Electrogas Welding (EGW) - College of Eastern Utah

Electrogas Welding (EGW)
WELD 1140
College of Eastern Utah
Lon Youngberg

EGW Description
Electrogas welding is an arc welding
process that is performed on verticallyoriented
plates/structures. The process
produces an arc between a continuously
fed wire electrode and the weld pool.
The weld pool is contained by some
form of backing. External shielding gas
and pressure may or may not be used.

EGW Interesting Facts
Electroslag welding was invented first.
EGW uses either sold wire, or flux-cored wire.
Shielding gas (CO2 or Ar/CO2) is always used
with solid wire and can be used with fluxcored
wire.
EGW is a machine welding process.
Although the weld progresses in a vertical
direction, the weld is deposited in the flat
position.

Interesting Facts (cont.)
Water-cooled copper retaining shoes
are typically used on either side of the
joint to hold the molten pool in place.
EGW is commonly used for material
thicknesses between ½” and 3”.
Electrode diameters are typically from
1/16” to 1/8”

EGW
A consumable guide is often used with
short welds (about 4 ft max).
When a consumable guide is used,
none of the equipment (retaining shoes,
wire feed mechanism) moves vertically.
DCEN (reverse polarity) is normally
used. Like SAW, a CV power supply is
normally used, but CC may also be used

EGW
EGW power supplies are usually capable of
750 amps at 100% duty cycle.
Retaining shoes (dams) are typically watercooled
copper. However, steel backing strips,
ceramic backups and combinations are
sometimes used.
EGW flux-core electrodes are not the same as
FCAW (less slagging). Solid wires are
typically the same as GMAW (except bigger).

EGW
Joint designs: see fig. 7.6 and 7.7
Know the following features:
Strongbacks
Starting sump
Runoff tabs

Metallurgical Concerns
Since EGW is a high heat-input process
where a large molten puddle is used,
the cooling rate is very slow. This
condition results in large (course),
columnar grains in the weld zone and a
wide heat affected zone (HAZ). Course
grained microstructures typically lack
toughness (resistance to fracture).

Angular Distortion & Stress
Angular distortion (the “gull wing” shape of a
SMAW certification plate) is minimal for EGW
when a symmetrical joint is used.
Solidification begins at the outside edges.
The result is that the outer surfaces of the
completed weld are in compression and the
center is in tension.

EGW variables
Voltage: typically 30 to 35 volts
Amperage: 300 to 1000 amps
depending on the wire size.
Electrode Extension:
Gas shielded - usually about 1.5”
Self shielded (flux core) – 2” to 3”
Oscillation can be used

Discontinuities
Porosity
Ceterline Cracking
Incomplete fusion at the sides
Overlap
Underfill
Melt Through
Hot Cracking