30%
70%
High
current
Low
current
Power source
Argon gas
Nozzle
Arc ignition
Established
TIG arc
Gas flow
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
Tungsten touches
the work
Tungsten off the
work
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
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 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 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.
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.
VIPER MIG 185 Manual |
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DC TIG WELDING GUIDE
