Observations of pulsating Marangoni phenomena during the local oxidation of deoxidized liquid steel

Studies have been made by means of a high-speed video technique of the surface of Al-Si-Mn deoxidized liquid steel at about 1600 degrees C during local reoxidation by gently impinging flows of CO2-containing gases. Expanding 'necklaces' of alumina oxidation product have been observed to form at frequencies of up to about 5 Hz and to travel at velocities of up to 250 mm s(-1) near to the gas inlet tube, depending on the experimental conditions. The pulsation frequency appears to be controlled by the rate of diffusion of aluminium to the surface. The effects of additions of the surfactants sulphur and selenium on the velocity of the moving front are shown to be consistent with the processes being surface tension driven.