CONTROL OF THE CHROMIUM OXYGEN REACTION IN PURE IRON MELTS

Oxygen activities in Fe-O-Cr melts, equilibrated with chromium oxide, were determined as a function of chromium content by EMF measurements using ZrO2(CaO) plug-type sensors with a Cr-Cr2O3 reference. Plug-type sensors with or without Cr2O3 saturator were used in the experiments. From the experimental results values for the activity coefficient f(O ) and the interaction parameters e(O)(Cr) and r(Cr)(O) were evaluated. Raoultian chromium activity features a slight positive deviation from ideal solution behaviour in the temperature range from 1550 to 1650 d egrees C. Taking into account the calculated interaction parameters, t he equilibrium constant K-Cr-O was redetermined at 1550 to 1650 degree s C. In comparison with previous studies a better agreement was obtain ed with existing thermochemical data.