Abstract
Al metal powder added to MgO-C refractories plays important roles in suppression of carbon-oxidation. Size of Al grain causes difference in the behavior of Al, namely, in microstructure and properties of the refractories. Al reacts with carbon to give Al4C3(s) which forms a surface layer about 20μm thick. Thus, Al grains smaller than 40μm change to Al4C3(s) almost completely during early stages of heating, and then an aggregate of Al4C3(s) crystals gradually reacts with CO(g) to form C(s) and Al2C3(s) from it's surface. On the other hand, for Al grains larger than 40μm, an Al4C3(s) surface layer is formed and Al(l) left inside vaporizes by crashing through the layer of Al4C3(s). As a result, pores are formed, resulting in strengths lower than that for Al grains smaller than 40μm.
