1 Complex flow motions during laser welding

In this paper, we report on observations of liquid metal flow during laser welding carried out in the conduction mode. A high-speed camera was used to capture the flow motion. The flow behavior is affected by the heating source as well as material properties; the former can influence the energy density and thermal field and the latter determines the response to the thermal field gradient. The dynamic behavior of the fluid influences heat and mass transfer in the weld pool. The results from high-speed camera observations show that the flow motions can be quite complex and are dependent on the process boundary conditions. Nomenclature ia = activity of species i in solution (-) A = surface tension gradient of pure iron (N m-1 K-1