On Consonance between a Mathematical Method for the CET Prediction and Constrained/Unconstrained Solidification

Some properties of the functions yielding from the temperature field have been employed as a tool to determine the structural zones' localization in a large static steel ingot. Thus, a numerical simulation was performed to generate the temperature field converged subsequently into the thermal gradient field. As a result, the selection of a zone, in which a columnar into equiaxed structure transformation (CET) is expected, is possible. It is shown that the CET - zone is formed when the thermal gradient becomes temporarily constant. Moreover, the CET localization can be easily controlled / shifted by the mold thickness selection. Both temperature and thermal gradient fields were also calculated to predict mathematically the creation of some structural zones in the continuously solidifying brass ingot. The columnar structure resulting from the constrained growth seems dominant in these ingots. However, when the s/l interface rate and velocity of the liquidus isotherm movement are subjected to a separation then the birth of the equiaxed structure is to be expected. In the industrial practice, the following structural zones are evinced in a continuously cast brass ingot: chilled columnar grains-, (CC), fine columnar grains-, (FC), columnar grains-, (C), equiaxed grains zone, (E), and eventually the single crystal, (SC), situated axially. The current innovative method for the mathematical predictions of the CET appearance in the static ingot turns out also useful in the reproduction of the all mentioned structural zones' localization. In particular, a study of the behavior of the velocity of the liquidus isotherm movement and thermal gradient changes versus solidification time delivers a precise information about these structural zones' situation. (C) 2019 The Authors. Published by Elsevier Ltd.