Study On Friction Stir Welding Technology Of 7B52 Laminated Aluminum Alloy Corner Joint

In this paper,in response to the urgent need for high-quality,high-efficiency,smalldeformation welding manufacturing of 7B52 laminated aluminum alloy special car body box structure,the optimized design of 7B52 laminated aluminum alloy corner joint structure and specific friction stir welding process,welding process temperature field and stirring head force simulation and simulation,static joint shoulder friction stir welding process test,microstructure and mechanical property testing and analysis of welded joints,qualified welding samples were formed,the best process specification parameters were obtained,and accumulated richer design,simulation and test data.Through the force analysis of the actual working conditions of the corner joints of the special car body,the technical solutions such as the static shaft shoulder friction stir welding process on the inside and the dynamic shaft shoulder friction stir welding process on the outside of the box structure corner joint are proposed.Based on the analysis of the welding conditions of the welding head and the technical indicators,the optimal size parameters of the mixing pin and the static shoulder are given by the analysis of the welding conditions of the welding head of the inner corner joint weld joint.Simulation analysis,optimized design of the static shaft shoulder mixing head structure in the weld joint of the corner joint.The temperature field of the friction stir welding process,the stress field of the stirring pin and the static shoulder were simulated using ANSYS finite element simulation software.The maximum temperature of the weld seam was 498 ? and the optimal speed range of the stirring pin was 800-1300 rpm.Analysis data.Passed more than 30 sets of 15 mm thick 7B52 corner joint welding process test.The best process of the static shaft shoulder stir welding of the corner joint weld(inner weld)is: welding speed 30?40mm/min,rotation speed 1000?1100rpm;The best process for the dynamic shaft shoulder stir welding of the butt welds(outer welds)of the corner joints is: welding speed 200?350mm/min,rotation speed 650?850rpm;the process test shows that the static and dynamic shaft shoulder friction stir welding process is stable,The mixing pin works reliably,the surface of the weld is smooth and the appearance is beautiful,the weld joint has no welding defects such as cracks,unwelded,slag inclusions,delamination,etc.The temperature test during the welding process also shows that the accuracy of the simulation calculation of the corner joint is high.By comparing the temperature curve of the measuring point with the temperature curve in the simulation results,the fitting degree is more than 0.8,and the designed stirring pin meets the needs of 7B52 laminated aluminum alloy welding.Combining simulation and test data,the temperature distribution of the weld is discussed Relationship with weld defects.Through the inspection and analysis of optical microstructure,SEX,EDS and hardness,combined with the calculation results of simulation,the laws of metal flow in the weld nugget area,element distribution of the weld joint and joint hardness distribution are proposed.FSW has a 7B52 laminated aluminum alloy with the stirring effect,the interlayer materials mixed into the weld nugget zone,making the element distribution in the weld nugget zone uneven,and the horizontal and vertical hardness values fluctuated greatly.The effect of repeated heat input on the joint microhardness was analyzed.The shear and bending tests show that the maximum shear strength and bending strength of the butt weld joint of the angular joint butt weld are 285 MPa and 447 MPa,respectively.The bending strength is 266 MPa and 386.7MPa respectively,and the fractures are all ductile fractures;the shear strength coefficient of the weld joint of the corner joint reaches 71.3%.