Lincoln Electric IM556 AC-235 - Manual (Page 12)

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FIGURE 2—The welding arc.
The function of the covered electrode is much more than
simply to carry current to the arc. The electrode is com-
posed of a core of metal wire around which has been
extruded and baked a chemical covering. The core wire
melts in 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 the protective slag.
The principal differences between various types of elec-
trodes are in their coatings. By varying the coating, it is
possible to greatly alter the operating characteristics of
electrodes. By understanding the differences 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 welding is
more or less futile. With complete mastery of the four,
welding will be easy.
1. The Correct Welding Position
Beginners will find it easier to learn how to control the
welding arc using the two-handed technique shown below.
This requires the use of a headshield.
a. Hold the electrode holder in your right hand.
b. Touch your left hand to the underside of your right.
c. Put the left elbow against your left side.
(For welding left-handed it is the opposite.)
If you are using a hand shield, hold the electrode holder in
your right hand and the hand shield in your left. (For weld-
ing left-handed it is the opposite.)
Whenever possible, weld from left to right (if right-hand-
ed). This enables you to see clearly what you are doing.
Hold the electrode at a slight angle as shown.
2. The Correct Way to Strike an Arc
Be sure the work clamp makes good electrical contact to
the work.
Lower your headshield or hold the hand shield in front of
your face. Scratch the electrode slowly over the metal and
you will see sparks flying. While scratching, lift the elec-
trode 1/8" (3.2mm) and the arc is established.
NOTE: If you stop moving the electrode while scratching,
the electrode will stick.
NOTE: Most beginners try to strike the arc by a fast jab-
bing motion down on the plate. Result: They either stick 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 to 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.