CN113921260A - Hot-pressing preparation method of rare earth permanent magnet - Google Patents
Hot-pressing preparation method of rare earth permanent magnet Download PDFInfo
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- CN113921260A CN113921260A CN202010664728.XA CN202010664728A CN113921260A CN 113921260 A CN113921260 A CN 113921260A CN 202010664728 A CN202010664728 A CN 202010664728A CN 113921260 A CN113921260 A CN 113921260A
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- 238000007731 hot pressing Methods 0.000 title claims abstract description 39
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 31
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 21
- 238000005238 degreasing Methods 0.000 claims abstract description 17
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 15
- 239000000956 alloy Substances 0.000 claims abstract description 15
- 230000032683 aging Effects 0.000 claims abstract description 13
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000001257 hydrogen Substances 0.000 claims abstract description 10
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 10
- 238000007599 discharging Methods 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 239000007789 gas Substances 0.000 claims abstract description 6
- 230000006698 induction Effects 0.000 claims abstract description 6
- 238000011282 treatment Methods 0.000 claims abstract description 6
- 239000006259 organic additive Substances 0.000 claims abstract description 5
- 238000003723 Smelting Methods 0.000 claims abstract description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- 229910052786 argon Inorganic materials 0.000 claims description 7
- 239000000843 powder Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 239000006247 magnetic powder Substances 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 3
- 239000010959 steel Substances 0.000 claims description 3
- 230000005347 demagnetization Effects 0.000 claims description 2
- 229910052692 Dysprosium Inorganic materials 0.000 claims 1
- 229910052689 Holmium Inorganic materials 0.000 claims 1
- 229910001117 Tb alloy Inorganic materials 0.000 claims 1
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims 1
- 239000012467 final product Substances 0.000 claims 1
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 claims 1
- 238000005336 cracking Methods 0.000 abstract description 4
- 239000000047 product Substances 0.000 description 8
- 238000005245 sintering Methods 0.000 description 8
- 239000002245 particle Substances 0.000 description 6
- 238000000227 grinding Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 238000000635 electron micrograph Methods 0.000 description 4
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 description 3
- 210000000078 claw Anatomy 0.000 description 3
- 238000010902 jet-milling Methods 0.000 description 3
- 239000000314 lubricant Substances 0.000 description 3
- 229910001172 neodymium magnet Inorganic materials 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000011258 core-shell material Substances 0.000 description 2
- NUKZAGXMHTUAFE-UHFFFAOYSA-N methyl hexanoate Chemical compound CCCCCC(=O)OC NUKZAGXMHTUAFE-UHFFFAOYSA-N 0.000 description 2
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 2
- 229910052982 molybdenum disulfide Inorganic materials 0.000 description 2
- 230000005405 multipole Effects 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- SNRUBQQJIBEYMU-UHFFFAOYSA-N Dodecane Natural products CCCCCCCCCCCC SNRUBQQJIBEYMU-UHFFFAOYSA-N 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910000828 alnico Inorganic materials 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- KPLQYGBQNPPQGA-UHFFFAOYSA-N cobalt samarium Chemical compound [Co].[Sm] KPLQYGBQNPPQGA-UHFFFAOYSA-N 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000007822 coupling agent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- -1 dodecyl alkane Chemical class 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 125000001183 hydrocarbyl group Chemical group 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000000462 isostatic pressing Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 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
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 229910000938 samarium–cobalt magnet Inorganic materials 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 1
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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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/026—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets protecting methods against environmental influences, e.g. oxygen, by surface treatment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- 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
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Environmental & Geological Engineering (AREA)
- Hard Magnetic Materials (AREA)
- Powder Metallurgy (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Abstract
The invention relates to a method for preparing a rare earth permanent magnet, in particular to a method for preparing the rare earth permanent magnet by hot pressing. Solves the problems of large deformation of sintered rare earth permanent magnets and high cracking rate of ring and sheet products in the prior art. A hot-pressing preparation method of a rare earth permanent magnet is realized by the following steps: 1) smelting rare earth alloy; 2) crushing the alloy; 3) conventional magnetic field forming; 4) degreasing in a vacuum degreasing furnace, removing gas adsorbed by the green body, volatilizing organic additives in the green body and removing residual hydrogen in the crushing process; 5) induction heating the mold and the green body, performing hot pressing to make the density of the workpiece reach the density required by the finished permanent magnet, cooling and discharging; 6) and performing secondary aging treatment to obtain a finished permanent magnet. The section size is the same as the die, and the near-net forming without processing or with less processing is realized. The preparation method is suitable for permanent magnets of various shapes, and is particularly suitable for ring and sheet products.
Description
Technical Field
The invention relates to a method for preparing a rare earth permanent magnet, in particular to a method for preparing the rare earth permanent magnet by hot pressing.
Background
In the prior art, rare earth permanent magnets are obtained through a sintering process. The volume shrinkage rate of the rare earth permanent magnet exceeds 40% in the sintering process, and the shrinkage rate in the magnetic field direction is nearly twice as large as that of a non-magnetic field method, so that the shrinkage deformation is large, more grinding amount is reserved, the grinding is time-consuming and labor-consuming, and the material yield is low. Ring and tile shapes, and high breakage rate during grinding. The cracking rate of the multi-pole magnetic ring and the radiation magnetic ring is particularly high.
Disclosure of Invention
The invention solves the problems of large shrinkage deformation amount, large grinding amount and high ring product cracking rate of the rare earth permanent magnet in the prior art, and provides a preparation method of the rare earth permanent magnet to overcome the problems.
The invention is realized by adopting the following technical scheme: a hot-pressing preparation method of a rare earth permanent magnet is realized by the following steps:
1) smelting rare earth alloy;
2) crushing the alloy;
3) filling the magnetic powder into a mold, performing magnetic field forming and demagnetization to make the density reach 3.8-4.5g/cm3；
4) Putting a certain batch of green bodies into a vacuum degreasing furnace, gradually raising the temperature, removing gas adsorbed by the green bodies, volatilizing organic additives in the green bodies and hydrogen remained in the hydrogen crushing process; the degreasing process was determined by a limited number of tests, depending on the volume size of the green body, the amount and type of organic additives, and the amount of residual hydrogen. The former stage is used for degreasing, ensuring a carbon content of less than 1000ppm, preferably less than 500 ppm. The latter stage is used for dehydrogenation, with hydrogen residues below 500 ppm. Cooling to room temperature and discharging. The upper limit of the temperature is that the green body does not undergo sintering shrinkage.
5) Hot pressing
Putting the degreased green bodies into a hot pressing furnace in batches, and replacing the green bodies by argon until the oxygen concentration is lower than 100 ppm. And (4) putting the green bodies into a die cavity of a hot press one by one or in groups. Heating with medium frequency or high frequency induction to reach hot pressing temperature and maintaining for some time. Then hot pressing is performed. And (5) discharging the product after cooling.
Because of high temperature and high pressure, the die is made of hard alloy with high strength, so that the service life of the die is ensured.
After degreasing, the green body is not directly hot-pressed, mainly because the thin-wall green body has low high-temperature strength, and the ring green body has high breakage rate when being grabbed by a mechanical claw and is difficult to align with a die cavity. In addition, special degreasing-hot pressing integrated automation equipment is required.
For thick-wall or solid products, the green body can also be directly placed into a die cavity of a hot-pressing furnace after degreasing, and the green body is not cooled and discharged, and then heated for the second time. The invention mainly solves the production problem of thin-wall products. Or the wall thickness is larger, and the method belongs to the production of multiple varieties in small batch.
Range of hot pressing temperature: when the temperature is lower than 550 ℃, the pressure is higher, and the green body is difficult to reach the density required by the finished permanent magnet (7.5-7.6 g/cm for neodymium iron boron)3) However, temperatures above 1000 ℃ are advantageous for increasing the hot pressing density (the pressure is inversely proportional to the temperature, i.e., the higher the temperature, the lower the pressure required to achieve the finished permanent magnet density). However, if the temperature is too high, the grains of the rare earth permanent magnet material will grow up, which will affect the performance of the permanent magnet. Therefore, the temperature, pressure, and holding time required for hot pressing in this step can be easily obtained by a limited number of tests. The temperature and pressure range obtained by the test is 550-1000 ℃, and is preferably 760-950 ℃. The dwell time is 20s-100 s.
The invention provides a novel preparation method of a rare earth permanent magnet, which is characterized in that the permanent magnet with required finished product density is obtained by conventional magnetic field forming, vacuum degreasing and hot pressing, thereby solving the problems of large sintering deformation and high ring product cracking rate in the prior art and reducing the cost; meanwhile, the hot-pressed green body has standard shape and high dimensional precision, the grinding process can be basically omitted, and the outer surface of the green body is slightly oxidized in the degreasing and hot-pressing processes to form a compact oxide layer which is a natural protective layer and can not be electroplated under many conditions, so that the preparation process is simplified; because the hot pressing temperature is far lower than the sintering temperature and the hot pressing time is far shorter than the sintering time, the crystal grains are not easy to grow and almost keep the size and the shape of the powder particles. Particularly, by adopting a double-alloy method, heavy rare earth elements only permeate into the surface layer of the main phase to form a core-shell structure, and a double-high product with high coercivity and high remanence is obtained. The preparation method is suitable for permanent magnets of various shapes, and is particularly suitable for multi-pole magnetic rings, radiation magnetic rings, tile shapes and sheets.
Even if some internal defects occur in the magnetic field forming, they are eliminated in the hot pressing. The present invention is therefore an all-round optimization of the prior art, both in terms of efficiency, in terms of quality, in terms of performance, or in terms of cost.
Drawings
FIG. 1 is an electron micrograph of the powder after jet milling;
FIG. 2 is an electron micrograph of neodymium iron boron permanent magnet after 900 deg.C aging.
Detailed Description
The invention is further described below with reference to the figures and examples.
Examples
A hot-pressing preparation method of a rare earth permanent magnet is realized by the following steps:
1) smelting rare earth alloy;
2) crushing the alloy;
3) and filling the magnetic powder into the die cavity, and carrying out magnetic field forming. The density is 3.8 to 5.5g/cm3Not isostatic pressing.
4) And (3) degreasing the green body at medium temperature in vacuum, only removing gas adsorbed by the green body, volatilizing organic additives in the green body and hydrogen remained in the hydrogen crushing process, and avoiding shrinkage of the green body. In the specific implementation, the vacuum degreasing temperature is preferably 300-500 ℃ and 650-950 ℃. (for example, it may be selected from 400 ℃ for 2 hours and 900 ℃ for 3 hours). In the temperature rise process of vacuum degreasing, the temperature rise speed is controlled to be 5-10 ℃/min. The heat preservation time interval is set to ensure that the heating is uniform, the air is fully discharged, and the carbon adding amount is reduced. The latter stage is mainly to remove residual hydrogen. Cooling to room temperature, charging argon and discharging.
5) And further carrying out hot pressing on the degreased green body to enable the density of the green body to reach the final density of the permanent magnet.
And putting the degreased green bodies into a die cavity of a hot pressing furnace in batches, and replacing air with argon until the oxygen concentration is lower than 100 ppm. The workpieces are placed into a die cavity of a hot press one by using a mechanical claw or a manual clamping claw, the die and the green body are heated to a hot pressing temperature by medium frequency induction, and then the workpieces are pressed one by one.
And carrying out hot pressing on the green body in the die to ensure that the density of the green body reaches the density required by the finished permanent magnet, and obtaining the finished permanent magnet after aging. In specific implementation, preferably, the mold and the green body therein are heated to 650-; at this temperature, the grains hardly grow and maintain the size after the jet milling. The coercive force is improved compared with the common sintering, and the remanence is not reduced. The mold and the green body therein are heated to a desired temperature, kept warm for 0.3-10 minutes (for example, 0.3 minute, 0.5 minute, 0.8 minute, 1 minute, 3 minutes, 5 minutes, 6 minutes, 8 minutes, 9 minutes, 10 minutes are selected), pressurized to a desired pressure, and then kept for 0.3-10 minutes (for example, 0.3 minute, 0.5 minute, 0.8 minute, 1 minute, 3 minutes, 5 minutes, 6 minutes, 8 minutes, 9 minutes, 10 minutes are selected) to ensure the heat and pressure are kept constant. The longer dwell time is beneficial to the increase of density and the improvement of density uniformity, but too long will inevitably affect production efficiency, and further too long will possibly cause grain growth and affect magnetic performance.
The hot pressing temperature is lower than the sintering temperature, and the crystal grains are not easy to grow. The method is particularly beneficial to adopting a double-alloy method, the heavy rare earth element only permeates into the surface layer of the main phase to form a core-shell structure, and a double-high product with high coercivity and high remanence is obtained. The result is equivalent to the surface permeation of heavy rare earth, but the manufacturability is far better than the surface diffusion of heavy rare earth.
And carrying out 900 ℃ aging treatment on the hot-pressed workpiece, passivating the sharp corners of the particles, combining small particles, uniformly distributing a neodymium-rich phase, and completely and clearly preparing a crystal boundary, wherein the aging time is longer than that of sintered neodymium iron boron, and is generally 3-9 hours. Preferably 5-6 hours. Then, the coercivity is further improved by performing low-temperature aging at 490-520 ℃. And obtaining the permanent magnet product.
The die material can be selected from materials such as heat-resistant die steel and hard alloy according to production batches. If necessary, the surface of the green body is sprayed with high-temperature lubricant such as molybdenum disulfide and the like.
Example one
Vacuum melting, preparing 48H quick-setting tablets, and quickly setting and spinning to obtain quick-setting sheets with the thickness of 0.25-0.35 mm.
The rapidly solidified flakes HD were coarsely crushed according to a conventional method. 800 PPM residual hydrogen
Milling with a jet mill to an average particle size of 3.2 microns. The total amount of the antioxidant and the lubricant is 0.5 percent. Wherein the methyl caproate is wetted by 15 percent, the isomeric dodecyl alkane is wetted by 20 percent, the zinc stearate is wetted by 2 percent, the coupling agent is wetted by 5 percent, and the rest is hydrocarbon diluent.
The hard alloy die has the die size of 80 mm in outer diameter, 30mm in inner diameter and 100mm in die cavity depth. The core rod is made of bearing steel.
Adding 75g of magnetic powder into the film cavity; applying magnetic field for pressing, wherein the magnetic field is 1.2, the pressure is 40MPa, and the density is 3.9g/cm3。
After demoulding, putting the mixture into a vacuum degreasing furnace, heating to 400 ℃ at the vacuum degree of 0.01Pa according to 5 ℃/min, and preserving heat for 120 min; then the temperature is raised to 900 ℃ according to the speed of 5 ℃/min, and the temperature is preserved for 60 min. Then, argon gas was introduced. And after cooling to room temperature, opening the furnace door and discharging. Spraying molybdenum disulfide powder on the surface of the green body to serve as a die wall lubricant.
The degreased green compact was placed in a hot ballast and replaced by argon gas to achieve an oxygen concentration of less than 50 ppm.
Placing the green bodies on a die of a press one by a mechanical gripper, starting medium frequency induction heating to reach 900 ℃, preserving heat for 30S, then pressing at 50MPa, and maintaining the pressure for 60S to obtain the green bodies with the density of 7.6g/cm3. Cooling to 80 ℃, and discharging. And carrying out 900-degree aging for 6 hours and then carrying out 500-degree aging for 5 hours to obtain the radiation magnetic ring with 48H performance. The direct dimension is not changed, and only the height direction is reduced by half.
Example two
0.6% of Tb (80%) -Cu (20%) alloy powder was added during compounding. The rest is the same as the first embodiment. A high remanence, high coercivity magnet of 46EH was obtained.
FIG. 1 is an electron micrograph of the powder after jet milling at 10000 times. The largest particle is 7-8 microns.
FIG. 2 is an electron micrograph of the permanent magnet after aging at 900 ℃ with the largest particles also being 7-8 microns. Because the hot pressing temperature is low, the time is short, and the crystal grains are hardly grown.
This scheme can also be used to the manufacturing of class metal permanent-magnet such as samarium cobalt, alnico. It can also be used for hot-press forming of tiles, fans, wafers, square sheets, squares or irregular blocks.
The above examples are merely representative of preferred embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, various changes, modifications and substitutions can be made without departing from the spirit of the present invention, and these are all within the scope of the present invention.
Claims (8)
1. The hot-pressing preparation method of the rare earth permanent magnet is characterized by comprising the following steps of:
1) smelting rare earth alloy;
2) crushing the alloy;
3) filling the magnetic powder into a mold, and performing magnetic field forming and demagnetization to make the density reach 3.8-4.5g/cm 3;
4) putting the green body into a vacuum degreasing furnace, removing gas adsorbed by the green body, volatilizing organic additives in the green body and hydrogen remained in the hydrogen crushing process; cooling to room temperature and discharging;
5) placing the degreased green body into a hot pressing furnace, and replacing the green body by argon until the oxygen concentration is lower than 100 ppm; placing the green body into a die cavity of a hot press; induction heating to reach hot pressing temperature and maintaining for some time; then hot pressing is carried out; cooling and discharging;
6) and (5) performing aging treatment to obtain a final product.
2. The hot-pressing preparation method of a rare earth permanent magnet according to claim 1, wherein the hot-pressing die material is a hard alloy or heat-resistant steel material.
3. The hot-pressing preparation method of a rare earth permanent magnet as claimed in claim 1, wherein in step 4), the degreasing temperature is selected from 300 ℃ and 750 ℃ to 900 ℃, the secondary degreasing is performed, and the total degreasing time is selected from 4 to 7 hours.
4. The hot-pressing preparation method of a rare earth permanent magnet as claimed in claim 1, wherein step 5), intermediate frequency induction heating is performed, the hot-pressing temperature is 650-.
5. The method of claim 1, wherein the aging treatment comprises secondary aging treatments at 900 ℃ and 500 ℃.
6. The hot-pressing preparation method of a rare earth permanent magnet according to claim 3, characterized in that the rare earth permanent magnet is discharged after argon is filled before discharging.
7. The method of claim 5, wherein the aging treatment is carried out at 900 ℃ for 3-9 hours.
8. The hot-pressing preparation method of a rare earth permanent magnet according to claim 1, characterized in that a powder containing one or two alloys of terbium, dysprosium, holmium is added to the pulverized powder; the addition amount is 0.1 to 5 percent.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116590080A (en) * | 2023-06-12 | 2023-08-15 | 大地熊(包头)永磁科技有限公司 | Release agent and neodymium iron boron forming method |
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| CN104332264A (en) * | 2014-10-13 | 2015-02-04 | 宁波尼兰德磁业有限公司 | Method for enhancing properties of sintered neodymium-iron-boron magnets |
| CN111276309A (en) * | 2018-12-04 | 2020-06-12 | 董元 | Method for preparing rare earth permanent magnet through hot press molding |
| CN111276308A (en) * | 2018-12-04 | 2020-06-12 | 董元 | Method for preparing rare earth permanent magnet by hot press molding |
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| CN101154489A (en) * | 2007-08-31 | 2008-04-02 | 钢铁研究总院 | Anti-impact ferrous rare earth permanent magnet and its manufacturing method |
| JP2009123968A (en) * | 2007-11-15 | 2009-06-04 | Hitachi Metals Ltd | POROUS MATERIAL FOR R-Fe-B BASED PERMANENT MAGNET, AND MANUFACTURING METHOD THEREOF |
| CN104332264A (en) * | 2014-10-13 | 2015-02-04 | 宁波尼兰德磁业有限公司 | Method for enhancing properties of sintered neodymium-iron-boron magnets |
| CN111276309A (en) * | 2018-12-04 | 2020-06-12 | 董元 | Method for preparing rare earth permanent magnet through hot press molding |
| CN111276308A (en) * | 2018-12-04 | 2020-06-12 | 董元 | Method for preparing rare earth permanent magnet by hot press molding |
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| CN116590080A (en) * | 2023-06-12 | 2023-08-15 | 大地熊(包头)永磁科技有限公司 | Release agent and neodymium iron boron forming method |
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