Effect of industrial hot rolling mode on microstructure and properties of low carbon bainitic steel

Slabs of low carbon bainitic steel have been subjected to various modes of fractional hot rolling at fixed conditions of the next direct quenching and tempering. To assess influence of such treatments, microstructures and textures of bainite are determined by EBSD on representative areas and then analyzed with allowance for the resulting mechanical properties. The obtained data reveal a specific effect of hot deformation as far as the tempering does not significantly change crystallographic constitution of the quenched steel. According to the bainite textures, all considered modes lead to deformed states of parent austenite; at the same time, dissimilar types of the transformation product have been detected. Specifically, the softer (granular) bainite appears at higher strains and lower temperatures of the finish rolling stage because the work hardening of austenite increases the transformation temperature. Conversely, the lath bainite providing the maximum steel strength corresponds to properly limited strains of austenite at high enough temperatures.