Modelling of compacted graphite cast iron solidification - Discussion of microstructure parameters

Abstract

A melt maintained for hours in a press pour unit allowed the following changes over time from spheroidal graphite to compacted graphite iron by casting thermal cups at regular time intervals. This provided extensive experimental information for checking the possibility of simulating solidification of compacted graphite irons by means of a microstructure modelling approach. During solidification, compacted graphite develops very much as lamellar graphite but with much less branching. On this basis, a simulation of the thermal analysis records was developed which considers solidification proceeding in a pseudo binary Fe-C system. The simulated curves were compared with the experimental ones obtained from three representative alloys that cover the whole microstructure change during the holding of the melt. The most relevant result is that the parameter describing branching capability of graphite is the most important for reproducing the minimum eutectic temperature and the recalescence which are so characteristic of the solidification of compacted graphite cast irons.