Tungsten Electrode for TIG welding:
Tungsten electrodes are used when arc welding with the Tungsten
Inert gas (TIG) process or when plasma welding. In both processes
the electrode, arc and weld pool are protected from atmospheric
contamination by an inert gas. A tungsten electrode is used because
it can withstand very high temperatures with minimal melting or
erosion. Tungsten electrodes are made by powder metallurgy and are
formed to size after sintering.
TIG welding tungsten electrodes usually contain small quantities of
other metallic oxides which can offer the following benefits:-
- facilitate arc starting
- increase arc stability
- improve current-carrying capacity of the rod.
- reduce the risk of weld contamination
- increase electrode life
Oxides used are primarily those of zirconium, thorium, lanthanum,
yttrium or cerium. Additions are usually of order 1%-4%. All these
oxides greatly improve arc initiation, especially when direct
current (DC) welding is employed. Thorium oxide (thoria) has been
used for many years having been found effective in terms of long
life and thermal efficiency. Zirconium oxide (zirconia) has been
commonly used for alternating current (AC) TIG welding, normally
for welding aluminium.
| Type | Grade | Color | Chemical Composition (%) | Features |
| R.E | Impurities | W |
| Pure | WP | Green | / | ≤0.05 | Balance | Non-radioactive, AC welding, aluminum, magnesium, their alloys |
| Thorium | WT10 | Yellow | 0.9~1.1 | ≤0.05 | Balance | Excellent electron emission, overall performances, high
current-carrying capacity radioactivity, DC welding, carbon steel,
stainless steel, nickel and titanium alloys. |
| WT20 | Red | 1.8~2.2 | ≤0.05 | Balance |
| WT30 | Purple | 2.8~3.2 | ≤0.05 | Balance |
| WT40 | Orange | 3.8~4.2 | ≤0.05 | Balance |
| Lanthanum | WL10 | Black | 0.9~1.1 | ≤0.05 | Balance | Non-radioactive, excellent electric conductivity and welding
capacity, high current-carrying capacity, minimum ratio of burnt
area, DC welding |
| WL15 | Gold | 1.3~1.7 | ≤0.05 | Balance |
| WL20 | Blue | 1.8~2.2 | ≤0.05 | Balance |
| Cerium | WC10 | Pink | 0.9~1.1 | ≤0.05 | Balance | Non-radioactive, easier arc initiation under low current
circumstances, low arc- maintaining current, pipelines, small
components and discontinuous welding |
| WC15 | Orange | 1.3~1.7 | ≤0.05 | Balance |
| WC20 | Grey | 1.8~2.2 | ≤0.05 | Balance |
| Yttrium | WY20 | Blue | 1.8~2.2 | ≤0.05 | Balance | Non-radioactive, long and slim arc beam with high compression,
deeper burning groove under medium and high current circumstances |
| Compound | WX | Cyan | 1.0~5.0 | ≤0.05 | Balance | Different additives |
All the types of tungsten electrodes can be made with surface
conditions of drawn, electrolytic polished, ground and swaged.
The lanthanated tungsten electrodes are becoming more popular in
the circle of welding in the world soon after they were developed,
because of their good welding performance. The electric
conductivity of lanthanated tungsten electrode is most closed to
that of 2% thoriated tungsten electrodes. Welders can easily
replace thoriated tungsten electrodes with lanthanated tungsten
electrodes at either AC or DC and not have to make any welding
program changes.
The radioactivity from thoriated tungsten electrodes can thus be
avoided. Another advantage of lanthanated tungsten electrodes is
being able to be bear high current and having the lowest burn-loss
rate.
| Trade mark | Added
impurity | Impurity
quantity | Other
impurities | Tungsten | Electric discharged
power | Color
sign |
| WL10 | La2O3 | 0.80 - 1.20% | <0.20% | The rest | 2.6 - 2.7 | Black |
| WL15 | La2O3 | 1.30 - 1.70% | <0.20% | The rest | 2.8 - 3.0 | Yellow |
| WL20 | La2O3 | 1.80 - 2.20% | <0.20% | The rest | 2.8 - 3.2 | Sky blue |
2% lanthanated tungsten electrodes contains 2% Lanthanum oxide
(La2O3) that is also a non-radioactive material. It has good
welding performance. Its electric conductivity is closed to that of
the 2% thoriated tungsten electrodes. Lanthanated electrodes
operate at a slightly different arc voltage than Thoriated or
ceriated electrodes. Were developed around the same time as
Ceriated tungsten to help combat the increasing awareness of the
radioactivity of Thoriated Tungsten electrodes.
Application:Generally used to weld carbon & stainless steels,
nickel alloys and titanium.
