GB2091592A - Refractory heat-insulating material - Google Patents

Refractory heat-insulating material Download PDF

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Publication number
GB2091592A
GB2091592A GB8201462A GB8201462A GB2091592A GB 2091592 A GB2091592 A GB 2091592A GB 8201462 A GB8201462 A GB 8201462A GB 8201462 A GB8201462 A GB 8201462A GB 2091592 A GB2091592 A GB 2091592A
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United Kingdom
Prior art keywords
refractory
coated
low density
particles
insulating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB8201462A
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Foseco International Ltd
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Foseco International Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Foseco International Ltd filed Critical Foseco International Ltd
Priority to GB8201462A priority Critical patent/GB2091592A/en
Publication of GB2091592A publication Critical patent/GB2091592A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B22D7/06—Ingot moulds or their manufacture
    • B22D7/10—Hot tops therefor
    • B22D7/102—Hot tops therefor from refractorial material only
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/10—Coating or impregnating
    • C04B20/1055—Coating or impregnating with inorganic materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B30/00—Compositions for artificial stone, not containing binders

Abstract

A refractory heat-insulating material suitable for use as an anti- piping compound or cover on the surface of molten metal comprises a low density porous particulate material, such as expanded perlite, exfoliated vermiculite, pumice or furnace aggregate, coated with a refractory oxide, such as silica, alumina, chromia or zirconia, formed from a colloidal oxide sol.

Description

SPECIFICATION Refractory heat-insulating materials This invention relates to refractory heatinsulating materials comprising low density porous particulate materials such as perlite, vermiculite, pumice and furnace aggregate, coated with a refractory oxide.
Refractory heat-insulating compositions containing particulate materials are used in particulate form or as shaped products in the form of slabs or sleeves to insulate molten metal in the production of metal castings or ingots.
In order to achieve good thermal insulation properties in the refractory heat-insulating composition it is important that the composition should have as low a density as possible, commensurate with adequate resistance to the molten metal against which the composition is being used.
In the past low densities have been achieved by the incorporation of organic or inorganic fibres or by including low density porous particulate materials such as expanded perlite, exfoliated vermiculite, pumice or furnace aggregate.
Such low density porous materials have relatively low softening and melting points, so that the quantity which can be used particularly when casting high melting point metals such as copper, iron and steel, is limited.
It has now been found that the refractoriness of such low density porous particulate materials may be increased thus increasing their usefulness in compositions for use in the casting of molten metals by coating the particles with a layer of refractory oxide produced from a colloidal oxide sol.
According to the invention there is provided a refractory heat-insulating material comprising a low density porous particulate material coated with a refractory oxide formed form a colloidal oxide sol.
According to the invention there is provided a method of producing a refractory heat-insulating material which comprises forming a fluidised suspension in air of a low density porous particulate material, spraying the surface of the particles of fluidised material with a coating of a colloidal sol of a refractory oxide and heating the coated particles to dry the coating and bond it firmly to the surface of the particles.
The low density porous particulate material preferably has a density of less than 1 g/cm3 and may be for example expanded perlite, exfoliated vermiculate, pumice, or furnace aggregate.
The refractory oxide sol is preferably a hydrosol but the liquid need not be water. Examples of suitable refractory oxides include silica, alumina, chromia and zirconia.
A suitable method for coating the particles is described in Refractories Journal, May/June 1980, page 19.
The coated low density particles of the invention may be used on their own as an antipiping compound or bound together with a binder as an insulating cover on the surface of molten metals such as copper, iron or steel in a riser, mould or ladle etc. They may also be used as a component of an exothermic and/or refractory heat-insulating composition for use in the production of castings or ingots from molten copper, iron or steel, either as an anti-piping compound or loose cover or as a bonded shape such as a slab or sleeve. When used as a component of an exothermic and/or refractory heat-insulating composition the particles may constitute as little as about 1% by weight of the composition or as much as about 95% by weight of the composition.
The following example will serve to illustrate the invention: Quantities of nominally +100 mesh B.S.S.
perlite having an untamped bulk density of 0.10 g/cm3 were coated with alumina using a boehmite (alumina hydrate) sol using the procedure described in Refractories Journal, May/June 1980, page 1 9. One sample had a "thin" coating corresponding to an increase in the untamped bulk density of the perlite of 0.03 g/cm3 and another a "thick" coating corresponding to an increase in the untamped bulk density of the perlite of 0.07 g/cm3. Calculations based on the chemical analyses of uncoated and coated perlite samples indicated an alumina pick up of 11.5% by weight in the case of the "thin" coated sample and 34.2% by weight in the case of the "thick" coated sample.
The refractoriness of the samples was compared by placing them in refractory boats and firing them for 30 minutes at 1 3000C. The uncoated perlite shrank considerably and melted into a hard glassy mass whereas although both coated perlite samples showed some shrinkage they remained granular in nature indicating that the alumina coating had acted as a protective shield preventing individual perlite particles from coalescing.
1. A refractory heat-insulating material comprising a low density porous particulate material coated with a refractory oxide formed from a colloidal oxide sol.
2. A refractory heat-insulating material according to claim 1 wherein the porous particulate material is expanded perlite, exfoliated vermiculite, pumice or furnace aggregate.
3. A refractory heat-insulating material according to claim 1 wherein the refractory oxide is silica, alumina, chromia or zirconia.
4. A bonded composition comprising a low density porous particulate material coated with a refractory oxide formed from a colloidal oxide sol and a binder.
5. An exothermic and/or heat-insulating composition comprising a low density porous particulate material coated with a refractory oxide formed from a colloidal oxide sol and an exothermic and/or heat-insulating component.
6. A composition according to claim 5
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Refractory heat-insulating materials This invention relates to refractory heatinsulating materials comprising low density porous particulate materials such as perlite, vermiculite, pumice and furnace aggregate, coated with a refractory oxide. Refractory heat-insulating compositions containing particulate materials are used in particulate form or as shaped products in the form of slabs or sleeves to insulate molten metal in the production of metal castings or ingots. In order to achieve good thermal insulation properties in the refractory heat-insulating composition it is important that the composition should have as low a density as possible, commensurate with adequate resistance to the molten metal against which the composition is being used. In the past low densities have been achieved by the incorporation of organic or inorganic fibres or by including low density porous particulate materials such as expanded perlite, exfoliated vermiculite, pumice or furnace aggregate. Such low density porous materials have relatively low softening and melting points, so that the quantity which can be used particularly when casting high melting point metals such as copper, iron and steel, is limited. It has now been found that the refractoriness of such low density porous particulate materials may be increased thus increasing their usefulness in compositions for use in the casting of molten metals by coating the particles with a layer of refractory oxide produced from a colloidal oxide sol. According to the invention there is provided a refractory heat-insulating material comprising a low density porous particulate material coated with a refractory oxide formed form a colloidal oxide sol. According to the invention there is provided a method of producing a refractory heat-insulating material which comprises forming a fluidised suspension in air of a low density porous particulate material, spraying the surface of the particles of fluidised material with a coating of a colloidal sol of a refractory oxide and heating the coated particles to dry the coating and bond it firmly to the surface of the particles. The low density porous particulate material preferably has a density of less than 1 g/cm3 and may be for example expanded perlite, exfoliated vermiculate, pumice, or furnace aggregate. The refractory oxide sol is preferably a hydrosol but the liquid need not be water. Examples of suitable refractory oxides include silica, alumina, chromia and zirconia. A suitable method for coating the particles is described in Refractories Journal, May/June 1980, page 19. The coated low density particles of the invention may be used on their own as an antipiping compound or bound together with a binder as an insulating cover on the surface of molten metals such as copper, iron or steel in a riser, mould or ladle etc. They may also be used as a component of an exothermic and/or refractory heat-insulating composition for use in the production of castings or ingots from molten copper, iron or steel, either as an anti-piping compound or loose cover or as a bonded shape such as a slab or sleeve. When used as a component of an exothermic and/or refractory heat-insulating composition the particles may constitute as little as about 1% by weight of the composition or as much as about 95% by weight of the composition. The following example will serve to illustrate the invention: Quantities of nominally +100 mesh B.S.S. perlite having an untamped bulk density of 0.10 g/cm3 were coated with alumina using a boehmite (alumina hydrate) sol using the procedure described in Refractories Journal, May/June 1980, page 1 9. One sample had a "thin" coating corresponding to an increase in the untamped bulk density of the perlite of 0.03 g/cm3 and another a "thick" coating corresponding to an increase in the untamped bulk density of the perlite of 0.07 g/cm3. Calculations based on the chemical analyses of uncoated and coated perlite samples indicated an alumina pick up of 11.5% by weight in the case of the "thin" coated sample and 34.2% by weight in the case of the "thick" coated sample. The refractoriness of the samples was compared by placing them in refractory boats and firing them for 30 minutes at 1 3000C. The uncoated perlite shrank considerably and melted into a hard glassy mass whereas although both coated perlite samples showed some shrinkage they remained granular in nature indicating that the alumina coating had acted as a protective shield preventing individual perlite particles from coalescing. CLAIMS
1. A refractory heat-insulating material comprising a low density porous particulate material coated with a refractory oxide formed from a colloidal oxide sol.
2. A refractory heat-insulating material according to claim 1 wherein the porous particulate material is expanded perlite, exfoliated vermiculite, pumice or furnace aggregate.
3. A refractory heat-insulating material according to claim 1 wherein the refractory oxide is silica, alumina, chromia or zirconia.
4. A bonded composition comprising a low density porous particulate material coated with a refractory oxide formed from a colloidal oxide sol and a binder.
5. An exothermic and/or heat-insulating composition comprising a low density porous particulate material coated with a refractory oxide formed from a colloidal oxide sol and an exothermic and/or heat-insulating component.
6. A composition according to claim 5 containing 195% by weight of the coated material.
7. A method of producing a refractory heatinsulating material according to claim 1 which comprises forming a fluidised suspension in air of a low density porous particulate material, spraying the surface of the particles of fluidised material with a coating of a colloidal sol of a refractory oxide and heating the coated particles to dry the coating and bond it firmly to the surface of the particles.
GB8201462A 1981-01-27 1982-01-19 Refractory heat-insulating material Withdrawn GB2091592A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8201462A GB2091592A (en) 1981-01-27 1982-01-19 Refractory heat-insulating material

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8102432 1981-01-27
GB8201462A GB2091592A (en) 1981-01-27 1982-01-19 Refractory heat-insulating material

Publications (1)

Publication Number Publication Date
GB2091592A true GB2091592A (en) 1982-08-04

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Family Applications (1)

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GB8201462A Withdrawn GB2091592A (en) 1981-01-27 1982-01-19 Refractory heat-insulating material

Country Status (1)

Country Link
GB (1) GB2091592A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0147814A2 (en) * 1983-12-21 1985-07-10 Aloys Dr. Wüstefeld Expanded perlite
GB2259873A (en) * 1991-09-28 1993-03-31 Tioxide Group Services Ltd Coated particulate igneous material
GB2260281A (en) * 1991-10-12 1993-04-14 Willich F Berg Bautechnik Building material and method of producing the same
EP0640573A1 (en) * 1993-03-10 1995-03-01 Krosaki Corporation Heat-insulating refractory material
WO1996011171A1 (en) * 1994-10-10 1996-04-18 Deutsche Perlite Gmbh Granular bulk material, process for its production and its use

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0147814A2 (en) * 1983-12-21 1985-07-10 Aloys Dr. Wüstefeld Expanded perlite
EP0147814A3 (en) * 1983-12-21 1987-01-21 Aloys Dr. Wüstefeld Expanded perlite
GB2259873A (en) * 1991-09-28 1993-03-31 Tioxide Group Services Ltd Coated particulate igneous material
GB2259873B (en) * 1991-09-28 1995-07-05 Tioxide Group Services Ltd Coated material,its manufacture and use
GB2260281A (en) * 1991-10-12 1993-04-14 Willich F Berg Bautechnik Building material and method of producing the same
GB2260281B (en) * 1991-10-12 1995-11-01 Willich F Berg Bautechnik Building material and method of producing the same
EP0640573A1 (en) * 1993-03-10 1995-03-01 Krosaki Corporation Heat-insulating refractory material
EP0640573A4 (en) * 1993-03-10 1996-02-07 Krosaki Corp Heat-insulating refractory material.
WO1996011171A1 (en) * 1994-10-10 1996-04-18 Deutsche Perlite Gmbh Granular bulk material, process for its production and its use

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)