In-Situ Observation Combined with Numerical Simulation of the Solidification and Subsequent Cooling Process for Hot Stamping Steel

In this study, the solidification and subsequent cooling processes of hot stamping steel during thin slab casting have been investigated using high-temperature confocal in-situ observation experiments and finite element numerical simulations based on the calculation results of phase evolution diagrams. The numerical simulation results reveal that different regions of the cast slab exhibited varying solidification times/cooling rates, with the longest solidification time occurring at the center of the slab, approximately 77.5 s, and the shortest at the corners, around 2.1 s. Considering these findings, in-situ observation experiments have been conducted under cooling rates of 10, 50, 150, and 1000 °C/min, revealing that both solidification and solid-state transformation events are delayed with increasing cooling rates. Notably, under higher cooling rates, the peritectic reaction process exhibit blocky transformation. Based on the findings, this study establishes relationships between the ferrite growth rate/secondary dendrite arm spacing and cooling rate for hot stamping steel. Additionally, potential optimization strategies for continuous casting and secondary cooling process parameters are suggested to enhance the sophistication of thin slab production processes. These optimization methodologies are informed by guiding experiments conducted in conjunction with numerical simulations, ultimately facilitating the optimization of practical production practices.