Tungsten Electrodes

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.

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.

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.