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3
LEARNING TO WELD
3
SELF-SHIELDED FCAW (FLUX CORE
ARC WELDING)
Figure 3 illustrates the action taking place in the self-
shielded FCAW (Innershield) welding arc. It closely
resembles what is actually seen while welding.
FIGURE 3
The “arc stream” is seen in the middle of the picture.
This is the electric arc created by the electric current
flowing through the space between the end of the wire
electrode and the base metal. The temperature of this
arc is about 6000°F, which is more than enough to
melt metal.
The arc is very bright, as well as hot, and cannot be
looked at with the naked eye without risking painful
injury. A very dark lens, specifically designed for arc
welding, must be used with the hand or face shield
whenever viewing the arc .(ANSI Z49.1-88)
The arc melts the base metal and actually digs into it
much as water through a nozzle on a garden hose
digs into the earth. The molten metal forms a molten
pool or crater and tends to flow away from the arc. As
it moves away from the arc, it cools and solidifies.
The function of the Innershield cored wire electrode is
much more than simply to carry current to the arc. The
wire core is composed of fluxes and/or alloying ingre-
dients around which a steel sheath has been formed.
It is simply a stick electrode turned inside out in a con-
tinuous wire form.
The cored wire melts in the arc and tiny droplets of
molten metal shoot across the arc into the molten
pool. The wire sheath provides additional filler metal
for the joint to fill the groove or gap between the two
pieces of base metal.
The core materials also melt or burn in the arc and
perform several functions. They make the arc stead-
ier, provide a shield of smoke-like gas around the arc
to keep oxygen and nitrogen in the air away from the
molten metal, and provide a flux for the molten pool.
The flux picks up impurities and forms the protective
slag on top of the weld during cooling.
After running a weld bead, the slag may be removed
with a chipping hammer and wire brush. This
improves appearance and allows for inspection of the
finished weld.
Since machine size and output characteristics limit the
size and type of wire electrode which can be used, check
your Instruction Manual “Application Chart” or see the
Application Guide on the inside door of the Machine. This
will give you the proper electrode size and control set-
tings to be used.
GMAW (GAS METAL ARC WELDING)
Figure 4 illustrates the GMAW (Also referred to as MIG)
welding arc. Solid wire does not contain fluxes or ingredi-
ents to form its own shielding and no slag forms to pro-
tect the molten weld metal. For this reason, a continuous
even flow of shielding gas is needed to protect the
molten weld metal from atmospheric contaminant’s such
as oxygen and nitrogen. Shielding gas is supplied
through the gun and cable assembly, through the gas
nozzle and into the welding zone.
Important!
The MIG welding process requires that the welder has a
gas solenoid valve installed in order to control the flow of
the shielding gas. Read your Operators Manual to see if
your machine requires additional items to MIG weld.
When comparing the GMAW and FCAW processes, you
can see that the principal difference between the two lies
in the type of shielding used. GMAW uses gas for shield-
ing, thus we have Gas Metal Arc Welding. FCAW uses
the melting or burning of the core ingredients for shield-
ing, and is thus termed Self-Shielded Flux-Cored Arc
Welding.
The recommended LINCOLN Super Arc L-56 solid wire
and gas for Gas Metal Arc Welding (MIG)Metal Inert Gas
is also located in the Instruction Manual “Application
Chart” or see the Application Guide on the inside door of
the Machine. This machine is capable of welding a wide
range of mild steels in all positions, however, more skill
IS required for out-of-position welding with the GMAW
process.
FIGURE 4
Gas nozzle
Shielding gasSolid wire
electrode
Contact Tip
Base metal
Weld metal
Burning of core materials
inside the wire electrode
provides a gas to shield
the molten metal as it
solidifies.
Arc Stream
Weld Puddle
Cored Wire
Protective Slag
Weld Metal
DRAG TECHNIQUE
PUSH TECHNIQUE
DIRECTION OF TRAVEL
DIRECTION OF TRAVEL
WARNING