Formation Mechanism of the Oxide of Al-Si System in Molten Al

摘要

Molten aluminum which has highly chemical activity for oxygen is formed the unique oxide called "Obake" of the Al-Si-O system. the Obake was generated only when silicon was contained in aluminum alloy and silica was contained in crucible. Comparing chemical composition of the obake formed in an industrial furnace with that of the molten aluminum, Si component in the Obake was concentrated both from the castable refractory and the molten aluminum. The ratios of Si to Al in the molten aluminum and the Obake were expressed by Si:Al valence 5:89 and Si:Al valence 11:51, respectively. The indispensable condition of the formation of Obake was that SiO(g) was constantly supplied. The molten aluminum reacted with SiO_2(s) according to the reaction of SiO_2(s)+2Al(l) valence SiO(g)+Al_2O(g) to provide SiO(g) and A1_2O(g).Under the particular oxygen partial pressure, Si(l) in molten aluminum reacted with AlO(g) to from SiO(g). The presence of SiO(g) was revealed by the result of the industrial furnace test, that is, the increase of Si component in Obake, Furthermore, Obake grew when its surface was wetted by molten aluminum, that is, the contact angle between Obake and molten aluminum was reduced.