inner shell is greater than that of the third outer shell. And / or, the thickness of the third outer shell layer of the main phase grain shell layer in the non-demagnetizing region is 0-0.5 μm.

17. The method for preparing a neodymium iron boron magnet according to any one of claims 1-16, characterized in that, A diffusion source is applied to a NdFeB substrate along a first easily demagnetized region, a first transition region, a non-easily demagnetized region, a second transition region, and a second easily demagnetized region distributed perpendicular to the orientation direction, and grain boundary diffusion parallel to the orientation direction is performed to obtain the NdFeB magnet; the diffusion source contains Dy and / or Tb.

18. A neodymium iron boron magnet prepared by the method for preparing neodymium iron boron magnets according to claim 17.

19. An application of a neodymium iron boron magnet as described in any one of claims 1-16 or 18 in magnetic steel.

Images