Wear of direct-bonded magnesia-chrome ore refractories in the RH-TOB process

In order to elucidate the wear mechanism of direct-bonded magnesia-chrome ore refractories in RH-TOB (RH-Top Oxygen Blowing), crucibles were made from the MgO-Cr2O3 refractory, which are used as a side wall refractory material for the RH-TOB lower vessels. The crucibles were charged with melting stock to carry out the oxygen blowing experimental at 1650 degrees C. Experiment was discriminated the wear by FeO permeation and the wear by Fe fume. The chromite in the MgO-Cr2O3 refractory creates a complex spinel of a high melting point with FeO, therefore chromite is stable and shows a high corrosion resistance on FeO. On the other hand, FeO that has a very low melting point permeates magnesia that are composed of fine particles combined by silicate bonds. Consequently, an eutectic reaction causes the bond melts and separating the particles. The wear during the RH-TOB process results from the oxidation heat that is produced when the Fe fumes react with oxygen and impact the refractory dissolve away both magnesia and chromite.