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Glossary of Terms
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 than 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.
Lap Joint - a joint between two overlapping members in parallel
planes.
Open Circuit Voltage (OCV) - the voltage between the electrode
and the work clamp of the welding machine when no current is
flowing (not welding). The OCV determines how quickly the arc is
struck.
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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 that 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.
Tack Weld - weld made to hold parts in proper alignment until final
welds are made.
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 electrode.
Work Angle - the angle of the electrode from horizontal, measured
at right angles to the line of welding.
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