The paper entitled "Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds" by Maria Asuncion Valiente Bermejo and her colleagues at University West: L. Karlsson, L-E. Svensson and K. Hurtig and with the support of H. Rasmuson (ESAB AB), M. Frodigh (Sandvik Materials Technology) and P. Bengtsson (AGA Gas AB) was published on-line first in Welding in the World on the 29th of October 2014. The full paper is available at http://link.springer.com/article/10.1007/s40194-014-0199-7 and it was published in vol. 59, n.2, pp. 239-249.
Here you have the summary:
The influence of shielding gases on welding performance and on properties of duplex and superduplex stainless steel welds was studied. Using argon as the reference gas, helium, nitrogen and carbon dioxide were added and five mixtures evaluated. Bead-on-plate welds and circumferential
pipe welds were produced using mechanised GMA welding in the downhand position. Welding performance, corrosion resistance,mechanical properties, microstructural features and weld imperfections were assessed and related to the shielding gas. Shielding gases containing 30 % helium showed excellent results; whilst pure argon showed unstable arc and poor weld pool fluidity and Ar+2 %CO2 resulted in underfill and porosity. Mixtures containing helium resulted in higher ductility
welds and higher impact toughness values than welds produced with Ar+2 %CO2. Sound and balanced duplex microstructures free from intermetallics were found with suitable ferrite contents for all the shielding gases studied. All the duplex pipe welds passed the corrosion test regardless of the
shielding gas used, and the best results in the corrosion test for superduplex pipe welds were found when using Ar+30 %He+0.5 %CO2+1.8 %N2 as shielding gas.
pipe welds were produced using mechanised GMA welding in the downhand position. Welding performance, corrosion resistance,mechanical properties, microstructural features and weld imperfections were assessed and related to the shielding gas. Shielding gases containing 30 % helium showed excellent results; whilst pure argon showed unstable arc and poor weld pool fluidity and Ar+2 %CO2 resulted in underfill and porosity. Mixtures containing helium resulted in higher ductility
welds and higher impact toughness values than welds produced with Ar+2 %CO2. Sound and balanced duplex microstructures free from intermetallics were found with suitable ferrite contents for all the shielding gases studied. All the duplex pipe welds passed the corrosion test regardless of the
shielding gas used, and the best results in the corrosion test for superduplex pipe welds were found when using Ar+30 %He+0.5 %CO2+1.8 %N2 as shielding gas.