Carbon Diffusion in Liquid during Steady State Solidification of Flake Graphite Cast Iron

Abstract

Carbon redistribution in the liquid ahead of planar and paraboloid interfaces of flake graphite cast iron unidirectionally solidified was calculated. The fraction of carbon diffusion in the liquid f in eutectic solidification is related to the growth rate R, the intergraphite spacing λ, the diffusion coefficient of carbon in liquid D and undercooling at the solidification front ΔT₀, as
fλR=0.0032DΔT₀
This equation is approximately valid both for the planar and paraboloid interfaces at different temperature gradients. The calculated f decreases with a decrease in the growth rate. This corresponds to the empirical fact that the paraboloid protrusions become more prominent with a decrease in the growth rate. The fraction of carbon diffusion through austenite sheath (1−f) in eutectic solidification increases with increasing growth rate. The protrusions often appearing on the slowly solidifying interface are attributed to a less undercooling at the interface, where carbon diffuses both in the liquid and the austenite, than that in the liquid.