SU1742261A1 - Refractory mass for teeming metals - Google Patents

Abstract

This invention relates to the manufacture of carbide-containing refractories for casting metals. The composition can be used for the manufacture of ceramic elements of the spinning units of amorphous and microcrystalline ribbons. The refractory mass contains, in wt.%: Phosphate bond 3. 10; silicon carbide M4,5 - 42,0; corundum 10-25; granular fused quartz fraction of 3 mm 27 - 37; sulfide alcohol bard 0.5 - 1.0; clay refractory - the rest. The refractory mass was prepared as follows. Runners were loaded into silicon carbide and fused quartz, moistened with a phosphate binder and a slip with the addition of PRS, a mixture of clay and corundum was injected and the mass was treated for 10 minutes. The refractory porosity is 14, 2 - 16.9%, compressive strength 88 - 127 MPa, thermal expansion coefficient 3.52 - 4.54 -106 degrees 1. Thermal resistance - more than 10 thermal cycles. 2 tab. sl C

Description

The invention relates to the manufacture of refractory products for casting metals, in particular in the preparation of strips from amorphous or microcrystalline alloys.

A mortar from crystalline quartzites, clay, and an aluminum-chromophosphate binder with the addition of silicon carbide is known.

The presence of crystalline quartzite in the composition of the dead does not allow to obtain heat-resistant products with a low linear expansion coefficient from such a mass. The bond is not enriched in corundum.

Closest to the invention is a composition of refractory materials, containing, in wt%: phosphate binder 12-18; electrocorundum 5 - 20; plasticizer 6 - 10; fine ground mullite 10 - 30; silicon carbide - the rest.

The disadvantage of refractories of this composition is relatively low heat resistance, density and strength of products, a high coefficient of thermal expansion, which limits the possibility of its use as structural materials at high temperatures.

The aim of the invention is to increase the compressive strength, heat resistance and decrease in porosity and thermal expansion coefficient.

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This goal is achieved by the fact that the composition contains additionally granular fused quartz and PRS in the following ratio of initial components, in May.%: Phosphate bond 3-10; silicon carbide 14.5 - 42.0; corundum 10 - 35; granular fused quartz fraction of 3 mm 27 37; sulfite-alcohol bard (PRS) 0.5 - .1.0; refractory clay - the rest.

The concentration ranges of the components in the mixture are chosen from the following considerations: an increase in the silicon carbide content above 42% leads to the need to reduce the silicon carbide content, above 42% leads to the need to reduce the ceramic bond (clay + corundum) content, less than 20% or fused silica less than 27 % leads to a sharp decrease in the density and strength of the refractory and its heat resistance, i.e. main quality indicators of refractories for metal casting /

Reducing the content of silicon carbide less than 14.5% reduces their density characteristics. Increasing the content of the ceramic binder (clay + corundum) more than 45 leads to increased shrinkage of the mass, and also because of the increased clay content and, accordingly, the glass phase, to a decrease in the thermal properties and heat resistance of the refractory,

Reducing the content of the phosphate bond and the PRS of less than 3.5% is inefficient and does not allow to obtain high-strength products in unburned form. Compositions containing more than 11% of the phosphate bond and PRS swell in the firing process, thereby deteriorating all the quality indicators.

The improvement in the quality indicators of the proposed refractory in comparison with the properties of the known refractory is due to the introduction of melted quartz in an amount of 27–37% in combination with silicon carbide and a high alumina-phosphate bond with the addition of 0.5–1% of PRS. Increasing the density and strength of products contributes to the introduction of granular fused quartz into their composition, which, when pressed in combination with hard materials such as silicon carbide and corundum, is intensively crushed. A structure is formed that approximates the optimal grain composition. This structure, where the granular part is represented by silicon carbide and fused silica, and the high-alumina composition of clay, corundum, PRS and phosphate binder is less susceptible to thermal expansion and more heat-resistant. The introduction of the PRS improves the compressibility of the mass and, accordingly, the quality of the products.

The effect is achieved only at the specified content of fused quartz. Reducing it below 27% or increasing above 37% is accompanied by a deterioration in the whole range of properties.

The use of fused quartz and PRS in the compositions of ceramic materials is well known, but the use of such a complex composition and structure of a substance combining silicon carbide, fused quartz, corundum, clay, phosphate binder and PRS in a complex that provides such

5 are the most important properties for metal casting, such as high density, strength, heat resistance and low thermal expansion coefficient. These properties are due to the introduction of a phosphate binder into the PRS composition and a special granulometric structure, as well as the formation of aluminum, silico-, and kaolin-phosphate cords with corundum, quartz, and clay at relatively low temperatures. With

At high temperatures, partial decomposition of silicon carbide leads to the formation of active silicon dioxide, which binds silicon carbide and fused silica grains, and also reacts with a high-alumina bond, forming mullite intergrowths.

PRI me R. The following materials are used as raw materials for the preparation of samples: silicon carbide of a fraction of 0.2–0.1 mm, corundum of a fraction less than 0.063 mm, fused quartz of a fraction of 3–0 mm, clay refractory DN-1, concentrate of PRS, mullite fraction less than 0 08 mm.

The phosphate binder used is: phosphoric acid (1.6 g / cm3 density) and an aluminum-chromophosphate binder (1.55 g / cm density).

Mixing and moistening the experimental mass produced in laboratory mixing

5 runners in the following order: loading of filler (silicon carbide + fused quartz), wetting with orthophosphoric acid and slip with the addition of PRS, the introduction of a mixture of clay and corundum and treatment of the mass

0 for 10 min. Humidity mass in the range of 3-6%.

Samples are pressed on a laboratory hydraulic press at a specific pressure of 50 MPa. Dry the samples at 120 ° C to

5 residual moisture is not more than 1%, followed by heat treatment in an electric furnace at 520 ° C with an exposure at a final temperature of 4 hours. Part of the samples from each of the compositions are calcined at 1400 ° C in charging with 4 hours exposure.

According to this technology, samples of three compositions were made using orthophosphoric acid (compounds 1–3) and three compositions using as a phosphate bond, an aluminum-chromophosphate bond (compounds 4–6), as well as four masses with beyond the ranges of the proposed limits: two (7 and 8) for the masses with phosphoric acid and two (9 and 10) for the masses with an alumina-phosphate binder.

The compositions of the masses and the properties of the samples of them are given in table. 1 and 2.

The tests were carried out according to the same procedure on the same number of samples (average of three definitions).

The open porosity, compressive strength, thermal stability and thermal expansion coefficient are determined.

As a result of comparative tests, it was established that the samples of the proposed composition (1-6) differ from the known samples (11) by higher indicators of compressive strength by 1.5 - 1.8 times and heat resistance, as well as by a lesser 1.5 - 1.8 times the porosity and thermal expansion coefficient is 1.5-1.7 times less. The specified advantages are fair both at an unburned variant of technology, and after roasting at 1400 ° С. Going beyond the range of the proposed limits of the components causes a deterioration in the quality indicators of the samples.

Claims (1)

Claims Refractory mass for casting metals, including phosphate bond, silicon carbide, corundum, refractory clay, characterized in that, in order to increase the compressive strength and heat resistance, reduce porosity and thermal expansion coefficient, it contains additionally granular fused quartz fractions: S 3 mm and sulphite-alcohol bard in the following ratio of components, wt.%: phosphate bond 3 - 10; silicon carbide 14.5 - 42.0; corundum 10-25; granular fused quartz fraction of 3 mm 27-37; sulfite alcohol bard 0.5 - 1.0; refractory clay - the rest. Table  Out of range of suggested limits. Continuation of table 1 table 2