Calculation of Initial Stage of Solidified Shell Deformation during δ to γ Transformation in Mold

Solidification shell deformations within the mold during continuous casting have been calculated in order to clarify the influence of mold flux infiltration variability on the cooling rate, the width of the low heat flux region, the height of air gap, the unevenness of solidified shell, and the resulting strain in the solidified shell. A sequentially coupled thermal-mechanical finite element model has been developed to perform the calculations. The simulation includes heat transfer and shell deformation in a growing solidified shell, along with the delta-to-gamma transformation. Further, it takes into account the effects of variability in mold flux infiltration and air gap formation on heat transfer into the mold, as well as the effect of cooling rate on the thermal expansion resulting from delta-to-gamma transformation. The results showed that mild cooling and small width of low heat flux region (i.e. low variability in mold flux infiltration) strongly decrease the height of the air gap, the unevenness in the solidified shell and the strain in the solidified shell. It is confirmed that it is important to optimize the cooling rate and prevent the variation in mold flux infiltration, especially at near the meniscus region of δ to γ transformation in order to minimize longitudinal crack formation.