Visualisation of alternating shielding gas flow in GTAW

Ioannis Bitharas, Stuart Campbell, Alexander Galloway, Norman McPherson, A.J. Moore

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

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 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 obseved 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, compare 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.
LanguageEnglish
Pages424-431
Number of pages8
JournalMaterials and Design
Volume91
Early online date2 Dec 2015
DOIs
Publication statusPublished - 5 Feb 2016

Fingerprint

Tungsten
Electric arc welding
Shielding
Flow of gases
Helium
Visualization
Gases
Argon
Welds
Schlieren systems
Nozzles
Welding
Pipe
Flow rate
Heat transfer

Keywords

  • GTAW
  • alternating shielding gases
  • Schlieren visualisation

Cite this

Bitharas, Ioannis ; Campbell, Stuart ; Galloway, Alexander ; McPherson, Norman ; Moore, A.J. / Visualisation of alternating shielding gas flow in GTAW. In: Materials and Design. 2016 ; Vol. 91. pp. 424-431.
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Visualisation of alternating shielding gas flow in GTAW. / Bitharas, Ioannis; Campbell, Stuart; Galloway, Alexander; McPherson, Norman; Moore, A.J.

In: Materials and Design, Vol. 91, 05.02.2016, p. 424-431.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Visualisation of alternating shielding gas flow in GTAW

AU - Bitharas, Ioannis

AU - Campbell, Stuart

AU - Galloway, Alexander

AU - McPherson, Norman

AU - Moore, A.J.

PY - 2016/2/5

Y1 - 2016/2/5

N2 - 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 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 obseved 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, compare 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.

AB - 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 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 obseved 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, compare 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.

KW - GTAW

KW - alternating shielding gases

KW - Schlieren visualisation

U2 - 10.1016/j.matdes.2015.11.085

DO - 10.1016/j.matdes.2015.11.085

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JO - Materials & Design

T2 - Materials & Design

JF - Materials & Design

SN - 0261-3069

ER -