Modeling Slag Behavior When Using Micro‐Bubble Swarms for the Deep Cleaning of Liquid Steel in Tundishes

Abstract

Gas bubbling through a ladle shroud can be an effective approach for the removal of inclusions. However, an exposed eye of steel often appears in the slag cover surrounding the ladle shroud, owing to re‐surfacing bubbles leading to the formation of an exposed eye of steel, termed a “slag eye,” resulting in heat losses and re‐oxidation of the liquid steel. In order to control the formation of such a “slag eye” during gas injection into the shroud, a novel ladle shroud is employed to produce micro‐bubbles, as small as 0.54 mm in diameter. The water model results revealed that reducing the sizes of bubbles that are created in the ladle shroud could effectively limit the formation of a “slag eye,” provided the bubbles are sufficiently small and dispersed. This allows them to pass through the top layer of slag without breaking it up. For a given inflow velocity and shroud configuration, the critical condition for forming a “slag eye” depends on a balance between the gas flow rate and the individual sizes of bubbles penetrating the upper slag layer. Slag layer behavior is also simulated numerically, using a three‐dimensional CFD model. Numerical predictions are in good agreement with corresponding experimental results.