Sintered cerium-iron-boron and preparation method therefor

Abstract

The present application relates to sintered cerium-iron-boron and a preparation method therefor. The preparation method comprises the following steps: subjecting all the raw materials to melt blending, cooling, crushing, powdering, forming under a magnetic field, isostatic pressing, sintering, a solution treatment, first-stage aging and second-stage aging, so as to obtain a product; and melt blending a first phase alloy and a second phase alloy to prepare a diffusion source, and then subjecting the product to a secondary diffusion treatment by using the diffusion source, so as to obtain cerium-iron-boron.

Description

Sintered cerium iron boron and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic materials, and particularly relates to a sintered cerium iron boron and a preparation method thereof. BACKGROUND

[0002] Since the invention of rare earth permanent magnet materials, they have been favored by many industries due to their excellent performance. Among many rare earth permanent magnet materials, samarium cobalt magnet and neodymium iron boron are the two most widely used ones. The samarium cobalt magnet has very high magnetic performance and good high-temperature resistance, but the samarium and cobalt in the raw material are relatively scarce and the cost is high, which limits its further popularization and use. The neodymium iron boron has the same excellent magnetic performance and is the highest magnetic permanent magnet material at present, and has a lower cost than the samarium cobalt magnet, so it has higher use value.

[0003] However, in actual use, it is found that the neodymium iron boron will have a large decrease in magnetic performance when used in a high-temperature environment. Therefore, some technicians propose to replace part of the neodymium (Nd) with other rare earth elements to improve the high-temperature resistance of the neodymium iron boron. With the increasing demand for neodymium iron boron, there is a problem of insufficient supply of neodymium elements. Therefore, people turn their attention to another rare earth element, cerium (Ce). By adding Ce in a certain proportion into the neodymium iron boron, a new type of permanent magnet material, cerium iron boron, can be obtained. According to the chemical properties of Ce and Nd, the cerium iron boron not only has good magnetic performance, but also has more excellent mechanical properties, high-temperature resistance and more stable and low cost than the neodymium iron boron.

[0004] However, in the preparation process of the cerium iron boron, coarse grains will be formed during the diffusion of Ce on the surface of the magnet, which will reduce the intrinsic coercivity of the cerium iron boron and hinder the application of the cerium iron boron in fields with high requirements for magnetic performance (such as wireless charging, relays and sensors, etc.). SUMMARY

[0005] In order to solve the above technical problems, the present application provides a sintered cerium iron boron and a preparation method thereof.

[0006] In a first aspect, the present application provides a preparation method of a sintered cerium iron boron, which comprises the following steps: melting and blending all raw materials, cooling, to obtain a sintered cerium iron boron with a formula of (Nd, M) a Ce 2-a Fe 14The alloy ingot of B is crushed, powdered, formed by a magnetic field, isostatic pressed, sintered, solid-solved, first aged and second aged to obtain a product, wherein a = 1.06-1.38, M is one or more of Gd, Ti and Zr; a first phase alloy and a second phase alloy with a weight ratio of 1:(0.8-1.0) are melt-blended at a vacuum degree of-0.1 MPa to 0.02 MPa and a temperature of 1300-1350 DEG C, cooled and post-processed to obtain a diffusion source, wherein the first phase alloy is expressed as Pr x Cu 100-x , x = 68-72, and the second phase alloy is expressed as Pr y Tb 10 Cu 90-y , y = 58-62, the diffusion source is then coated on the surface of the product, diffused at a vacuum degree of 4.8x10 -3 -5.2x10 - 3 Pa, a diffusion temperature of 850-900 DEG C for 1.5-2h, then diffused at a temperature of 980-1080 DEG C for 3-6h, then the system is cooled to 480-500 DEG C, annealed for 1.5-2.5h, and finally cooled to room temperature to obtain cerium-iron-boron.

[0007] By using the above technical scheme, the diffusion source obtained by melting the first phase alloy and the second phase alloy is prepared, and the diffusion source is uniformly coated on the outer surface of the cerium-iron-boron green body. Under a certain diffusion temperature and diffusion time, the diffusion source can play a grain boundary diffusion effect. Pr and Tb can be enriched on the surface of the cerium-iron-boron green body and form a Pr-rich shell and a Tb-rich shell to produce a continuous grain boundary phase, improve the magnetic crystal anisotropy field strength of the surface of the cerium-iron-boron, inhibit the magnetization reversal of the main phase grains in the cerium-iron-boron, thereby greatly improving the intrinsic coercive force and remanence of the cerium-iron-boron. Pr and Tb can fully play a synergistic effect to further enhance the magnetic crystal anisotropy field strength of the surface of the cerium-iron-boron. The enrichment of Tb on the surface of the magnet can also compensate for the negative impact of coarse grains on the magnetic properties and further compensate for the lack of magnetic properties. Cu can compensate for the loss of mechanical strength of the cerium-iron-boron after adding Pr and Tb. Therefore, the diffusion heat treatment of the cerium-iron-boron green body in the present application can effectively improve the magnetic properties of the cerium-iron-boron without affecting the mechanical strength of the cerium-iron-boron.

[0008] And, the application adopts secondary diffusion in the diffusion heat treatment, at a temperature of 850-900 DEG C, the internal of cerium iron boron mainly occurs rapid grain boundary diffusion phenomenon, greatly optimize the magnetic properties of cerium iron boron, subsequently the application is raised to 980-1080 DEG C and then carries out secondary diffusion, makes the internal of cerium iron boron more significant body diffusion phenomenon, the movement of atoms or ions in the grain interior gradually tends to homogenization, the atom or ion of uniform distribution can further enhance the magnetic properties of cerium iron boron.

[0009] Preferably, the post-processing specifically is that the cooled mixture is cut to obtain a sheet-shaped diffusion source.

[0010] By adopting the above technical scheme, the application cuts the diffusion source into a sheet shape, and uses the sheet-shaped diffusion source for treatment. Compared with powder diffusion source treatment or coating diffusion treatment, the grain boundary diffusion of the sheet-shaped diffusion source is more significant in two-dimensional direction, the surface area to volume ratio of diffusion is larger, and the interaction between the surface and grain boundary interface of cerium iron boron is more significant, which can further enhance the magnetic crystal anisotropy field strength of the surface of cerium iron boron. Moreover, although the powder material has more diffusion paths, and the coating diffusion has a faster diffusion speed, there is Ce in cerium iron boron itself which can promote diffusion. If the coating diffusion or powder diffusion source is used, excessive diffusion will occur, which will reduce the chemical uniformity between alloy particles, and further reduce the mechanical strength of cerium iron boron. Therefore, the application uses a sheet-shaped diffusion source in the grain boundary diffusion of cerium iron boron, which can take into account the improvement of mechanical properties and the effect of ensuring good diffusion.

[0011] Preferably, the time of the first diffusion is 1.8 h, and the time of the second diffusion is 4 h.

[0012] By adopting the above technical scheme, the application further controls the time of the first diffusion and the second diffusion, thereby further improving the magnetic properties of cerium iron boron.

[0013] Preferably, in the expression of the alloy ingot, a=1.25-1.35.

[0014] By adopting the above technical scheme, the application further controls the amount of Ce added, and further optimizes the overall performance of cerium iron boron. Since Ce can promote the enrichment of Pr and Tb on the surface of cerium iron boron to a certain extent, it plays an auxiliary role in the magnetic performance strengthening effect of diffusion heat treatment. Experimental data proves that when a=1.25-1.35, the high-temperature resistance of cerium iron boron is good, the cost is low, and it can effectively assist the magnetic performance strengthening effect of diffusion heat treatment. At the same time, the number of coarse grains is small, which can effectively optimize the magnetic properties, and the remanence and intrinsic coercive force are high.

[0015] Preferably, after the raw materials are melt-blended, the alloy ingot is obtained by cooling at a rate of 40-80℃ / s.

[0016] Compared with Nd, the chemical property of Ce is more active and is easy to be oxidized. By adopting the technical scheme, the cooling rate is limited, which is much greater than the natural cooling rate (2℃ / min on average). The fast cooling can greatly shorten the contact time of Ce in the alloy ingot with oxygen during the cooling process, thereby reducing the possibility of oxidation of Ce, reducing the number of magnetic phases of cerium-iron-boron that are oxidized and decomposed, and ensuring that the intrinsic coercive force of cerium-iron-boron is almost not affected.

[0017] Preferably, the sintering is performed twice, specifically, the material obtained after isostatic pressing is kept at a temperature of 800-850℃ for 1-1.5h, then heated to 1050-1100℃ and kept for 2-2.5h again, and then solid solution is performed.

[0018] By adopting the technical scheme, the organic matter, gas adsorbed on the surface of particles and gas remaining in pores in the cerium-iron-boron blank can be fully discharged by adopting the twice sintering in the sintering, the purity of the cerium-iron-boron blank is improved, and the mechanical properties thereof are optimized. The twice sintering can further control the grain growth to be more uniform and smaller, significantly reducing the number and growth rate of coarse grains, and improving the remanence and intrinsic coercive force of cerium-iron-boron.

[0019] Preferably, the time of the first aging is 3-4h.

[0020] Preferably, the time of the second aging is 22-23h.

[0021] By adopting the technical scheme, the processing time in the first aging and the second aging is controlled. Within the processing time range, the number of complete cell bodies in the cerium-iron-boron is large, the regularity of the internal cellular structure and the continuity of the cell wall phase are also high, the possibility of the phenomenon of large cells swallowing small cells in the cerium-iron-boron blank is low, the pinning effect of the cellular structure on the domain wall is strong, and the enhancement of the good pinning effect can simultaneously improve the magnetic properties, high-temperature resistance and mechanical properties of cerium-iron-boron.

[0022] In the second aspect, the application provides cerium-iron-boron prepared by the above preparation method. The cerium-iron-boron has good magnetic properties and mechanical properties, the remanence can reach 1.35T or more, and the intrinsic coercive force can reach 890kA·m -1 The bending strength at 25℃ can reach 849MPa or more.

[0023] In summary, the application has the following beneficial technical effects:

[0024] 1. The preparation method of the application carries out diffusion heat treatment on the cerium iron boron green body, which can effectively improve the magnetic properties of the cerium iron boron, and almost has no effect on the mechanical strength of the cerium iron boron;

[0025] 2. The preparation method of the cerium iron boron of the application uses sheet-shaped diffusion source in grain boundary diffusion, which can improve the mechanical properties and ensure good diffusion;

[0026] 3. The preparation method of the cerium iron boron of the application strictly controls the treatment conditions of sintering, aging and diffusion heat treatment, so that the magnetic properties, high temperature resistance and mechanical properties of the cerium iron boron are significantly improved. DETAILED DESCRIPTION

[0027] Material source

[0028] The raw materials used in the application are all commercially available products, except for special instructions, which are as follows:

[0029] Nd is purchased from Jiangxi Ruida Rare Earth Co., Ltd., with a purity of 98.5%;

[0030] Ce is purchased from Baotou Jingxin Rare Earth New Material Co., Ltd., with a rare earth content of >99%;

[0031] Fe is purchased from Henan Yuanheng Powder Metallurgy Co., Ltd., with a purity of >99%;

[0032] B is purchased from Nangong Xindun Alloy Welding Material Spraying Co., Ltd., with a purity of 99%;

[0033] Cu is purchased from Bohua Snano Technology (Ningbo) Co., Ltd., with a purity of 99.95%;

[0034] Gd is purchased from Yipin Chuancheng (Beijing) Technology Co., Ltd., with a purity of 99.99%;

[0035] Ti is purchased from Dongguan Maoteng Metal Material Co., Ltd., with a purity of 99.9%;

[0036] Zr is purchased from Beijing Xingrongyuan Technology Co., Ltd., with a purity of 99%;

[0037] Pr is purchased from Suzhou Kanyang Automation Co., Ltd., with a purity of 99.9%;

[0038] Tb is purchased from Hengshui Yimei Metal Material Trade Co., Ltd., with a purity of 99.9%;

[0039] Dy is purchased from Hebei Jiuyue New Material Technology Co., Ltd., with a purity of 99.9%;

[0040] The activator is purchased from Guangzhou Yishun Chemical Co., Ltd., with an effective substance content of 99.9wt%.

[0041] The application will be further described in detail below in connection with examples and comparative examples.

[0042] Example 1.1

[0043] A preparation method of sintered cerium iron boron includes the following steps:

[0044] S11, smelting: placing Nd, Gd, Ti, Ce, Fe and B in a system with a vacuum degree of -0.1 MPa, and melting and blending at a temperature of 1500°C, and naturally cooling (2°C / min) to room temperature to obtain an alloy ingot with a formula of (Nd, Gd, Ti) 1.06 Ce 0.94 Fe 14 B;

[0045] S12, crushing and powdering: crushing the alloy ingot obtained in step S11 to a particle size of less than 10 mm, and then crushing to a particle size of less than 1 mm, and then ball-milling the coarse powder obtained after the crushing to obtain an alloy powder with a particle size of 4±0.5 μm under the protection of inert gas;

[0046] S13, magnetic field forming and isostatic pressing: under the protection of inert gas, the alloy powder obtained in step S12 is oriented and formed in an open press with a magnetic field, and the magnetic field strength is 2T, and the cerium iron boron body powder after the oriented forming is cold isostatic pressed at a pressure of 220 MPa for 35 min to obtain a cerium iron boron body green body;

[0047] S14, sintering and solid solution: placing the cerium iron boron green body obtained in step S13 in a vacuum system with a vacuum degree of 4×10 -3 Pa, and increasing the temperature to 800°C, and keeping the temperature for 4 h, and then decreasing the temperature to 900°C for 4 h of solid solution treatment to obtain a cerium iron boron blank;

[0048] S15, aging: the cerium iron boron blank obtained in step S14 is subjected to a first aging at a temperature of 800°C for 2 h under the protection of inert gas, and then the temperature is decreased to 500°C at a speed of 0.8°C / min, and a second aging is performed for 24 h, and then air cooling to room temperature to obtain a product;

[0049] S21, preparation of diffusion source: melting and blending 1 kg of a first phase alloy Pr 68 Cu 34 and 1 kg of a second phase alloy Pr 58 Tb 10 Cu 32 at a vacuum degree of 0.02 MPa and a temperature of 1350°C, and cooling, and then ball-milling under the protection of inert gas to obtain a powder-shaped diffusion source with a particle size of 2±0.5 μm;

[0050] S22, diffusion heat treatment: the product obtained in S15 is cut to obtain cerium iron boron flakes with a thickness of 1±0.05 cm, then polished using 400 mesh metallographic sandpaper to remove the surface oxide scale, and then completely immersed in an activated agent aqueous solution with a concentration of 25wt% at a temperature of 35℃, cleaned in an ultrasonic cleaner for 3 minutes to obtain impurity-removed cerium iron boron, and then each surface of the impurity-removed cerium iron boron is coated with the powdered diffusion source prepared in step S21, and diffusion is carried out at a diffusion temperature of 900℃ for 1.5h, followed by secondary diffusion at a temperature of 1080℃ for 3h, then the system is cooled to 480℃, annealed for 2.5h, and finally cooled to room temperature to obtain cerium iron boron. -3 Pa, diffusion temperature is 900℃, time is 1.5h, then secondary diffusion is carried out at a temperature of 1080℃, time is 3h, then the system is cooled to 480℃, annealed for 2.5h, and finally cooled to room temperature to obtain cerium iron boron.

[0051] Example 1.2

[0052] A method for preparing sintered cerium iron boron, comprising the following steps:

[0053] S11, melting: Nd, Ti, Zr, Ce, Fe and B are placed in a system with a vacuum degree of -0.1MPa, and are melt blended at a temperature of 1500℃, and are naturally cooled to room temperature to obtain an alloy ingot with a formula of (Nd,Ti,Zr) 1.38 Ce 0.62 Fe 14 B;

[0054] S12, crushing and powdering: the particle size of the alloy ingot prepared in step S11 is initially crushed to below 10mm, and then is medium crushed to below 1mm, and the coarse powder obtained after medium crushing is ball milled under the protection of inert gas to obtain alloy powder with a particle size of 4±0.5μm;

[0055] S13, magnetic field forming and isostatic pressing: the alloy powder prepared in step S12 is oriented and formed in an open press with a magnetic field under the protection of inert gas, and the magnetic field strength is 2T, and the cerium iron boron body powder after oriented forming is cold isostatic pressed at a pressure of 220Mpa for 35min to obtain a cerium iron boron body green body;

[0056] S14, sintering and solid solution: the cerium iron boron green body prepared in step S13 is placed in a vacuum system with a vacuum degree of 4×10 -3 Pa, and the temperature is raised to 1100℃ and kept for 3h, and then the temperature is lowered to 850℃ for 4h of solid solution treatment to obtain a cerium iron boron blank;

[0057] S15, aging: the cerium iron boron blank obtained in step S14 is subjected to a primary aging at a temperature of 800℃ for 2h under inert gas protection, then cooled to 500℃ at a rate of 0.8℃ / min, and subjected to a secondary aging for 24h, and then air-cooled to room temperature to obtain the product;

[0058] S21, preparation of diffusion source: 1kg of the first phase alloy Pr 72 Cu 28 and 0.8kg of the second phase alloy Pr 62 Tb 10 Cu 28 are melt-blended under a vacuum of -0.1MPa and at a temperature of 1300℃, cooled, and then obtained as a powder with a particle size of 2±0.5μm after ball milling under inert gas protection;

[0059] S22, diffusion heat treatment: the product obtained in S15 is cut to obtain cerium iron boron flakes with a thickness of 1±0.05cm, then polished using 400-mesh metallographic sandpaper to remove the surface oxide skin, and then completely immersed in an activated agent aqueous solution with a temperature of 35℃ and a concentration of 25wt%, cleaned in an ultrasonic cleaner for 3min to remove other surface impurities to obtain the impurity-removed cerium iron boron, and then each surface of the impurity-removed cerium iron boron is coated with the powder diffusion source prepared in step S21, and subjected to a primary diffusion under a vacuum of 4.8×10 -3 Pa and a diffusion temperature of 850℃ for 2h, and then subjected to a secondary diffusion at a temperature of 980℃ for 6h, and finally cooled to 500℃, annealed for 2h, and cooled to room temperature to obtain the cerium iron boron.

[0060] Examples 1.3-1.7

[0061] A method for preparing sintered cerium iron boron, which differs from example 1.1 in that the type of M and the value of a in step S11 are changed to obtain alloy ingots with different expressions (see Table 1), and the rest are the same as example 1.1.

[0062] Table 1

[0063] Example 1.8

[0064] A method for preparing sintered cerium iron boron, which differs from example 1.1 in that in step S11, a=1.25, and an alloy ingot with the expression (Nd,Gd,Ti) 1.25 Ce 0.75 Fe 14 B is obtained, and the rest are the same as example 1.1.

[0065] Example 1.9

[0066] A method for preparing sintered cerium iron boride, which is different from example 1.1 in that in step S11, a = 1.35, and the expression is (Nd, Gd, Ti) 1.35 Ce 0.65 Fe 14 B alloy ingot, and the rest is the same as example 1.1.

[0067] Example 2.1

[0068] A method for preparing sintered cerium iron boride, which is different from example 1.1 in that in step S11, it is cooled to room temperature at a rate of 40℃ / s, and the rest is the same as example 1.1.

[0069] Example 2.2

[0070] A method for preparing sintered cerium iron boride, which is different from example 1.1 in that in step S11, it is cooled to room temperature at a rate of 80℃ / s, and the rest is the same as example 1.1.

[0071] Example 3.1

[0072] A method for preparing sintered cerium iron boride, which is different from example 1.1 in that in step S2, a sheet-shaped diffusion source is used for diffusion heat treatment, specifically:

[0073] S21, preparation of diffusion source: 1kg of first phase alloy Pr 68 Cu 34 and 1kg of second phase alloy Pr 58 Tb 10 Cu 32 Melt and blend under the condition of vacuum degree 0.02MPa and temperature 1350℃, cool, cut, and get sheet-shaped diffusion source with thickness 0.6±0.05mm;

[0074] S22, diffusion heat treatment: cut the product obtained in S15 to get cerium iron boride sheet with thickness 1±0.05cm, then polish using 400 mesh metallographic sandpaper to remove the surface oxide skin, then completely immerse it in activated agent aqueous solution with temperature 35℃ and concentration 25wt%, clean in ultrasonic cleaner for 3 minutes, remove other impurities on the surface to get impurity-removed cerium iron boride, then wrap the sheet-shaped diffusion source obtained in step S21 on each surface of the impurity-removed cerium iron boride, and diffuse under the condition of vacuum degree 5.2×10 -3 Pa and diffusion temperature 850℃ for 8h, then cool the system to 480℃, anneal for 2.5h, and finally cool to room temperature to get cerium iron boride.

[0075] Example 3.2

[0076] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S2, a diffusion heat treatment is carried out by using a diffusion source coating, specifically:

[0077] S21, preparation of diffusion source: 1 kg of first phase alloy Pr 68 Cu 34 and 1 kg of second phase alloy Pr 58 Tb 10 Cu 32 Melt and blend under the condition of vacuum degree 0.02 MPa and temperature 1350℃, cool, dissolve in ethanol to obtain mixed liquid diffusion source;

[0078] S22, diffusion heat treatment: cut the product obtained in S15 to obtain cerium iron boride flakes with a thickness of 1±0.05 cm, then polish using 400 mesh metallographic sandpaper to remove the surface oxide skin, then completely immerse the cerium iron boride in an activated agent aqueous solution with a temperature of 35℃ and a concentration of 25wt%, clean in an ultrasonic cleaner for 3 minutes, remove other impurities on the surface to obtain impurity-removed cerium iron boride, then put the impurity-removed cerium iron boride into the mixed liquid diffusion source prepared in step S21, and use electrophoretic deposition method to deposit a layer of diffusion source coating on the impurity-removed cerium iron boride, then take out the cerium iron boride, diffuse under the condition of vacuum degree 5.2×10 -3 Pa and diffusion temperature 850℃ for 8h, then cool the system to 480℃, anneal for 2.5h, and finally cool to room temperature to obtain cerium iron boride.

[0079] Example 4.1

[0080] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S22, the time of one diffusion is 1.6h, and the rest is the same as example 1.1.

[0081] Example 4.2

[0082] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S22, the time of one diffusion is 1.8h, and the rest is the same as example 1.1.

[0083] Example 4.3

[0084] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S22, the time of one diffusion is 2h, and the rest is the same as example 1.1.

[0085] Example 4.4

[0086] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S22, the time of secondary diffusion is 4h, and the rest is the same as example 1.1.

[0087] Example 4.5

[0088] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S22, the time of secondary diffusion is 5h, and the rest is the same as example 1.1.

[0089] Example 4.6

[0090] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S22, the time of secondary diffusion is 6h, and the rest is the same as example 1.1.

[0091] Example 5.1

[0092] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S14, the sintering is divided into two times, specifically: the cerium iron boride green body is kept at a temperature of 850℃ for 1h, then heated to 1100℃ and kept for 2h again, and then solid solution is carried out.

[0093] Example 5.2

[0094] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S14, the sintering is divided into two times, specifically: the cerium iron boride green body is kept at a temperature of 800℃ for 1.5h, then heated to 1050℃ and kept for 2.5h again, and then solid solution is carried out.

[0095] Example 6.1

[0096] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S15, the treatment time of primary aging is 3h, and the rest is the same as example 1.1.

[0097] Example 6.2

[0098] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S15, the treatment time of primary aging is 4h, and the rest is the same as example 1.1.

[0099] Example 6.3

[0100] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S15, the treatment time of primary aging is 5h, and the rest is the same as example 1.1.

[0101] Example 6.4

[0102] A preparation method of sintered cerium iron boride, different from example 1.1, is that in step S15, the treatment time of primary aging is 1 h, and the rest is the same as example 1.1.

[0103] Example 6.5

[0104] A preparation method of sintered cerium iron boride, different from example 6.1, is that in step S15, the treatment time of secondary aging is 21 h, and the rest is the same as example 6.1.

[0105] Example 6.6

[0106] A preparation method of sintered cerium iron boride, different from example 6.1, is that in step S15, the treatment time of secondary aging is 22 h, and the rest is the same as example 6.1.

[0107] Example 6.7

[0108] A preparation method of sintered cerium iron boride, different from example 6.1, is that in step S15, the treatment time of secondary aging is 23 h, and the rest is the same as example 6.1.

[0109] Example 6.8

[0110] A preparation method of sintered cerium iron boride, different from example 6.1, is that in step S15, the treatment time of secondary aging is 25 h, and the rest is the same as example 6.1.

[0111] Example 6.9

[0112] A preparation method of sintered cerium iron boride, different from example 6.2, is that in step S15, the treatment time of secondary aging is 22 h, and the rest is the same as example 6.2.

[0113] Example 6.10

[0114] A preparation method of sintered cerium iron boride, different from example 6.2, is that in step S15, the treatment time of secondary aging is 23 h, and the rest is the same as example 6.2.

[0115] Comparative example 1

[0116] Different from example 1.1, step S21 and step S22 are removed, and the rest is the same as example 1.1.

[0117] Comparative example 2

[0118] Different from example 1.1, in step S21, Tb in the second phase alloy is replaced by Dy, and the expression of the second phase alloy is Pr 58 Dy10 Cu 32 The rest are the same as Example 1.1.

[0119] Comparative Example 3

[0120] The difference from Example 1.1 is that in step S21, Pr in the first phase alloy and the second phase alloy is replaced by Dy, and the expression of the first phase alloy is Dy 68 Cu 34 , and the expression of the second phase alloy is Dy 58 Tb 10 Cu 32 The rest are the same as Example 1.1.

[0121] Comparative Example 4

[0122] The difference from Example 1.1 is that in step S21, Cu in the second phase alloy is removed, and the expression of the second phase alloy is Pr 58 Tb 10 The rest are the same as Example 1.1.

[0123] Comparative Example 5

[0124] The difference from Example 1.1 is that in step S11, a = 0.8, and the expression is (Nd, Gd, Ti) 0.8 Ce 1.2 Fe 14 B alloy ingot, and the rest are the same as Example 1.1.

[0125] Comparative Example 6

[0126] The difference from Example 1.1 is that in step S11, a = 1.5, and the expression is (Nd, Gd, Ti) 1.5 Ce 0.5 Fe 14 B alloy ingot, and the rest are the same as Example 1.1.

[0127] Performance test

[0128] 1. The remanence Br and intrinsic coercive force Hcj of the sample at 25℃ were measured by using a permanent magnet material measurement system, and the results were recorded in Table 2.

[0129] 2. The bending strength (MPa) of the sample at 25℃, 300℃ was determined according to the method recorded in “Rare Earth Permanent Magnet Material Physical Property Test Method” (GB / T 31967.2-2015), using three-point bending method, continuously applying bending force to the sample until the sample was broken, and the maximum bending force was used to calculate the bending strength (MPa) and the results were recorded in Table 2.

[0130] Table 2

[0131] Data analysis:

[0132] As can be seen from Table 2, the bending strength at 25℃ of Examples 1.1-1.9 can reach 850-855MPa, the bending strength at 300℃ can reach 763-768MPa, the bending strength reduction rate is not higher than 10.25%, Br can reach 1.35-1.38T, and Hc can reach 890-896kA·m -1 , which proves that in the preparation method of cerium-iron-boron of the present application, the addition amount of cerium element is obviously improved, so the high temperature resistance of cerium-iron-boron is improved, the compressive strength reduction rate of cerium-iron-boron used at high temperature is lower, and the diffusion heat treatment of cerium-iron-boron green body can effectively improve the magnetic properties of cerium-iron-boron, while not affecting the mechanical strength of cerium-iron-boron. The bending strength reduction rate, remanence and intrinsic coercive force of cerium-iron-boron of Examples 1.8-1.9 are all higher, which proves that by strictly controlling the addition amount of Ce, the high temperature resistance, remanence and intrinsic coercive force of cerium-iron-boron can reach the optimal balance;

[0133] The remanence and intrinsic coercive force of Examples 2.1-2.2 are higher than that of Example 1.1, which proves that by limiting the cooling rate in step S1 of the present application, rapid cooling is achieved, which can greatly shorten the contact time of Ce in the alloy ingot with oxygen during the cooling process, thereby reducing the possibility of oxidation of Ce, and also reducing the number of magnetic phases in cerium-iron-boron that are oxidized and decomposed, so as to ensure that the intrinsic coercive force of cerium-iron-boron is improved;

[0134] The bending strength at 25℃ and 300℃ of Example 3.1 is much higher than that of Example 1.1, and the remanence and intrinsic coercive force are not significantly changed, and the bending strength at 25℃ and 300℃ of Example 3.2 is not significantly changed compared with Example 1.1, which proves that by using a sheet-shaped diffusion source in the grain boundary diffusion of cerium-iron-boron, both the improvement of mechanical properties and the guarantee of good diffusion can be achieved;

[0135] In Examples 1.1 and 4.1-4.3, the remanence and intrinsic coercive force of Example 4.2 are the highest, and in Examples 1.1 and 4.4-4.6, the remanence and intrinsic coercive force of Example 4.4 are the highest, which proves that by controlling the time of the first diffusion to be 1.8h and the time of the second diffusion to be 4h in the diffusion heat treatment of the present application, the grain boundary diffusion can be further promoted in the early stage of diffusion, and the bulk diffusion can be further promoted after diffusion, thereby greatly improving the magnetic properties of cerium-iron-boron;

[0136] The 25℃ bending strength and 300℃ bending strength of examples 5.1-5.2 are higher than example 1.1, and the remanence and intrinsic coercive force are higher than example 1.1, which proves that the secondary sintering in the sintering process of the present application can fully discharge the organic matter, gas adsorbed on the surface of the particles and gas stored in the pores in the cerium iron boron blank, thereby improving the purity of the cerium iron boron blank, optimizing the mechanical properties thereof, and further controlling the grain growth in the secondary sintering to be more uniform and smaller, thereby significantly reducing the number and growth rate of coarse grains, and improving the remanence and intrinsic coercive force of the cerium iron boron;

[0137] The only difference between examples 6.1-6.4 is the aging time of the first stage, according to the data, the 25℃ bending strength and 300℃ bending strength of examples 6.2-6.3 are higher, and the remanence and intrinsic coercive force are also higher than those of other examples, therefore, the present application further adjusts the aging time of the second stage based on example 6.2, and finds that the 25℃ bending strength, 300℃ bending strength, remanence and intrinsic coercive force of examples 6.7-6.8 are higher, and the present application verifies the aging time of the second stage in examples 6.7-6.8 based on example 6.3, and the 25℃ bending strength, 300℃ bending strength, remanence and intrinsic coercive force of the cerium iron boron obtained are also improved, which proves that the present application further controls the aging time of the first stage and the second stage, and within the processing time range, the number of complete cellular bodies inside the cerium iron boron is larger, the regularity of the cellular structure and the continuity of the cellular wall phase are also higher, and the phenomenon of large cells swallowing small cells in the cerium iron boron blank is less likely to occur, the pinning effect of the cellular structure on the domain wall is stronger, and the enhancement of the good pinning effect will also improve the magnetic properties, high temperature resistance and mechanical properties of the cerium iron boron;

[0138] The remanence and intrinsic coercive force of comparative example 1 are greatly reduced compared with example 1.1, which proves that the grain boundary diffusion treatment method of the present application can effectively improve the magnetic properties of the cerium iron boron;

[0139] The remanence and intrinsic coercive force of comparative examples 2-3 are greatly reduced compared with example 1.1, which proves that Pr and Tb can fully play a synergistic effect, further enhance the magnetic crystal anisotropy field strength of the surface of the cerium iron boron, and the enrichment of Tb on the surface of the magnet can also make up for the negative impact of coarse grains on the magnetic properties, further making up for the lack of magnetic properties;

[0140] The 25℃ bending strength and 300℃ bending strength of comparative example 4 are reduced compared with example 1.1, which proves that Cu can make up for the loss of mechanical strength of the cerium iron boron after adding Pr and Tb;

[0141] The remanence and intrinsic coercive force of Comparative Example 5 are greatly reduced compared to Example 1.1, and the bending strength change rate of Comparative Example 6 is greatly increased compared to Example 1.1, proving that by strictly controlling the amount of Ce added, the high-temperature resistance, remanence and intrinsic coercive force of cerium-iron-boron can be optimally balanced.

[0142] The embodiments of the present specific implementation are the preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, so that: any equivalent changes made in accordance with the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method of producing sintered cerium iron boride comprising the steps of: All raw materials are melt-blended, cooled to obtain an alloy ingot of the expression (Nd, M) a Ce 2-a Fe 14 B, and then the alloy ingot is crushed, powdered, magnetically formed, isostatically pressed, sintered, solid-solved, first aged and second aged to obtain a product, wherein a = 1.06-1.38, M is one or more of Gd, Ti and Zr, characterized in that the product is further subjected to a diffusion treatment, specifically: The first phase alloy and the second phase alloy with a weight ratio of 1:(0.8-1.0) are melt-blended at a vacuum degree of -0.1 MPa to 0.02 MPa and a temperature of 1300-1350 ℃, cooled, and after post-treatment, a diffusion source is obtained, wherein the first phase alloy is expressed as Pr x Cu 100-x , x = 68-72, and the second phase alloy is expressed as Pr y Tb 10 Cu 90-y , y = 58-62, and then the diffusion source is coated on the surface of the product, and under the conditions of a vacuum degree of 4.8 x 10 -3 -5.2 x 10 -3 Pa and a diffusion temperature of 850-900 ℃, the product is once diffused for 1.5-2 h, and then twice diffused for 3-6 h at a temperature of 980-1080 ℃, and then the system is cooled to 480-500 ℃, annealed for 1.5-2.5 h, and finally cooled to room temperature, to obtain cerium iron boron.

2. The method of claim 1, wherein: The post-processing is specifically: cutting the cooled mixture to obtain a sheet-shaped diffusion source.

3. The method of claim 1, wherein the sintered cerium iron boride is prepared by the steps of: The time of the first diffusion is 1.8 h, and the time of the second diffusion is 4 h. ​ 4. The method of claim 1, wherein the sintered cerium iron boride is prepared by the steps of: In the expression of the alloy ingot, a = 1.25-1.

35. ​ 5. The method of claim 1, wherein the sintered cerium iron boride is prepared by the steps of: After melt blending of all raw materials, cooling is performed at a rate of 40-80 ℃ / s to obtain the alloy ingot. ​ 6. The method of claim 1, wherein the sintered cerium iron boride is prepared by the steps of: The sintering is performed in two times, specifically: ​ The material obtained after isostatic pressing is kept at a temperature of 800-850 ℃ for 1-1.5 h, then heated to 1050-1100 ℃ and kept again for 2-2.5 h, and then solid solution is performed.

7. The method of claim 1, wherein the sintered cerium iron boride is prepared by the steps of: The time of the first aging is 3-4 h. ​ 8. The method of claim 7, wherein the sintered cerium iron boride is prepared by the steps of: The time of the second aging is 22-23 h. ​ 9. A cerium iron boron prepared by the method for preparing a sintered cerium iron boron according to any one of claims 1-8.

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