A novel laboratory technique for introducing inclusion to liquid steel
Previous studies in steel cleanness have been hampered by limited control of inclusions’ phase and composition. This limited control is often a result of studying inclusion formation and development using industrial steel melts and the inclusions therein as starting material. This is an extremely complex situation and not always readily amenable to analysis. A new experimental laboratory technique has been developed that allows addition of inclusions of known, size, phase and composition to be added to liquid steel. These inclusions can then be tracked and changes in morphology with time can be assessed for different melt conditions. The technique involves the formation of a steel-oxide compact, where high-purity inclusions are sandwiched in steel foil at high pressure. This compact is added to a steel melt of controlled and known composition. The use of this sandwiching technique overcomes problems of passing small particles (inclusions <50 μm) through the gas-melt interface and inclusion agglomeration. Details of the technique are presented and discussed and results applying this new technique in a reactivity study using cerium oxide as a synthetic inclusion in steel are given.
Morphology and composition changes of spinel (MgAl2O4) inclusions in steel
Abstract In this study, spinel inclusions of close to stoichiometric MgO.Al2O3 composition and known size distribution were added to a liquid steel bath before assessing their reactivity. The inclusions were then tracked for changes in size, morphology and composition with time in an aluminium killed steel at 1600°C, by sampling of the melt followed by automatic SEM based inclusion analysis techniques. The majority of the inclusions in the melt were alumina and complex sulphide inclusions, with the added spinel inclusions being a small proportion of the total inclusions. The proportion of alumina inclusions increased with time. The spinel inclusions were found to be evenly distributed through the melt and there was little change in their average size during the reaction. However, the composition of the inclusions did change, with the Mg/Al mass-% ratio changing from ∼0·5 to 0·08.
Activities of SiO2 and Al2O3 and activity coefficients of FetO and MnO in CaO-SiO2-Al2O3-MgO slags
The activities of SiO2 and Al2O3 in CaO-SiO2-Al2O3-MgO slags were determined at 1873 K along the liquidus lines saturated with 2CaO · SiO2, 2(Mg,Ca)O · SiO2, MgO, and MgO · Al2O3 phases using a slag-metal equilibration technique. Based on these and previous results obtained in ternary and quaternary slags, the isoactivity lines of SiO2 and Al2O3 over the liquid region on the 0, 10, 20, 30, and 40 mass pct Al2O3 planes and those on the 10 and 20 mass pct MgO planes were determined. The activity coefficients of FetO and MnO, the phase boundary, and the solubility of MgO were also determined.