Effect Of Melt Stirring On Impurities Redistribution During Ohno Continuous Casting Of An Industrial Aluminum Alloy

The mode of redistributing the excess solutes accumulated at the solid-liquid interface during Ohno Continuous Casting (OCC) is a key factor determining the purity of the produced ingots. A control of mass transport occurring during OCC process is necessary to achieve higher purity ingots. The goal of this work has been to determine the best mechanical stirring method and stirring intensities under different casting speeds required to produce ingots of maximum purity during OCC. To determine the best stirring method, steady axial and transverse convective velocity cells were induced into the melt through mechanical stirring to produce rotational convective flow fields near the concave solid-liquid interface and their effect on solute transport were compared. The convective flow fields induced by axial stirring were found to be strong enough and effective in transporting accumulated solutes from the interface deep into the bulk melt. Using the determined axial stirring method, the critical stirring intensities required for different casting speeds were numerically determined. Melt agitation, with special axial flow field and magnitude was externally induced into the melt through mechanical rotation of a silicon carbide blade inserted into the melt and positioned just ahead of the solid-liquid interface and its effect on solute transport was simulated using ANSYS Fluent 12.1 software. It was found that, with adequate axial melt stirring, production of high purity ingots at high casting speeds (convectional OCC speeds) during OCC process is possible.