US3855374A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making magnetically-anisotropic permanent magnets
Assignee: Motors Liquidation Co
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Filing: 1972-12-22
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Granted: 1974-12-17
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Expires: 1992-12-22
Abstract
Abstract A method of making a permanent magnet of the hard ferrite type having a formula (SrO.6 Fe2O3) SrO.6Fe2O3 is disclosed. The process comprises the critical step of adding a compound selected from the group consisting of boric acid and boric oxide to magnetite and a source of SrO during the mixing (a) and milling step prior to calcining of the mixture. Superior magnets are produced over those achieved by the process where the boric acid or boric oxide is introduced after calcining of magnetite and a source of SrO.
Inventors
- 👤 V Brailowsky
- 👤 E Alson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 14:52
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/26; C04B35/2683; Y; Y10; Y10S; Y10S264/00; Y10S264/58
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
110 words
A METHOD OF MAKING A PERMANENT MAGNET OF THE HARD FERRITE TYPE HAVING A HEXAGONAL CRYSTALLINE LATTICE WITH A MAGNETOPLUMBITE STRUCTURE AND A FORMULA SRO. 6F2O3, COMPRISING THE STEPS OF MIXING AND MILLING MAGNETITE WITH A SOURCE OF SRO AND ABOUT 0.3 TO 1.5 PERCENT, BY WEIGHT, OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF BORIC ACID AND BORIC OXIDE TO FORM A HOMOGENEOUS MIXTURE THEREOF, CALCINING SAID MIXTURE, COMMINUTING SAID CALCINED MIXTURE TO FORM PARTICLES THEREOF HAVING AN AVERAGE SIZE OF ABOUT 1 TO 2 MICRONS, ORIENTING AND FORMING SAID PARTICLES INTO A BODY AND SINTERING SAID BODY AT A TEMPERATURE IN THE RANGE OF 2000* TO 2150*F.
Claim 2
Independent Claim
110 words
A METHOD OF MAKING A PERMANENT MAGNET OF THE HARD FERRITE TYPE HAVING A HEXAGONAL CRYSTALLINE LATTICE WITH A MAGNETOPLUMBITE STRUCTURE AND A FORMULA SRO. 6F2O3, COMPRISING THE STEPS OF MIXING AND MILLING MAGNETITE WITH A SOURCE OF SRO AND ABOUT 0.3 TO 1.5 PERCENT, BY WEIGHT, OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF BORIC ACID AND BORIC OXIDE TO FORM A HOMOGENEOUS MIXTURE THEREOF, CALCINING SAID MIXTURE, COMMINUTING SAID CALCINED MIXTURE TO FORM PARTICLES THEREOF HAVING AN AVERAGE SIZE OF ABOUT 1 TO 2 MICRONS, ORIENTING AND FORMING SAID PARTICLES INTO A BODY AND SINTERING SAID BODY AT A TEMPERATURE IN THE RANGE OF 2000* TO 2150*F.
Claim 3
Dependent Claim
14 words
The method of claim 1 wherein said mixture is calcined at about 2100* F.
Claim 4
Independent Claim
123 words
A method of making a permanent magnet of the hard ferrite type having a hexagonal crystalline lattice with a magnetoplumbite structure and a formula SrO. 6Fe2O3, comprising the steps of mixing and milling magnetite with a source of SrO and about 0.3 to 1.5 percent, by weight, of a compound selected from the group consisting of boric acid and boric oxide to form a homogeneous mixture thereof, calcining said mixture, comminuting said calcined mixture to form particles thereof having an average size of about 1 to 2 microns, compacting said particles while under the influence of a directional magnetic field into a body anisotropic in a principal direction, and sintering said body at a temperature in the range of 2000* to 2150* F.
Claim 5
Independent Claim
123 words
A method of making a permanent magnet of the hard ferrite type having a hexagonal crystalline lattice with a magnetoplumbite structure and a formula SrO. 6Fe2O3, comprising the steps of mixing and milling magnetite with a source of SrO and about 0.3 to 1.5 percent, by weight, of a compound selected from the group consisting of boric acid and boric oxide to form a homogeneous mixture thereof, calcining said mixture, comminuting said calcined mixture to form particles thereof having an average size of about 1 to 2 microns, compacting said particles while under the influence of a directional magnetic field into a body anisotropic in a principal direction, and sintering said body at a temperature in the range of 2000* to 2150* F.
Claim 6
Independent Claim
123 words
A method of making a permanent magnet of the hard ferrite type having a hexagonal crystalline lattice with a magnetoplumbite structure and a formula SrO. 6Fe2O3, comprising the steps of mixing and milling magnetite having an average grain size on the order of about 50 microns with a source of SrO and about 0.7 percent, by weight, boric acid to form a homogeneous mixture thereof, calcining said mixturE of about 2100* F, comminuting said calcined mixture to form particles thereof having an average size of about 1 to 2 microns, compacting said particles while under the influence of a directional magnetic field to form a body anisotropic in a principal direction, and sintering said body in the range of 2000* to 2150* F.
Claim 7
Independent Claim
123 words
A method of making a permanent magnet of the hard ferrite type having a hexagonal crystalline lattice with a magnetoplumbite structure and a formula SrO. 6Fe2O3, comprising the steps of mixing and milling magnetite having an average grain size on the order of about 50 microns with a source of SrO and about 0.7 percent, by weight, boric acid to form a homogeneous mixture thereof, calcining said mixturE of about 2100* F, comminuting said calcined mixture to form particles thereof having an average size of about 1 to 2 microns, compacting said particles while under the influence of a directional magnetic field to form a body anisotropic in a principal direction, and sintering said body in the range of 2000* to 2150* F.
Claim 8
Dependent Claim
14 words
The method of claim 4 wherein said body is sintered at about 2100* F.
References Cited (Backward Citations)
US2762777A
Cited
GB754626A
Cited
US2980617A
Cited
US3113927A
Cited
DE1471405A1
Cited
US3424685A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-16 | 1978-06-17 | 1978-12-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-16 | 1982-06-17 | 1982-12-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-16 | 1986-06-17 | 1986-12-17 | $7700.00 | Window Closed / Lapsed |