Modelling microstructural and mechanical properties of ferritic ductile cast iron

It is well known that the mechanical properties of ductile cast iron (DCI) depend on its microstructure, and that the microstructure depends on the properties of the melt and the cooling conditions during casting. There have been many studies of the individual elements of the process of casting DCI, but as yet there have been very few examples of modelling the entire process to predict cooling rates, microstructure, and mechanical properties, particularly for large castings. The present paper describes a method of modelling the microstructural and mechanical properties of ferritic DCI, and applies the methods to the case of a large (13 t) thick walled (300 mm thickness) casting. The microstructure calculated includes nodule count, nodularity, ferrite grain size, and percentage ferrite, The mechanical properties calculated include yield stress, tensile strength, elongation, and static upper shelf fracture toughness (J(1C) and K-JC), The calculated results compare well with those of a test casting, MST/4243. (C) 2000 IoM Communications Ltd.