Sintered neodymium-iron-boron magnet for preparing lanthanum-cerium-yttrium and method thereof

Abstract

The invention relates to the technical field of neodymium-iron-boron magnet production, in particular to a sintered neodymium-iron-boron magnet for preparing lanthanum-cerium-yttrium and a method of the sintered neodymium-iron-boron magnet. In the invention, the cerium element is used for replacing a praseodymium-neodymium alloy, meanwhile, the lanthanum and yttrium elements are introduced according to the proportion to generate a synergistic effect to regulate and control the structure of the high-cerium-content sintered neodymium-iron-boron magnet, the yttrium element is used for inhibiting main phase grain coarsening and improving the coercive force, and the lanthanum and yttrium elements can promote the flow of a rare earth-rich liquid phase in the sintering process and improve the diffusivity, so that the high-cerium-content sintered neodymium-iron-boron magnet is obtained. The density is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of neodymium-iron-boron magnet production, and particularly relates to a sintered neodymium-iron-boron magnet prepared by using lanthanum, cerium and yttrium and a method thereof. BACKGROUND

[0002] The main component of the traditional sintered neodymium-iron-boron magnet is praseodymium-neodymium (PrNd) alloy, but with the rapid development of high-tech fields such as electronic information, new energy vehicles, household appliances and robots, the demand for praseodymium-neodymium is increasing, which leads to high price and limited global reserves, resulting in an imbalance in the use of rare earth resources. Therefore, it is desired to replace praseodymium-neodymium (PrNd) alloy with relatively cheap and abundant elements.

[0003] Cerium (Ce) rare earth element is considered as a key path to solve the resource contradiction because of its abundant reserves and low price. However, when the addition ratio of cerium (Ce) exceeds 5%, the magnet performance deteriorates significantly, and the magnet exhibits problems such as uneven distribution of grain boundary phase, coercivity decay, main phase structure stability and magnetic phase proportion reduction, sintering densification and liquid phase diffusion deficiency. SUMMARY

[0004] In order to overcome the above-mentioned deficiencies, the present application aims to provide a sintered neodymium-iron-boron magnet prepared by using lanthanum, cerium and yttrium, which replaces praseodymium-neodymium alloy with cerium element, and simultaneously introduces lanthanum and yttrium elements in a certain proportion to produce a synergistic effect, so as to regulate the structure of the sintered neodymium-iron-boron magnet containing high cerium, thereby solving the problem of significant deterioration of magnet performance when the addition ratio of cerium exceeds 5%.

[0005] The technical solution of the present application to solve the technical problem is: A sintered neodymium-iron-boron magnet prepared by using lanthanum, cerium and yttrium, wherein it comprises (R （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） structure, wherein R is one or more of Pr, Nd, Dy, Tb, Ho, Gd rare earth elements, M is one or more of Cu, Al, Nb, Zr, Ga, Ti, B is boron element, T is Fe and Co element, La is lanthanum element, Ce is cerium element, Y is yttrium element; 28wt%≤x≤34wt%, 0<y≤3wt%, 0.85wt%≤z≤1wt%, 0.15<a:b<0.4, c:(a+b)=0.05~0.3, and c≤2.5wt%, 5%≤a+b≤15%.

[0006] As an improvement of the present application, it comprises (R （x-a-b-c） La aCe b Y c ) x -M y -B z -T （1-x-y-z） Structural formula, wherein, R is Pr, Nd, Dy, Tb, Ho, Gd rare earth elements one or more, M is Cu, Al, Nb, Zr, Ga, Ti one or more, B is boron element, T is Fe and Co element, La is lanthanum element, Ce is cerium element, Y is yttrium element;30wt%≤x≤32wt%, 0<y≤1.5wt%, 0.9wt%≤z≤0.95wt%, 0.3<a:b<0.4, c:(a+b)=0.05~0.3.

[0007] As a further improvement of the application, comprising (R （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） Structural formula, wherein, R is Pr, Nd, Dy, Tb, Ho, Gd rare earth elements one or more, M is Cu, Al, Nb, Zr, Ga, Ti one or more, B is boron element, T is Fe and Co element, La is lanthanum element, Ce is cerium element, Y is yttrium element;30wt%≤x≤32wt%, 0<y≤1wt%, 0.9wt%≤z≤0.95wt%, 0.3<a:b<0.35, c:(a+b)=0.2~0.3.

[0008] As a further improvement of the application, comprising (R （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） Structural formula, wherein, R is Pr, Nd, M is Cu, Al, Nb, Ga, Ti, B is boron element, T is Fe and Co element, La is lanthanum element, Ce is cerium element, Y is yttrium element;X=32wt%, y=0.83wt%, z=0.92wt%, a:b=0.33, c:(a+b)=0.2, and c=2wt%, a+b=10%.

[0009] A method for preparing lanthanum cerium yttrium sintered neodymium iron boron magnet, wherein, comprising the following steps: Step S1, preparing diffusion matrix, mixing component raw materials containing PrNd, Ce, La, Y, B, Ti, Cu, Co, Al, Ga, Fe, then smelting into flaky alloy, and making into fine powder, pressing into green body, performing isostatic pressing treatment, and then sintering; Step S2, grain boundary diffusion treatment: obtaining diffusion neodymium-iron-boron magnet by coating Dy diffusion source and then performing heat treatment, wherein the coating Dy content is 0.4-1.0wt%, the grain boundary diffusion heat treatment temperature is 800-1000℃, the time is 4-16h, the tempering temperature is 450-600℃, and the time is 2-6h.

[0010] As an improvement of the present application, step S1 comprises: Step S11, mixing component raw materials according to the component formula; Step S12, smelting at a temperature of 1400℃-1500℃ by an induction furnace, and fast quenching and belt casting to form a flaky alloy with a thickness of 0.2mm-0.4mm; Step S13, crushing the alloy flake by hydrogen and air flow grinding to form a fine powder with a size of 3.2μm-4.5μm; Step S14, pressing the fine powder into a green body under a magnetic field with a magnetic field intensity of 1.6T or above; Step S15, placing the green body into a vacuum sintering furnace after isostatic pressing, sintering at a temperature of 1000℃-1100℃ for 5h-6h to obtain a sintered neodymium-iron-boron magnet, and cutting the sintered neodymium-iron-boron magnet into a flaky substrate with a thickness of 2mm-10mm for grain boundary diffusion.

[0011] As a further improvement of the present application, step S1 further comprises step S16; step S16, performing tempering treatment on part of the sintered neodymium-iron-boron magnet, the first tempering temperature is 800-980℃, and the time is 3h, and the second tempering temperature is 400-600℃, and the time is 5h.

[0012] As a further improvement of the present application, in step S12, smelting at a temperature of 1460℃ by an induction furnace, and fast quenching and belt casting to form a flaky alloy with a thickness of 0.3mm.

[0013] As a further improvement of the present application, in step S13, crushing the alloy flake by hydrogen and air flow grinding to form a fine powder with a size of 3.8μm.

[0014] As a further improvement of the present application, the component formula comprises 20% PrNd, 7.5% Ce, 2.5% La, 2% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, and 65.25% Fe in terms of mass percentage. In the present application, cerium element is used to replace praseodymium-neodymium alloy, lanthanum and yttrium elements are introduced in proportion to produce synergistic effect to control the structure of sintered neodymium-iron-boron magnet containing high cerium, the main phase grain coarsening is inhibited by yttrium element, and the coercivity is improved, and lanthanum and yttrium elements can promote the flow of rare earth-rich liquid phase in the sintering process, improve the diffusion property, and improve the density. BRIEF DESCRIPTION OF DRAWINGS

[0016] For ease of illustration, the present application is described in detail by the following preferred embodiments and drawings.

[0017] Fig. 1 SEM image in Example 4 in the present application; Fig. 2 SEM image in Comparative Example 5 in the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0019] Cerium (Ce) substitution technology is considered as a key path to solve the resource contradiction, but when the addition ratio exceeds 5%, the performance of the magnet is significantly deteriorated, which specifically shows the following core problems: 1. Inhomogeneous distribution of grain boundary phase and coercivity decay: The atomic radius of cerium is significantly different from that of neodymium, resulting in low solid solubility of cerium in the main phase (Nd2Fe 14 B), which is easy to enrich and form coarse and discrete grain boundary phase at the grain boundary. In the traditional process, the segregation of cerium destroys the interface coupling of the main phase and the rare earth-rich phase, weakens the pinning effect of the grain boundary on the magnetic domain wall, and reduces the coercivity; 2. Main phase structure stability and magnetic phase proportion reduction: The introduction of cerium will reduce the magnetocrystalline anisotropy field of the main phase Nd2Fe 14 B, and induce local enrichment of Fe element to form non-magnetic phase (such as CeFe2), resulting in reduction of main phase volume fraction and magnetic energy product, and lattice mismatch between main phases is intensified under high cerium system, resulting in grain coarsening, which further deteriorates the magnetic performance; 3. Sintering densification and insufficient liquid phase diffusion: Cerium has strong oxidation tendency, which is easy to form oxide impurities such as CeO2 during sintering, hindering the flow of grain boundary liquid phase. At the same time, high cerium content will reduce the melting point of rare earth-rich phase, resulting in early formation of liquid phase but insufficient penetration depth, and the density of the magnet is reduced to below 95%, the porosity is increased to 3%~5%, which significantly reduces the remanence and bending strength.

[0020] The prior art can partially improve the magnetic properties by adding Al, Cu, Ga and other elements to optimize the grain boundary phase, but the effect of improving the coercivity of the high Ce system is limited, and the cost and performance requirements cannot be balanced, and some technologies improve the magnetic properties of the high Ce system by improving the diffusion source and diffusion process, but the diffusion of the high Ce neodymium iron boron magnet itself and the diffusion thickness are limited, and the magnetic property improvement range is limited.

[0021] The present application solves the problem that the performance of the magnet is significantly deteriorated when the proportion of cerium-rich addition exceeds 5%, and the present application optimizes the component ratio to produce a synergistic effect by introducing La and Y elements to regulate the structure and composition of high-cerium neodymium iron boron; the present application improves the coercivity of the magnet and improves the diffusion and thermal stability of the magnet by optimizing the element ratio through the synergistic effect between La, Ce and Y, thereby reducing the production cost and improving the product performance.

[0022] As shown in Figs. 1-2 A method for preparing a sintered neodymium iron boron magnet of lanthanum cerium yttrium, comprising the following steps: I. Preparation of diffusion matrix, mixing component raw materials containing PrNd, Ce, La, Y, B, Ti, Cu, Co, Al, Ga, Fe, then smelting into sheet alloy, and then into fine powder, pressing into green body, and then performing isostatic pressing treatment and sintering; wherein, specifically comprising: Step S11, mixing each component raw material according to the component formula; Step S12, smelting at a temperature of 1460±20℃ by an induction furnace, and fast quenching and belt casting to form a sheet alloy with a thickness of 0.3±0.05mm; Step S13, crushing the alloy sheet by hydrogen and air flow grinding into fine powder with a particle size of 3.8±0.2μm; Step S14, pressing the fine powder into a green body under the condition of a magnetic field with a magnetic field strength of 1.6T or above; Step S15, placing the green body into a vacuum sintering furnace after isostatic pressing, and sintering at a temperature of 1060±10℃ for 5h~6h to obtain a sintered neodymium iron boron magnet, and cutting the sintered neodymium iron boron magnet into sheet substrates with a thickness of 4mm and 8mm for grain boundary diffusion; Step S16, taking part of the sintered neodymium iron boron magnet for tempering treatment, the first tempering temperature is 900℃, and the time is 3h, the second tempering temperature is 500℃, and the time is 5h.

[0023] II. Grain boundary diffusion treatment: a diffusion neodymium iron boron magnet is obtained by coating a Dy diffusion source and then performing heat treatment, wherein the coating Dy content is 0.8wt%, the grain boundary diffusion heat treatment temperature is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h.

[0024] Specifically, the steps are as follows: I. Preparation of diffusion matrix According to the component formula, the raw materials of each component are mixed, melted in an induction furnace at a temperature of 1460±20℃, and quickly quenched to prepare a 0.3±0.05mm thick sheet-shaped alloy; the alloy sheet is crushed by hydrogen and pulverized by air flow mill to 3.8±0.2μm fine powder; the fine powder is pressed into a green body under the condition of a magnetic field with a magnetic field intensity of 1.6T or above; the green body is placed into a high vacuum sintering furnace after isostatic pressing, sintered at a temperature of 1060±10℃ for 6h to obtain a sintered neodymium-iron-boron magnet, and the sintered neodymium-iron-boron magnet is cut into 4mm and 8mm sheet-shaped substrates for grain boundary diffusion; part of the sintered neodymium-iron-boron magnet is tempered, the first-stage tempering temperature is 900℃, and the time is 3h, and the second-stage tempering temperature is 500℃, and the time is 5h.

[0025] II. Grain boundary diffusion treatment The grain boundary diffusion treatment adopts the method of coating Dy diffusion source and then heat treatment to obtain the diffusion neodymium-iron-boron magnet; wherein, the coating Dy content is 0.8wt%, the grain boundary diffusion heat treatment temperature is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h.

[0026] The present application provides Example 1 and Comparative Example 1 (component ratio see Table 1) as follows: Example 1

[0027] 1. Preparation of diffusion matrix According to the component formula, the raw materials of each component are mixed, melted in an induction furnace at a temperature of 1460±20℃, and quickly quenched to prepare a 0.3±0.05mm thick sheet-shaped alloy; the alloy sheet is crushed by hydrogen and pulverized by air flow mill to 3.8±0.2μm fine powder; the fine powder is pressed into a green body under the condition of a magnetic field with a magnetic field intensity of 1.6T or above; the green body is placed into a high vacuum sintering furnace after isostatic pressing, sintered at a temperature of 1060±10℃ for 6h to obtain a sintered neodymium-iron-boron magnet, and the sintered neodymium-iron-boron magnet is cut into 4mm and 8mm sheet-shaped substrates for grain boundary diffusion; part of the sintered neodymium-iron-boron magnet is tempered, the first-stage tempering temperature is 900℃, and the time is 3h, and the second-stage tempering temperature is 500℃, and the time is 5h.

[0028] 2. Grain boundary diffusion treatment The grain boundary diffusion treatment obtains the diffusion neodymium-iron-boron magnet by coating Dy diffusion source and then performing heat treatment; wherein, the coating Dy content is 0.8wt%, the temperature of the grain boundary diffusion heat treatment is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h, and the measured diffusion magnetic properties are shown in Table 2.

[0029] Comparative Example 1 1. Preparation of diffusion substrate The component raw materials are mixed according to the component formula with mass percentage of 24%PrNd, 8%Ce, 0.92%B, 0.3%Cu, 0.25%Ga, 1%Co, 0.1%Al, 0.18%Ti, 65.25%Fe, La:Ce=0, Y:(La+Ce)=0, melted by an induction furnace at a temperature of 1460℃, and prepared into a 0.3mm-thick flaky alloy by belt casting. The alloy flake is crushed by hydrogen and pulverized into a fine powder of 3.8μm by airflow milling. The fine powder is pressed into a green body under a magnetic field with a magnetic field intensity of 1.6T or above. The green body is placed into a high vacuum sintering furnace after isostatic pressing, sintered at a temperature of 1060℃ for 6h to obtain a sintered neodymium-iron-boron magnet. The sintered neodymium-iron-boron magnet is cut into 4mm and 8mm flaky substrates for grain boundary diffusion. Part of the sintered neodymium-iron-boron magnet is subjected to tempering treatment, the first-stage tempering temperature is 900℃, and the time is 3h, the second-stage tempering temperature is 500℃, and the time is 5h. The measured magnetic properties of the neodymium-iron-boron substrate are shown in Table 2.

[0030] 2. Grain boundary diffusion treatment The grain boundary diffusion treatment obtains the diffusion neodymium-iron-boron magnet by coating Dy diffusion source and then performing heat treatment; wherein, the coating Dy content is 0.8wt%, the temperature of the grain boundary diffusion heat treatment is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h, and the measured diffusion magnetic properties are shown in Table 2.

[0031] Table 1 Component proportion table

[0032] Table 2 Magnetic property comparison table

[0033] From the experimental data in Table 2, it can be seen that: 1. Comparative Example 1 is a high-purity Ce formula, and Example 1 is a La, Ce, Y composite formula of the present application. The Hcj of the high-Ce neodymium-iron-boron substrate of the present application is 0.58kOe higher than that of the comparative example, indicating that the high-Ce neodymium-iron-boron substrate of the present application plays a good effect in strengthening the grain boundary pinning effect and inhibiting the microstructure strengthening of reverse magnetic domain nucleation; 2、The Hcj of the high cerium neodymium iron boron 4mm and 8mm sheet-shaped base material of the application after grain boundary diffusion is 1.82kOe and 2.74kOe higher than that of the comparative example respectively, and the difference between the Hcj of the two is greater as the thickness increases, indicating that the high cerium neodymium iron boron base material of the application has better diffusion property and deeper diffusion depth; 3、The Br temperature coefficient at 120℃ of the high cerium neodymium iron boron base material of the application after diffusion is 0.06% better than that of the comparative example, indicating that the high cerium neodymium iron boron base material of the application has a good stabilizing effect on the main phase and can reduce high-temperature demagnetization.

[0034] The application provides examples 2 and 3 and comparative examples 2, 3 and 4 (the component ratio is shown in Table 3), as follows: Example 2

[0035] 1、Preparation of diffusion base The component formula of 20% PrNd, 9% Ce, 2% La, 1% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe, La:Ce=0.22, Y: (La+Ce)=0.09 is mixed according to the mass percentage content, and each component raw material is melted at a temperature of 1460℃ by an induction furnace, and is quickly quenched to prepare a sheet-shaped alloy with a thickness of 0.3mm; the alloy sheet is crushed by hydrogen and pulverized by airflow to form a fine powder with a particle size of 3.8μm; the fine powder is pressed into a green body under the condition of a magnetic field with a magnetic field intensity of 1.6T or more; the green body is placed into a high vacuum sintering furnace after isostatic pressing, and is sintered at a temperature of 1060℃ for 6h to obtain a sintered neodymium iron boron magnet; the sintered neodymium iron boron magnet is cut into a 3mm sheet-shaped base material for grain boundary diffusion; part of the sintered neodymium iron boron magnet is tempered, the first-stage tempering temperature is 900℃, and the time is 3h, the second-stage tempering temperature is 500℃, and the time is 5h; the magnetic properties of the neodymium iron boron base material are measured and shown in Table 4.

[0036] 2、Grain boundary diffusion treatment The grain boundary diffusion treatment adopts the mode of coating a Dy diffusion source and then performing heat treatment to obtain a diffusion neodymium iron boron magnet; wherein the coating Dy content is 0.6wt%, the grain boundary diffusion heat treatment temperature is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h; the diffusion magnetic properties are measured and shown in Table 4. Example 3

[0037] 1、Preparation of diffusion base The component formula of 20% PrNd, 7.5% Ce, 2.5% La, 2% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe, La:Ce=0.33, Y:(La+Ce)=0.2 by mass percentage is used to mix raw materials of each component, and the alloy is prepared into a 0.3mm-thick sheet by induction furnace smelting at a temperature of 1460℃ and quick quenching and belt casting; the alloy sheet is crushed by hydrogen and pulverized into a 3.8μm fine powder by airflow milling; the fine powder is pressed into a green body under a magnetic field with a magnetic field intensity of 1.6T or above; the green body is placed into a high vacuum sintering furnace after isostatic pressing and sintered at a temperature of 1060℃ for 6h to obtain a sintered neodymium-iron-boron magnet; the sintered neodymium-iron-boron magnet is cut into a 3mm sheet-shaped substrate for grain boundary diffusion; a part of the sintered neodymium-iron-boron magnet is tempered, the first-stage tempering temperature is 900℃, the time is 3h, the second-stage tempering temperature is 500℃, and the time is 5h, and the magnetic properties of the neodymium-iron-boron substrate are measured and shown in Table 4.

[0038] 2. Grain boundary diffusion treatment The grain boundary diffusion treatment adopts a method of coating a Dy diffusion source and then performing heat treatment to obtain a diffusion neodymium-iron-boron magnet; wherein the Dy coating content is 0.6wt%, the grain boundary diffusion heat treatment temperature is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h, and the diffusion magnetic properties are measured and shown in Table 4.

[0039] Comparative Example 2: 1. Preparation of diffusion substrate The component formula of 20% PrNd, 12% Ce, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe, La:Ce=0, Y:(La+Ce)=0 by mass percentage is used to mix raw materials of each component, and the alloy is prepared into a 0.3mm-thick sheet by induction furnace smelting at a temperature of 1460℃ and quick quenching and belt casting; the alloy sheet is crushed by hydrogen and pulverized into a 3.8μm fine powder by airflow milling; the fine powder is pressed into a green body under a magnetic field with a magnetic field intensity of 1.6T or above; the green body is placed into a high vacuum sintering furnace after isostatic pressing and sintered at a temperature of 1060℃ for 6h to obtain a sintered neodymium-iron-boron magnet; the sintered neodymium-iron-boron magnet is cut into a 3mm sheet-shaped substrate for grain boundary diffusion; a part of the sintered neodymium-iron-boron magnet is tempered, the first-stage tempering temperature is 900℃, the time is 3h, the second-stage tempering temperature is 500℃, and the time is 5h, and the magnetic properties of the neodymium-iron-boron substrate are measured and shown in Table 4.

[0040] 2. Grain boundary diffusion treatment The grain boundary diffusion treatment adopts the method of coating Dy diffusion source and then heat treatment to obtain the diffusion Nd-Fe-B magnet; wherein, the coating Dy content is 0.6wt%, the temperature of grain boundary diffusion heat treatment is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h, and the measured diffusion magnetic properties are shown in Table 4.

[0041] Comparative Example 3: 1. Preparation of diffusion substrate The component formula of 20%PrNd, 10.5%Ce, 1%La, 0.5%Y, 0.92%B, 0.3%Cu, 0.25%Ga, 1%Co, 0.1%Al, 0.18%Ti, 65.25%Fe, La:Ce=0.1, Y:(La+Ce)=0.04 is mixed with each component raw material, melted at 1460℃ by induction furnace, and quickly quenched to prepare 0.3mm thick sheet alloy; the alloy sheet is crushed by hydrogen and air mill to 3.8μm fine powder; the fine powder is pressed into green body under the condition of magnetic field intensity above 1.6T; the green body is put into high vacuum sintering furnace after isostatic pressing, sintered at 1060℃ for 6h to obtain sintered Nd-Fe-B magnet, and the sintered Nd-Fe-B magnet is cut into 3mm sheet substrate for grain boundary diffusion; part of the sintered Nd-Fe-B magnet is tempered, the first stage tempering temperature is 900℃, and the time is 3h, the second stage tempering temperature is 500℃, and the time is 5h, and the measured magnetic properties of Nd-Fe-B substrate are shown in Table 4.

[0042] 2. Grain boundary diffusion treatment The grain boundary diffusion treatment adopts the method of coating Dy diffusion source and then heat treatment to obtain the diffusion Nd-Fe-B magnet; wherein, the coating Dy content is 0.6wt%, the temperature of grain boundary diffusion heat treatment is 900℃, the time is 8h, the tempering temperature is 500℃, and the time is 4h, and the measured diffusion magnetic properties are shown in Table 4.

[0043] Comparative Example 4: 1. Preparation of diffusion substrate The component formula of 20% PrNd, 5.5% Ce, 3% La, 3.5% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe, La:Ce=0.55, Y:(La+Ce)=0.41 is mixed with each component raw material, melted at a temperature of 1460 DEG C by an induction furnace, and quickly quenched to prepare an alloy sheet with a thickness of 0.3 mm; the alloy sheet is crushed by hydrogen and pulverized into a fine powder with a particle size of 3.8 microns by airflow milling; the fine powder is pressed into a green body under a magnetic field with a magnetic field intensity of 1.6T or above; the green body is placed into a high vacuum sintering furnace after isostatic pressing, sintered at a temperature of 1060 DEG C for 6 hours to obtain a sintered Nd-Fe-B magnet, and the sintered Nd-Fe-B magnet is cut into a 3 mm sheet-shaped substrate for grain boundary diffusion; a part of the sintered Nd-Fe-B magnet is tempered, the first-stage tempering temperature is 900 DEG C, and the time is 3 hours, the second-stage tempering temperature is 500 DEG C, and the time is 5 hours, and the magnetic properties of the Nd-Fe-B substrate are measured, as shown in Table 4.

[0044] 2. Grain boundary diffusion treatment The grain boundary diffusion treatment adopts a mode of coating a Dy diffusion source and then performing heat treatment to obtain a diffusion Nd-Fe-B magnet; wherein the coating Dy content is 0.6wt%, the grain boundary diffusion heat treatment temperature is 900 DEG C, the time is 8 hours, the tempering temperature is 500 DEG C, and the time is 4 hours, and the diffusion magnetic properties are measured, as shown in Table 4.

[0045] Table 3 Component ratio table

[0046] Table 4 Magnetic property comparison table

[0047] From the experimental data in Table 4, it can be seen that: 1. The magnetic properties of the high-cerium Nd-Fe-B substrate of the present application are better than those of the high-purity Ce cerium formula and the complex formula exceeding the ratio relationship among La, Ce and Y; 2. The magnetic properties and Br temperature coefficient of the high-cerium Nd-Fe-B magnet of the present application after grain boundary diffusion are also obviously better than those of the comparative examples, indicating that when the ratio relationship of La, Ce and Y is exceeded, the synergistic effect of the combined addition of La and Y does not work well; 3. The high-cerium Nd-Fe-B magnet of the present application exhibits excellent effects in improving the coercivity of the substrate, diffusion and improving the thermal stability of the magnet.

[0048] The present application provides Example 4 and Comparative Example 5 (component ratio see Table 5), as follows: Example 4

[0049] The component formula of 22% PrNd, 7% Ce, 2% La, 1% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe, La:Ce=0.29, Y:(La+Ce)=0.1 in mass percentage content is mixed, and then the component materials are smelted at a temperature of 1460 DEG C by an induction furnace, and then the alloy is prepared into a sheet alloy with a thickness of 0.3mm by fast quenching and belt casting; the alloy sheet is crushed by hydrogen and pulverized into a fine powder with a particle size of 3.8um by air flow milling; the fine powder is pressed into a green body under a magnetic field with a magnetic field intensity of 1.6T; the green body is put into a high vacuum sintering furnace after isostatic pressing, and then the sintered Nd-Fe-B magnet is obtained by sintering at a temperature of 1060 DEG C for 6h; the sintered Nd-Fe-B magnet is tempered, the first tempering temperature is 900 DEG C, and the time is 3h, the second tempering temperature is 500 DEG C, and the time is 5h; and the magnetic properties of the Nd-Fe-B substrate are measured (see Table 6).

[0050] Comparative Example 5 The component formula of 22% PrNd, 7% Ce, 2% La, 1% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe, La:Ce=0.29, Y:(La+Ce)=0.1 in mass percentage content is mixed, and then the component materials are smelted at a temperature of 1460 DEG C by an induction furnace, and then the alloy is prepared into a sheet alloy with a thickness of 0.3mm by fast quenching and belt casting; the alloy sheet is crushed by hydrogen and pulverized into a fine powder with a particle size of 3.8um by air flow milling; the fine powder is pressed into a green body under a magnetic field with a magnetic field intensity of 1.6T; the green body is put into a high vacuum sintering furnace after isostatic pressing, and then the sintered Nd-Fe-B magnet is obtained by sintering at a temperature of 1060 DEG C for 6h; the sintered Nd-Fe-B magnet is tempered, the first tempering temperature is 900 DEG C, and the time is 3h, the second tempering temperature is 500 DEG C, and the time is 5h; and the magnetic properties of the Nd-Fe-B substrate are measured (see Table 6).

[0051] Table 5 Component ratio table

[0052] Table 6 Magnetic property comparison table

[0053] As shown in the experimental data in Table 6, the high-cerium Nd-Fe-B substrate of the application introduces Y element, which plays a role in inhibiting the grain coarsening of the main phase and refining the grains; and the Y element forms a Y-O-Ce hard shell layer at the grain boundary, enhances the pinning of the anti-magnetization domain, and thus improves the coercivity.

[0054] The neodymium-iron-boron magnet of the present application produces synergistic effect by introducing La and Y elements, optimizes the component proportion (preferably the specific proportion is 20% PrNd, 7.5% Ce, 2.5% La, 2% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, 65.25% Fe in terms of mass percentage, La:Ce is about 0.33, and Y:(La+Ce)=0.2), regulates the structure and composition of the neodymium-iron-boron magnet, and specifically as follows: 1. Coercivity strengthening: Y element inhibits the main phase grain coarsening, refines the grain, Y forms Y-O-Ce hard shell layer at the grain boundary, enhances the anti-magnetization domain pinning, and improves the coercivity; 2. Thermal stability improvement: La-Ce-Y synergistic effect stabilizes the main phase structure, and reduces the temperature sensitivity; 3. Diffusion optimization: Y promotes the flow of rare earth-rich liquid phase during the sintering process, improves the diffusion, and improves the density.

[0055] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sintered NdFeB magnet for preparing lanthanum-cerium-yttrium, characterized in that, Including (R) （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） The structural formula is as follows: R is one or more rare earth elements selected from Pr, Nd, Dy, Tb, Ho, and Gd; M is one or more rare earth elements selected from Cu, Al, Nb, Zr, Ga, and Ti; B is boron; T is Fe and Co; La is lanthanum; Ce is cerium; and Y is yttrium. The formula is: 28wt%≤x≤34wt%, 0<y≤3wt%, 0.85wt%≤z≤1wt%, 0.15<a:b<0.4, c:(a+b)=0.05~0.3, and c≤2.5wt%, 5%≤a+b≤15%.

2. The sintered NdFeB magnet for preparing lanthanum-cerium-yttrium according to claim 1, characterized in that, Including (R) （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） The structural formula is as follows: R is one or more rare earth elements Pr, Nd, Dy, Tb, Ho, and Gd; M is one or more rare earth elements Cu, Al, Nb, Zr, Ga, and Ti; B is boron; T is Fe and Co; La is lanthanum; Ce is cerium; and Y is yttrium. The formula is: 30wt%≤x≤32wt%, 0<y≤1.5wt%, 0.9wt%≤z≤0.95wt%, 0.3<a:b<0.4, and c:(a+b)=0.05~0.

3.

3. The sintered NdFeB magnet for preparing lanthanum-cerium-yttrium according to claim 2, characterized in that, Including (R) （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） The structural formula is as follows: R is one or more rare earth elements Pr, Nd, Dy, Tb, Ho, and Gd; M is one or more rare earth elements Cu, Al, Nb, Zr, Ga, and Ti; B is boron; T is Fe and Co; La is lanthanum; Ce is cerium; and Y is yttrium. The formula is: 30wt%≤x≤32wt%, 0<y≤1wt%, 0.9wt%≤z≤0.95wt%, 0.3<a:b<0.35, and c:(a+b)=0.2~0.

3.

4. The sintered NdFeB magnet for preparing lanthanum-cerium-yttrium according to claim 3, characterized in that, Including (R) （x-a-b-c） La a Ce b Y c ) x -M y -B z -T （1-x-y-z） The structural formula is as follows: R represents Pr or Nd, M represents Cu, Al, Nb, Ga, or Ti, B represents boron, T represents Fe or Co, La represents lanthanum, Ce represents cerium, and Y represents yttrium; x = 32 wt%, y = 0.83 wt%, z = 0.92 wt%, a:b = 0.33, c:(a+b) = 0.2, and c = 2 wt%, a+b = 10%.

5. A method for preparing sintered NdFeB magnets of lanthanum, cerium, and yttrium, characterized in that, Includes the following steps: Step S1: Prepare a diffusion matrix by mixing raw materials containing PrNd, Ce, La, Y, B, Ti, Cu, Co, Al, Ga, and Fe, then melting them to form a sheet alloy, which is then made into fine powder, pressed into a green blank, and sintered after isostatic pressing. Step S2, Grain boundary diffusion treatment: Diffused NdFeB magnets are obtained by coating with a Dy diffusion source followed by heat treatment. The Dy content is 0.4~1.0wt%, the grain boundary diffusion heat treatment temperature is 800~1000℃ and the time is 4~16h, and the tempering temperature is 450~600℃ and the time is 2~6h.

6. The method for preparing sintered NdFeB magnets of lanthanum, cerium, and yttrium according to claim 5, characterized in that, Step S1 includes: Step S11: Mix the raw materials of each component according to the ingredient formula; Step S12: The alloy is smelted in an induction furnace at a temperature of 1400℃~1500℃ and then rapidly quenched and spun into sheet alloys with a thickness of 0.2mm~0.4mm. Step S13: The alloy sheet is pulverized into fine powder of 3.2μm~4.5μm by hydrogen crushing and air jet milling; Step S14: Press the fine powder into a green body under a magnetic field strength of 1.6T or higher; Step S15: After isostatic pressing, the green blank is placed in a vacuum sintering furnace and sintered at 1000℃~1100℃ for 5h~6h to obtain sintered NdFeB magnets. The sintered NdFeB magnets are cut into 2mm~10mm sheet substrates for grain boundary diffusion.

7. The method for preparing sintered NdFeB magnets of lanthanum, cerium, and yttrium according to claim 6, characterized in that, Step S1 also includes step S16; Step S16: Take a portion of the sintered NdFeB magnets and temper them. The first tempering temperature is 800~980℃ and the time is 3h. The second tempering temperature is 400~600℃ and the time is 5h.

8. The method for preparing sintered NdFeB magnets of lanthanum, cerium, and yttrium according to claim 6, characterized in that, In step S12, the alloy is melted in an induction furnace at a temperature of 1460°C and then rapidly quenched and spun into sheet alloys with a thickness of 0.3 mm.

9. The method for preparing sintered NdFeB magnets of lanthanum, cerium, and yttrium according to claim 6, characterized in that, In step S13, the alloy sheet is pulverized into a fine powder of 3.8 μm by hydrogen crushing and air jet milling.

10. A method for preparing sintered NdFeB magnets of lanthanum, cerium, and yttrium according to claim 6, characterized in that, In step S11, the composition formula includes 20% PrNd, 7.5% Ce, 2.5% La, 2% Y, 0.92% B, 0.3% Cu, 0.25% Ga, 1% Co, 0.1% Al, 0.18% Ti, and 65.25% Fe by mass percentage.

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