©
COPYRIGHT 1998 THE ESAB GROUP, INC. LESSON
II 2.7
ELECTROSLAG AND ELECTROGAS WELDING
Electroslag Welding (ESW)
and Electrogas Welding (EGW)
comprise only a minor portion
of all welding done in the country,
but they are uniquely adapted to certain applications, primarily
the joining of very thick materials. The joining of a 12 inch material along
a 40 foot line
is not an uncommon application for the Electroslag process.
2.7.1
Electroslag
Welding (See
Figure 21) is technically not an arc welding process,
although it utilizes a current carrying
consumable electrode. The only time there is an arc
between the electrode and the work
piece is when current is initially charged through the electrode.
This initial charge heats a layer of loose flux that becomes molten and
extinguishes the
arc. 2.7.2
Flux
- The flux used in ESW is high in electrical resistance.
As current is applied, enough
heat is generated from this resistance to keep the flux, base metal, and electrode
in a molten state.
This axis of the weld joint is on a vertical plane. The two pieces
of metal, usually of
the same thickness, are positioned so that there is an opening between them. One
or more electrodes
are fed into the opening through a welding bead that travels vertically as the
joint is filled.
To contain the molten puddle, water cooled copper shoes or dams are placed
on the sides of
the vertical cavity. As the weld joint solidifies, the dams move vertically
so as to always
remain in contact with the molten puddle. 2.7.3
Process
- A variation of ESW is the consumable guide method.
The process is the same
with this method except that the guide tube that feeds the electrode to the molten
pool is WATER
INLET/OUTLET COPPER
SHOE BASE
METAL SOLIDIFIED
METAL WELD
POOL MOLTEN
FLUX GUIDE
TUBE (CONSUMABLE
GUIDE METHOD) ELECTRODE
ELECTROSLAG WELDING
FIGURE 21
