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Home > Ordnance Documents and other related manuals > > Electrodes Defects and Their effects.
Direct Current Arc-Welding Electrodes.
Automotive Welding Processes, Materials, and Identification

Welding Operations, I
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WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
arc blow (an unstable arc condition) that is particularly harmful
when  welding  in  corners  or  restricted  places  and  when  high
currents, as required in thick sections, are used.  Arc blow, in
these cases, causes blowholes and slag inclusions in the weld as
well as a lack of fusion.
(2) Alternating current is used in atomic hydrogen welding, and
in those carbon-arc processes that require the use of two carbon
electrodes, in order that a uniform rate of welding and electrode
consumption may be accomplished.  In carbon-arc processes, where
one  carbon  electrode  is  used,  straight  polarity  with  direct
current is recommended because the electrode is thus consumed at
a slower rate.
i.
Electrode Defects and their Effects.
(1) If  certain  elements,  or  their  oxides,  are  present  in
electrode coatings, they will materially effect the stability of
the  arc.
If  these  impurities  are  present  in  considerable
quantities of light or heavy coatings, the electrodes will not be
able to compensate for defects in the wire.  In bare electrodes,
because there is almost no coating on the wire, the composition
and uniformity of the wire is an important factor in the control
of arc stability.
Impurities in the wire can cause the arc to
become unstable.
(2) Aluminum or aluminum oxide, even when present in quantities
not  exceeding  0.01  percent,  will  cause  the  arc  to  become
unstable.
Silicon, silicon dioxide, and iron sulfate also tend
to make the arc unstable.
But, iron oxide, manganese oxide,
calcium oxide, and iron sulfide tend to stabilize the arc.
(3) When phosphorous or sulfur are present in excess of 0.04
percent,  they  will  impair  the  weld  metal  because  they  are
transferred from the electrode to the molten metal.  Phosphorous
causes grain growth, brittleness, and "cold shortness" (brittle
when below red heat) in the weld, and these defects increase in
magnitude as the carbon content of the steel increases.
Sulfur
acts as a slag, breaks up the soundness of the weld metal, and
causes "hot shortness" (brittle when above red heat).  Sulfur is
particularly harmful to bare, low-carbon steel electrodes with a
low manganese
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