Limitations of the Schlieren technique for shielding gas flow visualization in arc welding processes


Gas protection is very important in arc welding processes and several factors influence its effectiveness. This paper provides a discussion of the applicability of the Schlieren technique to arc welding processes. Tests were performed with different types of shielding gas and with GMAW and GTAW torches, in order to highlight differences associated with the various conditions. The results obtained in conjunction with a review of results reported in the literature allowed an evaluation of the limitations associated with the use of the Schlieren technique in the arc welding processes. The most important limitation is that the visualization is inherently difficult when using pure Ar gas, meaning that in most situations it is not possible to adequately visualize the flow interface with atmospheric air, which is the main region of interest in this type of analysis. However, visualization is possible in regions where pure Ar is heated, or when mixtures with other gases are used. In addition, the results obtained with different sources of light were compared and the test was performed by filming the arc welding or with the gas flowing through the torch without the arc. The differences observed in the results obtained are discussed herein.

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The authors are grateful to the LABSOLDA team, POSMEC, and UFSC.


We also acknowledge the Brazilian research funding agencies CNPq and Petrobras, which subsidized the research through the acquisition of equipment and granting of scholarships.

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Correspondence to Álisson Fernandes da Rosa.

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Recommended for publication by Commission XII - Arc Welding Processes and Production Systems

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Schwedersky, M.B., da Rosa, Á.F., Okuyama, M.P. et al. Limitations of the Schlieren technique for shielding gas flow visualization in arc welding processes. Weld World (2021).

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  • Shielding gas
  • High speed filming
  • LED
  • Laser