Aluminum Deoxidation Equilibria in Liquid Iron: Part I. Experimental

In order to provide accurate information for refining of steel containing more than 1 mass pct Al, previously known information about Al deoxidation equilibria in liquid iron was critically reviewed. New Al deoxidation equilibria, Al and O contents in liquid iron in equilibrium with solid Al₂O₃ were measured at 1873 K and 1923 K (1600 °C and 1650 °C) over the whole Al composition range, 0.0027 < [pct Al] < 100. In order to secure the deoxidation equilibria, in the present study, the Al deoxidation experiments were carried out by employing three different methods: (1) traditional Al deoxidation by the addition of Al into Fe-O alloys, (2) oxidation of Al in Fe-Al alloys by the addition of Fe₂O₃ as an oxygen source, and (3) addition of CaO flux for an effective removal of suspended Al₂O₃ inclusions in liquid alloys containing high Al. In addition, in the present study, the O solubility limit in pure Al melt in equilibrium with solid Al₂O₃ was also measured in the temperature range from 1673 K to 1873 K (1400 °C to 1600 °C). The present experimental results provide a complete set of Al deoxidation equilibria in liquid iron which may be useful for the estimation of residual oxygen level and alumina inclusion formation in high Al steel processing. Interaction parameter formalism, which was originally proposed by Wagner and Chipman and has been widely used to interpret the Al deoxidation equilibria in liquid iron, was found to be inapplicable. Limitation of the interaction parameter formalism at high Al content in liquid Fe was discussed.