Research On Plasma Transport Coefficient Of Underwater Wet Welding And Simulation Analysis Of Arc

Underwater welding technology has been widely used in the field of underwater construction and military,among which underwater wet flux cored wire arc welding（underwater wet FCAW）has a good application and development prospect.However,the underwater wet FCAW welding process contains complex physical and chemical changes,resulting in poor welding stability,poor welding quality,affecting its application in important components.Therefore,it is very important to study underwater wet FCAW and improve the stability of underwater wet welding.For underwater wet FCAW research mostly from the macroscopic Angle of flux-cored wire and welding current voltage research,from the Angle of the micro arc plasma research is less,the underwater wet FCAW arc plasma research are much rarer,physical parameters of the existing research of arc plasma transport coefficient are mostly air arc.Therefore,from the perspective of microscopic physics and chemistry,this dissertation deeply studied the component properties of underwater wet welding FCAW arc plasma,studied its component particle number density and transport coefficient and other physical parameters,used the obtained physical parameters to conduct underwater wet FCAW simulation research,and studied the underwater wet FCAW from the essence of the arc.The welding arc properties of underwater wet FCAW were investigated.In this dissertation,the underwater wet welding experiment platform was used to conduct welding experiments,real-time acquisition of welding arc spectral information,arc spectral diagnosis and analysis of the collected spectral information,determination of underwater wet welding arc plasma components;The partition function of each component particle was calculated,and the numerical density of each particle was calculated.The numerical density of each component particle in the arc plasma was compared and analyzed in 20m,50m and 100m water depth environments.The calculation of the particle number density also laid a foundation for the subsequent calculation of transport parameters.Based on the local thermodynamic equilibrium state,the expressions of electric conductivity,thermal conductivity and viscosity coefficient of arc plasma in underwater wet welding were derived by simplifying distribution function and particle collision term appropriately.The electric conductivity,thermal conductivity and viscosity coefficient of underwater wet welding arc of 20m,50m and 100m are calculated by using the expression of arc transport coefficient,and the influence of water depth and temperature on the transport coefficient is compared and analyzed.The arc magnetohydrodynamics model was established,and the underwater wet welding arc simulation was completed in COMSOL Multiphysics,and the distribution of arc temperature field,pressure field,flow field and magnetic field was analyzed.The research shows that:（1）In the particle number density of the arc plasma components of underwater wet welding,the number density of H₂,CO and other molecules decreases gradually with the increase of arc temperature,while the number density of C,H,O and other atoms increases first with the increase of arc temperature,and then decreases gradually,while the number density of electrons increases continuously and finally tends to equilibrium.For the same particle,when the arc temperature is the same,the deeper the water is,the greater the particle number density is.（2）The overall trend of thermal conductivity of arc plasma varies with temperature at different water depths,but the peak point of thermal conductivity appears at different temperature times.The peak point of thermal conductivity of arc plasma in deeper water depths moves a little later.The viscosity coefficients of the three different water depths have the same variation trend,but the viscosity coefficients of 100m water depths are always larger than those of 20m and 50m water depths.The conductivity of arc plasma in welding environment decreases with deeper water depth.（3）The arc temperature field distribution of underwater wet welding arc simulation is roughly in the shape of a bell jar,which is consistent with the comparison and analysis of existing literature.The distribution of the velocity field is similar to that of the temperature field.The plasma velocity is the highest near the welding wire.Arc pressure is mainly concentrated near the workpiece;The magnetic field is symmetrically distributed and mainly concentrated around the flux cored wire.