Production of Ductile Iron Castings with Different Matrix Structure

The relation between the kind of inoculants, the castings size and matrix structure of ductile iron was investigated. Inoculation was performed by using 4 different inoculants. Ductile iron was cast in test bars with diameters from 3 mm to 50 mm. The study of the microstructure showed that the effect of the kind of inoculant on the content of pearlite is significant only for regular specimen sizes. The hardness value was found to decrease with decreasing pearlite content in the matrix structure of ductile iron. The time between spheroidizing treatment and pouring has strong effect on the ductility of ductile iron. Ce-bearing inoculant reduced this effect. Tests were also conducted to investigate the effects of kind of inoculants and the diameter of specimens on the microhardness of pearlite. It was found that the microhardness of pearlite of small size specimens is higher than this one of large size specimens. Ce-bearing inoculant slightly equalizes pearlite contents and its microhardness in various specimens sizes.