Assisting Gas Optimization in CO2 Laser Welding

Hui Gong, Flemming Ove Olsen

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


    High quality laser welding is achieved under the condition of optimizing all process parameters. Assisting gas plays an important role for sound welds. In the conventional welding process assisting gas is used as a shielding gas to prevent that the weld seam oxidates. In the laser welding process assisting gas is also needed to control the laser induced plasma.Assisting gas is one of the most important parameters in the laser welding process. It is responsible for obtaining a quality weld which is characterized by deep penetration, no interior imperfections, i.e. porosity, no crack, homogeneous seam surface, etc. In this work a specially designed flexible off-axis nozzle capable of adjusting the angle of the nozzle, the diameter of the nozzle, and the distance between the nozzle end and the welding zone is tested. In addition to the nozzle parameters three gases, Nitrogen, Argon, and Helium are applied with three different flow rates for each of the gases. A number of systematic laboratory experiments is carried out by employing various experimental designs, 33 and 32 Factorial Design. In the experiments a CO2 laser is used to weld thin sheets of mild steel. The welding specimens are evaluated by a number of quality characteristics, such as the seam depth and seam width. The significance of the gas parameters and their interactions are based on the data found by the Analysis of Variance, ANOVA.In order to investigate the possibility of automatic optimizing the welding process, a couple of photo diodes are applied to monitor the welding process. These two photo diodes are arranged in two different viewing angles. The couple of photo diode signals are translated by a data acquisition card and stored in a computer. The photo diode signals are further analyzed with FFT frequency analysis. The relations between the gas parameters and signal frequencies are studied. Finally the relationships of the gas parameters and weld characteristics are studied. The possibility of using photo diode signals in controlling the gas parameters is discussed.KeywordsCO2 laser welding, assisting gas parameters, factorial design, photo diode signals.
    Original languageEnglish
    Title of host publicationProceedings 6th Welding
    Place of PublicationNagoya
    PublisherKyroki Publishing Co.
    Publication date1996
    Publication statusPublished - 1996
    Event6th Welding Society - Nagoya, Japan
    Duration: 1 Jan 1996 → …


    Conference6th Welding Society
    CityNagoya, Japan
    Period01/01/1996 → …

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