Kinetics of Nitrogen Desorption of Liquid Iron, Liquid Fe-Mn and Fe-Cu Alloys under Reduced Pressures

The rates of nitrogen desorption of inductively stirred liquid iron were measured under reduced pressures at 1 600°C, lind the effects of manganese lind copper 011 those rates were discussed. The rates of nitrogen desorption were apparently represented by the equlItion of sec on a order reaction rate in terms of nitrogen cOlltellt in liquid iron as shown by the previous investigators with the results obtained under lin argon atmosphere. The values of the rate constant of lIitrogen desorptioll, k N , decrease witlt increasing oxygen content in liquid iron and agreedfairly well with those obtained by other investigators when the oxygell cOlltellt is more than 0.02 % . At low concentrations of oxygen in mplts, however, the values of k N obtailled in the jJTesent work are higher than those of others, though there are some discrepancies amollg them. These results were exI)lained by lhe application of lhe mixed-control model ill eluding the mass transfer in both phases and the chemical reactioll at the inteljace. Consequently, although the rale of nitrogeh desorption has been regarded as the chemical reaclion control, the mass transfer in liquid iron should play an important role on the nitrogen desorption at lower oxygell concentratiolls. It is also found thllt the vaporizatioll of mangallese or copper in liquid iron decreases the rate of nitrogen desorj)tioll, due probably to the local decrease of interfacial temperature caused by the latent heat of vaporizatioll alld also to the decrease of the ejlctive reaction sitesfor nitrogen desorption.