关键词: 高强耐候钢Q550NQR1, 珠光体偏析, -40℃, 冲击韧性, 铌, 钒

Abstract: This research investigated 8.0 mm thick high strength weathering steel Q550NQR1 with relatively low -40℃ low temperature impact value, and multiple pearlite segregation bands were observed in core microstructure, although the segregation bands are narrow and discrete, the quantity is numerous and ratio reaches 5. 8% ; through test, the segregation band in core microstructure has little effects on mechanical performance of tested steel, which is considered to be resulted from the effects of fine grain strengthening and precipitation strengthening by Nb-V micro alloying； however, the interface of ferrite and pearlite is relatively weak, which facilitates generation and extension of crack, as well as the pearlite segregation band likely leads to increase of ductile-brittle transition temperature thereby deteriorating low temperature impact toughness of tested steel. The improved technologies that increasing heating temperature and assuring enough heating time, increasing cooling rate in laminar cooling section as well as controlling the contents of Nb and V were adopted to conduct rolling, and for the final product, grain refinement achieves, pearlite segregation band vanishes, mechanical performance satisfies requirement and the surplus is appropriate, as well as -40℃low temperature impact average value increases 84.3 J.