| Energy saving and environmental protection are the development trends in the future automotive,aerospace and other fields.Lightweighting is one of the important ways to achieve this goal.In the traditional manufacturing field,steel and aluminum are indispensable engineering materials.Replacing steel materials with aluminum can not only reduce the weight and cost of components,but also meet the requirements of energy conservation and environmental protection.Therefore,the use of steel/aluminum structural parts to achieve material lightweighting has become The current research hotspot of industrial technology.Laser-arc hybrid heat source welding technology,as one of the new hybrid welding technologies,combines the advantages of arc welding and laser welding.It is a new and efficient new welding heat source with the synergy effect of 1 + 1 > 2.There is huge potential for steel/aluminum structural connections.However,the physical properties of steel and aluminum are significantly different,the metallurgical compatibility is poor,and brittle intermetallic compounds are easily formed during welding,which also poses a huge challenge to the weldability of steel and aluminum.In this subject,the laser-TIG composite heat source welding method is used to analyze the lap welding process of 430 ferritic stainless steel and 6061 aluminum alloy thin plate.Based on COMSOL simulation software,a three-dimensional transient finite element method for laser-TIG composite lap welding is established.The model elaborates the temperature field distribution characteristics of the joint during the welding process.The evolution of the microstructure,the growth mechanism of the interface layer and the mechanical properties of the joint are discussed.The following results are obtained:The laser-TIG composite heat source welding can realize the effective connection of steel/aluminum dissimilar metals.By studying the influence of the main welding parameters?laser power,arc current,welding speed?on the formability of the weld and the welding pool under the action of a single factor,the welding is found.Speed has the greatest influence on the surface morphology and weld pool size of the weld.The peak laser current has a greater effect on the weld depth,and the arc current has a significant effect on the weld width.Based on the distribution cloud diagram and thermal cycle curve of surface temperature field and longitudinal section temperature field of laser-arc welding,the temperature field distribution characteristics of laser-TIG composite lap welding were systematically analyzed.Comparing the experimental results with the simulation results for the same process parameters,the morphology of the obtained molten pool is basically consistent with the morphology of the molten pool simulated by finite element analysis,which verifies the accuracy of the simulation results.By analyzing the temperature field distribution characteristics under different process parameters and combining the experimental results,the optimal process parameter combination under the experimental conditions was obtained: laser peak current 100 A,arc current 100 A,and welding speed 600 mm·min-1.The steel/aluminum dissimilar metal laser-TIG composite heat source welding head can be divided into six different microstructure regions.The joint has a significant intermetallic compound interface layer.The interface layer has uneven thickness and shape,and the thickness is 10?20 ?m,it is mainly composed of needle-shaped FeAl3 phase and plate-shaped Fe2Al5 phase.The hardness test and tensile test of the joint obtained under the optimal process parameter combination show that the joint interface region has the highest hardness,up to 566 HV,the maximum tensile shear force of the joint is 1.164 k N·cm-1,and the joint fails at the interface steel/aluminum metal.Between compound layers. |
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