Development of low manganese micro-niobium thick plate based on water cooling process after rolling

Through the effect of micro-niobium alloying and water cooling after rolling, a 50 kg low manganese micro-niobium thick plate based on water cooling after rolling was successfully developed. After the steel plate was cooled by water after rolling, the banded structure between the original polygonal ferrite and pearlite lamellae was broken, some of the structure was transformed into bainite, the polygonal structure was reduced, the acicular structure was increased, and the grains were more uniform. The results of scanning electron microscopy and energy spectrum analysis show that the niobium alloy mainly formed granular NbC in the steel plate, and the particle size was about 1 μm. The tensile and impact properties of the developed steel plate met the requirements of the standard for Q355D steel, and the welding performance was good, which met the requirements of large heat input welding of 50 kJ/cm.