Narrow gap welding has advantages over conventional V-grooved butt welding such as high productivity, small deformation and high mechanical property. Therefore, with narrower groove gap, less arc heat input is expected with all the other advantages of narrow gap welding. The main defects of narrow gap welding include lack of root fusion, convex bead surface and irregular surface, all of which have negative effects on next pass welding operation.
This paper suggests a up-and-down torch oscillation for ultra narrow gap welding with gap size less than 5mm and finds out proper welding condition from welding parameters to fulfill reliable high quality welding.
At first, as ultra narrow gap welding system modeling, GMA welder model was suggested with Halmoy’s model referenced for wire melting modeling. And the arc length in ultra narrow gap was defined.
Then, based on the experiment results of up-and-down torch oscillation welding, simulation results on the torch oscillation, phase shift of current and wire extension length on varying oscillation frequency were analyzed to show that weld bead shape in ultra narrow gap can be predicted.
Finally electromagnetic up-and-down torch oscillation system was suggested one of ultra narrow gap welding process.
As a result, it was confirmed that reliable weld quality in ultra narrow gap welding can be achieved with up-and-down torch oscillation above 15Hz due to its ability to provide uniform heat input along the sidewall of gap, which provided.
