SiO2(l) + 2CaF2(g) ↔ 2CaO(s) + SiF4(g) (1) H2O(g) + CaF2(g) ↔ CaO(s) +2HF(g) (2) The empirically determined trend of flux basicity (BI) vs. ppm O in the weld metal is generally used to design fluxes for the target oxygen content in the weld metal. The BI ...