Determination and Prediction of Water Vapor Solubilities in CaO-MgO-SiO 2 Slags
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I.
INTRODUCTION
F R O M a steelmaker's viewpoint, hydrogen at very low concentrations can have very serious implications with respect to the mechanical properties of the finished steel product Ladle steelmaking techniques, recently employed in the production of high quality steels with low oxygen and sulfur levels, have renewed interest in the interactions of hydrogen with molten steel and slags. From a fundamental viewpoint, the dissolution of water vapor in molten slags, as a physico-chemical phenomenon, can provide a source of information pertaining to the structure and behavior of polyionic melts. Two research groups ~z have previously studied dissolution of water vapor in molten CaO-MgO-SiO2 slags. A comparison of the results from these two investigations indicates that there is a discrepancy with respect to the effect of magnesia on the solubility of water vapor in these slags. Specifically, while Zuliani et al. 1 3 reported that the replacement of hme by magnesia had a negligible effect, Iguchi and Fuwa, z who conducted a greater number of experiments with acidic sIags, found that, at a given basicity, the water vapor solubility mcreased with increasing magnesia content. The aim of this study was to resolve this ambiguity concerning the effect of magnesia. An additional objective was to obtain further information on factors influencing the dissolution of water vapor in metallurgical slags.
II.
EXPERIMENTAL PROCEDURE
Details of the present experimental procedure are briefly described below. More comprehensive details of this technique, including correction factors for the effect of different gas densities on the actual weight change measurements, have been reported elsewhere.~ 3 D.J SOSINSKY, Graduate Student, and A McLEAN, AISI Distinguished Professor, are with the Department of Metallurgy and Materials Science, Um'~erslty of Toronto, Toronto, ON M5S IA4, Canada M MAEDA, formerly Postdoctorate Fellow in Metallurgy and Materials Science, Umverslty of Toronto, is now Assistant Professor in the Institute of Industrial Science, University of Tokyo, 22-1, Roppongi 7 Chome. Mmato-ku, Tokyo, 106, Japan Manuscript submttted March 2, 1984 METALLURGICAL TRANSACTIONS B
Approximately twenty-five grams of prefused slag, contained in a platinum crucible and prepared from ultrahigh purity chemicals with less than 15 ppm total metallic impurities, are suspended from the electrobalance by means of a platinum chain. The slag is fused and held under purified, dry argon until a stable weight is recorded. An Ar/H~O gas mixture of controlled water vapor partial pressure is admitted into the reaction chamber and the change in sample weight continuously recorded on a strip chart. From preliminary experiments, it was determined that periods ranging from 12 to 24 hours were reqmred, depending on slag composition, to obtain equilibrium between the gas and slag phases. After saturation is obtained, dry argon is readmitted to the reaction chamber and water vapor then desorbs from the slag back to the gas phase. This experimental t
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