Mathematical model for decarburization of ultra-low carbon steel during RH treatment

A mathematical model was established to investigate the decarburization behaviour of ultra-low carbon steel during Ruhrstahl-Heraeus (RH) refining process. In this model, it was assumed that the decarburization reactions occur at four sites: Ar bubble surface, bath surface, bulk steel and splash droplet surface. The effect of Ar bubble behaviour and splash droplet behaviour on decarburization rate was taken into consideration specifically. The calculated results are basically consistent with the industrial experimental observations. Carbon concentration was mainly eliminated at bath surface at early stage of RH treatment, and was mostly removed in bulk steel at middle stage, and was removed at splash droplet surface in the final stage. The decarburization rate at different sites and its contribution to total decarburization value were evaluated in detail. The decarburization rate during RH treatment could be effectively improved by accelerating the drop of vacuum pressure at early stage. Appropriate increasing Ar gas flow rate was beneficial to deep decarburization by increasing the reaction area of droplet surface and bath surface.