Study on Removal Mechanism of blowholes in Straight Polarity Direct Current Tungsten Arc Welding of Aluminum Alloy
Hui Lia, Jun-Shan Yaob and Jia-Sheng Zouc
aSchool of Mechanical Engineering/Flight Academy，Chang Zhou Institute of Technology，Chang Zhou，213002，Jiang Su，People’s Republic of China
bThe 10th Research Institute of China Aerospace Science and Industry Corporation，Gui Yang，550000，Gui Zhou，People’s Republic of China
cProvincial Key Lab of Advanced Welding Techno -logy, Jiangsu University of Science and Technology, Zhen jiang 212003, Jiangsu, People’s Republic of China
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Abstract:
2219 aluminum alloy has a series of advantages, such as good mechanical properties, stress corrosion resistance, welding performance, low hot crack tendency, and is widely used in the aerospace field. In the process of evaluating the welding process performance of 2219 aluminum alloy, it was found that the high porosity was proved to be the main weakness of the joint quality of AC TIG welding. The Straight Polarity Direct Current（DCSP）TIG welding process of 2219 aluminum alloy is realized by removing the oxide film on the surface of aluminum alloy with activating flux. The outstanding feature is that the internal porosity of TIG weld is effectively reduced, and the welding quality is improved. Therefore, the mechanism of activating flux to remove the internal porosity of 2219 aluminum alloy DCSP TIG welding was studied. The results show that DCSP TIG welding arc is stable, and the activating flux covers the weld pool surface, which can protect the weld pool and reduce the hydrogen solubility in the weld pool. The infrared thermal imager is used to measure the temperature of the welding joint. The coating of activating flux can increase the heat input of the DCSP TIG welding joint. The increase of the welding heat input reduces the solidification speed of the molten pool, increasesthe existence time of the molten pool, and hydrogen bubbles have enough time to escape from the molten pool. Through the analysis of the force on the surface of the molten pool, it can be seen that the coating of activating flux increases the heat input of the TIG welding joint. The greater the heat input, the stronger the effect of Lorentz force and plasma force on the molten pool, thus changing the movement direction of the metal in the molten pool, which is conducive to the bubble floating, and effectively inhibits the generation of weld porosity.
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