CN115274239A - Method for improving temperature coefficient of rare earth cobalt-based permanent magnet - Google Patents

Method for improving temperature coefficient of rare earth cobalt-based permanent magnet Download PDF

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CN115274239A
CN115274239A CN202210829133.4A CN202210829133A CN115274239A CN 115274239 A CN115274239 A CN 115274239A CN 202210829133 A CN202210829133 A CN 202210829133A CN 115274239 A CN115274239 A CN 115274239A
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alloy
permanent magnet
rare earth
magnet
temperature coefficient
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方以坤
王超
李卫
李强锋
肖逸菲
王磊
郑蒙
朱明刚
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Central Iron and Steel Research Institute
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    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
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    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
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    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
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    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
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    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
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    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
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    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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Abstract

The invention discloses a method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet, which comprises the following steps: alloy ingot casting,Crushing, powder preparing, powder mixing, orientation molding, sintering and tempering; in the alloy ingot casting step, two alloy raw materials, sm (Co) are prepared according to the following chemical formula1‑a‑b‑cCuaFebZrc)zAnd R (Co)1‑a‑b‑ cCuaFebZrc)zWherein R is Gd or a combination element of Gd and one or two or more elements of Tb, dy, ho, er, tm and Lu; a is 0.06-0.12, b is 0.05-0.25, c is. The invention optimizes the ordering process and the heat treatment process of the magnet by adjusting the ordering process of the magnet, so that the density of the flaky phase of the magnet is between 0 and 0.04nm‑1Is adjustable. By controlling the density of flaky phases in the magnet, the distribution width and the average concentration of Cu elements in the cell wall phase of the permanent magnet are further influenced to change within the ranges of 10-30 nm and 10-30 at%, the temperature coefficient of the coercive force of the rare earth cobalt-based permanent magnet is regulated, the magnets with different temperature stabilities are obtained, and the stable application of the magnets in different temperature intervals is met.

Description

Method for improving temperature coefficient of rare earth cobalt-based permanent magnet
Technical Field
The invention relates to the technical field of permanent magnet materials, in particular to a method for improving a temperature coefficient of a rare earth cobalt-based permanent magnet by regulating lamellar phase density.
Technical Field
The samarium cobalt magnet is obviously superior to other permanent magnet materials in the aspect of high temperature, so that the samarium cobalt magnet can be applied to a working environment of more than 500 ℃, becomes a first choice of a high-temperature resistant permanent magnet material, and plays an indispensable role in applications such as high-grade new energy automobiles, special industrial robots, electronic information, aerospace, high-end equipment manufacturing and the like. Therefore, the development of the high-performance samarium-cobalt magnet for the wide temperature range has important significance.
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 document [ Hadjipinayis G C, IEEE Transactions on Magnetics,2000,36 (5): 3382-3387 ] reports that positive coercivity temperature coefficient can be obtained for samarium cobalt magnet in certain temperature interval by reducing Cu content; the document [ Xiong X Y, acta materialia.2004,52 (3): 737-748 ] reports that the temperature coefficient of positive coercivity can be obtained also in a certain temperature range by controlling the cooling temperature in the slow cooling process. Although these two approaches result in samarium cobalt magnets having a positive temperature coefficient of coercivity, they are impractical because the coercivity is too low. Therefore, how to improve the mode of greatly sacrificing room-temperature coercivity to replace temperature stability is the key for preparing the permanent magnet with wide-temperature-range and high-temperature stability.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to provide a method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet, wherein the temperature coefficient of the permanent magnet is improved by regulating and controlling the density of flaky phases, and the obtained magnet not only has high coercive force at room temperature, but also has low coercive force temperature coefficient.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet comprises the following steps:
(1) Alloy ingot casting: a first alloy raw material and a second alloy raw material are prepared according to the following chemical formula, wherein the component of the first alloy raw material is Sm (Co)1-a-b-cCuaFebZrc)zThe second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zWherein R is Gd or a combined element of Gd and one or two or more elements of Tb, dy, ho, er, tm and Lu, and the Gd content accounts for not less than 50 percent of the mass fraction of the combined elements; a is 0.06-0.12, b is 0.05-0.25, c is;
respectively smelting and pouring the prepared alloy raw materials to obtain mother alloy ingots of the first alloy and the second alloy;
(2) Crushing and preparing powder: the mother alloy cast ingot is coarsely crushed and airflow-crushed to the average particle size of 2.5-4.5 mu m to obtain a first alloy Sm (Co)1-a-b-cCuaFebZrc)zAnd a second alloy R (Co)1-a-b-cCuaFebZrc)zTwo kinds of alloy powder;
(3) Mixing powder: weighing the two alloy powders respectively according to the following mass percentages, and fully mixing the two alloy powders in a mixer: 60-80% of first alloy powder and the balance of second alloy;
(4) Orientation molding: under the protection of inert gas, the mixed magnetic powder is oriented and molded in a magnetic field with the magnetic field intensity of 1.5-2.3T, and then cold isostatic pressing is carried out to obtain a magnet green body;
(5) And (3) sintering: sintering the magnet green body at 1200-1235 ℃ for 1.0-2.5 h, and then carrying out solid solution treatment at 1165-1215 ℃ for 2-10 h to obtain a sintered magnet;
(6) Tempering: tempering the sintered magnet, wherein the tempering process is 790-870 ℃, the temperature is kept for 0.5-5 h, and then the sintered magnet is cooled to 300-400 ℃ at the cooling rate of 0.5-2 ℃/min to obtain a final magnet;
the method improves the temperature coefficient of the permanent magnet by regulating and controlling the density of the flaky phase.
In the step (1), the first alloy raw material Sm (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, sm: 22.8-27.8%, fe:3.3% -18.2%, cu:4.6% -9.8%, zr:2.2 to 4.7 percent, and the balance of Co;
the second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, R: 22.8-27.8%, fe:3.3% -18.2%, cu:4.6% -9.8%, zr:2.2 to 4.7 percent, and the balance of Co;
the mass percentage content of the combined element R is 2-20%.
In the step (1), raw materials are uniformly smelted by adopting an electric arc smelting or micro-positive pressure induction smelting furnace or a rapid hardening ingot casting process to obtain a first alloy Sm (Co)1-a-b-cCuaFebZrc)zAnd a second alloy R (Co)1-a-b-cCuaFebZrc)zThe master alloy of (1).
In the step (2), the first alloy Sm (Co) is firstly crushed by a machine1-a-b-cCuaFebZrc)zAnd a second alloy R (Co)1-a-b-cCuaFebZrc)zThe mother alloy is roughly crushed, and the oxygen concentration in the gas path of the process of powder preparation by airflow milling is 50-300 ppm.
In the step (4), the pressing pressure of the cold isostatic pressing is 200-260 MPa.
In the step (3), the coarse crushed powder is crushed to magnetic powder with the average particle size of 2.5-4.5 mu m by adopting a high-speed nitrogen jet mill, the mixing time is slightly 2 hours, and the pressure of filling high-purity argon is 0.01-0.05 MPa.
In the step (6), the temperature coefficient of the permanent magnet is improved by regulating and controlling the density of the flaky phase: the density of the flaky phase of the magnet is 0-0.04 nm-1Is adjustable.
In the step (6), the flaky phase density of the magnet is realized to be 0-0.04 nm-1The temperature coefficient of the coercive force of the rare earth-cobalt-based permanent magnet can be adjusted, so that the distribution width and the average concentration of the Cu element in the cell wall phase of the permanent magnet are respectively influenced to change within the ranges of 10-30 nm and 10-30 at%, and the adjustment and control of the temperature coefficient of the coercive force of the rare earth-cobalt-based permanent magnet are realized.
A rare earth cobalt-based permanent magnet having an improved temperature coefficient, which is prepared by the steps of: alloy ingot casting, crushing and powder making, powder mixing, orientation forming, sintering and tempering;
in the alloy ingot casting step, a first alloy material and a second alloy material are prepared according to the following chemical formula, wherein the component of the first alloy material is Sm (Co)1-a-b-cCuaFebZrc)zThe second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zWherein R is Gd or a combined element of Gd and one or two or more elements of Tb, dy, ho, er, tm and Lu, and the Gd content accounts for not less than 50 percent of the mass fraction of the combined elements; a is 0.06-0.12, b is 0.05-0.25, c is;
in the powder mixing step: weighing two alloy powders respectively according to the following mass percentages, and fully mixing the two alloy powders in a mixer: 60-80% of first alloy powder and the balance of second alloy;
the temperature coefficient of the final product of the permanent magnet is improved by regulating and controlling the density of flaky phases.
First alloy raw material Sm (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, sm: 22.8-27.8%, fe:3.3% -18.2%, cu:4.6% -9.8%, zr:2.2 to 4.7 percent, and the balance of Co;
the second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, R: 22.8-27.8%, fe:3.3% -18.2%, cu:4.6% -9.8%, zr:2.2 to 4.7 percent, and the balance of Co;
the mass percentage content of the combined element R is 2-20%.
The temperature coefficient of the final product of the permanent magnet is improved by regulating and controlling the density of flaky phases: the density of the flaky phase of the magnet is 0-0.04 nm-1Is adjustable.
By realizing the density of the flaky phase of the magnet between 0 and 0.04nm-1The temperature coefficient of the coercive force of the rare earth-cobalt-based permanent magnet can be adjusted, so that the distribution width and the average concentration of the Cu element in the cell wall phase of the permanent magnet are respectively influenced to change within the ranges of 10-30 nm and 10-30 at%, and the adjustment and control of the temperature coefficient of the coercive force of the rare earth-cobalt-based permanent magnet are realized.
The permanent magnet has the following combination of magnetic property and temperature coefficient under the using state:
remanence Br=8.7 ~ 9.4kGs magnetic energy product (BH)max= 18.4-21.5 MGOe, intrinsic coercivity Hcj＝9.2～25.3kOe；
The coercive force temperature coefficient from room temperature to 500 ℃ is-0.050 to-0.170%/DEG C.
Compared with the prior art, the invention has the beneficial effects that:
1. through adopting the mode that two kinds of alloy powder mix can avoid batching many times, can obtain the alloy composition that can satisfy different temperature stability demands through batching once.
2. According to the method for improving the temperature coefficient of the rare earth cobalt-based permanent magnet by regulating the lamellar phase density, the rare earth cobalt-based permanent magnet with different lamellar phase densities is obtained by adding heavy rare earth and optimizing a heat treatment process, and the regulation and control of the distribution and concentration of a Cu element in a cell wall phase are realized.
3. The method is suitable for industrial application, overcomes the problem that the room temperature magnetic property is greatly sacrificed to obtain the temperature stability in the traditional mode, and realizes the regulation and control of the coercive force temperature coefficient.
Drawings
FIG. 1 is a picture of the density of a lamellar phase of a rare earth cobalt-based permanent magnet produced in example 1 of the present invention;
FIG. 2 is a picture of the density of lamellar phases of a rare earth cobalt-based permanent magnet produced in example 2 of the present invention;
FIG. 3 is a photograph showing the density of lamellar phases of a rare earth cobalt-based permanent magnet produced in example 3 of the present invention;
FIG. 4 is a photograph showing the density of lamellar phases of a rare earth cobalt-based permanent magnet produced in example 4 of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
The basic principle of the invention is as follows: by introducing the heavy rare earth combination element R, the ordering speed of the magnet is regulated and controlled, and the effective regulation and control of the density of the flaky phase in the magnet are realized by combining the optimization of a heat treatment process. For the rare earth cobalt-based permanent magnet, the flaky phase is a diffusion channel of a Cu element, and the distribution and concentration of the Cu element in the cell wall phase of the magnet are changed by changing the density of the flaky phase in the magnet, so that the coercive force temperature coefficient of the magnet is optimized.
The rare earth cobalt-based permanent magnet consists of samarium, cobalt, iron, copper, zirconium and a combined element R, 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 Gd content accounts for not less than 50% of the combined element by mass.
A method for regulating lamellar phase density to improve the temperature coefficient of a rare earth cobalt-based permanent magnet comprises the following steps:
(1) Sm (Co) is prepared according to the following weight percentage1-a-b-cCuaFebZrc)zAlloy raw materials: sm: 22.8-27.8%, fe:3.3% -18.2%, cu:4.6% -9.8%, zr:2.2 to 4.7 percent of the total weight of the alloy, and the balance of Co, and the R (Co) is prepared according to the following weight percentage1-a-b-cCuaFebZrc)zAlloy raw materials: r: 22.8-27.8%, fe:3.3% -18.2%, cu: 4.6-9.8%, zr:2.2 to 4.7 percent of Co, and the balance of Co, wherein R is Gd or a combination element of Gd and one or two or more elements of Tb, dy, ho, er, tm and Lu;
the prepared raw materials are respectively prepared into two kinds of alloy powder by the following steps: smelting in a medium-frequency induction furnace, then casting in a double-sided water-cooling casting mold to prepare an alloy ingot, wherein argon is adopted for protection in the smelting process; then crushing the alloy ingot into alloy particles with the diameter of 0.5-2 mm by using a hammer crusher, and preventing the alloy particles from being oxidized by adopting nitrogen protection in the crushing process; preparing the alloy particles into alloy powder with the particle size of 2.5-4.5 microns by adopting an airflow milling powder preparation technology, wherein the narrower particle size distribution curve can be obtained by adopting the airflow milling technology to prepare the alloy powder, so that the magnet obtains higher magnetic property consistency;
(2) Respectively weighing the two alloy powders in the step (1) according to the proportion of 60-80% of the first alloy powder and the balance of the second alloy powder, fully mixing in a mixer to prepare mixed magnetic powder, and adopting high-purity nitrogen protection to prevent the powder from being oxidized in the mixing process;
(3) Weighing the mixed magnetic powder prepared in the step (2) in a glove box, then carrying out magnetic field orientation forming in a closed nitrogen atmosphere press, and then carrying out cold isostatic pressing to obtain a magnet green body;
(4) Sintering the magnet green body obtained in the step (3) at 1200-1235 ℃ for 1.0-2.5 h, and then carrying out solid solution treatment at 1165-1215 ℃ for 2-10 h to obtain a sintered magnet;
(5) Tempering the sintered magnet obtained in the step (4), wherein the tempering process is that the temperature is maintained at 790-870 ℃ for 0.5-5 h, and then the sintered magnet is cooled to 300-400 ℃ at the cooling rate of 0.5-2 ℃/min to obtain a final magnet;
usually, the sintered samarium cobalt magnet needs to be insulated for 12-24 hours at the temperature of 790-870 ℃ in the tempering stage, the ordering speed of the magnet in the tempering stage is delayed by doping the heavy rare earth combination element R, then the temperature preservation time of 790-870 ℃ is reduced, the density of flaky phases and the concentration and distribution of Cu elements in cell wall phases can be adjusted, and the regulation and control of the coercive force temperature coefficient of the magnet are realized on the basis of shortening the process flow.
Preferably, when the alloy powder is prepared by adopting the jet mill in the step (1), the oxygen concentration in a gas path of the jet mill is controlled to be 50-300 ppm. In order to ensure the proper oxygen content in the final magnet, the oxygen content in the gas path is strictly controlled when the alloy powder is prepared by jet milling.
Preferably, in the step (2), the mixing tank filled with the mixed magnetic powder needs to be filled with high-purity nitrogen as protective gas, and the mixing time is 2 hours.
Preferably, in the step (3), the cold isostatic pressing pressure is 200-260 MPa, so that the green body has a sufficiently high initial pressure density.
Preferably, in the step (4), the sintering and solid solution of the magnet are carried out under the protection of high-purity argon to reduce the volatilization of the rare earth element and ensure that the content of the rare earth element in the magnet is proper, and the pressure of filling the high-purity argon is 0.01-0.05 MPa.
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.
Example 1
(1) Preparing alloy powder according to the following weight percentageAlloy raw materials: sm (Co)balCu0.09Fe0.1Zr0.025)7.2Alloy: sm:26%, co:56.5%, fe:7%, cu:8%, zr:2.5%, (Gd)0.51Dy0.49)(CobalCu0.09Fe0.1Zr0.025)7.2Alloy: gd:13%, dy:13%, co:57.5%, fe:7%, cu:8%, zr:2.5 percent;
respectively smelting the prepared raw materials in a medium-frequency induction furnace, and then casting in a double-sided water-cooling casting mold to prepare an alloy ingot; crushing the alloy ingot into alloy particles with the diameter of 0.5mm by using a hammer crusher; the alloy particles are made into alloy powder with the average particle size within the range of 3.0 mu m by adopting a jet milling powder technology. Controlling the oxygen content of the gas circuit to be 100ppm in the powder making process of the airflow mill;
(2) Mixing the alloy powder obtained in the step (1) according to the following mass percentage: sm (Co)balCu0.09Fe0.1Zr0.025)7.2Alloy powder: 70%, (Gd)0.51Dy0.49)(CobalCu0.09Fe0.1Zr0.025)7.2Alloy powder: 30 percent, mixing for 2 hours to obtain mixed magnetic powder;
(3) Weighing the mixed alloy powder in a glove box, carrying out magnetic field orientation molding in a closed nitrogen atmosphere press, and then carrying out cold isostatic pressing at 220MPa to obtain a magnet green body;
(4) Sintering the green body at 1215 ℃ for 1.5h, and then carrying out solid solution treatment at the solid solution temperature of 1195 ℃ for 4h to obtain the sintered magnet. High-purity argon is filled in the process of sintering and solid solution of the magnet, and the pressure is 0.04MPa.
(5) Tempering the sintered magnet obtained in the step (4), preserving heat at 830 ℃ for 1h, and cooling to 400 ℃ at a cooling rate of 0.7 ℃/min to obtain a final magnet;
the magnetic properties of the sintered samarium cobalt magnet prepared according to example 1 were: remanence Br=8.9kGs magnetic energy product (BH)max=19.5MGOe, intrinsic coercive force Hcj=9.2kOe, cu element in cell wall phaseThe average concentration of the element is 12.7at%, the distribution width of Cu element in cell wall phase is 25nm, and the density of lamellar phase is 0.004nm-1And the coercive force temperature coefficient is-0.079%/DEG C at room temperature to 500 ℃.
Example 2
(1) Preparing alloy powder, namely preparing alloy raw materials in percentage by weight as follows: sm (Co)balCu0.1Fe0.15Zr0.025)7.2Alloy: sm:26%, co:53.5%, fe:10%, cu:9%, zr:2.5%, (Gd)0.51Dy0.49)(CobalCu0.1Fe0.15Zr0.025)7.2Alloy: gd:13% and Dy:13%, co:56%, fe:10%, cu:9%, zr:2.5 percent;
respectively smelting the prepared raw materials in a medium-frequency induction furnace, and then casting in a double-sided water-cooling casting mold to prepare an alloy ingot; then crushing the alloy cast ingot into alloy particles with the diameter of 0.5mm by using a hammer crusher; the alloy particles are made into alloy powder with the average particle size within the range of 3.0 mu m by adopting a jet milling powder-making technology. Controlling the oxygen content of a gas path to be 100ppm in the process of milling powder by airflow;
(2) Mixing the alloy powder obtained in the step (1) according to the following mass percentage: sm (Co)balCu0.1Fe0.15Zr0.025)7.2Alloy: 65%, (Gd)0.51Dy0.49)(CobalCu0.1Fe0.15Zr0.025)7.2Alloy powder: 35 percent, mixing the powder for 2 hours to obtain mixed magnetic powder;
(3) Weighing the mixed alloy powder in a glove box, carrying out magnetic field orientation molding in a closed nitrogen atmosphere press, and then carrying out cold isostatic pressing at 220MPa to obtain a magnet green body;
(4) And sintering the green body at 1215 ℃ for 1.5h, and then carrying out solid solution treatment at 1195 ℃ for 4h to obtain the sintered magnet. High-purity argon is filled in the process of sintering and solid solution of the magnet, and the pressure is 0.04MPa.
(5) Tempering the sintered magnet obtained in the step (4), preserving heat at 800 ℃ for 4h, and cooling to 400 ℃ at a cooling rate of 0.7 ℃/min to obtain a final magnet;
the magnetic properties of the sintered samarium cobalt magnet prepared according to example 2 were: remanence Br=8.8kGs magnetic energy product (BH)max=19.2MGOe, intrinsic coercivity Hcj=15.1kOe, the average concentration of Cu element in the cell wall phase was 19.5at%, the distribution width of Cu element in the cell wall phase was 20nm, and the density of lamellar phase was 0.019nm-1The coercive force temperature coefficient from room temperature to 500 ℃ is-0.112%/DEG C.
Example 3
(1) Preparing alloy powder, namely preparing alloy raw materials according to the following weight percentages: sm (Co)balCu0.09Fe0.2Zr0.03)7.4Alloy: sm:25%, co:50.5%, fe:14%, cu:7%, zr:3.5%, (Gd)0.6Dy0.40)(CobalCu0.09Fe0.2Zr0.03)7.4Alloy: gd:15%, dy:10%, co:50.5%, fe:14%, cu:7%, zr:3.5 percent;
respectively smelting the prepared raw materials in a medium-frequency induction furnace, and then casting in a double-sided water-cooling casting mold to prepare an alloy ingot; then crushing the alloy cast ingot into alloy particles with the diameter of 0.5mm by using a hammer crusher; the alloy particles are made into alloy powder with the average particle size within the range of 3.0 mu m by adopting a jet milling powder-making technology. Controlling the oxygen content of a gas path to be 100ppm in the process of milling powder by airflow;
(2) Mixing the alloy powder obtained in the step (1) according to the following mass percentage: sm (Co)balCu0.09Fe0.2Zr0.03)7.4Alloy powder: 80%, (Gd)0.6Dy0.40)(CobalCu0.09Fe0.2Zr0.03)7.4Alloy powder: 20 percent, mixing the powder for 2 hours to obtain mixed magnetic powder;
(3) Weighing the mixed alloy powder in a glove box, carrying out magnetic field orientation molding in a closed nitrogen atmosphere press, and then carrying out cold isostatic pressing at 220MPa to obtain a magnet green body;
(4) Sintering the green body at 1220 ℃ for 1h, and then carrying out solid solution treatment at the solid solution temperature of 1195 ℃ for 4h to obtain the sintered magnet. High-purity argon is filled in the magnet sintering solid solution process, and the pressure is 0.04MPa.
(5) Tempering the sintered magnet obtained in the step (4), preserving heat at 850 ℃ for 3h, and cooling to 400 ℃ at a cooling rate of 0.7 ℃/min to obtain a final magnet;
the magnetic properties of the sintered samarium cobalt magnet prepared according to example 3 were: remanence Br=9.4kGs, magnetic energy product (BH)max=21.5MGOe, intrinsic coercivity Hcj=24.4kOe, the average concentration of Cu element in the cell wall phase is 22.5at%, the distribution width of Cu element in the cell wall phase is 17nm, and the density of lamellar phase is 0.026nm-1And the coercive force temperature coefficient is-0.144%/DEG C at room temperature to 500 ℃.
Example 4
(1) Preparing alloy powder, namely preparing alloy raw materials according to the following weight percentages: sm (Co)balCu0.07Fe0.12Zr0.03)7.6Alloy: sm:24.5%, co:58%, fe:8.5%, cu:5.5%, zr:3.5%, (Gd)0.9Dy0.1)(CobalCu0.07Fe0.12Zr0.03)7.6Alloy: gd:22% and Dy:2.5%, co:58%, fe:8.5%, cu:5.5%, zr:3.5 percent;
respectively smelting the prepared raw materials in a medium-frequency induction furnace, and then casting in a double-sided water-cooling casting mold to prepare an alloy ingot; crushing the alloy ingot into alloy particles with the diameter of 0.5mm by using a hammer crusher; the alloy particles are made into alloy powder with the average particle size within the range of 3.0 mu m by adopting a jet milling powder technology. Controlling the oxygen content of a gas path to be 100ppm in the process of milling powder by airflow;
(2) Mixing the alloy powder obtained in the step (1) according to the following mass percentage: sm (Co)balCu0.07Fe0.12Zr0.03)7.6Alloy powder: 60%, (Gd)0.9Dy0.1)(CobalCu0.07Fe0.12Zr0.03)7.6Alloy powder: 40 percent, mixing for 2 hours to obtain mixed magnetic powder;
(3) Weighing the mixed alloy powder in a glove box, carrying out magnetic field orientation molding in a closed nitrogen atmosphere press, and then carrying out cold isostatic pressing at 220MPa to obtain a magnet green body;
(4) Sintering the green body at 1225 ℃ for 1h, and then carrying out solid solution treatment at a solid solution temperature of 1205 ℃ for 4h to obtain a sintered magnet. High-purity argon is filled in the process of sintering and solid solution of the magnet, and the pressure is 0.04MPa.
(5) Tempering the sintered magnet obtained in the step (4), preserving the heat at 830 ℃ for 4h, and cooling to 400 ℃ at a cooling rate of 0.7 ℃/min to obtain a final magnet;
the magnetic properties of the sintered samarium cobalt magnet prepared according to example 4 were: remanence Br=8.7kGs, magnetic energy product (BH)max=18.4MGOe, intrinsic coercivity Hcj=25.3kOe, the average concentration of Cu element in the cell wall phase was 25.5at%, the distribution width of Cu element in the cell wall phase was 14nm, and the lamellar phase density was 0.035nm-1And the coercive force temperature coefficient is-0.152%/DEG C at room temperature to 500 ℃.

Claims (12)

1. A method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet is characterized by comprising the following steps:
the preparation method of the rare earth cobalt-based permanent magnet comprises the following steps:
(1) Alloy ingot casting: a first alloy material and a second alloy material are prepared according to the following chemical formula, wherein the component of the first alloy material is Sm (Co)1-a-b-cCuaFebZrc)zThe second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zWherein R is Gd or a combined element of Gd and one or two or more elements of Tb, dy, ho, er, tm and Lu, and the Gd content accounts for not less than 50 percent of the mass fraction of the combined elements; a is 0.06-0.12, b is 0.05-0.25, c is;
respectively smelting and pouring the prepared alloy raw materials to obtain mother alloy ingots of the first alloy and the second alloy;
(2) Crushing and pulverizing: the mother alloy cast ingot is coarsely crushed and air-flow ground to the average grain size of 2.5-4.5 mu m to obtain a first alloy Sm (Co)1-a-b-cCuaFebZrc)zAnd a second alloy R (Co)1-a-b-cCuaFebZrc)zTwo kinds of alloy powder;
(3) Mixing powder: weighing the two alloy powders according to the following mass percentages, and fully mixing the two alloy powders in a mixer: 60-80% of first alloy powder, and the balance of second alloy;
(4) Orientation molding: under the protection of inert gas, the mixed magnetic powder is oriented and molded in a magnetic field with the magnetic field intensity of 1.5-2.3T, and then cold isostatic pressing is carried out to obtain a magnet green body;
(5) And (3) sintering: sintering the magnet green body at 1200-1235 ℃ for 1.0-2.5 h, and then carrying out solid solution treatment at 1165-1215 ℃ for 2-10 h to obtain a sintered magnet;
(6) Tempering: tempering the sintered magnet, wherein the tempering process is 790-870 ℃, the temperature is kept for 0.5-5 h, and then the sintered magnet is cooled to 300-400 ℃ at the cooling rate of 0.5-2 ℃/min to obtain a final magnet;
the method improves the temperature coefficient of the permanent magnet by regulating and controlling the density of the flaky phase.
2. The method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet according to claim 1, wherein:
in the step (1), the first alloy raw material Sm (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, sm: 22.8-27.8%, fe:3.3% -18.2%, cu: 4.6-9.8%, zr:2.2 to 4.7 percent of Co, and the balance of Co;
the second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, R: 22.8-27.8%, fe:3.3% -18.2%, cu: 4.6-9.8%, zr:2.2% > E4.7 percent, and the balance being Co;
the mass percentage content of the combined element R is 2-20%.
3. The method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet according to claim 1, wherein:
in the step (1), raw materials are uniformly smelted by adopting an electric arc smelting or micro-positive pressure induction smelting furnace or a rapid hardening ingot casting process to obtain a first alloy Sm (Co)1-a-b-cCuaFebZrc)zAnd a second alloy R (Co)1-a-b-cCuaFebZrc)zThe master alloy of (1).
4. The method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet according to claim 1, wherein:
in the step (2), the first alloy Sm (Co) is firstly crushed mechanically1-a-b-cCuaFebZrc)zAnd a second alloy R (Co)1-a-b- cCuaFebZrc)zThe mother alloy is roughly crushed, and the oxygen concentration in the gas path of the powder process by the airflow milling is 50-300 ppm.
5. The method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet according to claim 1, wherein:
in the step (4), the pressing pressure of the cold isostatic pressing is 200-260 MPa.
6. The method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet according to claim 1, wherein:
in the step (3), the coarse crushing powder is crushed to magnetic powder with the average particle size of 2.5-4.5 mu m by adopting a high-speed nitrogen jet mill, the mixing time is slightly 2h, and the pressure of filling high-purity argon is 0.01-0.05 MPa.
7. The method for improving the temperature coefficient of a rare earth cobalt-based permanent magnet according to claim 1, wherein:
in the step (6), the temperature coefficient of the permanent magnet is improved by regulating and controlling the density of the flaky phase: the density of the flaky phase of the magnet is 0-0.04 nm-1Is adjustable.
In the step (6), the flaky phase density of the magnet is realized to be 0-0.04 nm-1The distribution width and the average concentration of the Cu element in the cell wall phase of the permanent magnet are respectively influenced to change within the ranges of 10-30 nm and 10-30 at%, and the coercive force temperature coefficient of the rare earth cobalt-based permanent magnet is regulated and controlled.
8. A rare earth cobalt-based permanent magnet having an improved temperature coefficient, characterized in that:
the rare earth cobalt-based permanent magnet is prepared by the following steps: alloy ingot casting, crushing and pulverizing, powder mixing, orientation forming, sintering and tempering;
in the alloy ingot casting step, a first alloy material and a second alloy material are prepared according to the following chemical formula, wherein the component of the first alloy material is Sm (Co)1-a-b-cCuaFebZrc)zThe second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zWherein R is Gd or a combined element of Gd and one or two or more elements of Tb, dy, ho, er, tm and Lu, and the Gd content accounts for not less than 50 percent of the mass fraction of the combined elements; a is 0.06-0.12, b is 0.05-0.25, c is;
in the powder mixing step: weighing two alloy powders respectively according to the following mass percentages, and fully mixing the two alloy powders in a mixer: 60-80% of first alloy powder, and the balance of second alloy;
the temperature coefficient of the final product of the permanent magnet is improved by regulating and controlling the density of flaky phases.
9. The rare earth cobalt-based permanent magnet according to claim 8, wherein:
first alloy raw material Sm (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, sm: 22.8-27.8%, fe:3.3% -18.2% of Cu:4.6% -9.8%, zr:2.2 to 4.7 percent, and the balance of Co;
the second alloy raw material component is R (Co)1-a-b-cCuaFebZrc)zAccording to the mass percentage, R: 22.8-27.8%, fe:3.3% -18.2%, cu: 4.6-9.8%, zr:2.2 to 4.7 percent, and the balance of Co;
the mass percentage content of the combined element R is 2-20%.
10. The rare earth cobalt-based permanent magnet according to claim 8, wherein: the temperature coefficient of the final permanent magnet product is improved by regulating and controlling the density of flaky phases: the density of the flaky phase of the magnet is 0-0.04 nm-1Is adjustable.
11. The rare earth cobalt-based permanent magnet according to claim 8, wherein:
by realizing the density of the flaky phase of the magnet between 0 and 0.04nm-1The distribution width and the average concentration of the Cu element in the cell wall phase of the permanent magnet are respectively influenced to change within the ranges of 10-30 nm and 10-30 at%, and the coercive force temperature coefficient of the rare earth cobalt-based permanent magnet is regulated and controlled.
12. The rare earth cobalt-based permanent magnet according to claim 8, wherein: the permanent magnet has the following combination of magnetic property and temperature coefficient under the using state:
remanence Br=8.7 ~ 9.4kGs magnetic energy product (BH)max= 18.4-21.5 MGOe, intrinsic coercivity Hcj＝9.2～25.3kOe；
The coercive force temperature coefficient from room temperature to 500 ℃ is-0.050 to-0.170%/DEG C.
CN202210829133.4A 2022-06-24 2022-06-24 Method for improving temperature coefficient of rare earth cobalt-based permanent magnet Pending CN115274239A (en)

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