The rate-limiting process in the desulfurization of ferroalloys in vacuum melting was confirmed by a kinetic study. The increasing order of rate of desulfurization is as follows : Fe-S<Fe-C-S<Fe-C-Si-S. In Fe-Si-S alloy, the rate of desulfurization is well explained from the evaporation of SiS from the surface of the melt. It is suggested that the rate-limiting process is the evaporation of desulfurization products from the surface of molten iron
