<p>Previous studies on element transfer behavior during submerged arc welding (SAW) have been constrained by underdeveloped arc characterization techniques beneath fluxes coverage, leading to a predominant reliance on empirical correlations based on oxygen potential that obscure accurate tracing of alloying element transfer pathways. To address such technical challenge, an experimental methodology integrating spectral diagnostics, droplet collection, and metal composition analysis has been designed and deployed, enabling an unambiguous yet efficient identification of possible mechanisms. The results demonstrate the presence of Ca I and Ca II in the arc plasma, and the Ca content in the droplets increases from 0 to 0.0452 wt pct with the increase CaO content in the fluxes. However, no detectable Ca has been found in the weld metal. Such findings indicate that Ca present in the arc is lost from the weld pool following transfer into the droplets, negating the long-held hypothesis that CaO remains inactive in element transfer due to high thermal stability and calling into question the assumption of thermodynamic equilibrium during SAW. Our discoveries could facilitate a critical reassessment of the applicability of oxygen potential in welding processes and advance the conceptual framework from a thermodynamic perspective to one centered on plasma-metal reaction mechanisms.</p>