Influence of Tramp Elements on Surface Properties of Liquid Medium‐Carbon Steels

The transformation of the steel industry is inevitably linked to increased recycling rates of steel. However, end‐of‐life scrap is often contaminated with tramp elements like copper, molybdenum, and tin and while their influence on mechanical properties of steels is well described, their effect on nonmetallic inclusions remains largely unknown. Therefore, herein, two medium‐carbon steels are alloyed with up to 1 wt% of the listed tramp elements. The influence these elements have on the inclusion behavior in liquid steel is investigated using the sessile drop method in contact with alumina and zirconia as well as in steel/slag melting experiments to evaluate the formation and separation of new inclusions. Additionally, a semiempirical approach using CALPHAD to model the surface tension of steels with tramp elements is done. Copper and tin decrease the surface tension, while molybdenum increases the surface tension. It is demonstrated that most investigated alloys lead to a decrease of wetting angle as compared to the nonalloyed steels. The shown trends in the sessile drop experiments are lower contact angles with increased surface tension while a higher number of inclusions occurs with a decrease in surface tension. Thus, this study demonstrates that tramp elements affect the oxidic cleanness of steels.