Analysis of the Solidus Temperature of Multicomponent Steel by a Finite Thickness Model with Heat- and Solute-Transfer Equations in the Solid–Liquid Zone

To examine the assumption of a constant solidus temperature—which has been empirically adopted in general heat analyses without firm validation—in all solidification stages for multicomponent steels, heat- and solute-transfer equations were simultaneously solved using the finite thickness model, which focuses on early-to-late-stage solidification except final-stage solidification. In early-to-middle-stage solidification, the model provides a constant solidus temperature, as predicted by the previously reported semi-infinite thickness model wherein the solidification front was far from the strand center. In late-stage solidification, however, the present model exhibited a slightly decreased solidus temperature—almost within the temperature measurement accuracy range. This suggests that the assumption of a constant solidus temperature does not exactly hold in late-stage solidification but is not unreasonable from a practical viewpoint. The obtained solutions agree well with numerical analyses and are in reasonable agreement with thermoanalytical measurements and industrial findings. Thus, the present model supports the assumption of a constant solidus temperature and estimates the solidus temperature in early-to-late-stage solidification, which can play a role in search of an adequate solidus temperature as an approximate analytical solution for multicomponent steels.