Structural Reconstruction of Solidification Kinetics in Cast Iron with Spherical Graphite

抄録

A novel method for the structural reconstruction of solidification kinetics in cast iron with spherical graphite (SGI) is described in this paper. The method includes an automated SEM/EDX analysis of different micro-features in SGI structure, separation of graphite nodule statistics from non-metallic inclusions, and conversion to a three dimensional Population Density Function (PDF_exp). A structure integrator was developed to simulate the PDF_sim for the arbitrary nucleation and growth rate functions. Structural reconstruction of the solidification kinetics in the industrial castings was done by inverse optimization and matching both PDF functions at unique parameters of graphite nodule nucleation and growth.
It was shown that SGI solidification kinetics in industrial castings significantly differ from those predicted by basic nucleation models. The cooling rate and inoculation have large effects on the kinetics of graphite nodule nuclei formation during solidification. It was proved that the observed bi-modal PDF function in inoculated SGI is related to the second nucleation wave. The suggested method provides insight into the nucleation process in SGI casting and can be used as a tool for process control. Reconstructed solidification kinetics can help in the design of effective inoculants and melt treatment methods. Knowledge about nucleation parameters can be also used for improving simulations of casting solidification.