Study On Aluminum Alloy Cold Metal Transition Welding And Additive Manufacturing Process

Cold Metal Transfer(CMT)welding technology is very suitable for the additive manufacturing of aluminum alloy because of its extremely low welding heat input and stable welding arc during the welding process.It has become a research hotspot since its inception.In the case of additive manufacturing research,the formation,size and droplet transfer mode of the droplets have an important influence on the stability during the welding process and the surface forming and quality of the weld.Therefore,it is important to study the droplet transfer.At present,the researches of CMT in various countries mainly focus on the numerical research of process application and temperature field,and the research on CMT droplet transfer theory is still relatively few.Based on VOF theory,fluid dynamics,electromagnetic theory and force analysis of droplets,the mathematical equation of GMAW droplet transfer is established by using FLUENT numerical simulation software.The dynamic behavior of GMAW droplet transfer is simulated when welding current is 150 A,and the temperature field of droplet transfer is analyzed.In order to verify the accuracy of the simulation results,a high-speed camera and electrical signal synchronous acquisition system are built.The results show that the simulation results are in good agreement with the experimental results,which lays a foundation for the realization of CMT droplet transfer.On the basis of GMAW model,the droplet transfer behavior in CMT welding process was dynamically analyzed by FLUENT software.The dynamic changes of droplet transfer during the wire feeding speed of 5m/min and 5.5m/min are mainly analyzed.The simulation results show that when the wire feeding speed is 5m/min,the droplet transfer mode is a typical short-circuit transition.When the wire feeding speed is 5.5m/min,the droplet transfer mode is a mixed transition of the droplet transition and the short-circuit transition.The simulation results are compared with the experimental results and found to be in good agreement,which proves the accuracy of the CMT droplet transfer model.The temperature field and potential field of the droplet transfer under two parameters are analyzed.The results show that the potential field and temperature field are in good agreement with the dynamic process of droplet transfer,which further reveals the mechanism of CMT droplet transfer without splash.Based on the CMT welding droplet transfer process,the CMT additive manufacturing process was studied to explore the macroscopic morphology and microscopicity of single-layer single-channel,single-layer multi-channel,single-channel multi-layer and multi-layer multi-channel specimens under different parameters.The change law of the organization provides reference for the optimization of the parameters of aluminum alloy CMT additive manufacturing.The research results show that when single-layer single-pass welding is carried out,the wire feeding speed is 5m/min,and the welding speed is 60cm/min,the weld is well formed,and the microstructure of the weld is fine equiaxed crystal.Different welding parameters have different effects on the unused parts of single-layer multi-pass surfacing.When performing a single-channel multi-layer experiment,increasing the heat input can improve the wettability and improve the quality of the surfacing weld.