CN117637333A - Forming method of neodymium-iron-boron magnet - Google Patents
Forming method of neodymium-iron-boron magnet Download PDFInfo
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- CN117637333A CN117637333A CN202311832669.2A CN202311832669A CN117637333A CN 117637333 A CN117637333 A CN 117637333A CN 202311832669 A CN202311832669 A CN 202311832669A CN 117637333 A CN117637333 A CN 117637333A
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- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 95
- 238000000034 method Methods 0.000 title claims abstract description 78
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 71
- 239000001257 hydrogen Substances 0.000 claims abstract description 71
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 71
- 239000000843 powder Substances 0.000 claims abstract description 61
- 238000000465 moulding Methods 0.000 claims abstract description 46
- 239000006247 magnetic powder Substances 0.000 claims abstract description 38
- 238000005245 sintering Methods 0.000 claims abstract description 29
- 239000003963 antioxidant agent Substances 0.000 claims abstract description 27
- 230000003078 antioxidant effect Effects 0.000 claims abstract description 27
- 238000003825 pressing Methods 0.000 claims abstract description 23
- 239000011812 mixed powder Substances 0.000 claims abstract description 19
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000000227 grinding Methods 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 238000005266 casting Methods 0.000 claims abstract description 8
- 239000002994 raw material Substances 0.000 claims abstract description 6
- 238000007873 sieving Methods 0.000 claims abstract description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 34
- 238000000462 isostatic pressing Methods 0.000 claims description 26
- 238000001816 cooling Methods 0.000 claims description 21
- 239000000463 material Substances 0.000 claims description 18
- 229910052786 argon Inorganic materials 0.000 claims description 17
- 238000003723 Smelting Methods 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 12
- BXWNKGSJHAJOGX-UHFFFAOYSA-N hexadecan-1-ol Chemical compound CCCCCCCCCCCCCCCCO BXWNKGSJHAJOGX-UHFFFAOYSA-N 0.000 claims description 10
- 239000007789 gas Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 6
- 229960000541 cetyl alcohol Drugs 0.000 claims description 5
- 238000006356 dehydrogenation reaction Methods 0.000 claims description 5
- LZTRCELOJRDYMQ-UHFFFAOYSA-N triphenylmethanol Chemical compound C=1C=CC=CC=1C(C=1C=CC=CC=1)(O)C1=CC=CC=C1 LZTRCELOJRDYMQ-UHFFFAOYSA-N 0.000 claims description 5
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 claims description 5
- 238000007790 scraping Methods 0.000 claims description 4
- 239000012300 argon atmosphere Substances 0.000 claims description 3
- 238000010298 pulverizing process Methods 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 238000012216 screening Methods 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims 1
- 230000008018 melting Effects 0.000 claims 1
- 238000005336 cracking Methods 0.000 abstract description 9
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 18
- 230000008569 process Effects 0.000 description 11
- 230000005415 magnetization Effects 0.000 description 8
- 238000002474 experimental method Methods 0.000 description 5
- 238000003801 milling Methods 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 238000000137 annealing Methods 0.000 description 3
- 230000002950 deficient Effects 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 238000007493 shaping process Methods 0.000 description 3
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 238000000748 compression moulding Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical group [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 1
- 239000013078 crystal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 239000013081 microcrystal Substances 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
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
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- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Abstract
The invention discloses a molding method of a neodymium iron boron magnet, and relates to the technical field of magnet molding. The molding method comprises the following steps: casting the raw materials into cast pieces; carrying out hydrogen breaking on the cast sheet to obtain coarse powder with the hydrogen content of 1000-1200 ppm; mixing coarse powder, aviation gasoline and a first part of antioxidant to obtain mixed powder, grinding the mixed powder to obtain powder, and mixing the powder with a second part of antioxidant to obtain fine powder; sieving the fine powder to obtain neodymium iron boron magnetic powder; magnetizing neodymium iron boron magnetic powder, closing the die, pressing and demolding to obtain a blank; and sintering the blank to obtain the NdFeB magnet. The method can reduce the occurrence of internal cracking or rupture of the magnet, is beneficial to reducing the molding difficulty of the magnet and improving the magnetic performance and yield of the magnet.
Description
Technical Field
The invention relates to the technical field of magnet forming, in particular to a forming method of a neodymium iron boron magnet.
Background
The neodymium-iron-boron magnet is tetragonal crystal formed by neodymium, iron and boron, has high magnetic energy product and high magnet coercivity, and is the most commonly used rare earth magnet at present. With the rapid development of the times, the role played by the NdFeB magnet in the technological development is more important, and the social demand of the NdFeB magnet is also increased year by year. However, along with the violent rise of the price of rare earth raw materials, the price of the neodymium-iron-boron magnet also rises, and how to reduce the cost is a difficult problem in front of the manufacturers of the neodymium-iron-boron magnet.
In the related art, in the process of forming the neodymium-iron-boron magnetic powder, the granularity of the neodymium-iron-boron magnetic powder is reduced, and the magnet coercivity of the prepared neodymium-iron-boron magnet can be improved, so that the neodymium-iron-boron magnet with higher magnetic performance can be prepared, and the cost of the neodymium-iron-boron magnet is reduced.
However, the reduced particle size of the neodymium-iron-boron magnetic powder may cause difficulty in molding the neodymium-iron-boron magnetic powder.
Disclosure of Invention
In order to solve the problem that the neodymium-iron-boron magnet is difficult to mold due to the reduction of the granularity of the neodymium-iron-boron magnetic powder, the application provides a molding method of the neodymium-iron-boron magnet.
The application provides a forming method of a neodymium iron boron magnet, which adopts the following technical scheme:
a forming method of a neodymium-iron-boron magnet comprises the following steps:
casting: smelting raw materials, and casting the raw materials into a sheet to obtain a cast sheet;
breaking hydrogen: carrying out hydrogen breaking on the cast sheet to obtain coarse powder with the hydrogen content of 1000-1200 ppm;
grinding: uniformly mixing coarse powder, aviation gasoline and a first part of antioxidant according to the weight ratio of (950-1050) 1 (0.3-0.9) to obtain mixed powder, grinding the mixed powder to obtain powder, and mixing the powder with a second part of antioxidant according to the weight ratio of (950-1050) 2 to obtain fine powder;
and (3) screening: sieving the fine powder with 200-300 mesh sieve, and removing the screen residue to obtain neodymium iron boron magnetic powder;
and (3) forming: pouring neodymium iron boron magnetic powder into a die cavity of a lower die, uniformly scraping powder, moving an upper die towards a direction close to the lower die, moving the upper die and the lower die in the same direction at a speed ratio of 1 (1.5-2.5) after the upper die moves to be in contact with the die cavity, stopping moving the upper die and the lower die when the moving stroke of the lower die reaches 8-12mm, then starting magnetizing, closing the upper die and the lower die, pressing, and demoulding to obtain a blank after the pressing is finished;
sintering: and carrying out isostatic pressing sintering on the blank to obtain the neodymium-iron-boron magnet.
Through adopting above-mentioned technical scheme, this application discovers through the experiment, when adopting above-mentioned method preparation magnetic powder and carrying out shaping and sintering to the magnetic powder, the neodymium iron boron magnetism body of obtaining is good in appearance, and magnetic property is high, has excellent yields. This is probably because controlling the hydrogen content of the magnetic powder to 1000-1200ppm helps to protect the magnetic powder during the pulverizing, pressing and sintering steps, and mixing the coarse powder, aviation gasoline and the first antioxidant in the above weight ratio can further protect the magnetic powder during the pulverizing process and reduce oxidation of the magnetic powder. In addition, the average particle size of the powder and the weight ratio of the powder to the second antioxidant are controlled within the above ranges, which not only helps to reduce the particle size of the magnetic powder, but also improves the lubricity of the magnetic powder, thereby improving the degree of orientation of the magnetic powder. The magnetic powder is scattered after being screened by a 200-mesh screen, so that the magnetic powder is prevented from agglomerating, and meanwhile, oversized particles are screened out, so that the magnetic performance of the magnet is improved. And then the magnetic powder is prepared according to the forming step and the sintering step, so that the occurrence of internal cracking or cracking of the magnet can be reduced, the forming difficulty of the magnet can be reduced, and the magnetic property and the yield of the magnet can be improved.
In a specific embodiment, in the shaping step, the magnetizing is performed in a magnetizing machine, the magnetizing field is 1.5-1.8T, and when the current of the magnetizing machine is stabilized at the same value, the magnetizing is finished.
Through adopting above-mentioned technical scheme, in the above-mentioned magnetic field scope, not only can make the magnet reach more than 98% of saturation magnetization, moreover, can reduce the magnet and take place to break at the magnetization in-process to further reduce the shaping degree of difficulty of magnet, improve the magnetic property and the yields of magnet.
In a specific embodiment, the molding step maintains the magnetizing field constant, and then performs mold clamping and demolding.
By adopting the technical scheme, magnetizing, die closing pressing and demolding are carried out in a constant magnetic field, so that the magnet can be kept stable in the pressing and demolding process, the internal cracking or breakage of the magnet is further reduced, and the magnet is convenient to form.
In a specific embodiment, in the molding step, the mold clamping is performed at a molding pressure of 10 to 15MPa.
By adopting the technical scheme, the blank with higher density can be obtained under the forming pressure, and the deformation of the blank in the sintering process can be reduced. Moreover, the obtained blank is not easy to generate internal cracking or rupture.
In a specific embodiment, in the molding step, the upper die and the lower die are moved synchronously for 2-3 seconds during demolding, the speed of the lower die is kept unchanged, the speed of the upper die is increased, and when the upper die and the lower die are completely separated from contact, the material in the lower die is taken out to obtain a blank.
Through adopting above-mentioned technical scheme, earlier with last mould and lower mould synchronous movement, the speed of progressive increase last mould again can make last mould and lower mould break away from slowly, can reduce the circumstances that leads to the magnet to break because of last mould breaks away from fast with the lower mould, helps improving the yields of magnet.
In a specific implementation, in the sintering step, the blank is placed in an isostatic press, isostatic pressing forming is carried out under 160-180MPa, sintering is carried out for 1-1.5h under 1010-1080 ℃, cooling is carried out for 1.5-2.5h under 420-480 ℃, and then cooling is carried out to room temperature, so as to obtain the NdFeB magnet.
Through adopting above-mentioned technical scheme, this application discovers through the experiment that adopts above-mentioned sintering pressure, temperature and time, helps improving the yields of magnet. This is probably because the magnetic powder of specific hydrogen content, component ratio and particle size employed in the present application has a better adaptability to the above sintering conditions under which internal cracking or breakage can be reduced and, furthermore, higher magnetic properties can be obtained.
In a specific embodiment, in the milling step, the mixed powder is added to an air-jet mill and milling is carried out at a classifier rotation speed of 3200 to 4000r/min, and the average particle size of the powder is 0.2 to 0.3 μm.
By adopting the technical scheme, the air flow mill and the rotating speed are adopted, so that not only can the abrasion and pollution be reduced, but also the materials can be homogenized, and the uniformity and quality of the powder are improved. In addition, experiments show that the particle size of the powder is controlled within the range, so that the magnetic performance of the magnet is improved, the yield of the magnet is improved, and the magnetic powder can be better mixed with the antioxidant within the particle size range, oxidation is reduced, and better magnetizing and orienting effects are achieved.
In a specific embodiment, the antioxidant comprises 1 (0.8-1.2) by weight of cetyl alcohol, triphenyl methanol, and zinc stearate in the milling step.
Through adopting above-mentioned technical scheme, this application discovers through the experiment that adopts the component of above-mentioned proportion, can form one deck oxygen barrier film layer on the surface of magnetic powder, helps preventing the oxidation of magnetic powder. In addition, the agglomeration of the magnetic powder can be reduced, and the orientation and the forming of the magnetic powder are facilitated. During sintering, the cracking of the magnet is reduced, and the magnetic performance of the magnet is improved.
In a specific embodiment, in the casting step, the smelting temperature is 1450-1550 ℃ and the thickness of the cast sheet is 0.2-0.45mm.
By adopting the technical scheme, under the smelting temperature and the thickness of the cast sheet, microcrystal or large particles generated in the cast sheet can be reduced, so that the uniformity of the cast sheet material is improved, and hydrogen breaking and grinding can be facilitated, so that the magnetic powder with more uniform granularity can be obtained.
In a specific embodiment, in the hydrogen breaking step, the cast sheet is subjected to hydrogen breaking as follows:
adding the cast sheet into a hydrogen crushing furnace under the argon atmosphere, and then introducing hydrogen into the hydrogen crushing furnace, wherein when the pressure drop rate is less than or equal to 0.05MPa/5min, the hydrogen is absorbed and saturated; then introducing argon into the hydrogen crushing furnace, stopping introducing the argon and discharging the gas in the hydrogen crushing furnace when the pressure in the hydrogen crushing furnace reaches-0.092 to-0.099 MPa; repeating the operation of introducing argon for 2-3 times, vacuumizing the hydrogen crushing furnace, heating the temperature in the hydrogen crushing furnace to 520-560 ℃, preserving heat for 7.5-8.5 hours, ending dehydrogenation, cooling to room temperature, and taking out the material in the hydrogen crushing furnace to obtain coarse powder with the hydrogen content of 1000-1200 ppm.
Through adopting above-mentioned technical scheme, this application is through the experiment issue, adopts above-mentioned technological condition to carry out hydrogen broken, helps obtaining the coarse powder that accords with hydrogen content requirement, moreover, can also improve the granularity uniformity of coarse powder.
In summary, the present application includes at least one of the following beneficial technical effects:
1. the forming method can reduce the occurrence of internal cracking or rupture of the magnet, is beneficial to reducing the forming difficulty of the magnet and improving the magnetic property and yield of the magnet;
2. according to the method, the lubricity of the magnetic powder can be improved, the orientation degree of the magnetic powder is improved, the magnetic powder is facilitated to be molded, and the magnetic property of the magnet is improved by adjusting the weight ratio of the magnetic powder to additives such as aviation gasoline, an antioxidant and the like;
3. according to the method, through improvement of the forming step and the sintering step, internal cracking or breakage of the magnet can be reduced, and the yield of the magnet is improved.
Detailed Description
The present application is described in further detail below in connection with examples and comparative examples.
Examples
Example 1
The embodiment provides a forming method of a neodymium-iron-boron magnet, which adopts the following technical scheme:
a forming method of a neodymium-iron-boron magnet comprises the following steps:
mixing Nd, B and Fe in a weight ratio of 32:1:67, adding the mixture into a smelting furnace, heating the smelting furnace to 1500 ℃, smelting at a constant temperature, obtaining standby materials after smelting, and casting the standby materials into a sheet to obtain a cast sheet with the thickness of 0.38 mm.
And continuously introducing argon into the hydrogen crushing furnace, replacing the gas in the hydrogen crushing furnace with the argon, adding the cast sheet into the hydrogen crushing furnace under the argon atmosphere, discharging the gas in the hydrogen crushing furnace, introducing hydrogen into the hydrogen crushing furnace, and stopping introducing the hydrogen into the hydrogen crushing furnace when the pressure drop rate in the hydrogen crushing furnace is less than or equal to 0.05MPa/5min, namely, the hydrogen absorption is saturated. Then argon is introduced into the hydrogen crushing furnace, and when the pressure in the hydrogen crushing furnace reaches-0.096 MPa, the argon is stopped and the gas in the hydrogen crushing furnace is discharged. Repeating the operation of introducing argon for 2-3 times, vacuumizing the hydrogen crushing furnace, heating the temperature in the hydrogen crushing furnace to 540 ℃, preserving heat for 8 hours, after dehydrogenation, naturally cooling to room temperature, and taking out the material in the hydrogen crushing furnace to obtain coarse powder with the hydrogen content of 1000-1200 ppm.
And uniformly mixing the coarse powder, aviation gasoline and the first part of antioxidant according to the weight ratio of 1000:1:0.6 to obtain mixed powder, adding the mixed powder into an air flow mill, grinding the mixed powder at the rotating speed of a classifying wheel of 3600r/min to obtain powder with the average granularity of 0.25 mu m, and uniformly mixing the powder with the second part of antioxidant according to the weight ratio of 1000:2 to obtain fine powder.
And then sieving the fine powder with a 200-mesh sieve, and removing the screen residue to obtain the NdFeB magnetic powder.
And pouring the neodymium iron boron magnetic powder into a die cavity of a lower die, wherein the lower die is positioned below the upper die. After powder scraping in a die cavity is uniform, the upper die vertically moves downwards, when the upper die is just inserted into the die cavity and is in contact with the lower die, the lower die is driven to move downwards, the speed ratio of the upper die to the lower die is 1:2, when the moving stroke of the lower die reaches 10mm, the upper die and the lower die are simultaneously stopped moving, then the upper die and the lower die are simultaneously transferred into a magnetizing machine, the magnetic field in the magnetizing machine is regulated to 1.7T to start magnetizing, when the current of the magnetizing machine is stabilized at the same value, the magnetizing is stopped, the magnetic field is kept constant, the die closing pressing is carried out, the forming pressure in the pressing process is kept constant to be 13MPa, after the pressing is finished, the upper die and the lower die are simultaneously moved upwards for 3 seconds at the same speed, then the moving speed of the lower die is kept unchanged, the moving speed of the upper die is increased to 2 times of the original speed, and after the upper die and the lower die are completely separated from contact with the lower die, the lower die is stopped moving, the material in the lower die is taken out, and a blank is obtained.
And then placing the blank into an isostatic press, regulating the isostatic pressing pressure in isostatic pressing sintering to 170MPa, performing isostatic pressing, sintering at 1145 ℃ for 1.25h after compression molding, cooling to 450 ℃ for 2h, and naturally cooling to room temperature to obtain the neodymium-iron-boron magnet.
Wherein the antioxidant comprises cetyl alcohol, trityl alcohol and zinc stearate in a weight ratio of 1:1:1.
Example 2
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that coarse powder, aviation gasoline and a first part of antioxidant are uniformly mixed according to a weight ratio of 950:1:0.3, so as to obtain mixed powder.
Example 3
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that coarse powder, aviation gasoline and a first part of antioxidant are uniformly mixed according to the weight ratio of 1050:1:0.9, so as to obtain mixed powder.
Example 4
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that powder and a second antioxidant are uniformly mixed according to a weight ratio of 950:2, and thus fine powder is obtained.
Example 5
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that powder and a second antioxidant are uniformly mixed according to a weight ratio of 1050:2, and thus fine powder is obtained.
Example 6
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that when an upper die is just inserted into a die cavity and is in contact with a lower die, the lower die is driven to move downwards, the speed ratio of the upper die to the lower die is 1:1.5, and when the moving stroke of the lower die reaches 10mm, the upper die and the lower die are stopped moving at the same time.
Example 7
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that when an upper die is just inserted into a die cavity and is in contact with a lower die, the lower die is driven to move downwards, the speed ratio of the upper die to the lower die is 1:2.5, and when the moving stroke of the lower die reaches 10mm, the upper die and the lower die are stopped moving at the same time.
Example 8
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that when an upper die is just inserted into a die cavity and is in contact with a lower die, the lower die is driven to move downwards, the speed ratio of the upper die to the lower die is 1:2, and when the moving stroke of the lower die reaches 8mm, the upper die and the lower die are stopped moving at the same time.
Example 9
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that when an upper die is just inserted into a die cavity and is in contact with a lower die, the lower die is driven to move downwards, the speed ratio of the upper die to the lower die is 1:2, and when the moving stroke of the lower die reaches 12mm, the upper die and the lower die are stopped moving at the same time.
Example 10
The embodiment provides a forming method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the magnetizing is started by adjusting the magnetic field in the magnetizer to 1.5T, and the end of the magnetizing is indicated when the current of the magnetizer is stabilized at the same value.
Example 11
The embodiment provides a forming method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the magnetic field in the magnetizer is adjusted to 1.8T to start magnetization, and when the current of the magnetizer is stabilized at the same value, the magnetization is ended.
Example 12
The embodiment provides a forming method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the magnetic field in the magnetizer is adjusted to 1.4T to start magnetization, and when the current of the magnetizer is stabilized at the same value, the magnetization is ended.
Example 13
The embodiment provides a forming method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the magnetizing is started by adjusting the magnetic field in the magnetizer to 1.9T, and the end of the magnetizing is indicated when the current of the magnetizer is stabilized at the same value.
Example 14
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that when the current of a to-be-magnetized machine is stabilized at the same value, the magnetization is stopped, the magnetic field is adjusted to be 1.5T, and mold closing pressing is performed.
Example 15
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that when the current of a to-be-magnetized machine is stabilized at the same value, the end of magnetization is indicated, the magnetic field is adjusted to be 1.8T, and mold closing and pressing are performed.
Example 16
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the molding pressure in the pressing process is constant at 10MPa.
Example 17
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the molding pressure in the pressing process is constant at 15MPa.
Example 18
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the molding pressure in the pressing process is constant at 9MPa.
Example 19
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the molding pressure in the pressing process is constant at 16MPa.
Example 20
The embodiment provides a forming method of a neodymium iron boron magnet, which is different from embodiment 1 only in that after pressing is finished, a lower die is kept motionless, an upper die is moved upwards, and after the upper die and the lower die are completely separated from contact, materials in the lower die are taken out, so that a blank is obtained.
Example 21
The embodiment provides a forming method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the isostatic pressing pressure in isostatic pressing sintering is adjusted to 160MPa, isostatic pressing is carried out, after the isostatic pressing forming, sintering is carried out for 1.5 hours at 1010 ℃, cooling is carried out to 450 ℃ for annealing for 2.5 hours, and natural cooling is carried out to room temperature, thus obtaining the neodymium iron boron magnet.
Example 22
The embodiment provides a forming method of a neodymium-iron-boron magnet, which is different from embodiment 1 only in that the isostatic pressing pressure in isostatic pressing sintering is adjusted to 180MPa, isostatic pressing is carried out, after the isostatic pressing forming, sintering is carried out for 1h at 1080 ℃, cooling is carried out to 480 ℃ for annealing for 1.5h, and then natural cooling is carried out to room temperature, thus obtaining the neodymium-iron-boron magnet.
Example 23
The embodiment provides a forming method of a neodymium-iron-boron magnet, which is different from embodiment 1 only in that the isostatic pressing pressure in isostatic pressing sintering is adjusted to 150MPa, isostatic pressing is carried out, after the isostatic pressing forming, sintering is carried out for 2 hours at 1045 ℃, cooling is carried out to 400 ℃, annealing is carried out for 3 hours, and natural cooling is carried out to room temperature, thus obtaining the neodymium-iron-boron magnet.
Example 24
The embodiment provides a forming method of a neodymium-iron-boron magnet, which is different from embodiment 1 only in that the isostatic pressing pressure in isostatic pressing sintering is adjusted to 190MPa, isostatic pressing is carried out, after the isostatic pressing forming, sintering is carried out for 0.5h at 1045 ℃, cooling is carried out for 1h at 500 ℃, and natural cooling is carried out to room temperature, thus obtaining the neodymium-iron-boron magnet.
Example 25
The present example provided a molding method of neodymium-iron-boron magnet, which was different from example 1 only in that the mixed powder was added to an air flow mill, and the milling was performed at a classifier rotation speed of 3200r/min to obtain a powder having an average particle size of 0.3 μm.
Example 26
The present example provided a molding method of neodymium-iron-boron magnet, which was different from example 1 only in that the mixed powder was added to an air flow mill, and the milling was performed at a classifier rotation speed of 4000r/min to obtain powder having an average particle size of 0.2 μm.
Example 27
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that after a smelting furnace is heated to 1450 ℃, the smelting is performed at a constant temperature, standby materials are obtained after the smelting is finished, and the standby materials are cast into a sheet to obtain a cast sheet with the thickness of 0.2 mm.
Example 28
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that after a smelting furnace is heated to 1550 ℃, the smelting furnace is smelted at a constant temperature, standby materials are obtained after the smelting is finished, and the standby materials are cast into a sheet to obtain a cast sheet with the thickness of 0.45mm.
Example 29
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that argon is then introduced into a hydrogen crushing furnace, and when the pressure in the hydrogen crushing furnace reaches-0.092 MPa, the introduction of argon is stopped and the gas in the hydrogen crushing furnace is discharged. Repeating the operation of introducing argon for 2 times, vacuumizing the hydrogen crushing furnace, heating the temperature in the hydrogen crushing furnace to 520 ℃, preserving heat for 8.5 hours, stopping dehydrogenation, naturally cooling to room temperature, and taking out the materials in the hydrogen crushing furnace to obtain coarse powder with the hydrogen content of 1000-1200 ppm.
Example 30
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that argon is then introduced into a hydrogen crushing furnace, and when the pressure in the hydrogen crushing furnace reaches-0.099 MPa, the introduction of argon is stopped and the gas in the hydrogen crushing furnace is discharged. Repeating the operation of introducing argon for 3 times, vacuumizing the hydrogen crushing furnace, heating the temperature in the hydrogen crushing furnace to 560 ℃, preserving heat for 7.5 hours, stopping dehydrogenation, naturally cooling to room temperature, and taking out the materials in the hydrogen crushing furnace to obtain coarse powder with the hydrogen content of 1000-1200 ppm.
Example 31
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the antioxidant comprises cetyl alcohol, triphenyl methanol and zinc stearate in a weight ratio of 1:0.8:0.8.
Example 32
The embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the antioxidant comprises cetyl alcohol, trityl alcohol and zinc stearate in a weight ratio of 1:1.2:1.2.
Example 33
The present embodiment provides a molding method of a neodymium iron boron magnet, which is different from embodiment 1 only in that the antioxidant is an antioxidant of model VOK-NOX C3.
Example 34
The embodiment provides a forming method of a neodymium-iron-boron magnet, which is different from embodiment 1 only in that after fine powder is sieved by a 300-mesh sieve, screen residues are removed, and the neodymium-iron-boron magnetic powder is obtained.
Comparative example
Comparative example 1
The comparative example provides a molding method of a neodymium iron boron magnet, which is different from example 1 only in that coarse powder, aviation gasoline and a first part of antioxidant are uniformly mixed according to the weight ratio of 900:1:0.5 to obtain mixed powder, then the mixed powder is added into an air flow mill, grinding is carried out at the rotating speed of a classifying wheel of 3600r/min to obtain powder with the average granularity of 0.25 mu m, and then the powder and a second part of antioxidant are uniformly mixed according to the weight ratio of 900:2 to obtain fine powder.
Comparative example 2
The comparative example provides a molding method of a neodymium iron boron magnet, which is different from example 1 only in that coarse powder, aviation gasoline and a first part of antioxidant are uniformly mixed according to the weight ratio of 1100:1:1 to obtain mixed powder, then the mixed powder is added into an air flow mill, grinding is carried out at the rotating speed of a classifying wheel of 3600r/min to obtain powder with the average granularity of 0.25 mu m, and then the powder and a second part of antioxidant are uniformly mixed according to the weight ratio of 1100:2 to obtain fine powder.
Comparative example 3
This comparative example provides a molding method of a neodymium iron boron magnet, which is different from example 1 only in that when an upper die is just inserted into a cavity and is in contact with a lower die, the lower die is driven to move downward, the speed ratio of the upper die to the lower die is 1:1.3, and when the moving stroke of the lower die reaches 7mm, the upper die and the lower die are stopped to move at the same time.
Comparative example 4
This comparative example provides a molding method of a neodymium iron boron magnet, which is different from example 1 only in that when an upper die is just inserted into a cavity and is in contact with a lower die, the lower die is driven to move downward, the speed ratio of the upper die to the lower die is 1:2.7, and when the moving stroke of the lower die reaches 13mm, the upper die and the lower die are stopped to move at the same time.
Comparative example 5
This comparative example provides a molding method of neodymium-iron-boron magnet, which is different from example 1 only in that fine powder is not sieved, and neodymium-iron-boron magnetic powder is directly obtained.
Comparative example 6
This comparative example provides a molding method of neodymium iron boron magnet, which is different from example 1 only in that sintered neodymium iron boron hydrogen powder with the brand of N38M is poured into a mold cavity of a lower mold, and the lower mold is positioned below an upper mold. After powder scraping in a die cavity is uniform, the upper die vertically moves downwards, when the upper die is just inserted into the die cavity and is in contact with the lower die, the lower die is driven to move downwards, the speed ratio of the upper die to the lower die is 1:2, when the moving stroke of the lower die reaches 10mm, the upper die and the lower die are simultaneously stopped moving, then the upper die and the lower die are simultaneously transferred into a magnetizing machine, the magnetic field in the magnetizing machine is regulated to 1.7T to start magnetizing, when the current of the magnetizing machine is stabilized at the same value, the magnetizing is stopped, the magnetic field is kept constant, the die closing pressing is carried out, the forming pressure in the pressing process is kept constant to be 13MPa, after the pressing is finished, the upper die and the lower die are simultaneously moved upwards for 3 seconds at the same speed, then the moving speed of the lower die is kept unchanged, the moving speed of the upper die is increased to 2 times of the original speed, and after the upper die and the lower die are completely separated from contact with the lower die, the lower die is stopped moving, the material in the lower die is taken out, and a blank is obtained.
And then placing the blank into an isostatic press, regulating the isostatic pressing pressure in isostatic pressing sintering to 170MPa, performing isostatic pressing, sintering at 1045 ℃ for 1.25h after compression molding, cooling to 450 ℃ for 2h, and naturally cooling to room temperature to obtain the neodymium-iron-boron magnet.
Performance test
For the neodymium-iron-boron magnets prepared in examples 1 to 34 and comparative examples 1 to 6, the magnetic properties and the appearance thereof were tested according to GB/T34495-2017, the neodymium-iron-boron magnet having no crack or defect in appearance was good, the neodymium-iron-boron magnet having crack or defect in appearance was defective, and the yields of each example and comparative example were calculated as yield = number of good/number of defective + number of defective ×100%, and the detection results are shown in Table 1.
TABLE 1
As can be seen from the combination of example 1 and comparative examples 1 to 6 and table 1, at least one of the magnetic properties or yield of comparative examples 1 to 6 is lower than that of example 1, which means that the process conditions and the molding method of example 1 help to improve both the yield and the magnetic properties of the neodymium-iron-boron magnet.
As can be seen from the combination of examples 1 to 34 and table 1, the magnetic properties of examples 1 to 11, examples 16 to 17, examples 21 to 22, examples 25 to 32 and example 34 are less different from each other, and the yield is 95% or more; however, the magnetic properties or yields of examples 12-15, examples 18-20, examples 23-24, and example 33 were at least one of lower. This demonstrates that under the process conditions and forming methods of examples 1-11, examples 16-17, examples 21-22, examples 25-32, and example 34, it is helpful to further improve the yield and magnetic properties of the neodymium-iron-boron magnet.
The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.
Claims (10)
1. The forming method of the neodymium-iron-boron magnet is characterized by comprising the following steps of:
casting: smelting raw materials, and casting the raw materials into a sheet to obtain a cast sheet;
breaking hydrogen: carrying out hydrogen breaking on the cast sheet to obtain coarse powder with the hydrogen content of 1000-1200 ppm;
grinding: uniformly mixing coarse powder, aviation gasoline and a first part of antioxidant according to the weight ratio of (950-1050) 1 (0.3-0.9) to obtain mixed powder, grinding the mixed powder to obtain powder, and mixing the powder with a second part of antioxidant according to the weight ratio of (950-1050) 2 to obtain fine powder;
and (3) screening: sieving the fine powder with 200-300 mesh sieve, and removing the screen residue to obtain neodymium iron boron magnetic powder;
and (3) forming: pouring neodymium iron boron magnetic powder into a die cavity of a lower die, uniformly scraping powder, moving an upper die towards a direction close to the lower die, moving the upper die and the lower die in the same direction at a speed ratio of 1 (1.5-2.5) after the upper die moves to be in contact with the die cavity, stopping moving the upper die and the lower die when the moving stroke of the lower die reaches 8-12mm, then starting magnetizing, closing the upper die and the lower die, pressing, and demoulding to obtain a blank after the pressing is finished;
sintering: and carrying out isostatic pressing sintering on the blank to obtain the neodymium-iron-boron magnet.
2. The method according to claim 1, wherein in the step of forming, the magnetizing is performed in a magnetizing machine, the magnetizing field is 1.5-1.8T, and the magnetizing is completed when the current of the magnetizing machine is stabilized at the same value.
3. The method of claim 2, wherein in the forming step, the magnetizing field is kept constant, and then the die assembly pressing and the die release are performed.
4. The method of claim 1, wherein in the molding step, the die-closing pressing is performed at a molding pressure of 10 to 15MPa.
5. The method of forming a neodymium iron boron magnet according to claim 4, wherein in the forming step, the upper die and the lower die are moved synchronously for 2-3 seconds during demolding, the speed of the lower die is kept unchanged, the speed of the upper die is increased, and when the upper die and the lower die are completely separated from contact, the material in the lower die is taken out to obtain a blank.
6. The method for forming a neodymium-iron-boron magnet according to claim 1, wherein in the sintering step, the blank is placed into an isostatic press, isostatic pressing forming is carried out under 160-180MPa, sintering is carried out for 1-1.5h under 1010-1080 ℃, cooling is carried out for 1.5-2.5h under 420-480 ℃, and cooling is carried out to room temperature to obtain the neodymium-iron-boron magnet.
7. The method according to claim 1, wherein in the pulverizing step, the mixed powder is added into an air flow mill, and the powder is pulverized at a classifier rotation speed of 3200-4000r/min, wherein the average particle size of the powder is 0.2-0.3 μm.
8. The method of forming a neodymium-iron-boron magnet according to claim 1, wherein in the grinding step, the antioxidant comprises cetyl alcohol, trityl alcohol and zinc stearate in a weight ratio of 1 (0.8-1.2).
9. The method of claim 1, wherein in the casting step, the melting temperature is 1450-1550 ℃, and the thickness of the cast sheet is 0.2-0.45mm.
10. The method for forming a neodymium iron boron magnet according to claim 1, wherein in the hydrogen breaking step, the cast sheet is subjected to hydrogen breaking according to the following steps:
adding the cast sheet into a hydrogen crushing furnace under the argon atmosphere, and then introducing hydrogen into the hydrogen crushing furnace, wherein when the pressure drop rate is less than or equal to 0.05MPa/5min, the hydrogen is absorbed and saturated; then argon is introduced into the hydrogen crushing furnace, and when the pressure in the hydrogen crushing furnace reaches-0.092 to-0.099 MPa, the argon is stopped to be introduced and the gas in the hydrogen crushing furnace is discharged; repeating the operation of introducing argon for 2-3 times, vacuumizing the hydrogen crushing furnace, heating the temperature in the hydrogen crushing furnace to 520-560 ℃, preserving heat for 7.5-8.5 hours, ending dehydrogenation, cooling to room temperature, and taking out the material in the hydrogen crushing furnace to obtain coarse powder with the hydrogen content of 1000-1200 ppm.
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