Influence of P2O5 on Crystallization of V-concentrating Phase in V-bearing Steelmaking Slag

Synthetic V-bearing steelmaking slag modified by Al2O3, containing three different amounts of P2O5, were heated to 1530°C and then slow cooling to 1300°C for several durations. The effect of P2O5 on the solidified slags, especially on the crystallization behaviour of V-concentraitng phase were characterized by XRD, SEM and EPMA. The results show that V is concentrated and formed into Ca3(VO4)2 in P2O5-free slag and for the samples with 1.0 wt% and 2.4 wt% P2O5, V is precipitated into a solid solution Ca3[(P, V)O4]2. Ca3(VO4)2 and Ca3[(P, V)O4]2 are both the V-concentrating phases in the modified slag. Quantitative description of the morphologic texture of grains of the V-concentrating phases was based on computer-aided image analysis. For all samples, the fitted lognormal distribution is in good agreement with the distribution in the whole grain size range. It is concluded that P2O5 accelerates the growth of V-concentrating phase and influence the morphology of V-concentrating phase and growth mechanism is surface-controlled. There exists a proper content range of P2O5 between 1–2.4% for better growth of V-concentrating phase.