A method for improving the temperature coefficient of rare earth cobalt-based permanent magnets

Abstract

The present invention discloses a method for improving the temperature coefficient of rare earth cobalt-based permanent magnets. The permanent magnets are prepared through the following steps: alloy ingot casting, crushing and powder making, powder mixing, orientation forming, sintering, and tempering; in the alloy ingot casting step, two alloy raw materials are configured according to the following chemical formula, Sm(Co 1‑a‑b‑c Cu a Fe b Zr c ) z and R(Co 1‑a‑b‑ c Cu a Fe b Zr c ) z , where R is Gd or a combined element of Gd and one or two or more elements among Tb, Dy, Ho, Er, Tm, and Lu; a: 0.06 to 0.12, b: 0.05 to 0.25, c: 0.02 to 0.04, z: 6.5 to 8.0. The present invention adjusts the ordering process of the magnet and optimizes the heat treatment process, so that the lamellar phase density of the magnet is adjustable within 0 to 0.04 nm ‑1 . By controlling the lamellar phase density in the magnet, the distribution width and average concentration of Cu elements in the cell wall phase of the permanent magnet are respectively changed within the ranges of 10 to 30 nm and 10 to 30 at%, realizing the regulation of the coercivity temperature coefficient of the rare earth cobalt-based permanent magnet, obtaining magnets with different temperature stabilities, and meeting the stable application of the magnets in different temperature ranges.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnetic materials, and in particular to a method for regulating the density of a lamellar phase to improve the temperature coefficient of a rare earth cobalt-based permanent magnet. Technical Background

[0002] Samarium cobalt magnets are significantly superior to other permanent magnet materials in terms of high temperature resistance, so they can be used in working environments above 500°C, becoming the first choice for high temperature resistant permanent magnet materials. They play an indispensable role in applications such as high-end new energy vehicles, special industrial robots, electronic information, aerospace, and high-end equipment manufacturing. Therefore, it is of great significance to develop high-performance samarium cobalt magnets for a wide temperature range.

[0003] By optimizing the content of Sm, Cu and other elements in the samarium cobalt magnet, adjusting the heat treatment process, and optimizing the distribution of the Cu element in the cell wall phase, better temperature stability can be obtained. The literature [Hadjipanayis GC, IEEE Transactions on Magnetics, 2000, 36 (5): 3382-3387] reported that by reducing the Cu content, the samarium cobalt magnet can obtain a positive coercive force temperature coefficient in a certain temperature range; the literature [Xiong XY, Acta Materialia. 2004, 52 (3): 737-748] reported that by controlling the cooling temperature of the slow cooling process, the magnet can also obtain a positive coercive force temperature coefficient in a certain temperature range. Although these two methods have obtained samarium cobalt magnets with positive coercive force temperature coefficients, they are not practical because the coercive force is too low. Therefore, how to improve this method of sacrificing room temperature coercive force in exchange for temperature stability is the key to preparing permanent magnets with high temperature stability in a wide temperature range. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to propose a method for improving the temperature coefficient of rare earth cobalt-based permanent magnets. The temperature coefficient of the permanent magnet is improved by regulating the density of the lamellar phase. The obtained magnet not only has a high coercive force at room temperature, but also has a low coercive force temperature coefficient.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet, wherein the method for preparing the rare earth cobalt-based permanent magnet comprises the following steps:

[0007] (1) Alloy ingot: The first alloy raw material and the second alloy raw material are configured according to the following chemical formula. The first alloy raw material is composed of Sm(Co 1-a-b-c Cu a Fe b Zr c )z The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z , wherein R is Gd or a combination of Gd and one or two or more of Tb, Dy, Ho, Er, Tm, and Lu, and the mass fraction of Gd in the combination element is not less than 50%; a: 0.06-0.12, b: 0.05-0.25, c: 0.02-0.04, z: 6.5-8.0;

[0008] The prepared alloy raw materials are melted and cast respectively to obtain mother alloy ingots of the first alloy and the second alloy;

[0009] (2) Crushing and Powdering: The master alloy ingot is crushed by coarse crushing and jet milling to an average particle size of 2.5 to 4.5 μm to obtain the first alloy Sm(Co 1-a-b-c Cu a Fe b Zr c ) z and the second alloy R(Co 1-a-b-c Cu a Fe b Zr c ) z Two alloy powders;

[0010] (3) Powder mixing: Weigh the two alloy powders mentioned above according to the following mass percentages, and mix the two alloy powders in a mixer: 60-80% of the first alloy powder and the rest of the second alloy powder;

[0011] (4) Orientation molding: Under the protection of inert gas, the mixed magnetic powder is oriented in a magnetic field with a magnetic field strength of 1.5 to 2.3 T, and then cold isostatic pressing is performed to obtain a magnet green body;

[0012] (5) Sintering: Sintering the magnet green body at 1200-1235°C for 1.0-2.5 h, and then performing a solid solution treatment at a solid solution temperature of 1165-1215°C for 2-10 h to obtain a sintered magnet;

[0013] (6) Tempering: The sintered magnet is tempered at 790-870°C for 0.5-5h, and then cooled to 300-400°C at a cooling rate of 0.5-2°C / min to obtain a final magnet;

[0014] This method improves the temperature coefficient of the permanent magnet by regulating the density of the lamellar phase.

[0015] In step (1), the first alloy raw material Sm (Co1-a-b-c Cu a Fe b Zr c ) z By mass percentage, Sm: 22.8% to 27.8%, Fe: 3.3% to 18.2%, Cu: 4.6% to 9.8%, Zr: 2.2% to 4.7%, and the balance is Co;

[0016] The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, R: 22.8% to 27.8%, Fe: 3.3% to 18.2%, Cu: 4.6% to 9.8%, Zr: 2.2% to 4.7%, and the balance is Co;

[0017] The mass percentage content of the combined element R is 2% to 20%.

[0018] In step (1), arc melting or slightly positive pressure induction melting furnace or rapid solidification ingot casting process is used to melt the raw materials uniformly to obtain the first alloy Sm (Co 1-a-b-c Cu a Fe b Zr c ) z and the second alloy R(Co 1-a-b-c Cu a Fe b Zr c ) z of the master alloy.

[0019] In step (2), the first alloy Sm(Co 1-a-b-c Cu a Fe b Zr c ) z and the second alloy R(Co 1-a-b-c Cu a Fe b Zr c ) z The master alloy is coarsely crushed, and the oxygen concentration in the air path of the air flow grinding process is 50-300ppm.

[0020] In step (4), the pressing pressure of the cold isostatic pressing is 200 to 260 MPa.

[0021] In step (3), a high-speed nitrogen gas jet mill is used to crush the coarsely crushed powder into magnetic powder with an average particle size of 2.5 to 4.5 μm, the mixing time is less than 2 hours, and the pressure of the high-purity argon gas is 0.01 to 0.05 MPa.

[0022] In step (6), the temperature coefficient of the permanent magnet is improved by adjusting the density of the lamellar phase: the lamellar phase density of the magnet is adjusted to 0-0.04 nm. -1 Adjustable.

[0023] In step (6), by achieving a flaky phase density of the magnet in the range of 0 to 0.04 nm -1 The temperature coefficient of the coercive force of the rare earth cobalt-based permanent magnet can be adjusted, thereby affecting the distribution width and average concentration of the Cu element in the cell wall phase of the permanent magnet to change in the range of 10 to 30 nm and 10 to 30 at%, respectively.

[0024] A rare earth cobalt-based permanent magnet with improved temperature coefficient, the rare earth cobalt-based permanent magnet is prepared by the following steps: alloy ingot casting, crushing and powdering, powder mixing, orientation molding, sintering, and tempering;

[0025] In the alloy ingot casting step, the first alloy raw material and the second alloy raw material are configured according to the following chemical formula, wherein the first alloy raw material is composed of Sm(Co 1-a-b-c Cu a Fe b Zr c ) z The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z , wherein R is Gd or a combination of Gd and one or two or more of Tb, Dy, Ho, Er, Tm, and Lu, and the mass fraction of Gd in the combination element is not less than 50%; a: 0.06-0.12, b: 0.05-0.25, c: 0.02-0.04, z: 6.5-8.0;

[0026] In the powder mixing step: two alloy powders are weighed according to the following mass percentages, and the two alloy powders are fully mixed in a mixer: 60-80% of the first alloy powder and the rest of the second alloy;

[0027] The temperature coefficient of the final permanent magnet product is improved by adjusting the density of the lamellar phase.

[0028] The first alloy raw material Sm (Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, Sm: 22.8% to 27.8%, Fe: 3.3% to 18.2%, Cu: 4.6% to 9.8%, Zr: 2.2% to 4.7%, and the balance is Co;

[0029] The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, R: 22.8% to 27.8%, Fe: 3.3% to 18.2%, Cu: 4.6% to 9.8%, Zr: 2.2% to 4.7%, and the balance is Co;

[0030] The mass percentage content of the combined element R is 2% to 20%.

[0031] The temperature coefficient of the final permanent magnet product is improved by adjusting the density of the lamellar phase: the lamellar phase density of the magnet is kept between 0 and 0.04 nm. -1 Adjustable.

[0032] By achieving a magnet with a lamellar phase density of 0 to 0.04 nm -1 The temperature coefficient of the coercive force of the rare earth cobalt-based permanent magnet can be adjusted, thereby affecting the distribution width and average concentration of the Cu element in the cell wall phase of the permanent magnet to change in the range of 10 to 30 nm and 10 to 30 at%, respectively.

[0033] The permanent magnet has the following combination of magnetic properties and temperature coefficients when in use:

[0034] Remanence B r =8.7~9.4kGs, magnetic energy product (BH) max =18.4~21.5MGOe, intrinsic coercivity H cj =9.2~25.3kOe;

[0035] The coercive force temperature coefficient from room temperature to 500°C is -0.050 to -0.170% / °C.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. By mixing two alloy powders, multiple batching can be avoided, and an alloy composition that can meet different temperature stability requirements can be obtained through one batching.

[0038] 2. A method of regulating the lamellar phase density to improve the temperature coefficient of rare earth cobalt-based permanent magnets in the present invention obtains rare earth cobalt-based permanent magnets with different lamellar phase densities by adding heavy rare earth and optimizing the heat treatment process, thereby achieving the regulation of the distribution and concentration of the Cu element in the cell wall phase.

[0039] 3. This method is suitable for industrial application. It overcomes the problem of traditional methods that greatly sacrifice room temperature magnetic properties in exchange for temperature stability, and realizes the regulation of coercive force temperature coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a picture of the flaky phase density of the rare earth cobalt-based permanent magnet prepared in Example 1 of the present invention;

[0041] Figure 2 is a picture of the flaky phase density of the rare earth cobalt-based permanent magnet prepared in Example 2 of the present invention;

[0042] Figure 3 is a picture of the flaky phase density of the rare earth cobalt-based permanent magnet prepared in Example 3 of the present invention;

[0043] Figure 4 This is a picture of the lamellar phase density of the rare earth cobalt-based permanent magnet prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0045] The basic principle of the present invention is to effectively control the density of the lamellar phase in the magnet by introducing the heavy rare earth combination element R, regulating the ordering speed of the magnet, and optimizing the heat treatment process. For rare earth cobalt-based permanent magnets, the lamellar phase is the diffusion channel of the Cu element. By changing the density of the lamellar phase in the magnet, the distribution and concentration of the Cu element in the cell wall phase of the magnet are changed, thereby optimizing the coercive force temperature coefficient of the magnet.

[0046] The rare earth cobalt-based permanent magnet is composed of samarium, cobalt, iron, copper, zirconium and a combination element R, wherein R is Gd or a combination of Gd and one or two or more elements of Tb, Dy, Ho, Er, Tm and Lu, wherein the mass fraction of Gd in the combination elements is not less than 50%.

[0047] A method for regulating the density of a lamellar phase to improve the temperature coefficient of a rare earth cobalt-based permanent magnet comprises the following steps:

[0048] (1) Sm(Co) was prepared according to the following weight percentages: 1-a-b-c Cu a Fe b Zr c ) z Alloy raw materials: Sm: 22.8% ~ 27.8%, Fe: 3.3% ~ 18.2%, Cu: 4.6% ~ 9.8%, Zr: 2.2% ~ 4.7%, the balance is Co, and R (Co) is configured according to the following weight percentages 1-a-b-c Cu a Fe b Zr c ) zAlloy raw materials: R: 22.8% to 27.8%, Fe: 3.3% to 18.2%, Cu: 4.6% to 9.8%, Zr: 2.2% to 4.7%, the balance is Co, wherein R is Gd or a combination of Gd and one or two or more of Tb, Dy, Ho, Er, Tm, and Lu;

[0049] The prepared raw materials are respectively used to prepare two kinds of alloy powders by the following steps: melting in a medium frequency induction furnace, then casting in a double-sided water-cooled mold to prepare an alloy ingot, and argon is used for protection during the melting process; the alloy ingot is then crushed into alloy particles of 0.5 to 2 mm by a hammer crusher, and nitrogen is used for protection during the crushing process to prevent the alloy particles from oxidation; the alloy particles are made into alloy powder with a particle size of 2.5 to 4.5 μm by air flow milling technology. The use of air flow milling technology to prepare alloy powder can obtain a narrower particle size distribution curve, so that the magnet obtains higher magnetic property consistency;

[0050] (2) Weighing the two alloy powders in step (1) in a ratio of 60-80% of the first alloy powder and the rest of the second alloy powder, and mixing them thoroughly in a mixer to obtain mixed magnetic powder. During the mixing process, high-purity nitrogen is used to protect the powder from oxidation;

[0051] (3) weighing the mixed magnetic powder obtained in step (2) in a glove box, then subjecting it to magnetic field orientation molding in a closed nitrogen atmosphere press, and then cold isostatic pressing to obtain a magnet green body;

[0052] (4) sintering the magnet green body obtained in step (3) at 1200-1235° C. for 1.0-2.5 h, and then performing a solid solution treatment at a solid solution temperature of 1165-1215° C. for 2-10 h to obtain a sintered magnet;

[0053] (5) tempering the sintered magnet obtained in step (4), wherein the tempering process comprises maintaining the temperature at 790-870° C. for 0.5-5 h, and then cooling the magnet to 300-400° C. at a cooling rate of 0.5-2° C. / min to obtain a final magnet;

[0054] Usually, sintered samarium cobalt magnets need to be kept at 790-870°C for 12-24 hours during the tempering stage. In the present invention, the ordering speed of the magnet during the tempering stage is delayed by adding the heavy rare earth composite element R, and then the density of the lamellar phase and the concentration and distribution of the Cu element in the cell wall phase can be adjusted by reducing the holding time at 790-870°C. On the basis of shortening the process flow, the temperature coefficient of the coercive force of the magnet is also regulated.

[0055] Preferably, when the alloy powder is prepared by jet milling in step (1), the oxygen concentration in the air path of the jet mill is controlled at 50-300 ppm. In order to ensure that the final magnet has a suitable oxygen content, the oxygen content in the air path must be strictly controlled when the alloy powder is prepared by jet milling.

[0056] Preferably, in step (2), the mixing tank containing the mixed magnetic powder needs to be filled with high-purity nitrogen as a protective gas, and the mixing time is 2 hours.

[0057] Preferably, in step (3), the pressing pressure of the cold isostatic pressing is 200-260 MPa to ensure that the green body has a sufficiently high initial pressing density.

[0058] Preferably, in step (4), the sintering and solid solution of the magnet need to be carried out under the protection of high-purity argon gas to reduce the volatilization of rare earth elements and ensure that the rare earth element content in the magnet is appropriate. The pressure of the high-purity argon gas is 0.01-0.05 MPa.

[0059] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0060] Example 1

[0061] (1) Preparation of alloy powder: Alloy raw materials are prepared according to the following weight percentages: Sm(Co bal Cu 0.09 Fe 0.1 Zr 0.025 ) 7.2 Alloy: Sm: 26%, Co: 56.5%, Fe: 7%, Cu: 8%, Zr: 2.5%, (Gd 0.51 Dy 0.49 )(Co bal Cu 0.09 Fe 0.1 Zr 0.025 ) 7.2 Alloy: Gd: 13%, Dy: 13%, Co: 57.5%, Fe: 7%, Cu: 8%, Zr: 2.5%;

[0062] The prepared raw materials are melted in a medium frequency induction furnace, and then cast in a double-sided water-cooled mold to prepare alloy ingots; the alloy ingots are then crushed into 0.5mm alloy particles using a hammer crusher; the alloy particles are made into alloy powder with an average particle size of 3.0μm using airflow grinding technology. During the airflow grinding process, the oxygen content of the gas path is controlled at 100ppm;

[0063] (2) The alloy powder obtained in step (1) is mixed according to the following mass percentages: Sm(Cobal Cu 0.09 Fe 0.1 Zr 0.025 ) 7.2 Alloy powder: 70%, (Gd 0.51 Dy 0.49 )(Co bal Cu 0.09 Fe 0.1 Zr 0.025 ) 7.2 Alloy powder: 30%, mixing time 2h, to obtain mixed magnetic powder;

[0064] (3) The mixed alloy powder is weighed in a glove box, formed by magnetic field orientation in a closed nitrogen atmosphere press, and then subjected to cold isostatic pressing at 220 MPa to obtain a magnet green body;

[0065] (4) The green body is sintered at 1215°C for 1.5 hours, and then subjected to solution treatment at a temperature of 1195°C for 4 hours to obtain a sintered magnet. During the sintering and solution treatment of the magnet, high-purity argon gas is filled at a pressure of 0.04 MPa.

[0066] (5) subjecting the sintered magnet obtained in step (4) to tempering treatment, maintaining the temperature at 830° C. for 1 h, and cooling the magnet to 400° C. at a cooling rate of 0.7° C. / min to obtain a final magnet;

[0067] The magnetic properties of the sintered samarium cobalt magnet prepared according to Example 1 are: remanence B r =8.9kGs, magnetic energy product (BH) max =19.5MGOe, intrinsic coercivity H cj =9.2kOe, the average concentration of Cu in the cell wall phase is 12.7at%, the distribution width of Cu in the cell wall phase is 25nm, and the density of the lamellar phase is 0.004nm -1 The coercive force temperature coefficient from room temperature to 500°C is -0.079% / °C.

[0068] Example 2

[0069] (1) Preparation of alloy powder: Alloy raw materials are prepared according to the following weight percentages: Sm(Co bal Cu 0.1 Fe 0.15 Zr 0.025 ) 7.2 Alloy: Sm: 26%, Co: 53.5%, Fe: 10%, Cu: 9%, Zr: 2.5%, (Gd 0.51 Dy 0.49 )(Co bal Cu 0.1 Fe 0.15Zr 0.025 ) 7.2 Alloy: Gd: 13%, Dy: 13%, Co: 56%, Fe: 10%, Cu: 9%, Zr: 2.5%;

[0070] The prepared raw materials are melted in a medium frequency induction furnace, and then cast in a double-sided water-cooled mold to prepare alloy ingots; the alloy ingots are then crushed into 0.5mm alloy particles using a hammer crusher; the alloy particles are made into alloy powder with an average particle size of 3.0μm using airflow grinding technology. During the airflow grinding process, the oxygen content of the gas path is controlled at 100ppm;

[0071] (2) The alloy powder obtained in step (1) is mixed according to the following mass percentages: Sm(Co bal Cu 0.1 Fe 0.15 Zr 0.025 ) 7.2 Alloy: 65%, (Gd 0.51 Dy 0.49 )(Co bal Cu 0.1 Fe 0.15 Zr 0.025 ) 7.2 Alloy powder: 35%, mixing time 2h, to obtain mixed magnetic powder;

[0072] (3) The mixed alloy powder is weighed in a glove box, formed by magnetic field orientation in a closed nitrogen atmosphere press, and then subjected to cold isostatic pressing at 220 MPa to obtain a magnet green body;

[0073] (4) The green body is sintered at 1215°C for 1.5 hours, and then subjected to solution treatment at a temperature of 1195°C for 4 hours to obtain a sintered magnet. During the sintering and solution treatment of the magnet, high-purity argon gas is filled at a pressure of 0.04 MPa.

[0074] (5) subjecting the sintered magnet obtained in step (4) to tempering treatment, maintaining the temperature at 800° C. for 4 h, and cooling the magnet to 400° C. at a cooling rate of 0.7° C. / min to obtain a final magnet;

[0075] The magnetic properties of the sintered samarium cobalt magnet prepared according to Example 2 are: remanence B r =8.8kGs, magnetic energy product (BH) max =19.2MGOe, intrinsic coercivity H cj =15.1kOe, the average concentration of Cu in the cell wall phase is 19.5at%, the distribution width of Cu in the cell wall phase is 20nm, and the density of the lamellar phase is 0.019nm -1The coercive force temperature coefficient from room temperature to 500°C is -0.112% / °C.

[0076] Example 3

[0077] (1) Preparation of alloy powder: Alloy raw materials are prepared according to the following weight percentages: Sm(Co bal Cu 0.09 Fe 0.2 Zr 0.03 ) 7.4 Alloy: Sm: 25%, Co: 50.5%, Fe: 14%, Cu: 7%, Zr: 3.5%, (Gd 0.6 Dy 0.40 )(Co bal Cu 0.09 Fe 0.2 Zr 0.03 ) 7.4 Alloy: Gd: 15%, Dy: 10%, Co: 50.5%, Fe: 14%, Cu: 7%, Zr: 3.5%;

[0078] The prepared raw materials are melted in a medium frequency induction furnace, and then cast in a double-sided water-cooled mold to prepare alloy ingots; the alloy ingots are then crushed into 0.5mm alloy particles using a hammer crusher; the alloy particles are made into alloy powder with an average particle size of 3.0μm using airflow grinding technology. During the airflow grinding process, the oxygen content of the gas path is controlled at 100ppm;

[0079] (2) The alloy powder obtained in step (1) is mixed according to the following mass percentages: Sm(Co bal Cu 0.09 Fe 0.2 Zr 0.03 ) 7.4 Alloy powder: 80%, (Gd 0.6 Dy 0.40 )(Co bal Cu 0.09 Fe 0.2 Zr 0.03 ) 7.4 Alloy powder: 20%, mixing time 2h, to obtain mixed magnetic powder;

[0080] (3) The mixed alloy powder is weighed in a glove box, formed by magnetic field orientation in a closed nitrogen atmosphere press, and then subjected to cold isostatic pressing at 220 MPa to obtain a magnet green body;

[0081] (4) The green body is sintered at 1220°C for 1 hour, and then subjected to solution treatment at a temperature of 1195°C for 4 hours to obtain a sintered magnet. During the sintering and solution treatment of the magnet, high-purity argon gas is filled at a pressure of 0.04 MPa.

[0082] (5) subjecting the sintered magnet obtained in step (4) to tempering treatment, maintaining the temperature at 850° C. for 3 h, and cooling the magnet to 400° C. at a cooling rate of 0.7° C. / min to obtain a final magnet;

[0083] The magnetic properties of the sintered samarium cobalt magnet prepared according to Example 3 are: remanence B r =9.4kGs, magnetic energy product (BH) max =21.5MGOe, intrinsic coercivity H cj =24.4kOe, the average concentration of Cu in the cell wall phase is 22.5at%, the distribution width of Cu in the cell wall phase is 17nm, and the density of the lamellar phase is 0.026nm -1 The coercive force temperature coefficient from room temperature to 500°C is -0.144% / °C.

[0084] Example 4

[0085] (1) Preparation of alloy powder: Alloy raw materials are prepared according to the following weight percentages: Sm(Co bal Cu 0.07 Fe 0.12 Zr 0.03 ) 7.6 Alloy: Sm: 24.5%, Co: 58%, Fe: 8.5%, Cu: 5.5%, Zr: 3.5%, (Gd 0.9 Dy 0.1 )(Co bal Cu 0.07 Fe 0.12 Zr 0.03 ) 7.6 Alloy: Gd: 22%, Dy: 2.5%, Co: 58%, Fe: 8.5%, Cu: 5.5%, Zr: 3.5%;

[0086] The prepared raw materials are melted in a medium frequency induction furnace, and then cast in a double-sided water-cooled mold to prepare alloy ingots; the alloy ingots are then crushed into 0.5mm alloy particles using a hammer crusher; the alloy particles are made into alloy powder with an average particle size of 3.0μm using airflow grinding technology. During the airflow grinding process, the oxygen content of the gas path is controlled at 100ppm;

[0087] (2) The alloy powder obtained in step (1) is mixed according to the following mass percentages: Sm(Co bal Cu0.07 Fe 0.12 Zr 0.03 ) 7.6 Alloy powder: 60%, (Gd 0.9 Dy 0.1 )(Co bal Cu 0.07 Fe 0.12 Zr 0.03 ) 7.6 Alloy powder: 40%, mixing time 2h, to obtain mixed magnetic powder;

[0088] (3) The mixed alloy powder is weighed in a glove box, formed by magnetic field orientation in a closed nitrogen atmosphere press, and then subjected to cold isostatic pressing at 220 MPa to obtain a magnet green body;

[0089] (4) The green body is sintered at 1225°C for 1 hour, and then subjected to solution treatment at a temperature of 1205°C for 4 hours to obtain a sintered magnet. During the sintering and solution treatment of the magnet, high-purity argon gas is filled at a pressure of 0.04 MPa.

[0090] (5) subjecting the sintered magnet obtained in step (4) to tempering treatment, maintaining the temperature at 830° C. for 4 h, and cooling the magnet to 400° C. at a cooling rate of 0.7° C. / min to obtain a final magnet;

[0091] The magnetic properties of the sintered samarium cobalt magnet prepared according to Example 4 are as follows: remanence B r =8.7kGs, magnetic energy product (BH) max =18.4MGOe, intrinsic coercivity H cj =25.3kOe, the average concentration of Cu in the cell wall phase is 25.5at%, the distribution width of Cu in the cell wall phase is 14nm, and the density of the lamellar phase is 0.035nm -1 The coercive force temperature coefficient from room temperature to 500°C is -0.152% / °C.

Claims

1. A method for improving the temperature coefficient of rare earth cobalt-based permanent magnets, characterized in that: The method for preparing the rare earth cobalt-based permanent magnet comprises the following steps: (1) Alloy ingot: The first alloy raw material and the second alloy raw material are configured according to the following chemical formula. The first alloy raw material is composed of Sm(Co 1-a-b-c Cu a Fe b Zr c ) z The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z , where R is Gd or a combination of Gd and one or two or more of Tb, Dy, Ho, Er, Tm, and Lu, and the mass fraction of Gd in the combination element is not less than 50%; a: 0.06-0.12, b: 0.05-0.25, c: 0.02-0.04, z: 6.5-8.0; The prepared alloy raw materials are melted and cast respectively to obtain mother alloy ingots of the first alloy and the second alloy; (2) Crushing and pulverizing: The master alloy ingot is coarsely crushed and jet-milled to an average particle size of 2.5 to 4.5 μm to obtain the first alloy Sm(Co 1-a-b-c Cu a Fe b Zr c ) z and the second alloy R(Co 1-a-b-c Cu a Fe b Zr c ) z Two alloy powders; (3) Mixing powders: Weigh the two alloy powders mentioned above according to the following mass percentages, and mix the two alloy powders thoroughly in a mixer: 60-80% of the first alloy powder and the rest of the second alloy powder; (4) Orientation molding: Under the protection of inert gas, the mixed magnetic powder is oriented in a magnetic field with a magnetic field strength of 1.5~2.3 T, and then cold isostatic pressing is performed to obtain a magnet green body; (5) Sintering: Sinter the magnet green body at 1200-1235 °C for 1.0-2.5 h, and then perform solid solution treatment at a solid solution temperature of 1165-1215 °C for 2-10 h to obtain a sintered magnet; (6) Tempering: The sintered magnet is tempered at 790-870 °C for 0.5-5 h, and then cooled to 300-400 °C at a cooling rate of 0.5-2 °C / min to obtain the final magnet; This method improves the temperature coefficient of the permanent magnet by adjusting the density of the lamellar phase: the lamellar phase density of the magnet is adjusted between 0 and 0.04 nm. -1 Adjustable; by achieving a magnet with a lamellar phase density between 0 and 0.04 nm -1 The distribution width and average concentration of the Cu element in the cell wall phase of the permanent magnet can be adjusted within the range of 10 to 30 nm and 10 to 30 at%, respectively, to achieve the regulation of the temperature coefficient of coercivity of the rare earth cobalt-based permanent magnet.

2. The method for improving the temperature coefficient of rare earth cobalt-based permanent magnets according to claim 1, characterized in that: In step (1), the first alloy raw material Sm(Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, Sm: 22.8% ~ 27.8%, Fe: 3.3% ~ 18.2%, Cu: 4.6% ~ 9.8%, Zr: 2.2% ~ 4.7%, and the balance is Co; The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, R: 22.8% ~ 27.8%, Fe: 3.3% ~ 18.2%, Cu: 4.6% ~ 9.8%, Zr: 2.2% ~ 4.7%, and the balance is Co; The mass percentage content of the combined element R is 2% to 20%.

3. The method for improving the temperature coefficient of rare earth cobalt-based permanent magnets according to claim 1, characterized in that: In step (1), arc melting or micro-positive pressure induction melting furnace or rapid solidification ingot casting process is used to melt the raw materials uniformly to obtain the first alloy Sm (Co 1-a-b-c Cu a Fe b Zr c ) z and the second alloy R(Co 1-a-b-c Cu a Fe b Zr c ) z of the master alloy.

4. The method for improving the temperature coefficient of rare earth cobalt-based permanent magnets according to claim 1, characterized in that: In step (2), the first alloy Sm(Co 1-a-b-c Cu a Fe b Zr c ) z and the second alloy R(Co 1-a-b- c Cu a Fe b Zr c ) z The master alloy is coarsely crushed, and the oxygen concentration in the air path of the air flow grinding process is 50 ~ 300 ppm.

5. The method for improving the temperature coefficient of rare earth cobalt-based permanent magnets according to claim 1, characterized in that: In step (4), the pressing pressure of the cold isostatic pressing is 200-260 MPa.

6. The method for improving the temperature coefficient of rare earth cobalt-based permanent magnets according to claim 1, characterized in that: In step (3), a high-speed nitrogen gas jet mill is used to grind the coarsely crushed powder into magnetic powder with an average particle size of 2.5 to 4.5 μm. The mixing time is 2 h, and the pressure of the high-purity argon gas is 0.01 to 0.05 MPa.

7. A rare earth cobalt-based permanent magnet with improved temperature coefficient, characterized in that: The rare earth cobalt-based permanent magnet is prepared by the following steps: alloy ingot casting, crushing and powdering, powder mixing, orientation molding, sintering, and tempering; In the alloy ingot casting step, the first alloy raw material and the second alloy raw material are configured according to the following chemical formula, wherein the first alloy raw material is composed of Sm(Co 1-a-b-c Cu a Fe b Zr c ) z The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z , where R is Gd or a combination of Gd and one or two or more of Tb, Dy, Ho, Er, Tm, and Lu, and the mass fraction of Gd in the combination element is not less than 50%; a: 0.06-0.12, b: 0.05-0.25, c: 0.02-0.04, z: 6.5-8.0; In the powder mixing step: two alloy powders are weighed according to the following mass percentages, and the two alloy powders are fully mixed in a mixer: 60-80% of the first alloy powder and the rest of the second alloy; The temperature coefficient of the final permanent magnet product is improved by adjusting the flake phase density as follows: by achieving a flake phase density of 0 ~ 0.04 nm -1 The distribution width and average concentration of the Cu element in the cell wall phase of the permanent magnet can be adjusted within the range of 10 to 30 nm and 10 to 30 at%, respectively, to achieve the regulation of the temperature coefficient of coercivity of the rare earth cobalt-based permanent magnet.

8. The rare earth cobalt-based permanent magnet according to claim 7, characterized in that: The first alloy raw material Sm (Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, Sm: 22.8% ~ 27.8%, Fe: 3.3% ~18.2%, Cu: 4.6% ~ 9.8%, Zr: 2.2% ~ 4.7%, and the balance is Co; The second alloy raw material composition is R(Co 1-a-b-c Cu a Fe b Zr c ) z By mass percentage, R: 22.8% ~ 27.8%, Fe: 3.3% ~ 18.2%, Cu: 4.6% ~ 9.8%, Zr: 2.2% ~ 4.7%, and the balance is Co; The mass percentage content of the combined element R is 2% to 20%.

9. The rare earth cobalt-based permanent magnet according to claim 7, characterized in that: The temperature coefficient of the final permanent magnet product is improved by adjusting the density of the lamellar phase: the lamellar phase density of the magnet is kept between 0 and 0.04 nm. -1 Adjustable.

10. The rare earth cobalt-based permanent magnet according to claim 7, characterized in that: The permanent magnet has the following combination of magnetic properties and temperature coefficients when in use: Remanence B r =8.7~9.4 kGs, magnetic energy product (BH) max =18.4~21.5MGOe, intrinsic coercivity H cj =9.2~25.3 kOe; The coercivity temperature coefficient from room temperature to 500°C is -0.050 ~ -0.170 % / °C.

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