Silicate Island Formation in Gas Metal Arc Welding

Because formation of silicate islands during gas metal arc welding is undesirable due to decreased productivity and decreased quality of welds, it is important to understand the mechanism of the formation of these silicate islands to mitigate their presence in the weld. The effects of welding parameters on the silicate formation rate were studied. Results showed that the applied voltage and oxidizing potential of the shielding gas were the parameters that most strongly influenced the amount of silicates formed on the surface of the weld bead. High-speed video was used to observe the formation of silicate islands during the welding process, which showed that the silicates were present at each stage of the welding process, including the initial melting of the wire electrode, and grew by coalescence. A flow pattern of the silicate islands was also proposed based on video analysis. An electromagnetic levitation system was used to study the growth kinetics of the silicate islands. Silicate coverage rate was found to increase with increasing oxidizing time, increasing oxidizing potential of the atmosphere, and increasing content of alloying elements except for Ti.