How to "Correctly" Grind, Cut & Prepare Tungsten Welding Electrodes (11 pages)

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“The Tungsten Electrode Experts”

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Pure tungsten electrodes (EWP) contain a minimum of 99.5 percent tungsten, with no intentional alloying
elements. The current-carrying capacity of pure tungsten electrodes is lower than that of the alloyed
electrodes. Pure tungsten electrodes are used mainly with AC for welding aluminum and magnesium
alloys. The tip of the EWP electrode maintains a clean, balled end, which provides good arc stability.
They may also be used with DC, but they do not provide the arc initiation and arc stability characteristics
of Thoriated, Ceriated, or Lanthanated electrodes.


The thermionic emission of tungsten can be improved by alloying it with metal oxides that have very low
work functions. As a result, the electrodes are able to handle higher welding currents without failing.
Thorium oxide is one such additive. To prevent identification problems with these and other types of
tungsten electrodes, they are color coded. Two types of Thoriated tungsten electrodes are available. The
EWTh-1 and EWTh-2 electrodes contain 1 percent and 2 percent thorium oxide (THO2) called thoria,
respectively, evenly dispersed through their entire lengths. Thoriated tungsten electrodes are superior to
pure tungsten electrodes in several respects. The thoria provides about 20 percent higher current-
carrying capacity, generally longer life, and greater resistance to contamination of the weld. With these
electrodes, arc starting is easier, and the arc is more stable than with pure tungsten or Zirconiated
tungsten electrodes.

The EWTh-1 and EWTh-2 electrodes were designed for DCEN applications. They maintain a sharpened
tip configuration during welding, which is desirable for welding steel. They are not often used with AC
because it is difficult to maintain the balled end, which is necessary with AC welding, without splitting the

Thorium is a very low-level radioactive material. The level of radiation has not been found to represent a
health hazard. However, if welding is to be performed in confined spaces for prolonged periods of time, or
if electrode grinding dust might be ingested, special precautions relative to ventilation should be
considered. The user should consult the appropriate safety personnel.

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