Thermodynamic Nature of SiO₂ and FeO in Flux O Potential Control Subject to Submerged Arc Welding Process

SiO2 and MnO are the essential components dictating flux O potential subject to submerged arc welding. Due to the lack of thermodynamic data on the flux properties in early trials, the roles of SiO2 and FeO in the determination of the flux O potential remain nebulous, and conclusions are often conflicting with each other. Within this framework, through the analysis of the fluxes of 23 formulas at the full coverage of acid and basic fluxes with a basicity index spanning from 0.5 to 5.6, attempts are made to obtain a better understanding of the thermodynamic interconnection between oxides (SiO2 and FeO) and the flux O potential, and to clarify the controversial conclusions raised by different investigators. In particular, a thermodynamic approach has been proposed to simulate the equilibrium FeO activity, during which no measurement of the slag composition is needed. It is revealed that the simulated equilibrium FeO activity is feasible to evaluate the flux potential for both acid and basic fluxes, which may pave a vital way to save the experimental resources on the flux design and analysis.