Monitoring of keyhole entrance and molten pool with quality analysis during adjustable ring mode laser welding

The process monitoring of the top side and the evaluation of surface quality were applied in adjustable ring mode (ARM) laser welding of 316 stainless steel by using visual monitoring and confocal sensor technology. Experiments were conducted in different power arrangements of an ARM laser. In this study, the process status was evaluated based on the area of keyhole entrance and the width of the pool. The geometric characteristics of the topside weld were measured by a confocal sensor. The shape of the fusion zone was analyzed based on its cross section. The process mechanism of a different mode of ARM laser welding was investigated by analyzing the process status and geometric characteristics of the surface bead. Experimental results showed that dual-mode laser welding could stabilize the keyhole entrance with a uniform weld surface formation in comparison to the pure ring-mode laser weld. The dual-mode laser also generated a wider molten pool with a wider fusion zone than the pure center laser weld.