Research On Copper And Steel Dissimilar Materials Welding Under Co-Effect Of Laser And Magnetic Field

T2 copper has the characteristics of strong corrosion resistance,beautiful forming,good electrical and thermal conductivity,and has great application prospect;SUS304austenitic stainless steel has good corrosion resistance and tensile strength.The dissimilar weld joints composed of T2 copper and SUS304 austenitic stainless steel have been widely used in aerospace,automotive,electrical and other fields.In this paper,aiming at the problems of unwelded defect and non-uniform components which are easy to occur in the welding process of these two materials,laser welding process experiment of changing laser beam declination and applied alternating magnetic field is carried out.In this study,the laser weld technology at the beam deflection angle of 10°bias steel and unbiased beam are studied.The weld formation,weld joint composition distribution,fusion zone interface morphology and mechanical properties under these two beam incident methods are compared and studied.It is found that the laser beam is offset to the copper plate side at the bottom of the weld,showing a sloping weld cross-section morphology,and the melting amount of copper in the weld increases obviously when the laser beam deviates to the steel side at 10 degrees,and the increase of the melting amount of copper will have a significant influence on the weld joint.When copper melts more,the weld will be filled more,effectively reducing the unfused defects,the transition of the components,elements and micro-hardness in the weld zone will be gentler,and the interface of the copper side joint will be better.The necking occurs at the fracture zone and the elongation increases,the weld strength is higher than the strength of the copper base metal.But the copper melt content of weld samples under unbiased angle laser beam is very pool,the weld composition and micro-hardness change sharply at the interface of the copper side joint,showing a jagged brazing interface in copper side joint.Because of insufficient copper melting,defects such as broken weld,and even unweld are commonto be seen in the weld joint formation,resulting in unstable weld performance.Therefore,joint quality and weld stability can be regulated by adjusting the beam deflection angle.The micro-hardness of various components in the weld are measured,and the mutual mapping relation between component and micro-hardness in copper-steel joint is established.For the problem of non-uniform composition,longitudinal alternating magnetic field is applied and all-factor experiments about magnetic field frequency and excitation current(magnetic induction intensity)are carried out.Besides,joint forming,weld width,weld composition,weld process stability and mechanical properties influenced by different magnetic field parameters are researched.Under certain parameter ranges,the alternating magnetic field can increase the weld width,promote uniformity of weld formation,and ensure a smooth transition of the copper side interface components.It has been found that parameters such as magnetic field frequency of 100-150 Hz and magnetic induction intensity of 18 mT can cause the weld to be widened and widened.It is found that the composition uniformity of the welded joints is greatly improved under the magnetic field frequency of 150 Hz,in which case the copper content in the weld increases,and the strip-like and massive iron-rich phases disappear.For the properties of copper-steel dissimilar welded joints under the action of alternating magnetic field,this study has conducted tensile testing,micro-hardness measurement and electrochemical corrosion testing.After applying alternating magnetic,the tensile strength and elongation of the weld joints have an obviously increase.In the range of magnetic induction intensity of 18 mT and magnetic field frequency of 100Hz-200 Hz,the tensile performance of copper-steel dissimilar joints is improved the most remarkable.The micro-hardness value depends on the composition distribution in the weld zone.Under the action of the alternating magnetic field,with the increase of magnetic induction intensity,the weld composition is more uniform,the hardness standard deviation is significantly reduced,and the standard deviation of weld area is the lowest at 18 mT,and the weld uniformity isthe best under this parameter.The material self-corrosion current density reaches a minimum at 18 mT,the joint has the best corrosion resistance under this parameter.A parameter-forming-component distribution-performance mapping relation is established.In order to analyze the causes of these changes,In order to analyze the causes of these changes,the high-speed imaging of the welding process under magnetic induction intensity of 18 mT and different magnetic field frequencies have been carried out.It is found that the width,the length and the area of the molten pool are obviously increased under the action of alternating magnetic field,but the area of the welding sparkling zone doesn't change so much.Besides,under alternating magnetic field,the flow in the molten pool is intensified and the metal spatter are obviously suppressed,so that the weld width is increased,the uniformity of the weld composition and the joint strength are promoted,proving that the magnetic field frequency of 150 Hz is indeed a very good regulation parameter.