Influence of oxides on cold lap formation in tandem GMAW

Abstract

The connection between the formation of cold laps and the presence of Mn–Si oxides was studied. The underlying purpose is to understand the fundamental mechanisms of cold lap formation and to avoid it. Tandem gas metal arc welding (GMAW) was used to produce welded specimens in two different shielding gases (pure Ar and pure CO₂) with base metal S355 MC (EN-10149-2) and wire G3Si1 (EN ISO 14341-A). Cross-sections of welds in the cold lap location were evaluated by light optical microscopy and scanning electron microscopy combined with energy dispersive spectroscopy. The results showed that the Mn–Si oxides significantly enhanced cold laps formation, especially the overlap type cold lap formation. The Mn–Si oxides originated from oxidation of the droplets. These oxides transfers to the surface of the weld pool at the weld toe, where they contributed to the formation of the cold laps.

Keywords:

• Tandem GMAW
• Oxides
• Cold lap
• Formation
• Droplet

This study has been supported by WIQ projects which are funded by the VINNOVA Foundation. The authors would like to acknowledge Volvo CE for support and help. Thanks also go to Mr Kjell Hurtig and Mr Tore Ronnhult for help in the experimental tasks.