RU2299871C1 - Refractory coating composition - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: invention relates to technology of production of refractory materials, which can be used as protective coatings against corrosive media during process heatings and in parts and intermediate products manufacturing processes. Composition according to invention contains, wt %: electrocorundum 35.2-52.0, Oxydal 4.0-6.0, kaolin 0.8-1.2, "Ruzin 12" 2.0-3.0, alumino-magnesium phosphate 18-27, and water 20-30.

EFFECT: improved quality of coatings.

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Description

The invention relates to techniques for the production of refractory materials that can be used as protective coatings against corrosive media during process heating and in the manufacturing process of parts and semi-finished products.

In high-temperature technological processes of the ceramic, glass, and metallurgical industries, protective coatings from the aggressive effects of gases, melts, and slag are used to protect the working surface of refractories, mainly of chamotte class.

Compositions for refractory coatings contain a ceramic component, one or two binders based on organic and inorganic compounds, modifying additives that increase the resistance of the coating to specific aggressive environments. The most widely used compositions using zircon-containing components (SU 539012, 12.27.76; SU 791704, 30.12.80; SU 1291583, 02.23.87; SU 1308595, 07.05.87; SU 1020404, 30.05.83; SU 1031954, 30.07.83 ; SU 1043134, 09/23/83; SU 1604795, 11/7/90).

A disadvantage of the known compositions is the low temperature of use in the range of 1350-1450 ° C.

Refractory mixtures are known containing aluminosilicate ceramics or its components, graphite, silicon containing component, phosphate binder, water (SU 1105486, 1984; SU 889643, 1981; SU 893952, 1981; SU 804603, 1980; SU 791690, 1980; SU 1090676, 1984; RU 2028280, 1995; RU 2136633, 1999).

The disadvantage of such compositions is the low adhesive ability of the coating, the rapid loss of heat resistance and the formation of open porosity when carbon (graphite) burns out, which reduces the operational life of the coating.

Known compositions for protecting refractory materials from aggressive gases and metal melts in the temperature range 1500-1700 ° C, containing aluminosilicate components, inorganic and organic binders, additives and water (SU 444761, 1972; SU 493449, 1972; SU 607818, 1976; SU 608784, 1976; SU 655688, 1979, SU 1079634, 1984; SU 1339111, 1987; SU 1604795, 1990; SU 1655949, 1992; RU 2049761, 1995; RU 2190584, 2002; RU 2239616, 2004; RU 2213714, 2003).

The disadvantages of the known solutions are the unevenness of the coating thickness due to the high viscosity or thixotropy of the compositions, low adhesive bond, high glass phase content, which limits the protective properties in unsteady thermal conditions, significant porosity and, as a result, penetration of the corrosive agent into the pores of the refractory and its destruction.

Closest to the proposed composition is a raw material mixture to obtain a protective coating, including calcium aluminum phosphate binder, aluminum powder, sulphite liquor, 41-52% aqueous dispersion polymer in the following ratio of components, wt.%

Calcium Aluminochromophosphate Binder 25-40 Aluminum powder 7-15 Sulphide liquor 0.1-2.0 41-52% input-dispersed polymer 10-38 Water rest

(SU 1046226, 10.10.83, Bull. No. 37)

A disadvantage of the known solution is the use of explosive finely dispersed aluminum powder, requiring preliminary protection and a high binder content. In addition, the protective coating obtained from this mixture cannot be used above the melting temperature of partially oxidized aluminum, of which aluminum powder is composed.

The purpose of the invention is improving the quality of the refractory coating.

This goal is achieved in that the composition for the manufacture of a refractory coating comprising an alumina ceramic component, a complex of a phosphate and organic binder, water, as an alumina ceramic component contains a mixture of alumina, oxide and kaolin, the binder complex contains aluminum-magnesium phosphate and an acrylic acid copolymer " Ruzin 12 "in the following ratio of components, wt.%:

Electrocorundum 35.2-52.8 Oxidized 4.0-6.0 Kaolin 0.8-1.2 Ruzin 12 2-3 Aluminum Magnesium Phosphate 18-27 Water 20-30

The essence of the proposed technical solution is as follows:

- the introduction of electrocorundum, as the basis of the ceramic component, is justified by its stable structure, hardness against abrasion, and its amphotericity provides stability against exposure to acid and alkaline environments;

- the introduction of oxidal and kaolin allows you to eliminate possible defects in the packaging of electrocorundum particles at high temperatures and give strength as a high-temperature ceramic bond;

- the use of an acrylic acid copolymer under the brand name "Ruzin 12" in the composition increases the performance properties of the coating in the raw material by increasing the adhesion and elasticity of the composition, which increases the resistance of the coating during transportation against shearing and impact loads, while removing excess water during drying, the crack resistance increases, and confidence intervals of the content of "Ruzin 12" are due to the fact that below 2 wt.% it is possible to shed the coating from the surface of the refractory, and above 3 wt.% the technological time moisture removal;

- the presence of aluminum-magnesium phosphate in the composition makes it possible to obtain a coating with increased heat resistance and adhesion strength at operating temperatures above 1500 ° C, which forms at room temperatures, introduce magnesium ion as a modified additive, resistant to glass and metal melts, and the concentration limits of aluminum-magnesium phosphate are limited by the technological time survivability and dehydration processes at high temperatures;

- the concentration limits of the water content are determined from the standpoint of coating by known methods of ejection spraying or slip impregnation, since at 20 wt.% water the viscosity of the composition allows the necessary coating layer to be applied only by spreading, and at 30 wt.% water it is difficult to keep the calculated coating on the surface of the refractory thickness, which leads to the cyclic application of subsequent layers after preliminary drying of the applied layer.

Examples of the implementation of the proposed technical solutions using raw materials:

Electrocorundum TU 3988-075-0022450-99

Oxidal TU - 8.39157-26003 (dust of electrostatic precipitators of the Achinsk Alumina Refinery, cleaned of iron and alkaline components and calcined to α - Al ₂ O ₃ )

Kaolin TU - 57-29-070-00284530-96

"Ruzin 12" TU 2241-005-57845504-2003

Aluminum Magnesium Phosphate TU 2149-068-10964029-2000

Water - technical

The raw material mixture is prepared as follows:

Example 1. A water-dispersion binder complex was prepared containing 6 g of a 50% concentration of Ruzin 12 "acrylic emulsion and 54 g of a 50% concentration of aluminum-magnesium phosphate solution. The components for homogenization were mixed for 5 minutes.

Dry components are loaded into the mixer based on 100 g of the composition: 35.2 g of electrocorundum, 4.0 g of oxidal and 0.8 g of kaolin. Dry components are mixed for 10-15 minutes. The resulting mixture was introduced portionwise into the aqueous dispersion complex of the binder with constant mixing for 20 minutes. The finished composition was sprayed onto silicon carbide substrates and dried at a temperature of 100-120 ° C for 2-3 hours.

Example 2. A water-dispersion binder complex was prepared in a mixer at the rate of 5 g of a 50% concentration of acrylic emulsion “Ruzin 12” and 45 g of a 50% concentration of a solution of aluminum-magnesium phosphate. The components were mixed for 5 minutes.

The dry components were loaded into the mixer at the rate of: 44 g of electrocorundum, 5 g of oxidal and 1 g of kaolin. Mixing was carried out dry for 12 minutes. The resulting dry mixture was introduced portionwise into the aqueous dispersion complex of the binder with constant stirring; the total mixing time was 18 min. The finished composition was sprayed onto the working surface of fireclay refractory for lining glass melting furnaces and dried for 2 hours.

Example 3. A water-dispersion binder complex was prepared in a mixer at the rate of 4 g of a 50% concentration of the Ruzin 12 acrylic emulsion and 36 g of a 50% concentration of a solution of aluminum-magnesium phosphate. The components were mixed for 5 minutes.

The dry components were loaded into the mixer at the rate of 52.8 g of electrocorundum, 6 g of oxidal, 1.2 g of koalin. Mixing was carried out dry for 10 minutes. The resulting dry mixture was introduced portionwise into the aqueous dispersion complex of the binder with constant stirring for 25 minutes. The finished composition was applied to the inner surface of the chamotte metal wire for casting steel by pouring a slip through the inner cavity of the metal wire and dried for 1 hour.

The obtained options for products with the proposed coating were previously tested under different conditions. Silicon carbide plates coated with a thickness of 2-3 mm were used as substrates for sintering corundum-mullite products at a temperature of 1650 ° C. The turnover of the plates increased by 25-30 times while maintaining the adhesive strength of the coating. After a 25-fold rotation of the plates, the shear strength was equal in value to the strength of the silicon carbide material, since the destruction passed through the volume of the plate.

The identical nature of the destruction was established when using fireclay products with a coating when cooking glass E, for the production of basalt fiberglass and for casting steel.

When casting 150 tons of steel, the metal wire did not overgrow, and it could be used in the following technological cycles. Positive results were obtained when using the composition in corundum crucibles during induction melting of nickel alloys, where clogging of the alloy with crucible material was excluded. In laboratory conditions, the possibility of using the proposed composition in sealing cracks, chips and technological joints when laying the lining of thermal units has been experimentally confirmed.

Thus, the technical usefulness was confirmed and the goals of the claimed object were realized.

Claims (1)

Composition for a refractory coating comprising an alumina ceramic component, a complex of a phosphate and organic binder, water, characterized in that the alumina ceramic component consists of a mixture of electrocorundum, oxide and kaolin, the binder complex contains aluminum-magnesium phosphate and an acrylic acid copolymer "Ruzin 12" in the following the ratio of components, wt.%: Electrocorundum 35.2-52.0 Oxidized 4.0-6.0 Kaolin 0.8-1.2 "Ruzin 12" 2.0-3.0 Aluminum Magnesium Phosphate 18-27 Water 20-30