Rate of nitrogen desorption from CaO-Al2O3 melts to gas phase

There is a limit to lowering the nitrogen level in steel, because of pickup from the atmosphere during and after degassing. Therefore, the nitride capacity of various fluxes has been measured in order to examine the possibility of nitrogen removal by using slag. It is necessary to take into account the nitrogen reaction rate between the gas and slag phases for the efficient removal of nitrogen in practical steelmaking processes. In this study, the nitrogen desorption rate from CaO-Al₂O₃ melts to gas phase has been examined at 1873 K. The mass-transfer coefficient of nitrogen in the melts increases as the CaO content increases, and the dependence is related to the viscosity of the melts. The reaction-rate constant of nitrogen desorption is found to be proportional to the 3/2 power of the oxygen partial pressure and increases as the CaO content increases under constant oxygen partial pressure.