Rate Of Desulfurization Research Articles

This investigation has been made to ascertain the desulfurization process of cast iron in vacuum-melting. The results of Fe-S and Fe-C-S alloys are summarized as follows: (1) In vacuum-melting at 1600°C, an Fe-S alloy containing 0.075%S is slightly desulfurized and in five minutes a minimum sulfur concentration is obtained. And then the sulfur concentration increases with increasing time. In the case of melting of Fe-C-S alloys in graphite crucibles, considerable desulfurization occurs and after certain times finite sulfur concentrations are obtained. When an alumina crucible is used, although the initial rate of desulfurization of the Fe-C-S alloy containing 3.34%C is much slower than that of melting in a graphite crucible, this rate increases with increasing time and finally the sulfur concentration becomes lower than that of the Fe-C-S alloy melted in a graphite crucible. (2) It may be considered that a slight desulfurization of the Fe-S alloy should occur by oxygen-sulfur reaction and that the increase of sulfur concentration should be due to vaporization of iron. If the desulfurization reactions are approximately in equilibrium during vacuum-melting, it may be said that the Fe-C-S alloy which contains 0.01 to 0.5%S should be most strongly desulfurized by the reactions C+S=CS (g), S=S (g) and C+2S=CS2 (g) in the range of lower sulfur concentration, and by the reaction C+2S=CS2 (g) in the range of higher concentration. The increased rate of desulfurization in the melting of the Fe-C-S alloy in the alumina crucible is considered to be due to entrance of silicon into the melt from the crucible. It may be considered from the thermodynamic equilibrium condition that as far as the carbon concentration is fixed during vacuum-melting the obtainable minimum sulfur concentration should be decreased with increasing carbon concentration of the Fe-C-S alloy used. (3) The sulfur concentration obtained in vacuum-melting of an Fe-C-S-alloy in a graphite crucible for 1/2 hr decreases with increasing emperature, which result consists with the thermodynamic considerations.

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