A critical condition for the formation of a coarse columnar γ grain structure in a peritectic solidified carbon steel

The formation of a coarse columnar austenite grain (CCG) structure is a serious problem in continuous casting processes of peritectic solidified carbon steels. In this study, a guiding principle for the avoidance of CCG formation is developed. The critical condition for CCG formation recently put forward based on phase-field simulations, which is given by a balance between the cooling condition and the growth rate of the CCG, is first re-examined and modified by considering the effect of a liquid phase during the CCG formation. The validity of this critical condition is then investigated by three different casting experiments combined with heat conduction analyses. From a comparison between the cooling conditions and the resulting microstructural changes, the validity of the critical condition is successfully demonstrated. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.