Abstract
The formation of bubbles at the nozzle exit and the subsequent rising behavior of the bubbles in a molten iron bath at 1250°C were observed using a high voltage X-ray fluoroscope and a high-speed video camera. The frequency of bubble formation at the nozzle exit, the mean bubble diameter, and the mean bubble rising velocity were obtained for a wide range of the injected argon gas flow rate. Empirical correlations of these quantities were proposed and compared with previously published data and empirical correlations.
It has been commonly believed that the frequency of bubble formation at the nozzle exit depends solely on the gas flow rate and the outer diameter of the nozzle when the gas flow rate is relatively high and the wettability between the nozzle material and the molten metal is bad. The present experimental results revealed that the frequency of bubble formation had a close relationship not with the outer diameter but with the inner diameter of the nozzle. Also, the bubble frequency depended on the gas flow rate and the physical properties of gas and molten metal. The critical gas flow rate for the initiation of smaller bubbles due to disintegration of larger bubbles was found to be approximately 60cm3/s under the present experimental conditions. The bubble behavior near the bath surface also was made clear.
