Thermodynamics Dependent on Size in Nucleation Process of Inclusion and Calculation of Critical Nucleus Radius in Clean Molten Steel

The nucleation process of non-metallic inclusions in molten steel was analyzed based on nano-thermodynamics theory,and calculation model was established.The relational expression of nucleus's size dependent interface energy between liquid steel and nucleus was obtained by considering effect of nucleus's size on interface energy,and then,the Gibbs free energy change expression of nucleation was established by analyzing influence of nucleus's size on its solubility.The mathematic formula for critical radius of nucleus was deduced by differential Gibbs free energy change of nucleation.The critical radius of nucleus of Al2O3 inclusion was calculated adopting both nano-thermodynamics and classical nucleation thermodynamics simultaneously.The results show that numerical value of critical radius of nucleus of Al2O3 inclusion based on nano-thermodynamics is greater than numerical value based on classical thermodynamics in the same conditions.During the process of terminal aluminum-deoxidation in liquid steel,numerical value of nucleus's critical radius of Al2O3 inclusion is approximate 1.40-2.72 nm by nano-thermodynamics,and value is 1.02-1.69 nm based on classical thermodynamics.The conclusions are consistent of results by molecular dynamic simulation and experiments in relate literatures.