Estirnation of Oxidation of Teeming Molten Steel by Air

Abstract

Reoxidation behavior of molten steel during the several pouring processes is studied referring to the previous results of model experiments.
It is found that gas volume entrained during teeming of molten steel increases with increasing length of stream and velocity at nozzle exit, and with decreasing nozzle diameter. It is, however, independent of physical properties of molten steel such as surface tension, viscosity and density, except under the condition of high teeming height and small nozzle diameter. As for the amount of oxygen absorption through surface of teeming stream, it is approximately 1/10 of that absorbed by the air entrainment at plunge region in metal pool, if the stream is practically laminar. However, difference between them decreases with decreasing teeming rate and teeming height.
A nomograph for estimation of oxygen absorption by gas entrainment and also through surface of stream was proposed.
Oxygen absorbed during teeming from ladle to tundish at continuous casting of molten steel decreases with increasing casting rate. Under a constant casting rate, it decreases with increasing casting time accompanying increase of stream radius and decrease of stream exit velocity. It is also suggested that all of oxygen in entrained gas bubbles dissolves into liquid steel.