RU2445290C1 - Refractory mixture - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to refractory industry and can be used in production of refractory materials, for repairing lining of melting facilities, particularly converters and electric steel furnaces, e.g., by filling or guniting. Disclosed is a periclase-based refractory mixture containing carbon, phenol-formaldehyde resin, sodium polyphosphate, boric acid, coal-tar pitch and alumina-containing material, which contains not less than 70 wt % aluminium oxide, with the following ratio of components, wt %: carbon 5.0-9.0; phenol-formaldehyde resin 3.0-3.8; sodium polyphosphate 1.0-2.0; boric acid 0.5-1.0; coal-tar pitch 1.0-3.0; said alumina-containing material 8.0-20.0; periclase 61.5-81.0. The alumina-containing material used is corundum or spinel, or mixture thereof with particle size of not more than 1.0 mm in any weight ratio. The carbon used is graphite or coke or mixture thereof with particle size smaller than 1.0 mm in any weight ratio.

EFFECT: low evaporating capacity of magnesium oxide from the refractory mixture, which ensures high wear-resistance of the lining.

3 cl, 3 tbl

Description

The invention relates to the refractory industry and can be used in the manufacture of unformed refractories for the repair of steelmaking units, in particular converters.

Known refractory mass containing scrap magnesia carbon-containing products with a particle size of 0.5-20.0 mm, including 9-10 wt.% Graphite, 1.5-2.0 wt.% Sodium tripolyphosphate, 0.5-0.9 wt.% Boric acid and 10 , 0-15.5 wt.% Carbon-containing organic component, which can be used coal tar pitch [1].

Known mass is characterized by a short sintering time and good flowability under high temperature exposure.

However, the presence in the mass of a high content of carbon-containing organic matter (10.0-15.5 wt.%) And carboxylmethyl cellulose (0.5-0.7 wt.%) During coking and high-temperature oxidation leads to the formation of a highly porous melt-permeable ceramic refractory texture. In the case of complete oxidation of such concentrations of these carbon-containing organic components, the total porosity of the products of high-temperature sintering of the mass can be 30-35%, which will cause not only a sharp decrease in mechanical strength, but also significantly intensify the erosion-corrosion wear of the lining. As a result of these physicochemical processes, a significant decrease in the resistance of the refractory mass occurs. In addition, the high content of carcinogenic substances in the form of coal tar pitch makes this mass environmentally dangerous.

The closest to most of the essential features to the claimed one is a refractory mass containing a magnesia aggregate fraction of not more than 4 mm in the form of a mixture of periclase and periclase-carbon components, phenol-formaldehyde resin, sodium polyphosphate and optionally boric acid and coal tar pitch in the following ratio of components, wt.%: Polyphosphate sodium no more than 2, phenol-formaldehyde resin 4-5, coal tar pitch 0-3, boric acid 0-2, a mixture of fused periclase or periclase-carbon products, or a mixture dedusted scrap of periclase products and dedusted scrap of periclase-carbon products - the rest [2].

It is known [3, 4] that a mixture of periclase and periclase-carbon materials consists of periclase (MgO), crystalline and amorphous carbon, respectively, in the form of graphite and coke, with a total carbon content of 6-11 wt.% In any mass ratio, while the particle size distribution carbon composition is not regulated.

This known refractory mass is characterized by satisfactory durability and manufacturability both in manufacturing and in operation in steelmaking converters, however, a further increase in its wear resistance is limited by the characteristics of the material composition, in particular, the high total content of highly refractory materials based on periclase and carbon (up to 88-94%) . The theory and practice of the production and use of carbon-containing refractories showed that during the service of periclase-carbon compositions, an intense high-temperature chemical interaction occurs between periclase, carbon and the product of its incomplete oxidation - carbon monoxide (СО) according to the following reactions:

As a result of direct (reaction 1) and indirect carbothermal reduction (reaction 2) periclase, magnesium metal is formed having a melting and boiling points of 651 and 1095 ° C, respectively.

Due to reactions 1 and 2, periclase evaporates, which leads to an increase in porosity, capillary impregnation with molten slag and metal, and ultimately increased wear of the refractory.

The aim of the present invention is to eliminate this drawback while maintaining other positive properties of the refractory mass.

The technical result consists in increasing the wear resistance of the refractory mass.

To achieve a technical result according to the claims, the refractory mass of the composition, wt.%: Periclase fraction is not more than 4 mm 61.5-81.0; carbon fractions less than 1 mm 5.0-9.0; phenol formaldehyde resin 3.0-3.8; sodium polyphosphate 1.0-2.0; boric acid 0.5-1.0; coal pitch 1.0-3.0, additionally contains alumina material in an amount of 8.0-20.0 wt.%, containing at least 70 wt.% alumina, and corundum or spinel, or a mixture thereof, is used as an alumina material fractions less than 1 mm.

In addition, the essence of the invention lies in the fact that the mass contains a quantitative ratio different from the known refractory masses of the reactive main highly refractory mineral components: periclase and carbon in the form of graphite or coke, or a mixture thereof in any mass fraction ratio of less than 1.0 mm in combination with organic binders (phenol-formaldehyde resin and coal tar pitch) and sintering additives - mineralizers (sodium polyphosphate and boric acid). The decrease in the content of periclase and carbon with melting points of 2800 and 3500 ° С, respectively, is compensated by the presence of highly refractory aluminous minerals in the form of corundum or spinel with melting points of 2050 and 2135 ° С, respectively, or their mixture, and small particles of these compounds additionally play the role of physical screens isolating larger grains of periclase aggregate and carbon.

This specific nature of the mineralogical microstructure of the proposed mass provides a decrease in the intensity of the above chemical reactions 1 and 2 and, as a result, leads to an increase in the wear resistance of the refractory mass.

When the carbon content is less than 5 wt.% Not ensured slag resistance of the mass. If the amount of this component is more than 9 wt.%, The mechanical strength decreases, the intensity of recovery and evaporation of periclase sharply increases, which leads to a decrease in the duration of operation of the refractory.

When the content of organic binders represented by phenol-formaldehyde resin and coal tar pitch is lower than the stated limits, the low-temperature strength of the mass is not achieved, and if they are exceeded, the high-temperature strength decreases and the resistance decreases due to erosive wear of the mass. With a decrease in the content of sintering components represented by boric acid and sodium polyphosphate, less than the stated limits, the formation of a dense and durable ceramic structure in the medium temperature range of 450-1000 ° C is not provided. If the upper concentrations of these components are exceeded, the high-temperature strength decreases and the wear of the refractory by reflow is enhanced.

The optimal content of the refractory base - periclase (MgO), having a melting point of 2800 ° C, is 61.5-81.0 wt.%. With a lower content of periclase, refractoriness and metal and slag resistance are not ensured, which leads to a decrease in the resistance of the refractory mass. At a higher content of periclase, wear resistance also decreases due to the increased recovery rate and its evaporation.

An alumina mineral containing at least 70% alumina (Al ₂ O ₃ ), represented by corundum (α-Al ₂ O ₃ ) or spinel (MgAl ₂ O ₄ ), or a mixture thereof, must be contained in an amount of 8.0-20, 0 wt.%. When the content of these components is less than 8.0%, the function of inhibiting the recovery and evaporation of periclase is not provided.

Corundum and spinel, unlike periclase, have high thermodynamic stability and resistance to carbothermal reduction, therefore, at temperatures of steelmaking processes (1580-1670 ° C) they are not subjected to carbothermic reduction and evaporation.

When the content of corundum and spinel is more than 20%, there is a decrease in slag resistance as a result of intensification of chemical wear by reactions:

In addition, when the content in the alumina-containing component is less than 70% Al ₂ O ₃ , a sufficient volumetric coating of periclase with corundum and (or) spinel is not achieved by a protective coating that prevents direct contact with carbon.

The proposed refractory mass is as follows.

To obtain the mass, a large assortment of well-known synthetic and technogenic raw materials is used:

- crystalline graphite, GOST 7478-75;

- technical carbon, GOST 25699.6-90;

- phenolic powder binder, TU 2257-241-00203447-97;

- sodium polyphosphate, GOST 20291-80;

- boric acid, GOST 18704-78;

- coal tar pitch, GOST 1038-75;

- scrap periclase products fractions of not more than 4 mm;

- scrap periclase-carbon products fraction not more than 4 mm;

- scrap aluminum-periclase-carbon products of a fraction of less than 1.0 mm;

- scrap of spinel-periclase-carbon products of a fraction of less than 1.0 mm, TU 1579-034-00187085-2004;

- fused periclase grade PPPL-95, fractions no more than 4 mm, TU 322-24-009-94;

- fused corundum fractions less than 1.0 mm, TU 1523-007-00187085-2001;

- fused spinel fractions of less than 1.0 mm, TU 1527-031-00187085-2004.

For the manufacture of refractory mass used dosage mixtures of the above raw materials of regulated grain and chemical compositions, are shown in table 1 (examples 1-6). A mixture of periclase, binders and sintering components was mixed for 10 minutes, after which the finished mass was packaged in a sealed package.

The material composition of the resulting refractory mass is shown in Table 2. The principal difference between the proposed mass and the known mass is the presence of an alumina material with an Al ₂ O ₃ content _of at least 70% in the form of corundum and (or) spinel, as well as the optimal quantitative ratio of the components.

The properties and chemical composition of the refractory mass are shown in table 3. As can be seen from the data in table 3, the inventive mass has a higher resistance to reduction and evaporation of magnesium oxide while maintaining the same indicators of other physicochemical properties.

The sintering time was determined visually by fixing the time of complete cessation of the flame from the burning of volatile components of pitch and resin. The porosity and compressive strength were determined according to GOST 2409-95 and GOST 4071.1-94, respectively, on samples subjected to heat treatment at a temperature of 1350 ° C for 2 hours.

The determination of slag resistance was carried out by the static crucible method using converter slag of the following chemical composition, wt.%: CaO 46.0; SiO ₂ 17.5; ∑ (FeO + Fe ₂ O ₃ ) 16.7; MnO 6.8; MgO 6.3; Al ₂ O ₃ 6.7 at a temperature of 1610 ° C. Slag resistance was assessed by measuring the areas of melt impregnation and corroding in a vertical section of crucibles formed from a refractory mass and previously calcined at 1350 ° C.

Determination of volatility was performed on samples pressed at a specific pressure of 100 N / mm ² , annealed at 1000 ° C and 1610 ° C with a holding time of 3 hours at each temperature. The calculation of volatility (I) was carried out according to the formula

where C ₁ is the MgO content in the sample calcined at 1000 ° C;

C ₂ is the MgO content in the sample calcined at 1610 ° C.

The proposed refractory mass was tested in the oxygen-converter shop of OJSC “Magnitogorsk Iron and Steel Works”, where it showed wear resistance of 15-33% more compared to the prototype mass (see table 3).

For the manufacture of the mass, you can use a wide range of available synthetic and man-made raw materials.

Information sources

1. RF patent №2243184.

2. RF patent No. 2379255.

3. Perepelitsyn V.A. Fundamentals of technical mineralogy and petrography. - M .: Nedra, 1987 .-- 255 p.

4. Kashcheev I.D. Oxide-carbon refractories. - M .: Intermet Engineering, 2000 .-- 265 p.

Table 1 Raw material The inventive composition, wt.% Outside, wt.% Example 6 * Example 1 Example 2 Example 3 Example 4 Example 5 Periclase fused PPPL-85 fractions 4.0-0.1 mm 80.5 - 20,0 - - 10.0 Crystalline graphite 3.0 - - - - - Technical carbon 2.0 - - - - - Scrap periclase fractions 4.0-0.1 mm - 15,5 - 40,0 - - Scrap periclase-carbon fractions 4.0-0.1 mm ** - 50,2 28.0 40.5 41.5 81.0 Scrap aluminopericlase-carbon fractions 4.0-0.1 mm ** - 15.0 - - 20,0 - Scrap spinel-carbon fractions 4.0-0.1 mm ** - 10.0 35,2 - 35.0 - Corundum fused fraction less than 1.0 mm 8.0 - - 6.0 - - Spinel fused fraction less than 1.0 mm - 2.0 8.0 - - - Phenol formaldehyde resin 3.0 3.8 3.8 5,0 2.0 5,0 Coal tar pitch 1,0 2.0 3.0 4.0 0.5 1,0 Boric acid 0.5 0.5 1,0 1,5 0.5 1,0 Sodium polyphosphate 2.0 1,0 1,0 3.0 0.5 2.0 * Known composition (RF patent 2379255) ** The scrap of all oxide-carbon products contains, wt%: crystalline graphite 3-10, amorphous carbon (coke) 1-2

table 2 Component The inventive composition, wt.% Outside, wt.% 6 * one 2 3 four 5 Phenol formaldehyde resin 3.0 3.8 3.8 5,0 2.0 5,0 Sodium polyphosphate 2.0 1,0 1,0 3.0 0.5 2.0 Boric acid 0.5 0.5 1,0 1,5 0.5 1,0 Coal tar pitch 1,0 2.0 3.0 4.0 0.5 1.0 Corundum (α-Al ₂ O ₃ ) 8.0 12.0 2.0 6.0 15.0 - Spinel (MgAl ₂ O ₄ ) - 2.0 18.0 - 7.0 - Periclase (MgO) 80.5 71.7 62,2 76.5 63.5 83.0 Carbon (C) 5,0 7.0 9.0 4.0 11.0 8.0 * Known composition (RF patent 2379255)

Table 3 Indicators The inventive composition Outside Example 6 * Example 1 Example 2 Example 3 Example 4 Example 5 Content, wt.% MgO 76.5 68.3 68.1 76,4 63.7 82.9 Al ₂ O ₃ 7.8 14.9 13.8 5.9 21.3 - Na ₂ O 0.61 0.30 0.30 0.91 0.15 0.61 P ₂ O ₅ 1.39 0.70 0.70 2.10 0.35 1.39 B ₂ O ₅ 0.28 0.28 0.56 0.84 0.84 0.56 P.P.P. 13,42 15,52 16.54 13.85 13.66 14.54 Sintering time, min 7 8 6 8 8 5-8 Open porosity,% 19.3 16.8 17.4 10.9 31,0 18.0-19.1 The limit of compressive strength, N / mm ² 23.7 25,4 18.7 27.2 16.3 23.0-25.4 Slag resistance: impregnation area, cm ² , 9.6 8.9 10.3 16,2 18,4 8.8-10.3 corrosion area, cm ² 6.0 7.0 6.8 7.2 1.9 6.0-7.1 Evaporation of MgO, wt.% 2.5 1.7 1,6 6.8 1.3 7.5-8.2 The resistance in the converter, the number of heats fifteen 16 fifteen 12 10 12-13 * Known composition (RF patent 2379255) P.P.P. - weight loss during calcination at a temperature of 1000 ° C

Claims (3)

1. Refractory mass, including periclase, carbon, phenol-formaldehyde resin, sodium polyphosphate, boric acid and coal tar pitch, characterized in that it additionally contains alumina-containing material containing at least 70 wt.% Alumina, in the following ratio, wt.% :
carbon 5.0-9.0 phenol formaldehyde resin 3.0-3.8 sodium polyphosphate 1.0-2.0 boric acid 0.5-1.0 coal tar pitch 1.0-3.0 specified alumina-containing material 8.0-20.0 periclase 61.5-81.0 2. The refractory mass according to claim 1, characterized in that the alumina-containing material is corundum (α-Al ₂ O ₃ ), or spinel (MgAl ₂ O ₄ ), or a mixture thereof in any mass fraction of the fraction of less than 1.0 mm 3. The refractory mass according to claim 1, characterized in that it contains graphite or coke as carbon, or a mixture thereof in any mass fraction ratio of less than 1.0 mm.