Solubility products of titanium sulphide and carbosulphide in ultra-low carbon steels

Abstract

The equilibrium precipitation behaviour of Ti stabilised interstitial free steels was studied quantitatively. The solubility products of TiS and Ti4C2S2 in austenite were determined with dissolution experiments. The results are as follows log[Ti][S]=-13975/T + 5.43 log[Ti][C]0.5[S]0.5 = -17045/T + 7.9 The calculated results using these solubility products agree well with other experimental results of steels not involved in the dissolution experiments. The solubility products obtained in the current work were compared with other published solubility products of TiS and Ti4C2S2 using all known experimental data from different sources to the knowledge of the authors, and it was shown that the solubility products determined in the current work provided the best fittings with the experimental results. The influence of reheating time on the precipitation state in the steels was also investigated. It was shown that at high temperatures (e.g. 1 150°C) equilibrium state of precipitates can be reached within one hour during reheating.