A method for preparing a high-abundance cerium magnet

Abstract

The application relates to a preparation method of a high-abundance cerium magnet, and belongs to the technical field of rare earth permanent magnet materials. The method is used to solve at least one of the problems that the performance of the high-abundance cerium magnet prepared by the existing method is uneven, low cost and performance improvement cannot be simultaneously considered, the preparation process is unstable, the process is complex, and the production cost is high. In the application, the total amount of Ce / rare earth is controlled in a high proportion, and the component design of the composite element addition and the size of the rapid solidification casting piece and the particle size control of the fine powder are combined. The magnet prepared by the application can balance the cost and the performance, the controllable replacement of the typical praseodymium-neodymium element by the low-price high-abundance rare earth element is realized under the condition that the proportion of Ce is greater than or equal to 50%, the cost of the sintered magnet is maximally reduced, the formation of the soft magnetic impurity phase of the cerium magnet is inhibited through component optimization, the grain boundary phase structure is stabilized, and the high-abundance cerium magnet with high magnetic performance is obtained.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials technology, and in particular to a method for preparing a high-abundance cerium magnet. Background Technology

[0002] my country possesses abundant rare earth resources, particularly cerium, a light rare earth element, which accounts for a relatively high proportion. With the development of the rare earth permanent magnet industry, the industrial production of traditional sintered rare earth permanent magnet materials, a major application area for rare earth elements, heavily relies on praseodymium and neodymium resources. This has led to a surplus of high-abundance cerium metal, and the prices of praseodymium and neodymium are significantly higher than cerium. Consequently, the development and industrial application of low-rare-earth cerium magnets are continuously being promoted to facilitate the comprehensive utilization of rare earth resources and meet the market demand for cost-effective magnets. Currently, the demand for low-cost rare earth permanent magnets is surging in fields such as industrial energy-saving motors, wind power generation, household appliances, and electric vehicles. Based on cost requirements and the goal of balanced resource utilization, the development and application of high-abundance cerium magnet production technology has become a core development direction driven by both the industry and the market.

[0003] A higher cerium content in rare-earth magnets results in lower costs. However, cerium magnets have relatively weak intrinsic properties, particularly low coercivity due to anisotropic fields. During fabrication, CeFe2 soft magnetic grain boundary phases are easily generated, disrupting the grain structure and affecting magnet performance. Existing magnet fabrication methods suffer from poor green uniformity during pressing, require secondary isostatic pressing and two-stage heat treatment, leading to complex processes, increased susceptibility to oxidation, and higher costs. Therefore, it is difficult to achieve both low cost and improved performance in high-cerium-content magnets. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a method for preparing high-abundance cerium magnets, in order to solve at least one of the following problems in existing methods: uneven performance of high-abundance cerium magnets, inability to simultaneously achieve low cost and performance improvement, unstable preparation process, complex process, and high production cost.

[0005] In a first aspect, the present invention provides a method for preparing a high-abundance cerium magnet, comprising the following steps: S1: The raw materials are prepared according to the following mass percentage composition of the magnets: (Ce x Pr y Nd 1-x-y ) a R b M c B d Fe 100-a-b-c-dWherein, 0.5≤x≤0.6, 0≤y≤0.15, 28.5≤a≤31, 0≤b≤1.5, 0.6<c≤3.3, 0.9≤d<1.2, 63≤100-abcd≤70, R is one of Gd, Dy, Ho, and M is one or more of Al, Ga, Cu, Zr, and Nb; S2: The prepared raw materials are made into castings with a thickness of ≤0.35mm, and the castings are coarsely crushed to a particle size of ≤0.35mm to obtain coarse powder; S3: The coarse powder is finely ground into fine magnetic powder with a particle size of 2.0~3.0μm. Additives are added to the fine magnetic powder and mixed evenly to obtain mixed fine magnetic powder. S4: The mixed fine magnetic powder is oriented and formed by a magnetic field press to obtain a green blank, and the green blank is directly and automatically conveyed into a vacuum heat treatment furnace under a protective atmosphere. S5: The green blank is subjected to segmented continuous heating sintering and first-stage tempering heat treatment in sequence to obtain a high-abundance cerium magnet.

[0006] Furthermore, in S3, the mass of the additive is 0.12 to 0.18% of the mass of the fine magnetic powder.

[0007] Furthermore, in S3, the fine powder preparation is carried out using an air jet mill under the protection of an inert gas, with the sorting wheel speed being 3300~4200 rpm and the pressure of the inert gas being 0.45~0.65 MPa.

[0008] Furthermore, the oxygen content in the inert gas is ≤30ppm, and the ambient temperature for mixing the magnetic powder is ≤25℃.

[0009] Furthermore, in S4, the magnetic field strength is ≥2.0T, the forming pressing speed is 1~3mm / s, and the density of the green blank is ≥4.1g / cm³. 3 .

[0010] Furthermore, in S4, the mixed fine magnetic powder is automatically distributed and loaded into the magnetic field at a pressure of 0.04~0.1MPa.

[0011] Furthermore, the segmented continuous heating sintering involves heating from room temperature to 900°C at a heating rate of 2-4°C / min, and then heating from 900°C to the sintering temperature at a heating rate of 5-10°C / min.

[0012] Furthermore, the sintering temperature is 1000~1030℃, and the sintering time is 2~5h.

[0013] Furthermore, in S5, the tempering temperature is 560~630℃, and the holding time is 3~6h.

[0014] Furthermore, in S5, the total carbon and oxygen content of the high-abundance cerium magnet is ≤1000ppm, the magnetic energy product is ≥30MGOe, and the remanence deviation of the magnetic properties is ≤0.5%.

[0015] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. This invention controls the total Ce / rare earth content at a high ratio, and combines the composition design of composite element addition with the control of the size of the rapidly solidified casting sheet and the fine powder particle size. The magnet prepared by this invention can balance cost and performance. Under the condition that the Ce content is ≥50%, it achieves the controllable substitution of typical praseodymium and neodymium elements with low-cost and high-abundance rare earth elements, minimizes the cost of sintered magnets, and suppresses the formation of soft magnetic impurity phases in cerium magnets through composition optimization, stabilizes the grain boundary phase structure, and obtains high-abundance cerium magnets with high magnetic properties.

[0016] 2. This invention improves the flowability of magnetic powder by controlling the particle size of fine magnetic powder and adding additives. Combined with automatic pressure powder distribution, it enhances the initial powder distribution density and consistency of the formed magnetic powder. By utilizing the optimal powder distribution density and high magnetic field orientation in conjunction with speed-controlled pressing, it achieves one-time forming of high-oriented, high-density green bodies without the need for secondary isostatic pressing. The green bodies are directly and automatically loaded into a vacuum heat treatment furnace, reducing the risk of magnet exposure, shortening the process flow, and lowering production costs. At the same time, it ensures high orientation, density, and uniformity of the formed magnets, and reduces the impurity content and sintering temperature of the green body, laying the foundation for obtaining highly uniform magnetic properties.

[0017] 3. This invention employs segmented continuous heating sintering to suppress magnet grain growth and improve the consistency of shrinkage thermal deformation. After sintering, the magnet is first rapidly cooled to room temperature and then subjected to a first-stage tempering treatment. The first-stage tempering heat treatment optimizes the grain boundary structure, retains extremely low impurity content in the magnet, shortens the heat treatment process, obtains excellent cerium magnet magnetic properties, and further reduces production process costs.

[0018] 4. The preparation method of this invention solves the technical problem of stable and efficient production of high-performance, low-cost magnets through synergistic process control throughout the entire process. The high-abundance cerium magnets prepared by this invention have a total carbon and oxygen content ≤1000ppm, a magnetic energy product ≥30MGOe, and a remanence deviation of ≤0.5% for consistent magnetic properties.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 Typical demagnetization curves of different parts of the high-abundance cerium magnet prepared in Example 1 of the present invention. Detailed Implementation

[0022] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0023] A specific embodiment of the present invention discloses a method for preparing a high-abundance cerium magnet, comprising the following steps: S1: The raw materials are prepared according to the following mass percentage composition of the magnets: (Ce x Pr y Nd 1-x-y ) a R b M c B d Fe 100-a-b-c-d Wherein, 0.5≤x≤0.6, 0≤y≤0.15, 28.5≤a≤31, 0≤b≤1.5, 0.6<c≤3.3, 0.9≤d<1.2, 63≤100-abcd≤70, R is one of Gd, Dy, Ho, and M is one or more of Al, Ga, Cu, Zr, and Nb; S2: The prepared raw materials are made into castings with a thickness of ≤0.35mm, and the castings are coarsely crushed to a particle size of ≤0.35mm to obtain coarse powder; S3: The coarse powder is finely ground into fine magnetic powder with a particle size of 2.0~3.0μm (e.g., 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm). Additives are added to the fine magnetic powder and mixed evenly to obtain mixed fine magnetic powder. S4: The mixed fine magnetic powder is oriented and formed by a magnetic field press to obtain a green blank, and the green blank is directly and automatically conveyed into a vacuum heat treatment furnace under a protective atmosphere. S5: The green blank is subjected to segmented continuous heating sintering and first-stage tempering heat treatment in sequence to obtain a high-abundance cerium magnet.

[0024] Compared with existing technologies, this invention controls the total Ce / rare earth content at a high ratio, combines the composition design of composite element addition with rapid solidification casting scale and magnetic powder control, and the magnets prepared by this invention can balance cost and performance. Under the condition that the Ce content is ≥50%, it achieves controllable substitution of typical praseodymium and neodymium elements with low-cost and high-abundance rare earth elements, minimizes the cost of sintered magnets, and suppresses the formation of soft magnetic impurity phases in cerium magnets through composition optimization, stabilizes the grain boundary phase structure, and obtains high-abundance cerium magnets with high magnetic properties.

[0025] It should be noted that in S1, when R and M take multiple elements, the proportions of the elements can be arbitrary.

[0026] In S2, the prepared raw materials are vacuum melted, rapidly solidified, and spun into cast sheets.

[0027] Specifically, in S3, the mass of the additive is 0.12 to 0.18% of the mass of the fine magnetic powder, for example, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, or 0.18%.

[0028] The additives selected are adapted to the preparation process of this invention by the above-mentioned addition ratio, which improves the flowability of magnetic powder, thereby helping to improve performance and uniformity. Adding too little will not easily improve flowability, while adding too much will reduce performance and increase impurity content.

[0029] It should be noted that the additives described in this invention can form a lubricating protective film between magnetic powder particles, reducing particle agglomeration and friction, improving flowability during compaction, and enhancing process stability and green uniformity. The additives in this invention are all commonly used additives in the prior art, such as lubricants and / or antioxidants.

[0030] Specifically, in S3, the fine powder preparation is carried out using an air jet mill under the protection of an inert gas. The sorting wheel speed is 3300~4200 rpm (e.g., 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200). The pressure of the inert gas is 0.45~0.65 MPa, e.g., 0.45 MPa, 0.47 MPa, 0.49 MPa, 0.5 MPa, 0.52 MPa, 0.54 MPa, 0.56 MPa, 0.58 MPa, 0.60 MPa, 0.62 MPa, 0.64 MPa, 0.65 MPa.

[0031] By selecting an inert gas pressure within the above-mentioned range, magnetic powder particles with a size of 2.0~3.0μm can be obtained, enabling normal process preparation. If the pressure is too high or too low, the above particle size range cannot be obtained, the process parameters will not match, and the steps will be difficult to implement.

[0032] Preferably, the inert gas is Ar.

[0033] Specifically, in S3, the mixing time is 0.5~2h, for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h.

[0034] Preferably, the oxygen content in the inert gas is ≤30ppm, and the mixing ambient temperature is ≤25℃.

[0035] Specifically, in S4, the magnetic field strength is ≥2.0T, for example, 2.0T, 2.1T, 2.2T, 2.3T, 2.4T, 2.5T, 2.6T, 2.7T, 2.8T, or 2.9T; the forming pressing speed is 1~3mm / s, for example, 1mm / s, 1.2mm / s, 1.4mm / s, 1.6mm / s, 1.8mm / s, 2mm / s, 2.2mm / s, 2.4mm / s, 2.6mm / s, 2.8mm / s, or 3mm / s; and the density of the green compact is ≥4.1g / cm³. 3 .

[0036] Choosing the above-mentioned magnetic field strength and pressing speed can achieve good orientation and pressing uniformity. Too low a value will result in insufficient orientation or low efficiency, while too high a value will result in poor uniformity.

[0037] Specifically, in S4, the mixed fine magnetic powder is automatically distributed and loaded into the magnetic field at a pressure of 0.04~0.1MPa, for example, 0.04MPa, 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, 0.09MPa, or 0.1MPa.

[0038] Choosing the powder pressure magnets described above can achieve high orientation and uniformity, laying the foundation for ultimately obtaining high-performance, highly uniform magnets. High or low pressure will reduce magnet performance.

[0039] It should be noted that in S4, the green blank is not subjected to isostatic pressing and secondary packaging, but is directly and automatically conveyed to a vacuum heat treatment furnace for heat treatment under the protection of an inert atmosphere. The total operation time of the pressing and automatic feeding process is ≤3h, and the oxygen content of the atmosphere is ≤50ppm.

[0040] Specifically, in S5, the segmented continuous heating sintering involves heating from room temperature to 900°C at a heating rate of 2~4°C / min (e.g., 2°C / min, 2.2°C / min, 2.4°C / min, 2.6°C / min, 2.8°C / min, 3.0°C / min, 3.2°C / min, 3.4°C / min, 3.6°C / min, 3.8°C / min, 4°C / min), and then heating from 900°C to the sintering temperature at a heating rate of 5~10°C / min (5°C / min, 5.5°C / min, 6°C / min, 6.5°C / min, 7°C / min, 7.5°C / min, 8°C / min, 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min).

[0041] Preferably, the sintering temperature is 1000~1030℃, for example, 1000℃, 1005℃, 1010℃, 1015℃, 1020℃, 1025℃, 1030℃, and the sintering time is 2~5h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h.

[0042] Specifically, in S5, the tempering temperature is 560~630℃, for example, 560℃, 565℃, 570℃, 575℃, 580℃, 585℃, 590℃, 595℃, 600℃, 605℃, 610℃, 615℃, 620℃, 625℃, 630℃, and the temperature is maintained for 3~6 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours.

[0043] It should be noted that the present invention uses segmented continuous heating sintering to suppress the growth of magnet grains and improve the consistency of shrinkage thermal deformation. After sintering, the magnet is first rapidly cooled to room temperature and then subjected to a first-stage tempering treatment. The first-stage tempering heat treatment is used to optimize the grain boundary structure, retain the extremely low impurity content of the magnet, shorten the heat treatment process, obtain excellent cerium magnet magnetic properties, and further reduce the production process cost.

[0044] Specifically, in S5, the total carbon and oxygen content of the high-abundance cerium magnet is ≤1000ppm, the magnetic energy product is ≥30MGOe, and the remanence deviation of the magnetic properties is ≤0.5%.

[0045] This invention improves the flowability of magnetic powder by controlling and combining it with automatic pressure powder distribution to enhance the initial powder density and uniformity of the formed magnetic powder. It utilizes optimal powder density and high magnetic field orientation in conjunction with speed-controlled pressing to achieve one-time forming of highly oriented, high-density green bodies without secondary isostatic pressing. Furthermore, the green bodies are automatically loaded into a vacuum heat treatment furnace for heat treatment, reducing the risk of magnet exposure, shortening the process flow, and lowering production costs. This ensures high orientation, density, and uniformity of the formed magnets while reducing impurity content and sintering temperature in the green body, laying the foundation for highly uniform magnetic properties. Simultaneously, a segmented continuous low-temperature sintering process is used to suppress magnet grain growth and improve the uniformity of shrinkage thermal deformation. A single-stage tempering heat treatment optimizes the grain boundary structure, retaining extremely low impurity content in the magnets, shortening the heat treatment process, and obtaining excellent cerium magnet magnetic properties, while further reducing production costs.

[0046] In summary, the preparation method of this invention achieves one-time high-orientation green compact densification through the control of high-Ce content magnet alloy powder. Combined with an automated conveying process and continuous single-stage heat treatment, it effectively improves magnet performance and short-process control, achieving efficient utilization of high-abundance rare-earth cerium. While maintaining the high magnetic properties of cerium magnets, it significantly improves the cost-effectiveness of magnets, realizing efficient batch automated preparation of high-energy-product cerium magnets. This method is suitable for low-cost, green, and low-carbon production of high-abundance cerium magnets. The preparation method of this invention solves the technical problems of stable and efficient production of high-performance, low-cost magnets through synergistic process control throughout the entire process.

[0047] The technical solution of the present invention will be further explained below with reference to specific embodiments. The following embodiments use lubricants and antioxidants as examples for explanation, but are not limited to these.

[0048] Example 1 This embodiment of a method for preparing a high-abundance cerium magnet includes the following steps: S1: The raw materials are prepared according to the following mass percentage composition of the magnet: (Ce 0.57 Pr 0.10 Nd 0.33 ) 30.1 R 0.5 M 2.6 B 0.97 Fe 65.83 R represents Gd, and M represents Al, Ga, Cu, or Zr. S2: The prepared raw materials are vacuum melted and rapidly solidified to form castings with a thickness of ≤0.35mm. The castings are then coarsely crushed to a particle size of ≤0.35mm to obtain coarse powder. S3: Using Ar as a protective gas, the coarse powder is ground into fine magnetic powder with a particle size of 2.1μm using an air jet mill. The gas pressure during the preparation of fine magnetic powder is 0.55~0.60MPa, and the sorting wheel speed is controlled at 4100 rpm. An additive is added to the fine magnetic powder, and the mass of the additive is 0.15% of the mass of the fine magnetic powder. The powder is circulated and mixed for 2 hours under Ar gas protection. The oxygen content in the protective gas is ≤20ppm, the ambient temperature is ≤20℃, and the powder is mixed evenly to obtain a mixed fine magnetic powder with good flowability. S4: The mixed fine magnetic powder is automatically distributed via a protective gas (Ar) and loaded into a molding die capable of withstanding a 2T orientation magnetic field. An initial loading density is established using a 0.08MPa pressure to ensure uniform powder distribution and achieve optimal density and distribution. The powder is then slowly and continuously pressed at a pressing speed of 1mm / s to achieve a density of 4.2g / cm³. 3 The green blank is placed directly into the material box by an automatic feeding system under a closed protection and then loaded into a vacuum heat treatment furnace. The process of pressing the powder into green blank and automatic feeding takes ≤1 hour, and the oxygen content of the controlled atmosphere is below 30ppm. S5: The green blank is subjected to segmented continuous heating sintering and tempering heat treatment in sequence; The segmented continuous heating sintering process specifically involves: heating from room temperature to 900℃ at a rate of 2℃ / min, then heating from 900℃ to sintering temperature of 1010℃ at a rate of 6℃ / min, with a sintering holding time of 3 hours; after sintering, the blank is first rapidly cooled to room temperature, then subjected to a first-stage tempering treatment at a tempering heat treatment temperature of 610℃, with a holding time of 3 hours, and then rapidly cooled to room temperature before being removed from the furnace to obtain a high-abundance cerium magnet.

[0049] At least nine different locations of the high-abundance cerium magnet prepared according to this invention were sampled and tested for magnetic properties according to standards. The demagnetization curves for the maximum and minimum magnetic properties are shown below. Figure 1 As shown, the performance consistency of the magnet is obtained by calculating the maximum deviation between the maximum and minimum values ​​of the remanent magnet Br. The figure shows that the magnet prepared in this embodiment exhibits excellent uniformity and consistency in magnetic properties.

[0050] Example 2 The method for preparing a high-abundance cerium magnet in this embodiment is similar to that in Embodiment 1, except that in S3, the air jet mill separation wheel rotates at 3700 rpm, the gas pressure during the fine magnetic powder preparation process is 0.50~0.55 MPa, and the magnetic powder particle size is 2.7 μm. An additive with a mass ratio of 0.18% is added. The oxygen content is ≤30 ppm, and the ambient temperature is below 25°C.

[0051] In S4, under automatic powder distribution pressure of 0.1 MPa and pressing speed of 2 mm / s, a single continuous pressing process produces a product with a density of 4.1 g / cm³.3 High-density green body.

[0052] In S5, the sintering temperature is 1028℃ and the holding time is 2.5h, and the tempering temperature is 590℃ and the holding time is 5h.

[0053] Example 3 The method for preparing a high-abundance cerium magnet in this embodiment is similar to that in Embodiment 1, except that in S1, the magnet composition is (Ce) 0.50 Pr 0.15 Nd 0.35 ) 29.3 R 1.0 M 3.2 B 0.90 Fe 65.60 R represents Dy, and M represents Al, Ga, Cu, Zr, and Nb. In S3, the air jet mill's sorting wheel rotates at 3300 rpm, the fine magnetic powder has a particle size of 3.0 μm, the additive's mass is 0.12% of the fine magnetic powder's mass, and the powder is circulated and mixed for 0.5 h under Ar gas protection, with an oxygen content ≤10 ppm in the protective gas and an ambient temperature ≤20℃. In S4, the powder distribution pressure is 0.05 MPa, the magnetic field strength is 2.1 T, and the green body density is 4.3 g / cm³. 3 The operation time for green pressing and automatic feeding processes is ≤0.5h, and the oxygen content in the controlled atmosphere is ≤15ppm; In S5, the temperature is increased from room temperature to 900℃ at a rate of 3℃ / min, then increased from 900℃ to sintering temperature of 1030℃ at a rate of 5℃ / min, and held for 2 hours. The tempering treatment temperature is 570℃, and held for 6 hours.

[0054] Example 4 The method for preparing a high-abundance cerium magnet in this embodiment is similar to that in Embodiment 1, except that in S1, the magnet composition is (Ce) 0.60 Nd 0.40 ) 29 R 1.5 M 1.9 B 1.1 Fe 66.5 R represents Gd, and M represents Al, Ga, Zr, and Nb; In S3, the gas pressure during the fine magnetic powder preparation process under a protective atmosphere is 0.60~0.65MPa, the sorting wheel speed is controlled at 3700 rpm, and the fine magnetic powder particle size is 2.5μm. In S4, the density of the green body is 4.4 g / cm³. 3 The operation time for green pressing and automatic feeding processes shall not be less than 2 hours, and the oxygen content of the controlled atmosphere shall be less than 30 ppm. In S5, the temperature is increased from room temperature to 900℃ at a rate of 4℃ / min, and then increased from 900℃ to 1022℃ at a rate of 8℃ / min. The tempering treatment temperature is 590℃, and the temperature is held for 5 hours.

[0055] Comparative Example 1 The preparation method of a high-abundance cerium magnet in this comparative example is similar to that in Example 1, except that in S3, the oxygen content of the protective gas is controlled to be ≤50ppm and the ambient temperature is higher than 25℃. In S4, instead of automatic powder distribution, the mixed fine powder is poured in directly, and the pressing speed is 5mm / s.

[0056] Comparative Example 2 The preparation method of this comparative example of a high-abundance cerium magnet is similar to that of Example 1, except that in S4, the powder distribution pressure is 0.2 MPa and the green density is 3.8 g / cm³. 3 The green billets are not directly transported to the furnace, but are sealed and transferred before being put into the furnace. The time exceeds 5 hours, and the oxygen content in the atmosphere is ≤100ppm.

[0057] Comparative Example 3 The preparation method of this comparative example of a high-abundance cerium magnet is similar to that of Example 1, except that in S5, segmented continuous heating sintering is not performed. Instead, sintering is carried out by heating from room temperature to 1040℃ for 3 hours at a heating rate of 5℃ / min. The heat treatment adopts a two-stage tempering process, that is, holding at 900℃ for 1 hour and then holding at 650℃ for 3 hours.

[0058] Comparative Example 4 The preparation method of the high-abundance cerium magnet in this comparative example is similar to that in Example 1, except that in S1, the magnet composition is (Ce) 0.65 Pr 0.10 Nd 0.25 ) 30.1 R 0.5 M 2.6 B 0.97 Fe 65.83 R represents Ho, and M represents Al, Ga, or Cu. In S2, the thickness of the cast sheet is ≤0.45mm; In S3, the fine magnetic powder is defined as 3.3 μm, and the mass of the additive is 0.25% of the mass of the fine magnetic powder. The powder is circulated and mixed for 2 hours.

[0059] Experimental Example 1 The demagnetization curves of the high-abundance cerium magnets prepared in the examples and comparative examples were tested respectively to obtain the magnetic properties of the magnets (tested according to GB / T 3217-2013) and the remanence consistency was calculated (using the same method as in Example 1, expressed as the maximum deviation). The results are shown in Table 1.

[0060] Table 1

[0061] As can be seen from Table 1, Examples 1-4 have significantly better magnetic energy products and remanence consistency than the comparative examples. The magnetic energy product of the magnet is ≥30MGOe, the remanence deviation of magnetic performance consistency is ≤0.5%, and the total carbon and oxygen content is ≤1000ppm.

[0062] Comparative Example 1 suffered from poor atmosphere and temperature control during the preparation process, lack of automatic powder feeding under pressure, and relatively fast pressing speed, resulting in a decrease in orientation and consistency. At the same time, the increased impurity content led to a decrease in the magnetic energy product of the magnet and affected the consistency compared to the Example.

[0063] Comparative Example 2 suffered from a sharp deterioration in magnetic energy product and remanence uniformity due to improper magnetic powder distribution conditions and pressing process, as well as the introduction of more impurities through intermediate steps.

[0064] Comparative Example 3 suffered from uneven grain size and grain boundary phase structure due to poor sintering and tempering processes. At the same time, the magnet was deformed significantly, resulting in a decrease in magnetic properties and remanence consistency compared to the Example.

[0065] In Comparative Example 4, due to the high amount of rare earth cerium added and the poor alloy rapid solidification and spinning process, even with changes in the magnetic powder particle size and an increase in the amount of composite additives to enhance the magnetic powder flowability, the difference in magnetic energy product was significant even without improvement in the uniformity of remanence of the magnet.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-abundance cerium magnet, characterized in that, Includes the following steps: S1: The raw materials are prepared according to the following mass percentage composition of the magnets: (Ce x Pr y Nd 1-x-y ) a R b M c B d Fe 100-a-b-c-d Wherein, 0.5≤x≤0.6, 0≤y≤0.15, 28.5≤a≤31, 0≤b≤1.5, 0.6<c≤3.3, 0.9≤d<1.2, 63≤100-abcd≤70, R is one of Gd, Dy, Ho, and M is one or more of Al, Ga, Cu, Zr, and Nb; S2: The prepared raw materials are made into castings with a thickness of ≤0.35mm, and the castings are coarsely crushed to a particle size of ≤0.35mm to obtain coarse powder; S3: The coarse powder is finely ground into fine magnetic powder with a particle size of 2.0~3.0μm. Additives are added to the fine magnetic powder and mixed evenly to obtain mixed fine magnetic powder. S4: The mixed fine magnetic powder is oriented and formed by a magnetic field press to obtain a green blank, and the green blank is directly and automatically conveyed into a vacuum heat treatment furnace under a protective atmosphere. S5: The green blank is subjected to segmented continuous heating sintering and first-stage tempering heat treatment in sequence to obtain a high-abundance cerium magnet.

2. The method for preparing a high-abundance cerium magnet according to claim 1, characterized in that, In S3, the mass of the additive is 0.12 to 0.18% of the mass of the fine magnetic powder.

3. The method for preparing a high-abundance cerium magnet according to claim 1, characterized in that, In S3, the fine powder preparation is carried out by air jet milling under the protection of inert gas, the sorting wheel speed is 3300~4200 rpm, and the pressure of the inert gas is 0.45~0.65 MPa.

4. The method for preparing a high-abundance cerium magnet according to claim 3, characterized in that, The oxygen content in the inert gas is ≤30ppm, and the ambient temperature for mixing the magnetic powder is ≤25℃.

5. The method for preparing a high-abundance cerium magnet according to claim 1, characterized in that, In S4, the magnetic field strength is ≥2.0T, the forming pressing speed is 1~3mm / s, and the density of the green body is ≥4.1g / cm³. 3 .

6. The method for preparing a high-abundance cerium magnet according to any one of claims 1-3, characterized in that, In S4, the mixed fine magnetic powder is automatically distributed and loaded into the magnetic field at a pressure of 0.04~0.1MPa.

7. A method for preparing a high-abundance cerium magnet according to any one of claims 1-3, characterized in that, The segmented continuous heating sintering involves heating from room temperature to 900°C at a heating rate of 2-4°C / min, and then heating from 900°C to the sintering temperature at a heating rate of 5-10°C / min.

8. The method for preparing a high-abundance cerium magnet according to claim 7, characterized in that, The sintering temperature is 1000~1030℃, and the sintering time is 2~5h.

9. The method for preparing a high-abundance cerium magnet according to claim 1, characterized in that, In S5, the tempering temperature is 560~630℃, and the holding time is 3~6h.

10. The method for preparing a high-abundance cerium magnet according to claim 1, characterized in that, In S5, the total carbon and oxygen content of the high-abundance cerium magnet is ≤1000ppm, the magnetic energy product is ≥30MGOe, and the remanence deviation of the magnetic properties is ≤0.5%.

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