The Effect of Alloying Elements on the Kinetics of the Cementite Coarsening Stage of Static Spheroidisation in Fe-0.59wt%C-1.19wt%Si-0.65wt%Mn Eutectoid Steel

Authors: Sedat ÖZBİLEN

Abstract: The mechanism of spheroidisation and the thermodynamic basis for the effects of ternary and quaternary alloying additions, namely Mn and Si, on the rate of coarsening of cementite particles during static spheroidisation in Fe-0.59wt%C-1.19wt%Si-0.69wt%Mn eutectoid steel has been considered in detail and a rate equation for the change in size of individual cementite particles has been derived by using a model to estimate the effective rate of diffusion of the alloying elements. The theoretical calculations were compared with experimental measurements and a reasonable agreement was found between them regarding the coarsening rate in the quaternary alloys, indicating that the rate equation is controlled and the rate is decreased by Mn and Si diffusion and is also valid for the coarsening of cementite particles during the latter stage of spheroidisation at 700^0C where equilibrium partitioning of alloying element additions, i.e., Mn and Si, between ferrite and cementite is attained.

Keywords: Spheroidisation, alloying elements, cementite coarsening