US4591383A — Apparatus and method of filtering molten metal us…

Claim 1

Independent Claim 144 words

An apparatus comprising: a molten metal filter of honeycomb structure with a multiplicity of thin walls defining a multiplicity of open ended, substantially uniform, hollow cells extending between a pair of honeycombed outer surfaces of the filter, said thin walls being formed by a sintered aggregation of alumina grains, essentially all of said grains having a crystalline form with sharp crystalline corners and wide boundaries between the grains characteristic of alumina having undergone exaggerated grain growth, the aggregation further being at least 98% or more by weight Al 2 O 3 and free of alumina grain growth inhibitors in amounts effective to having inhibited alumina grain growth; means for conveying molten metal to be filtered to one of said honeycombed surfaces of the filter; and means for conveying the molten metal from the remaining honeycombed surface of the filter after passage through said cells.

Claim 2

Independent Claim 144 words

An apparatus comprising: a molten metal filter of honeycomb structure with a multiplicity of thin walls defining a multiplicity of open ended, substantially uniform, hollow cells extending between a pair of honeycombed outer surfaces of the filter, said thin walls being formed by a sintered aggregation of alumina grains, essentially all of said grains having a crystalline form with sharp crystalline corners and wide boundaries between the grains characteristic of alumina having undergone exaggerated grain growth, the aggregation further being at least 98% or more by weight Al 2 O 3 and free of alumina grain growth inhibitors in amounts effective to having inhibited alumina grain growth; means for conveying molten metal to be filtered to one of said honeycombed surfaces of the filter; and means for conveying the molten metal from the remaining honeycombed surface of the filter after passage through said cells.

Claim 3

Dependent Claim 21 words

The apparatus of claim 1 wherein essentially all of said grains have average sizes of between about 10 and 200 microns.

Claim 4

Dependent Claim 19 words

The apparatus of claim 2 wherein said aggregation has a total porosity of about 10% or more bulk volume.

Claim 5

Dependent Claim 38 words

The apparatus of claim 3 wherein the aggregation is at least about 99.5% by weight Al 2 O 3 and a major proportion by weight of said grains have average sizes of between about 50 and 150 microns.

Claim 6

Dependent Claim 19 words

The apparatus of claim 4 wherein the total porosity of the aggregation is also no greater than about 14%.

Claim 7

Dependent Claim 18 words

The apparatus of claim 5 wherein said aggregation has an open porosity of no greater than about 5%.

Claim 8

Independent Claim 165 words

A method of filtering molten metal comprising the steps of: providing a molten metal filter of honeycomb structure formed by a multiplicity of thin walls defining a multiplicity of open ended, substantially uniform, hollow cells extending between a pair of honeycombed outer surfaces of the filter, said thin walls being formed by a sintered aggregation of alumina grains, essentially all of said grains having a crystalline form with sharp crystalline corners and wide boundaries between the grains characteristic of alumina having undergone exaggerated grain growth, the aggregation further being at least 98% or more by weight Al 2 O 3 and free of grain growth inhibitors in amounts effective to have inhibited alumina grain growth; conveying molten metal to be filtered to one of said honeycombed surfaces of the filter; passing the molten metal through said one honeycombed surface, the hollow cells of the structure and said remaining honeycombed surface; and conveying the filtered molten metal away from said remaining honeycombed surface of the filter.

Claim 9

Independent Claim 165 words

A method of filtering molten metal comprising the steps of: providing a molten metal filter of honeycomb structure formed by a multiplicity of thin walls defining a multiplicity of open ended, substantially uniform, hollow cells extending between a pair of honeycombed outer surfaces of the filter, said thin walls being formed by a sintered aggregation of alumina grains, essentially all of said grains having a crystalline form with sharp crystalline corners and wide boundaries between the grains characteristic of alumina having undergone exaggerated grain growth, the aggregation further being at least 98% or more by weight Al 2 O 3 and free of grain growth inhibitors in amounts effective to have inhibited alumina grain growth; conveying molten metal to be filtered to one of said honeycombed surfaces of the filter; passing the molten metal through said one honeycombed surface, the hollow cells of the structure and said remaining honeycombed surface; and conveying the filtered molten metal away from said remaining honeycombed surface of the filter.

Claim 10

Dependent Claim 45 words

The method of claim 7 wherein said aggregation is formed with a content of at least about 99.5% by weight Al 2 O 3 and a major proportion by weight of the sintered alumina grains have average sizes of between about 50 and 150 microns.

Claim 11

Dependent Claim 30 words

The method of claim 8 wherein said step of providing further comprises the step of forming the sintered aggregation with a total porosity of about 10% or more bulk volume.

Claim 12

Dependent Claim 115 words

The method of claim 7 wherein said step of providing further comprises the steps of: forming a green honeycomb monolith of interconnected continuous thin walls from a sinterable alumina mixture, at least essentially all of the alumina of the mixture being reactive alumina grains having average sizes of about 5 microns or less and the mixture further being free of alumina grain growth inhibitors in amounts effective to inhibit growth of the alumina grains during sintering; and sintering the green monolith structure at a temperature sufficiently high and for a period sufficiently long to cause essentially all remaining alumina grains to undergo exaggerated grain growth to average sizes of between about 10 and 200 microns.

Claim 13

Dependent Claim 30 words

The method of claim 10 wherein at least said reactive alumina added to the mixture has a purity of at least about 99.5% by weight Al 2 O 3 .

Claim 14

Dependent Claim 25 words

The method of claim 7 wherein said forming step further comprises the step of: extruding said mixture in the form of said green honeycombed structure.

Claim 15

Dependent Claim 83 words

The method of claim 7 wherein said step of providing further comprises the step of: including in the mixture a burn out material substantially uniformly distributed throughout each of the thin walls of the monolith in an amount sufficient to increase the resistance of the monolith after sintering to damage from thermal shock; and said sintering step further comprises heating the monolith in an oxygen atmosphere for a period sufficiently long to also combust at least essentially all of the burn out composition.

Claim 16

Independent Claim 161 words

A method of filtering molten metal comprising the steps of: providing a molten metal filter of honeycombed structure formed by a sintered aggregation of alumina grains, essentially all of said grains having a crystalline form with sharp crystalline corners and wide boundaries between the grains characteristic of alumina having undergone exaggerated grain growth and having average sizes of between about 10 and 200 microns, the aggregation comprising at least 98% or more by weight Al 2 O 3 and free of alumina grain growth inhibitors in amounts sufficient to have inhibited alumina grain growth, the aggregation of grains forming a multiplicity of thin walls defining a multiplicity of hollow, open-ended cells extending between a pair of honeycombed outer surfaces of the filter; and passing a charge of molten metal through the cells from one of said honeycombed outer surfaces through said cells and the remaining honeycombed outer surface whereby solid impurities in the molten metal charge are deposited on the filter.

Claim 17

Independent Claim 161 words

A method of filtering molten metal comprising the steps of: providing a molten metal filter of honeycombed structure formed by a sintered aggregation of alumina grains, essentially all of said grains having a crystalline form with sharp crystalline corners and wide boundaries between the grains characteristic of alumina having undergone exaggerated grain growth and having average sizes of between about 10 and 200 microns, the aggregation comprising at least 98% or more by weight Al 2 O 3 and free of alumina grain growth inhibitors in amounts sufficient to have inhibited alumina grain growth, the aggregation of grains forming a multiplicity of thin walls defining a multiplicity of hollow, open-ended cells extending between a pair of honeycombed outer surfaces of the filter; and passing a charge of molten metal through the cells from one of said honeycombed outer surfaces through said cells and the remaining honeycombed outer surface whereby solid impurities in the molten metal charge are deposited on the filter.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1989-05-26	1989-11-25	1990-05-27	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1993-05-26	1993-11-25	1994-05-27	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1997-05-26	1997-11-25	1998-05-27	$7700.00	Window Closed / Lapsed

Apparatus and method of filtering molten metal using honeycomb structure of sintered alumina as filter element

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