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AC or Alternating Current - electric
current that reverses direction periodically.
Sixty cycle current travels in both directions
sixty times per second.
Arc Length - the distance from the end
of the electrode to the point where the arc
makes contact with the work surface.
Base Metal - the material to be welded.
Butt Joint - a joint between two
members aligned approximately in the
same plane.
Crater - a pool, or pocket, that is formed
as the arc comes in contact with the base
metal.
DC or Direct Current - electric current
which flows only in one direction. The
polarity (+ or -) determines which direction
the current is flowing.
DC Reverse Polarity - occurs when the
electrode holder is connected to the
positive pole of the welding machine.
Reverse Polarity directs more heat into
melting the electrode rather then the work
piece. It is used on thinner material.
DC Straight Polarity - occurs when the
electrode holder is connected to the
negative pole of the welding machine.
With straight polarity more heat is directed
to the work piece for better penetration
on thicker material.
Electrode - a coated metal wire having
approximately the same composition as
the material being welded.
Fillet Weld - approximately a triangle in
cross-section, joining two surfaces at right
angles to each other in a lap, T or corner
joint.
Flux - a coating, when heated, that
produces a shielding gas around the
welding area. This gas protects the parent
and filler metals from impurities in the air.
Flux Cored Arc Welding (FCAW) -
also called Gasless, is a welding process
used with a wire-feed welding machine.
The weld wire is tubular with flux material
contained inside for shielding.
Gas Metal Arc Welding (GMAW) -
also called MIG, is a welding process used
with a wire feed welding machine. The
wire is solid and an inert gas is used for
shielding.
Gas Tungsten Arc Welding (GTAW)
- also called TIG, is a welding process used
with welding equipment with a high
frequency generator. The arc is created
between a non-consumable tungsten
electrode and the work piece. Filler metal
may or may not be used.
Inverter - Technology that converts high
voltage AC input power into high
amperage DC welding output power
through the use of transistor-bridge and
constant current rectifier instead of a
heavy traditional transformer.
Lap Joint - a joint between two
overlapping members in parallel planes.
MIG - See “Gas Metal Arc Welding.”
Open Circuit Voltage (OCV) - the
voltage between the electrode and the
ground clamp of the welding machine
when no current is flowing (not welding).
The OCV determines how quickly the arc is
struck.
Overlap - occurs when the amperage is
set too low. In this instance, the molten
metal falls from the electrode without
actually fusing into the base metal.
Porosity - gas pockets, or cavities,
formed during weld solidification. They
weaken the weld.
Penetration - the depth into the work
piece that has been heat effected by the
arc during the welding process. A good
weld achieves 100% penetration meaning
that the entire thickness of the work piece
has been heated and resolidified. The heat
effected area should be easily seen on the
opposite side of the weld.
Shielded Metal Arc Welding
(SMAW) - also called Stick, is a welding
process with uses a consumable electrode
to support the arc. Shielding is achieved by
the melting of the flux coating on the
electrode.
Slag - a layer of flux soot that protects
the weld from oxides and other
contaminants while the weld is solidifying
(cooling). Slag should be removed after
weld has cooled.
Spatter - metal particles thrown from the
weld which cool and harden on the work
surface. Spatter can be minimized by using
a spatter resistant spray on the work piece
before welding.
Stick - See “Shielded Metal Arc
Welding.”
Tack Weld - weld made to hold parts in
proper alignment until final welds are
made.
TIG - See “Gas Tungsten Arc Welding.”
Travel Angle - the angle of the
electrode in the line of welding. It varies
from 5º to 45º depending on welding
conditions.
T Joint - made by placing the edge of
one piece of metal on the surface of the
other piece at approximately a 90º angle.
Undercut - a condition that results when
welding amperage is too high. The
excessive amperage leaves a groove in the
base metal along both sides of the bead
which reduces the strength of the weld.
Weld Pool or Puddle - a volume of
molten metal in a weld prior to its
solidification as weld metal.
Weld Bead - a narrow layer or layers of
metal deposited on the base metal as the
electrode melts. Weld bead width is
typically twice the diameter of the
Welding Terms