ANALYSIS OF CAST IRON QUALITY PULSATIONS IN THE BLAST-FURNACE PROCESS

Abstract

The frequency and velocity of fluctuations of physical and chemical properties of cast iron at three blast furnaces are studied, the furnaces worked with the use of the same raw material conditions with the injection of pulverized coal fuel up to150 kg/ ton of pig iron. Only at one furnace the frequency of occurrence of highs on the curve of changes in the content of sulfur in iron has been found, which indicates the possibility of formation and destruction of the skull in accordance with known dependencies in the mode of self-oscillation. At two other furnaces there was an aperiodicity of sharp changes in the quality of cast iron, depending on external factors. The results of earlier studies and the data of the presented work allow us to state the appropriateness of predicting extreme emissions of sulfur in the cast iron at separate furnaces to provide the rhythmic operation of the pig iron at ladle refining installation.It is usually believed that there is a close direct connection between the temperature of the iron and the silicon content in it - the higher the temperature of the metal, the more it contains silicon. The periods of the furnace operation are considered when the trends in the change of physical and chemical heating of the iron coincide and when they have the opposite direction. In the second case, the increase in temperature of iron is due to the weakening of endothermic direct silica recovery.It is shown that the extreme emission of sulfur in iron, which is considered to be a sign of changing of skull state in the furnace, corresponds to other signs - a sharp transition from the molted to acidic slags, the maximum release of alkaline compounds with slag, in particular K2O, synchronous change in the basicity of slag with changes in alkaline content but in opposite directions. That is, the negative effect of the scull slipping in the blast furnace process is partially offset by the removal of alkalis from the working space of the furnace. In contrast to the widespread view, it was found that both the reduced basicity of slag and its high temperature influence the intense output of alkaline compounds.