Effect of vanadium on the fatigue properties of microalloyed medium-carbon steels

The fatigue properties of vanadium-microalloyed ferrite-pearlite steel 38MnVS and steel 38MnS at different states were studied by using rotating-bending fatigue test. The results show that vanadium can improve the fatigue properties of ferrite-pearlite steel mainly through precipitation strengthening and grain refining mechanism. TEM examination shows that in the as-hot forged state, the fine V(C, N) particles with about 4 nm in diameter have specific orientation relationship with ferrite matrix and significant effect on precipitation strengthening and microstructure refinement. The strengthening effect of soft ferrite raised the slip band initiation stress and delayed crack initiation, the fatigue property of the as-hot forged steel 38MnVS is much higher than that of steel 38MnS. In the as-annealed state, the initial fine V(C, N) particles coarsen and are incoherent with ferrite matrix, and have little effect on precipitation strengthening. Therefore, the fatigue property of the as-annealed steel 38MnVS is lower than that of the as-hot forged and is comparable to that of the steel 38MnS.