| With the development of lightweight automobile body,it is difficult to achieve the ideal weld quality by using the traditional welding methods in the application of aluminum alloy parts in automobile body manufacturing.CMT(Cold Metal Transfer),as a low-heat input welding technology,has the advantages of more stable arc and less heat input during welding,no spatter in arc initiation,and accurate arc length control.It has been applied more and more widely in various industries.At present,although there are many researches on the welding of aluminum alloy,most reaserch of them were about traditional arc welding.The deformation of the workpiece after welding is a complex process.The parameters in the welding,the presence or absence of oxidation film,the base material of the welding,etc.,all have an impact on the welding.Considering control the welding deformation of the complex working conditions in the welding process is still needed a more detailed study.In this paper AA6061-T6 aluminum alloy sheet as the research materials to study the welding of aluminum alloy sheet with different parameters combinations.Firstly,through the CMT experiments,the mechanism of the joint defect of anodic oxidized aluminum alloy sheet is studied,to evaluate the influence of the oxide film on the surface of aluminum alloy sheet on the welding.Then,the surface of aluminum alloy under natural oxide was treated by ultrasonic cleaning process,and the effect of ultrasonic cleaning on oxidation and weld optimization was analyzed to obtain better quality.Finally,the best ultrasonic cleaning parameters and welding parameters are obtained by using deformation multiple parameters to control welding quality and deformation,on the premise of ensuring weld quality.The main contents are as follows:(1)The mechanism of weld defects in CMT lap welding of anodized aluminum alloy thin plate is presented.The behavior of oxide film on aluminum alloy surface during welding was studied.The influence of surface oxidation film on welding heat input was explored,and the mechanism of welding defect formation was explained from the transient evolution of weld pool during welding.The relationship between the anodic oxidation film on aluminum alloy surface and welding quality and joint mechanical properties was obtained,the mechanism of defect is given.(2)Based on the method of anodized aluminum alloy welding,the welding and deformation law of aluminum alloy in natural oxide are given.Due to serious welding defects in the welding process of anodized aluminum alloy,in order to explore the relationship between the welding defects and the thickness of the oxide film,this section welded the aluminum alloy plate with the oxide film and the thickness of the natural oxide.It found that the welding quality of the aluminum alloy plate was related to the thickness of the oxide film.It is also found that reducing the thickness of oxide film can improve the welding quality.The variation of welding space is also analyzed.(3)The surface treatment method of aluminum alloy plate with ultrasonic cleaning is provided by comparing the anodic oxidation and natural oxidation grade.In order to verify the effectiveness of ultrasonic cleaning method,experiments were carried out on the oxidized plate in natural state with small degree of oxidation.Water ultrasonic cleaning and acetic acid ultrasonic cleaning,were compared respectively.The effect of ultrasonic cleaning surface treatment on the quality of aluminum alloy welding was studied by analyzing the data of weld depth and porosity after welding.(4)Based on various parameters of CMT welding parameters and plate processing methods of aluminum alloy sheet,a method of controlling welding deformation is presented.Since the welding sample involves two processes of welding and ultrasonic,the optimal parameters such as welding parameters,surface oxidation degree,ultrasonic cleaning time and cleaning solution obtained by combining the fixture arrangement of the plate and the plate condition.It can control the welding deformation and improve the welding quality on the premise of ensuring the welding quality.The welding and ultrasonic cleaning technology studied in this paper can effectively improve the weld quality.In addition,this paper explains the anodic oxidation film in the welding process and proposes a evolution of the weld pool.The welding process studied can effectively control the quality of the welded joint of aluminum alloy sheet metal and optimize the connection of sheet metal. |
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