Mechanisms of inclusion formation in low alloy steels deoxidised with titanium

In the present investigation, the conditions for inclusion formation in two Ti deoxidised steels and one AI-Ca deoxidised steel have been examined by means of optical and electron microscopy, in combination with a thermodynam ic analysis of the phase relations involved. It is concluded that the Ti co ntaining inclusions form as a result of a series of reactions occurring in the ladle, during solidification and ire the solid state. The important sol id state reaction products are MnS, TiN, and MnOTiO2. The presence of Mn ri ch compounds at the surface of the inclusions is consistent with the observ ation of a Mn depleted zone in the surrounding steel matrix. In contrast, t he primary inclusions in the AI-Ca deoxidised steel are complex oxysulphide s, which are thermodynamically more stable and can therefore form in the li quid state. MST/4351.