Investigation On Dissimilar Alloy Laser Welding Of T2 Copper/SUS 304

As the global industrial development,the needs and requirements of the engineering structures are becoming higher and higher,but the same alloy welded components already cannot satisfy the needs of industrial production,which leads that dissimilar alloy welded components is becoming a new trend in the development of welding.Copper-steel dissimilar alloy composites can not only combine the advantage of the two materials,but also can save precious metals to reduce costs.The dissimilar alloy welding is more complex and difficult,especially compared with the same material welding.So there are many defects in copper-steel dissimilar alloy welding such as gas holes and cracks,because of the big difference between copper and steel of chemical composition and thermal physical properties.Therefore,it is the key to popularize copper steel dissimilar alloy welded joint with good shape and good performance.In this paper,the whole factors of laser welding of copper-steel dissimilar alloy were investigated,and the welding process window has been established.Detailed study of the laser angle,light spot position,laser power,welding speed,defocus amount and linear energy influence on copper-steel dissimilar alloy weld,found that only in that situation of the laser Angle was-10 °,the position of light spot was 0,the laser power is greater than 2800 W,the defocus amount between-4 mm ~ + 6 mm and guarantee linear energy between 75 KJ/m ~ 100 KJ/m good forming welding joint can be attained.And in the process of welding molten the dynamic behavior of pool and the keyhole is studied,showed that the weld molten pool and the keyhole were cyclical swings in the welding process,welding molten pool will shift to the steel side,keyhole will be shift to the copper side.Next the copper penetrating crack in the weld joint of steel side heat affected zone was analyzed,found that copper penetration cracks in steel side heat affected zone existed in the form of the intergranular permeability,namely in the process of welding thermal cycle under the action of thermal stress in welding Cu element along the austenite grain boundary penetration in the direction of steel side parent metal.The formation of copper permeation cracks in the steel side heat affected zone has experienced the four stages of grain boundary liquefaction,initial crack growth,crack growth and intergranular cracking.And linear energy and defocus amount influenced the formation of penetration cracks,along with the rising of the line energy and defocus amount,the longest crack length,crack,liquefied grain boundary of the maximum liquid film thickness and length of copper penetrating crack of steel side heat affected zone were on the rise,when the linear energy was between 75 KJ/m ~ 100 KJ/m,defocus amount was zero could get the crack length and the width of the smallest in copper-steel dissimilar alloy welded joint.Finally,the microstructure and mechanical properties of copper-steel dissimilar alloy weld joint were tested and found no intermetallic compounds existed in the copper-steel dissimilar alloy weld joint internal,but Cu and gamma austenite.Under the action of molten pool flow,the Fe elements were disjointed distributed in the weld,forming diffuse distribution or mass distribution.Weld joint mechanical performance was excellent,the average hardness could reach 127.91 HV,higher than the base copper hardness and was below the matrix hardness of stainless steel,the tensile strength of joint at room temperature was 260.024 MPa,the tensile strength of joint at high temperature was 90.573 MPa,and the fracture position of the joints appears in the heat affected zone of copper side,and the mechanical properties of the weld are close to the copper plate.Therefore,in this process,we can obtain the excellent properties of copper-steel dissimilar alloy composite components.