CN115642029A - Method for preparing rare earth permanent magnet - Google Patents
Method for preparing rare earth permanent magnet Download PDFInfo
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- CN115642029A CN115642029A CN202210367974.8A CN202210367974A CN115642029A CN 115642029 A CN115642029 A CN 115642029A CN 202210367974 A CN202210367974 A CN 202210367974A CN 115642029 A CN115642029 A CN 115642029A
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 86
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000005324 grain boundary diffusion Methods 0.000 claims abstract description 128
- 239000000126 substance Substances 0.000 claims abstract description 109
- 229910001172 neodymium magnet Inorganic materials 0.000 claims abstract description 43
- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 36
- 150000003624 transition metals Chemical class 0.000 claims abstract description 36
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 35
- 239000001257 hydrogen Substances 0.000 claims abstract description 35
- -1 rare earth metal hydrogen compound Chemical class 0.000 claims abstract description 35
- 238000000576 coating method Methods 0.000 claims abstract description 28
- 239000011248 coating agent Substances 0.000 claims abstract description 26
- 238000010438 heat treatment Methods 0.000 claims abstract description 24
- 238000009792 diffusion process Methods 0.000 claims abstract description 12
- 230000000087 stabilizing effect Effects 0.000 claims abstract description 5
- 238000004519 manufacturing process Methods 0.000 claims description 18
- 238000002156 mixing Methods 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- 229910052771 Terbium Inorganic materials 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 239000013078 crystal Substances 0.000 claims description 7
- 239000012300 argon atmosphere Substances 0.000 claims description 6
- 150000002739 metals Chemical class 0.000 claims description 6
- 239000007921 spray Substances 0.000 claims description 2
- 239000000725 suspension Substances 0.000 claims description 2
- 238000002844 melting Methods 0.000 description 19
- 230000008018 melting Effects 0.000 description 17
- 229910045601 alloy Inorganic materials 0.000 description 13
- 239000000956 alloy Substances 0.000 description 13
- 229910052782 aluminium Inorganic materials 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 8
- 239000000843 powder Substances 0.000 description 5
- 230000006641 stabilisation Effects 0.000 description 5
- 238000011105 stabilization Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910052692 Dysprosium Inorganic materials 0.000 description 2
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 2
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- FNCIDSNKNZQJTJ-UHFFFAOYSA-N alumane;terbium Chemical compound [AlH3].[Tb] FNCIDSNKNZQJTJ-UHFFFAOYSA-N 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 2
- 229910052733 gallium Inorganic materials 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- HMUNWXXNJPVALC-UHFFFAOYSA-N 1-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)C(CN1CC2=C(CC1)NN=N2)=O HMUNWXXNJPVALC-UHFFFAOYSA-N 0.000 description 1
- LDXJRKWFNNFDSA-UHFFFAOYSA-N 2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound C1CN(CC2=NNN=C21)CC(=O)N3CCN(CC3)C4=CN=C(N=C4)NCC5=CC(=CC=C5)OC(F)(F)F LDXJRKWFNNFDSA-UHFFFAOYSA-N 0.000 description 1
- HGMITUYOCPPQLE-UHFFFAOYSA-N 3-quinuclidinyl benzilate Chemical compound C1N(CC2)CCC2C1OC(=O)C(O)(C=1C=CC=CC=1)C1=CC=CC=C1 HGMITUYOCPPQLE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002483 hydrogen compounds Chemical class 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Images
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
- H01F41/0293—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 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
-
- 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
- H01F1/0536—Alloys characterised by their composition containing rare earth metals sintered
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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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
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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)
- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Abstract
The invention relates to a method for preparing a rare earth permanent magnet, which comprises the following steps: preparing a NdFeB sintered magnet; preparing a first grain boundary diffusion substance containing a rare earth metal hydrogen compound; preparing a second interface diffusion substance including a hydrogen compound mixed with a rare earth metal and a transition metal; coating a first grain boundary diffusion substance or a second grain boundary diffusion substance on the surface of the NdFeB sintered magnet to form a grain boundary diffusion coating; diffusing the first grain boundary diffusion substance or the second grain boundary diffusion substance to the grain boundary of the NdFeB sintered magnet by heat treatment; and stabilizing the NdFeB sintered magnet in which the first grain boundary diffusion substance or the second grain boundary diffusion substance is diffused to the grain boundary by the heat treatment.
Description
Technical Field
The present invention relates to a method of manufacturing a rare earth permanent magnet, and to a method of manufacturing a rare earth permanent magnet in which alloy powder containing a rare earth element is coated and then heat treatment is performed to diffuse the rare earth element into the inside of grain boundaries of a sintered magnet. In more detail, the present invention relates to a method for producing a rare earth permanent magnet in which a rare earth metal is diffused into the inside of grain boundaries of an NdFeB-based sintered magnet by using an alloy powder containing the rare earth metal and a transition metal for lowering the melting point of the rare earth metal, thereby improving the coercive force.
Background
In general, a rare earth permanent magnet is a magnet excellent in magnetic force such as an R — Fe-B sintered magnet (where "R" is a rare earth element or a combination of rare earth elements such as neodymium (Nd), dysprosium (Dy), terbium (Tb)), and the like, and can realize high power and downsizing of a motor, and thus the range of utilization is gradually expanding.
In particular, in recent years, as the demand for hybrid vehicles or electric vehicles has increased, the demand for rare earth permanent magnets that can improve the magnetic force by 3 to 5 times as compared to existing ferrite magnets is expected to further increase.
In addition, the magnetic properties of a magnet can be expressed by a remanence determined by the fraction, density and degree of magnetic orientation of the main phase of a rare earth permanent magnet, and a coercivity that is the durability of the magnetic force of the magnet due to an external magnetic field or heat, which has a decisive relationship with the microstructure of the structure, and is determined by the refinement of the crystal grain size or uniform distribution at the grain boundary.
In addition, as a method for producing a permanent magnet, a method using a magnet grain refinement technique and a grain boundary diffusion technique, particularly a grain boundary diffusion technique, is generally used because the amount of rare earth metal used can be reduced.
The grain boundary diffusion process mainly comprises the following steps: preparing a grain boundary diffusion substance containing a rare earth metal, coating the prepared grain boundary diffusion substance on the surface of the sintered magnet, and then performing heat treatment on the sintered magnet, thereby diffusing the grain boundary diffusion substance into the interior of grains of the sintered magnet. However, since the melting point of the grain boundary diffusion substance is set to 1000 ℃ or higher, which is 400 ℃ or higher than the melting point of Nd-rich (Nd-rich) as crystal grains, there is a problem that the grain boundary diffusion substance is not easily diffused into the inside of the grain boundary.
The above description of the background art is only for the purpose of improving understanding of the background of the invention and should not be taken as corresponding to the prior art known to those of ordinary skill in the art.
[ Prior art documents ]
[ patent document ]
(patent document 1) KR10-2012-0124039A (11/12/2012)
Disclosure of Invention
Technical problem to be solved
The present invention has been made to solve the problems, and an object of the present invention is to provide a method of manufacturing a rare earth permanent magnet, in which a second grain boundary diffusion substance containing a rare earth metal and a transition metal is prepared, the second grain boundary diffusion substance having a melting point lower than that of a first grain boundary diffusion substance containing only a rare earth metal is coated, and a plurality of second grain boundary diffusion substances having different mixing ratios of a rare earth metal and a transition metal are prepared and coated to have a concentration gradient, thereby allowing the rare earth metal to be smoothly diffused into the inside of crystal grains.
Technical scheme
The method for producing a rare earth permanent magnet of the present invention for achieving the above object includes the steps of: preparing a NdFeB sintered magnet; preparing a first grain boundary diffusion substance containing a rare earth metal hydrogen compound; preparing a second interface diffusion substance including a hydrogen compound mixed with a rare earth metal and a transition metal; coating a first grain boundary diffusion substance or a second grain boundary diffusion substance on the surface of the NdFeB sintered magnet to form a grain boundary diffusion coating; diffusing the first grain boundary diffusion substance or the second grain boundary diffusion substance to the grain boundary of the NdFeB sintered magnet by heat treatment; and stabilizing the NdFeB sintered magnet in which the first grain boundary diffusion substance or the second grain boundary diffusion substance is diffused to the grain boundary by the heat treatment.
In the step of preparing the first grain boundary diffusion substance and the step of preparing the second grain boundary diffusion substance, the rare earth metal may be one or more metals selected from Tb, dy, ho, ga, and the transition metal may be one or more metals selected from Co, cu, al, ga, fe, ni, zn.
In the step of preparing the second crystal boundary diffusion substance, the mixing ratio of the rare earth metal and the transition metal may be 60 to 95.
In the step of preparing the second grain boundary diffusion substance, two or more kinds of second grain boundary diffusion substances different in a mixing ratio of the rare earth metal and the transition metal may be prepared.
In the step of applying the grain boundary diffusion substance to form the grain boundary diffusion coating, the second grain boundary diffusion substance may be applied in the order of a ratio of the transition metal from high to low among the two or more prepared second grain boundary diffusion substances, and finally the first grain boundary diffusion substance may be applied.
In the step of preparing the first grain boundary diffused species and the step of preparing the second grain boundary diffused species, the first grain boundary diffused species may be formed by mixing a rare earth metal hydrogen compound with ethanol, and the second grain boundary diffused species may be formed by mixing a hydrogen compound mixed with a rare earth metal and a transition metal with ethanol.
In the step of forming the grain boundary diffusion coating, the first grain boundary diffusion substance or the second grain boundary diffusion substance may be coated on the surface of the NdFeB sintered magnet by an ultrasonic spray method, a suspension adhesion method, or a roll coating method to form the grain boundary diffusion coating.
In the step of diffusing the first grain boundary diffusion substance or the second grain boundary diffusion substance to the grain boundaries of the NdFeB sintered magnet by heat treatment, the first grain boundary diffusion substance or the second grain boundary diffusion substance may be diffused to the grain boundaries of the NdFeB sintered magnet by heating to 600 ℃ or more and 900 ℃ or less in a vacuum or an argon atmosphere.
In the step of stabilizing the NdFeB sintered magnet, the NdFeB sintered magnet may be stabilized by heating to 400 ℃ or higher and 900 ℃ or lower in a vacuum or an argon atmosphere.
Advantageous effects
According to the method for preparing the rare earth permanent magnet, the rare earth metal is effectively diffused along the grain boundary of the sintered magnet, so that the coercive force of the prepared rare earth permanent magnet can be improved.
Drawings
Fig. 1 is a flowchart illustrating a method of manufacturing a rare earth permanent magnet according to an embodiment of the present invention.
Fig. 2 is a schematic view illustrating a method of manufacturing a rare earth permanent magnet according to one embodiment of the present invention.
Fig. 3 is a graph showing the melting point of terbium-aluminum alloy.
Description of reference numerals
10: ndFeB sintered magnet
100: grain boundaries
200: grain boundary diffusion material
300: grain boundaries diffused with grain boundary diffusion substances
Detailed Description
Hereinafter, specific details of the above object and the problem to be solved will be described in detail with reference to the drawings. In addition, in understanding the aspects of the present invention, when a detailed description of a known technology in the same field does not help to understand the core contents of the present invention, the description is omitted, and the technical idea of the present invention is not limited thereto, and those skilled in the art can variously implement by change.
Fig. 1 is a flowchart illustrating a method of manufacturing a rare earth permanent magnet according to an embodiment of the present invention, and fig. 2 is a schematic view illustrating a method of manufacturing a rare earth permanent magnet by grain boundary diffusion. Briefly explaining a method of manufacturing a rare earth permanent magnet by grain boundary diffusion with reference to fig. 2, a sintered magnet 10 including grain boundaries 100 is prepared, and grain boundaries 300 into which a grain boundary diffusion material is diffused are formed when a grain boundary diffusion material 200 is applied to the surface thereof and heated, thereby manufacturing the rare earth permanent magnet.
As shown in fig. 1, the method for producing a rare earth permanent magnet of the present invention for achieving the above object includes the steps of: a step S100 of preparing an NdFeB sintered magnet; a step S200 of preparing a first grain boundary diffusion substance containing a rare earth metal hydrogen compound; a step S300 of preparing a second grain boundary diffusion substance containing a hydrogen compound mixed with a rare earth metal and a transition metal; a step S400 of coating a first grain boundary diffusion substance or a second grain boundary diffusion substance on the surface of the NdFeB sintered magnet to form a grain boundary diffusion coating; a step S500 of diffusing the first grain boundary diffusion substance or the second grain boundary diffusion substance to the grain boundary of the NdFeB sintered magnet by heat treatment; and a step S600 of stabilizing the NdFeB sintered magnet in which the first grain boundary diffusion substance or the second grain boundary diffusion substance is diffused to the grain boundary by the heat treatment.
In step S100 of preparing a NdFeB sintered magnet, the NdFeB alloy is prepared by preparing in weight ratio and heating to 1300 to 1550 ℃ using a high-frequency melting furnace to melt it, and then preparing using a strip casting method such that the prepared NdFeB sintered magnet 10 contains rare earth elements containing dysprosium (Dy), terbium (Tb), neodymium (Nd), and praseodymium (Pr) in a sum of 30 to 35% by weight, transition metals containing cobalt (Co), aluminum (Al), copper (Cu), gallium (Ga), zirconium (Zr), niobium (Nb), 10% by weight, and the balance iron (Fe) in a sum of 0 to 10% by weight.
After preparing the NdFeB alloy, the NdFeB alloy is coarsely pulverized by hydrogenation and dehydrogenation, and then finely ground by a Jet mill (Jet-mill), thereby producing NdFeB powder, in which case the diameter of the NdFeB powder is preferably formed to be 3 to 5 μm.
As described above, after NdFeB powder is prepared, sintering and heat treatment are performed using a magnetic field forming machine in which the magnetic field direction is perpendicular to the forming direction, thereby producing a NdFeB sintered magnet.
The step S100 of preparing the NdFeB sintered magnet is preferably prepared in an inert atmosphere filled with nitrogen (N) gas or argon (Ar) gas, because the degradation of the magnetic characteristics of the NdFeB sintered magnet prepared by minimizing impurities such as carbon (C) or oxygen (O) can be minimized.
As described above, after preparing the NdFeB sintered magnet, the first grain boundary diffusion substance containing the rare earth metal hydrogen compound and the second grain boundary diffusion substance containing the hydrogen compound in which the rare earth metal and the transition metal are mixed are prepared. In this case, the rare earth metal may be one or more metals selected from Tb, dy, ho, and Ga, and the transition metal may be one or more metals selected from Co, cu, al, ga, fe, ni, and Zn.
The first grain boundary diffused material was prepared by mixing a rare earth metal hydrogen compound with ethanol at a weight ratio of 50. The second interface diffusion substance is prepared by mixing a hydrogen compound mixed with a rare earth metal and a transition metal with ethanol at a weight ratio of 50. The hydrogen compound contained in the first grain boundary diffusion substance is a hydrogen compound of a rare earth metal (for example, terbium hydride) which is a chemical combination of a rare earth metal and hydrogen, but the hydrogen compound contained in the second grain boundary diffusion substance is a hydrogen compound of an alloy of a rare earth metal and a transition metal (for example, a hydrogen compound of an alloy of 78% terbium and 22% aluminum in atomic percentage). Specifically, an alloy of a rare earth metal and a transition metal can be formed by mixing in an atomic percentage of 60. Further, two or more second grain boundary diffusion substances different in the mixing ratio of the rare earth metal and the transition metal can be prepared.
After preparing the first and second grain boundary diffusion materials, the prepared grain boundary diffusion materials are coated to form a grain boundary diffusion coating. At this time, of the two or more prepared second grain boundary diffusion substances, the second grain boundary diffusion substances are coated in order of the ratio of the transition metal from high to low, and finally the first grain boundary diffusion substance is coated, so that the second grain boundary diffusion substances are coated in order of the highest content of the transition metal. The coating thickness is preferably 10 to 30 μm.
Thereby, the second grain boundary diffusion substance is coated on the surface of the NdFeB sintered magnet in the order of the transition metal ratio from high to low, thereby forming a grain boundary diffusion coating. The first grain boundary diffusion substance is coated at the extreme end, so that a grain boundary diffusion coating layer can be formed. However, there is no problem in not using the first grain boundary diffusion substance according to circumstances, and there is no problem in diffusing the rare earth metal to the grain boundary of the sintered magnet even if only the second grain boundary diffusion substance is prepared and used.
That is, in the present invention, the rare earth metal is diffused to the grain boundary of the sintered magnet by making the concentration of the transition metal contained in the second grain boundary diffusion substance form a gradient. The alloy containing the transition metal is used in order to lower the melting point of the rare earth metal. Of course, in the case of an alloy, even if it is prepared with a low-melting metal and a high-melting metal at a ratio of 50. However, when the melting point of the alloy is measured according to the ratio of the rare earth metal to the transition metal, the optimum mixing ratio can be obtained. For example, terbium, which is typically used as a rare earth metal, has a melting point of 1356 ℃ and aluminum, which is a transition metal, has a melting point of 660 ℃.
Fig. 3 is a graph showing the melting point of terbium-aluminum alloy.
In order to enhance the coercive force, the amount of terbium is preferably larger than that of aluminum, and as shown in fig. 3, when terbium and aluminum metals are alloyed at an atomic ratio of 78. Therefore, when terbium and aluminum are used for preparing the second interface diffusion substance, the second interface diffusion substance may be preferably prepared by alloying in an atomic ratio of 78.
In addition, as an example of the gradient coating, the second grain boundary diffusion substance and the first grain boundary diffusion substance may be coated as follows.
Coating a second crystal boundary diffusion substance comprising an alloy of mixed terbium and aluminum in 78.
After the grain boundary diffusion substance is coated as described above, the first grain boundary diffusion substance or the second grain boundary diffusion substance is diffused to the grain boundary of the NdFeB sintered magnet by heat treatment. The heat treatment may be performed by heating to 600 ℃ or higher and 900 ℃ or lower in a vacuum or an argon atmosphere. The heat treatment is usually carried out for about 6 hours.
After the heat treatment, the NdFeB sintered magnet was stabilized. The stabilization may be performed by heating to 400 ℃ or higher and 900 ℃ or lower in a vacuum or an argon atmosphere. Stabilization is usually carried out for about 2 hours.
Hereinafter, various embodiments according to the method of manufacturing a rare earth permanent magnet as described above are presented, thereby more specifically disclosing the present invention.
All comparisonsExamples and examples using NdFeB sintered magnets processed to 12.5mm × 12.5mm × 5mm, a first grain boundary diffusion substance was prepared by mixing Tb hydrogen compound and ethanol at a weight ratio of 50, and a second grain boundary diffusion substance was prepared by mixing (1) Tb hydrogen 78 Al 22 Hydrogen compound, (2) Tb 85 Al 15 Hydrogen compound, (3) Tb 89 Al 11 Hydrogen compound, (4) Tb 95 Al 5 Hydrogen compound, (5) Tb 62.5 Co 37.5 Hydrogen compound, (6) Tb 90 Ga 10 Hydrogen compound, (7) Tb 88 Fe 12 Hydrogen compound, (8) Tb 64 Cu 36 Any one or more of the hydrogen compounds and ethanol in a weight ratio of 50.
Hereinafter, for convenience of description of the name, "hydrogen compound" is omitted. E.g. Tb 78 Al 22 The hydrogen compound is represented by Tb 78 Al 22 And the Tb hydrogen compound is represented by Tb.
[ Table 1]
Comparative example 1 is a magnet prepared using only the first grain boundary diffusion substance containing no transition metal, and example 1-1 is a magnet prepared using only Tb in the second grain boundary diffusion substance 78 Al 22 The magnet prepared, example 1-2, was prepared using Tb 78 Al 22 And Tb prepared magnet. The coercive force of example 1-1 was higher than that of comparative example 1 because the melting point of the grain boundary diffusion substance was lowered by about 500 ℃ or more, thereby stably performing grain boundary diffusion, and the coercive force of example 1-2 was higher than that of example 1-1 because the melting point of the grain boundary diffusion substance was sufficiently lowered while the content of Tb in the grain boundary diffusion substance was high.
[ Table 2]
Table 2 shows the preparation by changing the type of transition metal and the mixing ratio with terbiumThe result of preparing rare earth permanent magnet. Tb 78 Al 22 、Tb 62.5 Co 37.5 、Tb 90 Ga 10 、Tb 88 Fe 12 、Tb 64 Cu 36 The respective melting points are 880 ℃, 700 ℃, 880 ℃, 847 ℃ and 730 ℃. According to the above examples, it is known that applying a grain boundary diffusion substance having a low melting point thereunder is effective for increasing the coercive force. It is also found that the grain boundary diffusion material having a high Tb content and the grain boundary diffusion material having a low melting point do not both increase the magnetic properties in the same manner.
[ Table 3]
The results of preparing rare earth permanent magnets by subdividing the coating interval and using a plurality of second grain boundary diffusion substances differing in the concentration of aluminum as a transition metal are shown in table 3. The diffusion conditions were those heated at 900 ℃ for 6 hours in all examples, and the stabilization conditions were those heated at 500 ℃ for 2 hours in all examples. From example 3-1, example 3-2, and example 3-3 of the above results, it is understood that when the coating is performed so that the concentration of aluminum has a gradient in four or more layers, the coercive force is saturated and thus does not increase. In view of this, it can be considered that forming a three-to four-layer coating is the most economical method.
[ Table 4]
The results of preparing the rare earth permanent magnet by performing coating of the grain boundary diffusion substance four times identically to form a coating layer of four layers in total and changing the diffusion and stabilization conditions are shown in table 4. When comparative example 1 was compared with examples 4-1 to 4-7 and 3-2, the optimum diffusion temperature was 900 ℃ as in comparative example 1 when the 60 μm first grain boundary diffusion material was coated, but the optimum temperature was 700 ℃ and was decreased by about 200 ℃ when the coating was formed in such a manner that the Al content had a gradient. This means that the second grain boundary diffusion substance containing Al diffuses into the crystal grains at a relatively low temperature because of its low melting point. From the results shown in table 4, the optimum temperature for the stabilization temperature was 500 ℃.
As described above, in the method of producing a rare earth permanent magnet of the present invention, a hydrogen compound of an alloy in which a rare earth metal and a transition metal are mixed is used as a second grain boundary diffusion substance, and a grain boundary diffusion coating is formed in such a manner that the concentration of the transition metal has a gradient, whereby the rare earth metal can be diffused to the grain boundary of the sintered magnet. Therefore, the rare earth metal is effectively diffused along the grain boundary of the sintered magnet, so that the coercive force of the prepared rare earth permanent magnet can be improved.
As described above, although the present invention has been described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.
Claims (9)
1. A method of making a rare earth permanent magnet comprising the steps of:
preparing an NdFeB sintered magnet;
preparing a first grain boundary diffusion substance containing a rare earth metal hydrogen compound;
preparing a second interface diffusion substance including a hydrogen compound mixed with a rare earth metal and a transition metal;
coating a first grain boundary diffusion substance or a second grain boundary diffusion substance on the surface of the NdFeB sintered magnet to form a grain boundary diffusion coating;
diffusing the first grain boundary diffusion substance or the second grain boundary diffusion substance to the grain boundary of the NdFeB sintered magnet by heat treatment; and
the NdFeB sintered magnet in which the first grain boundary diffusion substance or the second grain boundary diffusion substance is diffused to the grain boundary by the heat treatment is stabilized.
2. The method of producing a rare earth permanent magnet according to claim 1, wherein in the step of producing the first grain boundary diffusion substance and the step of producing the second grain boundary diffusion substance, the rare earth metal is one or more metals selected from Tb, dy, ho, ga, and the transition metal is one or more metals selected from Co, cu, al, ga, fe, ni, zn.
3. The method for producing a rare earth permanent magnet according to claim 1, wherein in the step of producing the second crystal boundary diffusion substance, a mixing ratio of the rare earth metal and the transition metal is 60 to 95.
4. The method of producing a rare earth permanent magnet according to claim 3, wherein in the step of producing the second grain boundary diffusion substance, two or more kinds of second grain boundary diffusion substances different in a mixing ratio of the rare earth metal and the transition metal are produced.
5. The method of producing a rare earth permanent magnet according to claim 4, wherein in the step of applying a grain boundary diffusion substance to form a grain boundary diffusion coating, the second grain boundary diffusion substance is applied in the order of a ratio of transition metals from high to low among the two or more second grain boundary diffusion substances produced, and the first grain boundary diffusion substance is finally applied.
6. The method of producing a rare earth permanent magnet according to claim 1, wherein in the step of producing the first grain boundary diffusion substance and the step of producing the second grain boundary diffusion substance, the first grain boundary diffusion substance is formed by mixing a rare earth metal hydrogen compound with ethanol, and the second grain boundary diffusion substance is formed by mixing a hydrogen compound in which a rare earth metal and a transition metal are mixed with ethanol.
7. The method of manufacturing a rare earth permanent magnet according to claim 1, wherein in the step of forming the grain boundary diffusion coating, the first grain boundary diffusion substance or the second grain boundary diffusion substance is coated on the surface of the NdFeB sintered magnet by an ultrasonic spray method, a suspension adhesion method, or a roll coating method to form the grain boundary diffusion coating.
8. The method of producing a rare earth permanent magnet according to claim 1, wherein in the step of diffusing the first or second grain boundary diffusion substance to the grain boundary of the NdFeB sintered magnet by heat treatment, heating is performed in a vacuum or argon atmosphere to 600 ℃ or higher and 900 ℃ or lower, thereby diffusing the first or second grain boundary diffusion substance to the grain boundary of the NdFeB sintered magnet.
9. The method for producing a rare earth permanent magnet according to claim 1, wherein, in the step of stabilizing the NdFeB sintered magnet, the NdFeB sintered magnet is stabilized by heating to 400 ℃ or more and 900 ℃ or less in a vacuum or an argon atmosphere.
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