V4.0
200A Multi-Process Welder with LCD Display
8785115
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37
DC TIG WELDING
WARNING! Disconnect the Electrode Holder cable from the machine before
using TIG function. If the cable is not disconnected, welding voltage is present
and can cause arcing or flash.
The power source uses direct current (DC). 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 ionized and superheated, changing
its molecular structure into a plasma stream. This plasma stream flowing
between the tungsten and the workpiece is the TIG arc and can be as hot as
18,000 °C (34,232 °F). A pure and concentrated arc 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 ignition allows the arc to start easily in DC TIG by simply touching the
tungsten to the workpiece and lifting it up to start the 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.
