Effect of the shield gas, working angles and displacement angles on the characteristics of fillet joints obtained via GMAW using a high-strength microalloyed steel

ABSTRACT

Fillet joints are one of the most commonly used joints in various industries, in particular for agricultural machinery. However, the complexity of the pieces that require welding often makes accessibility difficult for the welder for this kind of joint, and working and displacement angles are important aspects to be evaluated. In addition, in the GMAW process, the use of the Ar-20%CO₂ mixture as the shield gas has increased at the expense of 100% CO₂, generally requiring an adjustment of the electrical parameters. On the other hand, the incorporation of new materials with higher strength also involves optimizing the welding procedure. The aim of this study was to evaluate the effect of two shield gases (Ar-20% CO₂ and 100% CO₂), three working angles (30, 45 and 60°) and two displacement angles (45° using the push technique and 60° using the pull technique) on the dimensional characteristics of the seam and the mechanical strength of the fillet joint from a microalloyed steel with high strength welded using GMAW. The highest levels of penetration corresponded to the test specimens welded using the pull technique and with CO₂. The over thickness was smaller for conditions with the push technique and the gas mixture. The microhardness of the weld metal, for a similar working angle, was higher for the gas mixture in all cases. Indices of acceptability were developed, which graded geometric aspects and these were compared with the mechanical properties obtained on the welds, showing a good correlation.

KEYWORDS:

• GMAW
• fillet weld
• shield gas
• working and displacement angle
• microalloyed steel

Acknowledgments

The authors would like to thank Laboratorios de Metalografía y de Ensayos de Materiales de la Escuela de Educación Secundaria Técnica N° 1 “Antonio Bermejo” for performing the breaking tests. They would also like to thank Universidad Tecnológica Nacional and UNNOBA for their financial support.