Multi-keyhole separation during multi-spot laser welding of duplex steel

Abstract

Separated keyholes generated during a multi-beam laser welding process were observed, analyzed, and quantified. Two high-speed cameras were utilized to capture process phenomena of bead on plate experiments, with a near vertical and a horizontal view. The films were analyzed for: the ability to form a unique keyhole for each beam, the time and location of observed fully penetrated keyhole, and other associated trends. The number of beams was correlated to fully penetrated, separate keyholes. Keyhole separations were observed to be stable while full penetration was less regular. The location of a fully penetrating keyhole correlated with the position of the stronger beam. The dynamic melt wall width separating the keyholes was measured with beam orientation and power ratios between beams having a significant impact. Beam orientation showed that the lagging inter-keyhole wall of a quad-beam process was impacted by the presence of a fully molten front in the in-line beam arrangement. For the cross-beam orientation, the lagging wall did not seem impacted by the melt front. Large power differences between leading beams for the quad-beam, in-line orientation formed a melt column in the location of the weaker beam and spattering from the column.