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BOC RAPTOR 200C & 250R MIG Operating manual
Schematic of Dip Transfer
1 Short circuit
2 Necking
3 Arc re-ignition
4 Arc established
5 Arc gap shortens
6 Short circuit
12.4 Modes of Metal Transfer
The mode or type of metal transfer in MIG 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 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.
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 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-
1
2
Current (A)
Voltage (V)
Short circuit cycle
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.
Metal-cored wires transfer metal in dip mode at low currents just
like solid MIG wires. This transfer mode is used for all positional
work with these types of wire.
Globular Transfer
Metal transfer is controlled by slow ejection resulting in large,
irregularly-shaped 'globs' falling into the weld pool under
the action of gravity. Carbon dioxide gas drops are dispersed
haphazardly. With argon-based gases, the drops are not as large
and are transferred in a more axial direction. There is a lot of
spatter, especially in carbon dioxide, resulting in greater wire
consumption, poor penetration and poor appearance. Globular
transfer occurs between the dip and spray ranges. This mode of
transfer is not recommended for normal welding applications and
may be corrected when encountered by either decreasing the arc
voltage or increasing the amperage. Globular transfer can take
place with any electrode diameter.
Basic flux-cored wires tend to operate in a globular mode or in
a globular-spray transfer mode where larger than normal spray
droplets are propelled across the arc, but they never achieve a true
spray transfer mode. This transfer mode is sometimes referred to as
non-axial globular transfer.
Self-shielded flux-cored wires operate in a predominantly globular
transfer mode although at high currents the wire often 'explodes'
across the arc.
3
4
5
Time
Arcing cycle
6
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