Controlling weld geometry during heat conduction mode laser beam welding by surface active elements

An important transport phenomenon determining the weld shape and its geometry in heat conduction mode laser beam welding is the convective heat transfer within the molten zone. Surface tension gradients at the free melt pool surface are the major factor driving these flows which may be significantly affected by some trace elements, thereby changing the magnitude and direction of fluid motion. Thus, it is possible to influence the resultant seam shape by controlling quantity and kind of such elements. However, this methodology requires a fundamental under standing of the interactions between welding variables and surface tension gradients. Numerical models enable a computation of temperature and velocity fields in melt pools and provide an useful tool to systematically study such phenomena in detail. So, theoretical conclusions can be made about suitable concentrations of surface active elements for increasing the welding process efficiency.