WO1988000931A1 - High density chromic oxide refractory block - Google Patents
High density chromic oxide refractory block Download PDFInfo
- Publication number
- WO1988000931A1 WO1988000931A1 PCT/US1987/001739 US8701739W WO8800931A1 WO 1988000931 A1 WO1988000931 A1 WO 1988000931A1 US 8701739 W US8701739 W US 8701739W WO 8800931 A1 WO8800931 A1 WO 8800931A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- chromic oxide
- block
- titania
- colloidal silica
- firing
- Prior art date
Links
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 title claims abstract description 31
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 42
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 42
- 238000010304 firing Methods 0.000 claims abstract description 19
- 239000008119 colloidal silica Substances 0.000 claims abstract description 16
- 230000001590 oxidative effect Effects 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 11
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 10
- 239000000377 silicon dioxide Substances 0.000 claims description 10
- 239000011819 refractory material Substances 0.000 claims description 6
- 239000000395 magnesium oxide Substances 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 4
- 239000006060 molten glass Substances 0.000 abstract description 9
- 230000007797 corrosion Effects 0.000 abstract description 6
- 238000005260 corrosion Methods 0.000 abstract description 6
- 239000011521 glass Substances 0.000 description 8
- 239000002002 slurry Substances 0.000 description 6
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000000280 densification Methods 0.000 description 3
- 229910021485 fumed silica Inorganic materials 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000000462 isostatic pressing Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- 239000004094 surface-active agent Substances 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- 229910052845 zircon Inorganic materials 0.000 description 2
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 2
- 101100008044 Caenorhabditis elegans cut-1 gene Proteins 0.000 description 1
- IMROMDMJAWUWLK-UHFFFAOYSA-N Ethenol Chemical compound OC=C IMROMDMJAWUWLK-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 239000013530 defoamer Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000003995 emulsifying agent Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 239000011505 plaster Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000867 polyelectrolyte Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
Classifications
-
- 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
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/12—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on chromium oxide
Definitions
- This Invention relates to dense refractory blocks having a high chromic oxide content which are used as linings for glass melting furnaces.
- Large blocks of this kind typically measuring as large as 6 x 12 x 36 inches, tend to crack while being fired during manufacture. The cracking appears to be caused by stresses stemming from non-uniform densification of the refractory during the firing.
- Such blocks are formed by methods generally known by those skilled in making various types of ceramic articles.
- Various types of procedures are known for preparing, mixing, pressing, and drying the raw materials to form an unfired body and then firing the body in a kiln at high temperatures, generally above 2600°F (1427°C) but below the melting point of the mixture, to develop a ceramic bonded article.
- the advantages of the method of this invention are not applicable to fusion casting of refractory shapes.
- Manigault teaches that a refractory material comprising from 85 to 58% chromic oxide, from 0.5 to 5% titanium dioxide, and from 1 to 10% zircon possesses very low porosity, high resistance to corrosion by molten glass, and is resistant to thermal cracking during firing.
- titania 1 to about 4% by weight of titania, from about 1 to about 3% by weight of a silica having a surface area of about 90m 2 /g or greater, from 0% to about 8% alumina, from 0% to about 5% ferric oxide, and from 0% to about 5% magnesia, pressing the blended solids into the desired shape, and firing the pressed shape at a temperature of from about 2600°F to about 3200°F (1427-1760°C) in a kiln in which the atmosphere may contain from about 1.5% excess combustibles to about 1.5% excess oxygen.
- a preferred mixture contains about 2% each of titania and the colloid-sized silica.
- the chromic oxide preferably has an average particle size greater than 1 micron, more preferably from about 2 to about 10 microns.
- a technical grade having a purity of about 98.5% Cr 2 O 3 is suitable.
- a pigment grade of titania is. preferred;. either anatase or rutile is satisfactory.
- a finely divided titania such as that sold under the trademark Titanox 1070 by NL Industries, Inc. exemplifies the material used in this Invention.
- the silica may be in the form of a sol such as that sold by DuPont under its LUDOX trademark, or it may be a dry powder s.uch as CAB-O-SIL fumed silica sold by Cabot Corporation.
- the average particle diameter of the colloidal silica may be from about 7 to about 24 nm (0.007 to 0.024 micron).
- the alumina, ferric oxide, and magnesia may originate from a low silica chromite, as may some of the chromic oxide.
- the chromite which is a chrome iron ore, may constitute up to about 28% of the dry weight of the blended mixture.
- a representative sample of the ore contained 35.1% Cr 2 O 3 , 28.8% A1 2 O 3 , 15.4% Fe 2 O 3 ' 18.8% MgO, 1,8% SiO 2 and 0.2% CaO.
- the silica of the ore does not function like the colloidal silica described above; the average particle size of the ore is preferably from about 3.5 to about 5 microns but it may be from 1 to about 10 microns.
- Zircon, and other materials which generate silica in situ during the high temperature firing of the block may be a source of the colloidal silica.
- the preferred composition is from about 93% to about 98% chromic oxide, from about 1% to about 4% titania, and from about 1% to about 3% by weight of the colloidal silica.
- a particularly preferred block made from technical grade chromic oxide contains about
- a large, dense refractory block is defined for the purposes of this invention as one having a volume of at least about 0.5 cubic foot (0.014 m 3 ) and a density of from about 260 to about 320 pounds per cubic foot.
- a refractory block made by the method of this invention may be of any useful size or shape but the advantages of this invention are particularly beneficial in the formation of blocks as large as about 2 cubic feet (0.05 m 3 ) such as., for example, one being 6 inches thick, 12 inches wide, and from 24 to 36 inches long. Blocks having right angled cut outs or an inside corner of about a one inch radius have been produced free of cracks, by the method of this invention.
- a particularly advantageous feature of the blocks of this invention is the fact that their porosity may be as.
- the green block of this invention may be made in several ways. Slurrying of the chromic oxide, titania, and colloidal silica with water, an organic binder and an emulsifier, followed by spray drying and isostatic pressing is one way. Such a slurry may be slip cast in a plaster mold, also. Dampening of the oxide mixture with about 5 to 10% by weight of an aqueous binder solution and pressing at from 8000 to 12000 psi on a hydraulic press Is another way. Firing of the green block may be carried out In either an oxidizing or a reducing atmosphere. The preferred temperature for firing is from about 2700 to about 3200°F; firing in. a reducing atmosphere at from about 2700 to about 2950°F is especially preferred.
- the kiln atmosphere was maintained in the range of 0.5 to 1.5% excess combustibles after the temperature reached 1600°F. After cooling the block to ambient temperature again in the kiln, it was inspected and measured. Apparent porosity and bulk density of the fired refractory was determined from measurements of a 3" x 3" x 9" bar of the refractory material which sat atop the block during firing.
- the green density of the block was 203 lbs/cu ft (3250 kg/m 3 ) and the fired density was about 293 1bs/cu ft (4688 kg/m 3 ).
- the glass corrosion resistance of the block of Example 1 was tested by suspending lengthwise four rectangular test bars cut from the block in each of three different baths of molten glass contained in platinum crucibles. The surface of the molten glass in each case was maintained at about 1.23 inches. (31.8mm) above the lower end of the test bar. The first set of four bars was held in the molten glass at 2650°F for 348 hours. The second set was held in the bath for 692.5 hours. The third set was held in the molten glass bath at 2700°F for 648 hours. After removal of the molten glass from the crucibles and cooling of the test bars, the extent of corrosion of the bars was measured at the glass line, i.e.
- the average number of days to cut 1 inch at the glass line was 440. Measurements of the bars below the glass line, when plugged into the above formula and the results averaged, indicated that it would take 515 days of submersion in molten glass to cause a loss of 1 inch of refractory by corrosion under the glass line.
- a refractory block which was fired at the same time in the same kiln as that of Example 1 was prepared by the general procedure of that example except that the chromic oxide had an average particle size of 2.3 microns, only 204 pounds of slurry water were used and the mold was not evacuated before being closed. The block did not crack during firing or cooling even though shrinkage was greater in each dimension.
- a green block having a density of 196 pounds per cubic foot and a bar were made by the general procedure of Example 1 and fired according to the schedule in that example but an atmosphere containing from 1/8 to 1/4.percent excess oxygen was maintained in the kiln after the temperature reached 1600°F.
- the block had no cracks despite shrinkages of 12.04%, 14.35%, and 13.05% in the length, width, and thickness, respectively.
- the bulk density, as measured on the bar was 300 pounds/cu ft (4.8 g/cc) and the apparent porosity was 0.0%.
- the soaking period at 450°F was. also omitted from the firing schedule and the excess combustibles atmosphere was maintained above 1500°F.
- the finished block was not cracked and shrinkage in the length dimension was 13.3%.
- the bulk density of the bar was 309 1bs/cu. ft. (4.95 g/cm 3 ) and the apparent porosity was 0.0%.
- Example 1 The general procedure of Example 1 was followed to make a bar measuring 3" x 3" x 9". Exceptions to that procedure were: the technical grade chromic oxide (about 98% pure) had an average particle size of 0.8 micron and It constituted only 71.1% of the dry weight of the mixture; 25.3% of the dry mixture was the low silica chromite described above and having an average particle size of 5 microns; the fumed silica constituted 1.55% of the dry mixture; and the slurry contained 28% water, 0.74% of the polyvinyl alcohol, 0.13% of the glycol, and 1.3% of the surfactant, by weight. The bulk density of the bar was 274 1bs. per cubic foot and the apparent porosity was 0%. Shrinkage upon firing was 11.7%.
- a large block measuring 6" x 12" x 24" and a 3" x 3" x 9" bar were made according to the general procedure of Example 5 except that the technical grade chromic oxide had an average particle size of 2 microns.
- the bulk density and apparent porosity of the bar were 272 pounds per cubic foot and 2.4%, respectively. No cracks were observed in the cooled block even though the firing shrinkage was 11.9% in length, 12.3% in width, and 11.4% in thickness.
Abstract
Large, dense chromic oxide refractory blocks containing from about 80 % to about 98 % chromic oxide are made by firing a green block comprising, in addition to the chromic oxide, titania and a colloidal silica having a surface area of at least about 90 m?2/g. Blocks having porosities as low as 0 % are made in either an oxidizing or a reducing atmosphere. The blocks are crack-free and have a good resistance to corrosion by molten glass.
Description
HIGH DENSITY CHROMIC OXIDE REFRACTORY BLOCK
This Invention relates to dense refractory blocks having a high chromic oxide content which are used as linings for glass melting furnaces. Large blocks of this kind, typically measuring as large as 6 x 12 x 36 inches, tend to crack while being fired during manufacture. The cracking appears to be caused by stresses stemming from non-uniform densification of the refractory during the firing.
Such blocks are formed by methods generally known by those skilled in making various types of ceramic articles. Various types of procedures are known for preparing, mixing, pressing, and drying the raw materials to form an unfired body and then firing the body in a kiln at high temperatures, generally above 2600°F (1427°C) but below the melting point of the mixture, to develop a ceramic bonded article. The advantages of the method of this invention are not applicable to fusion casting of refractory shapes.
One method to prevent cracking of the large blocks is to encase them in a substantially air tight muffle during firing. The muffling procedure serves to establish uniform atmospheric and temperature conditions throughout the block so that densification and shrinkage is uniform, thus preventing the formation of damaging stresses. Muffling is an expensive procedure because of the cost of materials and labor in building the muffles and because the muffles occupy space in the kiln, thus reducing the number of blocks which can be fired.
Titanium dioxide, or titania, has Ipng been known as an aid in the densification of high chromic oxide refractory blocks. In U.S. Patent
No. 3,773,531, for example, Manigault teaches that a refractory material comprising from 85 to 58% chromic oxide, from 0.5 to 5% titanium dioxide, and from 1 to 10% zircon possesses very low porosity, high resistance to corrosion by molten glass, and is resistant to thermal cracking during firing.
It is an object of this invention to provide a high chromic oxide refractory material which may be fired In the form of a large block without cracking regardless of whether a reducing or oxidizing atmosphere is present in the kiln.
It is another object of this invention to provide large blocks of high chromic oxide refractory material which have good resistance to corrosion by molten glass. It is a related object of this invention to provide a method for manufacturing large, dense, high chromic oxide refractory blocks which are consistently free of cracks.
These and other objects of this invention which will become apparent from the following description are achieved by blending a mixture containing, by weight, from about 80 to about 98% of chromic oxide, from about
1 to about 4% by weight of titania, from about 1 to about 3% by weight of a silica having a surface area of about 90m2/g or greater, from 0% to about 8% alumina, from 0% to about 5% ferric oxide, and from 0% to about 5% magnesia, pressing the blended solids into the desired shape, and firing the pressed shape at a temperature of from about 2600°F to about 3200°F (1427-1760°C) in a kiln in which the atmosphere may contain from about 1.5% excess combustibles to about 1.5% excess oxygen. A preferred mixture contains about 2% each of titania and the colloid-sized silica. The chromic oxide preferably has an average particle size greater than 1 micron, more preferably from about 2 to about 10 microns. A technical grade having a purity of about 98.5% Cr2O3 is suitable. A pigment grade of titania is. preferred;. either anatase or rutile is satisfactory. A finely divided titania such as that sold under the trademark Titanox 1070 by NL Industries, Inc. exemplifies the material used in this Invention.
The silica may be in the form of a sol such as that sold by DuPont under its LUDOX trademark, or it may be a dry powder s.uch as CAB-O-SIL fumed silica sold by Cabot Corporation. The average particle diameter of the colloidal silica may be from about 7 to about 24 nm (0.007 to 0.024 micron).
The alumina, ferric oxide, and magnesia, if present, may originate from a low silica chromite, as may some of the chromic oxide. The chromite, which is a chrome iron ore, may constitute up to about 28% of the dry weight of the blended mixture. A representative sample of the ore contained 35.1% Cr2O3, 28.8% A12O3, 15.4% Fe2O3' 18.8% MgO, 1,8% SiO2 and 0.2% CaO. The silica of the ore does not function like the colloidal silica described above; the average particle size of the ore is preferably from about 3.5 to about 5 microns but it may be from 1 to about 10 microns. Zircon, and other materials which generate silica in situ during the high temperature firing of the block, may be a source of the colloidal silica.
When the block is made from the technical grade of chromic oxide without the addition of the ore, the preferred composition is from about 93% to about 98% chromic oxide, from about 1% to about 4% titania, and from about 1% to about 3% by weight of the colloidal silica. A particularly preferred block made from technical grade chromic oxide contains about
96% of said oxide and 2% of each of the titania and colloidal silica.
A large, dense refractory block is defined for the purposes of this invention as one having a volume of at least about 0.5 cubic foot (0.014 m3) and a density of from about 260 to about 320 pounds per cubic foot. A refractory block made by the method of this invention may be of any useful size or shape but the advantages of this invention are particularly beneficial in the formation of blocks as large as about 2 cubic feet (0.05 m3) such as., for example, one being 6 inches thick, 12 inches wide, and from 24 to 36 inches long. Blocks having right angled cut outs or an inside corner of about a one inch radius have been produced free of cracks, by the method of this invention. A particularly advantageous feature of the blocks of this invention is the fact that their porosity may be as. low as 0% although higher porosities may be achieved if desired.
The green block of this invention may be made in several ways. Slurrying of the chromic oxide, titania, and colloidal silica with water, an organic binder and an emulsifier, followed by spray drying and isostatic pressing is one way. Such a slurry may be slip cast in a plaster mold, also. Dampening of the oxide mixture with about 5 to 10% by weight of an aqueous binder solution and pressing at from 8000 to 12000 psi on a hydraulic press Is another way. Firing of the green block may be carried out In either an oxidizing or a reducing atmosphere. The preferred temperature for firing is from about 2700 to about 3200°F; firing in. a reducing atmosphere at from about 2700 to about 2950°F is especially preferred.
The Invention is described in more detail by the procedures and products of the following examples.
EXAMPLE 1
To 248 pounds of water (about 29.8 gallons, 112.7 kg) there were added 6 pounds of Monsanto' s Gelvatol 20-30 polyvinyl alcohol, 1.2 pounds of Poly G 600 polyethylene glycol (Olin Chemical Co.), 8.0 pounds of Darvan C polyelectrolyte surfactant (Vanderbilt Chemical Co., and a silicone defoamer. To this mixture were added 768 pounds of chromic oxide (Accrox C; average particle size = 4.1 microns, sold by American
Chrome and Chemicals), 16 pounds of titania (Titanox 1070; NL Industries), and 16 pounds of colloidal silica (Cab-O-Sil M-5, surface area = 200 ± 25 m2/g). The solids were blended together by vigorous mixing of the aqueous slurry so that upon spray drying of the slurry a substantially uniform granular refractory material was obtained. A mold sized to yield a 6" x 12" x 24" finished block (12.2 x 30.4 x 60.8 cm) was filled with the granules and evacuated. Green block was formed by isostatic pressing at 20,000 psi. and it was set on its 6 x 24 face in a kiln and fired at 2950°F for 10 hours after the kiln was heated according to the following schedule:
Ambient to 450°F 20°F/hr. Soaked at 450°F 2 hra.
450°F to 1200°F 20°F/hr. 120.0°F to 1600°F 40°F/hr. 1600°F to 2950°F 20°F/hr.
The kiln atmosphere was maintained in the range of 0.5 to 1.5% excess combustibles after the temperature reached 1600°F. After cooling the block to ambient temperature again in the kiln, it was inspected and measured. Apparent porosity and bulk density of the fired refractory was determined from measurements of a 3" x 3" x 9" bar of the refractory material which sat atop the block during firing. The green density of the block was 203 lbs/cu ft (3250 kg/m3) and the fired density was about 293 1bs/cu ft (4688 kg/m3). Despite shrinkage of the block during firing which amounted to 10.76%, 12.73%, and 10.56% in the length, width and thickness dimensions, respectively, no cracks were found in the finished block. An average of 3 measurements of the bar gave a bulk density of 294 1bs/cu ft and an apparent porosity of 0.0%.
In contrast to the above results, a block made in the same way except that the silica had a surface area of 21 m2/g (Reynolds Aluminum Co.) and fired at the same time in the same kiln was found to be cracked upon inspection.
The glass corrosion resistance of the block of Example 1 was tested by suspending lengthwise four rectangular test bars cut from the block in each of three different baths of molten glass contained in platinum crucibles. The surface of the molten glass in each case was maintained at about 1.23 inches. (31.8mm) above the lower end of the test bar. The first set of four bars was held in the molten glass at 2650°F for 348 hours. The second set was held in the bath for 692.5 hours. The third set was held in the molten glass bath at 2700°F for 648 hours. After removal of the molten glass from the crucibles and cooling of the test bars, the extent of corrosion of the bars was measured at the glass line, i.e. where the surface of the glass had met the faces of the bar, and at 17.5mm below the glass line. The
difference in the width of the faces of the bars before and after the tests, called the "cut", was recorded and the service life of the refractory was calculated using the formula: y
The average number of days to cut 1 inch at the glass line, based on measurements of the twelve test bars, was 440. Measurements of the bars below the glass line, when plugged into the above formula and the results averaged, indicated that it would take 515 days of submersion in molten glass to cause a loss of 1 inch of refractory by corrosion under the glass line.
EXAMPLE 2
A refractory block which was fired at the same time in the same kiln as that of Example 1 was prepared by the general procedure of that example except that the chromic oxide had an average particle size of 2.3 microns, only 204 pounds of slurry water were used and the mold was not evacuated before being closed. The block did not crack during firing or cooling even though shrinkage was greater in each dimension.
EXAMPLE 3
A green block having a density of 196 pounds per cubic foot and a bar were made by the general procedure of Example 1 and fired according to the schedule in that example but an atmosphere containing from 1/8 to 1/4.percent excess oxygen was maintained in the kiln after the temperature reached 1600°F. The block had no cracks despite shrinkages of 12.04%, 14.35%, and 13.05% in the length, width, and thickness, respectively. The bulk density, as measured on the bar was 300 pounds/cu ft (4.8 g/cc) and the apparent porosity was 0.0%.
EXAMPLE 4
The general procedure of Example 1 was. followed to make a 6" x 12" x 24" block and a bar but a colloidal silica sol (Ludox HS-40; specific surface area = 230m2/g) was used in place of the fumed silica to make a slurry having the same solids content. The soaking period at 450°F was. also omitted from the firing schedule and the excess combustibles atmosphere was maintained above 1500°F. The finished block was not cracked and shrinkage in the length dimension was 13.3%. The bulk density of the bar was 309 1bs/cu. ft. (4.95 g/cm3) and the apparent porosity was 0.0%.
EXAMPLE 5
The general procedure of Example 1 was followed to make a bar measuring 3" x 3" x 9". Exceptions to that procedure were: the technical grade chromic oxide (about 98% pure) had an average particle size of 0.8 micron and It constituted only 71.1% of the dry weight of the mixture; 25.3% of the dry mixture was the low silica chromite described above and having an average particle size of 5 microns; the fumed silica constituted 1.55% of the dry mixture; and the slurry contained 28% water, 0.74% of the polyvinyl alcohol, 0.13% of the glycol, and 1.3% of the surfactant, by weight. The bulk density of the bar was 274 1bs. per cubic foot and the apparent porosity was 0%. Shrinkage upon firing was 11.7%.
EXAMPLE 6
A large block measuring 6" x 12" x 24" and a 3" x 3" x 9" bar were made according to the general procedure of Example 5 except that the technical grade chromic oxide had an average particle size of 2 microns. The bulk density and apparent porosity of the bar were 272 pounds per cubic foot and 2.4%, respectively. No cracks were observed in the cooled block even though the firing shrinkage was 11.9% in length, 12.3% in width, and 11.4% in thickness.
Claims
1. A refractory material comprising chromic oxide, titania, and a colloidal silica having a specific surface area of at least about 90 m 2/g.
2. The material of claim 1 wherein the silica has an average particle size of from about 7 to about 24 nanometers.
3. The material of claim 1 wherein the chromic oxide has an average particle size greater than 1 micron.
4. The material of claim 1 wherein the chromic oxide has an average particle of from about 2 to about 10 microns.
5. The material of claim 1 wherein the chromic oxide is from about 80% to about 98%, the titania is from about 1% to about 4% and the colloidal silica is from about 1% to about 3% of the weight.
6. The material of claim 5 wherein it comprises from 0% to about 8% alumina, from 0% to about 5% ferric oxide, and from 0% to about 5% magnesia, by weight.
7. The material of claim 5 wherein the chromic oxide is from about 93% to about 98%, the titania is from about, 1% to about 4%, and the colloidal silica is from about 1% to about 3%.
8. The material of claim 5 wherein the colloidal silica and the titania are each about 2%.
9. A refractory block comprising the material of claim 1 and having a density of from about 260 to about 320 pounds per cubic foot.
10. The refractory block of claim 9 characterized further by a porosity as low as 0%.
II. The refractory block of claim 9 further characterized in that its volume is at least about 0.5 cubic foot.
12. The block of claim 11 wherein the volume is from about 0.5 to about 2 cubic feet.
13. A method for forming a refractory block comprising mixing chromic oxide, titania, and a colloidal silica having a specific surface area of at least about 90m2/g, pressing the mixture into a block, and firing the block at a temperature of from about 2600°F to about
3200°F.
14. The method of claim 13 wherein the firing is conducted in a reducing atmosphere.
15. The method of claim 13 wherein the firing is. conducted in an oxidizing atmosphere.
16. The method of claim 13 wherein the mixture contains from about 93% to about 98% chromic oxide, from about 1% to about 4% titania, and from about 1% to about 3% colloidal silica of the weight of the solids.
17. The method of claim 13 wherein a portion of the chromic oxide is present as a chromite ore.
18. The method of claim 13 wherein the mixture contains from about 80% to about 98% chromic oxide, from about 1% to about 4% titania, from about 1% to about 3% colloidal silica, from 0% to about 8% alumina, from 0% to about 5% ferric oxide, and from 0% to about 5% magnesia of the weight of the solids.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE1987905339 DE277190T1 (en) | 1986-08-01 | 1987-07-23 | FIREPROOF CHROME ACID BLOCK HIGH DENSITY. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/891,661 US4724224A (en) | 1986-08-01 | 1986-08-01 | High density chronic oxide refractory block |
US891,661 | 1986-08-01 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1988000931A1 true WO1988000931A1 (en) | 1988-02-11 |
Family
ID=25398614
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1987/001739 WO1988000931A1 (en) | 1986-08-01 | 1987-07-23 | High density chromic oxide refractory block |
Country Status (4)
Country | Link |
---|---|
US (1) | US4724224A (en) |
EP (1) | EP0277190A4 (en) |
JP (1) | JPH01500427A (en) |
WO (1) | WO1988000931A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0546432A1 (en) * | 1991-12-07 | 1993-06-16 | Dyko Industriekeramik Gmbh | Process for the preparation of chromium oxide refractory bricks |
WO2010119422A1 (en) * | 2009-04-15 | 2010-10-21 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Sintered product based on chromium oxide |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5021375A (en) * | 1990-04-19 | 1991-06-04 | Norton Company | Chrome oxide refractory composition |
GB2253844A (en) * | 1991-03-22 | 1992-09-23 | Pilkington Glass Ltd | Throat |
US5219807A (en) * | 1991-06-27 | 1993-06-15 | Indresco Inc. | Burned high purity refractories with low soluble chromium |
US5454258A (en) * | 1994-05-09 | 1995-10-03 | Olin Corporation | Broad range moisture analyzer and method |
FR2971504A1 (en) | 2011-02-15 | 2012-08-17 | Saint Gobain Ct Recherches | DOPE CHROME OXIDE PRODUCT |
TWI657067B (en) * | 2016-02-05 | 2019-04-21 | 美商聖高拜陶器塑膠公司 | Chromium oxide refractory object and methods of forming thereof |
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US3971665A (en) * | 1974-03-18 | 1976-07-27 | Nissan Chemical Industries, Ltd. | Refractory compositions |
US4028122A (en) * | 1973-06-18 | 1977-06-07 | Greenewald Jr Herbert | Porous refractory shapes |
US4040847A (en) * | 1976-04-14 | 1977-08-09 | Johns-Manville Corporation | Temperature stable fibrous insulation composition and "wet" package formed thereof |
US4047965A (en) * | 1976-05-04 | 1977-09-13 | Minnesota Mining And Manufacturing Company | Non-frangible alumina-silica fibers |
US4125406A (en) * | 1973-07-05 | 1978-11-14 | Minnesota Mining And Manufacturing Company | Alumina-chromia-metal (IV) oxide refractory fibers having a microcrystalline phase |
US4374897A (en) * | 1980-03-04 | 1983-02-22 | Nippon Chemical Industrial Co., Ltd. | Chromium oxide-based sintered bodies and process for production thereof |
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Publication number | Priority date | Publication date | Assignee | Title |
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US2498622A (en) * | 1947-11-06 | 1950-02-21 | Corning Glass Works | Refractory composition |
US3773531A (en) * | 1972-07-13 | 1973-11-20 | Taylors Sons Co Chas | Dense chrome refractory material |
US4028123A (en) * | 1973-06-18 | 1977-06-07 | Greenewald Jr Herbert | Compacted refractory shapes |
US4119472A (en) * | 1976-09-01 | 1978-10-10 | Corning Glass Works | Rebonded fusion-cast AZS refractory grain |
US4233079A (en) * | 1979-10-26 | 1980-11-11 | Chicago Fire Brick Company | Aluminous refractory compositions containing carbon, silicon and chrome oxide |
JPS60239355A (en) * | 1984-05-14 | 1985-11-28 | 品川白煉瓦株式会社 | Chromium oxide refractories |
-
1986
- 1986-08-01 US US06/891,661 patent/US4724224A/en not_active Expired - Fee Related
-
1987
- 1987-07-23 EP EP19870905339 patent/EP0277190A4/en not_active Withdrawn
- 1987-07-23 WO PCT/US1987/001739 patent/WO1988000931A1/en not_active Application Discontinuation
- 1987-07-23 JP JP62504928A patent/JPH01500427A/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4028122A (en) * | 1973-06-18 | 1977-06-07 | Greenewald Jr Herbert | Porous refractory shapes |
US4125406A (en) * | 1973-07-05 | 1978-11-14 | Minnesota Mining And Manufacturing Company | Alumina-chromia-metal (IV) oxide refractory fibers having a microcrystalline phase |
US3971665A (en) * | 1974-03-18 | 1976-07-27 | Nissan Chemical Industries, Ltd. | Refractory compositions |
US4040847A (en) * | 1976-04-14 | 1977-08-09 | Johns-Manville Corporation | Temperature stable fibrous insulation composition and "wet" package formed thereof |
US4047965A (en) * | 1976-05-04 | 1977-09-13 | Minnesota Mining And Manufacturing Company | Non-frangible alumina-silica fibers |
US4374897A (en) * | 1980-03-04 | 1983-02-22 | Nippon Chemical Industrial Co., Ltd. | Chromium oxide-based sintered bodies and process for production thereof |
Non-Patent Citations (1)
Title |
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See also references of EP0277190A4 * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0546432A1 (en) * | 1991-12-07 | 1993-06-16 | Dyko Industriekeramik Gmbh | Process for the preparation of chromium oxide refractory bricks |
WO2010119422A1 (en) * | 2009-04-15 | 2010-10-21 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Sintered product based on chromium oxide |
FR2944522A1 (en) * | 2009-04-15 | 2010-10-22 | Saint Gobain Ct Recherches | FRITTE PRODUCT BASED ON CHROME OXIDE. |
US8609563B2 (en) | 2009-04-15 | 2013-12-17 | Saint-Gobain Centre De Recherches Et D'etudes Europeen | Sintered product based on chromium oxide |
Also Published As
Publication number | Publication date |
---|---|
US4724224A (en) | 1988-02-09 |
JPH01500427A (en) | 1989-02-16 |
EP0277190A1 (en) | 1988-08-10 |
EP0277190A4 (en) | 1990-06-27 |
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