This article presents the design process of the casting technology for a step-shaped casting made of steel using simulation tools. A series of proposals for gating and feeding systems were simulated in the MAGMASoft® software. Results of numerical simulations allowed the Authors to select the casting technology which allows defect-free casting to be obtained. A numerical analysis of the cooling rate of a step-shaped casting made of GX70CrMnSiNiMo2 tool steel with a 5% Ti addition was carried out for the selected manufacturing technology. Due to the nature of the material used and the extended presence of martensite during cooling, in-mold hardening of the casting may occur. The simulations showed that the type of molding material affects the cooling rate, which is confirmed by the analysis of cooling curves and the morphology of shrinkage porosity. The analysis of solidification rates provides a valuable starting point and basis for subsequent research stages, taking into account the actual properties of the molding sands and the phase transformations occurring in the selected steel type. The casting technology design, which ensures the production of sound casting, was developed as part of this study. A series of simulations using different molding materials confirms the significant impact that the choice of mold material has on the casting solidification and cooling process.