Abstract
This study examined the influence of silicon content, addition of nickel, and inoculation on the impact properties of annealed spheroidal graphite cast iron with a ferritic structure at a constant C. E. value (C. E. =C+1/3Si=4.3) ; an analysis of impact fracturing behaviour and microfractography on the fractured specimens have been performed. When the C. E. value is the same, the transition temperature increases considerably as the silicon content increases but the shelf energy absorbed in the ductile range does not change so much by the silicon content. The transition temperature, maximum fracture load and lower yield load all increase by the addition of nickel. By adding ferrosilicon for inoculation, the transition temperature decreases. This is attributed mainly to the increase in the number of graphite particles which act as a barrier to the propagation of brittle cracks. From the result of microfractography, the decohesive fracture pattern at twin-matrix interface was found to incline to appear frequently in the brittle fracture of higher silicon content cast iron.
