Research On The Behavior Of Non-conjugated Pool In Tandem Narrow Gap GMAW

Tandem narrow gap GMA welding method has been widely used in welding industry because it has higher efficiency, wider range of welding thickness, better forming characteristics. Although the actual welding process can be analyzed by the internal metal flow with photo of cross-sectional and longitudinal section, these are limited to some certain positions and the surface of liquid metal at a time. This paper relied on numerical simulation in order to make a continuous analysis of the metal flow and forming mechanism in the pool during the welding process. Through the Flow-3D software, different behavior of double-molten-pool mode and non-conjugated GMAW process were studied.According to mathematical formulas, this paper established a welding process numerical model. The model was divided into thermal model, quality model and momentum model. This paper selected and explained the rationality of double ellipsoid heat sources by comparing different heat distribution models. Deflection of heat source made the model be consistent with the actual welding process. This paper focused on the effects of arc pressure and electromagnetic on the weld pool behavior. Simulation results and actual weld characteristics were compared to verify the reasonableness of the model.In the range of tandem narrow gap GMAW, this paper analyzed variation with pulsed peak voltage, welding speed, wire feed speed, weld bead geometry symmetry. Welding defects such as lack of fusion, undercut, slag appeared in the welding process. Combined with changes in welding parameters, this paper made macro explanation for welding defects.Welding parameters were simulated in single molten pool mode and a non-conjugated pool behavior conditions. Through the patterns and trends of metal flow field, this paper analyzed main factors in different spatial locations under different parameters. Through longitudinal and the cross section of the metal, this paper indicated the reasons for microscopic defects.Comparing test results and simulation results in forming quality, welding parameter adjustment range, the stability of the welding process, welding defects, this paper made comprehensive analysis of the advantages and disadvantages in two modes.