Study On Laser-MIG Deep Penetration Lap Welding Of Stainless Steel 304/Aluminum Alloy 5052

The design and application of steel/aluminum dissimilar metal joint can f ully integrate the advantages of steel and aluminum alloy,which is one of the important directions to realize the lightweight of structure.However,due to the differences in physical and chemical properties between steel and aluminum,and in the process of welding,a large number of Fe-Al intermetallic compound layers of brittle phase are easy to appear in the interface layer of steel/aluminum joint,which is unfavorable to the mechanical properties of the joint.For steel/aluminum joints,domestic an d foreign relevant research institutions are studying the improvement of traditional welding process and the application of new process.At present,there are few researches on steel/aluminum deep penetration lap welding,so this paper uses laser-MIG composite welding to carry out deep penetration lap welding on stainless steel 304 with thickness of 3mm and aluminum alloy 5052 with thickness of 1.5mm,which has important theoretical significance and value of theoretical exploration.In this paper,the effects of welding parameters(laser power,arc power and welding speed)and Ni element as the interlayer on the surface morphology,section morphology,microstructure and mechanical properties of stainless steel 304/aluminum alloy 5052laser-MIG deep penetration lap joint were studied.The welding mechanism of laser-MIG deep penetration lap welding of stainless steel 304/aluminum alloy 5052 is also summarized.The results show that the welding parameters have obvio us influence on the weld formation,microstructure and mechanical properties of the joint.With the increase of laser power,the upper weld width is basically the same,the silvery white corrugated metal on the weld surface becomes obvious,the penetration is increasing,cracks appear on the interface layer and the cracks extend with the increase of laser power,the tensile strength of the joint first increases and then decreases.With the increase of arc power,the upper weld width is increasing,the silver white corrugated metal on the weld surface becomes obvious,the width of weld interface layer increases and the penetration remains unchanged.With the increase of welding speed,the amount of weld metal filling decreases,the upper weld width decreases,and the silver white corrugated metal on the weld surface becomes obvious,the thickness of interface layer and effective connection area decrease,at the same time,there is no obvious linear relationship between the mechanical properties of the joint and the welding speed.The microstructure and mechanical properties of stainless steel 304/aluminum alloy 5052 laser-MIG deep penetration lap joint were significantly affected by nickel as the interlayer.The results show that under the condition of low penetration,the addition of nickel interlayer will worsen the steel/aluminum joint and fo rm sandwich structure,which makes the steel/aluminum unable to produce effective connection.Under the condition of medium penetration and high penetration,the addition of nickel interlayer can effectively inhibit the formation of Fe-Al IMCs and reduce the thickness of IMCs in the interface layer.Nickel atoms can replace some of the iron atoms of Fe-Al-IMC to form Al₃Ni,which can reduce the brittleness and hardness of interface layer.Compared with the steel/aluminum joint without nickel interlayer,the tensile strength of the joint with low penetration becomes lower,the tensile strength of the joint with medium penetration increases but the increase range is not obvious,and the tensile s trength of the joint with high penetration increases obviously.Stainless steel 304/aluminum alloy 5052 laser-MIG deep penetration lap welding joint is mainly composed of base metal,reinforcement,arc area,laser area,hardening layer and interface layer,of which the hardening layer and interface layer are the research focus.The tensile test shows that the fracture mode of steel/aluminum joint is brittle fracture.The hardness test shows that the interface layer>hardening layer>the rest(base metal,reinforcement,arc area,laser area).Porosity and interface layer crack are common defects.Weld deformity due to welding thermal deformation is easy to occur and should be avoided as much as possible.