Unsteady Marangoni Flow in a Molten Pool When Welding Dissimilar Metals

The unsteady variations of transport processes in molten pools when welding dissimilar metals are systematically investigated. Convection is driven by Marangoni forces with different directions and magnitudes on a flat free surface. For a clear description without loss of generality, three-dimensional quasi-steady welding is stimulated by an unsteady two-dimensional process. Applying the volume of fluid (VOF) and enthalpy methods to determine the interfaces between the immiscible dissimilar metals and between solid and liquid, the computed results show in detail the unsteady variations in the velocity and temperature fields, the solute concentration on the free surface, and the shapes of the molten regions affected by varying the signs and magnitudes of the surface-tension coefficients. The predicted shapes of the fusion-zone and solute distributions agree with the available experimental results in welding iron to aluminum, copper and iron, and copper to nickle.