Instructions / Assembly

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GMAW
Glossary
A
node
T
he positive end of the welding circuit for a given arc
welding process. Anode may reference the particular positive
pole of a power source or it may reference the direct current
positive region of the welding arc.
Axial Spray Transfer The high-energy mode of metal transfer in
GMAW, which is characterized by a fine, axial stream of molten
d
roplets from the end of the electrode.
CAC-A A carbon arc cutting process variation that removes
m
olten metal with a jet of air.
Cathode The negative end of the welding circuit for a given arc
w
elding process. Cathode may reference the negative pole of
the power source or it may reference the negative cathode
region of the welding arc.
Current Density The electrode current divided by the cross
sectional area of the electrode. Important here is the concept
that there is maximum current that can be applied to a given
electrode diameter. Wire feed speeds beyond the maximum
current density result in additional deposition rate.
GMAW American Welding Society acronym for gas metal arc
welding. GMAW is an arc welding process that employs an arc
between continuous filler metal and the molten weld pool. The
electrode is either a solid or a tubular metal-cored electrode.
Externally supplied shielding gas is required to protect the
molten weld pool.
Globular Transfer A mode of metal transfer in GMAW charac-
terized by large irregularly shaped metal drops from the end of
the electrode, and it is commonly associated with high spatter
levels. The globular transfer metal transfer mode occurs at arc
voltages above those used for short-circuiting transfer, but below
axial spray transfer.
GMAW-S Gas metal arc short-circuiting transfer is a low heat
input mode of metal transfer in which the molten metal transfers
from the electrode to the work piece during repeated short
circuiting events. This process variation of GMAW lends itself to
the joining of sheet metal range of base material.
GMAW-P Metal transfer modes of GMAW, which uses the
advantages of the axial spray transfer mode. The pulsed
transfer mode relies on current excursions beyond axial spray,
which alternate with low current, to produce an average current.
The frequency of the pulsed current cycle occurs many times
per second. Designed to overcome lack of fusion defects,
reduce weld spatter levels, and weld out-of-position, the pulsed
spray transfer provides higher average currents than the short-
circuiting mode of metal transfer. The average current is less
than is seen in axial spray transfer.
Inert Shielding Gas Shielding gas for GMAW such as argon
and helium, which do not react chemically with the molten pool.
Aluminum, magnesium, copper, and titanium filler alloys require
the use of 100% inert gases. Carbon steel, stainless steel, and
nickel alloys usually provide improved arc performance with
small additions of reactive gases.
I
nductance
A
n essential component for the successful opera-
t
ion of short-circuiting transfer. Inductance provides control of the
rate of rise of short-circuit current. Inductance control has the
effect of reducing spatter loss and controlling the level of spatter
generated by traditional short-circuiting metal transfer. Adding
i
nductance to the arc increase the amount of time that the arc is
on, increases the transferred metal droplet size, and adds to the
puddle fluidity. The finished weld bead appears flatter,
smoother, and exhibits excellent weld toe wetting.
MIG A non-standard term used to describe GMAW or its variants.
The acronym refers to Metal Inert Gas welding and it references
the use of inert gases such as argon and helium.
Metal-Cored Electrode Composite tubular filler metal electrode
consisting of a metal sheath and a core of powdered metals,
scavengers, and deoxidizers. The finished weld has the appear-
ance of a gas metal arc weld, but with larger slag islands.
External gas shielding is required.
MAG Used to describe GMAW or its variants, the acronym
refers to Metallic Active Gas, and it references the use of carbon
dioxide shielding gas. The term is common in Europe.
Pinch Current The electromagnetic force relates to the
magnitude of the welding current responsible for a given mode
of metal transfer. The pinch current is larger in magnitude for
axial spray transfer than it is for globular transfer, and globular
transfer has a higher pinch current than does short-circuiting
transfer.
Power Lead The welding current cable, which carries the
welding current to the electrode.
Power Source An electrical apparatus designed to supply
current and voltage suitable for welding, thermal cutting, or
thermal spraying.
Pulsed Spray Transfer GMAW-P is a metal transfer mode of
GMAW, which uses the advantages of the axial spray transfer
mode. The pulsed transfer mode relies on current excursions
beyond axial spray, which alternate with low current, to produce
an average current. The frequency of the pulsed current cycle
occurs many times per second. Designed to overcome lack of
fusion defects, pulsed spray transfer provides higher average
currents than the short-circuiting mode of metal transfer.
Reactive Power Source A power source designed to provide
output, based upon feedback from the welding arc. This type of
power source design is primary for the Surface Tension Transfer™
welding process. The reactive power source for Surface Tension
Transfer is neither constant current nor constant voltage.
Reactive Shielding Gas Shielding gases such as carbon
dioxide (CO
2
) and oxygen (O
2
) are reactive because they have a
chemical interaction with the molten weld pool.
Short-Circuit in arc welding, is the physical contact between the
electrode and the work piece.
Short-Circuiting Transfer A low heat input mode of metal
transfer in which the molten metal transfers from the electrode to
the work piece during repeated short-circuit. This process
variation of GMAW lends itself to the joining a range of sheet
metal base materials.