High-iron-content samarium-cobalt magnet and preparation method thereof

Abstract

The invention belongs to the technical field of magnetic materials, and particularly relates to a high-iron-content samarium-cobalt magnet and a preparation method thereof. The preparation method comprises the steps that firstly, high-iron-content samarium-cobalt main phase magnetic powder and copper-rich auxiliary alloy powder are mixed according to a certain proportion through a double-alloy technology, a proper amount of copper powder is added into the mixed magnetic powder, and then magnetic field forming, cold isostatic pressing and sintering are sequentially carried out; then adopting a two-stage solid solution process to obtain a solid solution precursor with large-size grains; and finally, a three-stage aging process is adopted, the obtained cellular structure is complete and uniform, and the copper element is distributed in a concentrated mode at the cell wall. The prepared samarium-cobalt magnet has high coercive force and high squareness, the operation is simple and easy to implement, and batch production is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic materials, and in particular relates to a high-iron-content samarium-cobalt magnet and a preparation method thereof. Background Art

[0002] 2∶17 samarium cobalt (SmCo) magnets are the permanent magnet materials with the best magnetic properties above 250℃. They have good corrosion resistance and oxidation resistance, and play an irreplaceable role in high-precision and cutting-edge technology fields such as aerospace engines, magnetic bearings, and microwave communications. The rapid development of emerging technology fields such as new energy vehicles and rail transportation has put forward higher requirements on the temperature resistance and maximum magnetic energy product of permanent magnet materials. Based on the high Curie temperature advantage of 2∶17 SmCo permanent magnet materials, appropriately increasing the content of iron in the magnet is an effective way to develop high-temperature resistant and high-magnetic energy product magnets. Studies have shown that increasing the amount of iron replacing cobalt in 2∶17 SmCo magnets can directly increase the remanence of the magnet, thereby obtaining a higher theoretical magnetic energy product. However, when the iron content exceeds 20% (mass fraction), the squareness and coercive force of the magnet deteriorate sharply, restricting the development of the maximum magnetic energy product, which is mainly attributed to the increase in structural defects in high-iron content magnets. Therefore, how to break through the technical barriers of high magnetic energy product 2:17 type SmCo magnets is a key issue that needs to be studied at present. Summary of the invention

[0003] The object of the present invention is to provide a high iron content samarium cobalt magnet and a preparation method thereof, aiming to solve the problem that defect structures are easily generated at the grain boundaries of the high iron content samarium cobalt magnet and incomplete cellular structures are easily generated in the crystals, and to prepare a high iron content samarium cobalt magnet with high coercivity, high squareness and high magnetic energy product.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a high iron content samarium cobalt magnet, which comprises: a high iron content samarium cobalt alloy, a copper-rich auxiliary alloy and copper powder, wherein the mass ratio of the high iron content samarium cobalt alloy to the copper-rich auxiliary alloy is 5:1 to 20:1; the copper powder accounts for 1 to 5wt.% of the sum of the mass of the high iron content samarium cobalt alloy and the copper-rich auxiliary alloy.

[0005] Furthermore, the chemical formula of the high iron content samarium-cobalt alloy component is Sm(Co 1-a-b-c Fe a Cu b Zr c ) z , where 0.16≤a≤0.4, 0.04≤b≤0.1, 0.018≤c≤0.033, 7≤z≤8; the copper-rich auxiliary alloy composition is RE(Co 1-u Cu u )5, wherein RE is one or more of Pr, Nd, Sm, 0.4≤u≤1.

[0006] Furthermore, the cell structure in the final magnet crystal of the high iron content samarium cobalt magnet is complete and uniform, with a cell size of 100-150 nm; and the copper-rich 1:5H phase is generated in the form of cell walls in the grain boundaries.

[0007] Furthermore, the high iron content samarium cobalt magnet has a coercive force of not less than 25 kOe, a squareness of not less than 0.75, and a maximum magnetic energy product of not less than 33 MGOe.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned high iron content samarium cobalt magnet, the preparation method specifically comprising the following steps:

[0009] S1) smelting a high iron content samarium-cobalt alloy raw material and a copper-rich auxiliary alloy raw material according to a designed ratio to obtain a high iron content samarium-cobalt alloy ingot and a copper-rich auxiliary alloy ingot;

[0010] S2) respectively and sequentially subjecting the high iron content samarium-cobalt alloy ingot and the copper-rich auxiliary alloy ingot obtained in S1) to coarse crushing, medium crushing and jet milling to obtain high iron content samarium-cobalt magnetic powder and copper-rich auxiliary alloy powder;

[0011] S3) mixing the high iron content samarium cobalt magnetic powder and the copper-rich auxiliary alloy powder obtained in S2) in a certain ratio, adding copper powder to the mixed magnetic powder, and then performing mixing, magnetic field forming, cold isostatic pressing and sintering in sequence to obtain a sintered dense magnet;

[0012] S4) subjecting the sintered magnet obtained in S3) to a two-stage solid solution treatment to obtain a single-phase solid solution precursor having a grain size greater than 65 μm;

[0013] S5) subjecting the solid solution precursor obtained in S4) to a three-stage aging treatment, and obtaining a high iron content samarium-cobalt magnet having a complete and uniform cellular structure and concentrated copper distribution in the cell wall.

[0014] Furthermore, the particle size of the high iron content samarium cobalt magnetic powder obtained in S2) is 3-5 μm, of which the powder with a size of 3.5-4.2 μm accounts for more than 90%; the particle size of the copper-rich auxiliary alloy powder is 2-4 μm, of which the powder with a size of 2-3 μm accounts for more than 90%.

[0015] Furthermore, the copper powder in S3) has a particle size of 0.5 to 3 μm, and the density of the magnet after sintering is 8.3 to 8.45 g / cm 3 .

[0016] Furthermore, the two-stage solution treatment process in S4) is as follows: the sintered blank is first kept at a temperature of 1180-1205°C for 1-4 hours, then kept at a temperature of 1150-1190°C for 4-48 hours, and then air-cooled or water-cooled to room temperature.

[0017] Furthermore, the three-stage aging process in S5) is specifically as follows: first, keep the temperature at 600-780°C for 1-5h, then keep the temperature at 780-870°C for 10-24h, then cool to 400-500°C at a rate of 0.4-1°C / min, keep the temperature for 1-15h, and finally air-cool or water-cool to room temperature.

[0018] The high iron content samarium cobalt magnet prepared by the above preparation method is used in the field of high-power permanent magnet motors or rail transportation.

[0019] The beneficial effects of the present invention are as follows: due to the adoption of the above technical scheme, the preparation method of the present invention adopts a dual alloy process to first mix the high iron content samarium cobalt main phase magnetic powder with the copper-rich auxiliary alloy powder, then add copper powder, and then perform mixing, magnetic field forming, cold isostatic pressing and sintering in sequence to obtain a sintered dense magnet; then a two-stage solid solution process is adopted to obtain a solid solution precursor with large-sized grains; finally, a three-stage aging process is adopted, so that the cellular structure in the final magnet crystal is complete and uniform, and the cell size is 100-150nm; the addition of an appropriate amount of copper-rich auxiliary alloy and copper powder avoids the appearance of copper-poor areas at the grain boundaries, and promotes the formation of copper-rich 1:5H phase in the form of cell walls in the grain boundaries. The prepared samarium cobalt magnet has both high coercivity and high squareness, is simple to operate, and is convenient for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flowchart of a method for preparing a high iron content samarium cobalt magnet. DETAILED DESCRIPTION

[0021] The present invention will be further illustrated below in conjunction with examples and comparative examples. It should be understood that the following specific embodiments are only used to illustrate the features and advantages of the present invention, and are not used to limit the scope of the present invention.

[0022] like Figure 1 As shown, the present invention provides a method for preparing a samarium-cobalt magnet with a high iron content. The method specifically comprises the following steps:

[0023] S1) smelting a high iron content samarium-cobalt alloy raw material and a copper-rich auxiliary alloy raw material respectively to obtain a high iron content samarium-cobalt alloy ingot and a copper-rich auxiliary alloy ingot;

[0024] S2) performing coarse crushing, medium crushing and jet milling on the high iron content samarium-cobalt alloy ingot and the copper-rich auxiliary alloy ingot obtained in S1) respectively;

[0025] S3) mixing the high iron content samarium cobalt magnetic powder obtained in S2) and the copper-rich auxiliary alloy powder in a ratio of 5:1 to 20:1, and adding 1 to 5 wt.% of copper powder to the mixed magnetic powder, and then performing mixing, magnetic field forming, cold isostatic pressing and sintering in sequence to obtain a sintered dense magnet;

[0026] S4) subjecting the sintered magnet obtained in S3) to a two-stage solid solution treatment to obtain a single-phase solid solution precursor having a grain size greater than 65 μm;

[0027] S5) subjecting the solid solution precursor obtained in S4) to a three-stage aging treatment to obtain a complete and uniform cellular structure inside the grains, and the copper element is concentratedly distributed at the cell wall.

[0028] Furthermore, the chemical formula of the high iron content samarium-cobalt alloy component in S1) is Sm(Co 1-a-b-c Fe a Cu b Zr c ) z , where 0.16≤a≤0.4, 0.04≤b≤0.1, 0.018≤c≤0.033, 7≤z≤8; the copper-rich auxiliary alloy composition is RE(Co 1- u Cu u )5, wherein RE is one or more of Pr, Nd, Sm, 0.4≤u≤1.

[0029] Furthermore, the particle size of the high iron content samarium cobalt magnetic powder obtained in S2) is 3-5 μm, of which the powder with a size of 3.5-4.2 μm accounts for more than 90%; the particle size of the copper-rich auxiliary alloy powder is 2-4 μm, of which the powder with a size of 2-3 μm accounts for more than 90%.

[0030] Furthermore, the particle size of the copper powder (S3) is 0.5-3 μm, and the density of the magnet after sintering is 8.3-8.45 g / cm 3 , and copper is enriched in the grain boundaries of the sintered magnet.

[0031] Furthermore, the two-stage solution process in S4) adds a shorter high-temperature insulation step before the conventional solution process, specifically, the sintered blank is kept at 1180-1205°C for 1-4h and at 1150-1190°C for 4-48h, and then air-cooled or water-cooled to room temperature.

[0032] Furthermore, as the two-stage solid solution process proceeds in the magnet in S4), the grain size gradually grows and the elements within the grain and at the grain boundaries gradually become homogenized, which not only greatly reduces the proportion of grain boundary defects in conventional magnets, but also suppresses the occurrence of copper-poor grain boundaries.

[0033] Furthermore, the three-stage aging process in S5) adds a low-temperature insulation step before the conventional two-stage aging process, specifically, the solid solution magnet is firstly kept at 600-780°C for 1-5h, then kept at 780-870°C for 10-24h, cooled to 400-500°C at a rate of 0.4-1°C / min, and kept at this temperature for 1-15h, and finally air-cooled or water-cooled to room temperature.

[0034] Furthermore, the cellular structure within the final magnet crystal obtained in S5) is complete and uniform, and the cell size is 100-150 nm; the addition of an appropriate amount of copper-rich auxiliary alloy and copper powder not only avoids the appearance of copper-poor areas at the grain boundaries, but also promotes the formation of copper-rich 1:5H phase in the form of cell walls at the grain boundaries, ultimately obtaining a samarium-cobalt magnet with a high iron content.

[0035] Example 1

[0036] In the first step, the nominal composition of Sm(Co 0.635 Fe 0.28 Cu 0.065 Zr 0.02 ) 7.75 and Sm(Co 0.5 Cu 0.5 )5 of high iron content samarium cobalt alloy and copper-rich auxiliary alloy. The second step is to coarsely crush, medium crush and air flow mill the obtained high iron content samarium cobalt alloy ingots and copper-rich auxiliary alloy ingots respectively. Among them, the particle size of high iron content samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%; the particle size of copper-rich auxiliary alloy powder is 2-4μm, of which the powder with a size of 2-3μm accounts for more than 90%. The third step is to mix the obtained high iron content samarium cobalt magnetic powder and copper-rich auxiliary alloy powder in a ratio of 10:1, and add 2wt.% of copper powder to the mixed magnetic powder, and then carry out mixing, magnetic field forming, cold isostatic pressing and sintering in turn to obtain a sintered dense magnet. Among them, the copper powder particle size is 1μm, and the density of the magnet after sintering is 8.35g / cm 3. The fourth step is to perform a two-stage solid solution treatment on the obtained sintered billet, specifically, keep it at 1195℃ for 2h and keep it at 1180℃ for 10h, and then air cool or water cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. As the two-stage solid solution process proceeds, the grain size of the magnet gradually grows and the elements in the grain and at the grain boundary gradually become homogenized, which not only greatly reduces the proportion of grain boundary defects in conventional magnets, but also inhibits the occurrence of grain boundary copper deficiency. The fifth step is to perform a three-stage aging treatment, specifically, keep the obtained solid solution magnet at 750℃ for 4h and 810℃ for 24h, then cool it to 400℃ at a rate of 0.5℃ / min, keep it at this temperature for 10h, and finally air cool or water cool it to room temperature. After aging, the intracrystalline cellular structure of the magnet is complete and uniform, and the copper element is concentrated at the cell wall, and the cell size is about 120nm. More importantly, the addition of an appropriate amount of copper-rich auxiliary alloy and copper powder not only avoids the appearance of copper-poor areas at the grain boundaries, but also promotes the formation of copper-rich 1:5H phase in the form of cell walls at the grain boundaries, ultimately obtaining samarium-cobalt magnets with a high iron content.

[0037] Example 2

[0038] The high iron content samarium-cobalt alloy with the same composition and the same preparation process as in Example 1 is used, the only difference being that the copper-rich auxiliary alloy component is selected as Sm(Co 0.4 Cu 0.6 )5.

[0039] Example 3

[0040] The high iron content samarium-cobalt alloy with the same composition and the same preparation process as in Example 1 is used, the only difference being that the copper-rich auxiliary alloy component is selected as Sm(Co 0.3 Cu 0.7 )5.

[0041] Example 4

[0042] The high iron content samarium-cobalt alloy with the same composition and the same preparation process as in Example 1 is used, the only difference is that the copper-rich auxiliary alloy component is selected as Pr 0.2 Sm 0.8 (Co 0.5 Cu 0.5 )5.

[0043] Comparative Example 1

[0044] The first step is to smelt a nominal composition of Sm(Co 0.635 Fe 0.28 Cu 0.065 Zr 0.02 ) 7.75The high iron content samarium cobalt alloy. In the second step, the obtained high iron content samarium cobalt alloy ingot is subjected to coarse crushing, medium crushing and air flow grinding in turn. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%. In the third step, the obtained high iron content samarium cobalt magnetic powder is mixed, magnetic field formed, cold isostatically pressed and sintered in turn to obtain a sintered dense magnet. The density of the magnet after sintering is 8.35g / cm 3 . The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1195°C for 2h and at 1180°C for 10h, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. The fifth step is to perform a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750°C for 4h and at 810°C for 20h, and then to cool it to 400°C at a rate of 0.5°C / min, and to keep it at this temperature for 10h, and finally to air-cool or water-cool it to room temperature. After aging, the intracrystalline cellular structure of the magnet is complete and uniform, and the copper element is concentrated at the cell wall, and the cell size is 120nm. However, there is no cellular structure at the grain boundary of the magnet, and it exhibits local copper deficiency.

[0045] Comparative Example 2

[0046] In the first step, the nominal composition of Sm(Co 0.635 Fe 0.28 Cu 0.065 Zr 0.02 ) 7.75 and Sm(Co 0.5 Cu 0.5 )5 of high iron content samarium cobalt alloy and copper-rich auxiliary alloy. The second step is to coarsely crush, medium crush and air flow mill the obtained high iron content samarium cobalt alloy ingots and copper-rich auxiliary alloy ingots respectively. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%; the particle size of copper-rich auxiliary alloy powder is 2-4μm, of which the powder with a size of 2-3μm accounts for more than 90%. The third step is to mix the obtained high iron content samarium cobalt magnetic powder and copper-rich auxiliary alloy powder in a ratio of 10:1, and then carry out mixing, magnetic field forming, cold isostatic pressing and sintering in turn to obtain a sintered dense magnet. The density of the magnet after sintering is 8.35g / cm 3. The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1195°C for 2h and at 1180°C for 10h, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. The fifth step is to conduct a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750°C for 4h and at 810°C for 24h, and then to cool it to 400°C at a rate of 0.5°C / min, and to keep it at this temperature for 10h, and finally to air-cool or water-cool it to room temperature. After aging, the cellular structure of the magnet is complete and uniform, and the copper element is concentrated in the cell wall, and the cell size is 120nm. The addition of an appropriate amount of copper-rich auxiliary alloy locally reduces the appearance of copper-poor areas at the grain boundaries, and to a certain extent promotes the formation of copper-rich 1:5H phase in the grain boundaries in the form of cell walls.

[0047] Comparative Example 3

[0048] The first step is to smelt a nominal composition of Sm(Co 0.635 Fe 0.28 Cu 0.065 Zr 0.02 ) 7.75 The second step is to subject the obtained high iron content samarium cobalt alloy ingot to coarse crushing, medium crushing and air flow grinding in sequence. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%. The third step is to add 2wt.% copper powder to the high iron content samarium cobalt magnetic powder, and then carry out mixing, magnetic field forming, cold isostatic pressing and sintering in sequence to obtain a sintered dense magnet. Among them, the copper powder particle size is 1μm, and the density of the magnet after sintering is 8.35g / cm 3 . The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1195°C for 2h and at 1180°C for 10h, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. As the two-stage solid solution process proceeds, the copper element enriched at the grain boundary is gradually homogenized, effectively avoiding the copper-poor phenomenon of the grain boundary of conventional magnets. The fifth step is to perform a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750°C for 4h and at 810°C for 24h, and then cool it to 400°C at a rate of 0.5°C / min, and keep it at this temperature for 10h, and finally to air-cool or water-cool it to room temperature. After aging, the cellular structure of the magnet is complete and uniform, and the copper element is concentrated at the cell wall, and the cell size is 120nm. The addition of an appropriate amount of copper powder avoids the appearance of copper-poor areas at the grain boundaries, but no copper-rich 1:5H cell wall phase is generated at the grain boundaries.

[0049] Example 5

[0050] In the first step, the nominal composition of Sm(Co 0.615 Fe0.31 Cu 0.055 Zr 0.02 ) 7.75 and Sm(Co 0.5 Cu 0.5 )5 of high iron content samarium cobalt alloy and copper-rich auxiliary alloy. The second step is to coarsely crush, medium crush and air flow mill the obtained high iron content samarium cobalt alloy ingots and copper-rich auxiliary alloy ingots respectively. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%; the particle size of copper-rich auxiliary alloy powder is 2-4μm, of which the powder with a size of 2-3μm accounts for more than 90%. The third step is to mix the obtained high iron content samarium cobalt magnetic powder and copper-rich auxiliary alloy powder in a ratio of 10:1, and add 2wt.% of copper powder to the mixed magnetic powder, and then carry out mixing, magnetic field forming, cold isostatic pressing and sintering in turn to obtain a sintered dense magnet. Among them, the copper powder particle size is 1μm, and the density of the magnet after sintering is 8.35g / cm 3 . The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1185℃ for 2h and at 1155℃ for 10h, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. As the two-stage solid solution process proceeds, the copper element enriched at the grain boundary is gradually homogenized, effectively avoiding the copper-poor phenomenon of the grain boundary of conventional magnets. The fifth step is to perform a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750℃ for 4h and at 810℃ for 24h, and then cool it to 400℃ at a rate of 0.5℃ / min, and keep it at this temperature for 10h, and finally air-cool or water-cool it to room temperature. After aging, the cellular structure of the magnet is complete and uniform, and the copper element is concentrated at the cell wall, and the cell size is 120nm. The addition of appropriate amounts of copper-rich auxiliary alloy and copper powder not only avoids the appearance of copper-poor areas at the grain boundaries, but also promotes the formation of copper-rich 1:5H phase in the form of cell walls at the grain boundaries, ultimately obtaining samarium-cobalt magnets with high iron content.

[0051] Example 6

[0052] The same high iron content samarium-cobalt alloy as in Example 5 was used and the same preparation process was used, except that the copper-rich auxiliary alloy component was selected as Sm(Co 0.4 Cu 0.6 )5.

[0053] Example 7

[0054] The same high iron content samarium-cobalt alloy as in Example 5 was used and the same preparation process was used, except that the copper-rich auxiliary alloy component was selected as Sm(Co 0.3 Cu 0.7 )5.

[0055] Example 8

[0056] The high iron content samarium-cobalt alloy with the same composition and the same preparation process as in Example 5 is used, the only difference being that the copper-rich auxiliary alloy component is selected as Pr 0.2 Sm 0.8 (Co 0.5 Cu 0.5 )5.

[0057] Comparative Example 4

[0058] The first step is to smelt the nominal composition Sm(Co 0.615 Fe 0.31 Cu 0.055 Zr 0.02 ) 7.75 The high iron content samarium cobalt alloy. In the second step, the obtained high iron content samarium cobalt alloy ingot is subjected to coarse crushing, medium crushing and air flow grinding in turn. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%. In the third step, the obtained high iron content samarium cobalt magnetic powder is mixed, magnetic field formed, cold isostatically pressed and sintered in turn to obtain a sintered dense magnet. The density of the magnet after sintering is 8.35g / cm 3 . The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1185°C for 2 hours and at 1155°C for 10 hours, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. The fifth step is to perform a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750°C for 4 hours and at 810°C for 20 hours, and then to cool it to 400°C at a rate of 0.5°C / min, and to keep it at this temperature for 10 hours, and finally to air-cool or water-cool it to room temperature. After aging, the cellular structure in the magnet crystal is complete and uniform, and the copper element is concentrated at the cell wall, and the cell size is 120nm. However, there is no cellular structure at the grain boundary, and local copper deficiency is exhibited.

[0059] Comparative Example 5

[0060] In the first step, the nominal composition of Sm(Co 0.615 Fe 0.31 Cu 0.055 Zr 0.02 ) 7.75 and Sm(Co 0.5 Cu 0.5)5 of high iron content samarium cobalt alloy and copper-rich auxiliary alloy. The second step is to coarsely crush, medium crush and air flow mill the obtained high iron content samarium cobalt alloy ingots and copper-rich auxiliary alloy ingots respectively. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%; the particle size of copper-rich auxiliary alloy powder is 2-4μm, of which the powder with a size of 2-3μm accounts for more than 90%. The third step is to mix the obtained high iron content samarium cobalt magnetic powder and copper-rich auxiliary alloy powder in a ratio of 10:1, and then carry out mixing, magnetic field forming, cold isostatic pressing and sintering in turn to obtain a sintered dense magnet. The density of the magnet after sintering is 8.35g / cm 3 . The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1185°C for 2h and at 1155°C for 10h, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. The fifth step is to perform a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750°C for 4h and at 810°C for 24h, and then cool it to 400°C at a rate of 0.5°C / min, and keep it at this temperature for 10h, and finally to air-cool or water-cool it to room temperature. After aging, the cellular structure of the magnet is complete and uniform, and the copper element is concentrated in the cell wall, and the cell size is 120nm. The addition of an appropriate amount of copper-rich auxiliary alloy locally reduces the appearance of copper-poor areas at the grain boundaries, and to a certain extent promotes the formation of copper-rich 1:5H phase in the grain boundaries in the form of cell walls.

[0061] Comparative Example 6

[0062] In the first step, the nominal composition of Sm(Co 0.615 Fe 0.31 Cu 0.055 Zr 0.02 ) 7.75 The second step is to subject the obtained high iron content samarium cobalt alloy ingot to coarse crushing, medium crushing and air flow grinding in sequence. Among them, the particle size of samarium cobalt magnetic powder is 3-5μm, of which the powder with a size of 3.5-4.2μm accounts for more than 90%. The third step is to add 2wt.% copper powder to the high iron content samarium cobalt magnetic powder, and then carry out mixing, magnetic field forming, cold isostatic pressing and sintering in sequence to obtain a sintered dense magnet. Among them, the copper powder particle size is 1μm, and the density of the magnet after sintering is 8.35g / cm 3. The fourth step is to subject the obtained sintered billet to a two-stage solid solution treatment, specifically, to keep it at 1185℃ for 2h and at 1155℃ for 10h, and then to air-cool or water-cool it to room temperature to obtain a single-phase solid solution precursor with a grain size greater than 65μm. As the two-stage solid solution process proceeds, the copper element enriched at the grain boundary is gradually homogenized, effectively avoiding the copper-poor phenomenon of the grain boundary of conventional magnets. The fifth step is to perform a three-stage aging treatment, specifically, to keep the obtained solid solution magnet at 750℃ for 4h and at 810℃ for 24h, and then cool it to 400℃ at a rate of 0.5℃ / min, and keep it at this temperature for 10h, and finally air-cool or water-cool it to room temperature. After aging, the cellular structure of the magnet is complete and uniform, and the copper element is concentrated at the cell wall, and the cell size is 120nm. The addition of an appropriate amount of copper powder avoids the appearance of copper-poor areas at the grain boundaries, but there is still no copper-rich 1:5H cell wall phase generated at the grain boundaries.

[0063] The magnets prepared in the above examples and their comparative examples were subjected to room temperature (20° C.) magnetic performance tests using a permanent magnetic material measurement system. The performance results are shown in Table 1 below.

[0064] Table 1 Comparison of magnet performance parameters in the embodiments and comparative examples

[0065]

[0066] Comparing the magnetic performance data of Example 1 and Comparative Example 1, it is found that the coercive force (H cj ), squareness (H k / H cj ) and the maximum magnetic energy product ((BH) max ) is significantly higher than the control example. Further, by comparing the magnetic properties data of Examples 2 to 8 and Comparative Examples 2 to 8, the magnetic properties of the embodiments are all better than those of the control example. It can be seen that by adding an appropriate amount of copper-rich auxiliary alloy and a small amount of pure copper powder to the high-iron content samarium cobalt magnetic powder, not only the copper-poor phenomenon at the grain boundaries of conventional magnets is effectively avoided, but also a cellular tissue structure can be constructed at the grain boundaries. It is worth noting that the pure copper powder plays a role in wetting the grain boundaries in the magnet, making the cellular tissue structure at the grain boundaries more uniform and complete. The synergistic effect of the copper-rich auxiliary alloy and the pure copper powder greatly improves the coercive force, squareness and maximum magnetic energy product of the high-iron content samarium cobalt magnet. The present invention provides a high-iron content samarium cobalt magnet and a preparation method thereof, which have important guiding significance for the preparation of high-iron content samarium cobalt magnets.

[0067] The above is a detailed introduction to a high iron content samarium cobalt magnet and its preparation method provided in the embodiment of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application; at the same time, for ordinary technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0068] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0069] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0070] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0071] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A high iron content samarium cobalt magnet, characterized in that: The high iron content samarium cobalt magnet comprises: a high iron content samarium cobalt alloy, a copper-rich auxiliary alloy and copper powder, wherein the mass ratio of the high iron content samarium cobalt alloy to the copper-rich auxiliary alloy is 5:1-20:1; and the copper powder accounts for 1-5wt.% of the sum of the mass of the high iron content samarium cobalt alloy and the copper-rich auxiliary alloy.

2. The high iron content samarium cobalt magnet according to claim 1, characterized in that: The high iron content samarium-cobalt alloy component chemical formula is Sm(Co 1-a-b-c Fe a Cu b Zr c ) z , where 0.16≤a≤0.4, 0.04≤b≤0.1, 0.018≤c≤0.033, 7≤z≤8; the copper-rich auxiliary alloy composition is RE(Co 1-u Cu u )5, wherein RE is one or more of Pr, Nd, Sm, 0.4≤u≤1.

3. The high iron content samarium cobalt magnet according to claim 1, characterized in that: The cell structure in the final magnet crystal of the high-iron-content samarium-cobalt magnet is complete and uniform, and the cell size is 100-150nm; the copper-rich 1:5H phase is generated in the grain boundary in the form of cell wall.

4. The high iron content samarium cobalt magnet according to claim 1, characterized in that: The high iron content samarium cobalt magnet has a coercive force of not less than 25 kOe, a squareness of not less than 0.75, and a maximum magnetic energy product of not less than 33 MGOe.

5. A method for preparing a high iron content samarium cobalt magnet as claimed in any one of claims 1 to 4, characterized in that: The preparation method specifically comprises the following steps: S1) smelting a high iron content samarium-cobalt alloy raw material and a copper-rich auxiliary alloy raw material according to a designed ratio to obtain a high iron content samarium-cobalt alloy ingot and a copper-rich auxiliary alloy ingot; S2) respectively and sequentially subjecting the high iron content samarium-cobalt alloy ingot and the copper-rich auxiliary alloy ingot obtained in S1) to coarse crushing, medium crushing and jet milling to obtain high iron content samarium-cobalt magnetic powder and copper-rich auxiliary alloy powder; S3) mixing the high iron content samarium cobalt magnetic powder and the copper-rich auxiliary alloy powder obtained in S2) in a certain ratio, adding copper powder to the mixed magnetic powder, and then performing mixing, magnetic field forming, cold isostatic pressing and sintering in sequence to obtain a sintered dense magnet; S4) subjecting the densely sintered magnet obtained in S3) to a two-stage solid solution treatment to obtain a single-phase solid solution precursor having a grain size greater than 65 μm; S5) subjecting the single-phase solid solution precursor obtained in S4) to a three-stage aging treatment to obtain a high-iron content samarium-cobalt magnet having a complete and uniform cellular structure and concentrated copper distribution in the cell wall.

6. The preparation method according to claim 5, characterized in that: The particle size of the high iron content samarium cobalt magnetic powder obtained in S2) is 3-5 μm, of which the powder with a size of 3.5-4.2 μm accounts for more than 90%; the particle size of the copper-rich auxiliary alloy powder is 2-4 μm, of which the powder with a size of 2-3 μm accounts for more than 90%.

7. The preparation method according to claim 5, characterized in that: The copper powder in S3) has a particle size of 0.5 to 3 μm, and the density of the magnet after sintering is 8.3 to 8.45 g / cm 3 .

8. The preparation method according to claim 5, characterized in that: The two-stage solution treatment process in S4) is specifically as follows: the sintered blank is first kept at a temperature of 1180-1205°C for 1-4 hours, then kept at a temperature of 1150-1190°C for 4-48 hours, and then air-cooled or water-cooled to room temperature.

9. The preparation method according to claim 5, characterized in that: The three-stage aging process in S5) is specifically as follows: first, keep the temperature at 600-780°C for 1-5h, then keep the temperature at 780-870°C for 10-24h, then cool to 400-500°C at a rate of 0.4-1°C / min, keep the temperature for 1-15h, and finally cool to room temperature by air or water.

10. A high iron content samarium cobalt magnet prepared by the preparation method according to any one of claims 5 to 9, which is used in high-power permanent magnet motors or rail transportation fields.

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