Electrode Sharpening
Tungsten alloy electrodes offer improved
• arc striking
• arc stability
• current capacity
Tungsten alloy electrodes for DCEN
• Thoriated, AWS colour code RED (2%)
• Lanthanium, AWS colour code BLACK (1%)
• Cerium oxide, AWS colour code ORANGE (2%)
3.4 Consumables
The consumables used in the GTAW process
include the shielding gas and the filler material.
The shielding gas must be essentially inert
(i.e. argon or helium) although very small
amounts of active gases may be used in certain
applications.
This is because active (oxidising) gases like CO
2
and Oxygen react to tungsten.
The process may be used without filler material
addition, but if a filler is required this is added
in the form of a rod that is introduced into the
leading edge of the weld pool, either manually
or by a wire feed mechanism
A filler is added in the form of a rod introduced
into the leading edge of the weld pool, either
manually or by a wire feed mechanism.
3.5 Control of the Process
The main control parameters for the GTAW
process are:
• current
• travel speed
• filler wire addition
The current is increased to enable higher
travel speeds to be obtained (for a given plate
thickness or weld size) although at high current
levels the arc may become very fierce and
undercut may occur. In single electrode GTAW
applications the occurrence of undercut limits
the maximum speed and current. Filler wire may
be used to cool the weld pool and this may be
beneficial for complex positional joints and for
surfacing applications.
11
Shape of tungsten electrode tip – DCEN
Safety glasses and
respirator are worn
Silicon carbide
grinding wheel
Electrode held firmly in hands, resting on tool rest.
Hands well clear of grinding wheel.
