The transfer of molten metal in large drops from a consumable electrode across the arc. See Figure G-18. See also SHORT CIRCUITING TRANSFER and SPRAY TRANSFER.
Consumable electrode arc welding processes are used extensively because filler metal is deposited more efficiently and at higher rates than is possible with other welding processes. To be most effective, the filler metal needs to be transferred from the electrode
with small losses due to spatter. Uncontrollable short circuits between the electrode and the work should be avoided to help the welder or operator to maintain stability of the process. In the case of the GMAW process, arc instability caused by erratic transfer can generate pressure fluctuations that draw air into the vicinity of the arc.
High speed photography and analysis of oscilloscope photographs are used to study the different types of transfer. Transfer through the arc stream of covered electrodes can be characterized as globular (massive drops) or as a showery spray (large number of small drops). These modes are rarely found alone; generally, metal is transferred in some combination of both. Transfer with the GMAW process varies greatly when used with argon shielding. When the current is above the transition level, the transfer mechanism can best be described as an axial spray and short circuits are non-existent. When helium or an active gas such as carbon dioxide is used for shielding, the transfer is globular and some short circuiting is unavoidable. The GMAW short circuiting arc process has been adapted to use only short circuits for transfer of the metal to the weld pool.