抄録
A study has been made of the rate of deoxidation of molten silver by inert gas flushing. Argon was blown into the melt through an immersed nozzle 1.5 mm in I.D. and 3.0 mm in O.D . The gas flow rate under the normal state was 0.75–3.33×10−6 m3/s. The immersion depth of the nozzle was 15–65 mm. From the rate data, the deoxidation efficiency f was calculated. The efficiency was very high: f>0.6 at [%0]=0.298 and f>0.95 at [%0]=0.149.
On the basis of the assumption that the rate is controlled by one or two of the three rate-controlling steps of gas- and liquid-phase diffusions and chemical reaction at the bubble-metal interface, various reaction models are developed. The rate data are consistent with the model describing the liquid-phase mass transfer during bubble formation at the nozzle and bubble ascent through the melt. From comparison between the measured and calculated times of bubble formation, it is shown that mass transfer during bubble formation makes a large contribution to the deoxidation process: especially in the range of low oxygen concentration of the melt, the oxygen pressure in the bubble is nearly in equilibrium with the oxygen concentration in the melt before the bubble detaches from the nozzle.
