High-temperature-stability rare earth cobalt permanent magnet material and preparation method thereof

Abstract

The invention relates to a high-temperature-stability rare earth cobalt permanent magnet material and a preparation method thereof, belongs to the technical field of rare earth permanent magnet materials, and solves the problems of poor temperature stability and large temperature coefficient and magnetic flux change of a permanent magnet material in the prior art. The invention relates to a high-temperature-stability rare earth cobalt permanent magnet material, which is prepared by compounding 50-80% by mass of an alloy A and 50-80% by mass of an alloy B, the alloy A comprises 2-4 rare earth elements, and the content of Gd in the rare earth elements is not less than 50%; the B alloy comprises 2-4 rare earth elements, wherein the content of Sm in the rare earth elements is not less than 80%. And the preparation of the rare earth cobalt permanent magnet material with high temperature stability is realized.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth permanent magnet materials, and in particular to a rare earth cobalt permanent magnet material with high temperature stability and a preparation method thereof. Background Art

[0002] Rare earth permanent magnet materials have excellent magnetic properties and have been widely used in important fields such as aerospace equipment and high-precision instruments and meters. In the application process, permanent magnet materials, as magnetic field sources, are required to provide stable and reliable magnetic fields under various service conditions to achieve stable operation of the equipment.

[0003] Among the current rare earth permanent magnet materials, NdFeB permanent magnet materials have the highest magnetic energy product, but poor temperature stability, and the operating temperature is usually below 200°C. Although SmCo permanent magnet materials have good comprehensive performance in magnetic properties and temperature stability, their stable service temperature and temperature coefficient are still relatively large, making it difficult to meet the application requirements of high-end equipment for high stability and high-temperature service reliability of permanent magnet materials.

[0004] Magnets with small temperature coefficient and flux changes have high temperature stability. Existing studies have shown that rare earth permanent magnet materials can reduce the temperature coefficient of the magnet by adding heavy rare earth elements to form heavy rare earth / transition metal compounds. For example, by adding heavy rare earth elements to samarium cobalt magnets to replace metallic samarium elements, the residual magnetism temperature coefficient can be reduced from around -0.035% / ℃ to better than -0.01% / ℃ in the range of room temperature to 100 degrees Celsius. However, the addition of too much heavy rare earth will significantly reduce the residual magnetism and coercive force of the magnet, causing the performance of the magnet to drop sharply, and at the same time cannot meet the higher temperature range.

[0005] In order to improve the temperature resistance of magnets, the ratio of iron and cobalt in the magnets can be adjusted to obtain a higher Curie temperature, thereby improving the high-temperature stability of the magnets. A high proportion of cobalt will also cause the performance of the magnets to decline, and its temperature coefficient will also remain at a high level, but it cannot meet the requirements of low reversible magnetic loss at high temperatures. At the same time, the single design of composition and particle size in the magnet preparation process makes the magnet performance and stability not highly adaptable, making it difficult to obtain excellent comprehensive magnetic properties of magnets in a high service temperature range environment. Summary of the invention

[0006] In view of the above analysis, the embodiments of the present invention aim to provide a rare earth cobalt permanent magnet material with high temperature stability and a preparation method thereof, so as to solve at least one of the problems of existing permanent magnet materials such as poor temperature stability, large temperature coefficient and magnetic flux variation.

[0007] On the one hand, an embodiment of the present invention provides a high temperature stability rare earth cobalt permanent magnet material, which is prepared by compounding A alloy and B alloy in a mass ratio, wherein the mass of A alloy accounts for 50% to 80%; the A alloy includes 2 to 4 rare earth elements, wherein the content of Gd element in the rare earth elements is not less than 50%; the B alloy includes 2 to 4 rare earth elements, wherein the content of Sm element in the rare earth elements is not less than 80%.

[0008] Preferably, the chemical composition of the A alloy is (Gd a Dy b Er c Sm 1-a-b-c ) x Co y Cu z Zr w Fe 100-x-y-z-w , wherein the rare earth element composition ratio is: a=0.1~0.6, b=0~0.2, c=0~0.1, and the mass percentage is: x=22~25, y=45~50, z=6~11, and w=2~5.

[0009] Preferably, the chemical composition of the B alloy is (Gd a Dy b Er c Sm 1-a-b-c ) x Co y Cu z Zr w Fe 100-x-y-z-w , wherein the rare earth element composition ratio is: a=0.1~0.6, b=0~0.2, c=0~0.1, and the mass percentage is: x=25~28, y=55~60, z=6~11, and w=2~5.

[0010] Preferably, the performance of the high temperature stability permanent magnet material is that the remanence Br is greater than 8.7 kGs at room temperature 20°C, the knee coercivity Hk is greater than 16 KOe, and the remanence Br temperature coefficient is 0.015-0.025% / °C in the temperature range of 20-300°C.

[0011] On the other hand, an embodiment of the present invention further provides a method for preparing a rare earth cobalt permanent magnetic material with high temperature stability, which is used to prepare the permanent magnetic material, comprising the following steps:

[0012] S1. Alloy smelting: The materials are prepared according to the designed proportion of alloy elements, and the raw materials are melted into alloy A ingot and alloy B ingot respectively in a high vacuum induction melting furnace, and the ingots are roughly crushed into coarse powder particles not larger than 1 mm;

[0013] S2, ball milling: the A and B alloy coarse powder particles obtained in S1 are crushed by ball milling into A alloy fine magnetic powder and B alloy fine magnetic powder;

[0014] S3, orientation pressing: the fine magnetic powder of alloy A and the fine magnetic powder of alloy B obtained in S2 are fully mixed according to a composite ratio and then oriented pressed to obtain a magnet blank;

[0015] S4. Heat treatment: The magnet blank prepared in S3 is subjected to densification sintering and tempering heat treatment under vacuum conditions to obtain a permanent magnet material product.

[0016] Preferably, in S2, the particle size of the fine magnetic powder of alloy A is 4.5-6.0 μm, and the particle size of the fine magnetic powder of alloy B is 2.5-4.0 μm.

[0017] Specifically, the density of the magnet blank in S3 is 4.5-6.0 g / cm 3 .

[0018] Furthermore, the densification sintering process described in S4 is: the magnet blank is degassed at a high vacuum temperature below 500°C, the temperature is raised to 1190-1210°C for pre-sintering, the pre-sintering time is 30-50 minutes, and then the temperature is raised to 1220-1230°C for densification sintering. After the sintering and holding time is 40-70 minutes, high-purity argon is introduced and the temperature is quickly lowered to 1170-1200°C for solution treatment for 1-3 hours.

[0019] Exemplarily, the tempering heat treatment in S4 is: cooling to 820-870° C. and keeping the temperature for 15-25 hours, and then gradually cooling to room temperature.

[0020] Furthermore, the cooling rate of the gradient slow cooling to room temperature in S4 is: the cooling rate in the high temperature section is 0.7-0.9°C / min, and the cooling rate below 500°C is not less than 1.5°C / min.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] 1. The present invention obtains an alloy composition that can meet different temperature stability requirements by designing an alloy composition with high use temperature and low temperature coefficient rare earth / cobalt elements added in combination, optimizes rare earth elements, especially the Gd element content and the Fe / Co element ratio, realizes the regulation of magnet temperature characteristics, remanence and coercive force, so that the permanent magnet material obtains high temperature resistance while maintaining a high knee point coercive force. The prepared permanent magnet material has a high use temperature and a low reversible temperature coefficient, exhibits excellent comprehensive magnetic properties, can meet the application requirements of high stability of magnets in a wide temperature range service environment, and is suitable for various types of high-precision magnetic sensors, high-temperature magnetic transmissions and magnetic control devices, etc.;

[0023] The composite preparation of two alloy fine magnetic powders A and B with different particle size distributions can take into account the fluidity of the magnetic powder and obtain a higher degree of orientation, improve the sintering densification process, contribute to the consistency of magnet performance, and thus improve the magnetic properties of the material.

[0024] 2. The permanent magnet material preparation method of the present invention adopts a dual particle size distribution and a higher compact density, which improves the uniformity of the magnet; the preparation process does not require oxygen control and maintains a higher oxygen content. Combined with the reasonable design of the heat treatment process, it promotes the formation of the magnet's temperature-resistant micromagnetic structure and reduces the magnetic property loss of the magnet under high-temperature application conditions.

[0025] 3. The present invention obtains good organizational structure and magnetic properties through the optimization design of the heat treatment process, and the prepared high-temperature stability rare earth cobalt permanent magnet material has excellent temperature resistance and low magnetic loss changes in a wide temperature range.

[0026] 4. Through the design of high rare earth / cobalt element composite addition components and combined with process control, the prepared permanent magnetic material has high comprehensive magnetic properties, high temperature resistance and magnetic stability, and an operating temperature of over 300°C. The temperature coefficient is 0.015-0.025% / °C in a wide temperature range from room temperature 20°C to 300°C, and the high and low temperature cyclic impact magnetic loss is less than 1.5%. Compared with existing permanent magnetic materials, it achieves high temperature stability while maintaining relatively high magnetic properties.

[0027] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0029] Figure 1 is a test curve of the magnetic properties of the permanent magnetic material at room temperature in Example 2 of the present invention;

[0030] Figure 2 Magnetic property test curve of the permanent magnetic material at 300° C. in Example 2 of the present invention;

[0031] Figure 3 This is a scanning electron microscope image of the permanent magnetic material of the present invention. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0033] On the one hand, a specific embodiment of the present invention discloses a high temperature stability rare earth cobalt permanent magnet material, which is prepared by compounding A alloy and B alloy in a mass ratio, wherein the mass of A alloy accounts for 50% to 80%; the A alloy includes 2 to 4 rare earth elements, wherein the content of Gd element in the rare earth elements is not less than 50%; the B alloy includes 2 to 4 rare earth elements, wherein the content of Sm element in the rare earth elements is not less than 80%.

[0034] The Gd content in alloy A is not less than 50%, which can significantly reduce the temperature coefficient of the alloy and improve the temperature resistance. The samarium (Sm) content in alloy B is not less than 80%. The ratio design of samarium and Fe / Co can improve the remanence and intrinsic coercivity of the magnet and optimize the knee coercivity, thereby enhancing the temperature resistance and anti-demagnetization ability of the magnet. The comprehensive characteristics of rare earth elements and ferromagnetic elements are fully utilized to achieve high temperature resistance, high coercivity and good chemical stability.

[0035] The chemical composition of the alloy A is (Gd a Dy b Er c Sm 1-a-b-c ) x Co y Cu z Zr w Fe 100-x-y-z-w , wherein the rare earth element composition ratio is: a=0.1~0.6, b=0~0.2, c=0~0.1, and the mass percentage is: x=22~25, y=45~50, z=6~11, and w=2~5.

[0036] The chemical composition of the B alloy is (Gd a Dy b Er c Sm 1-a-b-c ) x Co y Cu z Zr w Fe 100-x-y-z-w , wherein the rare earth element composition ratio is: a=0.1~0.6, b=0~0.2, c=0~0.1, and the mass percentage is: x=25~28, y=55~60, z=6~11, and w=2~5.

[0037] It adopts dual alloy composite preparation, and through composite composition design, the alloy composition that can meet the requirements of different temperature stability is obtained, the ratio of rare earth elements to Fe / Co elements is optimized, and the temperature characteristics, remanence and coercive force of the magnet are regulated, so that the permanent magnet material can obtain high temperature resistance while maintaining a high knee point coercive force.

[0038] like Figure 3 As shown, the permanent magnetic material of the present invention has no microscopic defects such as cracks or holes, and has a dense microstructure.

[0039] The performance of the high temperature stability permanent magnet material is that the remanence Br is greater than 8.7 kGs at room temperature 20°C, the knee point coercive force Hk is greater than 16 KOe, and the remanence Br temperature coefficient is 0.015-0.025% / °C in the temperature range of 20-300°C.

[0040] On the one hand, a specific embodiment of the present invention discloses a method for preparing a rare earth cobalt permanent magnet material with high temperature stability, comprising the following steps:

[0041] S1. Alloy smelting: The materials are prepared according to the designed proportion of alloy elements, and the raw materials are melted into alloy A ingot and alloy B ingot respectively in a high vacuum induction melting furnace, and the ingots are roughly crushed into coarse powder particles not larger than 1 mm;

[0042] S2, ball milling: the A and B alloy coarse powder particles obtained in S1 are crushed by ball milling into A alloy fine magnetic powder and B alloy fine magnetic powder;

[0043] S3, orientation pressing: the fine magnetic powder of alloy A and the fine magnetic powder of alloy B obtained in S2 are fully mixed according to a composite ratio and then oriented pressed to obtain a magnet blank;

[0044] S4. Heat treatment: performing densification sintering and tempering heat treatment on the magnet blank under vacuum conditions to obtain a permanent magnet material product.

[0045] In S2, the fine magnetic powder particle size of alloy A is 4.5-6.0 μm, and the fine magnetic powder particle size of alloy B is 2.5-4.0 μm. Specifically, the fine magnetic powder particle size of alloy A is 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 5.1 μm, 5.5 μm, 5.8 μm, and 6.0 μm; the fine magnetic powder particle size of alloy B is 2.5 μm, 2.8 μm, 3.6 μm, 3.9 μm, and 4.0 μm.

[0046] The finer the magnetic powder particle size, the worse the fluidity of the magnetic powder; if the magnetic powder particle size is too large, it will lead to poor adaptability to the oriented pressing process, and the density of the magnet blank obtained after pressing will be low, which will affect the quality of the permanent magnet material product; the composite preparation of two alloy fine magnetic powders A and B with different particle size distributions can take into account the fluidity of the magnetic powder and obtain a higher degree of orientation, improve the sintering densification process, help the consistency of the magnet performance, and thus improve the magnetic properties of the material.

[0047] Preferably, the ball milling process uses an inert protective medium to prevent the magnetic powder from contacting the air, and the ball milling process uses a single diameter steel ball to more accurately control the particle size distribution of the powder during the ball milling process.

[0048] The density of the magnet blank in S3 is 4.5-6.0 g / cm 3 , higher pressed billet density can promote magnet densification, improve the orderliness of magnetic powder orientation, reduce pores and shrinkage deformation rate, and improve the consistency of magnets after sintering.

[0049] The heat treatment process in S4 is carried out in a vacuum heat treatment furnace.

[0050] The densification sintering process described in S4 is as follows: the magnet blank is degassed at a high vacuum temperature below 500°C, and the temperature is raised to 1190-1210°C for pre-sintering for 30-50 minutes, and then the temperature is raised to 1220-1230°C for densification sintering, and the sintering heat preservation time is 40-70 minutes; after densification sintering, high-purity argon gas is introduced to quickly cool the temperature to 1170-1200°C for solution treatment for 1-3 hours.

[0051] During the sintering process, the particles of the two alloys A and B combine with each other through diffusion and flow to form the precursor phase structure. The composite preparation of fine magnetic powders of the two alloys A and B with different particle size distributions can take into account the fluidity of the magnetic powder and obtain a higher degree of orientation, thereby improving the density of the precursor phase during the sintering process.

[0052] Pre-sintering before densification sintering helps to achieve better densification effect during high-temperature sintering by initially consolidating the powder at a lower temperature, increasing the density of the sintered body and reducing impurities and inhomogeneities at the grain boundaries.

[0053] The tempering heat treatment in S4 is: cooling to 820-870°C and keeping the temperature for 15-25h, and then slowly cooling to room temperature.

[0054] During the tempering heat treatment process, the cooling rate of the gradient slow cooling to room temperature is: the cooling rate in the high temperature section is 0.7-0.9°C / min, and the cooling rate below 500°C is not less than 1.5°C / min.

[0055] The permanent magnet material product obtained in S4 has an oxygen content of 2800-3800 ppm, that is, the preparation process does not need to control the oxygen content. When the rare earth cobalt permanent magnet material product is prepared by the present invention, a certain oxygen content is conducive to the stability of the magnet process.

[0056] The permanent magnet material product obtained in S4 has a high and low temperature impact magnetic flux change rate of less than 1.5% in the temperature range of 20 to 300°C.

[0057] In summary, the present invention, through the design of the composition of rare earth / cobalt element composite addition, combined with process control, the permanent magnet material prepared has high temperature resistance and magnetic stability, the use temperature is above 300°C, and the temperature coefficient is 0.015-0.025% / °C in a wide temperature range from room temperature 20°C to 300°C, and the high and low temperature cycle impact magnetic loss is less than 1.5%. Compared with the existing permanent magnet materials, it achieves high temperature stability while maintaining higher magnetic properties.

[0058] The high temperature stability rare earth cobalt permanent magnet material and the preparation method thereof of the present invention are described below with reference to specific embodiments.

[0059] Example 1

[0060] This embodiment provides a rare earth cobalt permanent magnet material with high temperature stability and a preparation method thereof.

[0061] The chemical composition of alloy A is (Gd 0.6 Sm 0.4 ) 22.6 Co 48.5 Cu6Zr 4.7 Fe 18.2 , B alloy chemical composition is (Dy 0.2 Sm 0.8 ) 27.6 Co 56 Cu 7.5 Zr 2.2 Fe 6.7 .

[0062] The specific preparation process is as follows:

[0063] S1. Alloy smelting: prepare two alloy raw materials A and B according to the designed element ratio, and melt and cast them into A alloy ingot and B alloy ingot in a high vacuum induction melting furnace. The weight of a single alloy ingot is about 30kg;

[0064] S2. Ball milling: The A and B alloy ingots are respectively crushed into coarse powder particles not larger than 1 mm, and then put into a ball mill to grind into fine magnetic powder that meets the requirements. Inert protective medium is used in the powder making process to prevent the magnetic powder from contacting with the air. A single diameter steel ball is used in the ball milling process. The ball milling time is adjusted to control the average particle size of the A alloy powder to be 4.6 μm and the average particle size of the B alloy powder to be 2.8 μm.

[0065] S3, Orientation Pressing: The two alloy magnetic powders are evenly distributed in a ratio of 50% by weight of alloy A and alloy B, and fully mixed, and then put into an orientation forming press for one high-pressure orientation pressing. After pressing, the high-stability rare earth cobalt magnet blank is obtained, and the density of the blank is 4.5-4.7g / cm 3 ;

[0066] S4, heat treatment: the magnet blank is placed in a vacuum heat treatment furnace for densification sintering and tempering heat treatment. The main steps of the process include: degassing the magnet blank at a high vacuum temperature below 500°C, heating it to a temperature range of 1197-1203°C for pre-sintering for about 30 minutes, then heating it to 1223-1228°C for densification sintering treatment, keeping it warm for 40-50 minutes, introducing high-purity argon gas and quickly cooling it to 1183-1200°C for solution treatment for 1 hour, then cooling it to 845-860°C and keeping it warm for 20-25 hours, then slowly cooling it to room temperature with a cooling rate of 0.7-0.9°C / min in the high temperature section and a cooling rate of not less than 1.5°C / min below 500°C. The blank is taken out of the heat treatment furnace to obtain the high temperature stability rare earth cobalt permanent magnet material of the present invention.

[0067] The permanent magnet material blank obtained in S4 was sampled for performance testing according to the test standard. The magnetic properties of the samples were tested at room temperature 20°C and high temperature 300°C using a permanent magnet demagnetization curve measuring instrument. The data are shown in Table 1.

[0068] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0069] The permanent magnetic material prepared by the present invention exhibits excellent high temperature stability.

[0070] Example 2

[0071] This embodiment provides a rare earth cobalt permanent magnet material with high temperature stability and a preparation method thereof.

[0072] The chemical composition of alloy A is (Gd 0.5 Dy 0.1 Sm 0.4 ) 24.9 Co 50 Cu 8.2 Zr 3.8 Fe 13.1The chemical composition of alloy B is (Gd 0.05 Sm 0.95 ) 25.9 Co 59.2 Cu 6.2 Zr 2.6 Fe 6.1 .

[0073] The specific preparation process is as follows:

[0074] S1. Alloy smelting: prepare two alloy raw materials A and B according to the designed element ratio, and melt and cast them into A alloy ingot and B alloy ingot in a high vacuum induction melting furnace. The weight of a single alloy ingot is about 30kg;

[0075] S2. Ball milling: The A and B alloy ingots are respectively crushed into coarse powder particles not larger than 1 mm, and then put into a ball mill to grind into fine magnetic powder that meets the requirements. Inert protective medium is used in the powder making process to prevent the magnetic powder from contacting with the air. A single diameter steel ball is used in the ball milling process. The ball milling time is adjusted to control the average particle size of the A alloy powder to be 4.7 μm and the average particle size of the B alloy powder to be 3.6 μm.

[0076] S3, Orientation Pressing: The two alloy magnetic powders are evenly distributed and fully mixed according to the weight ratio of A alloy accounting for 80% and B alloy accounting for 20%, and then put into the orientation forming press for one high-pressure orientation pressing. After pressing, the high-stability rare earth cobalt magnet blank is obtained, and the density of the blank is 4.6-4.9g / cm 3 ;

[0077] S4, heat treatment: the magnet blank is placed in a vacuum heat treatment furnace for densification sintering and tempering heat treatment. The main steps of the process include: degassing the magnet blank at a high vacuum temperature below 500°C, heating it to a temperature range of 1192-1197°C for pre-sintering for about 40 minutes, then heating it to 1221-1226°C for densification sintering, keeping it warm for 60-70 minutes, introducing high-purity argon gas to quickly cool it to 1175-1190°C for solution treatment for 3 hours, then cooling it to 835-850°C for insulation for 15-20 hours, then slowly cooling it to room temperature with a cooling rate of 0.7-0.9°C / min in the high temperature section and a cooling rate of not less than 1.5°C / min below 500°C. The blank is taken out of the heat treatment furnace to obtain the high temperature stability rare earth cobalt permanent magnet material of the present invention.

[0078] The permanent magnet material blank obtained in S4 was sampled for performance testing according to the test standard. The magnetic properties of the samples were tested at room temperature 20°C and high temperature 300°C using a permanent magnet demagnetization curve measuring instrument. The data are shown in Table 1.

[0079] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0080] The permanent magnetic material prepared by the present invention exhibits excellent high temperature stability.

[0081] The demagnetization curves of the permanent magnet material in this embodiment at room temperature of 300°C are as follows: Figure 1 and Figure 2 shown.

[0082] Example 3

[0083] This embodiment provides a rare earth cobalt permanent magnet material with high temperature stability and a preparation method thereof.

[0084] The chemical composition of alloy A is (Gd 0.55 Er 0.05 Sm 0.4 ) 24.3 Co 46 Cu 10.5 Zr 4.1 Fe 15.1 , B alloy chemical composition is (Dy 0.05 Er 0.1 Sm 0.85 ) 26.1 Co 55 Cu8Zr 3.6 Fe 7.3 .

[0085] The specific preparation process is as follows:

[0086] S1. Alloy smelting: prepare two alloy raw materials A and B according to the designed element ratio, and melt and cast them into A alloy ingot and B alloy ingot in a high vacuum induction melting furnace. The weight of a single alloy ingot is about 30kg;

[0087] S2. Ball milling: The A and B alloy ingots are respectively crushed into coarse powder particles not larger than 1 mm, and then put into a ball mill to grind into fine magnetic powder that meets the requirements. Inert protective medium is used in the powder making process to prevent the magnetic powder from contacting with the air. A single diameter steel ball is used in the ball milling process. The ball milling time is adjusted to control the average particle size of the A alloy powder to be 5.1 μm and the average particle size of the B alloy powder to be 3.9 μm.

[0088] S3, Orientation Pressing: The two alloy magnetic powders are evenly distributed and fully mixed according to the weight ratio of A alloy accounting for 75% and B alloy accounting for 25%, and then put into the orientation forming press for one high-pressure orientation pressing. After pressing, the high-stability rare earth cobalt magnet blank is obtained, and the density of the blank is 4.8-5.1g / cm 3 ;

[0089] S4, heat treatment: the magnet blank is placed in a vacuum heat treatment furnace for densification sintering and tempering heat treatment. The main steps of the process include: degassing the magnet blank at a high vacuum temperature below 500°C, heating it to a temperature range of 1192-1197°C for pre-sintering for about 40 minutes, then heating it to 1221-1226°C for densification sintering, keeping it warm for 60-70 minutes, introducing high-purity argon gas to quickly cool it to 1175-1190°C for solution treatment for 3 hours, then cooling it to 835-850°C for insulation for 15-20 hours, then slowly cooling it to room temperature with a cooling rate of 0.7-0.9°C / min in the high temperature section and a cooling rate of not less than 1.5°C / min below 500°C. The blank is taken out of the heat treatment furnace to obtain the high temperature stability rare earth cobalt permanent magnet material of the present invention.

[0090] The permanent magnet material blank obtained in S4 was sampled for performance testing according to the test standard. The magnetic properties of the samples were tested at room temperature 20°C and high temperature 300°C using a permanent magnet demagnetization curve measuring instrument. The data are shown in Table 1.

[0091] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0092] The permanent magnetic material prepared by the present invention exhibits excellent high temperature stability.

[0093] Comparative Example 1

[0094] This embodiment provides a rare earth cobalt permanent magnet material and a preparation method thereof.

[0095] The specific preparation process is the same as that of Example 1, except that only alloy A is used.

[0096] The permanent magnet material blanks were sampled for performance testing according to the test standards. The magnetic properties of the samples were tested at room temperature 20°C and high temperature 300°C using a permanent magnet demagnetization curve measuring instrument. The data are shown in Table 1.

[0097] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0098] Comparative Example 2

[0099] This embodiment provides a rare earth cobalt permanent magnet material and a preparation method thereof.

[0100] The specific preparation process is the same as that of Example 1, except that the proportion of alloy A is 40%.

[0101] The permanent magnet material blanks were sampled for performance testing according to the test standards, and the magnetic performance data of the samples at room temperature 20°C and high temperature 300°C were tested using a permanent magnet demagnetization curve measuring instrument, see Table 1.

[0102] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0103] Comparative Example 3

[0104] This embodiment provides a rare earth cobalt permanent magnet material and a preparation method thereof.

[0105] The specific preparation process is the same as that of Example 1, except that the average particle sizes of the A and B alloy powders are 8 μm and 5 μm, respectively.

[0106] The permanent magnet material blanks were sampled for performance testing according to the test standards, and the magnetic performance data of the samples at room temperature 20°C and high temperature 300°C were tested using a permanent magnet demagnetization curve measuring instrument: see Table 1.

[0107] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0108] Comparative Example 4

[0109] This embodiment provides a rare earth cobalt permanent magnet material and a preparation method thereof.

[0110] The specific preparation process is the same as that of Example 1, except that no pre-sintering is performed in S4.

[0111] The permanent magnet material blanks were sampled for performance testing according to the test standards. The magnetic properties of the samples were tested at room temperature 20°C and high temperature 300°C using a permanent magnet demagnetization curve measuring instrument. The data are shown in Table 1.

[0112] The flux meter and oxygen content analyzer were used to detect the high and low temperature flux changes and oxygen content. The results are shown in Table 1.

[0113] Table 1 Performance test data of permanent magnetic materials of embodiments and comparative examples

[0114]

[0115] The larger the remanence (Br) and knee coercive force (Hk), the better the magnetic field retention and anti-demagnetization ability of the permanent magnet material, while the smaller the remanence temperature coefficient and high and low temperature impact flux change rate, indicating that the performance of the magnet under different temperature conditions is more stable.

[0116] As shown in Table 1, Examples 1 to 3 use the dual alloy composite of the present invention, and the alloy composition and content meet the requirements of the present invention. The prepared permanent magnetic materials show excellent comprehensive magnetic properties, high use temperature and low reversible temperature coefficient, large remanence (Br) and knee point coercivity (Hk), small remanence temperature coefficient and high and low temperature impact flux change rate; and the preparation process does not need to control the oxygen content. The comprehensive magnetic properties of the permanent magnetic materials of Comparative Examples 1 to 4 are worse than those of Examples 1 to 3, and the specific situation is as follows:

[0117] Compared with Example 1, Comparative Example 1 uses only alloy A, resulting in a lower Sm element content in the permanent magnetic material and a higher Fe / Co element ratio. The remanence of the obtained permanent magnetic material decreases, the knee coercive force Hk decreases more, and the anti-demagnetization ability decreases significantly.

[0118] Comparative Example 2 Compared with Example 1, the use ratio of A alloy is 40%, resulting in a lower content of Gd element in the permanent magnetic material, which increases the temperature coefficient of residual magnetism Br, and the obtained permanent magnetic material has poor temperature resistance, and its high and low temperature impact magnetic flux change rate is significantly increased;

[0119] Comparative Example 3 Compared with Example 1, the particle size of the magnetic powders of alloys A and B is larger, the density of the magnet blank obtained after pressing is low, and there are pores in the magnet blank, which reduces the remanence (Br) and knee coercive force (Hk) of the magnet;

[0120] Compared with Example 1, in Comparative Example 4, no pre-sintering was performed during the heat treatment, so that the densification effect after sintering was slightly worse, and the remanence (Br) and knee coercive force (Hk) were reduced.

[0121] In summary, the present invention adopts a composition design of high rare earth / cobalt element composite addition and combines process control to prepare a permanent magnetic material with high comprehensive magnetic properties, high temperature resistance and magnetic stability. The remanence Br is greater than 8.7 kGs at room temperature of 20°C, the knee coercive force Hk is greater than 16 KOe, and the remanence Br temperature coefficient is 0.015-0.025% / °C in the temperature range of 20-300°C.

[0122] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A rare earth cobalt permanent magnet material with high temperature stability, characterized in that: It is prepared by compounding A alloy and B alloy in a mass ratio, wherein the mass of A alloy accounts for 50% to 80%; the A alloy includes 2 to 4 rare earth elements, wherein the content of Gd element in the rare earth elements is not less than 50%; the B alloy includes 2 to 4 rare earth elements, wherein the content of Sm element in the rare earth elements is not less than 80%.

2. The permanent magnetic material according to claim 1, characterized in that: The chemical composition of the alloy A is (Gd a Dy b Er c Sm 1-a-b-c ) x Co y Cu z Zr w Fe 100-x-y-z-w , wherein the rare earth element composition ratio is: a=0.1~0.6, b=0~0.2, c=0~0.1, and the mass percentage is: x=22~25, y=45~50, z=6~11, and w=2~5.

3. The permanent magnetic material according to claim 1, characterized in that: The chemical composition of the B alloy is (Gd a Dy b Er c Sm 1-a-b-c ) x Co y Cu z Zr w Fe 100-x-y-z-w , wherein the rare earth element composition ratio is: a=0.1~0.6, b=0~0.2, c=0~0.1, and the mass percentage is: x=25~28, y=55~60, z=6~11, and w=2~5.

4. The permanent magnetic material according to claim 1, characterized in that: The performance of the high temperature stability permanent magnet material is that the remanence Br is greater than 8.7 kGs at room temperature 20°C, the knee point coercive force Hk is greater than 16 KOe, and the remanence Br temperature coefficient is 0.015-0.025% / °C in the temperature range of 20-300°C.

5. A method for preparing a rare earth cobalt permanent magnetic material with high temperature stability, characterized in that: The method for preparing the permanent magnetic material according to any one of claims 1 to 4 comprises the following steps: S1. Alloy smelting: The materials are prepared according to the designed proportion of alloy elements, and the raw materials are melted into alloy A ingot and alloy B ingot respectively in a high vacuum induction melting furnace, and the ingots are roughly crushed into coarse powder particles not larger than 1 mm; S2, ball milling: the A and B alloy coarse powder particles obtained in S1 are crushed by ball milling into A alloy fine magnetic powder and B alloy fine magnetic powder; S3, orientation pressing: the fine magnetic powder of alloy A and the fine magnetic powder of alloy B obtained in S2 are fully mixed according to a composite ratio and then oriented pressed to obtain a magnet blank; S4. Heat treatment: The magnet blank prepared in S3 is subjected to densification sintering and tempering heat treatment under vacuum conditions to obtain a permanent magnet material product.

6. The preparation method according to claim 5, characterized in that: The particle size of fine magnetic powder of alloy A in S2 is 4.5-6.0 μm, and the particle size of fine magnetic powder of alloy B is 2.5-4.0 μm.

7. The preparation method according to claim 5, characterized in that: The density of the magnet blank in S3 is 4.5-6.0 g / cm 3 .

8. The preparation method according to claim 5, characterized in that: The densification sintering process described in S4 is as follows: the magnet blank is degassed at a high vacuum temperature below 500°C, heated to 1190-1210°C for pre-sintering for 30-50 minutes, then heated to 1220-1230°C for densification sintering, sintered at a heat preservation time of 40-70 minutes, and then high-purity argon is introduced to rapidly cool the temperature to 1170-1200°C for solution treatment for 1-3 hours.

9. The preparation method according to claim 5, characterized in that: The tempering heat treatment in S4 is: cooling to 820-870°C and keeping the temperature for 15-25h, and then slowly cooling to room temperature.

10. The preparation method according to claim 9, characterized in that: The cooling rate of the gradient slow cooling to room temperature in S4 is: the cooling rate in the high temperature section is 0.7-0.9°C / min, and the cooling rate below 500°C is not less than 1.5°C / min.

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