Microstructure and texture characterization after hot rolling in low-C steels

Abstract

The study of hot band microstructure and texture during the hot rolling process is of great importance within the general context of texture development during thermomechanical material processing. In this thesis work, the microstructure and texture after hot rolling of several low carbon steel grades (LC, ELC, ULC, B-ULC and IF) are of interest. Hot band characterization is meant to be made on the basis of the influence of parameters such as finishing rolling temperature (FRT), strain at the last pass, and chemical composition. Regarding the microstructural characterization, the grain size characterization is addressed. Optical microscopy (OM) together with the AnalySIS auto image post-processing software are used. In the second part of the work, texture development for the ELC and ULC steels is further investigated by means of XRD. A correlation between the chemistry and the hot band grain size is established based for the several grades of interest. However, the effect of parameters such as FRT, strain at the last pass could not be clearly determined. The behaviour of the austenite can be traced back by the resulting transformation textures after cooling. The measured textures for the ELC and ULC materials could not make it possible to determine the behaviour of the austenite during the hot deformation. The effect of the reduction in the last rolling pass is also investigated.