High‐temperature mass spectrometric study of the vaporization processes in the system CaO‐MgO‐Al2O3‐Cr2O3‐FeO‐SiO2

Knudsen effusion mass spectrometry was used to study vaporization processes and thermodynamic properties of twenty samples of chromium‐containing slags in the CaO‐MgO‐Al₂O₃‐Cr₂O₃‐FeO‐SiO₂ system in the temperature range 1850–2750 K. Tungsten cells were used and Cr₂O₃ solid was used as a reference material. The system was calibrated using liquid gold. As FeO was the first emanating vapor species, monitoring of the chromium‐containing species could be carried out only after the complete vaporization of FeO. This, however, was found to have very little impact on the concentration of the slags investigated. During the measurements, the ion current intensities of CrO⁺ and CrO species in the mass spectra of the vapor over the CaO‐MgO‐Al₂O₃‐Cr₂O₃‐FeO‐SiO₂ samples were monitored and compared with those corresponding to solid Cr₂O₃. Data on the partial pressures of vapor species as well as the activities of Cr₂O₃ as a function of temperature were obtained. The results are expected to be valuable in the optimization of slag composition in high alloy steelmaking processes. Copyright © 2009 John Wiley & Sons, Ltd.