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No one can learn to weld simply by reading about it. Skill
comes only with practice. The following pages will help the
inexperienced operator to understand welding and develop
this skill.
5.1 The Arc-Welding Circuit
The operators knowledge of arc welding must go beyond
the arc itself. The operator must know how to control the
arc, and this requires a knowledge of the welding circuit
and the equipment that provides the electric current used
in the arc. The circuit begins where the gun cable is
attached to the welding machine. Current flows through the
gun cable, gun, and contact tip, to the wire and across the
arc. On the work side of the arc, current flows through the
base metal to the work cable and back to the welding
machine. This circuit must be complete for the current to
flow.
This machine's welding circuit has a voltage output of 47
volts DC maximum. This voltage is quite low and is only
present when the gun trigger is depressed.
To weld, the work clamp must be tightly connected to clean
base metal. Remove paint, rust, dirt or oil as necessary and
connect the work clamp as close as possible to the area
you wish to weld. This helps prevent current from going
through an unwanted path. Avoid allowing the welding
circuit to pass through hinges, bearings, electronic
components, or similar devices that can be damaged.
Always disconnect electrical devices before welding upon
FUMES AND GASES can
them.
be dangerous
Fumes and slag generated from electrodes recommended
for use with this welding machine can be toxic.
•
Avoid contact with eyes and skin.
•
Do not take internally.
•
Keep out of reach of children.
•
Follow all safety precautions found in this operating
manual.
The gun and cable assembly is held by the operator who
guides the automatically fed wire along the joint,
maintaining a contact tip to work distance of about 10 - 12
mm This is called electrical stickout. This electrical stickout
(ESO) must be properly maintained by the operator. The
electric arc is made in the gap between the work and the
tip end of a small diameter wire. When the power source is
properly set, the arc gap is maintained automatically.
Arc welding is a manual skill requiring a steady hand, good
physical condition, and good eyesight. The operator
controls the welding arc, and, therefore, the quality of the
weld made.
Page 16
Section 5 - LEARNING TO WELD
REDI-MIG 455 Remote
5.2 The Self-Shielded (Gasless)
FCAW Welding Arc (DC-)
Figure 1 illustrates the action taking place in the self
shielded gasless FCAW welding arc. It closely resembles
what is actually seen while welding.
Figure 1
Cored Wire
Protective Slag
Weld Metal
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
3300°C, 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. The very
dark lens, specifically designed for arc welding must be
used with the hand or face shield whenever viewing the
arc.
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 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.
Machine size and output characteristics limit the size and
type of wire electrode which can be used.
Burning of core materials
inside
wire
electrode
results in shield of gas.
Arc Stream
IMA 603C
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