Direct Evidence for Phase Transition Process of VC Precipitation from (Fe,V)3C in Low-Temperature V-Bearing Molten Iron

V-bearing molten iron was obtained by adding Na2CO3 in the smelting process of vanadium titanomagnetite at low temperature. Two forms of V-rich carbides ((Fe,V)3C, VC) were detected in the V-bearing pig iron products. Once the smelting temperature was above 1300 °C, most of the V in the raw ore was reduced into molten iron. Owning to the high content of V, the unsteady (Fe,V)3C solid solution decomposed along with the precipitation of graphite and VC during the solidification process. The presence of VC cluster and VC precursor in (Fe,V)3C was detected by transmission electron microscopy, which confirmed the possibility of this transition process at the atomic perspective. The transformation dramatically affected the compositions and properties of V-bearing pig iron and had important guiding significance for the actual production process.