Improving strip surface quality of AA6111 alloy using different casting atmospheres for the horizontal single belt strip casting (HSBC) process

Abstract

The surface quality of as-cast strip is a key factor in the production of strips produced by Horizontal Single Belt Strip Casting process (HSBC). Aluminum alloys were cast on an HSBC simulator, using different casting atmospheres at meniscus region, including preheated air and pure oxygen. The strip’s bottom surface was analyzed in order to evaluate the effect of casting atmosphere on strip surface quality. The preheated air or oxygen was injected into the hollowed backwall refractory and was released through the orifices on the bottom of the refractory, close to the back-wall meniscus region. The purpose was to flush out the ambient air entrained above the moving substrate. The possibility of eliminating surface defects caused by air pockets’ on the strip’s bottom surface and improving surface quality by controlling the casting atmosphere in the meniscus region were confirmed. The surface profiles of the sand-blasted substrates and those of the related strips were analyzed using 3D Profilometry. The interfacial heat fluxes through using an oxygen atmosphere at the upstream meniscus were also enhanced greatly, as compared to the casting process using a graphite coating on the substrate. A novel way for improving strip surface quality with high attendant interfacial heat fluxes is now proposed for the HSBC process.