CS213420B1 - Refractory sealants and paints. - Google Patents

Abstract

The invention is based on refractory sealants and coatings with a ceramic filler and binder based on refractory oxides Al2O3, SiO4, MgO, CrO4, ZrO4, their mutual compounds or mixtures of carbide and carbon, with a chemical and organic binder. The products are characterized by a very fine grain size of up to 0.5 mm, a temperature of use in the range from 1200 °C to 1750 °C, good adhesion to the underlying material and high bond strength. The sealants and coatings are used for tight bonding of dense and insulating refractory products, including fibrous ones, and surface protection of linings made of these materials from aggressive and erosive environments.

Description

The invention relates to refractory sealants and coatings for tight bonding of dense and insulating refractory products, including fibrous ones, and surface protection of linings made of these materials from aggressive and corrosive environments, based on ceramic aggregates, which are fired clays, fired kaolin shale, corundum, synthetic or natural high-alumina aggregates, zircon, quartz or silica sand, magnesite, graphite, amorphous silica, binders, based on clays, kaolins, ground alumina, magnesium, silica, aluminosilicate, their basic components are oxides of silica, alumina, zirconium, magnesium, chromium, their mutual compounds or mixtures, carbides or pure carbon, supplemented with organic and chemical binders.

So far, refractory mortars have been used for joining refractory fittings when lining furnace units in metallurgy, mechanical engineering, energy, cement, ceramics, etc., characterized by a relatively coarse grain size of up to 2 mm or more and by the fact that the mortar solidifies and therefore the actual bonding effect occurs only after the lining is fired to the required temperature. However, this condition is not met, which causes insufficient solidification of the mortar, which falls out of the joints, the fittings loosen during temperature changes or mechanical influences (vibration, etc.) and the unit must be prematurely shut down for repair. The required temperature is usually reached only on the inner side of the lining, exposed to heat. However, because the temperature in the lining decreases towards the outer part, which also increases the degree of mortar solidification and therefore the joint. Wide joints in the lining, often up to 5 mm or more, caused by coarse-grained material, are the weakest point of the lining, especially where a corrosive environment is present. In a corrosive environment, the poorly consolidated porous mortar is attacked and dissolved much faster. This leads to a faster deterioration of the entire lining.

The above-mentioned shortcomings are eliminated by refractory sealants and coatings for joining refractory fittings and forming internal protective layers for lining according to the invention, which contain 40 to 90% of ground refractory fillers with a grain size of up to 0.5 mm, the composition of which corresponds to the main components of silicon dioxide, aluminum, magnesium, zirconium, aluminous oxide, carbides and raw materials based on free carbon, their compounds or mixtures, 10 to 60% of a clay or oxide binder based on refractory oxides ground with a grain size of up to 0.06 mm, 0.5 to 10% of a chemical binder, 0.2 to 5% of a water-soluble organic binder, 0 to 2% of surfactants and 0 to 50% of liquid components for accelerating the drying process. The filler may be burnt clay or kaolin, shale, corundum, zircon, calcined magnesite, quartz or silica sand, graphite, silicon carbide, crushed and ground fragments of dense or insulating refractory products, lightweight fillers such as caramzite, perlite and vermiculite. The ceramic binder may be refractory clay, kaolin, ground refractory oxides, carbides or silica salts. The maximum grain size of the filler 0.5 μm is chosen with regard to achieving minimum gaps between the fittings and increasing the specific surface /covering capacity/ when used in the form of a coating. The ceramic binder contains a minimum. 80% of particles below 0.06 mm when determining the grain size by the sedimentation method, the properties and effect of the ceramic binder is improved by the addition of chemical binders, which are phosphoric acid, sulfuric acid, hydrochloric acid or their salts and organic binders soluble in water, which are e.g. carboxymethyl cellulose. polyvinyl alcohol. dextrin. starch and nod.

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Mixtures of this composition are divided with a drain or other liquid components just before use or in advance. Sealants of this composition create a strong joint in the entire temperature range from a minimum of 60 °0 to the temperature of use given by the composition of the sealant. They have very good adhesion to fired ceramic material and metal construction, the thickness of the joints can be significantly reduced.

When using mastic as a coating, it is possible to protect the front side of the lining against the corrosive effects of metals, slag, dust drift, vapors, etc., or the erosive effects of gases flowing at high speed, etc. They are suitable as protective layers with a thickness of 2 to 5 mm. For the protection of linings of ceramic and glass furnaces, induction furnaces for melting metals, combustion chambers of energy equipment, drying equipment, containers for liquid metals / ladles, intermediate ladles, torpedo ladles, etc. /, protection against scale, etc. The coating is prepared by diluting the mastic with water or another liquid that supports faster solidification of the material during drying /alcohol, polyethylene glycol, etc. /. It is applied to the surface of the lining manually, e.g. with a brush or by machine spraying in a layer of 2-5 mm.

Very extensive use can be achieved in gluing insulation boards, mats, etc. made of fibrous materials both to fireclay lining and to create joints of fibrous materials without an anchoring system or with its significant limitation. With the help of coatings, materials, a protective layer against erosion and corrosion can be created on the surface of fibrous and classic fired insulation materials and extend their service life.

Examples of composition.

1. Fireclay putty ?0% kaolin, clay or burnt shale, ground to a grain size of up to 0.5 mm % mixture of floated kaolin and refractory clay in the ratio lsl with a grain size of up to 0.06 mm 5.5% primary aluminum phosphate 0.5% carboxymethyl cellulose

The mixture is thoroughly mixed with water so that the organic and chemical components melt first, then the clay and finally the non-plastic component. The following product properties were achieved after firing at 1400 °C« temperature of use 1500 °C refractoriness 1750 °C alumina content after annealing 40 % ferric oxide content after annealing 1.0 % shear strength of the joint 10 MPa very good adhesion without cracks

When using the sealant as a bonding material for fibrous insulation, a strong bond between the boards was achieved up to their maximum use temperature of 1250 °C. Likewise, when used as a protective layer on fired and fibrous insulation products, very good adhesion to the surface of the products was achieved and a hard, mechanically resistant layer was created. . 2. High-aluminum sealant % white electrocorundum with a grain size of up to 0.2 mm % up to 0.06 mm % ground alumina -- up to 0.04 mm

420% phosphoric acid with a concentration of 55%% polyvinyl alcohol powder

After dilution with water to a suitable consistency, the following properties were achieved:

use temperature up to 1800 °C heat resistance 1980 °0 oxide content aluminum 97% after annealing oxide content ferrous after annealing 0.4% max. grain size 0.2mm joint strength in cut after firing at l$00 °0 12 MPa

The sealant was used with very good results for bonding high-alumina and corundum products, dense and insulating. It was used with favorable results as a protective layer on high-alumina insulating lining.

Acid siliceous putty % quartzite or silica sand with a grain size of up to 0.5 mm % up to 0.09 W % up to 0.04 mm % primary calcium phosphate % starch powder

The following properties were achieved:

temperature of use 1650 °0 refractoriness 1730 °C grain size up to p.5 mm silica content 97% ferric oxide content 0.6% alumina content L.0% shear strength of the joint after firing at 1500 °C is 8 MPa

The sealant was used for joining dinas and silicate fittings. It is suitable for use in sealing dinas vaults, coke oven batteries, metallurgical slag, lightweight silicate fittings, sealing joints, cracks, etc. in masonry, etc.

4. Magnesium putty % calcined magnesite with a grain size of up to 0.5 mm % calcined magnesite with a grain size of up to 0.09 mm % calcined magnesite with a grain size of up to 0.04 mm % secondary sodium phosphate % sulphite leachate

The following properties were achieved: * application temperature 1650 °C, refractoriness more than 1900 °C, grain size up to 0.5 mm

213 420 content of magnesium oxide more than 85% strength of the joint after firing at 1600 °C is 12 MPa the sealant was used for sealing magnesite, chromomagnesite, magnesitechromite and chromite products. It is also suitable for creating a protective layer on tamped linings made of basic granular materials.

5. Protective coating for the linings of induction furnaces for melting aluminum % high-aluminum grinding stone / sillimanite, andalusite, mullite, etc./ with a grain size of up to 0.5 mm 20 % stoneware clay with a grain size of up to 0.06 mm 25 % crystalline silica up to 0.06 mm

5% sodium hexametaphosphate % liquor

After mixing with water, to which 1 to 2% of a surfactant had been added in advance, a suspension was prepared with the following properties: temperature of use up to 900 °C in a slightly oxidizing environment, refractoriness 1750 °C, grain size up to 0.5 mm, chemical composition after drying: .

carbon 24% aluminum acid 30% ferric acid 1%

When used as a protective layer on the inner part of the steamed lining of an induction furnace for melting aluminum, a hard layer 3 mm thick was created, increasing resistance to the corrosive effects of metal and additives, and the service life of the lining increased 3 times.

6. Zirconium protective layer for ceramic linings % zirconium sand with a grain size of up to 0.2 mm % zirconium flour -- up to 0.075 mm % -- ground up to 0.04 mm % zirconium oxychloride % carboxylmethylcellulose

After mixing with water, the mixture was used to create a protective layer on the wall of a tunnel kiln for firing glazed tiles. It can be used as a sealant for joining zirconium products. After firing at 1700 °C, the following properties were achieved: temperature of use 1750 °C, refractoriness more than 2,000 °C, zirconium dioxide content 62%, silica 34%, grain size up to 0.2 mm.

7. Sealant for joining insulating products % ground fragments of insulating fireclay with a grain size of up to 0.5 mm % refractory clay % aluminum sulfate % powdered polyvinyl alcohol

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The mastic, after mixing with water, was used for bonding refractory insulation products, both fired and fibrous, in the form of mats and boards. Excellent adhesion and bond strength were achieved up to a temperature of 1450 °C. The ground fractions contained 38% alumina, and the refractory value was 1750 °C.

8. High-aluminum coating of molds for foundry purposes % corundum with a grain size of up to 2 mm % ground alumina with a grain size of up to 0.04 mm % chromium oxide with a grain size of up to 0.04 mm % polyvinyl alcohol powder.

After diluting with ethyl alcohol to a consistency suitable for coating, a quick-drying coating of molds for special castings was created. A flawless surface of the castings was achieved.

Claims (4)

1. Refractory sealants and coatings for joining all types of dense and insulating heat sources of air materials and for performing protective coatings of refractory linings with ceramic filler and binder based on heat-resistant acid oxides. Aluminum, siliceous, magnesium, chromium, zirconium, their mutual compounds or mixtures, carbides and carbon, characterized in that they contain 40 to 90% of filler with grain size up to 0,5 mm, 10 to 60% of ceramic binder containing at least 80% of particles below 60 microns, 0.5-10% chemical binder, 0.2-5% water-soluble organic binder, 0-2% surfactant, and 0-30% liquid component, accelerating drying. 2. Refractory sealants and coatings according to claim 1, characterized in that the chemical binder is phosphoric acid, sulfuric acid, hydrochloric acid or salts thereof, preferably in aqueous solution. 3. Refractory sealants and coatings according to claim 1, characterized in that the surfactants are substances which improve the wettability of non-water-wettable materials, for example sulfonates or polyphosphates. 4. Refractory sealants and coatings according to claim 1, characterized in that the liquid components for accelerating the drying process are substances with a lower boiling point than water, for example ethyl alcohol.