LAUSR

Low-carbon V–N micro-alloyed steel plates (30 mm thick) were produced via various cooling processes. The differences between the microstructure and the properties of the experimental steels were analyzed and compared. The results indicated that a large amount of intragranular acicular ferrite with high density of dislocation and high misorientation boundaries formed in the experimental steel, and the quantities of finer V-containing precipitates increased at a finish cooling temperature of 538 °C. The strength and the impact toughness improved. The crystallographic characteristics of the experimental steels were analyzed via using electron back-scattered diffraction. The microstructures of experimental steels were observed on an optical microscope, a scanning electron microscope, and transmission electron microscopy. The strength enhancement was attributed to the refinement strengthening, the dislocation strengthening, the precipitation strengthening, and the transformation strengthening. The improvement of toughness was attributed to the microstructure refinement and the formation of high fraction acicular ferrite.