This article is concerned with the production of cast iron with spheroidal graphite (ductile iron) for the automotive industry. The properties of materials for automotive parts must be favourable, primarily for reasons of safety for the occupants of the vehicle. Therefore, the materials must be hard but sufficiently malleable, so that they can be significantly deformed upon impact without breaking. These favourable properties characterise ductile iron with high silicon content. As far as producing this cast iron is concerned, the metallurgical preparation of the alloy must be carefully carried out, and suitable charge materials must be selected, including modification and inoculation. The quality of the prepared alloy significantly affects the solidification process in both thin and thick parts of the castings. The aim of our research described in this article is to find the appropriate type and quantity of raw materials, modifiers and inoculants, and the required quantity of silicon in order to ensure the homogeneity of hardness in various casting thicknesses.