Effect of Vanadium on the Precipitation Behavior and Aging Properties of Higher Yield Strength Weathering Steels

The target-oriented researches on the Vanadium-containing weathering steels were conducted in this paper.Methods such as thermal simulation test,precipitate phase quantitative analysis,tensile test and so on were used to investigate the vanadium precipitation behavior and aging properties of higher yield strength weathering steels with different process condition.It has been found that with increasing N content the vanadium precipitation ratio in tested steels is significantly higher than that in referred steel.Increasing N content leads to a large V precipitation amount and V precipitation potential during cooling process.AI value is decreased when the V/N ratio increased,but the V/N ratio is less than 3.5 against aging performance.The critical technological parameters of 450 MPa grade higher yield strength weathering steel was confirmed,and the optimal coiling temperature of tested steel was 650 ℃,which corresponds to the combined effect of grain refinement and precipitation strengthening.Considering the effect of nitrogen on aging performance,the ratio of V/N in V＆N microalloying high strength weathering steel should be controlled to be a little higher than the ideal V/N chemical coordination ratio value（3.64）to achieve the best comprehensive properties.