Si deoxidation and C deoxidation processes were compared

Background/aims: One main purpose of vacuum degassing is the removal of nitrogen and hydrogen from the liquid steel. The progress of dehydrogenation and denitrogenation during degassing cannot be observed on‐line from measured waste gas values. It is therefore usual to elongate the vacuum treatment more than necessary to be sure that the aim values are reached. To overcome the uncertainty in the required degassing duration, a dynamic process model for dehydrogenation and denitrogenation was developed. Results and conclusions: The dynamic process model for denitrogenation and dehydrogenation is based on the principles of thermodynamics and reaction kinetics. It was applied to the vacuum tank degassing (VD) and the vacuum circulation (RH) process. The model was validated by comparison of simulation results with measured process data. The resulting simulation accuracy is about 8 ppm for nitrogen and 0.2 ppm for hydrogen. A simplified version of the process model is used for on‐line observation of the current nitrogen and hydrogen content.