In Situ Observations and Microstructure Evolution Behavior of Static Recrystallization of Microalloyed Continuous Casting Slabs in a Solidification End Reduction Process

Solidification end reduction is a novel technique that can effectively refine the microstructure and improve the homogeneity in continuously cast steel. Herein, the static recrystallization (SRX) behaviors and microstructure evolution of microalloyed continuous casting slabs during the heavy reduction (HR) process are simulated and analyzed by means of high-temperature laser scanning confocal microscopy (HT-LSCM). According to the statistical results of microstructure, the insulation temperature has a more significant effect on the SRX fraction and recrystallization grain size compared with the strain rate, initial austenite grain size, and prestrain, and a modified SRX kinetic model is proposed. Furthermore, a deforming microstructure is observed at different strains and holding times with electron backscatter diffraction (EBSD), and it is found that the reduction of high-angle boundaries (HAGBs, theta > 15 degrees) of 25 degrees-35 degrees is related to strain-induced boundary migration (SIBM). The stored deformation energy of HAGBs is higher than that of very low-angle boundaries (VLAGBs, theta < 5 degrees) by the detailed misinterpretation profile analysis of the block and lath boundaries. Finally, the combination of in situ observation and EBSD analysis shows that the stored deformation energy provides the driving force for the SRX process, which, in turn, consumes dislocations to stabilize the microstructure.