Assessment of controlled short-circuiting application in filling passes with MIG/MAG double-wire process

Abstract

In this work, a technical–economic assessment of the double-wire MIG/MAG welding process was carried out for flat-position welding of filler passes, employing controlled short-circuiting (CSC) operating mode in the trailing wire, as a way of improving control of the molten pool and reducing splashes. The assessment was based on a comparative study between the conventional double-wire MIG/MAG technique (using pulsed current in both wires) and a combination of pulsed current in the leading wire and CSC in the trailing wire. The following were kept constant: the values of average current for each wire, the volume of material deposited per unit length of weld, the type and size of the bevel and the wire, the composition of the shielding gas and the CTWD. The surface finish and geometry of the weld beads, deposition rate and deposition efficiency and the maximum welding speeds resulting from the use of each technique were assessed. The results show that the use of the CSC mode in the trailing arc increases the production capacity of the process slightly, leads to less splashing, improves the finish of the bead, produces smaller fusion zone and smaller HAZ and yet maintains a similar operational envelope (with respect to the range of useful welding speeds), which are positive factors. On the other hand, as a disadvantage, the use of CSC led to beads that are more convex and have less penetration.

Keywords:

• Tandem GMAW
• current control
• automation

Acknowledgements

The authors would like to thank the Post-Graduate Programme of the UFU for the opportunity for carrying out this work. We also thank CNPq, FAPEMIG and CAPES, for providing a research grant and study grants (master’s). In addition, we would like to thank the Central Group for Research and Development of Welding Processes - LAPROSOLDA for making equipment and materials available, and White Martins for supplying the shielding gas.

Notes

Selected from Soldagem & Inspeção. 2015 20(1) 16–27.