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Fastening
& Joining Methods
Arc
Welding
Arc welding processes use a welding power
supply to create and maintain an electric
arc between an electrode and the base material
to melt metals at the welding point. They
can use either direct (DC) or alternating
(AC) current, and consumable or non-consumable
electrodes. The welding region is sometimes
protected by some type of inert or semi-inert
gas, known as a shielding gas, and filler
material is sometimes used as well.
Arc welding is one of several fusion
processes for joining metals. By applying
intense heat, metal at the joint between
two parts is melted and caused to intermix
- directly, or more commonly, with an intermediate
molten filler metal. Upon cooling and solidification,
a metallurgical bond is created. Since the
joining is an intermixture of metals, the
final weldment potentially has the same
strength properties as the metal of the
parts. This is in sharp contrast to non-fusion
processes of joining (i.e. soldering, brazing
etc.) in which the mechanical and physical
properties of the base materials cannot
be duplicated at the joint.
In arc welding, the intense heat needed
to melt metal is produced by an electric
arc. The arc is formed between the actual
work and an electrode (stick or wire) that
is manually or mechanically guided along
the joint. The electrode can either be a
rod with the purpose of simply carrying
the current between the tip and the work.
Or, it may be a specially prepared rod or
wire that not only conducts the current
but also melts and supplies filler metal
to the joint. Most welding in the manufacture
of steel products uses the second type of
electrode.
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