Self-Shielded Fcaw (Fluxed-Cored Arc Welding); Gmaw (Gas Metal Arc Welding) - Lincoln Electric LTW1 Manual De Instrucciones

LEARNING TO WELD
SELF-SHIELDED FCAW
(FLUX-CORED 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.
DRAG TECHNIQUE
Cored Wire
Protective Slag
Weld Metal
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.
WARNING
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 a welding helmet 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 ingredients around which a steel sheath has
been formed. It is simply a stick electrode turned inside out in a
continuous 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 steadier, 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
settings to be used.
Figure 4 illustrates the GMAW (Also referred to as MIG) welding arc.
Solid wire does not contain fluxes or ingredients to form its own
shielding, and no slag forms to protect the molten weld metal. For this
reason, a continuous, even flow of shielding gas is needed to protect
the molten weld metal from atmospheric contaminants such as
oxygen and nitrogen. Shielding gas is supplied through the gun and
Burning of core materials
cable assembly, through the gas nozzle, and into the welding zone.
inside the wire electrode
provides a gas to shield
the molten metal as it
solidifies.
Arc Stream
Weld Puddle
DIRECTION OF TRAVEL
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 shielding, thus we have Gas Metal Arc
Welding. FCAW uses the melting or burning of the core ingredients for
shielding, 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"; you may also 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.
GMAW
(GAS METAL ARC WELDING)
FIGURE 4
PUSH TECHNIQUE
Contact Tip
Solid wire
electrode
Base metal
Gas nozzle
Shielding gas
Weld metal
DIRECTION OF TRAVEL