The circulation flow rate of a steel melt, which is one of the important factors which determine decarburization rate of RH system, was calculated by using a 3-dimensional numerical simulation technique. A new model for evaluating the shape and volume of the plume zone, formed by Ar gas blown through multiple nozzles on the wall of the snorkel, was proposed to determine the driving force of melt circulation.Circulation flow rates were measured in the 1/10 scale water model and in a real RH system to verify the calculation results with good agreement with the calculated circulation flow rates.Because the computer program can calculate the circulation flow rates at various operating conditions and dimensions of the RH system, it may be useful in determining the optimum operating conditions and designing new RH systems.

Internal morphologies of bulk shape oxides in a melt of Ti bearing low-carbon steel were analyzed. The outer shapes of nearly spherical inclusions containing Ti were quite different from the shape of alumina inclusions that typically have a cluster form. A cross-section investigation using a polishing method and the FIB method revealed that the TiO x -Al 2 O 3 complex oxide covers alumina clusters and that the interfaces of the alumina and complex oxide are modified as time passes.

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