Influence of shielding gas on cathode spot behaviours in alternating current tungsten inert gas welding of aluminium

摘要

The influence of shielding gas (argon, helium) on the cathode spot (CS) behaviours in aluminium AC TIG welding was investigated by the high-speed (500,000 fps) observation. Moreover, the temperature of the weld pool surface was measured by the two-wavelength pyrometer method to discuss its relationship with the CS. Consequently, the average current per CS in the helium case was 16.7 A, higher than 7.6 A in the argon case. The larger current per spot is considered to cause the higher velocity of the CS on liquid surface in the helium case (168 +/- 41 m s(-1)) than that in the argon case. The average number of the CS was almost zero within around a radius of 2.0 mm in helium, which had the temperature above 1300 K.