High power laser welding is widely used across various industrial fields due to its advantages such as small heat-affected zone and deep penetration capability. Upon laser irradiation of a metal, a moltenpool is formed, while part of the molten metal undergoes evaporation, generating a vapor cavity known as a capillary. Multiple internal reflections of the laser within the capillary enhance energy absorption, enabling deeper penetration. However, this process also induced the ejection of molten metal, called spatter, which can result in welding defects such as material loss, and surface irregularities. Therefore, developing effective methods to suppress spatter is essential for improving weld quality. Stabilization of both the molten pool flow and the dynamics of the capillary is considered critical for achieving spatter suppression. Previous studies have demonstrated that beam profile control during welding can enhance the stability of the molten pool and capillary, thereby reducing spatter formation. Nonetheless, the fundamental mechanisms underlying these effects remain insufficiently understood, and an optimal beam profile has yet to be established.

In this study, several laser beam profiles were engineered and applied to welding processes. The resulting flow behavior of the molten pool and the stability of the capillary were systematically compared with those obtained using a conventional Gaussian beam. The effects of beam shaping on the suppression of spatter were also examined in detail, with the aim of elucidating the correlation between beam profile geometry and melt dynamics.