Researchon Welding Deformation Of Steel Aluminum And Sheet Steel Based On CMT Spot Welding

As an important means of energy-saving and emission reduction,the lightweight of vehicle body has become the important trends of automobile industry.Since the car body is made of a large number of components,it is necessary to choose the proper materials in accordance with the specific parts,which is the core concept of lightweight.Steel welding with aluminum alloy not only reduce the weight of car,but also more economic,thus improve the safety.However,steel and aluminum alloy has great difference in material properties,which causes the welding of aluminum steel produces a large deformation and makes the assembly size quality difficult to control.Therefore,studying the deformation law and control method in the welding process of steel and aluminum sheets has a practical significance.In this thesis,studying the Al/steel sheet welding deformation systematically based on Cold Metal Transfer(CMT)spot welding.In the beginning,through CMT spot welding of Al/steel sheet in physics experiment,determining the reasonable range of welding process parameters,and analyzes the influence on the welded joint appearance,the organization and the joint mechanical properties in different wire feeding speed.Then the finite element analysis model is established according to the characteristics of CMT spot welding,and the welding deformation is analyzed theoretically.Finally through physical experiment and simulation to establishes response surface analysis model,analyzing the various factors’ influences in welding deformation,which is concluded that the reasonable welding craft parameters and effective control of welding deformation.The main research contents are as follows:(1)To investigate the influence of welding process parameters on the of Al/steel CMT spot welding.The reasonable range of welding parameters was determined through multi-group welding test.The welding quality was evaluated by tensile test and metallographic analysis.Screening the main welding technological parameters by analysis of various process parameters on the bonding strength and the microstructure.Using scanning electron microscopy(SEM)analysis of the characteristics of aluminum/steel CMT spot welding joint organization.To establish the finite element simulation model of aluminum/steel sheets welding.(2)To establish the finite element simulation model of aluminum/steel sheets.According to the welding characteristics of CMT and the actual welding process,the proper heat source model is selected to determine the accurate heat source parameters through the heat source check.Load heat source model after the whole process of welding temperature field is calculated.Then the transient temperature field of thermal analysis for stress analysis of load.finally getting the residual stress distribution and deformation analysis model.Compared with the actual welding deformation,the correctness of the simulation is verified.(3)To establish the effective prediction model of the deformation of Al/steel sheets CMT spot welding.Firstly,the main factors that influence deformation are selected by orthogonal test,and then the mathematical relation model of CMT welding process parameters and the deformation of CMT spot welding is established through the response surface analysis method.More clearly analysis of the relationship between welding process parameters and the welding deformation.The range of reasonable guidance of Al/steel CMT spot welding is given by the response surface model parameters and improving the efficiency of welding.The main research of this thesis is the deformation of single point of Al/steel CMT welding.The article research results can be extended to CMT welding multi-point deformation analysis and assembling deviation analysis,at the same time can also be applied to magnesium,aluminum,magnesium,steel,titanium steel dissimilar materials,such as deformation analysis.That has a strong engineering application prospects.