A rare-earth permanent magnet material Sm2(Co,Fe,Cu,Zr) 17 and its preparation method

Abstract

This invention relates to a rare-earth permanent magnet material Sm2(Co,Fe,Cu,Zr). 17 The method for preparing the permanent magnet material, wherein the chemical formula of the permanent magnet material is Sm2Co. 17‑a‑b‑c Fe a Cu b Zr c Where 0.15≤a≤0.35, 0.05≤b≤0.15, 0.02≤c≤0.05, and a+b+c≤0.50; the permanent magnet material has a 2:17 rhombohedral crystal structure with space group R-3m and an average grain size of 3-8μm; the preparation method includes vacuum melting, homogenization treatment, powder preparation, magnetic field orientation forming, cold isostatic pressing, sintering, and graded aging treatment steps. This invention improves the coercivity and maximum energy product of the permanent magnet material and enhances its temperature stability by optimizing the Fe, Cu, and Zr element ratio and introducing a multi-stage heat treatment process.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet materials technology, and particularly to a rare earth permanent magnet material Sm2 (Co,Fe,Cu,Zr). 17 And its preparation method. Background Technology

[0002] Rare earth permanent magnet materials are important functional materials used in modern applications, including motors, generators, magnetic levitation systems, medical devices, and aerospace. Sm-Co based permanent magnet materials hold a significant position in high-temperature applications due to their excellent temperature stability and corrosion resistance. The second-generation rare earth permanent magnet material, Sm2Co... 17 Type-3 permanent magnets have a high Curie temperature (approximately 920°C), a low temperature coefficient, and good oxidation resistance, making them the main permanent magnet materials currently used for operating temperatures exceeding 300°C.

[0003] To further improve Sm2Co 17 To improve the magnetic properties of permanent magnets, the industry typically uses Fe to partially replace Co to increase saturation magnetization, Cu to promote the formation of a 1:5 cell wall phase, and Zr to refine grains and optimize cellular morphology. However, existing technologies lack systematic optimization of the amount and ratio of Fe, Cu, and Zr, and the control of process parameters is not precise enough, resulting in poor consistency and repeatability of magnetic properties, and the temperature stability needs to be improved.

[0004] Therefore, there is an urgent need to develop a rare earth permanent magnet material with optimized element ratios and controllable preparation process, as well as its preparation method. Summary of the Invention

[0005] To address the above problems, this invention provides a rare-earth permanent magnet material Sm2(Co,Fe,Cu,Zr). 17 And its preparation method.

[0006] The specific technical solution is as follows: A rare earth permanent magnet material with the chemical formula Sm2Co 17-a-b-c Fe a Cu b Zr c Where a, b, and c represent the atomic substitution fractions of Fe, Cu, and Zr, respectively, with 0.15≤a≤0.35, 0.05≤b≤0.15, 0.02≤c≤0.05, and a+b+c≤0.50; the permanent magnet material has a 2:17 rhombohedral crystal structure with space group R-3m; the average grain size of the permanent magnet material is 3-8μm.

[0007] Furthermore, the permanent magnet material has a cellular microstructure, including a 2:17 type rhombohedral intracellular phase and a 1:5 type hexagonal cell wall phase, with an average size of 80-150 nm for the intracellular phase and an average thickness of 5-10 nm for the cell wall phase.

[0008] Furthermore, the permanent magnet material has an intrinsic coercivity Hcj≥25kOe, remanence Br≥11.0kGs, maximum energy product (BH)max≥28MGOe, and squareness Hk / Hcj≥0.90 at 25℃.

[0009] Furthermore, the density of the permanent magnet material is ≥8.30g / cm³, and the oxygen content is ≤500ppm.

[0010] Furthermore, the intrinsic coercivity Hcj of the permanent magnet material at 300℃ is ≥18kOe, and the temperature coefficient of coercivity β(Hcj) is -0.10% / ℃ to -0.20% / ℃.

[0011] A method for preparing the above-mentioned rare earth permanent magnet material includes the following steps: (1) Weigh the raw material metals according to the stoichiometric ratio, under a vacuum degree ≤10 - The alloy ingot is smelted in an induction melting furnace with a melting temperature of 1450-1550℃ and held for 10-20 minutes before being poured into an alloy ingot. (2) The alloy ingot is homogenized at 1100-1200℃ for 12-24h, then crushed and powdered to obtain alloy powder with an average particle size of 3-5μm. (3) The alloy powder is pressed into shape in an orientation magnetic field with a magnetic field strength of 1.5-2.5T and a pressing pressure of 150-250MPa to obtain a pressed blank; (4) The compact is subjected to cold isostatic pressing treatment at a pressure of 200-300MPa and a holding time of 60-120s; (5) The cold isostatically pressed blank is sintered at 1190-1210℃ for 30-60 min; (6) The sintered body is subjected to graded aging treatment: the first aging temperature is 850-900℃ and the aging time is 1-2h; the second aging temperature is 750-800℃ and the aging time is 2-4h; the third aging temperature is 400-500℃ and the aging time is 3-6h; the temperature is cooled to the next temperature at a rate of 5-10℃ / min between each aging stage.

[0012] Furthermore, the purity of the raw material metal in step (1) is ≥99.9%, and the Sm content is 5-10% in excess of the stoichiometric ratio on an atomic percentage basis.

[0013] Furthermore, in step (2), the powdering process adopts a combination of hydrogen crushing and air jet milling. The hydrogen crushing is carried out at room temperature, the hydrogen absorption time is 2-4 hours, and the dehydrogenation temperature is 600-750℃.

[0014] Furthermore, in step (3), the pressing process is carried out by compression molding or static molding with rubber, and the orientation magnetic field direction is parallel to the pressing direction.

[0015] Furthermore, the graded aging treatment in step (6) is carried out under argon protection. After the first stage of aging, the furnace is cooled to the second stage temperature. After the second stage of aging, the furnace is cooled to the third stage temperature. After the third stage of aging, the furnace is cooled to room temperature.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Synergistic optimization of composition, structure, and organization This invention achieves synergistic optimization of composition, crystal structure, and microstructure by systematically optimizing the addition amounts of Fe, Cu, and Zr (a=0.15-0.35, b=0.05-0.15, c=0.02-0.05, a+b+c≤0.50), combined with a 2:17 rhombohedral crystal structure (space group R-3m) and an average grain size of 3-8 μm. Fe substitution increases saturation magnetization, Cu promotes the formation of a 1:5 cell wall phase, and Zr refines grains and stabilizes the high-temperature microstructure. The synergistic effect of these three elements enables the material to achieve an optimal balance between magnetic properties, coercivity, and temperature stability.

[0017] 2. Precise and controllable microstructure This invention precisely controls the formation process of cellular structures through optimized graded aging treatment (three-stage temperature gradient: 850-900℃ → 750-800℃ → 400-500℃), maintaining the intracellular phase size at 80-150 nm and the cell wall phase thickness at 5-10 nm, thus forming an ideal magnetic domain pinning structure. This nanoscale structure matches the 3-8 μm grain size, ensuring that the material simultaneously possesses high coercivity and high remanence.

[0018] 3. Significantly improved magnetic properties The permanent magnet material of this invention has an intrinsic coercivity Hcj≥25kOe, remanence Br≥11.0kGs, maximum energy product (BH)max≥28MGOe, and squareness Hk / Hcj≥0.90 at 25℃, which is 10-15% higher than the prior art and meets the application requirements of high-performance permanent magnet devices.

[0019] 4. The preparation process is stable and controllable. This invention employs a powder-making process combining hydrogen crushing and air jet milling to obtain alloy powder with narrow particle size distribution and low oxygen content (≤500ppm). Through optimized sintering temperature (1190-1210℃) and graded aging process, the product density is ensured to be ≥8.30g / cm³, and the performance fluctuation between batches is less than 5%.

[0020] 5. Improved temperature stability This invention improves the high-temperature magnetic stability of materials through Zr microalloying and optimized aging processes. At 300℃, the intrinsic coercivity Hcj ≥ 18kOe, and the coercivity temperature coefficient β(Hcj) is controlled within the range of -0.10% / ℃ to -0.20% / ℃, which is about 30% lower than that of materials without Zr, thus broadening the high-temperature application range of the materials. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0022] The following embodiments, in conjunction with the accompanying drawings, are merely for illustrating the technical solutions described in the claims and are not intended to limit the scope of protection of the claims.

[0023] Example 1 A rare earth permanent magnet material with the chemical formula Sm2Co 17-a-b-c Fe a Cu b Zr c Where 0.15≤a≤0.35, 0.05≤b≤0.15, 0.02≤c≤0.05, and a+b+c≤0.50; the permanent magnet material has a 2:17 rhombohedral crystal structure with space group R-3m; the average grain size of the permanent magnet material is 3-8μm.

[0024] The permanent magnet material has a cellular microstructure, including a 2:17 rhombohedral intracellular phase and a 1:5 hexagonal cell wall phase. The average size of the intracellular phase is 80-150 nm, and the average thickness of the cell wall phase is 5-10 nm.

[0025] The permanent magnet material has an intrinsic coercivity Hcj≥25kOe, remanence Br≥11.0kGs, maximum energy product (BH)max≥28MGOe, and squareness Hk / Hcj≥0.90 at 25℃.

[0026] The permanent magnet material has a density ≥8.30g / cm³ and an oxygen content ≤500ppm.

[0027] The permanent magnet material has an intrinsic coercivity Hcj ≥ 18kOe at 300℃, and a coercivity temperature coefficient β(Hcj) of -0.10% / ℃ to -0.20% / ℃.

[0028] Example 2 A method for preparing a rare earth permanent magnet material includes the following steps: Step 1: Vacuum melting Weigh out raw material metals Sm, Co, Fe, Cu, and Zr with a purity ≥99.9% according to stoichiometry. The Sm content, calculated as an atomic percentage, should be 5-10% in excess of the stoichiometric ratio to compensate for Sm volatilization loss during smelting and subsequent heat treatment. Place the raw material into an alumina crucible, put it in a vacuum induction melting furnace, and evacuate to ≤10°C. - ²Pa, electrically heated to 1450-1550℃, held for 10-20 minutes to fully melt and homogenize the alloy, and then poured into a water-cooled copper mold to obtain an alloy ingot.

[0029] Step 2: Homogenization and Powdering The alloy ingot is homogenized at 1100-1200℃ for 12-24 hours to eliminate casting segregation and ensure uniform distribution of alloying elements. After homogenization, the ingot is mechanically crushed and then pulverized using a combination of hydrogen crushing and air jet milling. Hydrogen crushing is performed at room temperature for 2-4 hours, causing the ingot to break due to hydrogen embrittlement. Dehydrogenation is then carried out at 600-750℃ to obtain hydrogen-crushed powder. This powder is further pulverized in a nitrogen-protected air jet mill, with controlled classifier speed and air pressure, to obtain fine powder with an average particle size of 3-5 μm.

[0030] Step 3: Magnetic field orientation shaping Fine powder is loaded into a mold and pressed into shape under an orientation magnetic field with a strength of 1.5-2.5T and a pressing pressure of 150-250MPa. The orientation magnetic field direction is parallel to the pressing direction. Compression molding or isostatic molding with rubber can be used to obtain the pressed blank.

[0031] Step 4: Cold isostatic pressing The compact is subjected to cold isostatic pressing at a pressure of 200-300 MPa for a holding time of 60-120 seconds. Cold isostatic pressing further increases the density of the compact, bringing it to 60-65% of the theoretical density, and eliminates cracks and delamination defects that may occur during the pressing process.

[0032] Step 5: Sintering The cold isostatically pressed compact is placed in a vacuum sintering furnace and sintered at 1190-1210℃ for 30-60 minutes. This temperature range is lower than that of Sm2Co. 17The phase decomposition temperature (approximately 1230℃) ensures sufficient atomic diffusion and densification, resulting in a density of over 98% of the theoretical density after sintering, with the oxygen content controlled below 500 ppm.

[0033] Step 6: Tiered Time-Limited Processing The sintered body undergoes a three-stage aging treatment to form an optimized cellular microstructure. First-stage aging: Aging at 850-900℃ for 1-2 hours to allow alloying elements to fully diffuse and form a preliminary phase separation trend; Second-stage aging: furnace cooling to 750-800℃ at a rate of 5-10℃ / min for 2-4 hours to promote the nucleation of the 1:5 cell wall phase; Third-stage aging: furnace cooling to 400-500℃ at a rate of 5-10℃ / min, aging for 3-6 hours, to allow Cu elements to fully segregate to the cell wall phase and form effective domain wall pinning centers.

[0034] All aging stages were carried out under argon protection. The empirical relationship between the third-stage aging temperature T and the aging time t is as follows: when t = 5-6 h, T = 400-450 °C; when t = 3-4 h, T = 450-500 °C. This relationship is based on Cu in Sm2Co. 17 The relationship between the diffusion coefficient in the matrix and temperature is determined to ensure optimal aging results at the target temperature.

[0035] After the third stage of aging is completed, air cool to room temperature.

[0036] Example 3 Preparation of chemical formula Sm2Co 16.65 Fe 0.25 Cu 0.08 Zr 0.02 The permanent magnet material (a=0.25, b=0.08, c=0.02, a+b+c=0.35).

[0037] Raw materials were weighed according to stoichiometric ratio, with an excess of 7 at.%. Vacuum melting temperature was 1500℃, held for 15 min. Homogenization treatment temperature was 1150℃, time was 18 h. Hydrogen crushing and hydrogen absorption was performed for 3 h, and dehydrogenation temperature was 650℃. The average particle size of the powder after air jet milling was 4 μm. The orientation magnetic field strength was 2.0 T, and the pressing pressure was 200 MPa. Cold isostatic pressing pressure was 250 MPa, held for 90 s. Sintering temperature was 1200℃, time was 45 min. Staged aging: first stage 880℃ / 1.5 h, second stage 780℃ / 3 h, third stage 450℃ / 5 h, cooling rate was 6℃ / min.

[0038] Measured material parameters: average grain size 5.2 μm, density 8.35 g / cm³, oxygen content 420 ppm. Magnetic properties: at 25℃, intrinsic coercivity Hcj = 26.5 kOe, remanence Br = 11.2 kGs, maximum energy product (BH)max = 29.7 MGOe, squareness Hk / Hcj = 0.92; at 300℃, Hcj = 20.8 kOe, coercivity temperature coefficient β(Hcj) = -0.14% / ℃.

[0039] Example 4 Preparation of chemical formula Sm2Co 16 . 55 Fe0. 35 Cu0. 05 Zr0. 05 The permanent magnet material (a=0.35, b=0.05, c=0.05, a+b+c=0.45).

[0040] Raw materials were weighed according to stoichiometric ratio, with an excess of 8 at.%. Vacuum melting temperature was 1520℃, held for 12 min. Homogenization treatment temperature was 1180℃, time was 20 h. Hydrogen decomposition and hydrogen absorption were performed for 2.5 h, and the dehydrogenation temperature was 680℃. The average particle size of the powder after air jet milling was 3.5 μm. The orientation magnetic field strength was 2.2 T, and the pressing pressure was 220 MPa. Cold isostatic pressing pressure was 280 MPa, held for 100 s. Sintering temperature was 1205℃, time was 40 min. Staged aging: first stage 890℃ / 1 h, second stage 790℃ / 2.5 h, third stage 480℃ / 4 h, cooling rate was 8℃ / min.

[0041] Measured material parameters: average grain size 4.5 μm, density 8.38 g / cm³, oxygen content 380 ppm. Magnetic properties: at 25℃, Hcj = 28.2 kOe, Br = 11.0 kGs, (BH)max = 29.5 MGOe, Hk / Hcj = 0.91; at 300℃, Hcj = 21.5 kOe, β(Hcj) = -0.12% / ℃.

[0042] Example 5 Preparation of chemical formula Sm2Co 16 . 75 Fe0. 15 Cu0. 07 Zr0. 03 The permanent magnet material (a=0.15, b=0.07, c=0.03, a+b+c=0.25).

[0043] Raw materials were weighed according to stoichiometric ratio, with an excess of 6 at.%. Vacuum melting temperature was 1480℃, held for 18 min. Homogenization treatment temperature was 1120℃, time was 22 h. Hydrogen decomposition and hydrogen absorption were performed for 4 h, and the dehydrogenation temperature was 620℃. The average particle size of the powder after air jet milling was 4.5 μm. The orientation magnetic field strength was 1.8 T, and the pressing pressure was 180 MPa. Cold isostatic pressing pressure was 220 MPa, held for 110 s. Sintering temperature was 1190℃, time was 50 min. Staged aging: first stage 860℃ / 2 h, second stage 760℃ / 4 h, third stage 420℃ / 6 h, cooling rate was 5℃ / min.

[0044] Measured material parameters: average grain size 6.8 μm, density 8.32 g / cm³, oxygen content 450 ppm. Magnetic properties: at 25℃, Hcj = 25.8 kOe, Br = 11.5 kGs, (BH)max = 28.6 MGOe, Hk / Hcj = 0.93; at 300℃, Hcj = 19.8 kOe, β(Hcj) = -0.16% / ℃.

[0045] Comparative Example 1 (Traditional Ingredients) Preparation of chemical formula Sm2Co 16.75 Fe0. 25 The permanent magnet material contains no Cu or Zr (a=0.25, b=0, c=0).

[0046] The same preparation process as in Example 3 was used. Magnetic properties were measured: at 25°C, Hcj = 18.5 kOe, (BH)max = 24.3 MGOe, no obvious cellular structure, and poor squareness.

[0047] Comparative Example 2 (Traditional Preparation Process) The same components as in Example 3 were used, but the ingot crushing-ball milling process was adopted, and a single-stage aging treatment (850℃ / 4h) was performed after sintering.

[0048] The measured magnetic properties are: at 25℃, Hcj=21.3kOe, (BH)max=26.1MGOe; the average grain size is non-uniform (2-12μm), the density is only 94% of the theoretical density, and there are obvious pores.

[0049] Compared with the prior art, the present invention significantly improves coercivity, maximum magnetic energy product and microstructure uniformity.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A rare-earth permanent magnet material, characterized in that, The chemical formula is Sm2Co 17-a-b-c Fe a Cu b Zr c Where a, b, and c represent the atomic substitution fractions of Fe, Cu, and Zr, respectively, with 0.15≤a≤0.35, 0.05≤b≤0.15, 0.02≤c≤0.05, and a+b+c≤0.50; the permanent magnet material has a 2:17 rhombohedral crystal structure with space group R-3m; the average grain size of the permanent magnet material is 3-8μm.

2. The rare earth permanent magnet material as described in claim 1, characterized in that, The permanent magnet material has a cellular microstructure, including a 2:17 rhombohedral intracellular phase and a 1:5 hexagonal cell wall phase. The average size of the intracellular phase is 80-150 nm, and the average thickness of the cell wall phase is 5-10 nm.

3. The rare earth permanent magnet material as described in claim 1, characterized in that, The permanent magnet material has an intrinsic coercivity Hcj≥25kOe, remanence Br≥11.0kGs, maximum energy product (BH)max≥28MGOe, and squareness Hk / Hcj≥0.90 at 25℃.

4. The rare earth permanent magnet material as described in claim 1, characterized in that, The density of the permanent magnet material is ≥8.30g / cm³, and the oxygen content is ≤500ppm.

5. The rare earth permanent magnet material as described in claim 1, characterized in that, The intrinsic coercivity Hcj of the permanent magnet material at 300℃ is ≥18kOe, and the temperature coefficient of coercivity β(Hcj) is -0.10% / ℃ to -0.20% / ℃.

6. A method for preparing the rare earth permanent magnet material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Weigh the raw material metals according to the stoichiometric ratio, under a vacuum degree ≤10 - The alloy ingot is smelted in an induction melting furnace with a melting temperature of 1450-1550℃ and held for 10-20 minutes before being poured into an alloy ingot. (2) The alloy ingot is homogenized at 1100-1200℃ for 12-24h, then crushed and powdered to obtain alloy powder with an average particle size of 3-5μm. (3) The alloy powder is pressed into shape in an orientation magnetic field with a magnetic field strength of 1.5-2.5T and a pressing pressure of 150-250MPa to obtain a pressed blank; (4) The compact is subjected to cold isostatic pressing treatment at a pressure of 200-300MPa and a holding time of 60-120s; (5) The cold isostatically pressed blank is sintered at 1190-1210℃ for 30-60 min; (6) The sintered body is subjected to graded aging treatment: the first aging temperature is 850-900℃ and the aging time is 1-2h; the second aging temperature is 750-800℃ and the aging time is 2-4h; the third aging temperature is 400-500℃ and the aging time is 3-6h; the temperature is cooled to the next temperature at a rate of 5-10℃ / min between each aging stage.

7. The preparation method according to claim 6, characterized in that, The purity of the raw material metal in step (1) is ≥99.9%, and the Sm content is 5-10% excess according to the stoichiometric ratio on an atomic percentage basis.

8. The preparation method according to claim 6, characterized in that, The powdering process in step (2) adopts a combination of hydrogen crushing and air jet milling. The hydrogen crushing is carried out at room temperature, the hydrogen absorption time is 2-4 hours, and the dehydrogenation temperature is 600-750℃.

9. The preparation method according to claim 6, characterized in that, The pressing and molding in step (3) adopts compression molding or rubber isostatic molding, and the orientation magnetic field direction is parallel to the pressing direction.

10. The preparation method according to claim 6, characterized in that, The graded aging process in step (6) is carried out under argon protection. After the first stage of aging, the furnace is cooled to the second stage temperature. After the second stage of aging, the furnace is cooled to the third stage temperature. After the third stage of aging, the furnace is cooled to room temperature.

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