High-resistivity ndfeb permanent magnet material and high-throughput preparation method thereof

Abstract

This invention discloses a high-resistivity NdFeB permanent magnet material and its high-throughput preparation method. Specifically, the method includes: preparing a metal cladding of suitable size; assembling NdFeB, NdDyTbFeB metal strips and rare-earth alloy diffusion source strips into grooves within the metal cladding using an alternating arrangement of the metal strips and diffusion source strips; performing vacuum electron beam welding and hot isostatic pressing; slicing and sealing the resulting multi-element section before heat treatment; and finally, screening to obtain the high-resistivity NdFeB permanent magnet material. This invention, based on a high-throughput preparation method for diffusion multi-element sections, can obtain a large number of parallel samples in a short time. Combined with high-throughput testing and characterization methods, it allows for rapid screening of suitable diffusion sources and heat treatment temperatures, enabling efficient development of high-resistivity NdFeB permanent magnet materials.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnets, specifically to a high resistivity NdFeB permanent magnet material and its high-throughput preparation method. Background Technology

[0002] As the social energy structure continues to optimize, the demand for permanent magnet materials in low-carbon economic sectors such as energy-saving home appliances, new energy vehicles, and wind power generation will increase significantly. Permanent magnet motors are more favored by the market than excitation motors due to their advantages in high efficiency, low energy consumption, good stability, and weight and size. With the rapid development of the low-carbon economy and its increasingly widespread applications, the market is placing higher performance demands on permanent magnet motors, urgently requiring the development of safer, more reliable, and more efficient permanent magnet motors.

[0003] NdFeB permanent magnets are the preferred permanent magnet for permanent magnet motors. Permanent magnet synchronous traction motors for new energy vehicles and permanent magnet synchronous generators for wind turbines often operate in environments with temperatures reaching 150℃ or even 250℃. However, due to the low Curie temperature of NdFeB magnets (approximately 312℃), conventional NdFeB magnets are prone to thermal demagnetization under such high temperatures, leading to a decrease in their magnetic properties and compromising the efficient operation of the permanent magnet motor. Currently, methods to improve their coercivity often involve adding expensive and scarce heavy rare earth elements such as Dy and Tb, significantly increasing costs. Adding water-cooling devices can also reduce rotor temperature, but this limits the motor's structural design and cannot fundamentally solve the material problem.

[0004] The heat generation of a rotor is primarily determined by its resistivity. Introducing high-resistivity scattering elements into NdFeB can increase electron scattering efficiency and reduce heat generation. Current research often involves introducing insulating oxide particles containing Si, Zn, and Sn to increase resistivity, but this inevitably leads to a significant decrease in magnetic properties. Grain boundary diffusion, which forms continuous rare-earth oxide grain boundary phases along the main phase boundary layer, can improve resistivity while maintaining coercivity. Therefore, grain boundary diffusion is a viable method for the research and preparation of high-resistivity NdFeB permanent magnet materials. However, grain boundary diffusion relies heavily on experiments, requiring the exploration of suitable diffusion substrates and source compositions, as well as optimal diffusion processes, to obtain high-resistivity NdFeB permanent magnet materials that meet practical application requirements. This process demands substantial human, material, and financial resources, significantly limiting the development of high-resistivity NdFeB permanent magnet materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-resistivity NdFeB permanent magnet material and its high-throughput preparation method. This invention employs a high-throughput experimental method, obtaining a large number of parallel samples in a short time by preparing multi-element nodes. Combined with high-throughput testing and characterization methods, experimental efficiency can be effectively improved. By using a diffusion multi-element node method and applying thermal isostatic pressing, a tight bond between interfaces can be achieved, resulting in higher mechanical properties. Through the rational design of the diffusion layer composition, heavy rare earth elements diffuse into the main phase to form a core-shell structure, improving the wettability and resistivity of the grain boundary phase, thereby increasing the overall resistivity without sacrificing magnetic properties.

[0006] The high-throughput preparation method of high-resistivity NdFeB permanent magnet material provided by this invention includes the following steps:

[0007] (1) Prepare an elongated elliptical sleeve with length, width and height dimensions of l*m*n and a cap with length, width and height dimensions of l*m*k, and machine a rectangular groove in the sleeve;

[0008] (2) Prepare a magnet strip M with length, width and height dimensions of a*b*d and a diffusion source strip T with length, width and height dimensions of a*c*d, and perform surface grinding and polishing treatment; wherein in millimeters, 10≥a≥3, 10≥b≥3, c≥0.5, d≥3;

[0009] (3) Assemble the magnet strip and the diffusion source strip alternately into the rectangular groove, cover it, and perform vacuum electron beam welding;

[0010] (4) The welded sheath is subjected to hot isostatic pressing to obtain a diffusion multi-element joint;

[0011] (5) Cut the diffusion multi-section into multiple pieces parallel to the long elliptical surface, seal the tube, and perform diffusion heat treatment at different temperatures or times according to the requirements of subsequent experiments to obtain multiple sets of high resistivity NdFeB permanent magnet material diffusion multi-sections under different heat treatment conditions.

[0012] (6) The resistivity and magnetic properties of each interface of the diffusion multi-component joint of the obtained NdFeB permanent magnet material are tested, and the interface that meets the requirements of resistivity and magnetic properties is selected. Based on the component composition on both sides of the interface and the corresponding heat treatment conditions, the high resistivity NdFeB permanent magnet material with the required performance can be prepared. The resistivity and magnetic property requirements are determined according to the subsequent application requirements. After obtaining the component composition on both sides of the interface, the corresponding magnet composition and diffusion source composition can be selected, and the material can be processed according to the powder metallurgy preparation process and corresponding heat treatment conditions known in the art.

[0013] Furthermore, in step (1), the cladding material is one of 304 stainless steel, pure iron, or Cr metal.

[0014] Furthermore, the magnet strip M in step (2) can be selected from one or more of NdFeB magnets and NdDyTbFeB magnets, wherein the composition of the NdFeB magnet is: (Nd x Pr y A z D 1-x-y-z ) a Fe bal M c B e Nd represents neodymium, Pr represents praseodymium, A represents one or more rare earth elements La, Ce, and Y, D represents one or more rare earth elements other than Dy, Tb, Nd, Pr, La, Ce, and Y, Fe represents iron, B represents boron, and M represents one or more rare earth elements Al, Ga, Cu, Ti, Cr, Mn, Mo, Nb, P, Si, Ta, V, Zr, Ni, and Co; the composition of the NdDyTbFeB magnet is: (Nd x’ Pr y’ R z’ E 1-x’-y’-z’ ) b Fe bal N d B f R represents one or two rare earth elements Dy and Tb; E represents one or more rare earth elements other than Dy, Tb, Nd, Pr, La, Ce, and Y; N represents one or more rare earth elements Al, Ga, Cu, Ti, Cr, Mn, Mo, Nb, P, Si, Ta, V, Zr, Ni, and Co; calculated as a mass percentage, satisfying 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.8, 28.5≤a≤33.5, 0.3≤c≤6, 0.85≤e≤1.5, 0.5≤x'≤1, 0≤y'≤0.4, 0.05≤z'≤0.5, 27≤b≤33.5, 0.2≤d≤6, and 0.85≤f≤1.5; bal indicates that all remaining elements are Fe after removing other elements.

[0015] Furthermore, the diffusion source strip T in step (2) can be selected from S. g Fe bal Q h S t One or more of the following, where S is one or more rare earth elements Dy, Tb, Nd, Pr, Gd, Ho, Fe is iron, Q is one or more of Al, Ga, Cu, Ni, Co; S is one or more of Sn, Si, Zn, Zr, Pb; satisfying 0.5≤g≤0.8, 0.05≤h≤0.45, 0.05≤t≤0.45, and bal means that all the remaining elements are Fe.

[0016] When there are multiple magnet strips M or diffusion source strips T with different compositions, the principle of alternating arrangement of magnet strips M and diffusion source strips T is still followed. That is, regardless of whether the composition of magnet strips M is the same or different, two magnet strips M need to be separated by a diffusion source strip T, and similarly, two diffusion source strips T also need to be separated by a magnet strip M.

[0017] Furthermore, the vacuum degree of vacuum electron beam welding in step (3) is 5*10 -5 ~5*10 -4 Pa, the weld width is 0.5~1.5mm.

[0018] Furthermore, the hot isostatic pressing treatment in step (4) is performed at a temperature of 650–1000℃ for 2–5 hours and at a pressure of 50–300 MPa.

[0019] Furthermore, the sealing tube in step (5) is in an argon atmosphere of 0.03–0.06 MPa. Furthermore, the diffusion heat treatment time in step (5) is 2–30 days, and the diffusion heat treatment temperature is 800–1100 °C.

[0020] This invention further provides NdFeB permanent magnet materials prepared by the method described above. The method of this invention can quickly determine the composition and heat treatment conditions of NdFeB permanent magnet materials that meet the requirements of high resistivity and magnetic properties.

[0021] The beneficial effects of this invention compared to the prior art are as follows:

[0022] 1) This invention rapidly understands the influence of different diffusion sources on the resistivity of permanent magnets by preparing diffusion multi-component nodes with different compositions, and efficiently prepares permanent magnet materials with high magnetic properties and high resistivity.

[0023] 2) This invention can quickly grasp the diffusion thermodynamics of the diffusion source in the magnet at different temperatures and times by using different heat treatment temperatures and times, and efficiently screen suitable heat treatment processes.

[0024] 3) This invention adopts a high-throughput experimental method, which can obtain a large number of samples through a single experiment and obtain a large amount of data through centralized parallel testing and characterization. Compared with the traditional experimental trial and error method, it can significantly improve the research and development efficiency of high resistivity permanent magnet materials.

[0025] 4) The prepared multi-element nodes form a shell rich in Dy / Tb in the main phase of the magnet through heat treatment, which improves the coercivity; at the same time, a continuous and high resistivity grain boundary phase (mainly rich in rare earth compounds) is formed, which improves the overall resistivity of the magnet. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the diffusion multi-element joint arrangement for a high resistivity permanent magnet material. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments:

[0028] Example 1:

[0029] (1) Prepare a size of 30*18*45mm 3 The elongated oval-shaped sleeve measures 30*18*1mm. 3 The lid, with a long oval sleeve, is machined to measure 21*13*40mm. 3 The rectangular groove is made of 304 stainless steel.

[0030] (2) Prepare a size of 21*2.5*40mm 3 (Nd) 0.65 Pr 0.15 Ce 0.2 ) 30 Fe bal Al 0.2 Ga 0.5 Nb 0.2 B1 magnet strip, 21*1*40mm 3 Nd 0.6 Cu 0.25 Sn 0.1 Si 0.05 、Nd 0.6 Cu 0.25 Sn 0.15 、Nd 0.6 Cu 0.35 Si 0.05 Diffusion source strips, surface sanded and polished with a polishing machine;

[0031] (3) Alternately assemble the four magnet strips and three diffusion source strips into the rectangular slot (separate the two magnet strips with one diffusion source strip, and separate the two diffusion source strips with one magnet strip, such as...). Figure 1 (As shown), cover and perform vacuum electron beam welding; the vacuum degree for vacuum electron beam welding is 5*10. -4 Pa, weld width is 0.5mm;

[0032] (4) The welded sheath is subjected to hot isostatic pressing to obtain a diffusion multi-element joint; the hot isostatic pressing temperature is 750℃, the time is 4h, and the pressure is 200MPa.

[0033] (5) The multi-section was cut into 8 pieces parallel to the long elliptical surface and sealed into tubes. After sealing, the tubes were divided into 4 temperature groups (two pieces in each group) and subjected to diffusion heat treatment at four different temperatures of 800℃, 900℃, 1000℃ and 1100℃. The diffusion heat treatment time for the two pieces in each group was 7 days and 15 days, respectively, to obtain 8 high resistivity NdFeB permanent magnet materials. The partial resistivity of these materials is shown in Table 1 below. Since the magnet strips have the same composition, the interfaces in Table 1 are represented by diffusion sources.

[0034] (6) Based on a comprehensive consideration of the composition, corresponding resistivity, and magnetic properties, (Nd) was finally selected. 0.65 Pr 0.15 Ce 0.2 ) 30 Fe bal Al 0.2 Ga 0.5 Nb 0.2 B1 / Nd 0.6 Cu 0.25 Sn 0.1 Si 0.05 Interface, heat treatment temperature 900℃, time 15 days, through (Nd) 0.65 Pr 0.15 Ce 0.2 ) 30 Fe bal Al 0.2 Ga 0.5 Nb 0.2 Add Nd to B1 0.6 Cu 0.25 Sn 0.1 Si 0.05 High resistivity sintered permanent magnets were produced.

[0035] Table 1

[0036] diffusion source Temperature / °C Time / day Interfacial resistivity / μΩ·cm <![CDATA[Nd 0.6 With 0.25 Sn 0.1 And 0.05 ]]> 800 7 1003 <![CDATA[Nd 0.6 With 0.25 Sn 0.1 And 0.05 ]]> 800 15 1218 <![CDATA[Nd 0.6 With 0.25 Sn 0.1 And 0.05 ]]> 900 7 7309 <![CDATA[Nd 0.6 With 0.25 Sn 0.1 And 0.05 ]]> 900 15 8215 <![CDATA[Nd 0.6 With 0.25 Sn 0.15 ]]> 900 7 8012 <![CDATA[Nd 0.6 With 0.35 And 0.05 ]]> 900 15 6547

[0037] Example 2:

[0038] (1) Prepare a size of 32*20*51mm 3 The elongated oval-shaped sleeve measures 32*20*1mm. 3 The lid, with a long oval sleeve, is machined to measure 24*17*45mm. 3 The rectangular groove is made of 304 stainless steel.

[0039] (2) Prepare a size of 24*3.5*45mm 3 (Nd 0.85 Pr 0.1 Dy 0.05 ) 30.5 Fe bal Al0.15 Ga 0.45 Co 0.2 Zr 0.15 B 0.95 Magnet strip, 24*1*45mm 3 Nd 0.6 Tb 0.1 Fe 0.1 Cu 0.15 Si 0.05 、Nd 0.55 Tb 0.1 Fe 0.1 Cu 0.15 Si 0.1 、Nd 0.5 Tb 0.1 Fe 0.1 Cu 0.15 Si 0.15 Diffusion source strips, surface sanded and polished with a polishing machine;

[0040] (3) Alternately assemble the four magnet strips and three diffusion source strips into the rectangular slot (separate the two magnet strips with one diffusion source strip, and separate the two diffusion source strips with one magnet strip, such as...). Figure 1 (As shown), cover and perform vacuum electron beam welding; the vacuum degree for vacuum electron beam welding is 5*10. -5 Pa, weld width is 1.5mm;

[0041] (4) The welded sheath is subjected to hot isostatic pressing to obtain a diffusion multi-element joint; the hot isostatic pressing temperature is 650℃, the time is 2h, and the pressure is 50MPa.

[0042] (5) The multi-section was cut into 10 pieces parallel to the long elliptical surface and sealed into tubes. After sealing, the tubes were divided into 5 temperature groups (two pieces in each group) and subjected to diffusion heat treatment at five different temperatures of 900℃, 950℃, 1000℃, 1050℃ and 1100℃. The diffusion heat treatment time for the two pieces in each group was 7 days and 15 days, respectively. The cooling method was quenching. Ten high resistivity NdFeB permanent magnet materials were obtained. The partial resistivity test results are shown in Table 2 below. Since the magnet strips have the same composition, the interfaces are represented by diffusion sources in Table 2.

[0043] (6) Based on a comprehensive consideration of the composition, corresponding resistivity, and magnetic properties, (Nd) was finally selected. 0.85 Pr 0.1 Dy 0.05 ) 30.5 Fe bal Al 0.15 Ga 0.45 Co 0.2 Zr 0.15 B 0.95 / Nd 0.55 Tb 0.1 Fe 0.1 Cu 0.15 Si 0.1 Interface, heat treatment temperature 1050℃, time 7 days, through (Nd 0.85 Pr 0.1 Dy 0.05 ) 30.5 Fe bal Al 0.15 Ga 0.45 Co 0.2 Zr 0.15 B 0.95 Add Nd 0.55 Tb 0.1 Fe 0.1 Cu 0.15 Si 0.1 High resistivity sintered permanent magnets were produced.

[0044] Table 2

[0045]

[0046] Example 3:

[0047] (1) Prepare a size of 32*20*51mm 3 The elongated oval-shaped sleeve measures 32*20*1mm. 3 The lid, with a long oval sleeve, is machined to measure 24*17*45mm. 3 The rectangular groove is made of 304 stainless steel.

[0048] (2) Prepare a size of 24*3.5*45mm 3 (Nd) 0.8 Pr 0.1 Dy 0.1 ) 30.5 Fe bal Cu 0.25 Al 0.25 Ga 0.5 Co 0.5 Ti 0. 2B 0.95 、(Nd 0.65 Pr 0.15 Dy 0.2 ) 30.5 Fe bal Al 0.15 Ga 0.5 Co 0.6 Ti 0.3 B 0.92 、(Nd 0.75 Pr 0.1 Dy 0.15) 31 Fe bal Al 0.25 Ga 0.35 Nb 0.2 B1、(Nd 0.6 Pr 0.1 Dy 0.3 ) 31.5 Fe bal Cu 0.25 Al 0.25 Ga 0.35 Co 0.5 Ti 0.25 B 0.98 Magnet strip, 24*1*45mm 3 Nd 0.5 Zn 0.39 Sn 0.06 Cu 0.025 Al 0.025 Diffusion source strips, surface sanded and polished with a polishing machine;

[0049] (3) Alternately assemble the four magnet strips and three diffusion source strips into the rectangular slot (separate the two magnet strips with one diffusion source strip, and separate the two diffusion source strips with one magnet strip, such as...). Figure 1 (As shown), cover and perform vacuum electron beam welding; the vacuum degree for vacuum electron beam welding is 5*10. -5 Pa, weld width is 1mm;

[0050] (4) The welded sheath is subjected to hot isostatic pressing to obtain a diffusion multi-element joint; the hot isostatic pressing temperature is 650℃, the time is 2h, and the pressure is 50MPa.

[0051] (5) The multi-section was cut into 10 pieces parallel to the long elliptical surface and sealed into tubes. After sealing, the tubes were divided into 5 temperature groups (two pieces in each group) and subjected to diffusion heat treatment at five different temperatures of 900℃, 950℃, 1000℃, 1050℃ and 1100℃. The diffusion heat treatment time for the two pieces in each group was 5 days and 10 days, respectively. The cooling method was quenching. Ten high resistivity NdFeB permanent magnet materials were obtained. The partial resistivity test results are shown in Table 3 below. Since the diffusion strips have the same composition, each interface is represented by a magnet in Table 3.

[0052] (6) Based on a comprehensive consideration of the composition, corresponding resistivity, and magnetic properties, (Nd) was finally selected. 0.65 Pr 0.15 Dy 0.2 ) 30.5 Fe bal Al 0.15 Ga 0.5 Co 0.6 Ti0.3 B 0.92 / Nd 0.5 Zn 0.39 Sn 0.06 Cu 0.025 Al 0.025 Interface, heat treatment temperature 1050℃, time 5 days, through (Nd 0.65 Pr 0.15 Dy 0.2 ) 30.5 Fe bal Al 0.15 Ga 0.5 Co 0.6 Ti 0.3 B 0.92 Add Nd 0.5 Zn 0.39 Sn 0.06 Cu 0.025 Al 0.025 High resistivity sintered permanent magnets were produced.

[0053] Table 3

[0054]

[0055] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A high-throughput preparation method for high resistivity NdFeB permanent magnet materials, characterized in that, Includes the following steps: (1) Prepare an elongated elliptical sleeve with length, width and height dimensions of l×m×n and a cap with length, width and height dimensions of l×m×k, and machine a rectangular groove in the sleeve; (2) Prepare a magnet strip M with length, width and height dimensions of a×b×d, prepare a diffusion source strip T with length, width and height dimensions of a×c×d, and perform surface grinding and polishing treatment; In millimeters, 10≥a≥3, 10≥b≥3, c≥0.5, d≥3; In step (2), the magnet strip M is selected from one or more of NdFeB magnets and NdDyTbFeB magnets, wherein the composition of the NdFeB magnet is: (Nd x Pr y A z D 1-x-y-z ) a Fe bal M c B e Nd represents neodymium, Pr represents praseodymium, A represents one or more rare earth elements La, Ce, and Y, D represents one or more rare earth elements other than Dy, Tb, Nd, Pr, La, Ce, and Y, Fe represents iron, B represents boron, and M represents one or more rare earth elements Al, Ga, Cu, Ti, Cr, Mn, Mo, Nb, P, Si, Ta, V, Zr, Ni, and Co; the composition of the NdDyTbFeB magnet is: (Nd x’ Pr y’ R z’ E 1-x’-y’-z’ ) b Fe bal N d B f R is one or two elements from rare earth elements Dy and Tb; E is one or more elements from other rare earth elements besides Dy, Tb, Nd, Pr, La, Ce, and Y; N is one or more elements from Al, Ga, Cu, Ti, Cr, Mn, Mo, Nb, P, Si, Ta, V, Zr, Ni, and Co; calculated as a mass percentage, satisfying 0.2≤x≤1, 0≤y≤0.5, 0≤z≤0.8, 28.5≤a≤33.5, 0.3≤c≤6, 0.85≤e≤1.5, 0.5≤x'≤1, 0≤y'≤0.4, 0.05≤z'≤0.5, 27≤b≤33.5, 0.2≤d≤6, and 0.85≤f≤1.

5. Diffusion source T is selected from S g Fe bal Q h Z t One or more of the following elements are present: S is one or more rare earth elements Dy, Tb, Nd, Pr, Gd, Ho; Fe is iron; Q is one or more of Al, Ga, Cu, Ni, Co; Z is one or more of Sn, Si, Zn, Zr, Pb; and the following conditions are met: 0.5≤g≤0.8, 0.05≤h≤0.45, 0.05≤t≤0.

45. (3) Assemble the magnet strip and the diffusion source strip alternately into the rectangular groove, cover it, and perform vacuum electron beam welding; (4) The welded sheath is subjected to hot isostatic pressing to obtain a diffusion multi-element joint; the hot isostatic pressing temperature is 650~1000 ℃, the time is 2~5 h, and the pressure is 50~300 MPa. (5) Cut the diffusion multi-section into multiple pieces parallel to the long elliptical surface, seal the tube and perform diffusion heat treatment at different temperatures or times according to the requirements of subsequent experiments to obtain multiple groups of high resistivity NdFeB permanent magnet material diffusion multi-sections under different heat treatment conditions; the diffusion heat treatment time is 2~30 days and the diffusion heat treatment temperature is 800~1100 ℃. (6) The resistivity and magnetic properties of each interface of the diffusion multi-component joint of the obtained NdFeB permanent magnet material are tested, and the interface that meets the requirements of resistivity and magnetic properties is selected; NdFeB permanent magnet material is prepared according to the component composition on both sides of the interface and the corresponding heat treatment conditions.

2. The method according to claim 1, characterized in that, In step (1), the cladding material is one of 304 stainless steel, pure iron, or Cr metal.

3. The method according to claim 1, characterized in that, The vacuum degree of vacuum electron beam welding in step (3) is 5×10 -5 ~5×10 -4 Pa, the weld width is 0.5~1.5 mm.

4. The method according to claim 1, characterized in that, The sealing tube in step (5) is in an argon atmosphere of 0.03~0.06 MPa.

5. The high resistivity NdFeB permanent magnet material prepared by the method according to any one of claims 1-4.

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