Effect of slag composition on wettability of oxide inclusions

Inclusion removal is key in the production of high quality steel. The inclusions are primarily removed from liquid steel by reacting with a liquid slag phase. For efficient inclusion removal, the inclusions transfer across the steel-slag interface to dissolve in the slag. This transfer process is strongly influenced by interfacial phenomena. In this study, the dynamic wetting (θ) of a range of slags in the CaO–Al2O3–SiO2–(MgO) system on solid oxides representing inclusion phases (Al2O3, MgAl2O4 and CaO.Al2O3) at 1773 K was investigated using a sessile drop technique. It was found that for all systems studied θ versus time showed a rapid decrease in wetting in the first 10 s tending to a plateau value at extended times. Further, for basic type ladle slags the plateau value was independent of slag composition and for acid type tundish slags the plateau value decreased with increasing basicity. Through work of adhesion analysis it was shown that ladle type slags appeared more suitable for inclusion removal and that from a wetting perspective calcium aluminate would be easier to remove than spinel and alumina. Choi and Lee’s dynamic wetting model was evaluated and found to not only represent the data well but have physical relevance for the basic, but not the acid, slags investigated