A vertical cut at the mid-depth of the 15-ton forging steel ingot has been performed by curtesy of the CELSA – Huta Ostrowiec plant.
Some metallographic studies were able to reveal not only the chilled undersized grains under the ingot surface but columnar grains and
large equiaxed grains as well. Additionally, the structural zone within which the competition between columnar and equiaxed structure
formation was confirmed by metallography study, was also revealed. Therefore, it seemed justified to reproduce some of the observed
structural zones by means of numerical calculation of the temperature field. The formation of the chilled grains zone is the result of
unconstrained rapid solidification and was not subject of simulation. Contrary to the equiaxed structure formation, the columnar structure
or columnar branched structure formation occurs under steep thermal gradient. Thus, the performed simulation is able to separate both
discussed structural zones and indicate their localization along the ingot radius as well as their appearance in term of solidification time.