A method for preparing high resistivity and high mechanical strength sintered samarium cobalt permanent magnets

Abstract

This invention discloses a method for preparing high-resistivity, high-mechanical-strength sintered samarium-cobalt permanent magnets. The main steps of this method are as follows: samarium-cobalt alloy is subjected to air jet milling, and ultrafine magnetic powder A0, base material B0, and qualified magnetic powder CO generated during the air jet milling process are collected separately; the ultrafine magnetic powder A0 is controlled-actuated to obtain magnetic powder A1; the base material B0 is sequentially hydrogenated and air jet milled to obtain magnetic powder B2; magnetic powder A1, magnetic powder B2, and qualified magnetic powder CO are mixed uniformly to obtain mixed magnetic powder D; the mixed magnetic powder D is oriented and shaped to obtain a samarium-cobalt green blank E, and then the samarium-cobalt green blank E is made into a sintered samarium-cobalt permanent magnet. The sintered samarium-cobalt magnets prepared by this method simultaneously possess high resistivity and high mechanical strength, and fully utilize the two residual powders—ultrafine powder and base material—generated during the samarium-cobalt alloy air jet milling process, thereby improving the yield of samarium-cobalt alloy air jet milling powder, increasing resource utilization, and reducing production costs and energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet preparation technology, specifically relating to a method for preparing a high resistivity and high mechanical strength sintered samarium cobalt permanent magnet. Background Technology

[0002] Samarium cobalt permanent magnets, as second-generation rare-earth permanent magnets, mainly come in two types: 1:5 (SmCo5) and 2:17 (Sm2Co). 17 (Two types). Its main characteristics are high magnetic properties, good temperature stability, and strong corrosion resistance. Compared with neodymium iron boron permanent magnets, samarium cobalt permanent magnets are more suitable for working in high-temperature environments, making them ideal for manufacturing various high-performance permanent magnet motors and products used in complex working environments. However, due to the low reserves of samarium, the main component of samarium cobalt permanent magnets, their price is very high. Therefore, recycling the waste generated during the air jet milling process of samarium cobalt permanent magnets and reusing it to prepare samarium cobalt permanent magnets that meet performance requirements is an effective way to reduce costs and improve the comprehensive utilization rate of resources.

[0003] The production process of samarium-cobalt permanent magnets mainly includes alloy smelting, mechanical crushing, air jet milling, orientation forming, sintering, solution treatment, and aging heat treatment. During the air jet milling process, samarium-cobalt alloys produce two types of non-compliant residual powders: bottom material and ultrafine powder, accounting for approximately 5-10 wt% of the total production. The ultrafine powder contains the precious rare earth element Sm (approximately 27-40%), a proportion far higher than that of ordinary compliant magnetic powder (23-27%), making it highly valuable for recycling. Although the bottom material contains a slightly lower proportion of Sm (approximately 10-25%) than ordinary compliant magnetic powder, the relative proportion is still significant, retaining important recycling value. Therefore, fully utilizing both the ultrafine powder and the bottom material can greatly recover strategic metals such as Sm and Co, improving the comprehensive utilization rate of resources and reducing production costs and energy consumption.

[0004] With the application of samarium cobalt magnets in small, high-precision instruments, higher requirements have been placed on their processing accuracy, mechanical reliability, and resistivity. To improve the mechanical properties of samarium cobalt magnets, the industry has made many attempts. For example, patent CN202110748910.8 discloses using atomized mixed powder of FeCoNi-based high-entropy alloy and nickel-based hard alloy to impact the surface of samarium cobalt magnets, creating microcracks on the surface. These microcracks are effectively filled with the mixed powder, and then tempering heat treatment is applied to obtain samarium cobalt permanent magnets with high toughness and high coercivity. Patent ZL201610377494.4 invented a method to improve the mechanical properties of samarium cobalt permanent magnets by doping with silver powder; patent CN202010842920.3 disclosed a method to optimize the strength and toughness of grain boundary phases by adding tough copper-based nanowires and carbon nanotubes; patent CN202111164098.0 disclosed a method to effectively improve the toughness of magnets by adding an appropriate amount of nano-Zn powder to coat nano-TiN powder in samarium cobalt magnet materials. To improve magnet resistance, patent ZL200910227793.X invented a method to increase the resistivity of permanent magnets by adding titanate coupling agents, bisphenol A epoxy resin, and bisphenol F epoxy resin. Patent ZL201810074109.8 invented a method to increase the resistivity of permanent magnets by adding high-resistivity elements such as In, Ca, and Si. Patent CN201910536878.X mentions adding solid surfactants and polar solvents to dry-milled magnetic powder, followed by wet milling to prepare high-resistivity magnets. Patent CN202110924270.1 discloses a method to improve resistivity by coating and laser-cladding a mixture of nanocrystalline magnetic powder, inorganic insulating nanoscale materials, and nanoscale fluorides onto the magnet surface. These methods can only improve either the mechanical properties or the resistivity of samarium-cobalt magnets. How to prepare samarium-cobalt magnets that simultaneously possess high resistivity and high strength remains a major challenge in the industry. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing high resistivity and high mechanical strength sintered samarium cobalt permanent magnets. By processing and doping the base material and ultrafine magnetic powder generated during the samarium cobalt alloy air jet milling process, both residual powders are fully recycled, thereby greatly recovering strategic metals such as Sm and Co, saving non-renewable resources, and improving the comprehensive utilization rate of waste resources. Furthermore, the sintered samarium cobalt magnets prepared by this method have both high resistivity and high mechanical strength, reducing eddy current losses during use, ensuring their application in strong impact and vibration environments, and effectively extending their service life.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a high-resistivity, high-mechanical-strength sintered samarium-cobalt permanent magnet, comprising the following steps:

[0008] Samarium-cobalt alloys are available.

[0009] The samarium-cobalt alloy was subjected to air jet milling, and the ultrafine magnetic powder A0, the bottom material B0, and the qualified magnetic powder C0 generated during the air jet milling process were collected respectively.

[0010] The ultrafine magnetic powder A0 is subjected to controlled oxidation to obtain magnetic powder A1;

[0011] The base material B0 is hydrogenated to obtain hydrogenated magnetic powder B1, and then the hydrogenated magnetic powder B1 is subjected to air jet milling to obtain magnetic powder B2.

[0012] The magnetic powder A1, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly to obtain mixed magnetic powder D;

[0013] After the mixed magnetic powder D is oriented and shaped to obtain a samarium cobalt green blank E, the samarium cobalt green blank E is then made into a sintered samarium cobalt permanent magnet.

[0014] The samarium-cobalt alloy described in this article has the following composition: Sm(Co) 1-a-b-c Fe a Cu b Zr c ) z , where 8.1≥z≥7.2, 0.2≥a≥0.4, 0.09≥b≥0.05, 0.01≥c≥0.04.

[0015] The ultrafine magnetic powder A0 described in this article has a particle size of 0.01-2μm and an oxygen content of 4000-10000ppm; the base material B0 has an iron content of 18%-30wt% and a particle size of 4-20μm; and the qualified magnetic powder C0 has a particle size of 2-4μm.

[0016] In a further embodiment, the collection of the base material B0 and the qualified magnetic powder C0 is carried out in a protective gas atmosphere with an oxygen content of <150ppm and under temperature control.

[0017] Preferably, the protective gas is selected from at least one of nitrogen or rare gases (such as helium, argon, etc.);

[0018] Preferably, the temperature control condition is that the temperature of both the powder and the ambient atmosphere does not exceed 30°C.

[0019] In a further embodiment, the controllable oxidation is achieved by controlling the contact time and temperature of the ultrafine magnetic powder A0 with air;

[0020] Preferably, the temperature for the controlled oxidation is 26-30°C;

[0021] Preferably, the controllable oxidation process is as follows: after oxidizing the ultrafine magnetic powder A0 for 10 minutes, the oxidation is stopped and the oxygen content is tested until the oxygen content reaches the target range of 15,000-35,000 ppm.

[0022] In a further embodiment, the hydrogenation treatment temperature is 30-300℃, the hydrogen pressure is 0.1-3MPa, and the hydrogen content of the hydrogenated magnetic powder B1 is 1000-2000ppm.

[0023] In a further embodiment, the particle size of the magnetic powder B2 is 3-10 μm.

[0024] In a further embodiment, in the mixed magnetic powder D, the mass ratio of magnetic powder A1 to magnetic powder B2 is 1:9-3:7, and the total mass of magnetic powder A1 and magnetic powder B2 is matched with the mass of qualified magnetic powder C0 in a ratio of 1:9-1:1.

[0025] In a further embodiment, to prevent further oxidation of the mixed magnetic powder D, preferably, 0.1wt‰-0.5wt‰ of an antioxidant is added to the mixed magnetic powder D. The antioxidant can be a conventional choice in the art, and specific examples include, but are not limited to, at least one of butylated hydroxyanisole, butylated hydroxytoluene, and tert-butylhydroquinone.

[0026] In a further embodiment, it is understood that the step of forming the samarium cobalt green blank E into a sintered samarium cobalt permanent magnet also includes conventional sintering, solution treatment, and aging treatment in the art; wherein, the specific sintering, solution treatment, and aging treatment can be performed according to parameters well known to those skilled in the art. In some specific embodiments of the present invention, the sintering temperature is 1200-1250°C; and / or, the solution treatment temperature is 1120-1190°C; and / or, the aging treatment temperature is 800-860°C.

[0027] The present invention has the following beneficial effects:

[0028] This invention addresses the issue of substandard residual powders, such as the bottom material and ultrafine magnetic powder, generated during the air jet milling process of samarium-cobalt alloys. Specifically, the ultrafine magnetic powder undergoes controlled oxidation, while large particles in the bottom material are subjected to hydrogen absorption and air jet milling to break them down to 3-10 μm. The treated bottom material, ultrafine magnetic powder, and qualified magnetic powder are then mixed to prepare samarium-cobalt permanent magnets.

[0029] The prepared sintered samarium-cobalt permanent magnets incorporate a significant amount of rare-earth oxides due to the introduction of these oxides from the ultrafine magnetic powder. This increases the magnet's resistivity, while the oxides also pin grain boundaries, hindering grain growth and enhancing the magnet's strength. Furthermore, the three types of magnetic powder with significantly different particle sizes form a heterogeneous structure with varying grain sizes within the magnet, improving its bending strength. This invention achieves low-energy consumption and high-efficiency recovery of both the samarium-cobalt alloy air-jet mill substrate and the ultrafine magnetic powder, providing a novel method for preparing high-resistivity, high-mechanical-strength samarium-cobalt magnets. Attached Figure Description

[0030] Figure 1 The images are SEM images of ultrafine magnetic powder A0 and base material B0 in Example 1, respectively.

[0031] Figure 2 They are respectively Figure 1 Particle size distribution diagrams of ultrafine magnetic powder A0 and base material B0;

[0032] Figure 3 This is the heterogeneous structure model formed in this invention; where CG represents coarse grain, MG represents medium-sized grain, and FG represents fine grain. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0035] This invention prepares a non-uniform structure (such as) by interdoping this base material and ultrafine powder. Figure 3As shown, samarium-cobalt magnets can enhance mechanical properties. On the other hand, ultrafine powder, due to its small particle size, large specific surface area, and high content of the rare earth element samarium, more easily combines with oxygen to form Sm₂O₃ particles, thus exhibiting a high oxide content. When the proportion of ultrafine powder is high, the oxide content of the resulting magnet increases. The high-melting-point Sm₂O₃ particles can act as grain boundaries in the samarium-cobalt magnet, hindering grain growth, refining the grains, and thereby improving the mechanical properties of the samarium-cobalt magnet. Simultaneously, grain refinement and increased grain boundary defects can increase resistivity. Furthermore, Sm₂O₃ itself has high resistivity; as the Sm₂O₃ content in the magnet increases, the resistivity of the samarium-cobalt magnet will also increase. Therefore, by using this base material and ultrafine powder in a certain doping manner, magnets with high resistivity and high strength and toughness can be prepared.

[0036] The present invention will be described below through specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods that do not specifically describe conditions or steps are conventional methods, and the reagents and materials used can be obtained commercially.

[0037] Example 1

[0038] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0039] Ultrafine magnetic powder A0, generated during the air jet milling process of samarium-cobalt alloy, was collected. The average particle size of the ultrafine magnetic powder A0 was 0.9 μm, and the oxygen content was 6500 ppm (e.g., ...). Figure 1 a and Figure 2 (as shown in a);

[0040] The ultrafine magnetic powder A0 was subjected to controlled oxidation (at a temperature of 26°C). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 17,500 ppm.

[0041] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium-cobalt alloy air jet milling process were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 contained an iron content of 22 wt% and an average particle size of approximately 11 μm (e.g., ...). Figure 1 b and Figure 2 As shown in b), the average particle size of qualified magnetic powder CO is approximately 3.6 μm;

[0042] The base material B0 was hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature was 100℃ and the hydrogen pressure was 0.1MPa. The hydrogen content of the hydrogenated magnetic powder B1 was 1600ppm.

[0043] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 6 μm.

[0044] Magnetic powder A1, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly. The mass ratio of magnetic powder A1 to magnetic powder B2 is 1:9, and the total mass ratio of magnetic powder A1 and magnetic powder B2 to qualified magnetic powder C0 is 5:5, resulting in mixed magnetic powder D with obvious differences in particle size.

[0045] The mixed magnetic powder D was oriented and shaped into a samarium cobalt green blank E, with a forming magnetic field strength of 1.5T and a pressure of 15MPa;

[0046] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1220℃, solution treatment at 1180℃, and aging heat treatment at 840℃.

[0047] Example 2

[0048] For the nominal component Sm(Co) 0.669 Fe 0.230 Cu 0.077 Zr 0.024 ) 7.6 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0049] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.6 μm and the oxygen content was 8000 ppm.

[0050] The ultrafine magnetic powder A0 was subjected to controlled oxidation (temperature 28℃). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 18,600 ppm.

[0051] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium cobalt alloy air jet milling process were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 27wt% and an average particle size of about 14μm, while the qualified magnetic powder C0 had an average particle size of about 3.7μm.

[0052] The base material B0 was hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature was 120°C and the hydrogen pressure was 0.15 MPa. The hydrogen content of the hydrogenated magnetic powder B1 was 1200 ppm.

[0053] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 7 μm.

[0054] Magnetic powder A1, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly. The mass ratio of magnetic powder A1 to magnetic powder B2 is 18:82. The total mass ratio of magnetic powder A1 and magnetic powder B2 to qualified magnetic powder C0 is 4:6. 0.2wt‰ of antioxidant butylated hydroxyanisole is added. After mixing evenly, mixed magnetic powder D with obvious differences in particle size is obtained.

[0055] The mixed magnetic powder D was oriented and molded to form a samarium cobalt green blank E, with a molding magnetic field strength of 1.5T and a pressure of 15MPa;

[0056] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1223℃, solution treatment at 1167℃, and aging heat treatment at 838℃.

[0057] Example 3

[0058] For the nominal component Sm(Co) 0.648 Fe 0.250 Cu 0.079 Zr 0.023 ) 7.8 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0059] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.3 μm and the oxygen content was 9500 ppm.

[0060] The ultrafine magnetic powder A0 was subjected to controlled oxidation (at a temperature of 27°C). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 22,000 ppm.

[0061] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium cobalt alloy air jet milling process were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 30 wt% and an average particle size of about 18 μm, while the qualified magnetic powder C0 had an average particle size of about 3.5 μm.

[0062] The base material B0 was hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature was 100℃ and the hydrogen pressure was 0.25MPa. The hydrogen content of the hydrogenated magnetic powder B1 was 1160ppm.

[0063] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 8 μm.

[0064] Magnetic powder A1, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly. The mass ratio of magnetic powder A1 to magnetic powder B2 is 29:71, and the total mass ratio of magnetic powder A1 and magnetic powder B2 to qualified magnetic powder C0 is 5:5, resulting in mixed magnetic powder D with obvious differences in particle size.

[0065] The mixed magnetic powder D is oriented to form a samarium cobalt green blank E, with a forming magnetic field strength of 1.5T and a pressure of 15MPa;

[0066] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1224℃, solution treatment at 1178℃, and aging heat treatment at 834℃.

[0067] Example 4

[0068] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.2 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0069] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.01 μm and the oxygen content was 10,000 ppm.

[0070] The ultrafine magnetic powder A0 was subjected to controlled oxidation (at a temperature of 25°C). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 35,000 ppm.

[0071] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium cobalt alloy air jet milling process were collected under a helium protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 18wt% and an average particle size of about 4μm, while the qualified magnetic powder C0 had an average particle size of about 2μm.

[0072] The base material B0 is hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature is 30°C and the hydrogen pressure is 1 MPa. The hydrogen content of the hydrogenated magnetic powder B1 is 1000 ppm.

[0073] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 3 μm.

[0074] Magnetic powder A1, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly. The mass ratio of magnetic powder A1 to magnetic powder B2 is 2:8, and the total mass ratio of magnetic powder A1 and magnetic powder B2 to qualified magnetic powder C0 is 1:5, resulting in mixed magnetic powder D with obvious differences in particle size.

[0075] The mixed magnetic powder D was oriented and shaped into a samarium cobalt green blank E, with a forming magnetic field strength of 1.5T and a pressure of 15MPa;

[0076] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1250℃, solution treatment at 1190℃, and aging heat treatment at 860℃.

[0077] Example 5

[0078] For the nominal component Sm(Co) 0.606 Fe 0.290 Cu 0.078 Zr 0.026 ) 7.9 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0079] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 2 μm and the oxygen content was 4000 ppm.

[0080] The ultrafine magnetic powder A0 was subjected to controlled oxidation (at a temperature of 30°C). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 15,000 ppm.

[0081] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium cobalt alloy air jet milling process were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 30wt% and an average particle size of about 20μm, while the qualified magnetic powder C0 had an average particle size of about 4μm.

[0082] The base material B0 is hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature is 300℃ and the hydrogen pressure is 3MPa. The hydrogen content of the hydrogenated magnetic powder B1 is 2000ppm.

[0083] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 10 μm.

[0084] Magnetic powder A1, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly. The mass ratio of magnetic powder A1 to magnetic powder B2 is 3:7, and the total mass ratio of magnetic powder A1 and magnetic powder B2 to qualified magnetic powder C0 is 1:9, resulting in mixed magnetic powder D with obvious differences in particle size.

[0085] The mixed magnetic powder D is oriented to form a samarium cobalt green blank E, with a forming magnetic field strength of 1.5T and a pressure of 15MPa;

[0086] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1200℃, solution treatment at 1120℃, and aging heat treatment at 800℃.

[0087] Comparative Example 1

[0088] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0089] The qualified magnetic powder CO produced during the above-mentioned samarium cobalt alloy air jet milling process was collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The average particle size of the qualified magnetic powder CO was approximately 3.6 μm.

[0090] The qualified magnetic powder C0 orientation molding is used to form a green body E, with a molding magnetic field strength of 1.5T and a pressure of 15MPa;

[0091] Sintered samarium cobalt permanent magnets were prepared by sintering the aforementioned samarium cobalt green blank E at 1220℃, solution treatment at 1180℃, and aging heat treatment at 840℃.

[0092] Comparative Example 2 (Compared to Example 1, this comparative example only recovers ultrafine magnetic powder)

[0093] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0094] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.9 μm and the oxygen content was 6500 ppm.

[0095] The ultrafine magnetic powder A0 was subjected to controlled oxidation (temperature 26℃). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 17,500 ppm.

[0096] The qualified magnetic powder CO produced during the above-mentioned samarium cobalt alloy air jet milling process was collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The average particle size of the qualified magnetic powder CO was approximately 3.6 μm.

[0097] Magnetic powder A1 and qualified magnetic powder C0 are mixed evenly at a mass ratio of 1:1 to obtain mixed magnetic powder D;

[0098] The mixed magnetic powder D was oriented and molded to form a samarium cobalt green blank E, with a molding magnetic field strength of 1.5T and a pressure of 15MPa;

[0099] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1232℃, solution treatment at 1180℃, and aging heat treatment at 840℃.

[0100] Comparative Example 3 (Compared to Example 1, this comparative example only recovers the bottom material)

[0101] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0102] The bottom material B0 and qualified magnetic powder C0 generated during the air jet milling of samarium cobalt alloy were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 22wt% and an average particle size of about 11μm, while the qualified magnetic powder C0 had an average particle size of about 3.6μm.

[0103] The base material B0 was hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature was 100℃, the hydrogen pressure was 0.1MPa, and the hydrogen content of the powder was 1600ppm.

[0104] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 6 μm.

[0105] Magnetic powder B2 and qualified magnetic powder C0 are mixed evenly at a mass ratio of 1:1 to obtain mixed magnetic powder D;

[0106] The mixed magnetic powder D was oriented and molded to form a samarium cobalt green blank E, with a molding magnetic field strength of 1.5T and a pressure of 15MPa;

[0107] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1216℃, solution treatment at 1180℃, and aging heat treatment at 840℃.

[0108] Comparative Example 4 (The ultrafine magnetic powder was not subjected to controlled oxidation compared to Example 1)

[0109] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0110] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.9 μm and the oxygen content was 6500 ppm.

[0111] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium cobalt alloy air jet milling process were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 22wt% and an average particle size of about 11μm, while the qualified magnetic powder C0 had an average particle size of about 3.6μm.

[0112] The base material B0 was hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature was 100℃, the hydrogen pressure was 0.1MPa, and the hydrogen content of the powder was 1600ppm.

[0113] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 6 μm.

[0114] Ultrafine magnetic powder A0, magnetic powder B2 and qualified magnetic powder C0 are mixed evenly. The mass ratio of ultrafine magnetic powder A0 and magnetic powder B2 is 1:9, and the mass ratio of the total mass of ultrafine magnetic powder A0 and magnetic powder B2 to the mass of qualified magnetic powder C0 is 5:5, resulting in mixed magnetic powder D with obvious differences in particle size.

[0115] The mixed magnetic powder D was oriented and molded to form a samarium cobalt green blank E, with a molding magnetic field strength of 1.5T and a pressure of 15MPa;

[0116] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1219℃, solution treatment at 1180℃, and aging heat treatment at 840℃.

[0117] Comparative Example 5 (The substrate was not hydrogenated or subjected to air jet milling compared to Example 1)

[0118] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0119] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.9 μm and the oxygen content was 6500 ppm.

[0120] The ultrafine magnetic powder A0 was subjected to controlled oxidation (temperature 26℃). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 17,500 ppm.

[0121] The bottom material B0 and qualified magnetic powder C0 generated during the above-mentioned samarium cobalt alloy air jet milling process were collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 had an iron content of 22wt% and an average particle size of about 11μm, while the qualified magnetic powder C0 had an average particle size of about 3.6μm.

[0122] Mix magnetic powder A1, base material B0 and qualified magnetic powder C0 evenly. The mass ratio of magnetic powder A1 to base material B0 is 1:9, and the mass ratio of the total mass of magnetic powder A1 and base material B0 to the mass of qualified magnetic powder C0 is 1:1, to obtain mixed magnetic powder D with obvious differences in particle size.

[0123] The mixed magnetic powder D was oriented and molded to form a samarium cobalt green blank E, with a molding magnetic field strength of 1.5T and a pressure of 15MPa;

[0124] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1219℃, solution treatment at 1180℃, and aging heat treatment at 840℃.

[0125] Comparative Example 6 (no qualified magnetic powder added compared to Example 1)

[0126] For the nominal component Sm(Co) 0.680 Fe 0.220 Cu 0.075 Zr 0.025 ) 7.5 The samarium-cobalt alloy was subjected to air jet milling powder processing;

[0127] Ultrafine magnetic powder A0 generated during the air jet milling process of samarium cobalt alloy was collected. The average particle size of ultrafine magnetic powder A0 was 0.9 μm and the oxygen content was 6500 ppm.

[0128] The ultrafine magnetic powder A0 was subjected to controlled oxidation (at a temperature of 26°C). After every 10 minutes of oxidation, the oxidation was stopped and the oxygen content was tested to obtain magnetic powder A1, which had an oxygen content of approximately 17,500 ppm.

[0129] The bottom material B0 generated during the above-mentioned samarium cobalt alloy air jet milling process was collected under a nitrogen protective atmosphere and at a temperature not exceeding 30°C. The bottom material B0 contained an iron content of 22 wt% and an average particle size of approximately 11 μm.

[0130] The base material B0 was hydrogenated to obtain hydrogenated magnetic powder B1. The hydrogenation temperature was 100℃ and the hydrogen pressure was 0.1MPa. The hydrogen content of the hydrogenated magnetic powder B1 was 1600ppm.

[0131] Hydrogenated magnetic powder B1 was subjected to air jet milling to obtain magnetic powder B2 with an average particle size of approximately 6 μm.

[0132] Magnetic powder A1 and magnetic powder B2 were mixed evenly at a mass ratio of 1:9 to obtain mixed magnetic powder D with obvious differences in particle size;

[0133] The mixed magnetic powder D was oriented and shaped into a samarium cobalt green blank E, with a forming magnetic field strength of 1.5T and a pressure of 15MPa;

[0134] Sintered samarium cobalt permanent magnets were prepared by sequentially subjecting samarium cobalt green blank E to sintering at 1250℃, solution treatment at 1180℃, and aging heat treatment at 850℃.

[0135] The sintered samarium cobalt permanent magnets in Examples 1-5 and Comparative Examples 1-6 were subjected to relevant performance tests, and the results are shown in Table 1.

[0136] Table 1 Performance test results of sintered samarium cobalt permanent magnets

[0137]

[0138] Note: The remanence and maximum magnetic energy product in Table 1 were tested according to GB / T 3217, Test Method for Magnetic Properties of Permanent Magnet (Hard Magnet) Materials; the bending strength was tested according to GB / T 31967.2, Test Method for Physical Properties of Rare Earth Permanent Magnet Materials Part 2: Determination of Bending Strength and Fracture Toughness; and the resistivity was tested according to GB / T 315-2019, Test Method for Resistivity of Metallic Materials.

[0139] As can be seen from the test results in Table 1, the preparation method of this invention can not only effectively improve resource utilization and reduce costs and energy consumption, but also produce sintered samarium cobalt permanent magnets with excellent resistivity and bending strength while ensuring magnetic properties, thus meeting the application requirements of samarium cobalt permanent magnets in small, high-precision instruments.

[0140] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0141] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method of producing a high mechanical strength sintered samarium-cobalt permanent magnet having a high electrical resistivity, characterized by, The method comprises the following steps: providing a samarium-cobalt alloy; airflow milling the samarium-cobalt alloy and collecting superfine magnetic powder A0, base material B0 and qualified magnetic powder C0 generated in the airflow milling process respectively; controllably oxidizing the superfine magnetic powder A0 to obtain magnetic powder A1; hydrogenating the base material B0 to obtain hydrogenated magnetic powder B1, and then airflow milling the hydrogenated magnetic powder B1 to obtain magnetic powder B2; mixing the magnetic powder A1, the magnetic powder B2 and the qualified magnetic powder C0 uniformly to obtain mixed magnetic powder D; obtaining a sintered samarium-cobalt permanent magnet by orienting and forming the mixed magnetic powder D to obtain samarium-cobalt green body E and then processing the samarium-cobalt green body E.

2. The production method according to claim 1, wherein The composition of the Sm-Co alloy is Sm(Co 1-a-b-c Fe a Cu b Zr c ) z wherein 8.1≥z≥7.2, 0.2≥a≥0.4, 0.09≥b≥0.05, 0.01≥c≥0.

04.

3. The production method according to claim 1, wherein The superfine magnetic powder A0 has a particle size of 0.01-2 μm and an oxygen content of 4000-10000 ppm. The base material B0 has an iron content of 18%-30 wt% and a particle size of 4-20 μm. The qualified magnetic powder C0 has a particle size of 2-4 μm.

4. The production method according to claim 1, wherein The collection of the base material B0 and the qualified magnetic powder C0 is performed in a protective gas atmosphere with an oxygen content of less than 150 ppm and under temperature control.

5. The production method according to claim 4, wherein The protective gas is at least one selected from nitrogen and rare gas.

6. The production method according to claim 4, wherein The temperature control condition is that the temperature of the powder and the surrounding atmosphere is not higher than 30℃.

7. The production method according to claim 1, wherein The controllable oxidation is achieved by controlling the time and temperature of the superfine magnetic powder A0 contacting air.

8. The production method according to claim 7, wherein The controllable oxidation is performed at a temperature of 26-30℃.

9. The production method according to claim 7, wherein The controllable oxidation process is that the superfine magnetic powder A0 is oxidized for 10 min, the oxidation is stopped and the oxygen content is tested, and the process is repeated until the oxygen content reaches a target range of 15000-35000 ppm.

10. The production method according to claim 1, wherein The hydrogenation treatment is performed at a temperature of 30-300℃ and a hydrogen pressure of 0.1-3 MPa, and the hydrogen content of the hydrogenated magnetic powder B1 is 1000-2000 ppm.

11. The production method according to claim 1, wherein The magnetic powder B2 has a particle size of 3-10 μm.

12. The production method according to claim 1, wherein In the mixed magnetic powder D, the mass ratio of the magnetic powder A1 to the magnetic powder B2 is 1:9-3:7, and the mass ratio of the total mass of the magnetic powder A1 and the magnetic powder B2 to the qualified magnetic powder C0 is 1:9-1:

1.

13. The production method according to claim 1, wherein 0.1 wt‰-0.5 wt‰ of an antioxidant is added to the mixed magnetic powder D.

14. The production method according to claim 13, wherein The antioxidant is at least one selected from butylated hydroxyanisole, butylated hydroxytoluene and tertiary butyl hydroquinone.

15. The production method according to claim 1, wherein The step of processing the samarium-cobalt green body E into a sintered samarium-cobalt permanent magnet further comprises sintering, solid solution and aging treatment.

16. The production method according to claim 15, wherein The sintering temperature is 1200-1250℃; and / or, the solid solution temperature is 1120-1190℃; and / or, the aging treatment temperature is 800-860℃.

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