Analysis of the Fe–Ce–O–C–M phase diagrams (M = Ca, Mg, Al, Si) by constructing a component-solubility surface

Abstract

Analysis of the ternary phase diagrams of Ce₂O₃- and CeO₂-containing oxide systems allowed us to find the oxide compounds that form during steel deoxidizing with cerium and with cerium together with aluminum, calcium, magnesium, or silicon. The temperature dependences of the equilibrium constants of formation of Ce₂O₃ oxides and Ce₂O₃ · Al₂O₃, Ce₂O₃ · 11Al₂O₃, Ce₂O₃ · 2SiO₂, 7Ce₂O₃ · 9SiO₂ and Ce₂O₃ · SiO₂ compounds are found. Surfaces for the component solubility in metallic melts Fe–Al–Ce–O–C, Fe- Ca–Ce–O–C, Fe–Mg–Ce–O–C, and Fe–Si–Ce–O–C are constructed. Nonmetallic inclusions that form in the course of experimental melts of St20 steel after its deoxidizing with silicocalcium and rare-earth metal (REM)-containing master alloys in a ladle furnace after degassing are studied. Phase inhomogeneity of the inclusions is found. As a rule, they consist of phases classified into the following three groups: oxide–sulfide, sulfide–oxide, and multiphase oxide–sulfide melt. Calcium aluminates are found to be components of complex sulfide-oxide noncorrosive inclusions.