In situ observation and investigation of effect of cooling rate on slab surface microstructure evolution in microalloyed steel

In the process of continuous casting, the cooling rate is the key factor affecting and deciding the slab surface microstructure. In this study, confocal laser scanning microscopy was used for in situ observation of, and research on, slab surface microstructure evolution under different cooling rates. It was found that the slab microstructure was uniform, and there was no obvious filmlike proeutectoid ferrite or chainlike microalloyed element precipitation in the prior austenite grain boundary under the cooling rate of 3-6 degrees C s(-1). The results of hot tensile experiments showed that this microstructure had a higher hot ductility, which contributed to the virtual disappearance of the brittle trough and reduction of the steel's cracking susceptibility.