The transformation of the steel industry not only leads to the need for alternative reduction processes but also requires increased scrap rates. End-of-life scrap usually contains elevated levels of tramp elements, like copper, molybdenum, and tin. These elements cannot be removed from steel melts by currently available processes. Therefore, these tramp elements are expected to accumulate in steels with every recycling cycle if the steel melt is not diluted with freshly reduced iron from ore. While it is well known that tramp elements influence material properties in a negative way and can lead to problems during continuous casting, their influence on the oxidic cleanness of steel remains mostly unresearched. Previous studies employing Drop Shape Analysis (DSA) showed that excess amounts of tramp elements, of up to 1 wt.-%, significantly decrease the wetting angle of medium carbon steels on various oxidic materials. Non-metallic inclusions with low wetting angles are supposed to have a reduced tendency to deposit into slag.
In this work, a medium carbon steel was alloyed with different levels of the tramp elements copper, molybdenum, and tin. These alloys’ wetting behavior was evaluated on alumina and zirconia at 1600 °C by DSA. Furthermore, these steels were melted in a resistance-heated furnace and held at 1600 °C for 30 minutes together with a pseudo-wollastonitic slag in alumina crucibles. The separation behavior of non-metallic inclusions was evaluated before and after melting with the slag using automated Scanning Electron Microscopy with Energy-Dispersive Spectroscopy (SEM/EDS). The findings were then linked to the corresponding wetting angles. In addition, thermodynamic calculations using FactSage were applied.