METHOD FOR CALCULATING THE MICROSTRUCTURE & MECHANICAL PROPERTIES OF DUCTILE CAST IRON

Ductile Cast Iron (DCI) is now widely accepted as a material for manufacture of thickwalled containers for the storage and transport of spent fuel and intermediate level radioactive waste. Material specifications for DCI in this application (e.g. ns G 5504, Rehmer et al., 1995) require that both certain mechanical properties and microstructure are achieved throughout the casting. Most important of these requirements include minimum elongation, maximum 20% pearlite in the matrix, and minimum 80% nodularity of the graphite (when measured using the ISO 945 method). These properties all depend upon the cooling conditions during solidification, which vary throughout a casting. This paper will describe a method for calculating the distribution of microstructure and mechanical properties of a thick-walled ferritic DCI casting from a knowledge of the temperature-time history during solidification, as obtained, for example, from a thermal solidification analysis.