Effect of Refractory Binder on Inhibition of Oxide Growth in Molten Al-5%Mg Alloy

Abstract

  When molten aluminum alloy is held in a mold, oxides are formed on the surface of the molten alloy. If oxides are mixed into the product, they can cause various problems. In this study, we focused on the binders used in refractories to reduce the amount of oxides formed. We investigated the effect of the SiO₂-Sol binder in comparison with the P₂O₅ binder and Al₂O₃ cement. Molten Al-5%Mg alloy was held at 800℃ for six days in cups made using each binder. The results were as follows : 1) In the P₂O₅ binder cup, a very large amount of oxides was formed at the interface with the refractory and on the upper surface of the molten alloy. 2) In the Al₂O₃ cement cup, almost no oxides were formed at the interface with the refractory, but a relatively large amount was formed on the upper surface. 3) The amount of oxides formed on the surface of the molten alloy in the SiO₂-Sol binder cup was small both at the interface with the refractory and on the upper surface. This was thought to be due to the effect of the flexible microstructure of the oxide film, realized by needle-shaped MgO, SiO₂ particles, Al₂O₃ particles, etc. bending three-dimensionally and overlapping with each other.