Effects of Nb and V on Microstructural Evolution, Precipitation Behavior and Tensile Properties in Hot-rolled Mo-bearing Steel

Microstructural evolution, precipitation behavior, and tensile properties of four experimental Mo-bearing steels were studied to elucidate the effects of Nb and V on microstructural properties. The results indicated that the microstructure of hot-rolled steels consisted of polygonal ferrite and degenerate pearlite, and the morphology remained same after holding at 600 °C for 1 h. The smallest grain size was obtained in Nb-V-Mo containing steel, followed by Nb-Mo and V-Mo steels. Precipitation was less in the hot-rolled Mo-bearing steel. The maximum volume fraction of precipitates was obtained in Nb-V-Mo bearing steel, and the Nb-V-Mo complex carbonitrides were highly stable at 600 °C. In the Mo-bearing steel, the yield ratio was lowest at room temperature but highest at 600 °C, which was attributed to the precipitation of Mo carbides and drag effect of Mo solute on dislocation movement.