It has been observed experimentally that small additions of oxygen to the argon shielding gas affect the general operation of GMAW processes. By theoretically modeling the arc column, it is shown that the addition of 2 to 5% oxygen to argon has an insignificant effect on the arc characteristics. This corresponds to the minor changes in the thermophysical transport and thermodynamic properties caused by the oxygen addition. Therefore, it is concluded that the addition of oxygen to the argon shielding gas mainly affects the anode and the cathode regions. From the literature, it was found that the formation of oxides initiates arcing at the cathode and decreases the movement of the cathode spots. These oxides can also improve the wetting conditions at the workpiece and the electrode. Finally, oxygen is found to affect the surface tension gradient and thereby the convective flow of liquid metal in the weld pool.
The voltage and power distributions in gas metal arc welding (GMAW) were studied both experimentally and numerically. The principal voltage drop takes place in the arc, which also constitutes the dominant power contribution. Within the arc, the dominating voltage contributions are from the arc column and the cathode fall, while the anode fall and the electrode regions are less significant. The power input to the arc column increases with both increasing current and increasing arc length. These results indicate that it is critical to control the arc length in order to control the power input to the system.
The majority of automotive body shop welding consists of resistance spot welding (RSW) steel sheet due to its inherently low cost and high speed. With the introduction of aluminum, it is desirable to continue using RSW as the joining process. However, the presence of insulating oxide layers on the aluminum alloy material surface presents significant problems in obtaining consistent spot welding processes. If dressing fails to completely remove the pits, it will cause the electrode surface to deteriorate more rapidly, which in turn will eventually lead to unacceptable welds. Macrodeformation of the electrode, which commonly happens in steel spot welding, does not occur for aluminum spot welding because the nugget temperatures are much lower. However, circular protrusions on the MRD electrode with their small cross sections can be susceptible to deformation or flattening during use.