CN112992459A - Sintered neodymium-iron-boron magnetic material and preparation method thereof - Google Patents
Sintered neodymium-iron-boron magnetic material and preparation method thereof Download PDFInfo
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- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 100
- 239000000696 magnetic material Substances 0.000 title claims abstract description 70
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 238000002360 preparation method Methods 0.000 title abstract description 15
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 29
- 239000000956 alloy Substances 0.000 claims abstract description 29
- 238000005245 sintering Methods 0.000 claims abstract description 27
- 239000000843 powder Substances 0.000 claims abstract description 23
- 239000002994 raw material Substances 0.000 claims abstract description 20
- 238000005496 tempering Methods 0.000 claims abstract description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000001257 hydrogen Substances 0.000 claims abstract description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 13
- 238000001816 cooling Methods 0.000 claims abstract description 11
- 238000005266 casting Methods 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 238000005303 weighing Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 35
- 230000005291 magnetic effect Effects 0.000 claims description 19
- 229910052684 Cerium Inorganic materials 0.000 claims description 17
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 10
- 239000011362 coarse particle Substances 0.000 claims description 9
- 239000000047 product Substances 0.000 claims description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 6
- 230000008018 melting Effects 0.000 claims description 6
- 239000003963 antioxidant agent Substances 0.000 claims description 5
- 230000003078 antioxidant effect Effects 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 238000009694 cold isostatic pressing Methods 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 3
- 239000012467 final product Substances 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 238000000137 annealing Methods 0.000 claims 3
- 230000007797 corrosion Effects 0.000 abstract description 40
- 238000005260 corrosion Methods 0.000 abstract description 40
- 238000003723 Smelting Methods 0.000 abstract 2
- 238000000748 compression moulding Methods 0.000 abstract 1
- 239000012071 phase Substances 0.000 description 73
- 229910052779 Neodymium Inorganic materials 0.000 description 35
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 34
- 230000000052 comparative effect Effects 0.000 description 24
- 239000013078 crystal Substances 0.000 description 22
- 239000001301 oxygen Substances 0.000 description 13
- 229910052760 oxygen Inorganic materials 0.000 description 13
- 230000008569 process Effects 0.000 description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 12
- 229910052761 rare earth metal Inorganic materials 0.000 description 12
- 238000004519 manufacturing process Methods 0.000 description 10
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 150000002910 rare earth metals Chemical class 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 7
- 229910052796 boron Inorganic materials 0.000 description 7
- 230000004580 weight loss Effects 0.000 description 7
- 238000000465 moulding Methods 0.000 description 5
- 229910052802 copper Inorganic materials 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910000420 cerium oxide Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 238000005237 degreasing agent Methods 0.000 description 2
- 239000013527 degreasing agent Substances 0.000 description 2
- 238000000280 densification Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 238000010902 jet-milling Methods 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 230000005389 magnetism Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- PLDDOISOJJCEMH-UHFFFAOYSA-N neodymium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Nd+3].[Nd+3] PLDDOISOJJCEMH-UHFFFAOYSA-N 0.000 description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 229910002549 Fe–Cu Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical group [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 230000001808 coupling effect Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000005292 diamagnetic effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 229910001004 magnetic alloy Inorganic materials 0.000 description 1
- 239000006247 magnetic powder Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910000403 monosodium phosphate Inorganic materials 0.000 description 1
- 235000019799 monosodium phosphate Nutrition 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000007780 powder milling Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 238000007712 rapid solidification Methods 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 description 1
- 235000015393 sodium molybdate Nutrition 0.000 description 1
- 239000011684 sodium molybdate Substances 0.000 description 1
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000010998 test method Methods 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
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
- B22D11/0611—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by a single casting wheel, e.g. for casting amorphous metal strips or wires
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
- B22F3/04—Compacting only by applying fluid pressure, e.g. by cold isostatic pressing [CIP]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/023—Hydrogen absorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C30/00—Alloys containing less than 50% by weight of each constituent
- C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/044—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by jet milling
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- Manufacturing & Machinery (AREA)
- Fluid Mechanics (AREA)
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- Crystallography & Structural Chemistry (AREA)
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Abstract
The application relates to the field of magnetic materials, and particularly discloses a sintered neodymium-iron-boron magnetic material and a preparation method thereof. A sintered Nd-Fe-B magnetic material comprises PrNd30-40wt%, B1.5-1.8wt%, Ce15-17wt%, Ga2.5-3.5wt%, Zr0.1-0.3wt%, La0.1-0.3wt%, Cu0.1-0.3wt%, Al0.1-0.3wt%, Co0.9-1.2wt%, and the balance Fe and irremovable impurities; the preparation method comprises the following steps: the preparation method comprises the steps of weighing the raw materials in proportion, putting the raw materials into a vacuum smelting furnace for high-temperature smelting, rapidly casting the raw materials into alloy sheets by using a cooling roller, crushing the alloy sheets into powder by hydrogen and airflow, performing compression molding under vacuum to obtain pressed blanks, performing high-temperature sintering and tempering treatment, and finally performing air cooling. The sintered Nd-Fe-B magnetic material can be used for machines which are easy to corrode when working in open fields such as wind driven generators and the like, and has high corrosion resistance.
Description
Technical Field
The application relates to the field of magnetic materials, in particular to a sintered neodymium-iron-boron magnetic material and a preparation method thereof.
Background
The Nd-Fe-B is prepared from Nd, Fe and B2Fe14B) The formed tetragonal system crystal can be divided into sintered neodymium iron boron and bonded neodymium iron boron.
The sintered Nd-Fe-B permanent magnet has the advantages of high magnetic energy product, small volume, light weight and the like, and has been widely applied to the fields of national defense aviation, communication electronic medical treatment, machinery and the like. In recent years, due to the rapid development of energy-saving and environment-friendly industry in China, the output of rare earth permanent magnet motors applied to wind power generation, new energy automobiles, variable frequency air conditioners and the like is rapidly increased, the requirement on the comprehensive performance of sintered neodymium iron boron is higher and higher, and people have higher requirements on the magnetic performance of a magnet and the temperature stability and the corrosion resistance of the magnet.
Taking a wind driven generator as an example, because the wind driven generator works in the open field and is subjected to the tests of high temperature, severe cold, humidity and even salt fog, once corroded, corrosion products generated on the surface of the magnet not only can reduce the magnetic property of the magnet, but also can influence the service performance and the safety performance of the wind driven generator, so that the magnet applied to the wind driven generator is required to have higher corrosion resistance besides the magnetic property meeting the requirement.
Disclosure of Invention
In order to improve the corrosion resistance of the sintered neodymium-iron-boron magnetic material, the application provides the sintered neodymium-iron-boron magnetic material and a preparation method thereof.
In a first aspect, the present application provides a sintered nd-fe-b magnetic material, which adopts the following technical scheme:
a sintered Nd-Fe-B magnetic material, PrNd30-40wt%, B1.5-1.8wt%, Ce15-17wt%, Ga2.5-3.5wt%, Zr0.1-0.3wt%, La0.1-0.3wt%, Cu0.1-0.3wt%, Al0.1-0.3wt%, Co0.9-1.2wt%, and the balance Fe and non-removable impurities.
By adopting the technical scheme, elements such as Cu, Al and the like are added, so that an intermetallic compound is formed at a crystal boundary to form an Nd-Fe-Cu intergranular phase and an Nd-Fe-Al intergranular phase, and the original boron-rich phase is replaced, so that the growth of tetragonal phase grains is prevented, the grains are refined, the microstructure of the magnet is improved, and the coercive force is improved. In addition, the intergranular phase formed will partially replace the neodymium-rich phase, reducing the potential difference between the phases of the magnet.
Meanwhile, the texture of the sintered Nd-Fe-B magnetic material is smooth and can surround the main phase, so that a large amount of stable intermetallic compounds can greatly improve the corrosion resistance and the high temperature resistance of the sintered Nd-Fe-B magnetic material.
Cobalt forms Nd in Nd-rich grain boundary phase3The intergranular phase of Co partially replaces the intergranular neodymium-rich phase, thereby reducing the activity of the intergranular neodymium-rich phase and improving the corrosion resistance of the sintered neodymium-iron-boron magnetic material.
In addition, Co replaces the position of Fe in the main phase, so that the oxidation corrosion behavior of the neodymium iron boron magnetic material at the temperature of more than 200 ℃ can be greatly inhibited.
The content of the rare earth elements in the raw materials is high, and the bending strength of the neodymium iron boron magnet can be improved and the mechanical property of the neodymium iron boron magnet can be improved due to the addition of the rare earth elements.
In addition, the microstructure of the neodymium-iron-boron magnet mainly comprises a neodymium-iron-boron phase, a neodymium-rich phase, a boron-rich phase, neodymium oxide, an alpha-Fe phase and an external dopant. The Nd-Fe-B phase is polygonal, the Nd-rich phase is distributed along the grain boundary or the corner of the grain boundary, and the B-rich phase exists in isolated blocks or particles.
The neodymium-rich phase has three distribution states, namely a blocky neodymium-rich phase, a lamellar neodymium-rich phase and a dispersed neodymium-rich phase which can be observed in individual crystal grains. The blocky neodymium-rich phase is embedded on the boundary of the neodymium iron boron crystal grains; the lamellar neodymium-rich phase is continuously distributed at the grain boundary and the grain corner and has different thicknesses; the quantity of dispersed neodymium-rich phases is small and is distributed in the neodymium-iron-boron crystal grains.
The rich neodymium phase can promote the sintering of the neodymium iron boron magnet and play a role in sintering aid, the rich neodymium phase starts to melt at about 650 ℃, a foundation is laid for the densification of the neodymium iron boron magnet, and the densification of the neodymium iron boron magnet can be promoted. Meanwhile, the lamellar neodymium-rich phase continuously distributed along the crystal boundary can play a role in exchange coupling, so that the coercive force of the neodymium-iron-boron magnet can be improved, the volume fraction of the neodymium-iron-boron phase cannot be occupied, and the magnetic energy product is hardly influenced.
The boron-rich phase is mostly present in the form of polygonal particles at the corners of grain boundaries or at the neodymium iron boron grain boundaries, and fine particulate boron-rich phases are precipitated inside the individual neodymium iron boron grains.
The sintered Nd-Fe-B magnetic material is easy to be oxidized, namely chemically corroded. The neodymium-iron-boron phase, the neodymium-rich phase and the boron-rich phase have different oxidation capacities, the boron-rich phase and the neodymium-rich phase have stronger oxidation capacities, and the neodymium-rich phase and the boron-rich phase are generally distributed at a grain boundary. Thus, oxidation of the ndfeb magnet generally starts from grain boundaries, forming grain boundary corrosion.
When the microstructure of the neodymium iron boron magnet has fine and uniform neodymium iron boron phase crystal grains, the neodymium-rich phase is less distributed on the main phase crystal grain boundary and mainly concentrated on the triangular crystal boundary, the intergranular corrosion of the neodymium-rich phase of the magnet can be effectively inhibited, and the corrosion resistance of the magnet is improved.
With the increase of the content of the rare earth, the corrosion speed of the sintered neodymium iron boron magnetic material is increased. Therefore, the chemical properties, distribution state and content of the neodymium-rich phase are key factors influencing the corrosion resistance of the neodymium iron boron, and when the neodymium-rich phase of the magnet is distributed on the main phase grain boundary in a network shape, selective intergranular corrosion of the sintered neodymium iron boron magnetic material is easy to occur, so that the corrosion resistance of the sintered neodymium iron boron magnetic material is reduced.
Preferably, the cerium is used in an amount of 16 wt%.
By adopting the technical scheme, the added cerium can replace part of praseodymium and neodymium, and because the price of the cerium is obviously lower than that of neodymium, on the premise of ensuring the high performance of the magnet, the mode of replacing part of neodymium by the cerium is favorable for promoting the comprehensive utilization of rare earth resources, thereby reducing the production cost of the sintered neodymium-iron-boron magnetic material.
However, the addition amount of cerium is not easy to be excessive, and when the amount of cerium is 16wt% of the total amount of the neodymium iron boron magnetic material, the coercive force and the magnetic energy product of the magnet of the neodymium iron boron magnetic material are not obviously reduced. When the amount of added cerium exceeds 17wt%, the excess cerium increases the proportion of cerium phase in the rare earth-rich phase, and cerium is oxidized during firing to form cerium oxide. The rare earth-rich phase and a part of cerium oxide formed fall off in the firing process, which can cause a large number of irregular holes in the prepared sintered neodymium-iron-boron magnetic material, and cause the density of the sintered neodymium-iron-boron magnetic material to be reduced.
When the neodymium-iron-boron magnet is in a warm and wet environment, the neodymium-rich phase on the surface of the magnet firstly reacts with water molecules to generate hydrogen. After the reaction, hydrogen atoms generated by the decomposition of water are submerged in the grain boundary of the magnet and further react with the neodymium-rich phase to generate NdH3The reaction causes corrosion of the magnet along the crystal. NdH3The formation of (2) causes volume expansion of the grain boundary, generates stress in the grain boundary, breaks the grain boundary, and if the breakage is serious, the grain boundary is broken, and the magnetic properties are degraded.
In a second aspect, the present application provides a method for preparing a sintered ndfeb magnetic material, which adopts the following technical scheme:
a preparation method of a sintered neodymium-iron-boron magnetic material comprises the following preparation steps:
s1, weighing raw materials according to the components of the final product, putting the raw materials into a vacuum melting furnace for high-temperature melting, and casting the raw materials into alloy sheets at high speed by using a cooling roller;
s2, carrying out hydrogen crushing on the alloy sheet in the S1 to obtain coarse particles;
s3, crushing the coarse particles in the step S2 into powder by using an airflow mill to obtain neodymium iron boron alloy powder;
s4, pressing and forming the neodymium iron boron alloy powder under the vacuum condition to obtain a pressed blank;
s5, sintering the pressed compact prepared in the S4 at high temperature;
and S6, tempering the product obtained after high-temperature sintering in the step S5, and air cooling to obtain the sintered neodymium-iron-boron magnetic material.
By adopting the technical scheme, compared with the traditional ingot casting process, the process of quickly solidifying the thin strip is adopted, and the prepared sintered neodymium iron boron magnetic material can improve the coercivity and the corrosion resistance.
When the magnet is prepared by the traditional ingot casting process, the prepared magnet has coarse main phase grains, the distribution of neodymium-rich phases is relatively concentrated, the neodymium-rich phases are not uniformly distributed around the main phase, the alpha-Fe phase is segregated, and the composition structure is not uniform.
The defects of the traditional ingot casting process can be improved by adopting the rapid hardening thin strip process, so that the prepared magnet has good growth and small size of the columnar crystal of the main phase, the neodymium-rich phase is very thin and is uniformly distributed around the columnar crystal of the main phase, the segregation of an alpha-Fe phase does not exist, and the crystal grain structure of the magnet is fine and uniform.
Hydrogen crushing is a very effective process for preparing coarse crushed powder from rare earth permanent magnetic materials. The process utilizes the characteristic that the rare earth permanent magnetic alloy has hydrogen absorption and desorption, and the alloy is pulverized by grain boundary fracture and transgranular fracture in the process, so that alloy powder with a certain granularity is obtained.
Because the oxidation of the powder process is more serious, in order to reduce the oxidation degree of the magnetic powder, the alloy powder prepared by hydrogen crushing is further crushed by an airflow mill.
The method of hydrogen crushing and airflow milling powder can solve the problem of difficult mechanical alloy crushing, especially in the case of alloy ingot with alpha-Fe.
When the green compact after hydrogen crushing and jet milling is sintered in a vacuum furnace, hydrogen in the furnace reduces the oxidation of the charge. The green compact subjected to hydrogen crushing and jet milling can reduce the sintering temperature and avoid the growth of crystal grains.
Preferably, in S2, the coarse particles have a size of 0.25 to 0.3 mm.
By adopting the technical scheme, coarse particles below 0.325mm can directly enter the jet mill, so that the process is simplified, and the cost of mechanical coarse crushing is greatly reduced.
Preferably, in S3, the particle size of the neodymium iron boron alloy powder is 3-4 μm.
By adopting the technical scheme, the sintered neodymium-iron-boron magnetic material can be directly manufactured from the neodymium-iron-boron alloy powder with the size of 3-4 microns, the process is simplified, and the production cost is reduced.
Preferably, in S4, the NdFeB alloy powder is vertically oriented and pressed in a nitrogen atmosphere at a magnetic field of 3-5T and a pressure of 40-60MPa, and then is subjected to cold isostatic pressing in a magnetic field of 180-220MPa for secondary pressing.
By adopting the technical scheme, the vertical orientation mode is favorable for obtaining higher orientation factors, and meanwhile, the pressing mode has the advantages of low power consumption, high efficiency, convenience in operation and reliability.
Preferably, in S3, an antioxidant TH-412S is added to the neodymium iron boron alloy powder.
Through adopting above-mentioned technical scheme, in the preparation process of neodymium iron boron magnetism body, all have in every process that micro-oxygen gets into the sintered neodymium iron boron, the entering of oxygen can react with rare earth element and comparatively active metal, generates corresponding oxide to reduce the magnetic properties of sintered neodymium iron boron magnetism material. The addition of the antioxidant can reduce the oxygen content in the neodymium iron boron alloy powder.
Preferably, in S5, the sintering temperature for high-temperature sintering is 1000-1050 ℃, and the sintering time is 2-3 h.
By adopting the technical scheme, the sintering temperature of 1000-1050 ℃, organic matters in the pressed compact, gas adsorbed on the surfaces of particles and gas remained in pores can be fully removed.
The magnetic performance of the sintered neodymium iron boron magnetic material can be reduced due to the fact that the sintering temperature is too high, the liquid phase is increased along with the increase of the sintering temperature, more small particles are dissolved and separated out in the liquid phase, more small particles are separated out on the surface of large particles, and therefore abnormal growth of crystal grains occurs, and under the condition that the temperature is too high, the driving force for the growth of the crystal grains is large.
The magnetic performance of the sintered neodymium iron boron magnetic material is reduced due to the fact that the sintering time is too long, the continuous time of solid phase sintering is prolonged along with the increase of the sintering time, the diffusion among crystal grains is enhanced, the interface among the crystal grains gradually disappears, and therefore the phenomenon that a plurality of crystal grains grow into one crystal grain appears.
Preferably, in S6, the tempering treatment comprises first tempering at 880-920 ℃ for 2-4h, and then performing second tempering at 520-560 ℃ for 2-4 h.
By adopting the technical scheme, the grain boundary can be obviously clear in a secondary tempering mode, the main phase grains are well separated, and the intrinsic coercivity is greatly improved.
Because the neodymium-rich phase has serious agglomeration phenomenon before tempering, and after secondary tempering, the neodymium-rich phase is uniformly distributed around the grain boundary of the main phase, and a lamellar grain boundary phase is separated out, thereby reducing the agglomeration phenomenon of the neodymium-rich phase on the grain boundary and at the intersection of the grain boundaries.
Therefore, the secondary tempering can better isolate the main phase grains, remove the exchange coupling effect among the grains, and is beneficial to improving the coercive force, and the grain boundary of the main phase is very regular after the secondary tempering treatment, so that the diamagnetic domain is difficult to form.
Preferably, the sintered nd-fe-b magnet after air cooling in S6 is subjected to a phosphating treatment.
By adopting the technical scheme, the method for adding the rare earth element into the raw materials can substantially improve the corrosion resistance of the sintered neodymium-iron-boron magnetic material, and the surface of the sintered neodymium-iron-boron magnetic material is subjected to coating protection treatment on the basis, so that the corrosion resistance of the sintered neodymium-iron-boron magnetic material can be further improved.
The sintered Nd-Fe-B magnet is phosphated by forming a protective layer on the surface of the magnet to prevent air, moisture or other corrosive substances from entering the surface of the magnet, thereby improving the corrosion resistance of the magnet.
The phosphating process is simple in process, equipment investment is not needed, consumption in the phosphating production process is low, mainly including acid, alkali and phosphating solution, production cost is low, the production cost of the magnet cannot be obviously increased when the phosphating process is used as corrosion resistance, magnet loss in the storage period can be avoided, and the return rate is high.
The phosphatized product has uniform color and clean surface, can be packaged in vacuum, greatly prolongs the storage time, and has a storage means superior to the conventional oil immersion and oiling storage method. The complete phosphating film can resist oxidation corrosion in normal atmospheric environment.
In summary, the present application has the following beneficial effects:
1. as the elements such as Cu and Al are added into the raw materials, intermetallic chemicals are formed at the crystal boundary, and the corrosion resistance of the sintered neodymium-iron-boron magnetic material is improved.
2. The dosage of cerium is preferably 16wt%, and on the premise of ensuring high performance of the magnet, the comprehensive utilization of rare earth resources is facilitated, so that the production cost of the sintered neodymium-iron-boron magnetic material is reduced.
3. According to the method, the defects of the traditional ingot casting process are overcome by adopting the rapid solidification thin strip process, so that the grain structure of the sintered neodymium-iron-boron magnet is fine and uniform.
4. The method solves the problem of difficulty in mechanically crushing the alloy by adopting a method of hydrogen crushing and powder milling by airflow.
Detailed Description
The present application will be described in further detail with reference to examples.
The alkaline degreasing agent is selected from the group consisting of Jinan Beiya specialization industries, Ltd.
Example 1
A preparation method of a sintered neodymium-iron-boron magnetic material comprises the following preparation steps:
s1, weighing the raw materials in proportion, putting the raw materials into a vacuum melting furnace for high-temperature melting, and casting the raw materials into alloy sheets at high speed by using a cooling roller to obtain the alloy sheets;
s2, carrying out hydrogen crushing on the alloy sheet in the S1 into coarse particles of 0.25 mm;
s3, crushing the coarse particles in the step S2 into powder by using an airflow mill to obtain neodymium iron boron alloy powder with the particle size of 3 microns;
s4, vertically orienting and molding the neodymium iron boron alloy powder prepared in the S3 in a nitrogen atmosphere at the magnetic field of 4T and the pressure of 50MPa, and performing cold isostatic pressing in a magnetic field of 220MPa for secondary pressing to obtain a pressed blank;
s5, sintering the pressed compact prepared in the S4 at a high temperature of 1020 ℃ for 2 h;
and S6, performing secondary tempering on the product subjected to high-temperature sintering in the S5, wherein the secondary tempering comprises performing primary tempering at 900 ℃ and keeping for 3 hours, performing secondary tempering at 540 ℃ and keeping for 3 hours, performing air cooling to obtain a sintered neodymium-iron-boron magnetic material, and finally performing phosphating treatment.
In the sintered neodymium iron boron magnetic material, the components in percentage by mass are as follows: PrNd35wt%, B1.7wt%, Ce16wt%, Ga3.0wt%, Zr0.1wt%, La0.2wt%, Cu0.3wt%, Al0.2wt%, Co1.1wt%, and the balance Fe and non-removable impurities.
The phosphating treatment comprises the following steps:
a1, carrying out degreasing treatment on the sintered neodymium iron boron magnetic material, wherein the degreasing treatment adopts an alkaline degreasing agent, the temperature is 60 ℃, and the time is 4 min;
a2, washing the degreased sintered neodymium iron boron magnetic material with water;
a3, putting the washed sintered neodymium-iron-boron magnetic material into a phosphating solution, and standing for 4 min;
and A4, washing with water again, and finally drying.
The basic formula and the technological parameters of the phosphating solution are as follows: 50g/L of sodium dihydrogen phosphate, 12ml/L of phosphoric acid and 0.6g/L of sodium molybdate, and the time is 4min at room temperature.
Examples 2 to 5
Examples 2-5 sintered nd-fe-b magnets were prepared in the same manner as in example 1 except as shown in tables 1-2:
table 1 raw material composition and amount of sintered nd-fe-b magnetic material in examples 1-5
| Weight percent/wt% | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 |
| PrNd | 35 | 30 | 40 | 35 | 38 |
| B | 1.7 | 1.8 | 1.5 | 1.6 | 1.7 |
| Ce | 16 | 17 | 16 | 15 | 16 |
| Ga | 3 | 2.5 | 3.0 | 3.5 | 3.0 |
| Zr | 0.1 | 0.3 | 0.2 | 0.1 | 0.3 |
| La | 0.2 | 0.2 | 0.1 | 0.3 | 0.2 |
| Cu | 0.3 | 0.3 | 0.1 | 0.2 | 0.2 |
| Al | 0.2 | 0.1 | 0.2 | 0.3 | 0.2 |
| Co | 1.1 | 0.9 | 1.1 | 1.2 | 1.0 |
| Fe and non-removable impurities | 42.4 | 46.9 | 37.8 | 42.8 | 39.4 |
Table 2 parameters of sintered nd-fe-b magnet in examples 1-5
Example 6
The sintered nd-fe-b magnetic material of example 6 was prepared in the same manner as example 1 except that the vertical orientation molding in S4 was replaced with the horizontal orientation molding.
Comparative example 1
Comparative example 1 is identical to the preparation method of the sintered nd-fe-b magnetic material of example 1 except that no antioxidant is added in S3.
Comparative example 2
Comparative example 2 is identical to the method of manufacturing the sintered nd-fe-b magnet of example 1 except that the sintered nd-fe-b magnet after air cooling in S6 is not subjected to the phosphating treatment.
Comparative example 3
Comparative example 3 is identical to the preparation method of the sintered nd-fe-b magnetic material of example 1 except that the amount of cerium used in the raw materials is 4 wt%.
Comparative example 4
Comparative example 4 is identical to the preparation method of the sintered nd-fe-b magnetic material of example 1 except that the amount of cerium used in the raw materials is 8 wt%.
Comparative example 5
Comparative example 5 is identical to the method of manufacturing the sintered nd-fe-b magnetic material of example 1 except that Al and Cu are not added to the raw materials.
Comparative example 6
Comparative example 6 is identical to the method of manufacturing the sintered nd-fe-b magnetic material of example 1 except that the sintering temperature is 1100 c and the sintering time is 4h in S5.
Performance test
And (4) carrying out a corrosion test on the sintered neodymium iron boron magnetic material by adopting a neutral salt spray test (NSS).
Detection method/test method
Coercive force: carrying out coercive force test on the sintered neodymium iron boron magnetic material by adopting American MicroSense high precision;
oxygen content: the oxygen content in the magnet was quantitatively analyzed using an IRO-ii infrared oxygen analyzer.
TABLE 3 test results of examples 1 to 6
| Test items | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 |
| Coercive force (KOe) | 15.46 | 15.59 | 15.17 | 15.53 | 15.32 | 14.91 |
| Oxygen content (ppm) | 513.2 | 523.1 | 532.4 | 519.3 | 532.8 | 536.3 |
| Corrosion time 48h weight loss ratio (wt%) | 0.036 | 0.031 | 0.032 | 0.034 | 0.035 | 0.034 |
| Corrosion time 96h weight loss ratio (wt%) | 0.421 | 0.351 | 0.395 | 0.432 | 0.389 | 0.341 |
| Weight loss ratio (wt%) of corrosion time 144h | 0.865 | 0.735 | 0.894 | 0.866 | 0.781 | 0.746 |
TABLE 4 test results of comparative examples 1 to 6
| Test items | Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example 4 | Comparative example 5 | Comparative example 6 |
| Coercive force (KOe) | 14.52 | 14.26 | 14.77 | 13.36 | 13.16 | 12.83 |
| Oxygen content (ppm) | 1213.5 | 1325.6 | 635.6 | 511.6 | 1438.5 | 892.3 |
| Corrosion time 48h weight loss ratio (wt%) | 0.057 | 0.068 | 0.052 | 0.063 | 0.079 | 0.075 |
| Corrosion time 96h weight loss ratio (wt%) | 0.412 | 0.685 | 0.431 | 0.721 | 0.762 | 0.689 |
| Weight loss ratio (wt%) of corrosion time 144h | 0.762 | 1.356 | 0.721 | 1.627 | 1.657 | 1.539 |
It can be seen from the combination of examples 1 to 5 and comparative examples 3 to 4 and the combination of tables 3 to 4 that the oxygen content of the sintered ndfeb magnet can be reduced as the cerium content increases, thereby improving the corrosion resistance of the sintered ndfeb magnet. When the cerium content is 16wt%, the sintered Nd-Fe-B magnetic material has the best corrosion resistance. When the content of cerium exceeds 17wt%, the corrosion resistance is lowered.
Combining example 1 and example 6 with table 3, it can be seen that the magnetic performance of the sintered ndfeb magnet made by vertical orientation molding is better than that of the sintered ndfeb magnet made by horizontal orientation molding.
Combining example 1 and comparative example 1 with tables 3-4, it can be seen that the addition of the antioxidant can reduce the oxygen content of the sintered ndfeb magnet, thereby improving the corrosion resistance of the sintered ndfeb magnet. And the lower the oxygen content is, the better the corrosion resistance of the sintered neodymium iron boron magnetic material is.
If the oxygen content in the magnet is very high, the rare earth oxide formed in the sintering aging process exists in the grain boundary in the form of solid particles, so that the infiltration effect of the neodymium-rich phase relative to the main phase grains is reduced, the neodymium-rich phase is easily enriched at the corner of the grain boundary, and the oxygen content of the local area of the sintered neodymium-iron-boron magnet is increased. This promotes the surface corrosion of the sintered ndfeb magnetic material to expand to the interior of the magnet, so that the main phase crystal grains fall off, the weight loss rate is improved, and the corrosion resistance of the sintered ndfeb magnetic material is reduced.
It can be seen by combining example 1 and comparative example 2 and tables 3 to 4 that the corrosion resistance of the sintered ndfeb magnet subjected to phosphating treatment is superior to that of the sintered ndfeb magnet not subjected to phosphating treatment.
It can be seen from the combination of example 1 and comparative example 5 and tables 3-4 that the sintered nd-fe-b magnetic material prepared without adding Al and Cu to the raw materials has significantly reduced magnetic properties. Meanwhile, the corrosion resistance of the sintered Nd-Fe-B magnetic material is also obviously reduced.
Combining example 1 and comparative example 6 with tables 3-4, it can be seen that too high a sintering temperature and too long a sintering time can degrade the magnetic properties of the sintered ndfeb magnet and affect its corrosion resistance.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (10)
1. The sintered neodymium-iron-boron magnetic material is characterized by comprising the following components in percentage by mass: PrNd30-40wt%, B1.5-1.8wt%, Ce15-17wt%, Ga2.5-3.5wt%, Zr0.1-0.3wt%, La0.1-0.3wt%, Cu0.1-0.3wt%, Al0.1-0.3wt%, Co0.9-1.2wt%, and Fe and irremovable impurity for the rest.
2. The sintered NdFeB magnet as claimed in claim 1, wherein: the amount of cerium was 16 wt%.
3. The method for preparing sintered NdFeB magnetic material according to any one of claims 1-2, comprising the following steps:
s1, weighing raw materials according to the components of the final product, putting the raw materials into a vacuum melting furnace for high-temperature melting, and casting the raw materials into alloy sheets at high speed by using a cooling roller;
s2, carrying out hydrogen crushing on the alloy sheet in the S1 to obtain coarse particles;
s3, crushing the coarse particles in the step S2 into powder by using an airflow mill to obtain neodymium iron boron alloy powder;
s4, pressing and forming the neodymium iron boron alloy powder under the vacuum condition to obtain a pressed blank;
s5, sintering the pressed compact prepared in the S4 at high temperature;
and S6, tempering the product obtained after high-temperature sintering in the step S5, and air cooling to obtain the sintered neodymium-iron-boron magnetic material.
4. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: in S2, the size of the coarse particles is 0.25-0.3 mm.
5. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: in S3, the particle size of the neodymium iron boron alloy powder is 3-4 μm.
6. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: in S4, the Nd-Fe-B alloy powder is vertically oriented and pressed in a nitrogen atmosphere with the magnetic field of 3-5T and the pressure of 40-60Mpa, and then is pressed for the second time in a cold isostatic pressing in the magnetic field of 180-220 Mpa.
7. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: in S3, adding an antioxidant TH-412S into the neodymium iron boron alloy powder.
8. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: in S5, the sintering temperature for high-temperature sintering is 1000-1050 ℃, and the sintering time is 2-3 h.
9. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: in S6, the annealing treatment comprises first annealing at 880-920 ℃ for 2-4h, and then performing second annealing at 520-560 ℃ for 2-4 h.
10. The method for preparing the sintered NdFeB magnetic material according to claim 3, wherein the method comprises the following steps: and (4) carrying out phosphating treatment on the sintered neodymium iron boron magnetic material subjected to air cooling in the S6.
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