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VIPER MIG 135
OPERATING MANUAL
12. TIG: Welding Guide
12.1 DC TIG Welding
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 ).
DC TIG welding is a process in which an arc is struck between a tungsten electrode and the metal workpiece. 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 ionised and superheated, changing its molecular structure, which converts it into a plasma
stream. This plasma stream flowing between the tungsten and the workpiece is the TIG arc and can be as hot as 19,000°C.
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 highest amount of flexibility to weld the widest range of material thickness and types. DC TIG welding is
also the cleanest weld with no sparks or spatter.
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.
12.2 Lift Arc Ignition for TIG (Tungsten Inert Gas) Welding
Lift Arc is a form of arc ignition where the tungsten electrode is touched to the workpiece and then pulled upwards to
initiate an arc. 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.
Lift Arc ignition allows the arc to be started easily in DC TIG by simply touching the tungsten to the workpiece and lifting
it to start the arc. This prevents the tungsten tip from sticking to the workpiece and breaking the tip from the tungsten
electrode. There is a particular technique called “rocking the cup” used in the Lift Arc process that provides easy use of
the Lift Arc function.
30%
70%
70%
Power Source
Low Current
High Current
Gas flow
Tungsten off
the workpiece
Tungsten touches
the workpiece
Arc ignition
Established
TIG arc
Lay the nozzle on the job without
the tungsten touching 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 off the work.
Lift the torch to maintain the arc.
