Denitrogenization Mechanism from Molten Steel by Flux Treatment

Abstract

Experiments of nitrogen desorption from molten steel by flux treatment have been proceeding and the reaction rates have been investigated. The flux of the CaO-Al₂O₃-CaF₂-BaF₂-SiO₂-MgO system is effective for nitrogen desorption from molten steel, The nitrogen transfer rate from the steel to the gas phase could be increased by using the present flux, when the free surface of molten steel is exposed to argon atmosphere. The reason for the increase is that surface activity elements such as oxygen and sulphur in the molten steel were decreased and the interfacial resistance between the metal and gas was reduced. Under the present conditions, the nitrogen desorption from molten steel to the gas phase was more rapid than the nitrogen absorption of slag from the molten steel. The rate determinations step of nitrogen desorption from molten steel is changed from the interfacial chemical reaction step to the mass transfer of the metal phase, depending on the reduction of oxygen and sulphur in metal.