Physical and Mathematical Models of Vortex Flows During The Last Stages of Steel Draining Operations from a Ladle

Abstract

Slag entrainment during steel teeming-drain operations from a steel ladle impacts negatively steel cleanliness and quality. In the present work water modeling and mathematical simulations using a multiphase model for momentum and heat transfer were employed to understand the mechanisms of vortex funnel drain and sink drain flows. The critical bath height for vortex development increases with steel throughput and valve gate opening. Six stages during vortex development are identified, passing from a dimple formation on the bath surface until sink drain which begins when the bath level has the same magnitude as the nozzle diameter. This later drain pattern is independent from any other teeming-draining variable being only a function of the bath height and nozzle diameter; when they are about the same the metal-interface collapses. The temperature gradients originated by the heat losses of the ladle to the surroundings provide buoyancy forces that are large enough to influence liquid motion in the ladle. At large bath levels steel observes long-vertical recirculating flows and at low bath levels these flows change to horizontal-circular recirculating flows that become a seed for later vortex development. These buoyancy forces increase the critical height for vortex development and slag entrainment.