| In the micro-plasma arc welding(M-PAW) process of ultra-thin plate, the heat input of the 0.1mm ultra-thin plate is difficult to control. If the heat input is larger than the right heat input, the ultra-thin plate is welded through, and if heat input is smaller, ultra-thin plate can not be melted. Using the experimental method will take a lot of time, labor and money. With the development of science and technology, using computer software for the numerical analysis of the weld pool has been widely popular. So, in this paper, the ANSYS FLUENT software was used for numerical analysis of M-PAW process of ultra-thin plate.According to the welding procedure of M-PAW of ultra-thin plate, combining fluid mechanics and heat transfer theory, the transient numerical analysis models of ultra-thin plate’s weld pool were established. Gaussian distribution model as arc heat source model, which is comprehensive considering the surface tension, the electromagnetic force, buoyancy and arc pressure and other factors, and take those influent factors into concerted, thermal conductivity of ultra-thin plate solid metal, the heat transfer of liquid metal particles inside the pool, and convection, radiation and other conditions of the pool and the external environment, at the same time, utilizing method enthalpy porosity method to handle melting/ freezing problems. To secondary develop of ANSYS FLUENT software, by writing the user-defined function(UDF) will be imported into the program, using the finite volume method to discrete the control equations, and then SIMPLE algorithm to solve the problem, So as to realize numerical analysis of ultra-thin plate M-PAW process.Firstly, a transient model of non-mobile M-PAW of ultra-thin plate is established in this paper, set a small time step for the time of ultra-thin plate heated and form molten pool is very short, to observe heat transfer after ultra-thin plate heated and the formation and growing up of molten pool, to study the forces playing role in process of forming pool, the surface tension, the electromagnetic force, buoyancy and arc pressure were analyzed their effects respectively during the phase of forming pool.Secondly, the pool dynamic process of moving M-PAW of ultra-thin plate was analyzed. By setting a reasonable time, welding temperature field constantly changing with the movement of the arc can be observed during the welding process. The heat affected zone becomes larger and larger with the movement of the arc, while the size of welding central area is basically unchanged that the weld pool in quasi-steady state. And then analyze various forces and their resultant force great impacting on the liquid particles of pool when reaches to quasi-steady state.Finally, M-PAW of ultra-thin plate has been calculated to achieve the temperature field and the flow field of molten pool. Then the pulse parameters were changed, mainly for the duty cycle, the base pulse ratio and pulse frequency, to attain the changes of temperature field and the flow field of molten pool under various pulsed current, and to get the final form of welding seam under the effect of these parameters.A certain amount of M-PAW process testes of the ultra-thin stainless steel plate has been tested. Using an image acquisition system of the welding process obtains the shape and size of the pool. Making the weld cross section photomicrograph after welding get the profile shape and size of welding seam, the experimental values and calculated values were contrastively analyzed. |
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