WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
d. Types of Electrodes.
There are three different types of
electrodes.
They are: bare, thinly coated, and shielded-arc or
heavy-coated electrodes.
(1) Bare Electrodes.
Bare electrodes are made of wire
compositions required for specific applications and have no
coatings other than those required in wire drawing.
These wire
drawing coatings have some slight stabilizing effect on the arc,
but are otherwise of no consequence.
Bare electrodes are used
for welding manganese alloy steel, and other purposes where a
coated electrode is not required or is undesirable.
A
diagrammatic sketch of the transfer of metal across the arc of a
bare electrode is shown in figure 1, view A, on the following
page.
(2) Thinly Coated Electrodes.
(a) Thinly coated electrodes are made of a wire of a definite
A thin coating is applied on the surface of the
electrode by washing, dipping, brushing, spraying, tumbling, or
wiping to improve the stability and characteristics of the arc
stream.
They are listed under the E45 series in the electrode
identification system described in paragraph 2c, beginning on
page 3.
(b) The coating on these types of electrodes generally serves
the functions described below:
1 It dissolves or reduces impurities, such as oxides, sulfur,
and phosphorous, and thus keeps impurities out of the weld
deposit.
2 It reduces the adhesive force between the molten metal and
the end of the electrode, or changes the surface tension of the
molten metal so that the globules of metal leaving the end of the
electrode are smaller and more frequent, thus making the flow of
molten metal more uniform and continuous.
3 It increases the stability of the arc by introducing
materials readily ionized into the arc stream.
That is, the
coating fuels the arc by providing smaller particles when the
electric charge occurs.
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