Interface reactions between liquid iron and alumina–carbon refractory filter materials

The possibility of a carbothermic reaction between alumina and carbon is discussed based on thermodynamic calculations. A thermodynamic assessment of the Fe–Al2O3–Al corner of the Al–Fe–O system was done, and an interaction parameter of the metallic liquid phase was derived to model the solution of aluminium and oxygen in the ternary system. The derived dataset was used to calculate two experimental setups: (1) Fe–Al2O3–12.9 mass%C at 1550 °C under argon atmosphere as found in the literature and (2) the possible interface reaction between Fe–Al2O3–30 mass%C at 1650 °C. Interface reactions between Al2O3–30 mass%C and Al-killed steel 42CrMo4 at 1650 °C were studied experimentally using a steel melt-casting simulator. Large particles of exogenous alumina were found on a thin layer of alumina on top of the refractory material. The formation of an in situ-formed alumina layer can be explained thermodynamically by the partial dissolution of alumina and carbon in the iron melt at the interface and the reprecipitation of alumina at the filter surface.