Effects of additions of 0.0039, 0.01, 0.019 and 0.029 wt.% Sb on austenite transformation and the metallic matrix structure in the wall thicknesses of 3, 12, 25, 38, 50, 75 and 100 mm of ductile iron casting containing 2.11 wt.% Si and a low amount of Cu, Sn and Mn were analyzed in this paper. In the examined ductile iron casting without the addition of Sb, the share of pearlite in the metal matrix was decreased and the share of ferrite was increased with increasing wall thickness. The share of pearlite was low. Additions of Sb were increased the share of pearlite in all the walls. Increase of Sb content resulted in increasing the share of pearlite. Almost the same high share of pearlite in the wall thicknesses of 12, 25, 38, 50, 75 and 100 mm was obtained by addition of 0.029 wt. % Sb (varied from 96.00 to 97.61 %). The additions of 0.01, 0.019 and 0.029 wt.% Sb were resulted in a fully pearlitic metallic matrix in the wall thickness of 3 mm. Iron carbides were found in the wall thickness of 3 mm when Sb was added.