New macrosegregation criteria for quality problems in continuous casting of steel

Abstract

To estimate the quality condition in continuously cast steel slabs, simple but accurate macrosegregation criteria have been proposed. The formation of macrosegregation phenomena in continuous casting of peritectic carbon steels has been investigated by metallographic study of collected slab samples. The metallographic study involved plant trails to collect the slab samples and to prepare them for chemical macrosegregation analysis. The experimental results show a fluctuation of carbon between positive and negative segregation with distance from slab surface based on the cooling conditions experienced by the slab. Via mathematical analysis, formulae of average macrosegregation level ASL, its fluctuation level FSL and its segregation quality number SQN have been developed. The results calculated by these formulae show good agreement with the description of the formation mechanisms of different continuous casting defects and their locations. Therefore, these calculations illustrated that macrosegregation criteria and their distributions can be considered by experimental, simple and vital tools to evaluate the conditions of surface and inner qualities in continuously cast steel slabs. The mechanisms of these criteria with some mechanisms of continuous casting defects have been explained and discussed.