Simulation of longitudinal surface defec

Cracks and depressions in steel continuous casting often start during initial solidification in the mold and evolve later in the process. To understand the mechanism(s) of formation of these defects, a finite-element model of transient thermal-mechanical behavior during steel solidification has been developed and applied to simulate longitudinal depressions. The thermal model features a detailed analysis of heat transfer across the interfacial gap, which is fully coupled with a thermal-mechanical elastic-viscoplastic finite-element model that calculates the evolving size and shape of surface depressions. The results are compared with analysis of a sample with a longitudinal surface depression and crack from a commercial continuously cast slab. In this scenario, a thermal event caused a local drop in heat transfer, followed by frictional tension on the domain due to slab shrinkage, led to shell necking and the formation of a localized U-shaped depression. Finally, a new visualization methodology has been developed to better reveal defect formation in real time, such as longitudinal depressions, which persist as they move down the mold at the casting speed.