RU2263645C1 - Mass for making basic refractory articles - Google Patents

Abstract

FIELD: industry of refractory materials.

SUBSTANCE: invention proposes periclase-base mass with purity 95% of MgO, not less, for making basic refractory articles consisting of granular periclase, finely divided component and a temporary binding agent comprises granular periclase of fraction 0-3 mm and finely divided component comprises periclase of fraction less 0.088 mm, and zirconium dioxide and/or zircon of fraction less 0.088 mm, and/or alumina - Al₂O₃ of fraction less 0.010 mm, and boric acid of fraction less 0.088 mm in the following ratio of components, wt.-%: periclase of fraction less 0.088 mm, 79.0-98.7; zirconium dioxide and/or zircon of fraction less 0.088 mm, and/or Al₂O₃ of fraction less 0.010 mm, 1-20; boric acid of fraction less 0.088 mm, 0.3-1, and in the following ratio of mass components, wt.-%: granular periclase of fraction 0-3 mm, the base; finely divided component, 15-35; temporary binding agent (above 100%), 3-7. Invention can be used for casting liquid metals, in particular, for making plates of slide closing devices. Invention provides reducing porosity and enhancing strength in retaining heat resistance.

EFFECT: improved and valuable properties of mass.

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Description

The invention relates to the refractory industry and can be used for the manufacture of products operating in the conditions of prolonged casting of liquid metals, in particular for the manufacture of slab gate valves.

Refractories for slide gates should have the following properties: high mechanical strength, low porosity with sufficient heat resistance, high deformation temperature under load, low content of fusible materials.

A known method of manufacturing a magnesia refractory product from 97-30% magnesite of 95% purity and 3-70% zircon with optional Al ₂ O ₃ additive (Japanese application No. 3232764, 04 04 35/04, 1994).

The disadvantage of this magnesian product is the lack of heat resistance. It is known that the heat-resistant structure of the refractory is formed by introducing additives of materials that contribute to the formation of a microcracked structure (in this case, additives of zircon and Al ₂ O ₃ ), as well as through the use of materials of various granular fractions. The second method of increasing heat resistance in this invention is not implemented.

It should also be noted that the introduction of a significant amount of zircon ZrO ₂ · SiO ₂ (over 20%) into the mass composition increases the content of silicon dioxide SiO ₂ in the refractory composition and this can lead to the formation of fusible materials during the service, which also reduces the operational properties of the refractory.

The closest to the invention in terms of material and grain composition is a refractory mass based on sintered or fused magnesia with an MgO content of at least 96% with the addition of 1.0-2.5 wt.% ZrO ₂ with a purity of at least 95% and a grain size of less than 0.040 mm in the form of baddeleyite or stabilized ZrO ₂ (application Germany No. 4337916, C 04 B 35/64, 1995). The mass has the following grain composition: fractions 5-1 mm - 30-45%, fractions 1-0.09 mm - 15-30%, fractions <0.09 mm (finely divided component) - 30-40%.

The disadvantage of this invention is the low density and, therefore, high porosity. In addition, the production technology of such a refractory involves firing products at a temperature of 1700-1800 ° C, which greatly complicates its implementation.

The problem to which the invention is directed, is to reduce porosity and increase strength while maintaining heat resistance.

The problem is solved due to the fact that the finely divided component of the mass based on granular periclase filler contains, wt.%:

Periclase fraction less than 0.088 mm 79.0-98.7% Zirconia and / or zircon fractions less than 0,088 mm and / or Al ₂ O ₃ fractions less than 0,010 mm 1-20% Boric acid fractions less than 0.088 mm 0.3-1%

when the ratio of the components of the mass, wt.%:

periclase fraction 3-0 mm the foundation finely dispersed component 15-35% temporary binder (in excess of 100%) 3-7

It is known that the introduction of ZrO ₂ zirconia additive improves heat resistance due to the formation of a microcracked structure, the formation of which is caused by polymorphic transformations of zirconia crystals from a cubic modification to a monoclinic and vice versa. Polymorphic transformations of ZrO _{2 are} accompanied by a change in volume at temperature differences from 0 to 1600 ° C and the formation of microcracks. The addition of zircon to the magnesia masses increases the heat resistance due to forsterite neoplasms, while the porosity decreases and the strength of the refractory increases. The introduction of an additive of alumina increases the heat resistance of magnesian refractory as a result of the formation of aluminum-magnesian spinel, and since this process is accompanied by an increase in volume, the porosity decreases. The addition of boric acid improves the sintering of the refractory and thereby also helps to reduce the porosity of the refractory and increase the strength.

Thus, the joint or separate introduction of these additives into the composition of the finely dispersed component can reduce porosity and increase strength while maintaining, and in some cases, increasing heat resistance. The inventive refractory mass with the claimed ratio of components allows to obtain a refractory product with the necessary set of properties.

From the literature it is not known the use of the finely divided component of the proposed composition in combination with a granular filler in predetermined proportions.

For the manufacture of samples used fused periclase powder grade PPBS-95.5 according to TU 14-8-234-77 with changes No. 1-3 of fractions 3-0.5 mm, 2-05 mm, 0.5-0 mm and less than 0.088 mm, sintered Chinese periclase with MgO content - 96.5% of fractions 3-0.5 mm, 2-05 mm, 0.5-0 mm and less than 0.088 mm, TU 1762-003-001 86759-2000 grade baddeleyite concentrate -1, TU U 14-10-015-98 zircon concentrate, grade KCP, reactive alumina STS - 30 (Alcoa), boric acid according to GOST 9565-75, technical lignosulfonate according to TU 13-0281036-029-94, polyvinyl alcohol. All components of industrial production.

Masses were prepared in mixing runners. First, periclase fractions of 3-0.5 or 2-0.5 and 0.5-0 mm were loaded and mixed for 1-2 minutes. Then moistened with a solution of LST (density 1.22-1.24 g / cm ³ ) or a solution of polyvinyl alcohol (density 1.20-1.22 g / cm ³ ) and mixed for 3-5 minutes. Then the components of the finely divided component were added and mixed for another 5-7 minutes. The total mixing cycle is 15-20 minutes.

The compositions of the prepared refractory masses are presented in table 1, and the properties of samples made from these masses are shown in table 2.

The products were pressed on a hydraulic press at a pressure of 180 MPa. Further, the products were dried at 100-120 ° C, and then fired at a temperature of 1650 ° C. Samples were cut out from the obtained products and the properties were determined.

The determination of open porosity and apparent density was carried out according to GOST 2409-95. Determination of compressive strength according to GOST 4071.1-94. Determination of heat resistance was carried out according to GOST 7875-85 at a temperature of 1000 ° C followed by air cooling for 10 heat shifts. Due to the fact that for 10 heat shifts, cuts and cracks did not appear on the samples, the heat resistance was evaluated by the residual strength (loss of strength) during compression after this test.

According to the description of the prototype patent, the heat resistance of the samples was evaluated by changing the modulus of elasticity before and after the test for heat resistance. Due to the lack of a description of this method of determination, the prototype samples made were tested for compressive strength after 10 heat exchanges of 1000 ° C - air.

From table 2 it is seen that the proposed mass has a lower porosity and higher strength while maintaining high heat resistance.

The use of the proposed mass for the manufacture of refractories, in particular slabs for slide gates, will increase their durability and increase the service life, which will ensure failure-free operation of devices for casting liquid metal.

table 2 Composition, No. Open porosity,% The apparent density, g / cm ³ The limit of compressive strength, N / mm ² Heat resistance (10 heat exchange)
1000 ° C-air Appearance The compressive strength after 10 heat cycles, N / mm ² Strength reduction,%. 1 12,2 3.14 130 No cracks or cuts 110 fifteen 2 11.5 3.15 158 No cracks or cuts 163 - 3 14.5 3.05 95 No cracks or cuts 78 eighteen 4 12.6 3.10 110 No cracks or cuts 102 7 5 11.7 3.15 139 No cracks or cuts 142 - 6 10.7 3.16 128 No cracks or cuts 131 - analog 7.1 3.31 96 The formation of cuts after 3 heat changes thirty 69 prototype 16,4 2.94 85 No cracks or cuts 68 twenty

Claims (1)

The mass for the manufacture of basic refractory products based on periclase with a purity of at least 95% MgO, consisting of granular periclase, a finely dispersed component and a temporary binder, characterized in that it contains granular periclase of a fraction of 0-3 mm, and the finely divided component contains a periclase of a fraction of less than 0.088 mm and zirconia and / or zircon fractions less than 0.088 mm, and / or alumina-Al ₂ O ₃ fractions less than 0.010 mm and boric acid fractions less than 0.088 mm with a ratio of components, wt.%: Periclase fraction less than 0.088 mm 79.0-98.7 Zirconia and / or zircon fractions less than 0,088 mm, and / or Al ₂ O ₃ fractions less than 0.010 mm 1-20 Boric acid fraction less than 0.088 mm 0.3-1 the ratio of the components of the mass is, wt.%: Granular periclase fraction 0-3 mm The foundation Fine component 15-35 Temporary binder (over 100%) 3-7