<Original Papers>Some Experiments on the Behavior of Sulphur in Molten Fe-S-Si Alloy under Vacuum

The rate of evaporation of sulphur from the melt was measured by the method similar to Langmuir\u27s. It was found that the increase in the evaporation of sulphur with silicon was much larger than that estimated from the activity of sulphur of previous investigators. The variation of sulphur and silicon contents in the melt and the composition of condensates indicated that the mole ratio of sulphur to silicon evaporated during the process of vacuum melting was nearly equal to unity. These results show that the vacuum desulphurization is mainly due to the formation of gaseous compounds, such as SiS. From the experimental data, it was found that partial pressure pSiS for the reaction S+Si=SiS(g) at 1,600℃ was as follows : log pSiS (atm)=log α_Sα_+0.2