Abstract
The experimenal results and considerations on the desulfurization of Fe-Si-S and Fe-C-Si-S alloys in vacuum-melting are summarized as follows: (1) The desulfurization velocity of Fe-Si-S and Fe-C-Si-S alloys is more rapid compared with that of the Fe-C-S alloys. And the minimum sulfur concentration obtained in vacuum melting of the Fe-Si-S and Fe-C-Si-S alloys is lower than that of the Fe-C-S alloys. In the case of vacuum melting of Fe-Si-S alloys, both a desulfurization and a decrease of silicon concentration occur at the same time, and the sulfur concentration obtained decreases with increased silicon concentration; the sulfur concentration obtained in melting at 1700°C is lower compared with that obtained in melting at 1600°C. In the case of vacuum-melting of Fe-Si-S alloys which contain approximately the same amount of Si and S, the ratio of the decrease of sulfur to the decrease of silicon closely approximates the weight ratio of sulfur to silicon which is required to form the silicon monosulfide SiS. (2) From the experimental result made by Oelsen-Maetz and the author’s thermocynamic consideration, it may be considered that if a chemical reaction, i.e., Si+S=SiS (g) is approximately in equilibrium during the vacuum melting, the desulfurization of Fe-Si-S and Fe-C-Si-S alloys should be almost carried out by the reaction which forms SiS, and that the strong desulfurization of Fe-Si-S and Fe-C-Si-S alloys should be due to a very high equilibrium partial pressure of SiS.
