Numerical Analysis Of Dynamic Heat Transfer And Fluid Flow In PAW With Hot Wire Weld Pool And Keyhole

K-PAW(Keyhole Plasma Arc Welding) with hot wire is a new welding method basedon Keyhole Plasma Arc Welding. It can improve deposition efficiency, reduce the fusionration and superheat of molten pool, being easier to control welding shaping, so it will has abright prospect in future. The dynamic evolution of keyhole plays an important role indetermining weld penetration and weld quality. Analysis the stability of the keyhole withdroplet will lay solid foundation for optimizing the welding parameters.A three dimensional transient model of fluid flow and heat transfer in weld pool、keyhole and droplet is established based on the in-depth analysis of the welding shaping ofK-PAW. A combined volumetric heat source which include double-ellipsoid source andconic body source model is established, the height of conic body source is adjustedaccording to the depth of keyhole. The volume of fluids method (VOF) is used to track thekeyhole boundary, and double elliptical distribution of plasma arc pressure is applied on thekeyhole boundary, electromagnetic force, surface tension,buoyancy force, gravity,radiation and convection are included in the weld pool. The latent heat and momentum sinkdue to the solidification and melting are dealt with by enthalpy porosity technique. ThePISO (Pressure-Implicit with Splitting of Operators) algorithm is used to deal with thecoupled behaviors of pressure and velocity. The droplet with some energy and velocity isadded on the top of the weld pool with further development of FLUENT software. Thetemperature of welding wire with some current and feed rate is calculated based on thelaw of conservation of energy, and then the energy which the arc loses can be calculatedwhen weld wire is heated to overheated droplet.Based on established model, the stability of the keyhole and weld pool are analyzed bychanging the welding current and wire feed rate. It can penetrate the plate when the weldcurrent add to140A from135A with the height of keyhole increasing by22.45%, themaximal velocity and pressure on the keyhole increasing by4.83%and4.18%, the timewhich takes to penetrate the plate reducing by8.29%. The fluid metal on the front wall ofkeyhole has maximal velocity, and the fluid metal which are extruded from keyhole areaccumulated in the back of the weld pool by the back wall of keyhole. So the maximalvelocity and pressure of fluid metal distributed in keyhole are regular. The stability of thekeyhole is lowered and it takes more time to penetrate the plate adding droplet in the weldpool. Adding droplet in the front wall of the weld pool will lower the velocity of fluid metal on the front wall of keyhole which is the main driving force to acquire keyhole, and addingdroplet in the back of the weld pool will lower the upward velocity of the fluid metal whichare extruded from the keyhole, so the stability of the keyhole is more weakened. Themaximal velocity and pressure on the wall of the keyhole with hot wire is more than theone without hot wire, the time which takes to penetrate the plate increases by7.82%and16.35%with wire feed rate of0.5m/min and1.0m/min respectively.The calculated keyhole shape at backside and the transverse cross-section of weldjoint are compared with the experimental measurements. Both agree well with each other.