Spectral analysis of the process emission during laser welding of AISI 304 stainless steel with disk and Nd:YAG laser

Optical emissions from the laser welding process can be obtained relatively easy in real-time. Such emissions come from the melt pool, keyhole, or plume during welding. Therefore it is very beneficial to establish a clear relation between characteristics of these emissions and the resulting weld quality or the occurrence of welding defects for any of the laser type currently used in industry. Most commonly used in continuous wave (CW) laser welding applications are the CO₂ laser, Nd:YAG laser, diode, disk and fiber lasers. The disk lasers are relatively new and need to be characterized with respect to the nature of their plasma or plume generation. In this paper, the process emissions during laser welding of AISI 304 stainless steel with disk laser and Nd:YAG laser are compared. Broadband spectral analysis between 200 nm and 1100 nm reveals spectral lines as well as the black body radiation emitted from bead-on-plate welding configuration. The relation between the process emission and weld quality is discussed.