Four kinds of test steels with different vanadium and nitrogen contents were smelted and cast by VN16 and FeV80 vanadium microalloying method. The effects of vanadium and nitrogen contents on the microstructure, strength and toughness of high strength hot-rolled steel plate were studied. The results show that the microstructure of test steels is ferrite and pearlite. When the nitrogen content is very low, the ferrite grain of vanadium microalloyed steel is coarse. Although increasing vanadium can refine the ferrite grain, the degree of refinement is not large. The ferrite grain of vanadium-nitrogen microalloyed steel is fine, and the increase of nitrogen can obviously refine the ferrite grain. The higher the nitrogen content, the greater the refinement degree. The nitrogen content is the main factor affecting the ferrite grain refinement. In vanadium microalloyed steel, the second phase particles are mainly precipitated in ferrite, which plays a strong role in precipitation strengthening, and the fine grain strengthening is relatively weak, resulting in the obvious increase of steel strength and decrease of toughness and plasticity when vanadium is added. In vanadium-nitrogen microalloyed steel, increasing nitrogen can effectively promote the precipitation of second phase particles in austenite, significantly enhance the fine grain strengthening effect of vanadium and weaken the precipitation strengthening effect, resulting in the improvement of steel strength, toughness and plasticity. The higher the nitrogen content, the more significant the strengthening effect.

microalloying  /  hot-rolled steel plate  /  microstructure  /  yield strength  /  tensile strength  /  toughness and plasticity