Predicting onset of high speed gas metal arc weld bead defects using dimensional analysis techniques

Abstract

The onset of geometric defects such as humping or discontinuous weld beads during gas metal arc welding (GMAW) frequently limits the use of higher welding speeds and increased productivity. In the present study, a dimensional analysis of the GMAW process was performed in order to identify a number of dimensionless groups formulated based on various GMAW process parameters and material properties that could be used to predict when humping or discontinuous weld beads would occur. Experimental data from bead on plate GMA welds in plain carbon steel plate made using argon and two different reactive shielding gases, welding powers between 5 and 12 kW and a range of welding speeds were then used to create dimensionless process maps. These maps showed the limiting welding speed above which the high speed weld defects occurred as a function of all influential process parameters. It was shown that all experimental data for limiting welding speeds could be collapsed onto two collinear dimensionless curves. Also, the transition from spray to rotational metal transfer was found to occur at a well defined value of one of these dimensionless parameters. The effects of work piece preheat temperature on humping were correctly predicted and there was a good correlation between the dimensionless GMAW process map and experimental data from other independent studies. These results suggest that the occurrence of high speed weld bead defects such as humping and discontinuous weld beads as well as the transition from spray to rotational metal transfer can be predicted using these new dimensionless GMAW process maps.