Mathematical model for austenitization kinetics of ductile iron

A mathematical model was developed in the current study to understand the progress of austenitization process in ductile irons. The austenitization time required to produce homogeneous austenite in a two-phase region of austenite and graphite has been estimated in terms of (a) time required for transformation of matrix to austenite and (b) time required for dissolution of graphite in austenite to attain uniform carbon content, which remains in equilibrium with graphite. The time required been related to the structural parameters of cast ductile iron-like radius of graphite nodule, radius of austenite cell, volume fraction of graphite, volume fraction of ferrite in cast matrix, and diffusion constant. The model was used to determine the minimum austenitization time required to achieve homogeneous austenite in three commercial ductile irons when austenitized at a temperature of 900 degrees C. The results were compared with those obtained. The uniformity of the carbon content in austenite of ductile iron was verified indirectly by measuring microhardness.