Experimental Observation of Cleaning Action of Cathode Spots in AC TIG Welding of Aluminum Plates

Abstract

Since it is indispensable to remove oxide layer on aluminum for realizing high quality weld joint in arc welding of aluminum plates, AC TIG welding is generally employed. In periods of EP (Electrode Positive) of AC TIG welding, the oxide layer is removed by cleaning action of cathode spots. In this paper, results on experimental observations of the cleaning action of the oxide layer by cathode spots in AC TIG welding of the aluminum plate with a high speed video camera will be reported. As a result, it was found that cathode spots moved slowly on the oxide layer and their averaged velocity was 26.1m/s. On the other hand, cathode spots near the center of the weld pool, where the oxide layer had been mostly removed, moved at high speed and their averaged velocity reached 121.9 m/s. Furthermore, the velocity greatly changed depending on the position of the cathode spot and exceeded 1 km/s at the maximum.

Behaviors of Cathode Spot in Alternative Current Helium TIG Welding of Aluminum

“…Here, areas of the white zone were selected to see the craters formed by cathode spots. The average velocity on the weld pool surface was the same order of 100 m/s with it in a previous study 16) . Inside the weld pool, the cathode spot moved freely on the liquid surface and the average velocity can reach 200 m/s at the maximum.…”

“…However, the observation with the above frame rates just showed the general tendency of cathode spot movement 14), 15) . Tashiro et al performed the observation of the cathode spot with a frame rate of 500,000 fps 16) . The average velocity of cathode spots reached an order of 100 m/s in the weld pool area and 10 m/s in the oxide layer area.…”

Numerical Analysis on Thermal Characteristics of Direct Current Pulsed Gas Metal Arc Welded Joints of AA5052 Aluminum Alloy to DP590 High Strength Steel

“…In previous studies, joint characteristics of IMC layer in the joint interface and consequent joint strengths are examined in conventional GMA, gas tungsten arc, laser beam, friction stir, and hybrid weldings to join steel to aluminum alloy. [7][8][9][10][11][12] However, many of studies showed defects in the welded joints and wide variations in IMC layer thickness. Furthermore, Su et al [7] indicated that alternating current (AC) pulse GMA provides low level of heat input, but the process induces severe porosities due to its change of polarity, split of bubbles by impact, and turbulence of melting pool by arc pressure.…”

Effect of welding parameters on microstructure and mechanical properties of AA7075/AA5182 alloys joined by TIG and MIG welding methods

“…Therefore, to solve the welding problems between quality and efficiency in the welding of aluminum alloys, some new welding methods such as laser-arc hybrid welding [7][8][9] and friction welding, and friction stirrer welding, which are one of the solid-state welding methods [10][11][12], have been used. Direct-current electrode-positive (GMAW) and alternating current gas tungsten arc welding (GTAW) have been widely used for the aluminum welds, because with these methods, it is easier to clean external factors such as corrosion and oxidation being formed on the surface of the material to obtain good welding called cathodic cleaning [13][14][15][16]. But, the equipment cost of the laser-arc hybrid welding is high, and the FSW and FW are not suitable for some welding positions and some material geometry.…”