THE INFLUENCE OF OXYGEN ADDITIONS ON ARGON-SHIELDED GAS METAL ARC-WELDING PROCESSES

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 addit ion of 2 to 5% oxygen to argon has an insignificant effect on the arc characteristics. This corresponds to the minor changes in the thermoph ysical transport and thermodynamic properties caused by the oxygen add ition. Therefore, it is concluded that the addition of oxygen to the a rgon shielding gas mainly affects the anode and the cathode regions. F rom the literature, it was found that the formation of oxides initiate s arcing at the cathode and decreases the movement of the cathode spot s. These oxides can also improve the wetting conditions at the workpie ce and the electrode. Finally, oxygen is found to affect the surface t ension gradient and thereby the convective flow of liquid metal in the weld pool.