MK Welding Multi-GMAW 200 LCD PFC, User Manual

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§4.3.5 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 nonconsumable 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 colour-coded at the end for easy identification. Below
are the most commonly used tungsten electrodes found in the New Zealand and Australian
market.
Thoriated
Thoriated tungsten electrodes (AWS classification EWTh-2) contain a minimum of 97.30
percent tungsten and 1.70 to 2.20percent thorium and are called 2 percent thoriated. They are
the most commonly used 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 welders can occur when thorium oxide
gets into the lungs. This can happen from the exposure to vapours 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) for its use.
E3 (Color Code: Purple)
E3 tungsten electrodes (AWS classification EWG) contain a minimum of 98% percent tungsten
and up to 1.5 percent Lanthanum and small percentages of Zirconium and Yttrium they are
called E3 Tungsten. E3 Tungsten Electrodes provide conductivity similar to that of thoriated
electrodes. Typically, this means that E3 Tungsten Electrodes are exchangeable with thoriated
electrodes without requiring significant welding process changes. E3 deliver superior arc
starting, electrode lifetime, and overall cost-effectivenes. When E3 Tungsten Electrodes are
compared with 2% thoriated tungsten, E3 requires fewer re-grinds and provides a longer overall
lifetime. Tests have shown that ignition delay with E3 Tungsten Electrodes actually improves
over time, while 2% thoriated tungsten starts to deteriorate after only 25 starts. At equivalent