Research On Equipment And Technology Of Friction Plug For Repairing Aluminum Alloy Keyhole Of Rail Vehicle

With the development of the transportation industry and the increasing energy crisis,lightweight technologies have attracted more and more attention.Due to its low density,high specific strength,corrosion resistance,and excellent forming properties,aluminum alloys have been widely used in train bodies with the advantages of greatly reducing the weight of train bodies and reducing costs.Friction stir welding can also solve the difficult problem of aluminum alloy welding.The 6082 aluminum alloy used in the experiment has become more and more popular in the transportation and mechanical engineering industries due to its good weld ability,excellent mechanical processing properties,and strong corrosion resistance.With the continuous advancement of the welding technology,the strength of joints welded with FSW(friction stir welding)is now significantly better than that of conventional MIG welding.In addition,thanks to the low defect rate of welded products,low production costs,and low welding pollution,the current high-speed train manufacturing has gradually formed the mainstream trend of using FSW as a welding method.However,using FSW welding will inevitably lead to "keyhole" phenomenon at the end of the weld.The specific repair method for the "keyhole" mainly depends on the structure of the welding.For example,some FSW welding structures can make the keyhole not remain on the work piece by setting up the welding plate and the lead-out plate while the keyhole portion can also be cut off and the friction welding hole of the friction stir welding can be taken out at the opening of the product part.All of them are feasible solutions.This article takes the 6082 aluminum alloy which is commonly used in high-speed rail vehicles as the research object.It utilizes friction plug welding-related process technology to perform the plug welding process research and equipment manufacturing on the keyhole-like defects left after the traditional friction stir welding of aluminum alloy.By modifying the existing FSW-3LM-015 friction stir welder and the non-keyhole friction stir spot welder independently-developed by our school.designing and processing fixtures,mixing heads,stopper taper,keyhole groove angle,etc.and conducting plug welding experiments under different process parameters.we analyze the plug welding effect to obtain the best process parameters for achieving the purpose of repairing the keyhole defects of traditional friction stir welding with the friction plug repair welding.Experimental results at this stage indicate that:the keyhole defect can be plugged after the same material plug is rotated at a high speed and fed.After the high-speed rotation friction between the plug and the keyhole wall,both the shaping state and the intermolecular coupling are possible.The metallographic observation and electron microscopy observation results of the experimental sample under the current process parameters show that:macroscopically,the keyholes have been plugged while whether the stopper rods and the keyholes have reached the intermolecular binding and what is the lattice arrangement pattern of the boundary line between the stopper rods and the parent material like still need a lot of comparative experiments to be repeatedly observed and discussed for obtaining the best plug welding process parameters that meet the actual production requirements.