Study on removal mechanism of oxide film in direct current straight polarity tungsten arc welding of aluminum alloy

Abstract

The Direct Current Straight Polarity (DCSP) TIG welding process of 2219 aluminum alloy was realized by removing oxide film on aluminum alloy surface with the activating flux. The effect of activating flux removing 2219 aluminum alloy surface anode oxide film and welding slag distribution morphology under the action of welding arc were analyzed. The results showed that the activating flux can effectively remove the anode oxide film, and welding slag with discontinuous floccules was distributed on the basic surface of aluminum, which was easy to remove. The difference in thermal expansion coefficient between Al and Al₂O₃ oxide films caused Al₂O₃ oxide films to crack under the action of high-temperature electric arc in TIG welding, but the oxide films cannot be removed. However, the weld surface coated with fluoride activating flux, fluoride can permeate between the oxide film and the aluminum matrix from the place where the oxide film cracked, causing defects at the film/matrix interface, which was conducive to peeling off the oxide film on the weld surface.

Keywords:

• Direct current straight polarity
• TIG welding
• oxide film
• activating flux

Disclosure statement

No potential conflict of interest was reported by the author(s).