Numerical Simulation Of The Metal Transfer Process Of Underwater Wet Flux Cored Arc Welding

Underwater welding technology is an important means of offshore engineering construction,mainly including wet method,dry method and partial dry method.Wet welding is widely used in marine engineering structures due to its simple equipment,convenient operation and low cost.In the underwater wet welding process,the welding torch and the workpiece are directly placed in the water,and the arc combustion and the droplet transfer are carried out in the bubbles generated by the water evaporation and the flux-cored wire gas generation.Due to a series of reasons such as cooling of water environment,bubble floating,arc drift,etc.,the underwater wet welding process has problems such as large welding spatter,poor weld formation,and easy arc breaking.As an important way to transfer mass transfer heat transfer,the stability of the droplet transfer will largely affect the quality of the weld.By establishing a reasonable mathematical analysis model,the numerical simulation of the underwater wet welding droplet transfer process,quantitative analysis of the physical quantities affecting the droplet transfer and the dynamic evolution of the droplets have important theoretical and practical value.Based on the basic theories of fluid mechanics and electromagnetism,this paper establishes a three-dimensional numerical analysis model of the underwater flux-cored wire wet welding droplet transfer process,considering the effects of gravity,surface tension,electromagnetic force and bubble floating on the droplet transfer.And appropriate simplification and hypothesis processing for the complex environment in the underwater welding process.In the fluid mechanics analysis software ANSYS FLUENT,through the secondary development of the software,the droplet transfer force is heated and set reasonably.The differential equations are discretized by the finite volume method,and the two-phase interface is tracked by the VOF method and solved by the PISO algorithm.Quantitative analysis of the underwater flux-cored wire wet-welded droplets continued to grow under the influence of various driving forces,and finally separated from the physical process of the welding wire falling into the molten pool.The numerical simulation results show that during the underwater wet welding process,the welding arc is always at the bottom of the droplet,and the droplets cannot be wrapped,and the arc shape is more restrained.The end of the wire is melted by the heating of the arc and tends to be hemispherical under the action of surface tension,and the axial electromagnetic force received by the droplet is a force that hinders the transition of the droplet due to the concentrated distribution of the arc energy.At the same time,during the welding process,the water under the arc is rapidly decomposed by heating,and the molten pool is also heated to release the gas.Due to the presence of water pressure,the generated gas cannot be freely diffused to the periphery,but moves upward in the form of bubbles.The high-speed flowing airflow acts on the continuously growing droplets to form a resistance.In the laminar flow state,that is,when the Reynolds number is small,the fluid with a faster flow velocity will drag the fluid with a slower flow velocity,hindering the droplet transfer,making the droplet drop difficult,and finally forming a large drop transition.Finally,the high-speed camera and electric signal sensor are used to collect the visual signal and electrical signal during the droplet transfer process,which verifies the reliability of the model.