Dissolution Kinetics of Cored Wire in Molten Steel

Abstract

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.

Melting of Moving Strip during Steel Strip Feeding in Continuous Casting Process

“…With a relatively low feeding speed, the strip feeding speed is dominate factor and thus the distance travelled increases with the strip. It is supposed that at a much faster speed that increases the heat transfer significantly, the decrease in melting time becomes the dominate factor, as a result, the increase in feeding speed may not necessarily help the strip to travel more distance . But, those significantly high speed does not look mechanically feasible in strip feeding process which is out of our research category.…”

Interfacial Phenomena and Inclusion Formation Behavior at Early Melting Stages of HCFeCr and LCFeCr Alloys in Liquid Iron

“…This shell grows to a certain maximum thickness until the heat supplied to the surface through convection becomes equal to the heat conducted inside. [32] Due to the fast freezing, small-sized FeO inclusions (< 1 lm) are formed inside this shell, which is called the ''inclusion-free'' zone (Figure 18(b)). (3) As the heat is continuously transferred from the liquid Fe to the alloy side, the solid Fe shell starts to melt.…”

Efficacy and recovery of calcium during CaSi cored wire injection in steel melts

“…The heat transfer coefficient h in equation (4) has been calculated from Nusselt number correlation for flow parallel to a cylinder, given by equation (5) 9 Nu~0 : 037 Re 0 : 8 Pr 0 : 43 (6) Re and Pr are the Reynolds number and Prandtl number respectively. For calculating the Reynolds number, the characteristic velocity is taken as the velocity of the wire.…”