Abstract
The behavior of the shielding gas and the beam refraction zone in the welding plasma formed during CO2 laser welding of metals were observed using the schlieren and shadowgraph imaging techniques, respectively. A visible light source was used for the schlieren observations. A stationary Gaussian-distribution-shaped gasdensity boundary was clearly seen to form on the welding pool under the Ar shielding gas. A fluid disturbance, namely, the application of a cross gas flow, extinguished the foot of the density boundary, resulting in a heavily oxidized weld bead. An infrared light source was used for the shadowgraph observation. The images showed that elliptical zones for the laser-beam refraction were produced. The schlieren and shadowgraph imaging techniques are thus effective for observing phenomena caused by the interaction between the laser beam and the shielding gas/laser-induced plasma formed on the welding pool.
