Effect of BaSO_4 on the interfacial phenomena of high-alumina refractories with Al-alloy

摘要

The performance of high-alumina refractories used for aluminium casting significantly impacts the efficiency of metal production. The interfacial reactions with Al-alloys cause corundum and magnesium spinel deposition on the refractory surface, leading to refractory degradation. An experimental study was conducted to investigate the influence of varying barium sulphate (BaSO _4) concentrations in a high-alumina refractory on its interfacial reactions with molten Al-alloy in a horizontal tube furnace at 1523 K (1250 °C) under inert conditions. This study showed that the Al-alloy reactions with pure BaSO4 would form barium aluminates at the interface. However, in the Al-alloy/refractory system, the interfacial behaviour was strongly influenced by the relative amount of BaSO_4, such that up to 5 wt%, the extent of alloy penetration into the refractory increased with increasing BaSO_4 contents. Electron-probe micro-analyser and X-ray diffraction studies indicated that the composition of the interface for these refractories was augmented with barium silicates and diminishing anorthite phases. In the presence of 10 wt% BaSO_4, the extent of metal penetration into the refractory decreased, whilst for 20% BaSO_4, the penetration was higher; these results were attributed to the interfacial presence of celsian (BaAl2Si_2O_8) and unreacted barium sulphates, respectively. This study suggests that maximising the celsian formation at the interface is critical for optimising the BaSO_4 concentration for improving the refractory's performance for Al-casting.