Relation between section thickness, microstructure and mechanical properties of ductile iron castings

Our experimental works are conducted to establish the conditions required to produce a desirable structure of the castings of various section sizes. The main factors of influence on the structure that one needs to address are: chemical composition, cooling rate, liquid treatment and heat treatment. This investigation was focused on the study of the influence of section size and holding time after spheroidizing on the structure and mechanical properties of the ductile iron plates cast in sand molds of vertical and horizontal configuration. Melts of eutectic and hypoeutectic composition were used to cast plates of thickness ranging from 3 mm to 50 mm. The results showed that the wall thickness of ductile iron castings and holding time after spheroidizing had very strong effect on the microstructure of the castings. The holding time had significant effect on the elongation, but insignificant effected on the tensile strength and hardness of castings.