Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

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%.

The Effect of an External Magnetic Field on the Aspect Ratio and Heat Input of Gas-Metal-Arc-Welded AZ31B Alloy Weld Joints Using a Response Surface Methodology

“…Theoretically, the process parameters were optimized using the software tool "optimizer," which is available in Minitab (17, State college, PA, USA), with the objective function as the aspect ratio (AR) to be minimized, as shown in Equation 22, keeping an eye on the heat factor, as shown in Equation (23). The corresponding inputs are shown in Equation (24).…”

“…given 90 ≤ M ≥ 150, 5.0 ≤ F ≥ 7.0, 500 ≤ S ≥ 700, 9 ≤ G ≥ 13 (24) The predicted and optimized results of the process parameters using the response "optimizer" tool were M as 119 G, F as 5.8 m/min, S as 700 mm/min, and G as 11.5 L/min. The predicted responses were 0.8 for the HI f , and 2.4 for the AR.…”

“…The EMF influenced the weld metal's surface, thus increasing the effective contact area and the stability of the welding process was improved. As the magnetic field strength incrementally increases, the resultant force is increased, and the deflecting magnitude of the welding arc also increases [24]. Reddy et al [25] adroitly demonstrated the effect of an external magnetic field on grain refinement in gas tungsten arc (GTA) welding.…”

Molten Pool Behaviors in Double-Sided Pulsed GMAW of T-Joint: A Numerical Study

“…Meng et al and Pan et al investigated the origin of humping [34,35] and undercut [35] defects during GTA welding. Then, the influencing mechanisms of vibration [36], double electrode [37], ultrasonic waves [38], magnetic fields [39], and gravity [40] on the molten pool flow were simulated and visualized. With the understanding of the complex flow behaviors in various conditions established, predicting or optimizing the welding process also becomes possible.…”

Modeling of Melt Flow and Heat Transfer in Stationary Gas Tungsten Arc Welding with Vertical and Tilted Torches

“…Gas tungsten arc welding (GTAW) is a joining method used widely in industry. A good deal of research is available to explore the process, either through experiments or computer simulations [1][2][3][4][5][6]. Since the process is highly transient, computer simulation is therefore helpful to understand its complete physics [7][8][9][10][11][12][13].…”