Microstructural Evolution and Precipitation of V(C,N) in a Low-carbon V-bearing Steel

The microstructural evolution and micro-hardness change in a low-carbon vanadium steel ((0.058)%C-0.92%Mn-0.51%V) during isothermal holding after austenite region deformation were investigated with thermo-mechanical test, and the precipitation of V(C,N) was studied through TEM. The experimental results show that the single-phase ferrite matrix microstructure could be obtained by isothermal holding at 650℃, 700℃ and 750℃ after austenite region deformation while the pearlite could be eliminated. During the isothermal holding process, the ferrite nucleated primarily along the anstenite grain boundaries, and then within the austenite grains. Two precipitation modes of V(C,N) were observed in the tested steel:inter-phase precipitation and random precipitation. The inter-phase precipitation of V(C,N) can eliminate the enrichment of carbon in austenite, which is the pre-requisite for the formation of single phase ferrite.