TIG welding, known for its precision and high-quality results, relies heavily on selecting the appropriate tungsten electrode. As a beginner, navigating through the various options can be overwhelming. In this guide, we aim to simplify the process and provide valuable tips for choosing the right tungsten electrode for your specific welding application.
The Role of Tungsten in TIG Welding:
TIG stands for tungsten inert gas welding process, so it hinges on the use of tungsten electrodes.Tungsten is a rare metallic element with an exceptionally high melting point of any metal. As a result, the electrode is more than capable of withstanding the heat of the welding arc without melting. Understanding the properties and preparations of tungsten electrodes is crucial for achieving optimal results in welding different metals.
Types of TIG Welding Tungsten Electrodes Explained:
1. Pure Tungsten Electrode – Colour Code: Green
Green tungsten electrodes show the best results in AC welding, where they form a clean, balled tip when heated. In addition, they offer a stable arc in balanced wave and sine wave welding, but at the cost of high consumption. However, increased consumption is compensated by their low price.
Besides high consumption, pure tungsten electrodes tend to spit at higher amperage. So even though you could use them for DC welding, they don’t perform well in ensuring smooth arc starts and clean results at higher amperage applications.
Due to known drawbacks of pure tungsten electrodes, manufacturers introduced oxides to improve the arc stability, arc start, and performance. Still, some welders prefer green tungsten in aluminium and magnesium welding due to lower prices.
2. Thoriated Tungsten Electrodes – Colours: Yellow and Red
Thoriated electrodes are one of the most versatile on the market, which makes them one of the most widely used tungsten electrodes today. They contain 97.30% tungsten and 1.70 to 2.20% thorium oxide. Adding thorium oxide to the tungsten reduces the operating temperature below the melting point, which minimises the weld pool contamination and consumption. As a result, thoriated welding electrodes provide excellent results at DC electrode negative welding (straight polarity) on carbon and stainless steel, nickel alloys, and titanium alloys welding performance.
However, thoriated electrodes don’t perform well on AC welding compared to green tungsten electrodes. In addition, the balled end, which is suitable for non-ferrous metal welding, is difficult to maintain.
There are three recognised thoriated electrode types: yellow, red, and purple:
- Yellow code colour
The yellow tungsten contains 0.8–1.2% of thorium oxide dispersed throughout the entire length. Yellow tungsten electrodes maintain a sharpened point well, which makes them an excellent choice for steel, copper alloys, titanium, or nickel alloys.
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Red colour code
The red tungsten contains 1.7–2.2 percent thoria, which increases the operating characteristics. With good arc stability and start, low consumption, and great result on DC welding, red tungsten electrodes are your go-to choice for TIG welding steel.
- Purple colour code
The purple tungsten contains 0.5–0.8% of rare earth oxides, often composed of a mix of cerium and other elements, dispersed evenly along the entire length. The unique properties of purple tungsten electrodes allow them to retain a well-defined point, making them particularly well-suited for welding applications involving materials such as stainless steel, aluminium, and other non-ferrous alloys.
The biggest drawback of thoriated electrodes lies within thorium addition, which is radioactive material. That’s why you should be extra careful when grinding thoriated tungsten electrodes.
3.Ceriated Electrodes – Color Code: Gray
Ceriated electrodes contain 97.30 percent tungsten and 1.80 to 2.20% CeO2, or cerium oxide, also referred to as ceria. Even though there are several grades of ceriated electrodes, only one is commercially significant which carries a grey colour on its tip.
Ceriated electrodes provide excellent results at low amp DC welding. Compared to green tungsten, grey electrodes show exceptionally better arc starts and arc stability and reduced vaporisation rate. Even though they provide similar arc characteristics like thoriated electrodes, ceriated electrodes work better in low-amp situations, which makes them suitable for thin sheet welding, pipe fabricating, and delicate metal joining.
Grey electrodes can be used on alternating current, but they work better with carbon and stainless steel, nickel alloy, and titanium welding, similar to red tungsten. However, ceria is non-radioactive, making them a safer alternative to thoriated electrodes.
Nonetheless, ceriated electrodes show poor results at high amp DC TIG welding. The oxides migrate to the tip of the electrode, where the heat is concentrated, and they disperse. By losing cerium oxide, electrodes lose their positive characteristics.
4. Zirconiated Electrodes – Color Code: White
Zirconiated tungsten electrode contains 99.10% tungsten and 0.15 to .8% zirconium oxide. They carry a white colour on the tip.
Similarly, zirconiated tungsten electrodes are used for AC welding jobs which include TIG welding aluminium alloys and magnesium. The high amount of tungsten produces a highly stable arc and retains a balled tip. Meanwhile, adding zirconium oxide improves the arc start, produces less spit, and handles higher amperage better than pure tungsten electrodes.
White tungsten electrodes are more expensive than green tungsten, but they are crucial in AC sine wave welding applications that require cleanliness. In addition, due to less spit, these produce significantly lower contamination and consumption than pure tungsten electrodes.
Even though zirconiated tungsten has a similar current-carrying capacity to thoriated electrodes, you should not use it in DC welding applications on carbon steel.
5. Lanthanated Tungsten Electrodes – Colours: Black, Gold, Blue
Lanthanated tungsten electrodes contain a minimum of 97.80 percent tungsten and the addition of 0.8-1.7% lanthanum oxide (La2O3), which is also called lanthana. Added lanthanum oxide improves arc starts, stability, and performance on both AC and DC welding. In addition, they maintain a sharp tip for steel welding, as well as a balled tip for aluminium alloys and non-ferrous metals at AC TIG welding.
Due to its favourable characteristics, the lanthanated tungsten electrode is considered a suitable replacement for thoriated tungsten electrode. However, lanthanum oxide is not radioactive, making these electrodes a go-to choice for many welders today.
Lanthanated tungsten electrodes is classified into three separate grades depending on the addition of lanthana:
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Black colour code
These electrodes contain 0.8-1.2 weight-percent lanthanum oxide and carry black colour on the tip. These are similar to a blue tungsten electrode and show DC welding arc starts, stable arc, low erosion rate, wide amperage range, and no spitting.
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Gold colour code
These electrodes are one of the most versatile electrodes today due to their ability to work well during both AC welding jobs and DCEN applications. These contain 1.3–1.7 wt.-% of La2O3, and you can distinguish them by the gold colour on the tip.
- Blue colour code
These electrodes contain 1.8–2.2 wt.-% dispersed lanthanum oxide, which is among the highest amount of oxides in all the specified electrode types. The high addition of oxides allows blue tungsten to resist high pulsing and amperage loads while retaining excellent arc start performance with a low consumption rate.
6. Rare Earth Tungsten Electrodes – Class: EWG (Various Colours)
The rare earth tungsten electrodes contain rare earth oxides that are not specified by an existing classification. These are classified as EWG electrodes, and manufacturers must use any colour other than those standardised (red, blue, gold, brown, etc.) The addition of rare earth oxides improves arc stability, arc start characteristics, and overall welding performance. In addition, added oxides can provide characteristics for specialty AC welding or direct current applications.
Even though rare earth electrodes can contain any oxide, the manufacturers must clearly mark each additive and its percentage on the package. As a result, you can get a specific electrode that perfectly suits your TIG weld applications. However, as a hobbyist, you will rarely need to use them.
Tungsten Preparation Tips:
After selecting the appropriate tungsten electrode, proper preparation is essential. Depending on the welding application, you must choose between a balled, pointed, or truncated tungsten tip.
– AC welding electrodes (pure or zirconiated tungsten) will require a balled tip that works great on sine wave and conventional square wave GTAW machines. To get the balled tip, you won’t need special preparation. Just provide an AC current, and the ball will form on the end of the electrode.
– Conversely, welding stainless steel or steel will require a sharp and/or truncated tip that can be applied on various electrode types (thoriated, lanthanated electrodes, etc.) You will need a specialised tungsten electrode sharpener with a diamond grinder to sharpen the tungsten electrode. As a rule of thumb, you will need to grind the taper to a distance of no more than 2.5 times the electrode diameter.
– Welding thin gauge aluminium or any delicate metal prone to distortion will require a pointed tip. The pointed tip focuses the arc closely and narrows the heat-affected zone. Narrow HAZ is crucial when trying to avoid distortion of delicate metals.
Choosing the Right Tungsten Electrode:
Consider the following recommendations for specific welding applications:
1. Best Tungsten for Steel:
– Thoriated electrodes (red) are versatile for both thick and thin steel, offering stable arcs and outstanding results. While lanthanated electrodes offer a safe alternative.
– Lanthanated electrodes (gold) provide a safe alternative with durability but may perform slightly less on low-amp applications.
– Ceriated electrodes (grey) excel in low-amp DC steel welding, providing stability with thin steel.
2. Best Tungsten for Aluminum:
– Pure tungsten (green) or zirconiated tungsten (white) are common choices for AC TIG welding on aluminium.
– Zirconiated electrodes offer improved arc start, lower consumption, and reduced weld puddle contamination.
Final Thoughts:
Understanding the characteristics of each tungsten electrode type and their applications, along with proper preparation techniques, is crucial for achieving optimal TIG welding results. The colour-coded classification system simplifies the selection process. This allows welders to choose the right tungsten for their specific needs. By following these guidelines, both beginners and experienced welders can navigate the intricacies of TIG tungsten with confidence.
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