[TIG] - Choosing tungsten electrodes

The choice of tungsten electrodes for TIG welding often gives rise to passionate debate, with everyone having their own personal preferences, resulting from dogmatism or field experience. We are therefore going to attempt to explore this subject, based on various tests carried out on the web and on manufacturers' documentation. However, we do not claim to represent the absolute truth: each selection is dictated by compromises, as we shall see later.

For those of you who don't want to get unnecessarily technical, you'll find a simplified decision tree below to help you make a reasoned choice depending on the metal you're going to weld:

As this diagram shows, the type of current used for your welding work (AC for alternating current and DC for direct current) will guide your selection from the outset:

-AC welding only:

-The pure tungsten electrode (known as WP) is of no interest for a recent substation whose power electronics are based on an inverter rather than a transformer. It is therefore inevitably reserved for older models and is not recommended for use in new substations, as its lack of stability at high frequency and high amperage could lead to contamination of the molten metal bath.

-The Zirconium-enriched electrode (identifier WZ8) is ideal for use in alternating current (inverter- or transformer-based power source) with aluminum and magnesium alloys. Its strong points are good ball-holding at the tip, support for higher amperage than pure tungsten, and less sparking. On the other hand, it also offers better priming and superior arc stability. Although its current-carrying capacity equals or even exceeds that of thorium tungsten, the zirconia electrode is not recommended for DC welding applications.

-AC + DC welding:

There are a plethora of multi-purpose electrodes in these 2 voltage ranges, but only 2 really stand out from the crowd. It's worth noting that they are non-radioactive, and therefore replace Thorium-based electrodes. We'll take a brief look at the others at the end of this article, so as not to leave them out completely.

-Let's start with WL20 enriched with 1.8-2% Lanthanum (as opposed to WL15, which oscillates between 1.3-1.7%): it is renowned for its superior arc initiation at minimum amperages, good arc stability, low wear rate and reliable re-ignition capabilities. In industry, lanthanum tungsten is recognized as a versatile substitute for thoriated and ceriated electrodes, as it combines the best qualities of both. It also supports a medium to high amperage range.

This electrode offers a wide range of applications and combines some of the best characteristics seen in other tungsten variants.

Next comes the new generation of electrodes known as tri-mix, featuring a blend of three rare-earth oxides (a family found under the EWG classification). This optimizes migration and evaporation rates, thus extending tungsten life. This variant offers stability and uniformity unmatched by many other types of tungsten.

It achieves very good starting at low amperage, and as its ignition properties are excellent, it is also often used for automated processes.

During the welding process, the electrode temperature remains constantly low (lower than that of a 2% thoriated alloy), which improves its current-carrying capacity and consequently its longer life than thoriated electrodes.

It can be found under the E3 reference at Abicor Binzel and under the LaYZr name at CK (the color is called “chartreuse” at CK). 

Below is a summary of the ratings awarded by various parties (website, retailer or manufacturer):

Note that the maximum rating at Soudeurs.com was +++ and that they also made a comparison with rare-earth electrodes, but without specifying which were concerned, so I didn't include it for E3/LaYZr.

Abicor Binzel also recommends sharpening this model at 60° so that they degrade less rapidly in AC, especially at high amperage.

- Other versions available on the market:

- Tungsten Thorium (WT20): Despite its interesting properties, the fact that it is slightly radioactive has led to its gradual abandonment, especially as replacements are now able to do better.

- Tungsten Lanthanum (WL15 , which oscillates between 1.3-1.7%): This is a declination that's of absolutely no interest in the sense that the WL20 does better than it in every respect.

-Tungsten Cerium (WC20): gives the best results in low-intensity DC welding. It has excellent arc initiation at low current, making it essential for orbital tube and pipe fabrication, sheet metal work and small parts applications. Ceriated electrodes offer similar versatility to thoriated electrodes, and often replace them in low-amperage applications. It is this low-amperage limitation in particular that makes them less versatile than WL20 or E3/LaYZr.

--Tungsten GEN3  (pearly copper) with 3% rare earths: A new addition to the EWG family with 1% more rare earths than E3/LaYZr. They are sold by EWS and are said to offer arc stability and service life a notch above E3/LaYZr.

-Tungsten Lymox (1% Lanthanum + 1% Cerium) & LymoxLux (1% Lanthanum + 4% Cerium):  Manufactured by Litty, they have a fairly confidential distribution and it's difficult to get more information on their performance. We are promised excellent priming and (very) low wear. However, given that they're cerium-based, one might logically deduce that their strong point is unlikely to be high amperage.

If you are interested in some video comparisons, here is a small selection: 

-Comparatif Thorium/E3 par Abicor

-The Fabrication Series

-WeldingTipandTricks: comparatif 1 & 2

-Weld.com

Sources used for this article:

-Abicor-Binzel

-EWS Gmbh

-Soudeurs.com

-Weldguru

-The Welder