Reducing dephosphorization of SiMn alloy melt and suppression of phosphine (PH3) gas emission

Abstract

The dephosphorization (de-P) efficiency of SiMn alloy melt using CaO-CaF2 flux was measured at 1823 K under a strongly reducing atmosphere. De-P efficiency increased by increasing the CaO content up to CaO saturation point in the CaO-CaF2 flux at 1823 K, indicating that the phosphorus was removed from the SiMn melt by the reducing refining mechanism. When the Vee ratio (= CaO/SiO2) of the reducing de-P slags is greater than about 1.35, the lime and dicalcium silicate phases precipitated during solidification, resulting in an increase in the emission rate of PH3 gas due to an increase in the reaction area. However, when the Vee ratio of the slags is lower than about 1.35, the fluorite, cristobalite, and wollastonite phases appeared from the phase diagram, resulting in less amount of PH3 emission during cooling because the reaction between Ca3P2 and H2O was restricted to the surface of bulk slag. © Avestia Publishing, 2017.