Research On The Process Of Multi-layer Laser-MIG Hybrid Welding For Invar Alloy

Invar alloy is widely used in die for the manufacture of aircraft composite materials due to its low coefficient of thermal expansion.The structure of aircraft composite materials is large and complex,which resulting in Invar alloy die processing and manufacturing difficulties.Welding as an indispensable processing technology in the process of Invar alloy die,has a decisive effect on the final performance of die.Laser-MIG hybrid welding has the characteristics of high cladding efficiency and strong adaptability to thick plate welding.These characteristics make it very suitable for the welding of thick plate Invar alloy die.Nowadays,Invar alloy die is mainly dependent on import and study of Invar alloy welding process is still scarce in the domestic,seriously affect the production of Invar alloy die.In this paper,the methods of simulation and experiment are used to study the process of Invar alloy laser-MIG hybrid welding process.Firstly,the finite element model of Invar alloy laser-MIG hybrid welding is established by numerical simulation technology,with this model the relation between parameters including welding current,welding speed,laser power and the geometry of weld pool is explored and obtain the range of welding parameters of Invar alloy laser-MIG hybrid welding preliminary.The temperature field,stress field and deformation field of welding are calculated by these parameters and the thermal cycling curves,stress curves and deformation curves of different welded layers are compared and analyzed.Secondly,the orthogonal experiment is designed to complete the Invar alloy laser-MIG hybrid welding experiment,the rules of process parameters on weld penetration,weld width and joint formation are obtained.By analyzing the welding defects such as gas pores,cracks,incomplete fusion and undercut,the qualitative relationship between welding defects and process parameters is established and the effective control scheme to welding defects is proposed.Finally,the welding process is optimized on the basis of analyzing the macroscopic morphology and welding defects of Invar alloy samples.Laser-MIG hybrid welding experiments are carried out using the optimized process parameters.Through the observation of the joint section,the weld has no obvious crack,porosity and other welding defects.The microstructure,element distribution and mechanical properties of the Invar Joint are tested and analyzed by means of optical microscope,scanning electron microscope,energy spectrum analysis,X-ray diffraction,micro hardness tester.This paper applies the technical route of experiment and simulation analysis to study Invar alloy laser-MIG hybrid welding process in parameters exploration,welding stress and deformation analysis,welding defect analysis and welding process optimization,which provide theoretical and technical guidance to Invar alloy die for civil aircraft composite material components.