The control of type, morphology and quantity of non-metallic inclusions is an important topic both in steelmaking and refining and in welding. It has been established that besides the known effects in mechanical properties, non-metallic inclusions can also affect austenite decomposition in steel. Titanium content plays an important role in defining the inclusion population in welds and some titanium oxides are among the inclusions that influence the most austenite decomposition. In a previous work the Kapoor-Frohberg model modified by Gaye (IRSID) was used to describe the liquid phase in the MnO-TiO2 system. In this work the on going extension of the description to include other oxides (initially FeO and Al2O3) is presented and discussed. The potential applications of this description to slag-steel and steel-inclusion equilibria are highlighted and examples are presented.