The experimental studies on galvanized steel were conducted for the quality monitoring of laser welding based on the principle of the emission spectroscopic techniques. Several welding defects such as bead separation, underfill, and burn-through were investigated in detail. A high resolution spectrometer was used to analyze spectral data originated from the plasma plume induced by CO2 laser. Among the ultra violet spectrum of the plasma plume of the galvanized steel, neutral zinc lines were selected to investigate the plasma plume behavior because zinc vapors play an important role in the zinc-coated steel welding. Each spectral signal was correlated with the welding quality. The transitional features of the signal were founded near the area where the defects begin to occur in each case. Electron temperature and standard deviation of neutral zinc line were the crucial factors to monitor the defects.

Topics
Lasers, Transition metals, Plasma sources, Fracture mechanics, Spectroscopy, Welding
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