Finite Element Analysis Of Welding Process For Automobile Engine Exhaust Manifold

Exhaust manifold is an important part of the exhaust system of automobile engine.It collect the high temperature exhaust gas generated from the combustion process in each cylinder,and then import gas into other parts of exhaust system to be processed.At present,the forming process of exhaust manifold is mainly welding technology.But,the welding process of the exhaust manifold is pretty complicated,and the exhaust manifold may produce certain welding deformation easily during the actual welding process.The welding process of the exhaust manifold is pretty complicated.In order to control the deformation of exhaust manifold,the varying situation of temperature field,stress and strain field should be studied and analyzed firstly.the multi weld welding process of two dissimilar metals between the flange(Q345 steel)and the exhaust branch pipe(316 stainless steel)on certain type of exhaust manifold is simulated with the help of SYSWELD finite analysis software in this paper.The double ellipsoid welding heat source model is chosen to simulate the whole process of welding dynamically.In the numerical simulation with SYSWELD software,the influences resulted by nonlinear relation between the thermo physical properties of materials and temperature,as well as latent heat were in consideration.the coupling calculation of the temperature field and stress-strain field was realized,and the temperature field distribution of the weld area and adjacent weld area under different heat input conditions was obtained.The optimum heat source parameters were obtained by comprehensively comparing the shape of weld pool near welding seam with each group parameter.Subsequently,the samples of the same material and size were selected for experimental welding,and the rationality of the selected heat source model and the grid model was validated by comparing the cross-section shape of the sample weld under different heat source parameters.Based on the results above,two typical welding sequences are established for the process of four welds of the flange and the exhaust branch pipe on this type of exhaust manifold.Through the numerical simulation of the two welding procedures with different welding sequence,welding deformations and residual stress of exhaust manifold under two welding procedures are calculated,which can be utilized to analyze the distribution and characteristics of deformations and residual stress.Analyzing and researching the distribution of deformations and residual stress of exhaust manifold can provide basic theory about controling or diminishing welding deformations and residual stress,which is essential to improving product quality of welding component.The study results also provide theory and experiment reference to the actual welding process of this type of product(dissimilar metal welding in varying thick).