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US3723587A
Expired / Lapsed
US
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Elimination of the grinding of calcined ferrite in the production of anisotropic magnets
Assignee: Fine Sinter Co Ltd
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Filing: 1971-02-25
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Granted: 1973-03-27
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Expires: 1991-02-25
Abstract
Abstract Anisotropic metal oxide magnets are produced by mixing at least one of Alpha -FeOOH having rectangular plate or needle crystal form, Alpha -Fe2O3 obtained by thermally decomposing the above described Alpha -FeOOH, Fe3O4 obtained by reducing the above described Alpha -Fe2O3 and gamma -Fe2O3 obtained by reoxidizing the above described Fe3O4 with at least one of barium compounds, strontium compounds and lead compounds so as to adjust the product composition to be approximately MO.6Fe2O3, wherein M is at least one metal of Ba, Sr and Pb, charging the resulting mixture in a press mold and subjecting to a primary compression molding under a pressure of 0.05 to 6 ton/cm2, primary sintering the compressed product at a temperature of 300* to 1,150*C, putting the sintered product in a press mold and subjecting to a secondary compression molding in the same direction as in the primary compression molding under a pressure of 0.3 to 10 ton/cm2 and secondarily sintering the compressed product at a temperature of 1,050*C to 1,400*C. Optionally, the barium, strontium, or lead compounds can be added either after the first cold pressing step or after the partial sintering step instead of prior to the first cold pressing step.
Inventors
- 👤 K Iwase
- 👤 M Kiyama
- 👤 I Naito
- 👤 T Takada
- 👤 Y Bando
- 👤 M Kazihara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:34
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/26; C04B35/2683; Y; Y10; Y10S; Y10S264/00; Y10S264/58
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
71 words
The process as claimed in claim 1, and adding to said mixture prior compression 0.05 to 4.5 percent by weight of at least one compound selected from the group consisting of Ca0, Si02, Al2O3, Na2O, As2O3, As2O5, K2O, BeO, B2O3, CdO, CeO2, Cs2O, Cr2O3, CoO, CuO, PbCrO4, Li2O, MgO, Mn3O4, MoO3, NiO, Nb2O5, WO3, V2O5, ZnO, ZrO2, TiO2, Sb2O5, BaSO4, SrSO4, PbF2, MgF2, Al2I3.6H2O, BaI2.2H2O and CaI2.6H2O as a magnetic-property-improving additive.
Claim 2
Dependent Claim
26 words
The process as claimed in claim 2, wherein when M is barium, said compound has a cation selected from the group consisting of strontium and lead.
Claim 3
Dependent Claim
26 words
The process as claimed in claim 2, wherein when M is strontium, said compound has a cation selected from the group consisting of barium and lead.
Claim 4
Dependent Claim
26 words
The process as claimed in claim 2, wherein when M is lead, said compound has a cation selected from the group consisting of barium and strontium.
Claim 5
Dependent Claim
225 words
A process of producing anisotropic metal oxide magnets which consists essentially of subjecting particles having rectangular plate or needle crystal form, selected from Alpha FeOOH having (100) crystal plane, Alpha -Fe2O3 having (0001) crystal plane and obtained by thermally decomposing the above-described Alpha -Fe00H, Fe3O4 having (111) crystal plane and obtained by reducing the above-described Alpha -Fe2O3 and gamma -Fe2O3 having (111) crystal plane and obtained by reoxidizing the above-described Fe3O4, the major axis of said crystal being 0.1 to 5 Mu , to cold compression molding under a pressure of about 0.5 to 3 ton/cm2 in a press mold, releasing said pressure, impregnating the compressed product with an aqueous solution of at least one water-soluble compound selected from the group consisting of barium acetate, strontium acetate and lead acetate so as to adjust the product composition to be approximately MO.6Fe2O3, wherein M is at least one metal selected from the group consisting o4 Ba, Sr and Pb, drying the impregnated product, partially sintering the thus-treated product at a temperature of 300* to 1,150*C., putting the sintered product in a press mold and subjecting the sintered product to further cold compression molding under a pressure at least as high as the first-mentioned pressure up to 10 ton/cm2, releasing the last-named pressure, and fully sintering the further compressed product at a temperature of 1,050* to 1,400*C.
Claim 6
Dependent Claim
68 words
A process as claimed in claim 6, wherein said product as first compressed is impregnated with an aqueous solution of at least one water-soluble compound selected from the group consisting of barium acetate, strontium acetate and lead acetate together with an aqueous solution of 0.05 to 4.5 percent by weight of at least one water-soluble magnetic-property-improving additive selected from the group consisting of Al2I3.6H2O, BaI2.2H2O and CaI2. 6H2O.
Claim 7
Dependent Claim
44 words
A process as claimed in claim 6, wherein an aqueous solution of 0.05 to 4.5 percent by weight of at least one water-soluble magnetic-property-improving additive selected from the group consisting of Al2I3.6H2O, BaI2.2H2 O and CaI2.6H2O is impregnated on the product as first sintered.
Claim 8
Dependent Claim
199 words
A process of producing anisotropic mEtal oxide magnets which consists essentially of subjecting particles having rectangular plate or needle crystal form, selected from Alpha -FeOOH having (100) crystal plane and Fe3O4 having (111) crystal plane, the major axis of said crystal being 0.1 to 5 Mu , to cold compressing molding under a pressure about 0.5 to 3 ton/cm2 in a press mold, releasing said pressure, partially sintering the compressed product at a temperature of 300*C. to 1,150*C., impregnating the sintered product with an aqueous solution of at least one water-soluble compound selected from the group consisting of barium acetate, strontium acetate and lead acetate so as to adjust the product composition to be approximately MO.6Fe2O3, wherein M is at least one metal selected from the group consisting of Ba, Sr and Pb, drying the impregnated product, putting the thus-treated product in a press mold and subjecting the impregnated product to further cold compression molding in the same direction as in the first compression molding under a pressure at least as high as the first-mentioned pressure up to 10 ton/cm2, releasing the last-named pressure, and fully sintering the further compressed product at a temperature of 1, 050* to 1,400*C.
Claim 9
Dependent Claim
68 words
A process as claimed in claim 9, wherein the product as first sintered is impregnated with an aqueous solution of at least one water-soluble compound selected from the group consisting of barium acetate, strontium acetate and lead acetate together with an aqueous solution of 0.05 to 4.5 percent by weight of at least one water-soluble magnetic-property-improving additive selected from the group consisting of Al2I3.6H2O, BaI2.2H2 O and CaI2.6H2O.
Claim 10
Dependent Claim
298 words
A process of producing anisotropic metal oxide magnets which consists essentially of mixing particles having rectangular plate or needle crystal form, selected from Alpha -FeOOH having (100) crystal plane, Alpha -Fe2O3 having (0001) crystal plane and obtained by thermally decomposing the above-described Alpha -FeOOH, Fe3O4 having (111) crystal plane and obtained by reducing the above-described Alpha -Fe2O3 and gamma -Fe2O3 having (111) crystal plane and obtained by reoxidizing the above-described Fe3O4, the major axis of said crystal being 0.1-5 Mu , with at least one compound selected from the group consisting of carbonates, oxides, hydroxides, acetates and sulfates of barium, strontium and lead so as to adjust the product composition to be approximately MO.6Fe2O3, wherein M is at least one metal selected from the group consisting of Ba, Sr and Pb, charging the resulting mixture in a press mold and subjecting the mixture to cold compression molding under a pressure of about 0.5 to 3 ton/cm2, releasing said pressure, partially sintering the compressed product at a temperature of 300* to 800*C., putting the sintered product in a press mold and subjecting the sintered product to further cold compression molding in the same direction as in the first compression molding under a pressure at least as high as the first-mentioned pressure up to 6 ton/cm.2 releasing the last-named pressure, further partially sintering the compressed product at a temperature of 800* to 1,150* C., putting the further sintered product in a press mold and subjecting the further sintered product to a still further cold compression molding in the same direction as in the first compressing molding under a pressure at least as high as the last-mentioned pressure up to 10 ton/cm.2, releasing the last-named pressure and fully sintering the still further compressed product at a tempeRature of 1,050* to 1,400*C.
Claim 11
Dependent Claim
257 words
A process of producing anisotropic metal oxide magnets which consists essentially of mixing particles having rectangular plate or needle crystal form, selected from Alpha -FeOOH having (100) crystal plane, Alpha -Fe2O3 having (0001) crystal plane and obtained by thermally decomposing the above-described Alpha -FeOOH, Fe3O4 having (111) crystal plane and obtained by reducing the above-described Alpha -Fe2O3 and gamma -Fe2O3 having (111) crystal plane and obtained by reoxidizing the above-described Fe3O4, the major axis of said crystal being 0.1-5 Mu , with at least one compound selected from the group consisting of carbonates, oxides, hydroxides, acetates and sulfates of barium, strontium and lead so as to adjust the product composition to be approximately MO.6 Fe2O3, wherein M is at least one metal selected from the group consisting of Ba, Sr and Pb, adding water to the resulting mixture and kneading thoroughly the resulting mass, charging the mass in a press mold provided with a filter and subjecting the mass to cold compression molding under a pressure of about 0.5 to 3 ton/cm2 to separate and discharge water, releasing said pressure, drying the compressed product, partially sintering the dried compressed product at temperature of 300* to 1,150*C., putting the sintered product in a press mold and subjecting the sintered product to further cold compression molding in the same direction as the first compression molding under a pressure at least as high as the first-mentioned pressure up to 10 ton/cm2, releasing the last-named pressure, and fully sintering the further compressed product at a temperature of 1, 050* to 1,400*C.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |