LESSON VII
©
COPYRIGHT 2000 THE ESAB GROUP, INC. cause
the shielding gas keeps atmospheric nitrogen from the weld zone. The
manufacturer’s shielding gas recommendation
should be followed. Shielding gas flow rates
of 30 to 45 cubic feet per hour are used depending on the electrode size, electrode
extension, and other welding conditions.
7.4.3
Electrode
Extension -
Electrode extension is the length of an electrode protrud-
ing beyond the end of the contact tip
during welding. This dimension is commonly referred
to as “electrical stickout”
and is relatively short when using gas shielded flux cored elec-
trodes (3/4" to 1-1/2"). This
short electrical stickout with a relatively high welding current
produces narrow, deep penetrating welds.
7.4.4
All-Position
Electrodes -
Gas shielded, all-position flux cored electrodes con-
tain ingredients in the core that produce
a fast freezing slag, and the proper puddle fluidity for
vertical, overhead, or other out-of-position welding. They are available
in .045", .052", and
1/16" diameters. Since the slag helps hold the puddle, the welding voltage
and current may
be relatively high, resulting in high deposition rates. The deep penetration
of these electrodes
limits the minimum material thickness to 1/8" in the vertical position, and 3/16"
in the flat or
horizontal position. 7.4.5
Mild
Steel Electrodes
- Gas shielded mild steel electrodes are available for
general purpose welding, welding through
rust and mill scale of varying degrees, out-of-position
welding, and for applications when high mechanical properties or high
impact values are necessary. Electrodes
designed for high deposition rates and high deposition
efficiency are also available. Most of the mild steel electrodes utilize
CO2 as the shielding
gas; however, some may use Argon/CO2 mixtures.
7.4.6
Low
Alloy Electrodes
- Gas shielded flux cored electrodes are widely used
for welding
the low alloy, high strength steels. They are available for welding the
carbon-molybdenum, chromium-molybdenum,
nickel, manganese-molybdenum and the high
strength quenched and tempered steels. The combination of an external gas
shield and the
fluxing elements in the core produce high purity weld metal.
7.5 SELF-SHIELDED
ELECTRODES Self-shielded
electrodes rely solely on the materials in the core of the wire for shielding
the arc from the
atmosphere, purifying the weld metal and providing the slag formers neces-
sary to protect the molten weld puddle.
These electrodes do not rely on gas shielding as the
gas shielded types do; therefore, they can operate more effectively in outdoor
environ- ments
without a windscreen.
