Guidelines for Tungsten Electrodes

Tungsten is a rare metallic element used for manufacturing gas tungsten arc welding (GTAW) electrodes. The GTAW 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.

Each Tig Electrodes is color-coded to eliminate confusion over its type. The color appears at the tip of the electrode.

Pure Tungsten (Color Code: Green):

Pure tungsten electrodes contain 99.50 percent tungsten, have the highest consumption rate of all electrodes, and typically are less expensive than their alloyed counterparts.

These electrodes form a clean, balled tip when heated and provide great arc stability for AC welding with a balanced wave. Pure tungsten also provides good arc stability for AC sine wave welding, especially on aluminum and magnesium. It is not typically used for DC welding because it does not provide the strong arc starts associated with thoriated or ceriated electrodes.

Thoriated (Color Code: Red):

Thoriated tungsten electrodes contain a minimum of 97.30 percent tungsten and 1.70 to 2.20 percent 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 increases the electron emission qualities of the electrode, which improves arc starts and allows for a higher current-carrying capacity. This electrode operates far below its melting temperature, which results in a considerably lower rate of consumption and eliminates arc wandering for greater stability. Compared with other electrodes, thoriated electrodes deposit less tungsten into the weld puddle, so they cause less weld contamination.

Ceriated (Color Code: Orange):

Ceriated tungsten electrodes contain a minimum of 97.30 percent tungsten and 1.80 to 2.20 percent cerium and are referred to as 2 percent ceriated. These electrodes perform best in DC welding at low current settings but can be used proficiently in AC processes. With its excellent arc starts at low amperages, ceriated tungsten has become popular in such applications as orbital tube and pipe fabricating, thin sheet metal work, and jobs involving small and delicate parts. Like thorium, it is best used to weld carbon steel, stainless steel, nickel alloys, and titanium, and in some cases it can replace 2 percent thoriated electrodes. Ceriated tungsten has slightly different electrical characteristics than thorium, but most welders can't tell the difference.

Lanthanated (Color Code: Gold):

Lanthanated tungsten electrodes contain a minimum of 97.80 percent tungsten and 1.30 percent to 1.70 percent lanthanum, or lanthana, and are known as 1.5 percent lanthanated. These electrodes have excellent arc starting, a low

Unlike thoriated tungsten, these electrodes are suitable for AC welding and, like ceriated electrodes, allow the arc to be started and maintained at lower voltages. Compared with pure tungsten, the addition of 1.5 percent lanthana increases the maximum current-carrying capacity by approximately 50 percent for a given electrode size.

Zirconiated (Color Code: Brown):

Zirconiated tungsten electrodes contain a minimum of 99.10 percent tungsten and 0.15 to 0.40 percent zirconium. A zirconiated tungsten electrode produces an extremely stable arc and resists tungsten spitting. It is ideal for AC welding because it retains a balled tip and has a high resistance to contamination. Its current-carrying capability is equal to or greater than that of thoriated tungsten. Under no circumstances is zirconiated recommended for DC welding.

Rare Earth (Color Code: Gray):

Rare-earth tungsten electrodes contain unspecified additives of rare-earth oxides or hybrid combinations of different oxides, but manufacturers are required to identify each additive and its percentage on the package. Dependsing on the additives, desired results can include a stable arc in both AC and DC processes, greater longevity than thoriated tungsten, the ability to use a smaller-diameter electrode for the same job, use of a higher current for a similar-sized electrode, and less tungsten spitting.

Ref:thefabricator.com/article/arcwelding/guidelines-for-tungsten-electrodes