Fundamental Phenomena in High Power CO_2 Laser Welding (Report I) : Atmospheric Laser Welding(Welding Physics, Process & Instrument)

概要

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Fundamental phenomena in high power CO_2 laser welding, including beam hole shape and peculiar plasma behavior, were observed dynamically using a transmission X-ray and high speed camera system. The effect of altering the flow rate of helium assist gas was also studied. It was found that the gas flow rate had a strong effect on the beam hole shape and plasma production, and the assist gas not only blowed away the laser plasma but also it enlarged the shape of the beam hole. Too high a flow rate of assist gas enlarged the beam hole too much to cause the failure of the wall focusing effect. In order to avoid the interference effect of laser plasma, a new laser welding process, called "Laser Spike Seam Welding", was developed based on above study on fundamental phenomena. This process allowed considerably deeper penetration than conventional laser welding. The reasons for this superiority were also analyzed by the above high speed imaging method.
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