SU730661A1 - Refractory mass - Google Patents

Description

one

The invention relates to the composition of high alumina refractory masses on a spinel bond and can be used in metallurgy as a lining of furnaces and making crucibles for melting metals.

Refractory materials containing chromo-magnesia spinel are widely used in metallurgy due to their high performance properties. The introduction of the chromium-containing component into the refractory material can be carried out both in the form of compounds Cg (III) and in the form of compounds Cg (1). No: the use of Cr ()) compounds is more promising since it allows one to simplify the process of manufacturing a refractory product and improve its quality.

The use of hexavalent chromium compounds as a binder makes it possible to obtain refractory products with high strength up to 18OO kg / cm

and heat resistance 2O-50 heat changes 8OO ° С - water.

The disadvantages of these materials are the effective ingot porosity (up to 2%) and the high firing temperature -1-

It is known to introduce, in addition to chromium compounds, boron compounds, which increases the temperature resistance of the products and avoids IR softening during

10 roasting in the range of 6OO-900 C, and also increases the rate of spinel formation 2.

The closest technical solution to this is refractory

15 weight, weight %: corundum 8299, magnesium oxide 0.4-10, chromium compounds 0.5-5 and boron compounds 0.1-3 per L.

The disadvantages of the well-known corundum-20 spinel mass are high calcination temperatures of 1 70 ° C, a significant amount of open sparkling, 16.5-21%, low mechanical strength of the products (the compressive strength is 700, 1000 kgf / cm), as well as reduced temperature of the onset of deformation under the NAT MANUAL.

The latter is due to the presence in the composition of the mass of boron compounds forming the glass phase with a low temperature of the onset of softening, which leads to a decrease in the deformation temperature of refractories under load on lOO-lSO C compared to igneous materials not containing boron compounds.

The circuit of the invention is a decrease in the firing temperature, porosity, increase in strength and temperature of the onset of deformation of products under load.

This goal is achieved in that in a refractory mass, including corundum or alumina, magnesium oxide and a chemical binder, containing a water-soluble chromium compound and an additive, the binder as an additive is 12-38 wt. Sol of silicic acid in terms of SiO / i with a ratio of components, weight. Magnesium oxide 4-IO

Chemical Binding of 1O-2O Corundum or Alumina Else A range of silica sol concentrations is selected on the basis of the following considerations. When the content of O.j in connection is less than 12 weights. %, in order to achieve the indicated value of the open porosity, it is necessary to raise the firing temperature to 1650 ° C, and if the content of 02 is in relation to more than 38 V, eu. % deformation temperature of products under load of 2 kg decreases to 1680-17OOs.

The mass is prepared by mixing the dry components followed by the addition of the complex binder with thorough mixing. O2 concentration. in the ash of silicic acid 5-30%. The more diluted sol is low-tech, and concentrated solutions of silica sol instability) and are prone to gelation, and therefore can only be used within a few hours after their preparation.

The chromium-containing component can be introduced into the composition of the mass, either as a dry water-soluble compound, transferred to # when the dry mixture is moistened with a sol of silicic acid, or as a solution in water or ashes. If necessary, the humidity of the mass before

making products is adjusted by adding water or drying it to the required level.

The masses of the proposed composition are used to form products by pressing (humidity 3-5%), as ramming mass (humidity 7-1О%) or in the form of refractory concrete (humidity 12-16%). The molded articles are dried at 9 ° –120 ° C and burned at 1450–50 ° C, raising the temperature at a rate of 12 ° –150 ° C / h.

Example 1. A mixture of composition, wt. %: corundum 87, magnesium oxide 0.5, anhydrous magnesium chromate 12.5 is moistened with a 12.1% solution of silica sol at the rate of 100 g of solution per 1 kg of the dry mixture and thoroughly mixed.

In terms of dry ingredients, the mixture has the following composition, you. % Corundum86

Magnesium oxide as MgO +

+ MgSgOd4

Chromic anhydride8, 8 Silica dioxide 1.2 Weight after mixing, dried to a moisture content of 3-5%, pressed out under a pressure of 800 kgf / cm and burned, raising the temperature from a speed of 15 O deg / h to.

Product properties are listed in the table.

Example 2. To a mixture of composition, wt. %: alumina G 00 75.7, fine ground calcined magnesite Yu, 8, technical chromic anhydride 12.5 added 2 7% sol of silicic acid in the amount of ZOO g solution sol per 1 kg of dry mass.

The composition of the mixture in terms of dry ingredients, wt. %:

Alumina7O

Magnesia oxide 10

Chromic anhydride12.5

Silicon dioxide 7.5

Example 3. To a mixture of 96O g of ground alumina G-OO and 60 g of magnesium oxide, 2OO g of an 18% solution of a sol of silicic acid are poured in which 144 g of chromic anhydride is dissolved before mixing. In terms of dry ingredients, the mixture has the following composition, weight. %:

Alumina80

Magnesia 5

Chromic anhydride12

Cracid Dioxide 3

The mixture is thoroughly mixed in the mixer, dried to moisture.

7306С1

3-5% and pressed products under pressure KOOP / kg.

Pressed products are burned at 145 ° C,

Properties of products pr) gvedek in ta6nifce.

PrevfaeMbie

 Pressing,

P 600krc / cMl500 1300-1500 9-11

Claims (1)

1. USSR author's certificate3. USSR author's certificate Me 565021, cl. C O4 B 35 / 1O, 1974. 5 No. 5О3835, cl. From 04 To 35/10, 1975. refractories. M., Metallurgists, 1977.