Abstract
The oscillation arc assisted by an extra alternating longitudinal magnetic field (LMF) in narrow gap tungsten arc welding is proved to be effective in avoiding welding defects due to insufficient fusion at the side walls in joining thick wall plates. The behavior of the welding arc and molten pool under the LMF is simulated to reveal the influence of the LMF on the formation of a uniform penetration weld bead. A unified mathematical model was developed for the narrow gap tungsten arc welding including the plasma arc, molten pool, electrode, and their interactions. Under the LMF, the whole welding arc is deflected and oscillates between the two side walls. When the magnetic-field strength is larger than 6 mT, the axis of the arc deflects to the side wall; the maximum value of heat flux at the bottom decreases by one-half, and the maximum value at the side wall is increased by a factor of ten. On the other hand, under the LMF, the forces acting on the molten pool are changed; the fluid flow pattern is helpful to increase the heat transferred to the side walls. The model is validated by experimental results. Both the percentage deviations of the simulation weld penetration at the side wall and at the bottom from the experimental results are lower than 10%.
Highlights
Thick wall plates are widely applied in marine, energies, transport industries, and so on
For the additional source term in Equation (3), the enthalpy transport of electron and the radiation loss were added to the welding arc zone, the latent heat of fusion was added to the weld pool, and the additional source terms were expressed as Equations (6) and (7)
The weld formation is mainly decided by the heat flux and forces of the welding arc
Summary
Thick wall plates are widely applied in marine, energies, transport industries, and so on. Developed a novel double welding; the distribution of arc pressure and heat is more reasonably between the bottom and side magnetic pole system for narrow gap welding to produce more uniform magnetic-field lines [13,14,15]. Used the LMF in low-frequency pulse narrow gap welding; the distribution of welding (LMF-NG-GTAW) are mainly focused on the characteristics of the weld shape under arc pressure and heat is more reasonably between the bottom and side wall of the narrow groove. NG-GTAW, is essential to such as the current density, heat flux, and fluid flow [17,18,19], and all these factors have a critical study the heating characteristics of the magnetically oscillation arc (MOA) and the fluid flow in the influence on In thethis weld formation. The model is validated by using the experimental data from references
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