| Laser welding is the use of high energy laser pulses to locally heat the material micro region, Laser radiation energy spread to internal material by heat conduction method, Material is melted to form a molten pool. It is a new type of welding, The main materials for thin-walled, thick materials and precision parts for laser welding, enabling spot welding, butt welding, stitch welding, seal welding, deep penetration, etc. There bath penetration and weld width ratio is high, small weld width, small heat-affected zone, small deformation, welding speed, weld smooth, beautiful, no treatment or simply treated after welding, weld quality, no holes, can be precisely controlled, focused spot small, high positioning accuracy, easy to automate and other advantages.Deep penetration laser welding process holes behavior, observe the flow of the molten pool and the experimental observations, The researchers of domestic and foreign studied the behavior of holes and weld pool coupled with high-speed CCD camera means test, X-ray, audible sound monitoring etc. However, these experiments are not comprehensive and effective means to get inside holes and weld pool flow, pressure and temperature fields data. Therefore, Establish an appropriate mathematical model of integrated to obtain the internal holes and the pool wall energy density, temperature, pressure, speed, distribution and physical appearance in real time by means of the numerical holes simulation, To investigate the nature and physical phenomena related to laser welding has great significance to scienceAround these key issues, In this paper, the behavior of deep penetration laser welding and bath coupling holes were reasonable assumptions and research, For laser spot welding and continuous laser penetration welding process, The numerical model including some effect factors such as surface tension, flotage interaction force between liquid and solid, turbulent, convection and radiation, was founded for laser point welding process, and the evolvements of the depth, By the VOF method for tracking the free surface of the pool, and the pool’s depth, temperature distribution, pressure distribution, the dynamic evolution of the weld morphology was analyzed. The results showed that:the recoil pressure is the important of the driving force when the material is heated, and have a downward force for welding molten pool, lead to the pressure is greater in the bottom of the pool; The recoil pressure discharge the liquid metal along the hole up molten pool, the main heat transfer method in the upper of molten pool is the convection, but that in the lower of molten pool is diffusion; The holes get deep mainly by the recoil pressures, The Boussinesq flotage is the main force of the upper edge over tall; During the welding time t>10ms is format spikes easy, provide the corresponding welding parameters for the laser spot welding. Under the same welding speed and different power bath depth, temperature, flow distribution and dynamic evolution of the holes were analyzed, The results showed that:Welding speed0.08m/s, power1600W、2000W、2400W, respectively welding time t<7.2ms hole depth into linear growth over time in the process of sports molten pool formation. When welding time t>7.2ms, Hole depth value of high frequency oscillation occurs, but the depth of the average tends to be stable. With the moving of the laser beam and molten pool of metal round holes format of circulation, solidified form "scaly solidification line".Through the laser spot welding and continuous laser deep penetration welding process abstract hypothesis, established deep penetration laser welding process numerical holes behavior based on VOF method, using mathematical modeling methods for laser welding process bath dynamics visualization of behavior, in this way the principle of laser welding for research with high scientific value. |
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