Promotion of Inclusion Float-out in Continuous Casting Tundish Bath by Gas Blowing

Abstract

The gas blowing method using a perforated plate, was studied to solve the problem of decrease of inclusion removal efficiency in a tundish bath on the high casting speed. The floating behavior of inclusions in the tundish bath during gas blowing was studied in connection with the fluid flow state of molten steel. A mathematical model which predicts the inclusion removal efficiency has been developed. It was postulated in the model that the tundish bath consists of three regions : a mixing flow region, a circulating flow region and a stagnant region. In the mixing flow region, inclusions are transferred by various sized vortices. In the circulating region produced by gas blowing, inclusions are transferred mainly by upward flow. The stagnant region is not involved in inclusion transfer.
The validity of the model was comfirmed by the results of cold model experiments and actual operations. It was found by the above model that the uniform bubbling flow occurred in the low flow rate of gas was effective for promoting the floating removal of inclusions and the faster the casting velocity, the stronger this effect became.