OPERATION
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§4.2.4 Tungsten Electrodes
Tungsten is a rare metallic element used for manufacturing TIG welding electrodes. The
TIG process relies on tungsten’s hardness and high-temperature resistance to carry the
welding current to the arc. Tungsten has the highest melting point of any metal, 3,410
degrees Celsius. Tungsten electrodes are a consumable and come in a variety of sizes,
they are made from pure tungsten or an alloy of tungsten and other rare earth elements.
Choosing the correct tungsten depends on the material being welded, amps required and
whether you are using AC or DC welding current. Tungsten electrodes are color-coded at
the end for easy identification.
Thoriated (RED)
Thoriated tungsten electrodes (AWS classification EWTh-2) contain a minimum of 97.30
percent tungsten and 1.70 to 2.20 percent thorium and are called 2% thoriated. They are
the most commonly used DC electrodes today and are preferred for their longevity and
ease of use. Thorium however is a low-level radioactive hazard and many users have
switched to other alternatives. Regarding the radioactivity, thorium is an alpha emitter but
when it is enclosed in a tungsten matrix the risks are negligible. Thoriated tungsten
should not get in contact with open cuts or wounds. The more significant danger to welder
can occur when thorium oxide gets into the lungs. This can happen from the exposure to
vapors during welding or from ingestion of material/dust in the grinding of the tungsten.
Follow the manufacturer’s warnings, instructions, and the Material Safety Data Sheet
(MSDS).
Pure (Green)
Pure tungsten electrodes (AWS classification EWP/WP) contain a minimum of 99.5%
percent tungsten. Pure Tungsten Electrodes provide conductivity similar to zirconiated
electrodes. Pure Tungsten Electrodes work well on AC constant current power sources,
such as transformer, for aluminum and magnesium alloys in low to medium temperature
applications. They can be used DC electrode negative with a pointed end, or balled for
use with AC power sources, they tend to split at higher amperages and should be used
for non-critical welds only.
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