Monitoring of laser welding by optical emission spectroscopy

The suitability of optical emission spectroscopy to monitor the laser welding process online is discussed in this paper. Optical emission spectra were recorded from the plume formed during carbon dioxide laser welding of AISI 316 steel sheets. Experiments were carried out for different laser powers. The intensities of spectral lines of different elements (e.g., Cr, Fe and Ni) were found to be in good correlation with the laser power. The intensity of a spectral line was identified as a simple empirical parameter to measure laser power used in the welding process. Normalising the intensity by taking its ratio with the intensity recorded at a standard power (e.g., 500 W) helped to reduce the errors due to the measurement geometry.