RU1794072C - Charge for refractory materials preparation - Google Patents

Abstract

The invention relates to the refractory industry, in particular to the manufacture of refractories for the lining of mobile cast iron mixers. The inventive charge contains components in the following ratio, wt.%: Fused corundum fraction 2 mm 25-40; fused mullite fraction 3 mm 15-35; calcined alumina 25-36; silica sand 9-15. Shrinkage during firing in the range of 1650-1750 ° C is 0.1-0.9%, the total porosity is 16.3-18.6%, the compressive strength is 126-169 N / mm2, and the heat resistance is 1300 ° C; C - water 6-12 heat exchange. 1 tab.

Description

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The invention relates to a refractory subindustry, and in particular to the production of refractories used in linings, high temperature metallurgical units; mobile cast-iron mixers, heating and shaft furnaces, melting crucibles, etc.

One of the main requirements in the manufacture of refractories, especially those used in contact with metals and slag, is their volume constancy during firing, since the presence of temperature fluctuations in the volume of the charge leads to significant deviations of the products in size, which subsequently does not allow high-quality performance masonry of thermal units. In addition, refractories used in cast iron mixers should

to have a high softening onset temperature under load, good slag resistance and considerable resistance to temperature fluctuations (heat resistance).

A known mixture for the manufacture of refractories based on alumina raw materials with AlaOs content of more than 95 wt.% For example alumina, or a mixture thereof with a material containing more than 50 wt.% AlaOa and with the addition of 2-15 wt.% High-siliceous material containing 75- 95 wt.% SiOa.

The disadvantage of the products made from the proposed charge is the low temperature of the onset of softening under a load of 0.2 N / mm2 1630 ° C, which does not allow to achieve high resistance of refractories in service.

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with

Another known mixture contains calcined alumina fractions of less than 10 microns in an amount of 43-70%, quartz sand fractions of less than 0.5 mm in an amount of 17-28% and an aluminosilicate component (chamotte kaolin or mullite or mullite-corundum fractions less than 3 mm ) in an amount of 2-40%.

The mixture using mullitocorundum chamotte makes it possible to obtain products with an AlaO3 content of 72-74.6%, a softening start temperature under a load of 0.2 N / mm2 1750 ° C, and low open porosity of 11.2-16.0 % and high mechanical strength 131-154 N / mm2.

However, products from this charge have significant shrinkage during firing, which does not allow to obtain products with sufficiently accurate dimensions. In addition, these refractories have low thermal stability (I heat transfer) and insufficient slag resistance due to the high content of silica sand in the charge.

The technical solution closest to this is a mixture comprising 35-50 wt.% Corundum, 15-30% fused mullite 20-30% alumina, 5-15% zirconium silicate. The material obtained from the known mixture has significant shrinkage and relatively low strength.

The aim of the invention is to reduce shrinkage and increase strength.

To achieve this goal, the mixture for the manufacture of refractories has the following composition, wt.%:

Fused corundum

fractions less than 2 mm 25-40

Fused mullite

fractions less than 3 mm 15-35

Alumina calcined 25-36

Quartz Forest 9-15

Firing of products from this mixture should be carried out at temperatures in the range of

The mixture for the manufacture of refractories, including fused corundum and mullite, alumina and an additive containing silicon oxide, characterized in that, in order to reduce shrinkage and increase strength, it contains fused components of the fractions, respectively, less than 2 mm and

Lah 1650-1750 ° C. During firing, quartz sand melts and interacts with alumina and other charge components with the formation of short-prismatic crystals of secondary mullite, which, due to strong bonds with mullite and corundum, increases all of the above indicators.

In order to obtain samples of refractories, a series of blends were prepared according to the proposed and known compositions.

Pre-produced a mass dosage of the starting components of the charge.

In the preparation of the charges used fused corundum and fused mullite

5 fractions of less than 3, 2, 1 and 0.5 mm with different ratios in the mixture, as well as different ratios of the components of the mixture in order to determine the optimal material and grain compositions. Granular constituent charges - fused corundum and

0 mullite and quartz sand were moistened with an aqueous solution of lignosulfonate (LBF) with a density of 1.15 g / cm3 and mixed thoroughly. Then, finely ground calcined alumina was introduced and mixed until a homogeneous mass was obtained. Samples

5 was made by pressing on a hydraulic press at a specific pressing pressure of 70 N / mm and calcined in a chamber furnace at a temperature of 1700 ° C with holding at a final temperature of 6 hours.

0 The composition of the mixture and the properties of the samples are shown in the table. As can be seen from the table, the volumetric shrinkage according to the proposed composition is insignificant and ranges from 0.1 to 0.9% versus 5.3% for samples from a known charge, mechanical strength 126-169 N / mm and porosity 16.3-18 , 6%.

less than 3 mm, and as an additive - quartz sand, in the following ratio of components, wt.%; Fused corundum fractions less than 2 mm 25-40 Fused mullite fractions less than 3 mm 15-35 Alumina 25-36 Quartz sand 9-15

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