TI 809-26
7.
a. Process Principles. Electrogas Welding (EGW) is very similar to Electroslag Welding (ESW), and
is used for welding thick sections, typically 50 mm to 500 mm (2 to 20 in.) in thickness, for short to
opening gap at the joint is generally set to approximately 22 mm (7/8 in.), depending on welding
equipment and material thickness, with no edge preparation generally required. Water-cooled copper
current electrode negative (DCEN) currents of 500 to 700 amperes are commonly used. The electrode is
either a solid wire, composite (cored) wire, or a flux cored wire designed for EGW. For solid wires,
or an argon-CO2 mix.
When flux cored wires are used, the shielding gas may or may not be necessary, depending upon the
weld pool and allows the welding arc to stabilize before reaching the actual joint. The arc is maintained,
and the fed electrode wire and adjacent base metal melts from the heat generated by the arc. The weld
Both the starting sump and finishing run-off tab are removed after completion of welding.
b. Filler Metal Designation, Specification and Certification. Filler materials, electrodes and fluxes
Specification for Carbon and Low-Alloy Steel Electrodes and
Electrogas Welding
classification system is summarized in Table C-19.
c. Advantages, Disadvantages and Limitations. Electrogas Welding (EGW) provides very high
vertical welding of thick steels. Time and expense is also saved in the avoidance of joint preparation,
preheating and interpass temperature control, and interpass cleaning. The joint is also free from angular
(1) EGW, if interrupted during welding, can leave major discontinuities in the joint that are difficult
to access and repair. The large grain size from the substantial heat input, and subsequent slow cooling,
disadvantage, compared to ESW, of requiring protection of the joint from wind over 8 km per hour (5
mph).
economical choice until a thickness of around 50 mm (2 in.) is welded, depending upon several factors
including the number of joints to be welded. EGW is not prequalified under AWS
, therefore
qualification testing following AWS
Section 4 is required. Angles beyond 10 to 15 degrees from
vertical may require special setups and procedures.
C-35
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