Copper/stainless Steel Lap Joint By Friction Stir Welding Process Research And Application

:Copper and stainless steel are two types of widely used metal materials. In order to meet the needs of different structures, the composite structures of the two types of materials are often required in the production and the electrolytic manganese cathode plate is one of its typical application. Due to the big difference of the physical and welding performance between the two materials, so the welding between the dissimilar materials of copper and stainless steel is difficulty. This paper mainly research on the copper/stainless steel lap joint by friction stir welding process, and ultimately this technology was used on the electrolytic manganese cathode plate welded.Firstly, the temperature change during the welding process, cooling deformation after welding and material flow around the tool were simulated. The results show that during the stability of the welding process, the welding temperature is about805℃. The warm-up time before weld, the temperature control at final welding and reducing the contact resistance between the upper and lower material is critical for welding. After welding, weldment bent to the copper side, and the maximum displacement of the Z direction is about12mm. Upside combined surface of the joint, copper yield, and in underside stainless steel, the maximum von mises stress is229Mpa. The flowing of stainless steel underside weakened and increase the rotation speed, reduce the welding speed and improve the welding depth can promote material flow. The simulation model is proved correct by testing the temperature changes during welding and analyzing the micro structure of the joint.On the basis of the simulation, testing on the lap joint of copper and stainless steel by friction stir welding, and the joints performance and organizational characteristics were analyzed. The results showed that shear strength of lap joints improved with tool rotation speed improve and the length of probe increases. The shear fracture zone can be divided into crack initiation zone, steady expansion zone and momentary break zone. The copper and stainless steel has a density combination. Advancing side and the return side of the joint are obvious dendritic copper and stainless steel blend area, and underside stainless steel insert into upside copper substrate. In stir zone, copper downward flow overall under pressure of tool. The distribution of hardness was uneven in the combination surfaces of copper and stainless steel, the point hardness on the copper-based material is lower than steel-based point. There are Fe-Cu-Cr-Ni intermetallic compound, copper base material and the stainless steel base material in copper and stainless steel fusion zone.Finally, the friction stir lap welding was used on the electrolytic manganese cathode plate welded. Resistance test show that the use of friction stir welding of electrolytic manganese cathode plates have a higher conductivity than the traditional process connection by rivets or bolts. Through water cooling, punching stress hole and change the manufacturing processes and flat steel, the distortion during friction stir welding process of copper and stainless steel were effectively controlled.