Numerical Investigation On The Dynamic Behavior Of Molten Pool And Its Interaction With Weld Penetration Depth In Pulsed Arc Welding

As the application of welding automation technology becomes more and more widespread,there is an urgent need to control the weld penetration in the automated production process.A 3D transient numerical model with a Gaussian surface heat source was established based on the volume of fluid(VOF)method to study the dynamic behavior of free weld pool surface in a stationary pulsed gas tungsten arc welding(GTAW)and gas metal arc welding(GMAW).The model is a multiphase flow model which takes air and welded metal into account.Through the programming language C,Fluent was redeveloped to improve the loading of force and heat source,and to input more accurate thermal and physical properties of materials during the calculation,so that the model would be closer to the actual welding situation.The temperature field and flow field of weld pool were then solved.The free surface of weld pool was tracked by the VOF method to obtain the continuous behaviors of weld pool surface along with time.Based on the analysis and verification of weld pool model,the solution of pulsed GTAW pool was given,and the temperature field and flow field of the weld pool were compared.The relationship between the oscillating frequency and the weld size were discussed qualitatively and quantitatively.Experimental results showed that the oscillating frequency of molten pool decreases with the increase in weld width.When other conditions remain unchanged,the height fluctuation of pulsed GMAW pool surface and the change in arc voltage during peak current period decrease with the increase in penetration.With the increase in wire feed speed,the finger-like penetration could enhance the electromagnetic force to accelerate the molten metal flow,leading to a reduced relative velocity between the droplet and the molten metal which lessens the effect of droplet transfer on the growing molten pool and further induces a smaller amplitude oscillation.When the droplet is very close to the molten pool,the arc pressure should not be loaded on the central area of pool surface.With such a loading method,the simulated dynamic behavior of molten pool surface could comply well with experimental results.