1995 Volume 81 Issue 12 Pages 1126-1131
Studies have been made on bubble formation at non-wetted nozzles and orifices and on the effect of bubble size on the rate of inclusion removal from molten metal.
The bubble formation at a nozzle or an orifice in mercury has been investigated. The experimental values of size of the bubble formed at a nozzle agree with those calculated from correlating equations using outer diameter of the nozzle. In the case of lower gas flow rate, the bubble size increases with increasing outer diameter of the nozzle (dno<7mm). At nozzle diameter of dno>7mm, the bubble size is independent of dno, and the nozzle can be regarded as an orifice. The bubble size increases with increasing gas-chamber volume under the conditions where the gas flow rate is relatively low and the dimensionless gas-chamber volume, Nc', is larger than unity.
The rate of SiO2 inclusion removal from molten Cu to slag with injecting Ar gas from multi-orifice and multi-nozzle has been examined. In the case of multi-orifice, the bubble size increases with increasing the number of orifices. This shows that the growing bubbles coalesce into one on the surface of the orifice plate. The rate of inclusion removal decreases with increasing bubble diameter. It is confirmed that the inclusion particles are removed from the melt mainly through adhesion to the bubble-metal interface.
