Wetting characteristics of oxygen-containing iron melts on refractory oxides

As part of refractory erosion studies, the wetting behaviour of molten iron containing varying amounts of oxygen on refractory oxides was investigated by the sessile drop method. The oxides investigated in the present work were alumina, silica and mullite. The reactions were followed in static as well as dynamic modes, under isothermal conditions, through contact angle measurements. Other parameters investigated in the present study were temperature and oxygen partial pressure. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen at constant partial pressure, came into contact with the surface of the drop. At a critical level of oxygen in the metal drop, a reaction product started forming at the drop/substrate interface and at this stage the contact angle dropped suddenly. In all cases there was a tendency for the contact angle to increase after this minimum. In the alumina case, the iron drop moved away from the reaction site, once the product layer had been formed at the interface, probably due to the imbalance in the surface forces. In the case of SiO2 and mullite, liquid slags were formed. The substrates were analysed through SEM and EDS. The reaction products identified were in agreement with thermodynamic predictions. In the case of SiO2, deep erosions were formed along the periphery of the drops, probably due to Marangoni flow. The possible mechanisms of the reactions and their impact on refractory erosion are discussed in the light of the present experimental results.