CN112908676A - Permanent magnetic ferrite magnetic powder for dry pressing molding and preparation method thereof - Google Patents
Permanent magnetic ferrite magnetic powder for dry pressing molding and preparation method thereof Download PDFInfo
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- 239000006247 magnetic powder Substances 0.000 title claims abstract description 68
- 229910000859 α-Fe Inorganic materials 0.000 title claims abstract description 52
- 238000003825 pressing Methods 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000000465 moulding Methods 0.000 title claims description 11
- 239000002002 slurry Substances 0.000 claims abstract description 45
- 238000000227 grinding Methods 0.000 claims abstract description 33
- 238000001035 drying Methods 0.000 claims abstract description 27
- 239000000843 powder Substances 0.000 claims abstract description 26
- 239000000463 material Substances 0.000 claims abstract description 18
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- 238000010979 pH adjustment Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 25
- 238000005245 sintering Methods 0.000 claims description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 12
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 10
- 229910000831 Steel Inorganic materials 0.000 claims description 8
- 239000010959 steel Substances 0.000 claims description 8
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 5
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 5
- 239000000377 silicon dioxide Substances 0.000 claims description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 229910052681 coesite Inorganic materials 0.000 claims description 3
- 229910052593 corundum Inorganic materials 0.000 claims description 3
- 229910052906 cristobalite Inorganic materials 0.000 claims description 3
- 229910052746 lanthanum Inorganic materials 0.000 claims description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 3
- 229910052682 stishovite Inorganic materials 0.000 claims description 3
- 229910052905 tridymite Inorganic materials 0.000 claims description 3
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 3
- 239000006185 dispersion Substances 0.000 abstract description 6
- 230000005389 magnetism Effects 0.000 abstract description 6
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 12
- 238000012360 testing method Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 229910000018 strontium carbonate Inorganic materials 0.000 description 5
- 238000002156 mixing Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000018044 dehydration Effects 0.000 description 3
- 238000006297 dehydration reaction Methods 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- 230000005415 magnetization Effects 0.000 description 3
- 238000000498 ball milling Methods 0.000 description 2
- 239000004327 boric acid Substances 0.000 description 2
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- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 2
- 235000012054 meals Nutrition 0.000 description 2
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- 238000003756 stirring Methods 0.000 description 2
- DSSYKIVIOFKYAU-XVKPBYJWSA-N (1s,4r)-4,7,7-trimethylbicyclo[2.2.1]heptan-3-one Chemical compound C1C[C@@]2(C)C(=O)C[C@H]1C2(C)C DSSYKIVIOFKYAU-XVKPBYJWSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 235000013539 calcium stearate Nutrition 0.000 description 1
- 239000008116 calcium stearate Substances 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
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- 239000000696 magnetic material Substances 0.000 description 1
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- 230000005405 multipole Effects 0.000 description 1
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- 238000012545 processing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000001238 wet grinding Methods 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
-
- 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
- H01F1/06—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 in the form of particles, e.g. powder
- H01F1/08—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 in the form of particles, e.g. powder pressed, sintered, or bound together
-
- 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
- H01F1/12—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 soft-magnetic materials
- H01F1/34—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 soft-magnetic materials non-metallic substances, e.g. ferrites
- H01F1/342—Oxides
- H01F1/344—Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
- Hard Magnetic Materials (AREA)
Abstract
The invention belongs to the technical field of permanent magnetic ferrite, and particularly relates to a preparation method of permanent magnetic ferrite magnetic powder for dry pressing forming, which comprises the following steps: (1) fine grinding: carrying out wet fine grinding on the coarse powder of the permanent magnetic ferrite pre-sintered material and the additive until the average particle size is 0.6-1.2 microns to obtain slurry; (2) adjusting the pH value of the slurry: adjusting the pH value of the slurry to 7.0-9.0; (3) dewatering and drying: dehydrating the slurry after pH adjustment, and then drying the slurry through a drying kiln to obtain dried magnetic powder; (4) grinding: grinding the magnetic powder by a dry ball mill; (5) dispersing: and dispersing the ground magnetic powder by adopting a high-speed crusher to obtain the permanent magnetic ferrite magnetic powder. The invention improves the dispersion characteristic of magnetic powder, improves the relative orientation degree and density of the corresponding sintered magnet, and effectively improves the residual magnetism Br of the magnet.
Description
Technical Field
The invention belongs to the technical field of permanent magnetic ferrite, and particularly relates to permanent magnetic ferrite magnetic powder for dry pressing and a preparation method thereof.
Background
The permanent ferrite device is formed by dry pressing and wet pressing.
The performance of products produced by a wet pressing method is high and stable, but the finished product rate of the formed blank is low because the dehydration is difficult to control, and some products with complex shapes are even difficult to press by a wet method. In addition, the wet pressing method has the disadvantages of complicated forming process, slow pressing rate, low productivity, etc.
The dry pressing method is a method of filling a dry permanent magnetic ferrite material powder into a molding cavity and molding in a magnetic field. Because the dehydration is not needed, the forming device has simple structure, high pressing speed and higher production efficiency, and is easy to realize automatic forming. In addition, the finished product has smooth and flat surface, does not need to be fettled, and greatly reduces grinding amount, so the method has more advantages than a wet pressing method, and is particularly suitable for special-shaped devices and small devices which are difficult to produce by a wet method. With the increasing development of electronic information technology, various electronic devices have higher and higher requirements on magnetic functional elements matched with the electronic devices, which are specifically represented by increasingly complex shapes, gradually reduced volumes and increasingly higher processing precision.
The dry-pressed anisotropic ferrite is mainly applied to the field of micromotors, is mainly used as a core component of high-grade permanent magnet synchronous motors, permanent magnet stepping motors and direct-current brushless motors, and can be specifically made into devices such as multi-pole magnetic rings, micro magnetic shoes and the like. The motors are widely applied to the fields of automobiles, computers and communication products, office automation equipment, instruments and meters, teaching instruments, household appliances, variable frequency air conditioner motors, precision motors, small motors, daily consumer goods, laser printer magnetic rollers, sensors, breakers and the like.
There are many studies on ferrites, for example:
patent document No. CN104496452B discloses a ferrite preparation method, comprising the following steps: preparing a ferrite pre-sintering material and carrying out wet crushing treatment to obtain ferrite pre-sintering material slurry; drying the ferrite pre-fired material slurry; carrying out vibration grinding treatment on the ferrite pre-sintering material dry powder for 20-40 minutes by using a vibration grinding machine; performing high-speed dispersion treatment on the powder after vibromilling; uniformly mixing the ferrite pre-sintering material powder after high-speed dispersion with an adhesive, and placing the mixture in a magnetic field for dry pressing to obtain a formed ferrite; and sintering the formed ferrite to obtain the high-performance dry-formed sintered permanent magnetic ferrite.
The journal literature of the influence of process parameters on the performance of dry-pressed anisotropic permanent magnetic ferrite discloses that the conventional production method is adopted to prepare dry-pressed permanent magnetic ferrite magnetic powder, and SiO is added in the formula by regulating and controlling the molar ratio of raw materials2And the influence of factors such as the particle size of magnetic powder and the like on the magnetic performance of the magnet is researched, and the performance of the magnet with higher magnetic performance is prepared.
Patent publication No. CN105622082A discloses a method for preparing anisotropic dry-pressed powder of permanent magnetic ferrite, in which a slurry after fine grinding is subjected to wet forming and simultaneously has orientation, and then is dried and crushed to obtain magnetic particles with pre-magnetization characteristics.
However, the relative orientation degree of the current permanent magnetic ferrite magnetic powder dry-pressed sintered magnet is only 90-92%. Compared with a wet pressing forming mode, the dry pressing forming mode has the problems of low magnet density and low magnetic powder orientation degree. Wherein, the ratio of the residual magnetism Br of the dry-pressed sintered magnet of the permanent magnetic ferrite to the residual magnetism Br of the wet-pressed sintered magnet of the corresponding magnetic powder is called as the relative orientation degree.
Disclosure of Invention
Based on the above disadvantages and shortcomings of the prior art, it is an object of the present invention to at least solve one or more of the above problems of the prior art, in other words, to provide a permanent magnetic ferrite magnetic powder for dry pressing and a method for preparing the same, which satisfies one or more of the above requirements.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of permanent magnetic ferrite magnetic powder for dry pressing molding comprises the following steps:
(1) fine grinding: carrying out wet fine grinding on the coarse powder of the permanent magnetic ferrite pre-sintered material and the additive until the average particle size is 0.6-1.2 microns to obtain slurry;
(2) adjusting the pH value of the slurry: adjusting the pH value of the slurry to 7.0-9.0;
(3) dewatering and drying: dehydrating the slurry after pH adjustment, and then drying the slurry through a drying kiln to obtain dried magnetic powder;
(4) grinding: grinding the magnetic powder by a dry ball mill;
(5) dispersing: and dispersing the ground magnetic powder by adopting a high-speed crusher to obtain the permanent magnetic ferrite magnetic powder.
Preferably, in the step (2), air or carbon dioxide gas is introduced into the slurry to adjust the pH of the slurry to 7.0-9.0.
Preferably, in the step (1), Fe is further added in the wet fine grinding process2O3。
Preferably, the Fe2O3The addition amount of (B) is 0.01-0.2% of the weight of the coarse powder of the permanent magnetic ferrite pre-sintering material.
Preferably, the additive comprises CaCO3、SiO2、H3BO3、Al2O3One or more of (a).
Preferably, in the step (3), the drying temperature of the drying kiln is not higher than 600 ℃.
Preferably, in the step (3), the moisture in the dried magnetic powder is less than 0.5 wt%.
Preferably, in the step (4), the weight ratio of the steel ball to the magnetic powder is 2-10: 1.
preferably, the diameter of the steel ball is 4-8 mm.
Preferably, the coarse powder of the permanent magnetic ferrite pre-sintering material contains lanthanum and cobalt.
The invention also provides the permanent magnetic ferrite magnetic powder for dry pressing molding prepared by the preparation method of any scheme.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method of the permanent magnetic ferrite magnetic powder for dry pressing molding adopts a novel preparation process, improves the dispersion characteristic of the magnetic powder, improves the relative orientation degree and density of a corresponding sintered magnet, and effectively improves the residual magnetism Br of the magnet.
Drawings
FIG. 1 is a flow chart of a conventional dry-pressed ferrite magnetic powder production process;
FIG. 2 is a schematic diagram of a poorly dispersed grain arrangement;
FIG. 3 is a schematic diagram of an ideal magnet grain arrangement;
fig. 4 is a flowchart of the method for producing the permanent magnetic ferrite magnetic powder for dry compacting in example 1 of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following specific examples.
The main factors influencing the remanence Br of the magnetic powder include the orientation degree eta, the saturation magnetization intensity Ms of the magnetic powder, the magnet density rho and the like, and are shown in the formula:
Br∝Ms×η×ρ
from this, it is known that increasing the saturation magnetization of magnetic powder, increasing the degree of orientation of magnetic powder, and increasing the magnet density are main means for increasing the residual magnetism Br of a sintered magnet.
In the conventional dry-pressing ferrite magnetic powder production process, as shown in fig. 1, coarse powder is subjected to wet grinding to obtain slurry, and then the slurry is sequentially subjected to dehydration, drying and dispersion to obtain magnetic powder. In the formulation of the pre-sinter, Fe to promote ferrite formation2O3The molar ratio of SrO to SrO is generally less than 6, namely SrO has surplus; meanwhile, in the ferrite process of the pre-sintering process, ferrite is not completely generated, and a small amount of residual SrO remains without reaction. In the subsequent wet fine grinding process, the residual SrO reacts with water to generate Sr (OH)2Therefore, the pH value of the slurry after fine grinding is 9-12. The research of the invention discovers that Sr (OH) in the slurry2The magnetic powder can be condensed on the surface of the magnetic powder in the drying process, so that the hardening of the magnetic powder particles is caused; the hardened grains of the magnetic powder are hard to be disentangled in the subsequent high-speed pulverization process, thereby causing the reduction of the orientation degree of the magnetic powder and the density of the magnet in the molding processThe decrease affects the remanence Br of the magnetic powder, as shown in fig. 2, which is a poorly dispersed grain arrangement, and fig. 3 is an ideal magnet grain arrangement.
The research of the invention finds that the pH value of the slurry can be reduced to 7.0-9.0 by introducing air or carbon dioxide gas into the slurry, and the mechanism is Sr (OH)2With CO2Reaction to form SrCO3Thereby eliminating Sr (OH) in water2And the hardening of magnetic powder in the drying process is avoided.
In addition, a small amount of Fe was added during fine grinding2O3During sintering, Fe2O3With SrCO3A reaction occurs to reduce the content of non-magnetic phases and increase the residual magnetism Br of the magnet.
In addition, in the drying process of the magnetic powder, the drying temperature of the magnetic powder also has great influence on the hardening of the magnetic powder. According to the invention, after drying, the magnetic powder is ground in a dry manner by using the ball mill, so that the hardening among the magnetic powder can be effectively damaged, and the dispersion state of the magnetic powder is improved.
Example 1:
as shown in fig. 4, the method for preparing the permanent magnetic ferrite powder for dry pressing according to the embodiment includes the following steps:
(1) preparation of the meal
Iron oxide red and strontium carbonate are mixed according to a molar ratio (Fe)2O3With SrCO3Molar ratio) 5.90: 1, burdening, adding silicon dioxide which accounts for 0.15 wt% of the base weight of the iron oxide red, uniformly mixing, pelletizing, presintering at 1295 ℃, and preserving heat for 60 minutes to obtain presintering material balls; and after cooling, coarsely crushing the pre-sintered material balls to obtain coarse powder with the average particle size of 3-6 microns.
(2) Fine grinding
Based on the weight of the coarse powder, 1.20 wt% of calcium carbonate, 0.25 wt% of silicon oxide, 0.15 wt% of boric acid and 0.10 wt% of iron oxide red are added; then adding the mixture into a ball mill, adding water and carrying out ball milling until the average particle size is 0.80 micron to obtain slurry. The pH of the slurry was measured to be 11.2.
(3) pH adjustment of slurry
Introducing CO into the slurry2Gas and materialStirring the slurry until the pH of the slurry reaches 7.80, and stopping introducing CO2And (5) gas to obtain low-pH slurry.
(4) Dehydrating and drying
And dehydrating the slurry with low pH value by a dehydrator or a filter press, and then drying in a drying kiln at the drying temperature of 450 ℃ until the moisture of the dried magnetic powder is 0.25 wt%, thereby obtaining the dried magnetic powder.
(5) Grinding
A dry ball mill is adopted, steel balls with the diameter of 8.0mm are filled in the dry ball mill, and the dried magnetic powder is ground;
wherein, the weight ratio of the steel ball to the magnetic powder is 8.0: 1, grinding for 60 minutes.
The test magnet powder had an average particle size of 0.79 microns.
(6) Dispersing
And dispersing the magnetic powder by adopting a high-speed pulverizer to obtain the final permanent magnetic ferrite magnetic powder for dry pressing.
The differences between examples 2 to 5 and example 1 are shown in table 1, and the others are the same as example 1.
Example 6:
the preparation method of the permanent magnetic ferrite magnetic powder for dry pressing molding comprises the following steps:
(1) preparation of the meal
Adopting iron oxide red, strontium carbonate, lanthanum oxide and cobalt oxide as raw materials according to Sr0.8La0.2Fe11.67Co0.13O19Burdening, adding silicon dioxide which accounts for 0.10 wt% of the base weight of the iron oxide red, uniformly mixing, pelletizing, presintering at 1285 ℃, and preserving heat for 60 minutes to obtain presintering material balls; and after cooling, coarsely crushing the pre-sintered material balls to obtain coarse powder with the average particle size of 3-6 microns.
(2) Fine grinding
Based on the weight of the coarse powder, 1.0 weight percent of calcium carbonate, 0.25 weight percent of silicon oxide, 0.10 weight percent of boric acid and 0.10 weight percent of iron oxide red are added; then adding the mixture into a ball mill, adding water and carrying out ball milling until the average particle size is 0.79 micron to obtain slurry. The pH of the slurry was measured to be 10.6.
(3) pH adjustment
Introducing CO into the slurry2Gas, stirring the slurry until the pH of the slurry reaches 7.50, and stopping introducing CO2And (5) gas to obtain low-pH slurry.
(4) Dehydrating and drying
And dehydrating the slurry with low pH value by a dehydrator, and then drying in a drying kiln at the drying temperature of 450 ℃ until the moisture content of the dried magnetic powder is 0.27 wt%, so as to obtain the dried magnetic powder.
(5) Grinding
A dry ball mill is adopted, steel balls with the diameter of 8.0mm are filled in the dry ball mill, and the dried magnetic powder is ground;
wherein, the weight ratio of the steel ball to the magnetic powder is 8.0: 1, grinding for 60 minutes.
The test magnet powder had an average particle size of 0.77 μm.
(6) Dispersing
And dispersing the magnetic powder by adopting a high-speed pulverizer to obtain the final permanent magnetic ferrite magnetic powder for dry pressing.
See table 1 for specific parameters for comparative examples 1-6.
The average particle size measurements were analyzed using a WLP 205 model instrument.
The dry press forming tests of the above examples 1-6 and comparative examples 1-6 were carried out by the following procedures:
(a) mixing 150 g of magnetic powder, 1.0 wt% of camphor powder and 0.30 wt% of calcium stearate, and stirring uniformly by using a high-speed stirrer;
(b) taking 40 g of mixed sample powder, putting the sample powder into a die with the diameter of 34mm, and forming on a dry pressing forming machine, wherein the pressing pressure is 3.5MPa, the pressure maintaining time is 5 seconds, and the magnetic field filling amount is 5000Gs, so that a green body is obtained;
(c) sintering the green body by adopting a box-type resistance furnace, wherein the sintering temperature is 1235 ℃, and keeping the temperature for 120 minutes;
(d) grinding: and after sintering, grinding the upper surface and the lower surface of the sintered block by using a grinder until the upper surface and the lower surface are smooth to obtain the sintered block.
(e) And (3) detection: testing the density of the sintered block by adopting a drainage method; and testing the magnetic property of the sintered block by using a B-H tester. See table 1 for specific test results.
The wet-press forming tests of the above examples 1 to 6 and comparative examples 1 to 6 were carried out by the following procedures:
(a) a 100-ton magnetic material wet pressing forming machine is adopted as pressing equipment; the diameter of the die cavity is 45 mm.
(b) Filling the slurry into the die cavity, and then pressing and forming; the pressing pressure was 6.5MPa, the dwell time was 10 seconds, and the orientation magnetic field strength was 9000 Gs.
(c) And sintering the green body by adopting a box-type resistance furnace, wherein the sintering temperature is 1235 ℃, and the heat preservation time is 120 minutes.
(d) Grinding: and after sintering, grinding the upper surface and the lower surface of the sintered block by using a grinder until the upper surface and the lower surface are smooth to obtain the sintered block.
(e) And (3) detection: testing the density of the sintered block by adopting a drainage method; and testing the magnetic property of the sintered block by using a B-H tester. See table 1 for specific test results.
TABLE 1 comparison of the process parameters and Performance measurements for the examples and comparative examples
Wherein, the coarse powder adopted by the examples 2-5 and the comparative examples 1-5 is the same as the example 1.
Comparative example 6 and example 6, the same coarse powder was used, and contained lanthanum and cobalt components.
In the embodiment and the alternative scheme thereof, the average particle size after fine grinding can be controlled to be other particle sizes between 0.6 and 1.2 micrometers, and is determined according to actual requirements.
In the above embodiment and its alternatives, the target value of the pH adjustment of the slurry can be arbitrarily determined between 7.0 and 9.0.
In the above examples and alternatives, during the fine grinding, Fe2O3The addition amount of the permanent magnetic ferrite pre-sintering material can be determined at will within 0.01-0.2% of the weight of the coarse powder of the permanent magnetic ferrite pre-sintering material.
In the above embodiments and alternatives, the additive may also be CaCO3、SiO2、H3BO3、Al2O3Any one or more of them, in particular according to the actual requirements.
In the above embodiment and its alternatives, the weight ratio of the steel ball to the magnetic powder may also be 2: 1. 4: 1. 6: 1. 10: 1, etc.
The foregoing has outlined rather broadly the preferred embodiments and principles of the present invention and it will be appreciated that those skilled in the art may devise variations of the present invention that are within the spirit and scope of the appended claims.
Claims (10)
1. A preparation method of permanent magnetic ferrite magnetic powder for dry pressing molding is characterized by comprising the following steps:
(1) fine grinding: carrying out wet fine grinding on the coarse powder of the permanent magnetic ferrite pre-sintered material and the additive until the average particle size is 0.6-1.2 microns to obtain slurry;
(2) adjusting the pH value of the slurry: adjusting the pH value of the slurry to 7.0-9.0;
(3) dewatering and drying: dehydrating the slurry after pH adjustment, and then drying the slurry through a drying kiln to obtain dried magnetic powder;
(4) grinding: grinding the magnetic powder by a dry ball mill;
(5) dispersing: and dispersing the ground magnetic powder by adopting a high-speed crusher to obtain the permanent magnetic ferrite magnetic powder.
2. The method according to claim 1, wherein in the step (2), air or carbon dioxide gas is introduced into the slurry to adjust the pH of the slurry to 7.0-9.0.
3. The method according to claim 1, wherein in the step (1), Fe is further added during the wet fine grinding2O3。
4. The method according to claim 3, wherein the Fe2O3Is added in an amount ofIs 0.01 to 0.2 percent of the weight of the coarse powder of the permanent magnetic ferrite pre-sintering material.
5. The method of claim 1, wherein the additive comprises CaCO3、SiO2、H3BO3、Al2O3One or more of (a).
6. The method according to claim 1, wherein in the step (3), the temperature of the drying kiln is not higher than 600 ℃.
7. The method according to claim 1, wherein in the step (3), moisture in the dried magnetic powder is less than 0.5 wt%.
8. The preparation method according to claim 1, wherein in the step (4), the weight ratio of the steel ball to the magnetic powder is 2-10: 1.
9. the preparation method of claim 1, wherein the permanent magnetic ferrite pre-sintering coarse powder contains lanthanum and cobalt.
10. The permanent magnetic ferrite powder for dry press molding produced by the production method according to any one of claims 1 to 9.
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