| A large wide aluminum alloy radiator is the important component of the railway vehicles such as high-speed train and city rail,etc.Existing import products use aluminum alloy plate bonding process which feature high cost and low radiation efficiency.Moreover,the technology is subject to others.Domestic,for the realization of the introduction,absorption,and innovation,extrusion and welding process is developed,welding is a major problem of the process.Due to the low joint strength,many welding pores,large welding deformation and low welding efficiency,the existing aluminum alloy fusion welding method exist a lot of problems.In order to further improve the welding quality and productivity,this thesis selects friction stir welding technology route to butt weld narrow extrusion profiles.Due to the special efficient heat dissipation structure of the radiator,the inherent big temperature gradient of thick plate welding and upper pressure requiring the support stability of the fin type radiating structure,it’s necessary to put forward a reasonable welding process and tooling method.In this paper,according to the friction stir welding heat production process and fluid dynamics theory,the friction stir welding temperature field and flow field model of the20mm6063-T5radiator aluminum alloy were constructed.Through the analysis of the simulation welding temperature field distribution and the thermoplastic metal flow condition we fould out the optimal conditions and welding process parameters.On the basis of numerical simulation we conducted the friction stir welding butt joint test of the heat sink.Radiator aluminum alloy6063-T5belongs to the Al-Mg-Si series forging category aluminum alloy which can be strengthened by heat treatment.Its surface is easy to generate the dense and stable oxidation film which have the strong surface protection ability Through the microcosmic metallographic analysis,scanning electron microscopy energy spectrum test and X-ray examination,the oxidation film is easily stirred into joint and influence the local stress distribution of material leading to the weak link defects that will make the strength and fatigue resistance poor of the radiator and reduce the product usability. According to the easily oxidized characteristic of6063aluminum alloy,In addition to strict chemical cleaning and mechanical polishing in joint related areas before the welding,we put forward a full range of inert gas protection scheme and designed gas protection friction stir welding fixture.In the welding process feeding inert gas Ar to create a closed space isolated from the air for preventing the oxidation of the alloy and the S curve weak link defect can be avoided from the source.Analysing the surface morphology,microstructure and mechanical properties of the weld, the results show that when the rotating speed is1200r/min and the welding speed is80mm/min,the butt joints with good superficial shaping quality,almost no deformation and no internal defects can be obtained and the weld’s average tensile strength reaches148.83Mpa,reaching87.3%of the base metal,which average elongation after fracture is17.9%,also reaching62%of the base metal.On the basis of the early exploration,The corresponding welding technology was formulated,radiator products were successful welded.After welding,through the X-ray detection,ultrasonic detection and metallographic microscope observation,the predictable internal defects such as the loose organization,groove holes and the S curve weak links were tested.In the light of defects we put forward effective method to eliminate them.As the actual product size requirements,long radiator plate butt welding and even more plate welding were undertook on the basis of the early exploration,we obtained the high quality welding joints. |
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