Numerical Simulation Of Flow Field And Temperature Field In Aluminum Alloy Laser CMT Composite Welding Pool

With the rapid advancement of industrialization to modernization,the demand for energy saving,weight reducing,and environmental friendly materials has increased sharply.As the preferred material for structural lightweight,aluminum alloy has excellent mechanical properties,high specific strength,low density,non-toxic,good thermal conductivity,corrosion resistance,and good recycling performance.Compared to other lightweight alloy materials such as titanium and magnesium alloys,aluminum alloy is relatively inexpensive,so it is widely used in the fields of aviation,high-speed rail,subway,and automobile.However,due to the difficult weldability of aluminum alloys,the application of aluminum alloys in various fields is largely restricted.Considering production costs,welding quality,and welding efficiency,it is necessary to conduct in-depth research and seek technical breakthroughs in welding methods,welding processes,and welding equipment.Research has found that laser CMT composite welding,as a new type of composite welding,can achieve efficient and high-quality welding with cold metal transfer(CMT),effectively improving defects such as spatter,porosity,joint softening,poor gap adaptability,insufficient penetration,and incomplete penetration during aluminum alloy welding.Due to the complexity of multi field coupling involved in its welding process,its true welding mechanism is difficult to reveal through traditional theoretical systems.Currently,there are few reports on numerical simulations of laser CMT composite welding at home and abroad.Therefore,this article uses FLUENT to establish a numerical simulation of the temperature field and flow field of the aluminum alloy laser CMT composite welding pool,in order to study its complex welding mechanism.A numerical theoretical analysis of heat transfer,fluid mechanics,and computational fluid forces was conducted for laser CMT composite welding.Numerical simulations of laser welding and laser CMT composite welding weld pools were established,in which the laser heat source was a Gaussian rotating body heat source,and the CMT heat source was a double ellipsoidal sphere heat source coupled with time variables to simulate the "cold heat" alternation.Surface tension,steam recoil The influence of driving forces such as buoyancy,arc pressure,electromagnetic force,and gravity on the temperature field of the molten pool is added as a source term to a user-defined function(UDF)for secondary development of the software.The difference between laser welding and laser CMT composite welding is discussed,and a comparison between laser welding simulation and laser CMT composite welding temperature field simulation is made.The laser power is 5KW,the welding speed is0.01m/s,the CMT heat source voltage is 50 V,and the current is 100 A.The addition of CMT heat source to laser CMT composite welding increases the heat input,which can effectively improve the welding speed.The laser heat source will produce keyholes,which mainly affect the lower part of the weld pool,The CMT heat source mainly affects the upper part of the weld pool,and the effects of laser power and welding speed on the temperature field,flow field,and weld pool morphology in composite welding were studied.Finally,a laser CMT composite welding process was conducted for 6005A-T4 extruded aluminum alloy.By comparing the fusion line morphology,the simulation results showed that the weld cross-section morphology was in good agreement with the experimental weld morphology,demonstrating the accuracy of the numerical simulation model.