Morphology and segregation in continuously cast high carbon steel billets

Abstract

Morphology and centerline macrosegregation in continuously cast high carbon steel billet samples were investigated in order to establish the casting behavior of a six strand curved mold billet caster without electro-magnetic stirring. Several billet samples were collected from the continuous casting shop of Tata Steel, India and experimental observations were correlated with the operating parameters of the caster. Macrostructural examination revealed predominantly columnar structure associated with high degree of segregation and porosities In all billets cast above 21°C of tundish superheat. Centerline porosity was practically absent in the billet cast below 21°C. These billets showed prominent V-segregation and less prominent centerline segregation. Transition from U-segregation to V-segregation was observed around 21°C superheat. An attempt has been made to study the effectiveness of secondary cooling by measurements of the secondary dendrite arm spacing at various locations in billet samples. Finally, degree of segregation of constituent solute elements were correlated among themselves and applicability of one of the simple segregation models to the centerline macrosegregation has been tested. © 2007 ISIJ.