Estimation of Air Oxidation of Teeming Molten Steel

Abstract

Reoxidation behaviors of molten steel during the several pouring processes were studied referring the previous results of model experiments.
It is found that the gas volume entrained during teeming of molten steel increases with increasing the length of the stream and the velocity at the nozzle exit, and with decreasing the nozzle diameter. It is, however, independent of the 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 the surface of teeming stream, it is approximately 1/10 of that absorbed by the air entrainment at the plunge region in the metal pool, if the stream is practically laminar.
A nomograph for the estimation of oxygen absorption by gas entrainment and also through the surface of stream was proposed.
Oxygen absorbed during teeming from ladle to tundish at continuous casting of molten steel decreases with increasing the casting rate. Under the constant casting rate, it decreases with increasing casting time according to the increase of stream radius and to the decrease of stream exit velocity. It is also suggested that the volume of gas entrained during this process seems to be nearly equal to the argon volume injected in the ladle for clean molten steel.
Applying this model to the steel tapping from the converter, it is roughly estimated that the oxygen absorption of liquid iron is nearly 11-16ppm O.