Abstract: By using the high speed camera, the arc and drop transfer behaviors of direct current electrode negative MAG welding process with different protecting atmospheres and different welding current levels are researched. The formation reason of bright arc ball and its influence on the stability of MAG welding process are analyzed. On this basis, the process interval of direct current electrode negative MAG welding is determined. Also the influences of wire polarity on wire melting coefficient are compared. By using 80%Ar plus 2%CO2 as shield gas, the drop transfer style belongs to large drop repulsion transfer, so the spatter is too large. But when the shield gas is 98%Ar plus 2%O2, the stable drop transfer style can be divided into dropwise transfer with low current and streaming transfer with large current. For the former one, with the increase of welding current, the droplet dimension reduces and the drop transfer frequency increases. For the latter one, the arc is divided into two parts in series. Both the moving domain of the bright arc ball and the stability of the welding process can be controlled by adjustment of arc voltage.

Key words: Bright arc ball, Direct current electrode negative, Streaming transfer, Wire melting coefficient