In the first report, stabilizing effects of a CO_2 laser on a TIG arc behavior were discussed from the point of the arc voltage and of the interaction between the arc and the laser plume.In this report, the CO_2 laser beam was scanned by a beam oscillator, and the shapes of melted parts of the base metal were investigated. Furthermore, the behavior of a TIG arc with a scanning CO_2 laser beam was investigated by high speed video-pictures. The main experimental conditions were as follows. The TIG arc current, the laser output, the scanning frequency and the scanning width of a laser beam, the traveling speed of a SUS304 base metal and the distance between the base metal and a tungsten electrode were 100 A (DCEN), 2 kw, 25 Hz, 8 mm, 20 mm/s and 15 mm, respectively.As a result, the arc could be controlled by the scanning laser beam, and wide and shallow beads were made using this method under the suitable conditions. Therefore, it was found that the arc with scanning laser beam is excellent as heat source for surface treatment.On the other hand, the arc voltage and the range of its change decreased according as the scanning frequency increased from 5 Hz to 20 Hz. According to the observation using high speed video-pictures, the arc went straight forwards from the electrode and bent toward the scanning laser plume, and the bending point of the arc became increasingly far from the tip of the electrode when the scanning frequency increased. It would be considered that the arc voltage was affected by the bending point of the arc column because of the arc stiffness.
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