Study on Slag-Steel Reaction between Cao-Al2o3-Ce2o3-5%Mgo-7%Sio2 Slag System and Fe-Al Steel System

Abstract

We studied the slag-steel reaction between RE-containing slag system and Fe-Al steel system. Thermodynamic analysis based on the IMCT activity theory and subsequent high temperature experiments were carried out to study the variation of T.Ce in steel with reaction time, the evolution of non-metallic inclusion type in steel, and the change of precipitate type in slag. The results show that the final content of Ce in steel increased with the increase of w(CaO)/w(Al2O3) and w(Ce2O3) of the slag and with the increase of w[Al] of the steel. The restrictive step in the initial stage of the slag-steel reaction was the interfacial reaction, where the reaction rate was only affected by a(Ce2O3) of the slag and a[Al] of the steel. For the medium stage, the accumulation rate of Ce content in steel decreased due to the consumption of reactants and the accumulation of products during the interfacial reaction. In the current work, a maximum of 80 ppm of Ce can be introduced into the steel during the slag-steel reaction. With the slag-steel reaction proceeding, the content of Ce and Mg in steel increased while that of Al and O decreased, resulting in the modification of Al2O3 inclusions into MgAl2O4, CeAlO3, CeAl11O18, and their combinations; MgAl2O4 is a metastable inclusion in some experimental groups, which disappeared in the final stage. Different types of precipitates were found in the final slags, including 2CaO·Al2O3·Ce2O3, 2CaO·3Al2O3·Ce2O3, CeAlO3, MgAl2O4, and MgO. A phase diagram showing the coexistence relationship of CaO-Al2O3-Ce2O3-MgO system was determined.

Keywords: CaO-Al2O3-Ce2O3-MgO-SiO2, Re-containing steel, slag-steel reaction, indirect alloying, Thermodynamics