Visualisation and optimisation of shielding gas coverage during gas metal arc welding

Ioannis Bitharas, N. A. McPherson, W. McGhie, D. Roy, Andrew J. Moore

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Abstract

The density gradients and flow characteristics of the gas shield during gas metal arc welding (GMAW) of DH36, higher strength ‘construction steel’ were visualised using schlieren imaging. A systematic study was undertaken to determine the effect of shielding gas flow rate, as well as changes in the nozzle stand-off and angle, on the weld quality. The schlieren images were used to validate 2D and 3D magnetohydrodynamic (MHD) finite element models of the interaction between the Ar shielding gas, the arc and the ambient atmosphere. Weld porosity levels were determined through x-ray radiography. Sufficient shielding gas coverage was provided at a minimum of 9 l/min pure Ar, irrespective of relatively large increases in the nozzle stand-off and angle. Using 80% Ar/20% CO2 shielding gas, and 86% Ar/12% CO2/2% O2 shielding gas with flux cored arc welding (FCAW-G), achieved good quality welds down to 5 l/min. The introduction of 12 l/min in production welding has been implemented with no compromise in the weld quality and further reductions are feasible.

Original languageEnglish
Pages (from-to)451-462
Number of pages12
JournalJournal of Materials Processing Technology
Volume255
Early online date2 Dec 2017
DOIs
Publication statusPublished - May 2018

Keywords

  • FCAW-G
  • Finite element modelling
  • Magnetohydrodynamics
  • Schlieren
  • Shielding gas
  • Visualisation

ASJC Scopus subject areas

  • Ceramics and Composites
  • Computer Science Applications
  • Metals and Alloys
  • Industrial and Manufacturing Engineering

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