Abstract: Final cooling test was carried out on the pressure vessel steel Q345R, and the effect of final cooling temperature on mechanical properties and microstructure of the as-rolled and normalized steel plate was studied. The results show that the mechanical properties of the as-rolled and normalized Q345R steel at different final cooling temperatures meet the standard requirements, but when directy air cooled after rolling, the performance margin is small. When the final cooling temperature is 650 ℃, the mechanical properties are relatively better. With the increase of final cooling temperature, the yield strength, tensile strength, and impact property of the steel plate have a downward trend, and the microstructure gradually becomes coarser. The microstructure of the as-rolled and normalized specimens are all typical ferrite+pearlite, and after normalization of the steel plate, the yield strength and tensile strength are significantly lower than that of the hot-rolled steel plate, while the impact property is significantly improved, and the microstructure becomes finer.

Key words: final cooling temperature, Q345R steel, heat treatment, mechanical properties, microstructure