EFFECT OF BASICITY ON COMPLEX METALLURGICAL PROPERTIES OF SINTER

Abstract

Metallurgical properties of sinter have a significant influence on its basicity. The dependence of cold and hot strength, softening point, reducibility and other physical and chemical properties of sinter on basicity was established by studies of many domestic and foreign scientists. However, taking into account essential increase of iron content in concentrate during decrease in silica content as a result of modernization of production in JSC Stoilensky GOK, the estimation of basicity influence on complex properties of sinter produced with the silica usage is actual. The results of laboratory research at Novolipetsk Iron and Steel Works with the purpose of study of sinter basicity influence on sintering process indexes, strength and high-temperature properties, including filterability of smelting products through the coke baffle are presented. The sinters of different basicity were produced in the laboratory conditions by sintering based on concentrate of Stoilensky GOK with iron content 68,0 %. The basicity of the charge CaO/SiO2 was varied in the range of 1.2‒2.0 units in steps of 0.2 units. In the process of research we selected the optimum rate of solid fuel for each charge from the condition of maximum vertical speed of sintering and sintering strength of sinter. It was found that increasing the basicity of sintering material leads to increasing cold and hot strength, narrowing interval of plastic-viscous state. The maximum vertical sintering rate and maximum specific capacity are reached at basicity 1.6. At basicity of 1.4 the minimum strength of sinter was obtained. It was established, that the sinter reducibility sharply increases at basicity of 1.6 units. With increase in basicity the temperature softening-melting interval (TSMI) of sinter decreases, which characterizes the cohesion zone. The widest TSMI is in sinter with basicity of 1.2, the narrowest – with basicity of 2.0. With increasing basicity of sinter the characteristics of the melt flow through the coke packing increases. The mixture of 55% of sinter with 2.0 basicity and 45% of unfluxed pellets from Stoilensky GOK had the best flow characteristics of the melt products and slag.