1986 Volume 72 Issue 15 Pages 2064-2069
A study was made on the rate of nitrogen desorption from molten iron by argon gas injection together with blowing onto the melt. The immersion depth of the nozzle was 4.65.2 cm. The injected gas flow rate was 5394 Ncm3/min. The oxygen contents in the melt were varied from 0.007 to 0.040%. During the experiment, the bubble formation time was measured by using a pressure pulse technique.
The observed rates are compared with the equivalents calculated from a mixed control model. From the comparison between calculation and experiment, the effective free surface area of the melt is obtained. Under the present experimental conditions the effective free surface area of the melt is independent of injected gas flow rate and oxygen contents. It is about 2.1 times as large as the cross sectional area of the crucible. Since the ratio of the area of the gas-metal interface to the volume of the metal was very large in the present experiment, the nitrogen concentration in the melt decreased very fast to less than 0.001%. Nitrogen desorption from molten iron can be explained by the mixed control model over a very wide range of nitrogen concentration.
