Specifications

18
Lift Arc™
During this method of arc initiation, the
tungsten is actually touching the workpiece.
This occurs at very low amperage that is only
sufficient to pre-heat, not melt the tungsten.
As the tungsten is moved off the plate, the arc
is established. With this method, there is little
chance of tungsten inclusion occurring.
3.3 Process Variables
DCEN
When direct-current electrode-negative
(straight polarity) is used:
•Electronsstrikethepartbeingweldedata
high speed.
•Intenseheatonthebasemetalisproduced.
•Thebasemetalmeltsveryquickly.
•Ionsfromtheinertgasaredirectedtowards
the negative electrode at a relatively slow rate.
•Directcurrentwithstraightpolaritydoesnot
require post-weld cleaning to remove metal
oxides.
Use of DCEN
For a given diameter of tungsten electrode,
higher amperage can be used with straight
polarity. Straight polarity is used mainly for
welding:
•Carbonsteels
•Stainlesssteels
•Copperalloys
The increased amperage provides:
•Deeperpenetration
•Increasedweldingspeed
•Anarrower,deeper,weldbead.
DCEN - Narrow bead - Deep penetration
Nozzle
Ions Electrons
DCEP
The DCEP (reverse polarity) are different from
the DCEN in following ways:
•Highheatisproducedontheelectroderather
on the base metal.
•Theheatmeltsthetungstenelectrodetip.
•Thebasemetalremainsrelativelycool
compared to sing straight polarity.
•Relativelyshallowpenetrationisobtained.
•Anelectrodewhosediameteristoolargewill
reduce visibility and increase arc instability.
Use of DCEP
•Intenseheatmeansalargerdiameterof
electrode must be used with DCEP.
•Maximumweldingamperageshouldbe
relatively low (approximately six times lower
than with DCEN).
DCEP - Wide bead - Shallow penetration
Nozzle
Ions Electrons