Effect of sulphur on iron carbide formation and stability

Abstract

Effect of sulphur on iron carbide process was investigated by examining iron ore reduction, iron cementation and cementite decomposition under gas atmosphere with and without sulphur. Sulphur added to H2-Ar gas in the form of H2S slightly decreased the rate of iron ore reduction at 750°C, but had a negligible effect at 850°C. Sulphur strongly retarded iron cementation. At 850°C, cementite was formed in 10 min by sulphur-free gas, 100 min when gas contained 50 ppm H2S, and 180 min when H2S was in the amount of 100 ppm. The rate of cementite formation increased with increasing temperature from 750°C to 925°C. Sulphur also strongly retarded free carbon deposition and stabilised cementite. However sulphur had no significant effect on the rate of cementite decomposition when it was introduced to the gas atmosphere after the completion of the cementation process.