US4252544A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Alumina abrasive grains and method for manufacturing the same
Assignee: Resonac Holdings Corp
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Filing: 1979-05-09
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Granted: 1981-02-24
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Expires: 1999-05-09
Abstract
Abstract Alumina abrasive grains having a density of more than 3.75 g/cm 3 and a hardness (Knoop) higher than 1,900 Kg/mm 2 are disclosed as useful in manufacturing a grinding wheel with which sharp grinding is carried out under heavy loads. The grains are characterized in that the grain structure thereof is constructed of electrofused or high temperature calcined alumina coarse crystal particles and alumina fine crystal particles which are located between said alumina coarse crystal particles, the latter having particle sizes smaller than that of the former and being processed at a calcination temperature lower than that of the former, wherein said fine crystal particles are sintered integrally with said coarse crystal particles. The method of making the grains is also disclosed.
Inventors
- 👤 Tokiji Takahashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 04:01
CPC Classifications
C; C09; C09K; C09K3/00; C09K3/14; C09K3/1436
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
78 words
Alumina abrasive grains produced by sintering, having a density of more than 3.75 g/cm 3 , a hardness (Knoop) of higher than 1,900 Kg/mm 2 , and a purity of higher than 98 percent wherein the grain structure is constructed of alumina coarse crystal particles of sizes in the range of 3 to 10 μm, and alumina fine crystal particles of sizes smaller than 2 μm, and said fine crystal particles are interposed among said coarse crystal particles.
Claim 2
Dependent Claim
78 words
Alumina abrasive grains produced by sintering, having a density of more than 3.75 g/cm 3 , a hardness (Knoop) of higher than 1,900 Kg/mm 2 , and a purity of higher than 98 percent wherein the grain structure is constructed of alumina coarse crystal particles of sizes in the range of 3 to 10 μm, and alumina fine crystal particles of sizes smaller than 2 μm, and said fine crystal particles are interposed among said coarse crystal particles.
Claim 3
Independent Claim
143 words
A method for manufacturing abrasive grains, which comprises; forming alumina coarse powder with a purity of higher than 98% and with a particle size in the range of 3 to 10 μm by electrofusing or calcining at a temperature of higher than 1700° C.; forming alumina fine powder with a purity of higher than 98% and with a particle size of smaller than 1 μm by calcining at a temperature of lower than 1700° C.; kneading said alumina coarse powder and said alumina fine powder in the presence of water or if necessary, primary binder; extruding the kneaded material by means of a mechanical extruder; drying the extruded material; cutting the extruded material to a predetermined length; and sintering the dried and cut pieces of extruded material at a temperature higher than that of calcining the fine powder and lower than 1700° C.
Claim 4
Independent Claim
143 words
A method for manufacturing abrasive grains, which comprises; forming alumina coarse powder with a purity of higher than 98% and with a particle size in the range of 3 to 10 μm by electrofusing or calcining at a temperature of higher than 1700° C.; forming alumina fine powder with a purity of higher than 98% and with a particle size of smaller than 1 μm by calcining at a temperature of lower than 1700° C.; kneading said alumina coarse powder and said alumina fine powder in the presence of water or if necessary, primary binder; extruding the kneaded material by means of a mechanical extruder; drying the extruded material; cutting the extruded material to a predetermined length; and sintering the dried and cut pieces of extruded material at a temperature higher than that of calcining the fine powder and lower than 1700° C.
Claim 5
Dependent Claim
19 words
A method as set forth in claim 2, wherein said primary binder to be added during kneading is starch.
Claim 6
Dependent Claim
24 words
A method as set forth in claim 2, wherein extruding is performed under reduced pressure with the use of a vacuum aided type extruder.
Claim 7
Dependent Claim
37 words
A method as set forth in claim 4, wherein the kneaded material is extruded through a nozzle during the extruding operation, the nozzle having an inner diameter substantially equal to the outer diameter of the abrasive grain.
Claim 8
Dependent Claim
45 words
A method as set forth in claim 4, wherein the extruded material is cut to the predetermined length naturally or with the aid of suitable cutting means, said length being substantially equal to or a little longer than the diameter of the product abrasive grain.
Claim 9
Dependent Claim
22 words
A method as set forth in claim 2, wherein the grannular pieces of the molded material are sintered in a rotary kiln.
Claim 10
Dependent Claim
32 words
A method as set forth in claim 7, wherein the granular pieces of the molded material are sintered in a temperature range of 1,550° to 1,650° C., for 40 to 60 minutes.
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) | 1984-02-24 | 1984-08-25 | 1985-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-24 | 1988-08-25 | 1989-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-24 | 1992-08-25 | 1993-02-24 | $7700.00 | Window Closed / Lapsed |