The aim of this paper was to examine the influences of different amounts and additions places of alloys and slag forming additions on the slag characteristic and the refractory material of the casting ladles (especially the slag zone). Ideal addition formulas dependent on the steel quality have been derived form the results, which should help to reduce the wear of the lining without interfering with the metallurgical work of the slag. Four different types of slags (for ULC-IF, LC, KPST44 and HIC steel grades) were examined at preassigned times in the work-flow. The locations of the slags in the quarternery system Al2O3 CaO 10 M-% MgO - SiO2 have been determined and the slags were assayed concerning their MgO-saturation. The weight of the slags and the wear of the MgO-C-lining of the slag zone have been calculated by Al/Al2O3- and P/P2O5-material-balances. As a result the slag addition formulas have been optimised concerning chemical composition and amount.