Effect of Mn on Solubility of Ti-sulfide and Ti-carbosulfide in Ultra-low C Steels

To clarify the thermodynamic stability of Ti4C2S2 and TiS in ULC Ti-added IF steels, extraction by potentiostatic electrolysis method and chemical analysis were conducted with ULC Ti-added IF steels containing various amounts of Mn and heated at various temperatures. As the results, the solubilities of Ti4C2S2 and TiS increased with an increase in Mn content. Ti4C2S2 was more stable than TiS between 950 and 1250°C. Following solubility products were obtained.log[Ti]·[C]0.5·[S]0.5=0.392−7004/T−(4.783−7401/T)·[Mn]log[Ti]2/3·[S]=−0.021−5847/T−(3.360−5195/T)·[Mn]