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Examination of desulfurization behaviour of ladle furnace slags of a low-sulfur steel

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2007
Keskinkılıç, Ender
The aim of this research was mainly to investigate desulfurization behaviour of ladle furnace slags of a low-sulfur steel. First, the change of the amount of unstable oxides (FetO and MnO) in slags was studied from the converter till the end of ladle furnace treatment for different steel quality groups. It was found that the change in the amount of unstable oxides could be examined best with low-C steel qualities. Then, the change of activity of iron oxide was investigated for a member of low-C steel quality group, namely 4937K, a low-S steel. The relation between the degree of desulfurization at the ladle furnace, % DeS (measured), and the change in activity of iron oxide, % Decrease in aFetO, was examined first using an empirical expression obtained from literature. Then, this relationship was studied using steel oxygen activity measurements conducted at the ladle furnace. With this method, a regression formula was proposed for 4937K slags relating activity coefficient of iron oxide, gama(FetO), with the major slag components. The results obtained from steel oxygen activities were found to be representative for 4937K steel-slag system showing similar behaviour with the ones from the empirical expression obtained from literature. Similar results were found using Temkin equation and the polymeric anion model. In relation to formation of less harmful inclusions to suppress adverse effects of sulfur, morphological studies of some steels produced in ERDEMİR plant were performed. D-type globular inclusions with severity values of 1-2 were observed.