CaO-SiO<SUB>2</SUB> 2元系スラグと炭素飽和溶鉄間の窒素の移行について

Abstract

This study was made on the reaction of the nitrogen transfer between CaO-SiO2 binary slag and carbon saturated iron melted in graphite crucible under an atmosphere of nitrogen, where the reactions of nitrogen absorption in slag and silica reduction to metal occurred simultaneously.The rates of nitrogen transfer were expressed by a zero order reaction for the forward reaction (from slag to metal) and a second order reaction for the backward reaction. The apparent activation energies were 47 kcal/mol for the forward reaction and 62 kcal/mol for the backward reaction. The forward reaction was promoted by the increase of the activity of silica in slag up to aSiO2=0.6 and then became extremely slow. Furthurmore, the rate of the forward reaction decreased as the slag-graphite, slag-metal interfacial area and the initial content of silicon in metal increased. While the rate of the backward reaction was also reduced by the increase of the slag-metal interfacial area, it was scarcely affected by the other variables.From these results, it is considered that the reaction of nitrogen transfer from slag to metal proceeds electrochemically and nitrogen in metal is partially removed to CO bubbles formed at the slag-metal interface. It appears that the rates of each reaction is controlled by chemical reactions and is greatly influenced by the advance of the reaction of silica reduction.