Neodymium-iron-boron permanent magnet containing lanthanum and cerium and preparation method of neodymium-iron-boron permanent magnet

Abstract

The chemical formula of the neodymium-iron-boron permanent magnet is (PrhNdi) aLabCecBdCueCofMgFe100-a-b-c-d-e-f-g, M is a combination of at least one element of Al, Cr, Nb, Zr, Ti, Mn, Zn, V and Mo and Ga, 27.2 < = a < = 29.5, 0.5 < = b < = 3.0, 0.5 < = c < = 3.0, 0.9 < = d < = 1.0, 0.1 < = e < = 1.5, 0.1 < = f < = 1.5, 0.1 < = g < = 1.5, 23 < = h < = 28, 72 < = i < = 77, a main phase in a microstructure is (Pr, Nd, La and Ce) FeB, and Ce is enriched in a grain boundary phase. Through collaborative optimization design of components and microstructures, efficient utilization of high-abundance rare earth elements is achieved, adding of main rare earth elements is reduced, on the premise that cost is not increased, the magnetic performance of the permanent magnet is remarkably improved, and the neodymium-iron-boron permanent magnet with the high Curie temperature and the high thermal stability is obtained. The comprehensive performance of the permanent magnet is improved, and the permanent magnet has the important cost advantage and industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials, specifically relating to a neodymium iron boron permanent magnet containing lanthanum and cerium and its preparation method. Background Technology

[0002] Rare earth permanent magnet materials are widely used in new energy vehicles, wind power generation, energy-saving variable frequency air conditioners, elevator traction machines, 3C electronic products, intelligent manufacturing, and high-end equipment manufacturing. However, with the expansion of application areas and the increase in demand for rare earth permanent magnet materials, the overuse of major rare earth elements (Pr, Nd, Gd, Ho) and the stockpiling of high-abundance rare earth elements (La, Ce, Y) are becoming increasingly prominent. This not only makes the supply of rare earth resources tighter but also has a profound impact on the development of the rare earth permanent magnet material industry. Against this backdrop, research on how to partially replace major rare earth elements (Pr, Nd, Gd, Ho) through the efficient utilization of high-abundance rare earth elements (La, Ce, Y) has attracted much attention.

[0003] Studies have shown that Ce, a highly abundant rare earth element, exhibits great potential in replacing major rare earth elements due to its excellent cost-effectiveness and magnetic properties. Specifically, Ce's anisotropic field (HA = 3600 kA / m) is close to that of Pr / Nd (HA = 5660 kA / m), while also possessing a significant cost advantage, making it a preferred replacement element for major rare earth elements (Pr, Nd, Gd, Ho). However, in practical applications, it has been found that the introduction of large amounts of Ce drastically deteriorates the Curie temperature and thermal stability of rare earth permanent magnet materials and reduces the remanence temperature coefficient. This characteristic severely restricts the proportion of Ce added to high-performance permanent magnet materials, especially in fields with high requirements for Curie temperature and thermal stability. Improving the Curie temperature and thermal stability of rare earth permanent magnet materials without increasing costs or affecting their magnetic properties, while simultaneously promoting the balanced utilization of rare earth resources, has become a key technological path for the sustainable development of the rare earth permanent magnet material industry. Therefore, this invention proposes a neodymium iron boron permanent magnet containing lanthanum and cerium and its preparation method. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a lanthanum-cerium-containing neodymium iron boron permanent magnet with a low remanence temperature coefficient and its preparation method, in order to address the shortcomings of the prior art. Through the synergistic optimization design of composition and microstructure, the high-abundance rare earth elements La and Ce are efficiently utilized, the addition of major rare earth elements is reduced, and the magnetic properties of the permanent magnet are significantly improved without increasing the cost, resulting in a neodymium iron boron permanent magnet with high Curie temperature and high thermal stability.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problem is: a neodymium iron boron permanent magnet containing lanthanum and cerium, wherein the chemical formula of the neodymium iron boron permanent magnet is: (Pr hNd i ) a La b Ce c B d Cu e Co f M g Fe 100-a-b-c-d-e-f-g Where M is a combination of at least one element selected from Al, Cr, Nb, Zr, Ti, Mn, Zn, V, and Mo with Ga, and a, b, c, d, e, f, g, and 100-abcdefg are Pr h Nd i The mass percentages of La, Ce, B, Cu, Co, M, and Fe in this NdFeB permanent magnet, and h and i, respectively, represent the mass percentages of Pr and Nd in Pr. h Nd i The mass percentages of the NdFeB permanent magnet are 27.2≤a≤29.5, 0.5≤b≤3.0, 0.5≤c≤3.0, 0.9≤d≤1.0, 0.1≤e≤1.5, 0.1≤f≤1.5, 0.1≤g≤1.5, 23≤h≤28, and 72≤i≤77. The main phase in the microstructure of this NdFeB permanent magnet is (Pr,Nd,La,Ce)FeB, with Ce enriched in the grain boundary phase.

[0006] This invention simultaneously adds Ce and La to neodymium iron boron permanent magnets. By partially replacing Ce with La and introducing a specific proportion of M, the addition of major rare earth elements is reduced while the addition of high-abundance rare earth elements is increased. Without increasing costs, the magnetic properties of the permanent magnets are significantly improved, resulting in neodymium iron boron permanent magnets with high Curie temperature and high thermal stability.

[0007] In the neodymium iron boron permanent magnet of this invention, La can form La2Fe with Fe and B. 14 Phase B, La2Fe 14 The Curie temperature of phase B is 530 K, significantly higher than that of Ce₂Fe. 14 The Curie temperature of the B phase is 424 K, therefore, under high-temperature conditions, La2Fe 14 The B phase exhibits stronger resistance to thermal disturbances, which is beneficial for maintaining a higher degree of magnetic moment order in permanent magnets, reducing magnetic attenuation, and improving thermal stability. Meanwhile, La2Fe... 14 The saturation magnetic polarization of phase B reaches 1.38T, which is higher than that of Ce2Fe. 14 The saturation magnetic polarization of phase B is 1.17T. Under comparable cost conditions, the addition of La to NdFeB permanent magnets can achieve higher remanence (Br) without reducing the coercivity (Hcj) of the permanent magnet, thus effectively reducing the remanence temperature coefficient of NdFeB permanent magnets.

[0008] The main phase in the microstructure of the NdFeB permanent magnet of this invention is (Pr, Nd, La, Ce)FeB, with Ce enriched in the grain boundary phase. This invention partially substitutes Ce with La, and the SEM analysis of the microstructure did not observe the harmful CeFe2 phase with typical black contrast, indicating that it did not negatively affect the magnet's coercivity. Meanwhile, EDS analysis confirmed that Ce is significantly enriched in the grain boundary phase. This enrichment enhances the wettability and improves the continuity of the grain boundary phase, ultimately promoting the improvement of the magnet's coercivity. Meanwhile, La exhibits a relatively uniform distribution throughout the magnet and is incorporated into the main phase, and due to the La2Fe... 14 B compared to Ce2Fe 14 B has a higher saturation magnetization and Curie temperature. Therefore, a higher proportion of La enters the main phase, effectively increasing the magnetization of the (Pr,Nd,La,Ce)FeB main phase, thereby improving the magnetic properties of the permanent magnet, such as magnetization, temperature stability, and remanence temperature coefficient. It is noteworthy that, under specific compositional ratios, the La / Ce ratio in the main phase is significantly higher than that in the grain boundary phase. Simultaneously, La exhibits a relatively higher tendency for solid solution in the main phase.

[0009] Preferably, in this neodymium iron boron permanent magnet, the mass percentage ratio of Cu to Ga is Cu:Ga = (1~9):(1~6), and the mass percentage ratio of Ce to La is Ce:La = (1~3):(1~3).

[0010] Preferably, in this neodymium iron boron permanent magnet, 27.5≤a≤28.1, 0.5≤b≤1.5, 0.5≤c≤1.5, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 0.1≤g≤0.5, the mass percentage ratio of Cu to Ga is Cu:Ga=3:2, and the mass percentage ratio of Ce to La is Ce:La=1:1 or 3:2.

[0011] Preferably, in this neodymium iron boron permanent magnet, 28.5≤a≤29.5, 1.0≤b≤2.5, 0.5≤c≤1.5, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 0.25≤g≤0.8, the mass percentage ratio of Cu to Ga is Cu:Ga=9:5, and the mass percentage ratio of Ce to La is Ce:La=2:3 or 3:2.

[0012] Preferably, in this neodymium iron boron permanent magnet, 28.8≤a≤29.5, 0.5≤b≤1.5, 0.5≤c≤1.5, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 0.1≤g≤0.5, the mass percentage ratio of Cu to Ga is Cu:Ga=3:2, and the mass percentage ratio of Ce to La is Ce:La=3:1 or 3:2.

[0013] Preferably, in this neodymium iron boron permanent magnet, 27.2≤a≤28.0, 2.0≤b≤3.0, 2.0≤c≤3.0, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 1.0≤g≤1.5, the mass percentage ratio of Cu to Ga is Cu:Ga=1.12:1, and the mass percentage ratio of Ce to La is Ce:La=2:3 or 3:2.

[0014] The preparation method of the above-mentioned neodymium iron boron permanent magnet containing lanthanum and cerium includes the following steps:

[0015] 1) Based on the chemical formula of neodymium iron boron permanent magnets (Pr h Nd i ) a La b Ce c B d Cu e Co f M g Fe 100-a-b-c-d-e-fg Calculate and weigh the raw materials according to the designed composition ratio, and place the raw materials into the crucible in the rapid solidification furnace in sequence. Under the protection of argon atmosphere, at 1480±20℃ and a vacuum degree of (2~10)×10 -2 Induction melting under Pa conditions, followed by rapid quenching and spinning at 1425±20℃ to produce a rapidly solidified sheet with a thickness of 0.28±0.05mm;

[0016] 2) The obtained rapid solidification casting sheet is placed in a hydrogen crushing furnace. First, hydrogen is absorbed under a pressure of 0-2 MPa for 2-4 hours. Then, hydrogen is removed at a temperature of 500-600℃ for 6-10 hours. Finally, it is cooled to obtain coarse powder.

[0017] 3) Add 0.05-0.1% of antioxidant by weight of the obtained coarse powder, stir evenly, and then perform air jet milling under nitrogen protection atmosphere to obtain fine powder with a particle size of 3.8±0.1μm;

[0018] 4) Add 0.05-0.1% of lubricant by weight of the fine powder to the obtained fine powder, stir evenly, first shape it in a magnetic field strength of 1.5-2.2T and a nitrogen protective atmosphere, and then perform isostatic pressing under a pressure of 140-220MPa to obtain a green body.

[0019] 5) The obtained green blank is vacuum sintered at a sintering temperature of 1045-1065℃ and a holding time of 6-10h, followed by two-stage aging treatment. The first stage of aging treatment is carried out at a temperature of 850-920℃ and a holding time of 3-5h, and the second stage of aging treatment is carried out at a temperature of 480-520℃ and a holding time of 3-5h, thereby obtaining sintered NdFeB permanent magnets containing lanthanum and cerium.

[0020] Compared with existing technologies, this invention has the following advantages: Through synergistic optimization design of composition and microstructure, this invention achieves efficient utilization of high-abundance rare earth elements La and Ce, reducing the addition of major rare earth elements. Without increasing costs, it significantly improves the magnetic properties of permanent magnets, resulting in NdFeB permanent magnets with high Curie temperatures and high thermal stability. Specifically, this invention employs an innovative composition design that partially replaces Ce with La and introduces a specific proportion of M, resulting in a relatively uniform distribution of La throughout the magnet. A higher proportion of La is distributed in the (Pr, Nd, La, Ce)FeB main phase, while Ce is enriched at grain boundaries. This avoids the formation of harmful CeFe2 phases and improves the wettability and continuity of grain boundary phases, thereby improving the magnetic properties of the permanent magnet, such as magnetization, temperature stability, and remanence temperature coefficient. It enhances remanence and temperature stability while maintaining high coercivity. This invention improves the overall performance of permanent magnets and effectively reduces dependence on major rare earth elements by increasing the proportion of high-abundance rare earth elements, offering significant cost advantages and industrial application value. Attached Figure Description

[0021] Figure 1 SEM images of the sintered NdFeB permanent magnet samples from Example 3-2;

[0022] Figure 2 for Figure 1 A magnified view of the image within the red box;

[0023] Figure 3 for Figure 2 EDS energy dispersive spectral analysis results at midpoints 30, 31, 34, and 48;

[0024] Figure 4 SEM image of the sintered NdFeB permanent magnet sample from Example 1-1;

[0025] Figure 5 for Figure 4 A magnified view of the image within the green box;

[0026] Figure 6 for Figure 4 EDS energy dispersive spectroscopy results at midpoint 1 and point 2. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Raw materials, additives, equipment, etc., not limited in scope in this invention, are all produced using conventional techniques in the art. The raw materials and additives used in the following embodiments are commercially available products.

[0028] Eight examples and four comparative examples of NdFeB permanent magnets were selected and divided into four groups. Each group included one comparative example and two examples for horizontal comparison, totaling 12 grades. All samples were processed into sintered NdFeB permanent magnet samples using the preparation method of this invention. The test results of the magnetic properties of the sintered NdFeB permanent magnet samples of each example and comparative example are shown in Table 1, and the chemical composition is shown in Table 2.

[0029] The preparation methods of the sintered NdFeB permanent magnet samples in each embodiment and comparative example specifically include the following steps:

[0030] 1) Based on the chemical formula of NdFeB permanent magnets, calculate and weigh the raw materials according to the designed composition ratio, and place the raw materials sequentially into the crucible in the rapid solidification furnace. Under an argon protective atmosphere, at 1480±20℃ and a vacuum degree of (2~10)×10 -2 Induction melting under Pa conditions, followed by rapid quenching and spinning at 1425±20℃ to form a rapidly solidified sheet with a thickness of 0.28±0.05mm;

[0031] 2) The obtained rapid solidification casting sheet is placed in a hydrogen crushing furnace. First, hydrogen is absorbed under a pressure of 0-2 MPa for 2-4 hours. Then, hydrogen is removed at a temperature of 500-600℃ for 6-10 hours. Finally, it is cooled to obtain coarse powder.

[0032] 3) Add 0.05-0.1% of antioxidant by weight of the obtained coarse powder, stir evenly, and then pulverize by air jet milling under nitrogen protection atmosphere to obtain fine powder with a particle size of 3.8±0.1μm;

[0033] 4) Add 0.05-0.1% of lubricant by weight of the fine powder to the obtained fine powder, stir evenly, first shape it in a magnetic field strength of 1.5-2.2T and a nitrogen protective atmosphere, and then perform isostatic pressing under a pressure of 140-220MPa to obtain a green body.

[0034] 5) The obtained green body is vacuum sintered at a sintering temperature of 1045-1065℃ and a holding time of 6-10h. Then, it is subjected to two-stage aging treatment. The first stage of aging treatment is carried out at a temperature of 850-920℃ and a holding time of 3-5h, and the second stage of aging treatment is carried out at a temperature of 480-520℃ and a holding time of 3-5h, thereby obtaining sintered NdFeB permanent magnets.

[0035] The magnetic properties of sintered NdFeB permanent magnet samples of each embodiment and comparative example were tested at different temperatures using the methods of GB / T 29628-2013 and GB / T 3217-2013. The test results are shown in Table 1.

[0036] Figure 1 SEM images of the sintered NdFeB permanent magnet samples from Example 3-2; Figure 2 for Figure 1 A magnified view of the image within the red box; Figure 3 for Figure 2 EDS energy dispersive spectroscopy analysis results at midpoints 30, 31, 34, and 48, where La / RE, Ce / RE, and La / Ce represent the proportions of La, Ce, and La to Ce in the total rare earth element content, respectively. Figure 1 No harmful CeFe2 phase with typical black contrast was observed. Figures 1-3 It can be seen that Ce is significantly enriched in the grain boundary phase, while La is relatively uniformly distributed in the magnet and enters the main phase. The mass percentage content of Ce in the main phase is 20.93% to 22.58%, and the mass percentage content of Ce in the grain boundary phase is 49.90% to 72.96%.

[0037] Figure 4 SEM image of the sintered NdFeB permanent magnet sample from Example 1-1; Figure 5 for Figure 4 A magnified view of the image within the green box; Figure 6 for Figure 4 The EDS energy dispersive spectroscopy results at midpoints 1 and 2, where La / RE, Ce / RE, and La / Ce represent the proportions of La, Ce, and La to Ce in the total rare earth element content, respectively. Figure 4 No harmful CeFe2 phase with typical black contrast was observed. Figures 4-6 It can be seen that Ce is significantly enriched in the grain boundary phase, with a mass percentage content of 14.74% to 14.87% in the grain boundary phase.

[0038] Combining Tables 1 and 2, we can see that: 1) Since the raw material prices of La and Ce are basically the same, the overall cost of the formula remains basically unchanged after La partially replaces Ce; 2) Adding 0.1 to 0.15 Al on the basis of adding La can ensure the balance of Br and Hcj in the magnet without increasing the cost; 3) When Ce:La = (1 to 2):1, the remanence temperature coefficient of the magnet shows an upward trend in this range, indicating that the addition of La improves the temperature stability of the remanence of the magnet; 4) Among the 12 grades of sintered NdFeB permanent magnet samples in the four groups of tested formulas, only by comparing different Ce:La ratios, it can be found that Ce:La = 3:2 has the best effect and the corresponding magnet has the best comprehensive performance.

[0039] Table 1: Magnetic properties of sintered NdFeB permanent magnet samples from each embodiment and comparative example at different test temperatures.

[0040]

[0041]

Claims

1. A neodymium iron boron permanent magnet containing lanthanum and cerium, characterized in that, The chemical formula of this neodymium iron boron permanent magnet is: (Pr h Nd i ) a La b Ce c B d Cu e Co f M g Fe 100-a-b-c-d-e-f-g Where M is a combination of at least one element selected from Al, Cr, Nb, Zr, Ti, Mn, Zn, V, and Mo with Ga, and a, b, c, d, e, f, g, and 100-abcdefg are Pr h Nd i The mass percentages of La, Ce, B, Cu, Co, M, and Fe in this NdFeB permanent magnet, and h and i, respectively, represent the mass percentages of Pr and Nd in Pr. h Nd i The mass percentages of the NdFeB permanent magnet are 27.2≤a≤29.5, 0.5≤b≤3.0, 0.5≤c≤3.0, 0.9≤d≤1.0, 0.1≤e≤1.5, 0.1≤f≤1.5, 0.1≤g≤1.5, 23≤h≤28, and 72≤i≤77. The main phase in the microstructure of this NdFeB permanent magnet is (Pr,Nd,La,Ce)FeB, with Ce enriched in the grain boundary phase.

2. The neodymium iron boron permanent magnet containing lanthanum and cerium according to claim 1, characterized in that, In this neodymium iron boron permanent magnet, the mass percentage ratio of Cu to Ga is Cu:Ga = (1~9):(1~6), and the mass percentage ratio of Ce to La is Ce:La = (1~3):(1~3).

3. The neodymium iron boron permanent magnet containing lanthanum and cerium according to claim 2, characterized in that, In this neodymium iron boron permanent magnet, 27.5≤a≤28.1, 0.5≤b≤1.5, 0.5≤c≤1.5, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 0.1≤g≤0.5, the mass percentage ratio of Cu to Ga is Cu:Ga=3:2, and the mass percentage ratio of Ce to La is Ce:La=1:1 or 3:

2.

4. The neodymium iron boron permanent magnet containing lanthanum and cerium according to claim 2, characterized in that, In this neodymium iron boron permanent magnet, 28.5≤a≤29.5, 1.0≤b≤2.5, 0.5≤c≤1.5, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 0.25≤g≤0.8, the mass percentage ratio of Cu to Ga is Cu:Ga=9:5, and the mass percentage ratio of Ce to La is Ce:La=2:3 or 3:

2.

5. A neodymium iron boron permanent magnet containing lanthanum and cerium according to claim 2, characterized in that, In this neodymium iron boron permanent magnet, 28.8≤a≤29.5, 0.5≤b≤1.5, 0.5≤c≤1.5, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 0.1≤g≤0.5, the mass percentage ratio of Cu to Ga is Cu:Ga=3:2, and the mass percentage ratio of Ce to La is Ce:La=3:1 or 3:

2.

6. A neodymium-iron-boron permanent magnet containing lanthanum and cerium according to claim 2, characterized in that, In this neodymium iron boron permanent magnet, 27.2≤a≤28.0, 2.0≤b≤3.0, 2.0≤c≤3.0, 0.9≤d≤1.0, 0.1≤e≤0.4, 0.1≤f≤1.5, 1.0≤g≤1.5, the mass percentage ratio of Cu to Ga is Cu:Ga=1.12:1, and the mass percentage ratio of Ce to La is Ce:La=2:3 or 3:

2.

7. A method for preparing a neodymium iron boron permanent magnet containing lanthanum and cerium as described in any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Based on the chemical formula of neodymium iron boron permanent magnets (Pr h Nd i ) a La b Ce c B d Cu e Co f M g Fe 100-a-b-c-d-e-f-g Calculate and weigh the raw materials according to the designed composition ratio, and place the raw materials into the crucible in the rapid solidification furnace in sequence. Under the protection of argon atmosphere, at 1480±20℃ and a vacuum degree of (2~10)×10 -2 Induction melting under Pa conditions, followed by rapid quenching and spinning at 1425±20℃ to produce a rapidly solidified sheet with a thickness of 0.28±0.05mm; 2) The obtained rapid solidification casting sheet is placed in a hydrogen crushing furnace. First, hydrogen is absorbed under a pressure of 0-2 MPa for 2-4 hours. Then, hydrogen is removed at a temperature of 500-600℃ for 6-10 hours. Finally, it is cooled to obtain coarse powder. 3) Add 0.05-0.1% of antioxidant by weight of the obtained coarse powder, stir evenly, and then pulverize by air jet milling under nitrogen protection atmosphere to obtain fine powder with a particle size of 3.8±0.1μm; 4) Add 0.05-0.1% of lubricant by weight of the fine powder to the obtained fine powder, stir evenly, first shape it in a magnetic field strength of 1.5-2.2T and a nitrogen protective atmosphere, and then perform isostatic pressing under a pressure of 140-220MPa to obtain a green body. 5) The obtained green blank is vacuum sintered at a sintering temperature of 1045-1065℃ and a holding time of 6-10h, followed by two-stage aging treatment. The first stage of aging treatment is carried out at a temperature of 850-920℃ and a holding time of 3-5h, and the second stage of aging treatment is carried out at a temperature of 480-520℃ and a holding time of 3-5h, thereby obtaining sintered NdFeB permanent magnets containing lanthanum and cerium.

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