Towards monitoring laser welding process via a coaxial pyrometer

摘要

The sensing and controlling of weld metrics, such as weld bead width, depth of penetration and defects, are important for adopting laser welding technology into the industry to meet the increasing demands on product quality. In this research, a weld monitoring system for laser welding is designed using a coaxial infrared pyrometer. Welds with different geometries are induced by stepwise modulation of laser power in bead-on-plate welds at three different beam diameters. The temperature signal calculated from coaxial infrared radiation are successfully correlated to weld width and penetration depth, measured by cross-sectional optical microscopy. Moreover, the temperature signal can be used as a direct indicator of welding transition mode between conduction and keyhole. The monitor is also capable of tracking geometric defects during laser welding. The use of coaxial infrared radiation can be a promising tool for the on-line detection and control of weld metrics, hence, to improve weld quality.