SE419637B - DRY, ELFFAST CEMENT FOR THE FORM OF FOGLOSA INFO - Google Patents

Description

_ ~ 790l | 659 ~ 5 10 15 2 particle diameter of 10, am or less, preferably S / fm or less.

Refractory grains of alumina, magnesium oxide, magnesium oxide-chromium oxide and spinel are preferred. Mixtures of these materials can be used. When melted spinel grains (MgO 2 Al 2 O 3) are used, it is profitable to mix in reactive fine ore of alumina and magnesium oxide, which. on the spot gives spinel when burning, known in the prior art, which helps to make the lining tight. The aluminum used in the melting furnace (or in a previous heating) is oxidized to gamma alumina and increases in volume. This results in a reduced porosity and it is also assumed that the combustion heat of the metal helps in the sintering.

In each case, the liners formed from mixtures according to the invention have a longer service life and lower porosity than those formed from mixtures without aluminum powder. The maximum amount of aluminum powder which can be used according to the invention is determined by the pore volume of the cement and how much aluminum expands when it is oxidized. For alumina mixtures, about 10% is the maximum permissible percentage by weight and in general 15% by volume is the upper limit.

The most useful refractory grains for lining metal melting furnaces, according to the invention, are alumina, magnesium oxide, magnesium oxide-chromium oxide, magnesium oxide-alumina spinel and alumina-chromium oxide. Generally less useful are feedstocks of silica, silicon carbide, muilite, zirconium and zirconia. g.

The following non-limiting examples preferably have the following composition (all percentages indicate% by weight): molten alumina, 1.2 - 4.8 mm 38% molten alumina, 44 m - 1.2 mm 25% molten alumina coated with 4 wt. -% glass (anna: us Patent p.79s.o4o), where the coated particles have a size of between 0 0, 16 and 0.7 mm 20% crude cyanite, 0.076 - 0.089 mm 20% aluminum powder, 0.076 mm 5% silicon carbide powder , 0.076 mm 5% metal powder of aluminum, 4.5 .mu.m diameter 3% boric acid 1% To characterize and investigate some of its properties, the above substances were mixed together into a lining in a metal melting furnace and parts of the lining were examined. The cement formed under heat had a porosi- a 7904659-5 3 ._. S. ._. ,. .. _ _ the density (volume of the open pores) of 17% and an average density of 3,2 g / cm3.

Without the addition of aluminum, the cement after molding in the metal melting furnace had a porosity of 20% and a density of 3.0 g / cm 3.

The cement, containing aluminum powder, was tested in a seedless smelting furnace for recycled steel. Previously, no cement, both those based on silica, zirconium, magnesium oxide and alumina, had been durable in this environment for more than a week. All became unusable due to severe erosion, metal penetration.

Below is an example of a spinel mixture: 10 molten spinel, 4, mm and finer 86% molten Mg0, 0, 15 mm and finer 4% molten Al 2 O 3, 0.076 mm and finer 4% fine-grained calcined Bayer alumina A 2% aluminum powder, 4.5 nun 3% l5 boric acid, finely divided l% The following is an example of molten Mg0 mixture: molten Mg0, 0.165 mm - 3.4 mm 63% molten Mg0, 0.15 mm and finer l7% molten MgO, 0.076 mm and finer l5 % 20 molten alumina, 0.076 mm and finer 2% aluminum powder, 4 .mu.m and finer 3% boric acid (finely divided) 0.5% As shown in the above example, a low temperature flux may be present in as small an amount as 1/2 weight. % normally more than 5% of such a flux is never used and alternatively the low temperature flux can be completely ruled out, see below.

An example of the manufacture and treatment of a mixture without any low temperature flux is given below.

Composition: 30 Material Size Weight -% Al2 O3 unit 94.5% purity 3.4 mm 0Ch finer 60 Al2O3 unit 99.5% purity 0; 70 mm 0Ch fi fl äše 30 Al203, finely ground 99.8% purity 0.076 mm 0Ch finer 4 SiO2 unit 99.0% purity 0-15 mm AND finer 3 35 Aluminum powder 4; Lm Treatment: Installation - Vibrate on site with molds _ Burning schedule - l. Raise the temperature to 204 ° C, at 38 ° C per hour. 2. Keep the temperature at 20400 for 1 hour 7904659-s 4 3. Raise the temperature to 53808, at 15006 per hour 4. HâH the temperature at 538 ° C for 1 hour

Claims (3)

A dry, refractory cement for forming seamless linings, packed or vibrated in place in a metal melting furnace, the cement comprising coarse, medium and fine particles of a crystalline alumina refractory material, alumina-chromium oxide, zirconia, spinel, silica, silica, magnesium oxide-chromium oxide, zirconium, mullite. magnesium oxide or mixtures thereof; up to 5% a low temperature flux; and fine-grained aluminum, characterized in that the aluminum particles have a particle size of 10 or less and are sufficiently atomized to be oxidized to alumina in place while the melting furnace is in operation, the aluminum metal being present in such a small amount that no electrical current passage occurs. through the packed, refractory mixture and that the pores of the packed mixture are not completely filled, when aluminum is oxidized to alumina, and is present in an amount of at least 1% by volume and not more than 15% by volume, of the total mixture of solids . Cement according to claim 1, characterized by at least one flux, which consists of glass, clay or boric acid in an amount of up to 5% by weight. Cement according to claim 1, characterized in that the crystalline refractory material is alumina, magnesium oxide or spinel. SUMMARY A A solid, packaged compound for lining metal measuring containers containing sorted, solid grains of a size chosen to minimize porosity and the amount of sintering and lubricating agent, - 15 vo1yms-%.