Modeling of different zones of as-cast structure of high carbon steel ingots

Abstract

Ingot casting technology has been expanded to large parts during the last decades. As the ingot sizes increase, higher quality of the as-cast semi-products is demanded, with regard to the control of casting defects like macrosegregation and structure inhomogeneity. In order to investigate macrosegregation and to estimate the as-cast structure, theoretical study and simulation work on ingot solidification are carried out at the Department of Ferrous Metallurgy of RWTH Aachen University (IEHK). A solidification model has been developed, and based on that, modeling of the structure morphology has been performed. A proper coupling of the developed solidification model with experimental results from IEHK is under investigation. This solidification model is a two-phase FVM model applied for high carbon steel with 0.6 wt.% [C]. The temperature and concentration fields of the solid and liquid phases have been calculated and these results can provide information for further prediction of the solidification structure such as CET (Columnar to Equiaxed Transition) zone and casting defects in an ingot. The structure morphology model introduces a shape factor of grains as the quantitative criterion for identification of the structure morphology. It focuses on the interaction between nuclei density and resulting macroscopic structure, and can calculate the strictly columnar zone, CET zone with mainly columnar characteristics and enclosed equiaxed crystals, and the pure equiaxed zone. The results will be presented, and the correlation of CET zone with development of macrosegregation in the inner part of an ingot will be discussed.