Effect of Mold Cavity Design on the Thermomechanical Behavior of Solidifying Shell During Microalloyed Steel Slab Continuous Casting

Corner transverse cracks are frequently observed on microalloyed steel slabs during continuous casting. As a solution to this problem, double phase-transformation technology could improve the ductility of the shell surface and avoid corner cracks. However, this technology requires a high cooling rate, which is difficult to reach in traditional flat plate molds (TFMs). Therefore, a novel convex structure mold (NCM) was designed to intensify corner cooling. To investigate the effects of mold design on interfacial heat transfer between the solidifying shell and mold, a thermomechanical model was developed considering the dynamic distributions of the mold slag layers and air gaps. Afterward, the interfacial heat fluxes between mold and solidifying shell obtained from the thermomechanical model were loaded on the flow, heat transfer, and solidification model to study the comprehensive influence of mold cavity design and steel flow on the shell temperature. Based on the models, the contact conditions, distributions of interfacial heat transfer media, interfacial heat fluxes, and temperatures and thicknesses of the solidifying shells were thoroughly compared between the TFM and NCM. The results show that the NCM provides a more appropriate compensation for the shell shrinkage; as a result, the thick slag layers concentrating in the corners of the TFM are flattened and homogenized in the NCM. Thicker slag layers in the TFM weaken the corner heat transfer and lead to uneven shell growth in the off-corner area. Meanwhile, the NCM could homogenize the off-corner heat transfer and increase the cooling rate of the shell corner to help implement double phase-transformation technology in the high-temperature zone of casters.