Visualisation of alternating shielding gas flow in GTAW

Ioannis Bitharas*, S. W. Campbell, A. M. Galloway, N. A. McPherson, Andrew J Moore

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)
155 Downloads (Pure)


The alternating shielding gas technique is a method of achieving transient arc characteristics during arc welding; however the complex flow that occurs through its use has not been investigated previously. A schlieren system was used to image density gradients that arise when alternating argon and helium shield gases, under varying flow parameters, with gas tungsten arc welding (GTAW). A theoretical analysis was carried out to determine the conditions under which the technique facilitates arc pulsing, in particular to avoid mixing of the shield gases in the delivery pipe prior to the welding nozzle. At appropriate pulsing frequency and flow rates, a stable horizontal region of helium was observed in the weld region, maintained in position by the denser argon from the preceding pulse. This higher than average mass fraction of helium when applying the shielding gases alternately, compared to a premixed gas with the same volume of argon and helium, increased the weld penetration by 13% on average, suggesting a modest improvement in heat transfer.

Original languageEnglish
Pages (from-to)424-431
Number of pages8
JournalMaterials and Design
Publication statusPublished - 5 Feb 2016


  • Alternating
  • Gases
  • GTAW
  • Schlieren
  • Shielding
  • Visualisation

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Science(all)


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