Liquid Iron Wetting of Calcium Aluminates

Abstract

An investigation has been carried out to assess the wetting behaviour of liquid iron carbon alloys on alumina, CA6 (CaO·6Al₂O₃), CA2 (CaO·2Al₂O₃) and CA (CaO·Al₂O₃). The melt compositions studied were 2 and 5 mass% [C] over a temperature range of 1450 to 1550°C. It was found that the systems studied were in general non-wetting, and that the contact angle dropped from approximately 140° to 110° as the calcium content of the substrates increased. The data for alumina were in good agreement with the literature. These data have been used to assess whether capillary phenomena play a significant role in coke dissolution in liquid iron. In previous studies it was found that as coke dissolved, a mineral layer consisting of alumina and calcium aluminates formed at the coke iron interface and that as time passed the mineralogy of the layer changed from CA6 to CA2 to CA. The rate of coke dissolution slowed considerably with the occurrence of the CA phase. It was not clear whether this was solely a densification effect, or if a capillary wetting issue was contributing to a reduction of the contact area. The contact angle measurements of iron on alumina, CA6, CA2 and CA have been discussed in light of this coke dissolution study, and a simple capillary penetration model used to assess the wetting effects. It was found that the change of wetting associated with the calcium enrichment of the mineral layer did not have a significant effect on the rate of coke dissolution.