The cleaning action in AC TIG welding is attributed to the oxide film removal process caused by cathode spots. Clarifying the behavior mechanism of these cathode spots will enable the control of the cleaning action. However, the behavior mechanism of cathode spots has not yet been experimentally clarified. This study reports that observations by high-speed video camera revealed the absence of cathode spots at the center of the molten pool, when shot in the vicinity of a molten pool after AC TIG welding using helium as shield gas on aluminum plates.
Droplet temperature for Metal Inert Gas welding process was measured by using optical pyrometry; two colors temperature measurement method. High speed color video camera was used to capture an image of metal droplet during transfer to base metal. As a result, the movement of an arc to cover the droplet from bottom half to the entire droplet by increase of welding current had allowed the change in droplet heating process from concentrated to uniform heating. The concentrated heating in globular transfer mode had caused a higher current density at the bottom of the droplet. The change of heating process from concentrated heating in globular mode to a rather uniform heating during transition resulted in a smaller current density and reduced the heat flux into droplet, therefore decreased the droplet temperature. The further increase in welding current led the increase of droplet temperature and produced the minimum temperature in the middle of transition mode.
The transfer modes in gas metal arc welding have important effects on welding quality. However, present study of metal transfer modes is not yet fully understood. In this study, welding arcs was visualised using the optical emission spectroscopy technique. The carbon steel wire electrode was used for welding with 80% Ar + 20% CO 2 shielding gas. The results showed that the globular to spray transition current was 330-350 A. During globular to spray transition, argon,CO 2 and Fe plasma tended to gradually change from localising near the arc axis to a two-layer structure having 11,000 K in high-temperature region away from the arc axis and around 7000 K in lowtemperature region near the arc axis.
In this study, the heat source characteristics of arc plasma in GMAW using 100% CO2 shielding gas. In particular, arc temperature, Fe vapor concentration and electrical conductivity and metal droplet temperature of a YGW11 wire electrode were measured by optical emission spectroscopic methods. The plasma temperature reached over 8000 K at the center of the arc plasma. The droplet temperature near the arc root was higher than other areas.
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