Effect of carbon and silicon carbide on the properties of carboxylated refractories

Abstract

The interrelation between the content of carbon and silicon carbide and the properties of carboxylated refractories (porosity, mechanical strength, heat resistance, resistance to the action of blast-furnace slag) is studied. Dependences of the properties of carboxylated refractories on their material composition are plotted.The quality of steel in metallurgy is often improved by treating cast iron, i.e., desulfurization, dephosphorization, and desiliconization, which are performed in mixers, casting ladles, and oxygen-blown vessels [1]. The functional layers of the linings of this equipment are primarily made of refractories based in the Al 2 O 3 -SiC-C system, which have replaced the earlier used high-alumina refractories and increased substantially the service life of the linings [2, pp. 248 -259]. Refractories with Al 2 O 3 -SiC-C composition are not roasted and are produced with the use of high-alumina raw materials (bauxite, corundum of different quality), silicon carbide, graphite, and tar with addition of functional additives [3].In order to improve the parameters of the properties carboxylated refractories are enriched with carbon. Carbon decreases the penetration of slag into refractories, which is associated with its low wetting with slag and the capacity to reduce iron oxides in the slag, which raises the viscosity and the melting temperature of the latter [4]. Carbon is usually introduced into the refractory in the form of graphite and tar. It is assumed that the gaseous products of carbon oxidation (CO and CO 2 ) in a carboxylated refractory fill the pores and create backpressure that hinders the penetration of slag. Growth in the carbon content is accompanied by increase in the slag resistance of carboxylated refractories [5]. The content of carbon in the refractories and its protection from burning are determined by the production parameters of the refractories and the service conditions in linings of metallurgical equipment.In the course of the study the carbon content was varied from 4 to 8 wt.% by changing the amount of introduced graphite at a constant amount of tar. The content of silicon carbide was varied within 10 -14 wt.%. The components were introduced into the composition of the finely milled part of the charge. The time of vibromixing was 25 min. The mixture prepared left no remainder on a sieve with a cell size of 0.063 mm. We used high-quality components of domestic and foreign producers. The plasticizer was a composition with a high residual carbon content, which had been developed by the department of chemical technology of high-temperature materials. The mixtures were prepared in a tempering mill with maximum charge of 6 kg; the preparation time was 20 -25 min. The tests were performed for molded cubic specimens with an edge of 50 mm, which had been heat treated preliminarily at 300 ºC with 15-h hold. The results of the tests were plotted in the form of linear dependences on the domains of designed compositions for 9 points using the MS Excel 2003 medium.The ultimate compressive s...

Increase in the Slag Resistance of Refractories Based on the Al₂O₃-SiC-SiO₂ System

“…There is a known [18,19] type of refractories with a carbon-bound silicon oxide carbide system. When producing special steels for ladle lining, alumina-carborundum and fire clay -carborundum products are used.…”