Abstract
The acoustic radiation force driving the plasma jet and the ultrasound reflection at the plasma arc-weld pool interface are considered to modify the formulas of gas shear stress and plasma arc pressure on the anode surface in ultrasonic-assisted plasma arc welding (U-PAW). A transient model taking into account the dynamic changes of heat flux, gas shear stress, and arc pressure on the keyhole wall is developed. The keyhole and weld pool behaviors are numerically simulated to predict the heat transfer and fluid flow in the weld pool and dynamic keyhole evolution process. The model is experimentally validated. The simulation results show that the acoustic radiation force increases the plasma arc velocity, and then increases both the plasma arc pressure and the gas shear stress on the keyhole wall, so that the keyholing capability is enhanced in U-PAW.
Highlights
Plasma arc welding (PAW) can form a keyhole channel inside the weld pool along the plate thickness, and join materials of mid-thickness in a single pass [1]
The stability of the weld pool and keyhole is the prerequisite for obtaining a large penetration and good weld quality [2]
In the PAW process, the dynamic stability of the weld pool and keyhole is poor, and the welding process-parameter window is narrow, which restricts its wider applications in the industry [3,4]
Summary
Plasma arc welding (PAW) can form a keyhole channel inside the weld pool along the plate thickness, and join materials of mid-thickness in a single pass [1]. To study the process mechanism of U-PAW, Wu et al [5] conducted experiments under different welding process parameters, and found that by the application of ultrasonic vibration, the plasma arc pressure is increased, so that an open keyhole can be formed at a higher welding velocity or lower welding current in U-PAW. Density of Ar (kg/m3) Adjusting constant (N) Plasma gas flow rate (L/min) Conversion coefficient Nozzle diameter (mm) Distance from electrode to workpiece (m) Shielding gas flow rate (L/min) Sound velocity of argon (m/s) Adjusting constant (N) Vibration frequency (KHz) Vibration amplitude (μm) Nozzle exit area (m2)
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