A new approach to molten steel refining using fine gas bubbles

Abstract

A new process has been developed for metal refining. This process involves the creation and dispersion of fine bubbles in molten metals by introducing inert or reactive gas into a turbulent flow region during metal transfer. The highly turbulent metal flow splits the gas into fine bubbles and results in good mixing between the gas and molten metal phases. These conditions are ideal for contacting inclusions in the metal with the bubbles and subsequent flotation of the inclusions to the metal-slag interface where the inclusions are then absorbed by the covering slag layer. Dissolved gases, such as [H], [O], [N], in the metals are also transferred to the gas bubbles and removed from solution. The process can be retrofitted into existing process plants. The process concept has been demonstrated using a full-scale air/water model to simulate the ladle-to-tundish system of continuous casting of steel. At liquid flows typical of those encountered in the caster, fine bubbles smaller than 0.5 mm in diameter can be created and a good mixing between the dispersed gas and the liquid has been achieved.