Thermodynamic Considerations on Desulfurization of Cast Iron in Vacuum Melting

In order to explain the desulfurization process in vacuum melting of cast iron, the alloy systems of Fe-S, Fe-C-S, Fe-Si-S, and Fe-C-Si-S were melted in vacuum, and considerable desulfurization was recognized in Fe-C-S, Fe-Si-S, and Fe-C-Si-S alloys. The desulfurization process was considered from the equilibrium conditions for desulfurization reactions. Relations between the desulfurization and the concentrations of carbon and silicon in Fe-C-S, Fe-Si-S, and Fe-C-Si-S alloys were explained on the basis of the phase rule. An Fe-C-S alloy was also melted in vacuum in a graphite crucible at 1300～1700℃, and the comparison was made between the experimental results and those calculated from equilibrium relation derived from thermodynamic data