BLOG: Choosing the Right Tungsten Electrode
Tungsten is a rare metal element that is used in the manufacture of electrodes that are used in tungsten arc welding (GTAW – Gas Tungsten Arc Welding). In the continuation, instead of GTAW, a term with which we are more familiar will be used, TIG welding or welding according to the TIG process.
The TIG process is characterized both by the resistance at higher temperatures, which are important for the transfer of the welding current into the weld seam and by the hardness of the tungsten. At 3,410 degrees Celsius, tungsten has the highest melting point of all metals.
Tungsten electrodes are available in different lengths, colors, and diameters and are made of pure tungsten or an alloy of tungsten and other rare earth elements and their oxides such as cerium and lanthanum, the most common types of electrodes. The choice of electrode for the TIG process depends on the type and thickness of the base material as well as the type of welding current, alternating current (AC), or direct current (DC).
The way the tip is processed is also particularly important; it can either be ground to a round point or to a point of intersection. The method and the grinding process can, depending on the workpiece material, have a strong influence on the welding result or the weld seam.
Each type of tungsten electrode is clearly color-coded. The end of the electrode is colored and each color represents a type of electrode.
| Â Type of tungsten electrode | Â Colour | Â Label | Oxide addition % Â | Â Alternating current AC | Â Direct current DC | Â Areas of application |
|---|---|---|---|---|---|---|
| Â Wla - tungsten with lanthanum oxide | Â Black | Â WL-10 | Â 1,0% Lanthanum LaO2 | Â x | Â x | Â Universal electrode for AC & DC welding. First choice in the low current range, with very good and high ignitability! |
| Â | Â Gold | Â WL-15 | Â 1,5% Lanthanum LaO2 | Â x | Â x | Â These can be used to weld unalloyed and high-alloy steels, titanium, nickel, copper, aluminum and magnesium alloys |
| Â | Â Blue | Â WL-20 | Â 2,0% Lanthanum LaO2 | Â x | Â x | Â |
| Â WCe - tungsten with ceria | Â Grey | Â WC-20 | Â 2,0% Cer LaO2 | Â x | Â x | Â Universal electrode for AC & DC welding. These can be used to weld steels, aluminum, nickel, titanium, copper and magnesium alloys in the lower and middle current range. |
| Â WTh - tungsten with thorium oxide ThO2 * aktive Partikel | Â Yellow | Â WT-10 | Â 1,0% Thorium ThO2 | Â x | Â x | Â Because of the radioactive particles, we advise against using it! Good alternatives are e.g. (WL / WC) with even better properties. |
| Â | Â Red | Â WT-20 | Â 2,0% Thorium ThO2 | Â x | Â x | Â But if they are used, they can be used to weld high-alloy materials. Safety precautions are to be observed! |
| Â | Â Purple | Â WT-30 | Â 3,0% Thorium ThO2 | Â x | Â x | Â |
| Â | Â Orange | Â WT-40 | Â 4,0% Thorium ThO2 | Â x | Â x | Â |
| Â WZr - tungsten with zirconium oxide ZrO2 | Â Brown | Â WT-03 | Â 0,3% Zirconium ZrO2 | Â x | Â | Â Suitable for AC welding of aluminum alloys, only conditionally suitable for DC welding. |
| Â | Â White | Â WT-08 | Â 0,8% Zirconium ZrO2 | Â x | Â | Â |
| Â WP - undoped tungsten electrode | Â Green | Â WP-00 | Â 99,8% Tungsten | Â x | Â | Â Suitable for AC welding of aluminum alloys, unsuitable for DC welding. |
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The following colors of tungsten electrodes are most commonly used:
- Green – pure tungsten
- Red
- Gold
- Gray
- Orange
- Blue
Some types of tungsten electrodes are also available in our online shop, take a look at the range: https://ipotools.eu/product-category/welding-and-cut-accessories/filler-metals/
In this blog, we’re going to dig deeper into the most commonly used tungsten electrodes.
Pure tungsten (green)
Pure tungsten electrodes (WP-00) contain 99.50% tungsten, have the highest wear rate of any electrode and are usually cheaper than their alloys.
These electrodes form a clean, round tip when heated and offer excellent arc stability for alternating current (AC) welding. Pure tungsten also ensures good arc stability during AC welding with sinusoidal current waves, especially when welding aluminum, magnesium, and their alloys. Normally, however, these electrodes are not used for direct current welding (DC), as they do not produce a strong arc, unlike tungsten electrodes with, for example, the color red.
Tungsten electrode (red)
Thorium tungsten electrodes (designation WT-20) contain at least 97.30 tungsten and 1.70 to 2.20 percent thorium and are referred to like 2 percent thorium. Nowadays, these are the most commonly used electrodes due to their long life and ease of use.
Thorium increases the electron emission properties of the electrode, which improves the start of the arc and enables higher welding performance. This electrode is used well below the melting temperature, which leads to significantly less wear. Compared to other electrodes, the thorium tungsten electrodes transfer less tungsten into the weld puddle and therefore cause less welding contamination.
These electrodes are mainly used in special alternating current welding (such as thin aluminum sheets and materials less than 1.5 mm thick) and in direct current welding of carbon and stainless steels as well as nickel and titanium.
In making these electrodes, thorium is evenly mixed with tungsten, which helps tungsten maintain a sharp edge after grinding – the ideal electrode shape for welding thin steel.
Note: Thorium is slightly radioactive, so always follow the manufacturer’s warnings, instructions, and safety data sheets when using it.
Tungsten electrode (Gold)
Lanthanum tungsten electrodes (WL-15) contain at least 97.80% tungsten and 1.30% to 1.70% lanthanum and are referred to as 1.5% lanthanum electrodes. They are characterized by excellent arc ignition, reduced wear, very good arc stability, and excellent re-ignition properties – in many ways similar to cerium-tungsten electrodes.
Lanthanum electrodes also share the electrical conductivity properties of 2% tungsten thorium. In some cases, 1.5% lanthanum electrodes can completely replace a 2% thorium electrode without significantly changing the welding parameters.
Lanthanum tungsten electrodes are ideal for optimizing your welding performance. Those are ideal for AC or DC negative electrodes with a pointed end, which you can also use for AC welding. When welding with lanthanum tungsten, the shape of a sharp point is obtained, which is a great advantage when welding steel and stainless steel with direct current or alternating current with rectangular current waves.
In contrast to tungsten-thorium, these electrodes are also suitable for alternating current welding (AC) and, like cerium-tungsten electrodes, enable the arc to start and be maintained even at lower voltages. Compared to pure tungsten with 1.5% lanthanum, the maximum electrical conductivity for a given electrode size is increased by approx. 50%.
Tungsten electrode (Gray)
Gray tungsten electrodes (designation WC-20) contain unspecified additives of rare metal oxides or hybrid combinations of different oxides. However, manufacturers must indicate each additive and its percentage on the packaging. Depending on the additives, the desired results can include a stable arc in AC and DC processes, a longer life than tungsten thorium, the ability to use a smaller diameter electrode for the same work, the use of a higher current for electrodes of identical size, and a lower one Include tungsten deposition on the workpiece.
Tungsten electrode (Orange)
A cerium-tungsten electrode (designation WT-40) contains at least 97.70 tungsten and 1.80 to 2.20 percent cerium. These electrodes are best suited for DC welding at low current settings, although those are also applicable to AC welding processes. With its excellent arc quality at low amperage, cerium-tungsten is particularly popular for welding and orbital welding of tubes, thin sheet metal, and for work involving small and sensitive parts.
Like thorium, cerium-tungsten is best for welding carbon steel, stainless steel, nickel alloys, and titanium, and can also replace a 2% thorium electrode in some cases. The electrical properties of cerium-tungsten are somewhat different from those of thorium, but most welders cannot distinguish between them.
The use of larger electrodes at higher strengths is not recommended, as at higher current strengths the oxides are quickly transferred to the heat of the tip, which removes the oxide content and also degrades the welding benefits.
Choice of the thickness/diameter of the tungsten electrode
The following table shows the recommended values ​​of the welding currents for a specific diameter of the tungsten electrode. As a rule, a thinner electrode ensures better ignition of the welding arc than a thicker one, but at the same time the thinner electrode wears out more quickly. If we choose an electrode that is too thick for a given welding current, this can lead to an unstable arc during welding, which of course affects the quality and shape of the weld.
| Â | Direct current (A) Â | Â | Alternating current (A) Â |
|---|---|---|---|
| Â Diameter of the tungsten electrode | Â Electrode polarity - | Â Electrode polarity + | Â 50/50 AC Balance |
| Â 0,3 | Â 0,1 to 15 | Â / | Â 0,1 to 15 |
| Â 0,5 | Â 5-20 | Â / | Â 5-20 |
| Â 1,0 | Â 15-80 | Â / | Â 20-60 |
| Â 1,6 | Â 70-150 | Â 10-20 | Â 60-120 |
| Â 2,4 | Â 150-250 | Â 15-30 | Â 100-180 |
| Â 3,2 | Â 250-400 | Â 25-40 | Â 160-250 |
| Â 4,0 | Â 400-500 | Â 40-55 | Â 200-320 |
| Â 4,8 | Â 500-750 | Â 55-80 | Â 290-390 |
| Â 6,4 | Â 750-1000 | Â 80-125 | Â 240-525 |
Table 1 – Typical welding current ranges for different tungsten electrode diameters in TIG welding.
Preparation – grinding the tungsten electrodes – tip, round, or cut tip?
After you have decided on an electrode type, the next step is the choice of the grinding method. The three most common methods of grinding the tungsten electrodes are point, round point, or cut point.
A round tip is normally used for pure tungsten electrodes labeled green and is recommended for alternating current (AC) welding with sinusoidal current waves and for conventional TIG welding machines with rectangular current waves. To properly shape the tip of the tungsten electrode, simply use the recommended alternating current for a given electrode diameter (Table 1) and a round tip will form at the end of the electrode. The diameter of the rounding formed should not exceed 1.5 times the diameter of the electrode (e.g. the electrode with a diameter of 1.6 mm must not have a round tip with a diameter of approx. 2 to 2.5 mm exceed). A larger ball at the tip of the electrode can reduce the stability of the arc. In addition, the round tip can fall off and contaminate the weld seam.
Preparation – grinding the tungsten electrodes
In TIG welding with inverter welding devices with direct or alternating welding current, the tungsten electrodes are ground to a point or a sharpened point. To avoid contamination of the electrodes, we recommend using special grinding wheels for grinding tungsten. Diamond cutters are best for this.
When grinding the thorium-tungsten electrodes, make sure that they are suctioned off and ventilated, as the dust produced during grinding is poisonous and harmful to health. Follow the manufacturer’s warnings, instructions, and safety data sheets.
The electrode is ground parallel to the grinding wheel so that the grinding marks run lengthways to the electrode, which ensures a stable arc and reduces the possibility of welding contamination.
We also recommend that you grind the tungsten electrode as centrically as possible, because the more centrically it is ground, the more stable the arc is, on which the arc quality also depends.
The cone at the end of the electrode should not be larger than 2.5 times the electrode diameter. For example, with a 1.6 mm electrode, the cone should be about 4 mm long. Electrode ground in this way guarantees better ignition and more precision in the arc.
If you are welding a thin material with a very low current (from 0.1 to 1.00 mm) it is best that the electrode is ground to a point. In this case, the point-ground tungsten electrode ensures the maximum concentration of the arc and thus prevents excessive heat transfer to the weld seam. In practice, this means less bending of the workpiece.
It is not recommended that you use a pointed tungsten electrode with higher welding currents, as increased welding current can cause the tip of the electrode to fall off and contaminate the weld. When welding at higher currents, it is best that the electrode tip is smoothed and ground. So, sharpen the electrode as described above, then lightly sand the top of the tip. The flat surface at the end of the electrode prevents tungsten from being transferred across the arc and prevents the formation of a ball.
Of course, there are also special electrode grinders for grinding tungsten electrodes, but due to the high prices and their unavailability, these are only mentioned here. If you follow instructions for choosing and preparing the tungsten electrodes, you can get great results even without special machinery and equipment.
Conclusion
How the arc and the binding behave depends on the bevel angle. An acute angle causes the penetration to be deeper, while an obtuse angle causes the penetration to be shallower with the same welding current. However, in order to achieve a good welding result and to reduce the load on the tip, the guideline value is that the tip of the electrode can be blunted by approx. 10% of the electrode diameter after grinding (2.4mm = approx. 0.24mm blunt). For the length, the diameter of the electrode is approx. Times 1 – 1.5. So the length of a 1.6 mm electrode is 1.6 – 2.4 mm.
