Dissolution Kinetics of Cored Wire in Molten Steel

An essential feature in steel refining is the injection of calcium in the steel ladle in the form of a cored wire for de‐oxidation and inclusion modification. The melting behaviour of these cored wires has an important influence on the efficiency of the injection process, castability of steel and the product quality. The calculation of the time for melting of the casing of the cored wire and the subsequent release of the filling materials into the bath cannot be done without resorting to an elaborate mathematical model due to the complexity of the heat transfer from the bath to the wire. In particular the formation of a solid shell around the wire and consequent lowering of the heat transfer needs to be addressed accurately. A mathematical model for calculating the melting time of the casing has been developed at R & D, Tata Steel. This model describes the freezing and melting process during the travel of the cored wire in the steel bath. The model has been validated against published data. Owing to the complexity of obtaining a direct validation, a novel indirect method has been adopted. The variation in the operating conditions demands variation in the cored wire parameters to make the injection process equally efficient under all conditions. The model has also been used to formulate the specification of cored wire to suit the injection temperature of different grades of steel.