Vacuum degassing impact on non-metallic inclusions during clean steelmaking

The objective of this article was to study the impact of duration of vacuum degassing process on the type and morphology of non-metallic inclusions which are undesired & unavoidable by product of steelmaking process. During the vacuum degassing stage five top slag and steel samples were taken. All sample occasions measured chemical composition of the molten steel and top slag, and SEM analysis of the non-metallic inclusions. It was seen that during vacuum degassing process the chemistry, dispersions as well as the morphology of the non-metallic inclusions is constantly changing. The Alumina content of the top slag is increased while CaO content is reduced. The percentage share of calcium aluminate type of inclusions verses spinel is increased. In the beginning of the vacuum degassing wt-% of Al in non-metallic inclusions is the highest however as the time passes this wt-% is reduced at the same time inclusions with larger ECDs appear.