Mode of metal transfer is essential variable for quality of welding. Welding gas is one of the main factors affecting metal transfer behavior for GMAW process. Recently, some gas providers have developed by adding oxygen into Ar/CO2 gas mixture to improve welding performance. However the effect of oxygen addition on metal transfer behavior has not been demonstrated and clarified. This research aims to study the influence of Oxygen, on modes of metal transfer and transition currents. In this study, the effect of welding currents and various types of welding gases were also investigated. The welding currents used were ranged from 90 to 310 ampere. Ten categories of welding gases involved in this study were divided into 2 groups, Ar/5%CO2 and Ar/15%CO2. Oxygen gas was added into each group ranging from 0% to 4%. Behaviors and modes of metal transfer were observed by using high speed camera. Rate of metal transfer, droplet size and transition current were measured. The results showed that with 1 – 2% oxygen addition short circuit/globular and globular/spray transition currents can be reached at lower welding current comparing with those of conventional Ar/5%CO2 and Ar/15%CO2 , (no oxygen addition). However excessive amount of oxygen in gas mixtures could increase both short circuit/globular and globular/spray transition currents especially in Ar/5%CO2.
Keywords:
Modes of metal transfer, Gas mixture, Oxygen addintion, Transition current.
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