A study was made on the rate of nitrogen desorption from molten iron by argon gas injection. Argon was injected into the melt through an submerged alumina nozzle of 0.1cm in I.D. and 0.3cm in O.D. The immersion depth of the nozzle was 4.65.2cm. The gas flow rate was 7496 Ncm³/min. The oxygen contents in the melt were varied from 0.004 to 0.066%. During the experiment, the bubble formation time was measured by using a pressure pulse technique.
The measured desorption rates are compared with those calculated by a mixed control model considering mass transfers in both liquid and gas phases and chemical reaction at the bubble-metal interface. Nitrogen desorption during bubble formation is taken into account in the model. From the comparison between calculation and experiment, the chemical reaction rate constant was obtained. It is shown that the chemical reaction rate constant decreases with increasing [%O] + [%S]/2. The rate constant obtained in the present study agrees well with that in the previous study of nitrogen absorption in molten iron. It was confirmed that both nitrogen absorption and desorption in molten iron could be explained by the mixed control model.