| As countries around the world begin to strengthen the strict measures for environmental protection,the concept of "green" and "harmonious" has become the main theme of life in the world.The increasing material and cultural exchange has brought the automobile industry into an unprecedented prosperity,and the traditional automobile is mainly driven by burning of diesel oil,gasoline and other energy sources seriously polluted to the environment,which obviously can't meet the trend of development in the world today.As a clean new energy source,electric power is widely concerned,and new energy power battery cars are favored by all countries.However,power battery as the main core component becomes the main obstacle to restrain its development.To ensure the quality of power battery connection and improve the service life is very important to the development of new energy power battery vehicles.Based on the laser welding technology,the reliable connection technology between pole ear piece and bus bar of power battery is studied.The basic characteristics of aluminum alloy welding for pole ear piece and the basic principle of laser welding technology are introduced.Combined with a large number of previous experimental results,the quasi-continuous pulsed fiber laser equipment and single-mode continuous wave fiber laser equipment were selected to carry out systematic experimental research on incomplete penetration laminated welding of pole ear slices.The main research contents are as follows:(1)Adopt quasi-continuous pulse optical fiber laser welding equipment to weld 0.5mm thick aluminum alloy sheet to obtain the well-welded tissue joint.The effects of different laser peak power,welding speed,swing spacing,pulse width and defocusing amount on weld performance were studied.It was found that when the laser peak power was 1050 W,welding speed was 5 mm/s,pulse width was 7.5 ms,defocusing was-1mm and swing spacing was 1.15 mm,weld tissue joints could be obtained to meet the requirements of power battery.However,the phenomenon of sudden cooling and sudden heat in pulsed laser,it is easy to produce defects such as pores and cracks,which is more sensitive to the change of process parameters.(2)The welding test of 0.5 mm thick aluminum alloy sheet was carried out by using single mode continuous wave laser welding equipment,considering the influence of laser output power,welding scanning speed,swing spacing and defocus on weld performance.In addition,the effect of the bonding spacing of aluminum thin sheet on weld seam was studied in combination with the actual working conditions.The results show that the welding at laser focal point is the most reliable when the laser power is1000 W,the welding speed is 1000 mm/s,the swing distance is 0.3 mm,the swing amplitude is 0.5 mm,and the effect of the bonding distance of aluminum sheet on weld performance is greater than that of laser process parameters on weld performance.Because the beam energy is concentrated and the penetration ability is strong,the weld pool is more consistent and has no obvious defects.(3)Comparing the weld performance of quasi-continuous pulsed fiber laser with single-mode continuous wave laser,the welding effect of aluminum sheet by single-mode continuous wave laser is obviously better than that of quasi-continuous pulsed laser equipment.At the same conditions,the tensile strength of the weld is 500 N higher than that of the quasi-continuous pulsed laser,and there are no obvious porosity,cracks and other defects in the weld.Therefore,in the non-permeable laser overlay welding process of 0.5 mm thick aluminum alloy sheet,the single mode continuous wave fiber laser can be selected first,and the workpiece to be welded should be kept flat and surface free of dirt before welding,and the bonding spacing should be less than 0.2 mm to ensure the consistency and stability of the weld. |
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