CN111243804A - Rare earth permanent magnet with hydrogen resistance and preparation method thereof - Google Patents
Rare earth permanent magnet with hydrogen resistance and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—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
- 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
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/0555—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
- H01F1/0556—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together pressed
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—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
- 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
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/0555—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
- H01F1/0557—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together sintered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- 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
- 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
- H01F41/0266—Moulding; Pressing
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Abstract
The invention discloses a rare earth permanent magnet with hydrogen resistance and a preparation method thereof, belonging to the technical field of rare earth permanent magnet materials. The rare earth permanent magnet of the invention is Sm2(CoCuFeZr)17Magnet, wherein the mass percentage of Sm is m, the sum of the mass percentages of Co and Fe is n, n>3 m; the sealing layer outside the rare earth permanent magnet is formed by sealing a water-based silane solvent containing cerium, and the hydrogen resistance of the rare earth permanent magnet is improved through heat treatment. According to the invention, the sum of the mass percentages of Co and Fe is set to be larger than the mass percentage of Sm, and the surface of the rare earth permanent magnet is more densified and stabilized by combining a heat treatment method, so that the path of hydrogen atoms entering a crystal boundary from the surface of a material is reduced, and the hydrogen resistance of the rare earth permanent magnet is improved, so that the purpose of preventing the hydrogen from entering the magnet is achieved.
Description
Technical Field
The invention relates to the technical field of rare earth permanent magnet materials, in particular to a rare earth permanent magnet with hydrogen resistance.
Background
The rare earth permanent magnetic material is a permanent magnetic material with the highest comprehensive performance, has the magnetic performance which is more than 100 times higher than that of magnetic steel used in the nineties, is much better than that of ferrite and alnico, and has the magnetic performance which is one time higher than that of expensive platinum-cobalt alloy. Due to the use of rare earth permanent magnetic materials, the development of permanent magnetic devices towards miniaturization is promoted, the performance of products is improved, and certain special devices are promoted to be generated. The current major classes of magnetic permanent magnet materials include sintered and bonded rare earth permanent magnets. The rare earth permanent magnet material is an indispensable material for manufacturing a stator and a rotor of a modern motor and realizing miniaturization of a high-performance motor by virtue of high magnetic energy product and high coercive force of the rare earth permanent magnet material.
When the existing rare earth permanent magnet is contacted with hydrogen, hydrogen atoms can enter the rare earth permanent magnet material along a crystal boundary, so that the rare earth permanent magnet material is pulverized, the magnetic property is lost, and finally the motor fails. According to the invention, the surface modification and the sealing are carried out on the rare earth permanent magnet material, so that the motor made of the permanent magnet material can stably operate in an environment contacting with hydrogen.
The prior art also has patent applications for improving the performance of rare earth permanent magnetic materials, such as: the name of the invention is: the sintered samarium cobalt permanent magnet material with high performance and high resistivity, the preparation method and the application (application number: 201810074109.8, application date 2018.01.25) thereof utilize the permanent magnet characteristic of the main phase of the samarium cobalt matrix to realize the high magnetic performance of the magnet, and the resistivity of the magnet is improved by the wrapping of a grain boundary phase; in addition, the samarium cobalt permanent magnet material does not need to be compounded with a high-resistivity compound through a complex process, and the resistivity of the magnet is improved on the basis of not changing the process flow of sintering the samarium cobalt magnet. However, this technique does not improve the hydrogen resistance of rare earth permanent magnets.
In addition, the invention and creation names are also disclosed as follows: a method for preparing high-performance SmCo permanent magnet material (application No. 201210272726.1, application No. 2012.07.26) is characterized in that the permanent magnetic performance of a magnet is improved by improving the aging process and adding a constant magnetic field when the permanent magnet material is subjected to aging treatment. However, this method also fails to improve the hydrogen resistance of the rare earth permanent magnet.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to solve the problem that the traditional permanent magnet material is easy to lose efficacy when contacted with hydrogen in the prior art, and provides a rare earth permanent magnet with hydrogen resistance and a preparation method thereof, wherein the rare earth permanent magnet is Sm2(CoCuFeZr)17The sum of the mass percentages of the magnet, Co and Fe is more than 3 times of the mass percentage of Sm, so that the surface of the rare earth permanent magnet is more compact and stable, meanwhile, the path of hydrogen atoms entering a crystal boundary from the surface of the material can be reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the rare earth permanent magnet with hydrogen resistance is Sm2(CoCuFeZr)17Magnet, wherein the mass percentage of Sm is m, the sum of the mass percentages of Co and Fe is n, n>3m。
Preferably, the mass percent of Co is 45-55%, the mass percent of Fe is 18-20%, and the mass percent of Sm is 15-23%.
Preferably, the rare earth permanent magnet is externally provided with a sealing layer, and the sealing layer is formed by sealing a water-based silane solvent containing cerium.
Preferably, the mass percentage of Cu is 2-6%.
The invention also provides a preparation method of the hydrogen-resistant rare earth permanent magnet, which comprises the following steps:
(1) smelting: smelting in a smelting furnace to obtain Sm2(CoCuFeZr)17Magnet, wherein the mass percentage of Sm is m, the sum of the mass percentages of Co and Fe is n, n>3m, and obtaining an ingot;
(2) milling: crushing and pulverizing the cast ingot to obtain permanent magnet powder;
(3) compression molding: punching and forming the permanent magnet powder to obtain a permanent magnet green body;
(4) sintering treatment: sintering the permanent magnet green body at 1150-1250 ℃ for 3-5 hours to obtain a permanent magnet blank after sintering;
(5) and (3) heat treatment: and after sintering, cooling to room temperature, and then carrying out heat treatment on the permanent magnet blank in a nitrogen atmosphere, wherein the heat treatment temperature is 650-1050 ℃, and the heat treatment time is more than 12 hours.
Preferably, the process of heat treatment comprises three stages:
stage one: firstly, heating a rare earth permanent magnet to 650-750 ℃ under the vacuum condition, and carrying out heat preservation treatment for 2-3 h;
and a second stage: then heating to 750-850 ℃ at a heating rate of 1-5 ℃/min, filling nitrogen into the vacuum furnace, and carrying out heat preservation treatment for 2-3 h;
and a third stage: heating to 900-1050 ℃ at a heating rate of 1-5 ℃/min, and carrying out heat preservation treatment for 10-15 h.
Preferably, the rare earth permanent magnet is subjected to sealing treatment after the heat treatment, and the method comprises the following specific steps: and cooling the rare earth permanent magnet to room temperature, immersing the rare earth permanent magnet into a sealing agent for dip-coating sealing treatment, wherein the sealing agent is a water-based silane solvent containing cerium, curing after sealing, and obtaining the rare earth permanent magnet after curing.
Preferably, the blocking agent comprises a water-based silane solvent and cerium oxide, and the mass of the cerium oxide is 0.5-2.1% of that of the water-based silane solvent.
Preferably, the sealant further comprises nano SiO2。
Preferably, the curing treatment is carried out at a baking temperature of 150-.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:
(1) according to the rare earth permanent magnet with the hydrogen resistance, the sum of the mass percentages of Co and Fe in the rare earth permanent magnet is more than 3 times of the mass percentage of Sm, so that the surface of the rare earth permanent magnet is more densified and more stable, meanwhile, the path of hydrogen atoms entering a crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
(2) According to the preparation method of the rare earth permanent magnet with the hydrogen resistance, the rare earth permanent magnet is subjected to heat treatment after sintering treatment, so that the rare earth phase enriched in the crystal boundary is distributed more uniformly, the densification of the crystal boundary is promoted, the path of hydrogen atoms entering the crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
(3) According to the preparation method of the rare earth permanent magnet with the hydrogen resistance, the rare earth permanent magnet after heat treatment is subjected to sealing treatment, so that a thin film sealing layer is formed on the surface of the rare earth permanent magnet, and the thin film sealing layer can fill micro cracks and micro holes on the surface of the rare earth permanent magnet by controlling the curing temperature to be 150-.
(4) According to the preparation method of the rare earth permanent magnet with the hydrogen resistance, the rare earth permanent magnet is subjected to sealing treatment by adopting the water-based silane solvent containing cerium, the silane treatment agent on the metal surface forms a metal silane composite film through film forming reaction, the water-based silane solvent containing cerium forms a large amount of oligosiloxane through condensation reaction, so that a sealing layer of a composite passivation film is formed on the surface of the rare earth permanent magnet, and the sealing layer has self-repairing capacity and can prevent the rare earth permanent magnet material from being scratched to cause magnet damage.
(5) The invention relates to a preparation method of a rare earth permanent magnet with hydrogen resistance, which adds nano SiO in the sealing treatment process2Nano SiO in the process of sealing treatment2Can gather at the micropore defect of the hydrogen-resistant layer, promote to form a complete silane film sealing layer while improving the strength of the sealing side, and prevent the process of hydrogen atoms from migrating from the surface of the magnet to the interior of the magnet.
Drawings
FIG. 1 is a graph showing the change in hydrogen absorption with time (100 ℃ C.) for example 1 of the present invention and comparative example 1.
Detailed Description
For further explanation of the present invention, the present invention will be explained in detail with reference to the following examples and drawings, and the details will be described below.
Example 1
The rare earth permanent magnet Sm with hydrogen resistance2(CoCuFeZr)17The sum of the mass percentages of the magnet, the Co and the Fe is more than that of Sm, and further illustrates, wherein the mass percentage of Sm is m, the sum of the mass percentages of the Co and the Fe is n, and n is>3m, is added. The sum of the mass percentages of Co and Fe is set to be larger than that of Sm, so that Sm is wrapped by Co and Fe, and the rare earth permanent magnet Sm is prepared2(CoCuFeZr)17The magnet is more compact, so that the path of hydrogen atoms entering a crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
The preparation method of the hydrogen-resistant rare earth permanent magnet comprises the following steps:
(1) smelting: mixing the materials according to the components, and smelting the mixture in a smelting furnace to obtain Sm2(CoCuFeZr)17The magnet comprises the following elements in percentage by mass: 45-55% of Co, 15-23% of Sm, 2-6% of Cu, 18-20% of Fe, 1-4% of Zr and 0-2% of impurities; the rare earth permanent magnet in the embodiment comprises the following elements in percentage by mass: 47% of Co, 18% of Sm, 3% of Cu, 19% of Fe, 2% of Zr and 1% of impurities; and obtaining an ingot.
(2) Milling: crushing and pulverizing the cast ingot to obtain permanent magnet powder, wherein the particle size of the permanent magnet powder is controlled to be 1-10 mu m, and the mass percentage of particles with the particle size distribution of 3-5 mu m is more than 80%; the powder preparation method comprises jet milling, wherein 0.1-3.5mL of antioxidant is added into per kilogram of permanent magnet powder during the jet milling process, wherein the antioxidant is thymol (C)10H14O) and calcium stearate (C)36H70O4Ca), and thymol (C)10H14O) and calcium stearate (C)36H70O4Ca) is 1:2, the antioxidant in the permanent magnet powder per kilogram in the embodiment is 2mL, and Sm can be reduced2O3The content of impurities;
(3) compression molding: punching and forming the permanent magnet powder to obtain a permanent magnet green body;
(4) sintering treatment: sintering the permanent magnet green body at 1150-1250 ℃ for 3-5 hours to obtain a permanent magnet blank after sintering;
in the embodiment, the sintering temperature is controlled to be 1230 ℃ in the sintering treatment process, the sintering time is 4 hours, argon is adopted for protection in the sintering process, and the furnace temperature uniformity is controlled to be +/-2 ℃ under the condition of full load in the sintering process;
(5) and (3) heat treatment: after sintering, cooling the permanent magnet blank to room temperature, and then carrying out heat treatment on the permanent magnet blank in a nitrogen atmosphere, wherein the heat treatment temperature is 650-1050 ℃, and the heat treatment time is more than 12 hours;
in detail, the heat treatment process comprises three stages:
stage one: firstly, heating the rare earth permanent magnet to 650-750 ℃ under the vacuum condition, wherein the vacuum degree is 1.3 multiplied by 10-1～1.3×10-3Pa, heat preservation treatment for 2-3 h; in this embodiment, the rare earth permanent magnet is heated to 750 ℃ and heat preservation is performed for 2h, in this embodiment, the temperature is 1.5 × 10-2Pa；
And a second stage: heating to 750-850 ℃ at a heating rate of 1-5 ℃/min, introducing nitrogen into the vacuum furnace, controlling the nitrogen partial pressure in the furnace to protect the atmosphere at 200-300 mbar after the temperature in the furnace is reached, and then carrying out heat preservation treatment for 2-3 h; in the embodiment, the temperature is raised to 850 ℃ at the heating rate of 3 ℃/min, nitrogen is introduced into the heat treatment furnace, the nitrogen partial pressure protective atmosphere in the furnace is controlled to be 200mbar, and the heat preservation treatment is carried out for 2 hours;
and a third stage: heating to 900-1050 ℃ at a heating rate of 1-5 ℃/min, and carrying out heat preservation treatment for 8-15 h. In the embodiment, the temperature is raised to 1050 ℃ at the temperature raising speed of 3 ℃/min, and the heat preservation treatment is carried out for 8 h;
the space-time cooling speed is controlled to be 175 ℃/h in the cooling process, so that the rare earth magnet crystal grains are more uniform and fine, the distribution of the crystal boundary enriched rare earth phase is more uniform, the crystal boundary is purified to promote the densification of the material, the path of hydrogen atoms entering the crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
Because nitrogen has a gap atom effect, the concentration of nitrogen atoms in the metal layer surface of the rare earth permanent magnet surface is the highest in the heat treatment process, and the penetration limit of the nitrogen atoms in the metal exists, so that the concentration of the nitrogen atoms in the permanent magnet approaches to zero, and the concentration gradient of the nitrogen atoms from outside to inside is formed; wherein the permeation limit of the nitrogen atoms is related to the nitrogen atom concentration, the reaction time, and the reaction temperature; during the heat treatment, nitrogen atoms continuously permeate to the nitrogen content low region under the driving of the concentration gradient, and finally nitrogen forms balanced nitrogen concentration inside the metal layer on the surface layer of the samarium-iron-cobalt alloy. Namely, in the process of heat treatment, nitrogen permeating into the surface layer of the samarium-iron-cobalt alloy reacts with the surface of the magnet, so that the nitrogen and the samarium-iron-cobalt alloy on the surface of the rare earth permanent magnet are subjected to gas-solid reaction, nitrogen atoms are introduced into interstitial sites of the samarium-iron-cobalt alloy and stably exist, and then a stable complete nitriding phase is formed on the surface of the rare earth permanent magnet, and the rare earth permanent magnet has hydrogen resistance. It is worth noting that this process is not only a physical infiltration process, but also a dynamic chemical infiltration process, since nitrogen gradually reacts with samarium iron cobalt alloy during the infiltration process.
In addition, the heat treatment of the invention can also make the distribution of the grain boundary enriched rare earth phase more uniform, purify the impurities of the grain boundary on the surface of the rare earth permanent magnet, reduce the path of hydrogen atoms entering the grain boundary from the surface of the material, and improve the hydrogen resistance of the rare earth permanent magnet material.
(6) Sealing treatment:
in order to improve the hydrogen resistance, this example performs a sealing treatment after the heat treatment step; cooling to room temperature, degreasing and washing the rare earth permanent magnet, dip-coating the rare earth permanent magnet by using a sealing agent, wherein the sealing agent is a water-based silane solvent containing cerium, and baking and curing at the temperature of 150-180 ℃ after dip-coating and sealing, so as to form a sealing layer on the surface, and the baking and curing temperature in the embodiment is 180 ℃.
It is worth mentioning that the blocking agent comprises a water-based silane solvent, cerium oxide and water, wherein the water-based silane solvent is a mixed silane system of bis (3-trimethoxysilylpropyl) amine (BAS) and Vinyltriacetoxysilane (VTAS), and the blocking agent is prepared by the following specific steps:
firstly, mixing bis (3-trimethoxysilylpropyl) amine (BAS) and Vinyl Triacetoxysilane (VTAS) according to a volume ratio of 1:5, and stirring for 4 hours to obtain a mixed silane system, wherein the mixed silane system is a water-based silane solvent;
then, adding cerium oxide into the water-based silane solvent, wherein the addition amount of the cerium oxide is 0.5-2.1% of the mass of the water-based silane solvent; mixing and stirring, adding water, wherein the water can be deionized water, the adding amount of the deionized water is 35-55 times of the volume of the water-based silane solvent, and continuously stirring for 6-8 hours after adding the water to obtain the sealant; the deionized water was added in an amount 35 times the volume of the aqueous silane solvent for 6 hours of stirring.
The rare earth permanent magnet is soaked in the sealing agent to form a sealing film layer on the surface of the rare earth permanent magnet, and the formed silanization sealing layer can fill micro cracks and micropores on the surface of the rare earth permanent magnet, so that the capability of the magnet for long-term stable work in a hydrogen environment can be ensured; the water-based silane solvent of cerium oxide forms a large amount of oligosiloxane through condensation reaction, a composite passivation film is formed on the surface of metal, and the composite passivation closed film layer has high hardness and self-repairing capability, namely after the rare earth permanent magnet material is scratched, the composite passivation closed film layer can react with oxygen and water in the air, and the scratched position of the closed film layer is repaired, so that the aim of preventing hydrogen from entering the magnet is fulfilled.
The prepared rare earth permanent magnet is subjected to hydrogen resistance detection, namely the prepared rare earth permanent magnet is subjected to hydrogen absorption performance detection at 100 ℃ and under the hydrogen pressure of 1MPa, the hydrogen content in the rare earth permanent magnet is detected in the hydrogen absorption process, and the hydrogen content is drawn in a graph 1.
Comparative example 1
The rare earth permanent magnetic material prepared by the comparative example comprises the following components: 48% of Co, 27% of Sm, 8% of Cu, 15% of Fe, 1% of Zr and 1% of impurities. The preparation method of the rare earth permanent magnetic material of the comparative example is as follows:
(1) smelting: mixing the materials according to the components, and smelting the mixture in a smelting furnace to obtain Sm2(CoCuFeZr)17The magnet comprises the following elements in percentage by mass: 48% of Co, 27% of Sm, 8% of Cu, 15% of Fe, 1% of Zr and 1% of impurities; and obtaining an ingot.
(2) Milling: crushing and pulverizing the cast ingot to obtain permanent magnet powder, wherein the particle size of the permanent magnet powder is controlled to be 1-10 mu m; the powder preparation method can select an airflow mill, and 2mL/kg antioxidant is added in the airflow mill process;
(3) compression molding: punching and forming the permanent magnet powder to obtain a permanent magnet green body;
(4) sintering treatment: sintering the permanent magnet green body at 1230 ℃ for 4 hours to obtain a finished rare earth permanent magnet in the prior art;
the comparative example does not carry out heat treatment or sealing treatment in the process of preparing the rare earth permanent magnet; and obtaining the rare earth permanent magnet of the product after sintering.
Then, the rare earth permanent magnet prepared in the comparative example 1 is subjected to hydrogen resistance detection, that is, the prepared rare earth permanent magnet is subjected to hydrogen absorption performance detection at 100 ℃ and under the hydrogen pressure of 1MPa, and the hydrogen content in the rare earth permanent magnet is detected in the hydrogen absorption process, and is plotted in fig. 1.
As can be seen by comparing example 1 with comparative example 1 in fig. 1, the rare earth permanent magnet in example 1 has a hydrogen absorption amount of 0 at 24 hours, i.e., does not react with hydrogen gas, and is always maintained at a low level. However, the hydrogen absorption amount of the rare earth permanent magnet in the prior art is gradually increased along with the increase of time, and particularly after the hydrogen absorption is carried out for 5 hours, the hydrogen absorption amount of the rare earth permanent magnet is obviously increased. The reason is that the rare earth magnetic material does not react with hydrogen through special components and a heat treatment process; the rare earth magnetic material improves the hydrogen resistance of the rare earth permanent magnet through heat treatment, a closed film layer is formed on the surface of the magnet, and the silanized closed layer after film formation can fill micro cracks and micropores on the surface of the rare earth permanent magnet, so that the capability of the magnet for long-term stable work in a hydrogen environment can be ensured.
Example 2
The basic contents of the present invention are different from those of embodiment 1 in that: the preparation method of the hydrogen-resistant rare earth permanent magnet comprises the following steps:
(1) smelting: mixing the materials according to the components, and smelting the mixture in a smelting furnace to obtain Sm2(CoCuFeZr)17The magnet comprises the following elements in percentage by mass: 50% of Co, 23% of Sm, 5% of Cu, 20% of Fe, 1% of Zr and 1% of impurities; and obtaining an ingot.
(2) Milling: crushing and pulverizing the cast ingot to obtain permanent magnet powder, wherein the particle size of the permanent magnet powder is controlled to be 1-10 mu m, and the mass percentage of particles with the particle size distribution of 3-5 mu m is more than 80%; the powder preparation method can select an airflow mill, and 0.1-3.5mL of antioxidant is added into each kilogram of permanent magnet powder in the airflow mill process;
(3) compression molding: punching and forming the permanent magnet powder to obtain a permanent magnet green body;
(4) sintering treatment: sintering the permanent magnet green body at 1250 ℃ for 5 hours to obtain a permanent magnet blank after sintering; argon is adopted for protection in the sintering process;
(5) and (3) heat treatment: the heat treatment process comprises three stages:
stage one: firstly, under the condition of vacuum, the rare earth permanent magnet is heated to 650 deg.C, and the vacuum degree is 1.3X 10-3Pa, heat preservation treatment for 2.5 h;
and a second stage: in the embodiment, the temperature is increased to 750 ℃ at the temperature rising speed of 1 ℃/min, nitrogen is introduced into the heat treatment furnace, the nitrogen partial pressure protective atmosphere in the furnace is controlled to be 300mbar, and the heat preservation treatment is carried out for 2.5 h;
and a third stage: in the embodiment, the temperature is increased to 900 ℃ at the temperature increasing speed of 1 ℃/min, and the heat preservation treatment is carried out for 10 hours;
the space-time cooling speed is controlled to be 120 ℃/h in the cooling process, so that the rare earth magnet crystal grains are more uniform and fine, the distribution of the crystal boundary enriched rare earth phase is more uniform, the crystal boundary is purified to promote the densification of the material, the path of hydrogen atoms entering the crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
(6) Sealing treatment: after cooling to room temperature, the rare earth permanent magnet is first degreased and washed, and then the rare earth permanent magnet is dip-coated with a sealing agent, the sealing agent is a water-based silane solvent containing cerium, and after dip-coating and sealing, the rare earth permanent magnet is baked and cured at 180 ℃, so that a sealing layer is formed on the surface, wherein the baking and curing temperature of the embodiment is 150 ℃.
It is worth pointing out that the sealing agent comprises water-based silane solvent, cerium oxide and nano SiO2And water, wherein the water-based silane solvent is a mixed silane system of bis (3-trimethoxysilylpropyl) amine (BAS) and Vinyl Triacetoxysilane (VTAS), and the preparation method of the sealant comprises the following specific steps:
firstly, mixing bis (3-trimethoxysilylpropyl) amine (BAS) and Vinyl Triacetoxysilane (VTAS) according to a volume ratio of 1:5, and stirring for 4 hours to obtain a mixed silane system, wherein the mixed silane system is a water-based silane solvent;
then, adding cerium oxide into the water-based silane solvent, wherein the addition amount of the cerium oxide is 0.5-2.1% of the mass of the water-based silane solvent, and the addition amount of the cerium oxide in the embodiment is 2%; mixing and stirring, adding water, wherein the water can be deionized water, the adding amount of the deionized water is 40 times of the volume of the water-based silane solvent, and stirring for 8 hours; then adding nano SiO into the mixture2Nano SiO2The addition amount of the nano SiO is 0.5-5.0% of the total mass of the water-based silane solvent, the cerium oxide and the water2The adding amount is 2.5 percent, and the nano SiO2Has a diameter of 10-30 nm.
The rare earth permanent magnet has the advantages that the rare earth phases enriched in the surface crystal boundary are distributed more uniformly, the densification of the crystal boundary is promoted, the path of hydrogen atoms entering the crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved; it is worth to say that the nano SiO is contained in the sealing agent2Nano SiO2Gather at the micropore defect of the hydrogen-resistant layer to form a complete silane film and improveThe strength of the sealing layer prevents the migration of hydrogen atoms from the surface of the magnet into the interior of the magnet.
Example 3
The basic contents of the present invention are different from those of embodiment 1 in that: the preparation method of the hydrogen-resistant rare earth permanent magnet comprises the following steps:
(1) smelting: mixing the materials according to the components, and smelting the mixture in a smelting furnace to obtain Sm2(CoCuFeZr)17The magnet comprises the following elements in percentage by mass: 55% of Co, 15% of Sm, 6% of Cu, 18% of Fe, 4% of Zr and 2% of impurities; and obtaining an ingot.
(2) Milling: crushing and pulverizing the cast ingot to obtain permanent magnet powder, wherein the particle size of the permanent magnet powder is controlled to be 1-10 mu m, and the mass percentage of particles with the particle size distribution of 3-5 mu m is more than 80%; the powder preparation method can select an airflow mill, and 3.5mL of antioxidant is added into each kilogram of permanent magnet powder in the airflow mill process;
(3) compression molding: punching and forming the permanent magnet powder to obtain a permanent magnet green body;
(4) sintering treatment: sintering the permanent magnet green body at 1150 ℃ for 3 hours to obtain a permanent magnet blank after sintering; argon is adopted for protection in the sintering process;
(5) and (3) heat treatment: the heat treatment process comprises three stages:
stage one: firstly, under the condition of vacuum, the rare earth permanent magnet is heated to 700 deg.C, and the vacuum degree is 1.3X 10-1Pa, heat preservation treatment for 3 h;
and a second stage: in the embodiment, the temperature is increased to 800 ℃ at the temperature increasing speed of 5 ℃/min, nitrogen is introduced into the heat treatment furnace, the nitrogen partial pressure protective atmosphere in the furnace is controlled to be 250mbar, and the heat preservation treatment is carried out for 3 hours;
and a third stage: in the embodiment, the temperature is raised to 1000 ℃ at the temperature raising speed of 5 ℃/min, and the heat preservation treatment is carried out for 15 h;
the space-time cooling speed is controlled to be 175 ℃/h in the cooling process, so that the rare earth magnet crystal grains are more uniform and fine, the distribution of the crystal boundary enriched rare earth phase is more uniform, the crystal boundary is purified to promote the densification of the material, the path of hydrogen atoms entering the crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved.
(6) Sealing treatment: cooling to room temperature, degreasing and washing the rare earth permanent magnet, pre-coating the rare earth permanent magnet in a pre-coating agent containing nano SiO2The water-based silane solvent is baked and cured at the temperature of 180 ℃, so that a precoat layer is formed on the surface layer of the rare earth permanent magnet; and then, dip-coating the surface of the rare earth permanent magnet by using a sealant, wherein the sealant is a water-based silane solvent containing cerium, the baking and curing temperature in the embodiment is 160 ℃, and the sealant in the embodiment is the same as that in the embodiment 1.
It is worth mentioning that the precoating agent comprises water-based silane solvent, nano SiO2And water, wherein the water-based silane solvent is a mixed silane system of bis (3-trimethoxysilylpropyl) amine (BAS) and Vinyl Triacetoxysilane (VTAS), and the preparation method of the sealant comprises the following specific steps:
firstly, mixing bis (3-trimethoxysilylpropyl) amine (BAS) and Vinyl Triacetoxysilane (VTAS) according to a volume ratio of 1:5 to obtain a mixed silane system, wherein the mixed silane system is a water-based silane solvent;
then, adding water into the water-based silane solvent, wherein the water can be deionized water, the addition amount of the deionized water is 40 times of the volume of the water-based silane solvent, and continuing stirring for 6 hours after adding the water; then adding nano SiO into the mixture2Nano SiO2The addition amount of the nano SiO is 0.5-5.0% of the total mass of the water-based silane solvent and the water2The amount added was 3%.
The rare earth permanent magnet has hydrogen resistance, the rare earth phase enriched in the crystal boundary is distributed more uniformly, the densification of the crystal boundary is promoted, the path of hydrogen atoms entering the crystal boundary from the surface of the material is reduced, and the hydrogen resistance of the rare earth permanent magnet material is improved; it is worth to say that the precoating layer is firstly dip-coated on the surface of the rare earth permanent magnet material, and the precoating layer contains nano SiO2Nano SiO2Gather at the micropore defect of the hydrogen-resistant layer to form a complete silane film; then dip-coating the seal layer to form a pre-coat layerThe sealing layer is formed on the outer surface, the sealing film layer is formed on the surface of the rare earth permanent magnet, and the silanization sealing layer after film forming can fill micro cracks and micropores on the surface of the rare earth permanent magnet, so that the capability of the magnet to stably work in a hydrogen environment for a long time can be ensured.
Example 4
The basic contents of the present invention are different from those of embodiment 1 in that: in this embodiment, after the permanent magnet blank is heat-treated, the rare earth permanent magnet is prepared, i.e., no sealing treatment is performed. The rare earth permanent magnet prepared by the embodiment still has good hydrogen resistance, because the rare earth permanent magnet is subjected to heat treatment, the rare earth phase enriched in the grain boundary is distributed more uniformly, the densification of the grain boundary is promoted, and the hydrogen resistance of the rare earth permanent magnet material is improved; further, it is worth mentioning that the hydrogen resistance of this example is slightly inferior to that of example 1.
The invention has been described in detail hereinabove with reference to specific exemplary embodiments thereof. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.
Claims (10)
1. A rare earth permanent magnet having hydrogen resistance, characterized in that: the mass percentage of Sm in the rare earth permanent magnet is m, the sum of the mass percentages of Co and Fe is n, and n is more than 3 m.
2. A rare earth permanent magnet having hydrogen resistance according to claim 1, characterized in that: the mass percentage of Co is 45-55%, the mass percentage of Fe is 18-20%, and the mass percentage of Sm is 15-23%.
3. A rare earth permanent magnet having hydrogen resistance according to claim 1, characterized in that: the rare earth permanent magnet is provided with a sealing layer outside, and the sealing layer is formed by sealing a water-based silane solvent containing cerium.
4. A rare earth permanent magnet having hydrogen resistance according to any one of claims 1 to 3, characterized in that: the mass percentage of Cu is 2-6%.
5. A preparation method of a hydrogen-resistant rare earth permanent magnet is characterized by comprising the following steps:
(1) smelting: smelting in a smelting furnace to obtain a magnet, wherein the mass percentage of Sm is m, the sum of the mass percentages of Co and Fe is n, and n is more than 3m, and obtaining an ingot;
(2) milling: crushing and pulverizing the cast ingot to obtain permanent magnet powder;
(3) compression molding: punching and forming the permanent magnet powder to obtain a permanent magnet green body;
(4) sintering treatment: sintering the permanent magnet green body at 1150-1250 ℃ for 3-5 hours to obtain a permanent magnet blank after sintering;
(5) and (3) heat treatment: and after sintering, cooling to room temperature, and then carrying out heat treatment on the permanent magnet blank in a nitrogen atmosphere, wherein the heat treatment temperature is 650-1050 ℃, and the heat treatment time is more than 12 hours.
6. The method for preparing a hydrogen-resistant rare earth permanent magnet according to claim 5, wherein: the heat treatment process comprises three stages:
stage one: heating the rare earth permanent magnet to 650-750 ℃, and carrying out heat preservation treatment for 2-3 h;
and a second stage: heating to 750-850 ℃ at a heating rate of 1-5 ℃/min, filling nitrogen into the vacuum furnace, and then carrying out heat preservation treatment for 2-3 h;
and a third stage: heating to 900-1050 ℃ at a heating rate of 1-5 ℃/min, and carrying out heat preservation treatment for 10-15 h.
7. The method for producing a hydrogen-resistant rare earth permanent magnet according to claim 5 or 6, characterized in that: and after the heat treatment, sealing the rare earth permanent magnet, and specifically comprising the following steps: and cooling the rare earth permanent magnet to room temperature, immersing the rare earth permanent magnet into a sealing agent for dip-coating sealing treatment, wherein the sealing agent is a water-based silane solvent containing cerium, curing after sealing, and obtaining the rare earth permanent magnet after curing.
8. The method for preparing a hydrogen-resistant rare earth permanent magnet according to claim 7, wherein: the sealing agent comprises a water-based silane solvent and cerium oxide, and the mass of the cerium oxide is 0.5-2.1% of that of the water-based silane solvent.
9. The method for preparing a hydrogen-resistant rare earth permanent magnet according to claim 7, wherein: the sealant also comprises nano SiO2。
10. The method for preparing a hydrogen-resistant rare earth permanent magnet according to claim 7, wherein: the baking temperature of the curing treatment is 150-180 ℃.
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