Numerical Simulation Of Plasma-MIG Hybrid Welding On Medium Thickness Plate Corner Joint Based On Fluent

With the rapid development of aerospace,rail transit,shipbuilding industry,the demand for high-quality and high-efficiency welding methods is more urgent.One of the effective ways to realize this desire is to combine different kinds of arc or heat source to form the composite heat source welding.Plasma-MIG is a kind of hybrid heat source welding technology combining plasma arc welding and inert gas arc welding.Due to the unique structure of the welding torch,a series of characteristics of the process are produced,such as deep penetration,stable welding process and no splash.Especially in the special conditions of welding bogie,pressure vessel or chamber,the plasma-MIG welding method can reach the effect of penetration which can not be achieved by conventional welding methods.In the welding of the fillet weld,the usual method is to increase the angle of the groove or adopt the method of double side groove welding to meet the quality requirements.When the plate is too large,the problem is the heat input is too large and lead to serious deformation of the workpiece,the mechanical properties of the welded joints decreased.The original plasma-MIG welding does not penetrate through welding when the welding groove is narrow.Considering the accessibility of the welding torch,it is necessary to study the internal mechanism of the welding process.However,the temperature of the welding arc is very high,it is difficult to study the arc through the ordinary detection and observation methods;The fluid flow and heat transfer in the weld pool is a dynamic time varying process.It is very difficult to detect the phenomena in the molten pool.In recent years,with the rapid development of numerical simulation method,it is helpful to understand the physical essence of the welding process from a deeper level.The author uses the FLUENT simulation software,combined with the fluid dynamics equations,the theory of MIGnetic fluid dynamics and Maxwell equations,established a three-dimensional mathematical model of plasma-MIG composite welding on low carbon steel T joint,the welding process of the welding arc,weld pool temperature field and flow field are simulated.First of all,the three-dimensional modeling was established,using Solidworks software and imported to the Hypermesh software for meshing.According to the three conservation equations(mass conservation,momentum conservation,energy conservation)and Maxwell’s equations,the mathematical model of 3D plasma-MIG composite arc is established.The temperature field and flow field can be obtained by calculation.With changing the plasma current,MIG current,the flow rate of the protective gas and plasma gas,the change of the composite arc shape was observed;In order to verify the accuracy of the simulation results,the high speed camera system was used to record the shape of the arc during the welding process.Secondly,the coupling 3D mathematical model of the plasma-MIG composite arc and melting pool is established.The melting process of the base metal and the shape of the final pool section can be obtained by calculation;The welding experiments were carried out under the same welding process,and the accuracy of the simulation results was verified by the comparison between the experimental and the simulation results.In this paper,the physical essence of welding is understood more deeply with simulating the arc and molten pool of plasma-MIG hybrid welding under special conditions.