Morphology and Macrosegregation in Continuously Cast Steel Billets

Abstract

In the transverse sections of low carbon continuously cast steel billets, samples for analyses of carbon and sulphur were collected by drilling at the billet centres as well as at the columnar-equiaxed transition (CET) boundaries, as revealed in etched macrostructures. Correlation of degrees of segregation for carbon (rc) with those for sulphur (rs) agreed closely with that predicted by Scheil's or modified Scheil's equation at the CET boundaries, but not at the billet centres. Variations of rc and rs with fractional solidification, although did not agree with predictions of the above equations, were in qualitative agreement with actual macrosegragation data reported in literature. Attempts were also made to correlate the experimental macrostructural and macrosegregation data with predictions based on conjugate fluid flow-heat transfer model developed earlier. Results of this exercise demonstrated close agreement of the predicted locations of CET boundaries with the measured values. This is being taken as additional confirmation of the reliability of the conjugate fluid flow-heat transfer model. Also, it seems that this model may be employed to estimate the size of equiaxed zone in continuous casting of steel. © 1994, The Iron and Steel Institute of Japan. All rights reserved.