14-BASIC WELDING TECHNIQUE
Note! This section being general welding technique guide is for reference only. Specific functions of your machine
please refer to previous chapters.
14-1 TIG welding technique
30%
70%
The DC power source uses what is known as DC (direct current) in which the main
electrical component known as electrons flow in only one direction from the
negative pole (terminal) to the positive pole (terminal). In the DC electrical circuit
there is an electrical principle 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).
Fig. 14-1-1: Heat input
Power Source
Nozzle
Argon gas
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 flow to prevent contamination of the tungsten, molten pool and weld
area.
When the TIG arc is struck the inert gas is ionized and superheated
changing it’s molecular structure which converts it into a plasma stream.
This plasma stream flowing between the tungsten and the work piece is the
TIG arc and can be as hot as 9000K+. It is a very pure and concentrated arc
which provides the controlled melting of most metals into a weld pool. TIG
welding offers the user the greatest amount of flexibility to weld the widest
range of material and thickness and types. DC TIG welding is also the
cleanest weld with no sparks or spatter.
Fig. 14-1-2: TIG arc
Low Current
High Current
Fig. 14-1-3: Low current
Fig. 14-1-4: High current
The intensity of the arc is proportional to
the current that flows 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.
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 current 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.
Gas flow
Fig. 14-1-5: Tungsten off the work Fig. 14-1-6: Tungsten touches the work Fig. 14-1-7: Arc ignition Fig. 14-1-8: Established TIG arc
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