Model Investigations on Slag Entrainment in Continuous Casting

Today continuous casting is the state of the art in industrial casting processes. The casting powder used fulfill various tasks such as preventing air contact, absorbing non-metallic inclusions from liquid steel, providing lubrication between strand shell and mould wall and controlling heat transfer. The mould powder in contact with liquid steel surface forms a liquid slag layer. The jet of liquid steel from submerged entry nozzle is reflected at the mould wall forming a lower and upper flow pattern. The upper flow moves along the steel-slag interface and generates shear stress at the interface and waves. Viscosityand density-differences between the two liquid phases leads under certain flow conditions to finger like protrusions. Reaching a critical flow velocity the protrusions can breakup and form slag droplets following the flow into the liquid steel-pool. These droplets can form finally non-metallic inclusions in steel material, cause defects in the final product and therefore should be avoided. Till now the physical mechanisms of slag entrainment are not completely understood.