Distribution Behavior of Chromium, Vanadium and Titanium in Molten Pig Iron by CaO-SiO2(-CaF2) Slag

Abstract

In recent year, the use of low-grade raw materials (ore, cokes etc.) has been increasing in the blast furnace in order to save the cost. It caused the increase of the contents of tramp elements (Cr, V and Ti etc.) in the molten iron. The increase of residual elements in the molten iron causes a lot of loads on the steelmaking process, especially on the converter. For this reason, it is necessary to study the distribution behavior of chromium, vanadium and titanium in molten iron for cost and quality. In order to investigate the distribution ratio of chromium, vanadium and titanium in the molten iron, a series of experiments were conducted. A graphite crucible with Si-containing carbon saturated iron and synthetic slag was put into the resistance furnace at a temperature of 1573K to 1673K in CO gas atmosphere (PO2=10-17) for a period of time. After the equilibrium was reached, melts and slag were quenched in the water, and the content of chromium, vanadium and titanium in both phases was analyzed respectively by inductively coupled plasma optical emission spectrometer (ICP-OES). Distribution ratio of chromium, vanadium and titanium was analyzed, and role of slag basicity, reaction temperature were examined. The results obtained in the present work are as follow. The increase of the slag basicity decreased the chromium, vanadium and titanium distribution ratio due to the increase of the activity coefficient of each oxide. However, the chromium and vanadium distribution ratio were very low. The chromium distribution ratio was inversely related to the temperature, which was dependent on the temperature, but there was no effect of temperature on vanadium distribution ratio. In case of the titanium, the distribution ratio of titanium shows a tendency to decrease with increasing temperature at slag basicity of one, while there was no effect of temperature at slag basicity of 1.3 or more. It was thermodynamically proved that the chromium and vanadium distribution reactions were an exothermic reaction and lower basicity was more suitable to leave chromium and vanadium in slag. However titanium distribution reaction was not clear.