Investigation of molten pool behavior and weld bead formation in VP-GTAW by numerical modelling

摘要

A three dimensional model is proposed to characterize the transport phenomena in molten pool and weld bead formation in high speed VP-GTAW. The temperature and velocity distribution, deformation of molten pool free surface and weld bead profile are systematically discussed. The molten pool temperature exhibits a periodically fluctuations (20-40 K), and the molten pool shape and velocity remain minor oscillation in the DCEN and DCEP phases. The velocity increases dramatically to 1.012 m/s at the initial stage (0-0.01 s), then the velocity remains stable as the further development of molten pool volume (0.01-0.4 s). Two forms of flow patterns driven by surface tension and electromagnetic force are dominated in the molten pool. The formation mechanisms of weld bead defects (undercut, humping) are analyzed. The simulated weld bead profiles are agree well with the experimental weld appearance. This numerical study may provide a good foundation for optimizing the VP-GTAW process to achieve quality welds. (C) 2016 Elsevier Ltd. All rights reserved.