Influence of Oxygen Content upon Molten Pool Dynamics in Submerged Arc Welding

In submerged arc welding, complex oxygen transport from the flux critically governs molten-pool dynamics by altering surface tension, yet the underlying mechanisms remain poorly understood. This study addresses this critical gap by developing a comprehensive numerical framework that, for the first time, couples a multi-pathway oxygen transport model with dynamic, region-specific surface tension calculations. Analysis of simulation results across varying oxygen levels reveals that the specific oxygen level dictates the competition between centrifugal spreading and centripetal return flows. Under low oxygen conditions, spreading flow dominates, resulting in a wider molten pool. Conversely, as oxygen content increases, Marangoni convection reverses: outward spreading flow diminishes while centripetal flow intensifies, leading to a significant contraction in the molten pool width. Furthermore, higher oxygen content induces an internal vortex that drives deeper penetration and delays solidification at the rear. This work elucidates the mechanism governing the transition in flow patterns driven by oxygen content and provides a physical basis for controlling weld formation by regulating the flux oxygen supply.