Operation, Figure 5 – Lincoln Electric POWER-ARC IM871-A User Manual

Page 25

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B-10

OPERATION

B-10

POWER-ARC 5500

The function of the covered electrode is much more
than simply to carry current to the arc. The electrode
is composed of a core metal wire around which has
been extruded and baked a chemical covering. The
core wire melts into the arc and tiny droplets of molten
metal shoot across the arc into the molten pool. The
electrode provides additional filler metal for the joint to
fill the groove or gap between the two pieces of the
base metal. The covering also melts or burns in the
arc. It has several functions. It makes the arc steadier,
provides a shield of smoke-like gas around the arc to
keep oxygen and nitrogen in the air away from the
molten metal, and provides a flux for the molten pool.
The flux picks up impurities and forms a protective
slag. The principle differences between the various
types of electrodes are in their coatings. By varying
the coating, it is possible to greatly alter the operating
characteristics of electrodes. By understanding the dif-
ferences in the various coatings, you will gain a better
understanding of selecting the best electrode for the
job you have at hand. In selecting an electrode, you
should consider:
1. The type of deposit you want, e.g., mild steel,

stainless, low alloy, hardfacing.

2. The thickness of the plate you want to weld.
3. The position it must be welded in (downhand,

out-of-position).

4. The surface condition of the metal to be welded.
5. Your ability to handle and obtain the desired

electrode.

Four simple manipulations are of prime importance.
Without complete mastery of these four, further
attempts at welding are futile.

With complete mastery

of the four, welding will be easy.

1. The Correct Welding Position

Illustrated is the correct welding position for
right-handed people. (For left-handed people it is
opposite.)

Whenever possible, weld from left to right (if right-
handed). This enables you to see clearly what you
are doing.

Hold the electrode at a slight angle as shown in
Figure 5.

Figure 5

15-20°

90°

side view

end view

Correct Welding Position

2. The Correct Way to Strike An Arc

Be sure the work clamp makes good electrical contact
to the work.
Lower your headshield and scratch the electrode
slowly over the metal, and you will see sparks fly.
While scratching, lift the electrode 1/8” (3.2mm) and
the arc is established.

NOTE: If you stop moving the electrode while
scratching, the electrode will stick. Most beginners try
to strike the arc by a fast jabbing motion down on the
plate. Result: They either stick their electrode or their
motion is so fast that they break the arc immediately.

3. The Correct Arc Length

The arc length is the distance from the tip of the
electrode core wire to the base metal.
Once the arc has been established, maintaining the
correct arc length becomes extremely important. The
arc should be short, approximately 1/16 to 1/8” (1.6-
3.2mm) long. As the electrode burns off, the electrode
must be fed to the work to maintain correct arc length.

The easiest way to tell whether the arc has the correct
length is by listening to its sound. A nice, short arc has
a distinctive, “crackling” sound, very much like eggs
frying in a pan. The incorrect, long arc has a hollow,
blowing or hissing sound.

4. The Correct Welding Speed

The important thing to watch while welding is the pud-
dle of molten metal right behind the arc. DO NOT
WATCH THE ARC ITSELF. The appearance of the
puddle and the ridge where the molten puddle solidi-
fies indicates correct welding speed. The ridge should
be approximately 3/8” (9.5mm) behind the electrode.

Most beginners tend to weld too fast, resulting in a
thin, uneven, “wormy” looking bead. They are not
watching the molten metal.

IMPORTANT: It is not generally necessary to weave
the arc forward, backward or sideways. Weld along at
a steady pace, and you will have an easier time.

NOTE: When welding on thin plate, you will find that
you have to increase the welding speed, whereas
when welding on heavy plate, it is necessary to go
more slowly to ensure fusion and penetration.

Ridge where puddle
solidifies

Molten puddle

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