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30
DC TIG Welding
The DC power source uses what is known as DC (direct current) in which the main elec-
trical component known as electrons ow in only one direction from the negative pole
(terminal) to the positive pole (terminal). In the DC electrical circuit there is an electrical prin-
ciple at work which should always be taken into account when using any DC circuit. With a DC
circuit 70% of the energy (heat) is always on the positive side. This needs to be understood
because it determines what terminal the TIG torch will be connected to (this rule applies to all
the other forms of DC welding as well ).
DC TIG welding is a process in which an arc is struck between a TUNGSTEN
electrode and the metal work piece. The weld area is shielded by an inert
gas ow to prevent contamination of the tungsten, molten pool and weld
area.
When the TIG arc is struck the inert gas is ionized and superheated chang-
ing it’s molecular structure which converts it into a plasma stream. This
plasma stream owing between the tungsten and the work piece is the
TIG arc and can be as hot as 34,232°F. It is a very pure and concentrated
arc which provides the controlled melting of most metals into a weld pool.
TIG welding oers the user the greatest amount of exibility to weld the
widest range of material and thickness and types. DC TIG welding is also
the cleanest weld with no sparks or spatter.
LIFT ARC IGNITION for TIG (tungsten inert gas) Welding
Lift Arc is a form of arc ignition where the machines has low voltage on the electrode to only a few volts, with a cur-
rent limit of one or two amps (well below the limit that causes metal to transfer and contamination of the weld or
electrode). When the machine detects that the tungsten has left the surface and a spark is present, it immediately
(within microseconds) increases power, converting the spark to a full arc. It is a simple, safe lower cost alternative
arc ignition process to HF (high frequency) and a superior arc start process to scratch start.
arc ignition
established
TIG arc
gas ow
The intensity of the arc is proportional to the current that ows from the
tungsten. The welder regulates the welding current to adjust the power of
the arc. Typically thin material requires a less powerful arc with less heat to
melt the material so less current (amps) is required, thicker material requires
a more powerful arc with more heat so more current (amps) are necessary
to melt the material.
30%
70%
high
current
low
current
power source
argon gas
nozzle
Lay the nozzle on the job
without the tungsten touch-
ing the work
Rock the torch sideways so
that the tungsten touches the
work & hold momentarily
Rock the torch back in the
opposite direction, the arc will
ignite as the tungsten lifts o
the work
Lift the torch to maintain the
arc
tungsten touches
the work
tungsten o the
work
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