Kinetic study of the nitrogen removal rate from molten steel (normal steel and 17 mass%Cr steel) under CO boiling or argon gas injection

A nitrogen removal experiment was carried out under reduced pressure using a 600-kg-scale induction furnace. Using normal and 17 mass%Cr steel, two methods to promote the reaction were selected, i.e., expansion of the reaction area with CO boiling and reduction of surface active elements, with the aim of promoting the chemical reaction at the metal-gas interface. Kinetic results indicate that surface active elements act on the whole experimental condition, and the rate determination step is predicted to be a chemical reaction at the gas-metal interface. Applying the chemical reaction equation obtained by previous research on high-chromium steel, the nitrogen removal rate can be explained using the same estimation method. The results obtained in the present study indicate the importance of development of an effective method to increase the gas-metal surface area.