Development of Rare Earth High Performance Weather Resistant Bridge Steel Q345qFNH

Aiming at the high quality requirement of long-span, high-strength and lightweight bridge steel, a new type of high-performance bridge steel was developed by using low-carbon and low-crack-sensitivity composition design route and TMCP process. The weather resistant elements of Cu, Cr and Ni were added to ensure the corrosion resistance of the steel plate, and rare earth Ce was added to further improve the low temperature impact toughness and corrosion resistance of the steel plate. The results show that the open rolling temperature in recrystallization rolling area of the new bridge steel is1150-1190℃, the final rolling temperature in non-recrystallized rolling zone is 820-870 ℃, the cooling rate is 6-10℃/s, and the final cooling temperature is 630-650℃. The microstructure is pearlite and ferrite, and the strength, plasticity, cold bending and low temperature impact toughness all meet the standard requirements. The average corrosion rate of the test steel decreases from 51.8 μm/a to 34.50 μm/a after adding RE element Ce.