Process Variables - Linde BOC RAPTOR Operating Manual

9.3 Process variables

Process variable
DCEN
Narrow bead,
deep penetration
Nozzle
Ions Electrons
DCEP
Wide bead,
shallow penetration
Nozzle
Ions Electrons
Explanation
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
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
Usage
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
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)
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