Investigation on Decarburization and Denitrozenization of Liquid Iron

Abstract

Kinetic study of carbon and nitrogen removal in liquid iron has been made by examining separately or simultaneously the rate of decarburization and denitrogenization. Effect of the content of dissolved oxygen in liquid iron on the rate of decarburizing and denitrogenizing reaction has also been investigated. The liquid iron sample weighing 4 to 7g was kept on an alumina disc by applying a levitating power and the dissolved carbon and (or) nitrogen were removed by passing the argon with (or without) CO₂ (or O₂) through the reaction tube. The results obtained were summarized within the range of our experimental condition as follows:
1) STEFAN-MAXWELL equation for the diffusion of the multicomponent system could be fairly well applied to estimate the rate of decarburization in liquid iron.
2) When the content of carbon in liquid iron is higher than 0.1%, the decarburizing rate is controlled by the mutual diffusion of reacting gases through the gaseous boundary layer.
3) It is considered that the reaction sites for decarburization are on the surface of gaseous side of the gas-metal interface.
4) The rate of denitrogenizing reaction is proportional to the square of the concentration of nitrogen in liquid iron, and its rate is thought to be controlled either by the combination process between the adsorbed nitrogen atoms at the gas-metal interface or by the desorption process of the nitrogen molecules from the adsorbed sites.
5) When the decarburizing reaction is occurred only on the gas-metal interface, the rate of denitrogenizing reaction is thought to be not affected by the rate of decarburizing reaction.
6) The apparent activation energy of denitrogenization from the liquid iron is calculated to be 32 to 36kcal/mol.