Production of medium and low density chromium oxide refractories and their properties

Conclusions In order to obtain medium and low density chromium oxide products, it is necessary to conduct compaction using the optimum number of strokes (impacts) on the friction-press. In this case, the strength of the products is sufficiently high for transporting the blocks.We developed certain methods that ensure production of large-sized slotted blocks without deformation during the firing operation.We developed a firing regime for the chromium oxide products with carbon black addition which makes it possible to decrease the firing duration by approximately 2 times. Furthermore, a firing regime was developed for dense products that permits one to increase the product density and to decrease the fuel consumption.Translated from Ogneupory, No. 2, pp. 5–9, February, 1986.     

Firing technology for refractories made of sintered corundum

Conclusions A technology was developed for firing corundum refractories, which, when used with a batch containing densely sintered chamotte having a water absorption of up to 3%, 40–45% finely milled corundum (minus 60 m), and a fabrication pressure of 100 MPa, guaranteed the production of dense goods, and with the use of slightly sintered chamotte having a water absorption of up to 12% — high-density goods. With a reduction in the fabrication pressure of the green articles to 50 MPa the new technology ensures the production of densified goods.Translated from Ogneupory, No. 5, pp. 15–20, May, 1979.     

Firing roof refractories by setting products of a single grade

Conclusions A study was made of the firing process in a high-temperature tunnel kiln set with roof refractories of one and two grades. The firing loss when the products were placed in 3–4 rows (on edge) is slight but sharply increases in the two lower rows of the lattice setting using products of a single grade. The setting of the roof refractories over the height should consist of no more than four rows (on edge) which with a kiln channel height of 1.1 m is possible by using a setting of periclase-spinel refractories with an undersetting of chrome-magnesite products.The firing of the roof refractories should be done in a 7-column setting using products of two grades with a column thickness of 0.23 m and a length of 2.6 m.The possibility of using lattice settings in specialized kilns with a low channel height should be considered separately.Translated from Ogneupory, No. 1, pp. 11–19, January, 1971.     

Silicone polymers in oxide refractories technology

Conclusions We developed a method for obtaining silicone bonds for refractory materials based on nonhydrolyzed ethyl silicate, silicone resins, and organic adhesive component.Using corundum and periclase refractories as examples we demonstrated that use of the new bonds contributes to a significant strengthening of the materials in the range 20–900°C, and they are therefore prospective for preparing unfired refractories. The use of bond ensures densification and strengthening of corundum refractories, while simultaneously reducing the shrinkage, and leads to an increase in the stabilization of the high-temperature strength of the articles and a reduction in their wettability by molten steel. It is shown that the new oxide materials may be obtained in the production of tiles for the gate valves of steel-casting ladles.Translated from Ogneupory, No. 3, pp. 13–16, March, 1984.     

Preserving refractories containing free calcium oxide

Conclusions A method was developed for preserving refractories containing free calcium oxide, enabling us to store freshly pressed articles without altering their basic properties for 25–30 days. In this case the maximum storage period of the heat-treated goods is not less than 3 months.The new method means that interfactory deliveries can be made to the newly built converter departments.Translated from Ogneupory, No. 3, pp. 8–11, March, 1981.     

Reaction between zinc oxide and chamotte refractories

Conclusions As a result of chemical reaction between chamotte and zinc oxide, zinc aluminate ZnAl₂O₄ and zinc silicate Zn₂SiO₄ are formed.The mullite is not chemically resistant under the action of zinc oxide. Even at 900°C mullite reacts with zinc oxide, forming ZnAl₂O₄ and SiO₂.In accordance with the quantity of melt formed in the refractory under the action of zinc oxide, high-alumina products should be more resistant to the action of vapors and oxides of zinc at elevated temperatures than chamotte and semiacid refractories.Translated from Ogneupory, No. 7, pp. 36–39, July, 1971.     

Dense magnesium oxide refractories with increased spalling resistance

Conclusions A production process of magnesium oxide spinel-bound plates with a porosity of 1 to 3%, high spalling resistance and considerable life span at high temperatures was developed.The production process is distinguished by the application of dead-burned finely-milled magnesium oxide, the introduction of highly dispersed -AI₂O₃, compression of green compacts from pseudogranular mixtures, slow drying accompanied by uniform air circulation and two-stage firing at 1450 and 1750° C in powder-covered capsules.     

Producing chromium carbide using reduction of chromium oxide with methane

In the present work, reduction of chromium oxide using methane is investigated. The thermogravimetric method was used to obtain kinetic parameters of the reaction in the temperature range of 870-975°C under atmospheric pressure. The experimental data was analyzed using the grain model. The reaction product, chromium carbide, was observed to be produced at a temperature of about 140°C lower than by other conventional methods. Carbon deposition, which is highly undesirable in the synthesis of chromium carbide, was negligible in the present experiments. The experiments were conducted in two modes, either under the conditions of reaction control or under the conditions of diffusion control for determining reaction rate constants and diffusion rates to study pore diffusion, respectively. The pore diffusion studies were carried out with and without considering the bulk flow effect. The gas phase diffusion coefficient through the product layer around the grains was calculated with an approximate method. © 2005 American Institute of Chemical Engineers AIChE J, 2006