Analysis of decarburization reaction in RH degasser and its application to ultra-low carbon steel production

Theoretical and experimental studies were carried out to quantify the effects of the fluid flow, reaction sites, and geometry of the vacuum vessel on the decarburization characteristics of the RH degasser. The distribution of carbon concentration in the ladle was calculated throughout treatment. The maximum value, found near the bottom of the ladle, was double the minimum value, but this difference was shown to have no effect on the decarburization rate. The ratio of the decarburization rate at the bath surface to the total rate in the RH was greatest in the ultra-low carbon region, while that at the molten steel-refractory interface was the smallest. The maximum decarburization rate and minimum final carbon content between 6 and 12 ppm were attained with the largest vacuum vessel (cross-sectional area, 5.1 m²; inner diameter of snorkel, 1.0 m). On the basis of theoretical and experimental analyses, a procedure was established for determining the geometry of the RH vacuum vessel required to obtain a specified aimed carbon content.