Characterizing instability phenomena in arc welding may be a complex task, since they depend on a number of interrelated factors. Such phenomena may manifest themselves in various ways, acting on the characteristics of the arc, the metal transfer, the amount of splatter and fumes formed, the arc format, the geometry of the bead and other aspects of welding. The literature on the subject reports diverse forms of instability associated with arc welding with solid wire and gas shielding (GMAW). This work aimed to define the instability phenomena associated with the GMAW process in welding with gases with a low oxidation potential. To do so, the welding current and voltages were monitored and metal transfer was filmed at high speed. The welding tests were carried out on plates of common carbon steel with a source operating at a constant current and an electrode with positive polarity. By synchronizing the filming with the welding current and voltage signals, the results showed that, during the periods of highest voltage, the transfer tended to be globular repulsive, as opposed to spray transfer during the lowest voltage periods. The synchronization of the electrical signals with the optical sensor indicates that, during periods of unstable operation, the arc is more luminous. It also showed that more fumes were generated during these periods.
[1]
R. E. Monroe,et al.
Cathodic cleaning and plasma arc welding of aluminum.
,
1968
.
[2]
Y H Fu,et al.
The influence of cathode surface microstructure on DC vacuum arcs
,
1989
.
[3]
A. E. Guile,et al.
Arc-electrode phenomena
,
1971
.
[4]
J. H. Nixon,et al.
Arc instability phenomena in GMA welding
,
1994
.
[5]
Paulo José Modenesi,et al.
The influence of small variations of wire characteristics on gas metal arc welding process stability
,
1999
.
[6]
M. Ushio,et al.
Observations of the phenomenon of abnormal arc voltage occurring in pulsed metal inert gas welding of aluminium alloy
,
2005
.
[7]
M. J. Kang,et al.
Spatter Rate Estimation in the Short-Circuit Transfer Region of GMAW
,
2003
.
[8]
D. W. Lyons,et al.
Droplet transfer in pulsed gas metal arc welding of aluminum
,
1998
.