Influence of inclusions modification on nozzle clogging

Abstract

During the secondary refining of high strength steel in a ladle furnace aluminum is used for the melt deoxidation. Aluminates inclusions are modified with a calcium silicon injection in a melt. On the basis of the binary diagram CaO-Al 20 3 solid and liquid calcium aluminates with different composition and shape are formed after calcium treatment. During the calcium silicon injection manganese sulphide is also modified and CaS or (Ca, Mn)S is formed and wrapped around calcium aluminates.Because of rising of calcium bubbles during the calcium silicon injection a powerful melt stirring occurs. This enables inclusion coagulation and a reaction with a slag. Additionally, the MgO•Al 20 3 spinels are formed.Clogging of a tundish nozzle may occur during continuous casting of steel billets. Scull which forms on the nozzle's inner wall consists of spinel, calcium aluminates with various composition and calcium manganese sulphide.