Stabilization of molten pool flow and keyhole capillary behavior through beam shaping in high-power laser welding of stainless steel

High-power laser welding is widely used due to its ability to achieve deep penetration with a small heat-affected zone. However, this process often leads to spatter, caused by the interaction between unstable keyhole capillary behavior and metal vapor ejection, which can result in welding defects such as pits and material loss. Stabilizing the keyhole capillary is, thus, essential for spatter suppression. This study investigates the effect of keyhole capillary stabilization using a 3spot laser profile, in which a high-power central laser is combined with low-power preheating and postheating lasers positioned at the forward and back. Welding experiments were conducted using this configuration, and the results were compared with those obtained from conventional single-spot laser beams. The mechanism by which beam profile control using a 3spot laser contributes to spatter reduction is elucidated in this study.