Macrosegregation during the cooperative melting/solidification process of plate electrode and base metal in electroslag fusion welding: towards geometrical design standards for weld homogenization

Electroslag fusion welding (ESFW) is an advanced joining process for large-scale thick-section components, where homogenization of elemental composition in fusion welded zone is critical for joint performance. This study investigates the macrosegregation behavior of solute elements during the cooperative melting and solidification of the plate electrode and base metal in ESFW, with a focus on the influence of key geometrical parameters: assembly clearance and plate electrode width. The results show that Carbon exhibits the strongest segregation due to synergistic coupling of its low partition coefficient and large positive solut expansion coefficient, driving upward solute transport that synergizes with Lorentz-force-driven convection to accumulate carbon-rich liquid in the final solidification zone. Molybdenum and chromium show weaker segregation due to higher partition coefficients, dominated by local thermosolutal convection in the mushy zone. The 15 mm clearance with 20 mm electrode width achieves optimal carbon uniformity (segregation index dispersion: 7.98%), balancing welding efficiency and homogenization. Carbon is the primary design consideration; molybdenum and chromium are secondary, though chromium depletion at the edges of fusion welded zone requires monitoring for corrosion-critical applications. These findings establish geometric design standards for welds, and the mechanistic insights can be generalized to other electrometallurgical processes.