CN114743783A - Method for reducing oxygen content of sintered neodymium-iron-boron magnet - Google Patents
Method for reducing oxygen content of sintered neodymium-iron-boron magnet Download PDFInfo
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- CN114743783A CN114743783A CN202210374479.XA CN202210374479A CN114743783A CN 114743783 A CN114743783 A CN 114743783A CN 202210374479 A CN202210374479 A CN 202210374479A CN 114743783 A CN114743783 A CN 114743783A
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- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 23
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 22
- 239000001301 oxygen Substances 0.000 title claims abstract description 22
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 22
- 239000006247 magnetic powder Substances 0.000 claims description 60
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 claims description 43
- 238000010438 heat treatment Methods 0.000 claims description 40
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- 239000003999 initiator Substances 0.000 claims description 20
- 238000005245 sintering Methods 0.000 claims description 18
- 239000003054 catalyst Substances 0.000 claims description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 16
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- 238000010992 reflux Methods 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 230000006835 compression Effects 0.000 claims description 9
- 238000007906 compression Methods 0.000 claims description 9
- OZAIFHULBGXAKX-UHFFFAOYSA-N 2-(2-cyanopropan-2-yldiazenyl)-2-methylpropanenitrile Chemical group N#CC(C)(C)N=NC(C)(C)C#N OZAIFHULBGXAKX-UHFFFAOYSA-N 0.000 claims description 8
- 239000011261 inert gas Substances 0.000 claims description 8
- 238000010907 mechanical stirring Methods 0.000 claims description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- 238000000967 suction filtration Methods 0.000 claims description 7
- 238000001291 vacuum drying Methods 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 5
- UKLDJPRMSDWDSL-UHFFFAOYSA-L [dibutyl(dodecanoyloxy)stannyl] dodecanoate Chemical compound CCCCCCCCCCCC(=O)O[Sn](CCCC)(CCCC)OC(=O)CCCCCCCCCCC UKLDJPRMSDWDSL-UHFFFAOYSA-L 0.000 claims description 4
- 239000012975 dibutyltin dilaurate Substances 0.000 claims description 4
- KSBAEPSJVUENNK-UHFFFAOYSA-L tin(ii) 2-ethylhexanoate Chemical group [Sn+2].CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O KSBAEPSJVUENNK-UHFFFAOYSA-L 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 2
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- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 239000011247 coating layer Substances 0.000 description 5
- 239000003607 modifier Substances 0.000 description 5
- 239000005416 organic matter Substances 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 4
- 239000006087 Silane Coupling Agent Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- XDLMVUHYZWKMMD-UHFFFAOYSA-N 3-trimethoxysilylpropyl 2-methylprop-2-enoate Chemical compound CO[Si](OC)(OC)CCCOC(=O)C(C)=C XDLMVUHYZWKMMD-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
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- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000003064 anti-oxidating effect Effects 0.000 description 2
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 238000012644 addition polymerization Methods 0.000 description 1
- 238000007259 addition reaction Methods 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
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- 239000006227 byproduct Substances 0.000 description 1
- 239000007810 chemical reaction solvent Substances 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 description 1
- WELLGRANCAVMDP-UHFFFAOYSA-N isocyanatoethane;prop-2-enoic acid Chemical compound CCN=C=O.OC(=O)C=C WELLGRANCAVMDP-UHFFFAOYSA-N 0.000 description 1
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- 230000007774 longterm Effects 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
Classifications
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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
- H01F41/026—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 protecting methods against environmental influences, e.g. oxygen, by surface treatment
-
- 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
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes 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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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Hard Magnetic Materials (AREA)
- Powder Metallurgy (AREA)
Abstract
The invention discloses a method for reducing the oxygen content of a sintered neodymium-iron-boron magnet, which relates to the technical field of magnet materials.
Description
The technical field is as follows:
the invention relates to the technical field of magnet materials, in particular to a method for reducing the oxygen content of a sintered neodymium-iron-boron magnet.
Background art:
the sintered Nd-Fe-B magnet has higher remanence and magnetic energy product, good dynamic recovery characteristic and high cost performance than other permanent magnets, and is widely applied to the fields of electronics, automobiles, computers, energy sources, medical appliances and the like. Because the rare earth elements have high metal activity, the neodymium iron boron magnetic powder is very easy to generate electrochemical reaction with oxygen and water vapor in the air at normal temperature to be oxidized, so that the performance of the sintered neodymium iron boron magnet is influenced, and the magnetic powder is subjected to anti-oxidation treatment in the production process of the sintered neodymium iron boron magnet. The current common method is to add a very small amount (less than or equal to 0.5 wt%) of organic matter before or after the jet mill after hydrogen crushing, coat the organic matter on the surface of the magnetic powder in a physical mixing way, prevent the magnetic powder from being oxidized by contacting with oxygen and water vapor in the air, reduce the oxygen content of the sintered neodymium iron boron magnet, and thus improve the magnetic performance of the sintered neodymium iron boron magnet.
Although the above method of adding organic substances to magnetic powder and physically mixing them can prevent oxidation in a short time, the adsorption force between the organic substances and the magnetic powder is weak, and part of the organic substances are volatile, so that the organic substances are easily desorbed from the surface of the magnetic powder to lose the oxidation prevention effect, which is not favorable for long-term storage of the magnetic powder, and the green compact cannot be exposed to the air for a long time during the compression molding process. Moreover, because the fluidity of the magnetic powder is poor, the physical mixing mode cannot make the organic matter completely and densely coat the surfaces of all the magnetic powder, and therefore the anti-oxidation effect is not good.
Patent CN108231310A discloses a preparation method of modified neodymium iron boron magnetic powder, which comprises connecting a silane coupling agent containing carbon-carbon double bond with neodymium iron boron magnetic powder through chemical bond, adding acrylic unsaturated monomer and/or aromatic unsaturated monomer to perform graft reaction with the silane coupling agent containing carbon-carbon double bond, forming a coating layer on the surface of neodymium iron boron magnetic powder, and obtaining the modified neodymium iron boron magnetic powder. This patent describes in paragraphs [0040] and [0043] the preparation principle that "the silane coupling agent can react with hydroxyl groups (-OH) on the surface of magnetic powder, connecting with magnetic powder through chemical bond to coat a layer of organic matter containing carbon-carbon double bond functional group on the surface of magnetic powder, changing hydrophilicity of the surface of magnetic powder into lipophilicity, carrying out graft reaction between unsaturated monomer and modifier on the surface of magnetic powder through carbon-carbon double bond, then, a polymerization reaction is carried out on the basis, and a complete and compact polymer coating layer is formed on the surface of the magnetic powder, the method adopts silane coupling agent containing carbon-carbon double bond as a bridge for connecting magnetic powder and organic matter, the average oxygen content of the neodymium iron boron sintered body prepared by the modified neodymium iron boron magnetic powder prepared in the embodiment after being placed in the air for 7 days through orientation compression and vacuum sintering is more than 1000 ppm. The object of the present invention is to modify the process, and it is desirable to further reduce the oxygen content of the sintered neodymium iron boron body.
The invention content is as follows:
the invention aims to solve the technical problem of providing a method for reducing the oxygen content of a sintered neodymium iron boron magnet, wherein isocyanate ethyl acrylate is used as a modifier, the neodymium iron boron magnetic powder is coated on the surface through chemical reaction, the uniformity and the stability of the surface coating are improved, and the oxygen content of the sintered neodymium iron boron magnet is reduced while the magnetic performance of the sintered neodymium iron boron magnet is ensured.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a method for reducing the oxygen content of a sintered NdFeB magnet comprises the following steps:
(1) vacuum drying neodymium iron boron magnetic powder and a catalyst, adding the neodymium iron boron magnetic powder and the catalyst into isocyanate ethyl acrylate, heating and carrying out reflux reaction under the protection of nitrogen, mechanical stirring and assistance of ultrasonic waves, adding an initiator, continuing reflux reaction, cooling after the reaction is finished, adding water for stirring, carrying out suction filtration, washing with ethanol, and vacuum drying to obtain modified neodymium iron boron magnetic powder;
(2) carrying out orientation compression on the modified neodymium iron boron magnetic powder through a magnetic field to obtain a blank;
(3) and sequentially carrying out high-temperature roasting and vacuum sintering on the blank, cooling and carrying out heat treatment to obtain the sintered neodymium-iron-boron magnet.
In the step (1), under the action of a catalyst, hydroxyl on the surface of the neodymium iron boron magnetic powder and isocyanate groups in isocyanate ethyl acrylate molecules quickly react, so that the isocyanate ethyl acrylate is connected with the neodymium iron boron magnetic powder through chemical bonds; the carbon-carbon double bond in the isocyanate ethyl acrylate molecule rapidly generates polyaddition reaction under the action of an initiator, a complete, uniform and compact polymer coating layer is formed on the surface of the magnetic powder, the neodymium iron boron magnetic powder is protected, oxygen and water vapor in the air are isolated, and the neodymium iron boron magnetic powder is prevented from being oxidized in the storage and processing processes.
In the step (1), the isocyanate ethyl acrylate is used as a reactant to participate in the reaction, and is used as a reaction solvent, so that a large amount of organic solvents are avoided, the cost is reduced, the post-treatment operation can be reduced, water is added to quench the reaction during the post-treatment, the redundant isocyanate ethyl acrylate reacts with the water, and the by-products can be removed by washing with ethanol.
In the step (1), the nitrogen protection is to remove the interference of oxygen in the air to the chemical reaction, and the mechanical stirring and the ultrasonic assistance are to increase the contact area of the isocyanate ethyl acrylate and the neodymium iron boron magnetic powder, shorten the reaction time and improve the reaction uniformity.
The mass ratio of the neodymium iron boron magnetic powder to the isocyanate ethyl acrylate is 100 (10-20).
The catalyst is stannous octoate or dibutyltin dilaurate.
The dosage of the catalyst is 0.1-1% of the mass of the isocyanate ethyl acrylate.
The initiator is azobisisobutyronitrile or azobisisoheptonitrile.
The using amount of the initiator is 0.05-0.5% of the mass of the isocyanate ethyl acrylate.
The magnetic field adopts a direct current pulse magnetic field, and the pressure of the magnetic field is 1.8-2.0T.
The high-temperature roasting temperature is 500-600 ℃, and the heat preservation time is 1-3 h. The polymer coating is removed by high temperature firing.
The vacuum sintering temperature is 1050-.
The cooling is natural cooling to 700-800 ℃ and then inert gas is introduced for cooling to below 100 ℃.
The heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 850-; the temperature of the secondary heat treatment is 500-600 ℃, and the heat preservation time is 1-3 h.
The invention has the beneficial effects that: according to the invention, isocyanate ethyl acrylate is used as a modifier, a complete, uniform and compact polymer coating layer is formed on the surface of the neodymium iron boron magnetic powder after addition reaction and addition polymerization reaction, oxygen and water vapor in the air are isolated by the polymer coating layer, the neodymium iron boron magnetic powder is prevented from oxidation reaction in the storage and processing processes, the oxygen content of the sintered neodymium iron boron magnet is reduced, and the magnetic performance of the sintered neodymium iron boron magnet is ensured.
The specific implementation mode is as follows:
in order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.
The components and mass percentages of the neodymium iron boron magnetic powder in the following examples and comparative examples are Nd 15%, Co0.25%, B3.2%, Cu 0.2%, and the balance Fe, and the average particle size is 3.5 μm.
Example 1
(1) And (2) drying 100g of neodymium iron boron magnetic powder and a catalyst in vacuum, adding the dried mixture into 10g of isocyanate ethyl acrylate, heating and carrying out reflux reaction for 30min under the protection of nitrogen, mechanical stirring and assistance of ultrasonic waves, adding an initiator, continuing reflux reaction for 2h, cooling after the reaction is finished, adding water, stirring, carrying out suction filtration, washing with ethanol, and drying in vacuum to obtain the modified neodymium iron boron magnetic powder.
(2) Carrying out orientation compression on the modified neodymium iron boron magnetic powder by a magnetic field, wherein the magnetic field adopts a direct current pulse magnetic field, the pressure of the magnetic field is 1.8T, obtaining a blank,
(3) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, wherein the high-temperature roasting temperature is 500 ℃, and the heat preservation time is 2 hours; the vacuum sintering temperature is 1050 ℃, the heat preservation time is 4 hours, the heat treatment is carried out after cooling, the cooling is that the natural cooling is carried out to 700 ℃, then the inert gas is introduced for cooling to 50 ℃, the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 850 ℃, and the heat preservation time is 2 hours; the temperature of the secondary heat treatment is 500 ℃, and the heat preservation time is 3 hours, so that the sintered neodymium-iron-boron magnet is obtained.
Wherein the catalyst is dibutyltin dilaurate, and the using amount of the catalyst is 0.5 percent of the mass of isocyanate ethyl acrylate; the initiator is azobisisobutyronitrile, and the using amount of the initiator is 0.25 percent of the mass of the isocyanate ethyl acrylate.
Example 2
(1) And (2) drying 100g of neodymium iron boron magnetic powder and a catalyst in vacuum, adding the dried mixture into 15g of isocyanate ethyl acrylate, heating and carrying out reflux reaction for 30min under the protection of nitrogen, mechanical stirring and assistance of ultrasonic waves, adding an initiator, continuing reflux reaction for 2h, cooling after the reaction is finished, adding water, stirring, carrying out suction filtration, washing with ethanol, and drying in vacuum to obtain the modified neodymium iron boron magnetic powder.
(2) Carrying out orientation compression on the modified neodymium iron boron magnetic powder by a magnetic field, wherein the magnetic field adopts a direct current pulse magnetic field, the pressure of the magnetic field is 2.0T, obtaining a blank,
(3) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, wherein the high-temperature roasting temperature is 550 ℃, and the heat preservation time is 2 hours; the vacuum sintering temperature is 1150 ℃, the heat preservation time is 3 hours, the heat treatment is carried out after cooling, the cooling is that the natural cooling is carried out to 740 ℃, then the inert gas is introduced for cooling to 80 ℃, the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 900 ℃, and the heat preservation time is 2 hours; the temperature of the secondary heat treatment is 600 ℃, and the heat preservation time is 2 hours, so that the sintered neodymium-iron-boron magnet is obtained.
Wherein the catalyst is dibutyltin dilaurate, and the using amount of the catalyst is 0.5 percent of the mass of isocyanate ethyl acrylate; the initiator is azobisisobutyronitrile, and the using amount of the initiator is 0.25 percent of the mass of the isocyanate ethyl acrylate.
Example 3
(1) And (2) drying 100g of neodymium iron boron magnetic powder and a catalyst in vacuum, adding the dried mixture into 20g of isocyanate ethyl acrylate, heating and carrying out reflux reaction for 30min under the protection of nitrogen, mechanical stirring and assistance of ultrasonic waves, adding an initiator, continuing reflux reaction for 2h, cooling after the reaction is finished, adding water, stirring, carrying out suction filtration, washing with ethanol, and drying in vacuum to obtain the modified neodymium iron boron magnetic powder.
(2) Carrying out orientation compression on the modified neodymium iron boron magnetic powder by a magnetic field, wherein the magnetic field adopts a direct current pulse magnetic field, the pressure of the magnetic field is 2.0T, obtaining a blank,
(3) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, wherein the high-temperature roasting temperature is 600 ℃, and the heat preservation time is 1.5 hours; the vacuum sintering temperature is 1050 ℃, the heat preservation time is 3 hours, the heat treatment is carried out after cooling, the cooling is that the natural cooling is carried out to 710 ℃, then the inert gas is introduced for cooling to 60 ℃, the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 900 ℃, and the heat preservation time is 2 hours; the temperature of the secondary heat treatment is 550 ℃, and the heat preservation time is 3 hours, so that the sintered neodymium iron boron magnet is obtained.
Wherein the catalyst is stannous octoate, and the using amount of the catalyst is 0.5 percent of the mass of isocyanate ethyl acrylate; the initiator is azobisisoheptonitrile, and the using amount of the initiator is 0.25 percent of the mass of isocyanate ethyl acrylate.
Comparative example 1
Comparative example 1 was obtained by replacing the isocyanate ethyl acrylate in example 3 with methacryloxypropyltrimethoxysilane and methyl methacrylate.
(1) Adding 100g of neodymium iron boron magnetic powder into 100mL of tetrahydrofuran solution of 0.5 wt% of methacryloxypropyl trimethoxy silane, heating under the protection of nitrogen, mechanical stirring and the assistance of ultrasonic waves for reflux reaction for 30min, adding 20g of methyl methacrylate and an initiator, continuing reflux reaction for 2h, cooling after the reaction is finished, carrying out suction filtration, washing with ethanol, and carrying out vacuum drying to obtain the modified neodymium iron boron magnetic powder.
(2) Carrying out orientation compression on the modified neodymium iron boron magnetic powder through a magnetic field, wherein the magnetic field adopts a direct current pulse magnetic field, the pressure of the magnetic field is 2.0T, obtaining a blank,
(3) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, wherein the high-temperature roasting temperature is 600 ℃, and the heat preservation time is 1.5 hours; the vacuum sintering temperature is 1050 ℃, the heat preservation time is 3h, the heat treatment is carried out after cooling, the cooling is naturally cooled to 710 ℃, then inert gas is introduced for cooling to 60 ℃, the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 900 ℃, and the heat preservation time is 2 h; the temperature of the secondary heat treatment is 550 ℃, and the heat preservation time is 3 hours, so that the sintered neodymium iron boron magnet is obtained.
Wherein the initiator is azobisisoheptonitrile, and the dosage is 0.25% of the mass of the methyl methacrylate.
Comparative example 2
Comparative example 2 was obtained by replacing the isocyanate ethyl acrylate of example 3 with vinyltrimethoxysilane and styrene.
(1) Adding 100g of neodymium iron boron magnetic powder into 100mL of toluene solution of vinyl trimethoxy silane with the mass concentration of 0.5 wt%, heating and carrying out reflux reaction for 30min under the protection of nitrogen and under the assistance of mechanical stirring and ultrasonic waves, adding 20g of styrene and an initiator, continuing reflux reaction for 2h, cooling after the reaction is finished, carrying out suction filtration, washing with ethanol, and carrying out vacuum drying to obtain the modified neodymium iron boron magnetic powder.
(2) Carrying out orientation compression on the modified neodymium iron boron magnetic powder by a magnetic field, wherein the magnetic field adopts a direct current pulse magnetic field, the pressure of the magnetic field is 2.0T, obtaining a blank,
(3) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, wherein the high-temperature roasting temperature is 600 ℃, and the heat preservation time is 1.5 hours; the vacuum sintering temperature is 1050 ℃, the heat preservation time is 3 hours, the heat treatment is carried out after cooling, the cooling is that the natural cooling is carried out to 710 ℃, then the inert gas is introduced for cooling to 60 ℃, the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 900 ℃, and the heat preservation time is 2 hours; the temperature of the secondary heat treatment is 550 ℃, and the heat preservation time is 3 hours, so that the sintered neodymium iron boron magnet is obtained.
Wherein the initiator is azobisisoheptonitrile, and the dosage is 0.25% of the mass of styrene.
Comparative example 3
The step (1) in example 3 was deleted, that is, the neodymium iron boron magnetic powder was not subjected to coating modification, to obtain comparative example 3.
(1) Carrying out orientation compression on the neodymium iron boron magnetic powder by a magnetic field, wherein the magnetic field adopts a direct current pulse magnetic field, the pressure of the magnetic field is 2.0T, obtaining a blank,
(2) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, wherein the high-temperature roasting temperature is 600 ℃, and the heat preservation time is 1.5 hours; the vacuum sintering temperature is 1050 ℃, the heat preservation time is 3h, the heat treatment is carried out after cooling, the cooling is naturally cooled to 710 ℃, then inert gas is introduced for cooling to 60 ℃, the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 900 ℃, and the heat preservation time is 2 h; the temperature of the secondary heat treatment is 550 ℃, and the heat preservation time is 3 hours, so that the sintered neodymium iron boron magnet is obtained.
The modified ndfeb magnetic powder prepared in the step (1) in examples 1 to 3 and comparative examples 1 to 2 and the ndfeb magnetic powder used in the step (1) in comparative example 3 were left in the same air environment for 7 days before orientation press molding, and then subjected to subsequent corresponding orientation press molding, high-temperature baking, vacuum sintering and heat treatment, wherein the orientation press molding was an open press. The magnetic properties and oxygen content of the prepared sintered nd-fe-b magnet were measured, and the results are shown in table 1.
The magnetic performance of the magnet is measured by using an HS-40 type B-H loop measuring instrument, the oxygen content of the magnet is measured by using an IRO-I oxygen measuring instrument, the measurement is carried out for three times in parallel, and the average value is taken.
TABLE 1
| Remanence (kGs) | Coercive force (kOe) | Magnetic energy product (MGOe) | Oxygen content (ppm) | |
| Example 1 | 12.53 | 16.81 | 43.70 | 502 |
| Example 2 | 12.51 | 16.82 | 43.74 | 419 |
| Example 3 | 12.50 | 16.81 | 43.72 | 345 |
| Comparative example 1 | 12.47 | 16.73 | 43.68 | 627 |
| Comparative example 2 | 12.45 | 16.78 | 43.67 | 683 |
| Comparative example 3 | 12.52 | 16.82 | 43.72 | 1268 |
As can be seen from table 1, the use of ethyl isocyanate acrylate as a modifier in examples 1 to 3 of the present invention enables further reduction of the oxygen content of the sintered ndfeb magnet, without causing a significant decrease in the magnetic properties of the sintered ndfeb magnet, compared to the use of methacryloxypropyltrimethoxysilane and methyl methacrylate as modifiers in comparative example 1.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are given by way of illustration of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, and such changes and modifications are within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. A method for reducing the oxygen content of a sintered NdFeB magnet is characterized by comprising the following steps:
(1) vacuum drying neodymium iron boron magnetic powder and a catalyst, adding the mixture into isocyanate ethyl acrylate, heating and carrying out reflux reaction under the protection of nitrogen, mechanical stirring and ultrasonic assistance, adding an initiator, continuing reflux reaction, cooling after the reaction is finished, adding water, stirring, carrying out suction filtration, washing with ethanol, and vacuum drying to obtain modified neodymium iron boron magnetic powder;
(2) carrying out orientation compression on the modified neodymium iron boron magnetic powder through a magnetic field to obtain a blank;
(3) and (4) sequentially carrying out high-temperature roasting and vacuum sintering on the blank, cooling and carrying out heat treatment to obtain the sintered neodymium-iron-boron magnet.
2. The method of claim 1, wherein: the mass ratio of the neodymium iron boron magnetic powder to the isocyanate ethyl acrylate is 100 (10-20).
3. The method of claim 1, wherein: the catalyst is stannous octoate or dibutyltin dilaurate.
4. The method of claim 1, wherein: the dosage of the catalyst is 0.1-1% of the mass of the isocyanate ethyl acrylate.
5. The method of claim 1, wherein: the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
6. The method of claim 1, wherein: the using amount of the initiator is 0.05-0.5% of the mass of the isocyanate ethyl acrylate.
7. The method of claim 1, wherein: the magnetic field adopts a direct current pulse magnetic field, and the pressure of the magnetic field is 1.8-2.0T.
8. The method of claim 1, wherein: the high-temperature roasting temperature is 500-600 ℃, and the heat preservation time is 1-3 h; the temperature of the vacuum sintering is 1050-.
9. The method of claim 1, wherein: the cooling is naturally cooling to 700-800 ℃ and then introducing inert gas to cool to below 100 ℃.
10. The method of claim 1, wherein: the heat treatment is divided into two stages, the temperature of the first-stage heat treatment is 850-; the temperature of the secondary heat treatment is 500-600 ℃, and the heat preservation time is 1-3 h.
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