Effects of temperature and [S] on the kinetics of nitrogen removal from liquid steel

The kinetics of denitrogenation from liquid steel was studied by an oxygen-nitrogen analysis system (LECO TC-436) under 1600°C-2813°C conditions. The results show that when [S]=0.005%, the nitrogen removal is controlled by the nitrogen transfer in the liquid diffusion layer and when [S]=0.012% and 0.140% it is controlled by both the nitrogen transfer in the liquid diffusion layer and the chemical reaction at the liquid-gas interface below 2250°C, and by the nitrogen transfer in the liquid diffusion layer under 2250°C-2813°C conditions. The activation energy E_a is 57 kJ/mol for 0.005%[S], 95 kJ/mol for 0.012%[S], 165 kJ/mol for 0.140%[S]. The resistance of sulphur on nitrogen removal decreases with the temperature rise, and disappears at 2630°C. Based on the results obtained, it has been answered why the nitrogen in liquid steel can be decreased rapidly by the carbon-oxygen reaction under very high oxygen and sulphur content conditions during the BOF, EAF, VOD and AOD steelmaking processes.