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Schematic of Globular Transfer
Large droplet
6.4 Modes of metal transfer
The mode or type of metal transfer in MIG/MAG
and MCAW welding depends upon the current, arc
voltage, electrode diameter and type of shielding
gas used. In general, there are four modes of metal
transfer.
Modes of metal transfer with FCAW are similar to
those obtained in MIG/MAG welding, but here
the mode of transfer is heavily dependent on the
composition of the flux fill, as well as on current
and voltage.
The most common modes of transfer in FCAW are:
Dip transfer
•
Globular transfer
•
Spray transfer
•
Pulsed arc transfer operation has been applied
•
to flux-cored wires but, as yet, is not widely used
because the other transfer modes are giving
users what they require, in most cases.
20
Schematic of Spray Transfer
Gas shroud
Wire
Splatter
Workpiece
Dip Transfer
Also known as short-circuiting arc or short-arc, this
is an all-positional process, using low heat input.
The use of relatively low current and arc voltage
settings cause the electrode to intermittently
short-circuit with the weld pool at a controlled
frequency. Metal is transferred by the wire tip
actually dipping into the weld pool and the short-
circuit current is sufficient to allow the arc to be
re-established. This short-circuiting mode of metal
transfer effectively extends the range of MIG/MAG
welding to lower currents so thin sheet material
can readily be welded. The low heat input makes
this technique well-suited to the positional welding
of root runs on thick plate, butt welds for bridging
over large gaps and for certain difficult materials
where heat input is critical. Each short-circuit
causes the current to rise and the metal fuses off
the end of the electrode. A high short-circuiting
frequency gives low heat input. Dip transfer occurs
between ±70-220A, 14–23 arc volts. It is achieved
using shielding gases based on carbon dioxide and
argon.
Shielding gas
Droplets
Weld
Workpiece
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