TIG welding is one of the most challenging welding processes that require a lot of practice, but it yields the highest quality and aesthetic welds. In the line of challenges you need to overcome to get the best result stands the proper tungsten selection.
TIG welding is one of the most challenging welding processes that require a lot of practice, but it yields the highest quality and aesthetic welds. In the line of challenges you need to overcome to get the best result stands the proper tungsten selection.
As a beginner, you might have heard fellow welders talk about red or gold tungsten electrodes, debating which one is better or suits steel or aluminum alloys. That's why we decided to help you understand tungsten electrode types and give you tips when choosing the right one for your application.
TIG stands for tungsten inert gas welding process, so as you can deduce, this process highly relies on tungsten electrodes. Tungsten is a rare metallic element with the highest melting point of any metal. As a result, the electrode is more than capable of withstanding the heat of the welding arc without melting.
Tungsten electrodes come in a wide variety of sizes, lengths, and compositions. Therefore, on the market, you can find TIG electrodes with electrode diameter ranging from 0.040"-3/32", composed of pure tungsten or with added oxides, 7" in length or shorter.
Each of these properties can affect welding results, so many beginners wonder where to start. Since choosing the right TIG welding tungsten is essential for the best welding results on different types of metals, we will help you understand their properties and preparation.
The American Welding Society published "Specification for Tungsten and Oxide Dispersed Tungsten Electrodes for Arc Welding and Cutting" to ensure each welder gets tungsten electrodes with a specific composition.
The AWS A5.12M/A5.12:2009 document also provides a table that identifies the color-coding used in the United States, Europe, and Japan, which is the majority of the market share of sold tungsten. Due to easier distinguishing, many welders today call TIG electrodes by color rather than their original name.
Source: https://www.techstreet.com/standards/aws-a5-12m-a5-12-2009?product_id=1620788
So let's see what the common types of tungsten electrodes are and what their characteristics are.
Pure tungsten electrodes contain 99.50% tungsten, and they are denoted as EWP in the AWS classification. Pure tungsten is one of the oldest electrode choices and was closely related to the discovery of Gas tungsten arc welding. TIG welding was initially developed for aluminum and magnesium welding, and these electrodes are used in the same applications even today.
Source: http://www.halversoncts.com/76-tungsten-electrodes.html
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 aluminum and magnesium welding due to lower prices.
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. Good DC welding arc starts and stability with longevity and medium erosion rate are why many older welders swear by thoriated electrodes.
Adding thorium oxide to the tungsten reduces the operating temperature below the melting point, which minimizes 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.
Source: https://weldguru.com/ac-vs-dc-welding/
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.
AWS recognizes three thoriated electrode types: yellow, red, and purple, but only two of them are commercially significant:
has a
yellow code color, and it 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.
have a
red color code, and they contain 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.
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. Safety concerns are one of the main reasons why many welders turn to alternatives such as lanthanated or ceriated tungsten electrodes.
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 - EWCe-2, which carries a gray color on its tip.
EWCe-2 ceriated electrodes provide excellent results at low amp DC welding. Compared to green tungsten, gray electrodes show exceptionally better arc starts and arc stability and reduced vaporization 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 not radioactive as thorium, which presents an advantage.
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.
Zirconiated tungsten electrode contains 99.10% tungsten and 0.15 to .40% zirconium oxide. They carry a brown color on the tip, and AWS classifies them as EWZr-1. Brown TIG welding electrodes were developed as an alternative to pure tungsten, which you can see from the high tungsten content.
Similarly, zirconiated tungsten electrodes are used for AC welding jobs which include TIG welding aluminum 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.
TIG welding with
zirconiated tungsten electrode
Brown 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.
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 aluminum alloys and non-ferrous metals at AC TIG welding.
Due to its favorable 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.
The AWS classifies lanthanated tungsten electrodes into three separate grades depending on the addition of lanthana:
electrodes contain 0.8-1.2 weight-percent lanthanum oxide and carry
black coloron 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.
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 La
2
O
3
, and you can distinguish them by the
gold coloron the tip.
WL15 Series 1.5% Lanthanated TIG WeldingTungsten Electrode
EWLa-2 electrodes
contain 1.8–2.2 wt.-% dispersed lanthanum oxide, which is among the highest amount of oxides in all AWS-specified electrode types. The high addition of oxides allows
blue tungstento resist high pulsing and amperage loads while retaining excellent arc start performance with a low consumption rate.
WL20 Series 2% Lanthanated TIG WeldingTungsten Electrode
The rare earth tungsten electrodes contain rare earth oxides that are not specified by an existing classification. The AWS classifies them as EWG electrodes, and manufacturers must use any color other than those standardized (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.
After choosing the correct tungsten electrode for your application, you must prepare its tip according to requirements. Typical preparations include balled, pointed, and truncated tungsten tips.
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 specialized tungsten electrode sharpener with a diamond grinder to sharpen the tungsten electrode.
TTG02 Tungsten Electrode Sharpener Grinder
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. This is because grinding the taper produces a more focused arc, increasing the overall penetration and stability. However, be careful when grinding thoriated tungsten electrodes due to already-known health risks.
Welding thin gauge aluminum 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.
By understanding the characteristics of each electrode type and tungsten preparation, you can already make some deduction on which is the suitable tungsten for steel, stainless steel, or aluminum alloys.
Nonetheless, this last section of our article will serve as an excellent summary of everything we learned today.
To TIG weld carbon steel, you can use a wide variety of TIG electrodes, and the right choice will vary on the process amperage.
Seasoned welders will tell you that the most versatile choice for steel welding is thoriated electrodes (red electrode tip.) The sole reason is the ability to work well with both thick and thin steel, AC/DC applications, extremely stable arc, outstanding arc start characteristics, and final weld puddle results.
However, due to the health hazards of thorium, many welders today started using lanthanated electrodes. Gold tip tungsten presents an alternative and another excellent all-around choice for steel. It doesn't cause health issues, and it is durable, but it tends to work somewhat worse on low-amp applications. Meanwhile, blue tungsten works great on high-amp DC steel welding.
DC welding steel at low current will require ceriated tungsten electrodes. Gray tungsten produces a more stable arc with thin steel, which is considered an alternative to red or gold tungsten.
While TIG welding stainless steel is fundamentally different and more challenging than joining mild steel, tungsten electrode selection remains the same. You can successfully TIG weld stainless steel with thoriated, lanthanated, or ceriated electrodes.
Once again, red tungsten is a versatile all-around choice for stainless steel, but you can use lanthanated electrodes as an alternative due to safety concerns. Ceriated tungsten will work better than gold tungsten on low-amp stainless steel applications.
Photo by @weldinginoxita
TIG welding aluminum requires an alternating current, so you will need a tungsten electrode that works great with it. Pure tungsten (green) or zirconiated tungsten (brown) electrodes are typical choices.
Many welders choose green tungsten for aluminum due to its low price and decent arc performance when welding magnesium, aluminum, or other non-ferrous metals. However, pure tungsten has the highest consumption rate of any tungsten type and tends to spit at higher amp applications.
When cleanliness is crucial, AC TIG welding will require zirconiated tungsten. Even though it is more expansive than green tungsten, brown electrodes show better arc start, lower consumption, and weld puddle contamination.
Photo by @pacificarctigwelding
Red, blue, gold, or green tungsten might sound confusing to you as a beginner, but understanding how they affect weld arc performance is crucial in ensuring the best results. Luckily, the AWS classification allows you to distinguish each type of tungsten by its color and know its composition.
By understanding the properties of each TIG electrode type, choosing the right one for your application should be a piece of cake. Hopefully, our article helped you understand a small part of the complicated puzzle called TIG welding.
👋You may be interested in: How To Shape Tungsten Electrode For TIG Welding And Why?
Tungsten electrodes may be used with a variety of tip geometries. In AC welding, pure or Zirconiated tungsten electrodes are usually used and are melted to form a balled end. This section of the guidebook is dedicated to grinding electrodes for DC welding. The complete geometry for DC welding is comprised of the electrode diameter, the included angle (a.k.a. taper) and the tip (flat) diameter. In addition, the surface finish of the grind is also important.
Figure 2: Electrode Geometry
Choosing the best electrode geometry requires compromise among various attributes such as: shorter to longer electrode life, easier to more difficult arc starting, deeper to shallower weld penetration, and wider to narrower arc shape (and thus bead shape and size as well). Whichever geometry is selected, it should be used consistently as part of a successful welding procedure.
For best results, electrode configuration should be tested while welding procedures are being developed; it should be noted as a critical process variable for the weld procedure; and close tolerances should be held for all subsequent welds.
Electrode Diameter: The welding equipment manufacturer’s recommendations are almost always the best way to choose which diameter electrode to use. There are also guidelines published by the American Welding Society, which are duplicated in Table 2 of this guidebook. Note that larger diameters can accommodate higher amperages; and larger diameter electrodes will last longer than smaller ones, but smaller ones will be easier to arc start. Use of higher current levels than those that are recommended for a given electrode size will cause the tungsten to deteriorate or breakdown more rapidly. As the tip erodes, the probability of tungsten particles falling into the weld pool and contaminating the weld is much greater. If the current used is too low for a specific electrode diameter, arc instability can occur.
For a given level of current, direct current with the electrode positive requires a much larger diameter, because the tip is not cooled by the evaporation of electrons but heated by their impact; and thus it will become hot and subject to erosion. In fact, an electrode used with DCEP can handle approximately only 10% of the current that it could with the electrode negative. With AC welding, the tip is cooled during the electrode negative cycle and heated when positive. Thus, an electrode on AC can handle the current somewhere between the capacity of an electrode on DCEN and DCEP and about 50% less than that of DCEN.
Electrode Tip/Flat: The shape of the tungsten electrode tip is an important process variable in precision arc welding. A good selection of tip/flat size will balance the need for several advantages. The bigger the flat, the more likely arc wander will occur and the more difficult it will be to arc start. However, increasing the flat to the maximum level that still allows arc start and eliminates arc wander will improve the weld penetration and increase the electrode life. Some welders still grind electrodes to a sharp point, which makes arc starting easier. However, they risk decreased welding performance from melting at the tip and the possibility of the point falling off in the weld pool. In situations where very low amperage is used or short weld cycles are used (i.e., one second or less), a pointed electrode is desirable; however, for other situations it would be beneficial to prepare a flat at the end of the electrode.
Guidelines for testing can be found in Table 6; also refer to the welding equipment manufacturer’s recommendations. During the welding operation, the accurately ground tip of a tungsten electrode is at a temperature in excess of 3000° C (5500° F). Incorrect or inconsistent diameter flat at the tip of the tungsten electrode can lead to the following problems:
In AC welding, pure or Zirconiated tungsten electrodes melt to form a hemispherical balled end. For DC welding, Thoriated, Ceriated, or Lanthanated tungsten electrodes are usually used. For the latter, the end is typically ground to a specific included angle, often with a truncated end. Various electrode tip geometries affect the weld bead shape and size. In general, as the included angle increases, the weld penetration increases and the width of the weld bead decreases. Although small diameter electrodes may be used with a square end preparation for DCEN (Direct Current Electrode Negative) welding, conical tips provide improved welding performance.
Table 6: Tip Recommendations by Electrode Diameter Size
Electrode Included Angle/Taper: Electrodes for DC welding should be ground longitudinally and concentrically with diamond wheels to a specific included angle in conjunction with the tip/flat preparation. Different angles produce different arc shapes and offer different weld penetration capabilities. In general, blunter electrodes that have a larger included angle provide the following benefits:
Sharper electrodes with smaller included angle provide:
Larger tungsten diameters and higher currents are normally paired with larger tapers in the 25° to 45° included angle range in order to increase electrode service life and provide a more stable arc. More pointed tips in the 10° to 25° included angle range are used for lower current.
Electrode Angle Surface Finish: The smoothness of the finish on the prepared tip of the electrode will determine some of the characteristics of the welding process. In general, points should be ground as fine as possible to improve welding properties and increase the service life of the electrode. Electrodes that are ground too coarse result in unstable arcs.
Surface finish is typically expressed as a Root Mean Square (RMS) or as a Roughness Average (Ra). RMS is a comparative number as related to surface finishes measured with a profilometer. A fine finish is in the range of 20-40 RMS, a machined finish often is in the range of 80-120RMS, and grit blasted surfaces will be in the range of 400-500 RMS. The Ra value is defined as the average value of the departures from its centerline through a prescribed sampling length. Measured values expressed as RMS will read approximately eleven percent higher than values expressed in Ra. (Microinches x 1.11 = RMS).
A standard finish of around 20 RMS, which would still show the longitudinally ground lines to the naked eye, is an all-purpose, quality finish for any application. A high-polished or mirror-like finish of approximately 6-8 RMS, where few or no lines can be seen, is better for the longevity of the electrode because without any grit to the electrode surface, it is much less likely for contamination to “stick” to the electrode point and thus less erosion takes place. However, for welding power supplies that do not have strong arc starting characteristics, a finish of approximately 20 RMS is better because the longitudinally ground lines will help steadily lead the electrons to the extreme point of the electrode which assists in arc starting. Some manufacturers of pre-ground welding electrodes provide coarser finishes in the 30 to 40 RMS ranges; however, these do not last long, they provide unstable arcs, and they tend to be too gritty for extended, effective arc starting.
Typical Manufacturers’ Recommended Geometries: Many manufacturers provide information on recommended electrode geometries, because they have already preformed testing to determine which electrode geometry is the most beneficial for their equipment in various applications. However, when this information is not available, Diamond Ground Products, Inc. or other industry experts are the best source for this information.
Tolerances Required for Different Applications: Many welding applications are deemed highly critical and require strict tolerances on the length, taper, and flat, in addition to a high-polished finish. These applications include orbital tube welding for high purity, pharmaceutical, aerospace applications, fitting manufacturing, and many others. Basic guidelines for tolerances in these applications are ± .002” for the length, ±½° for the taper, and ± .002” for the tip/flat. Where applications require electrodes to be manufactured to these extreme tolerances, it is necessary to use equipment such as an optical comparator, microscope, and micrometer in addition to the precision tungsten electrode grinder which is required for almost all applications. Other applications will often call for their own specific tolerances. Where not specified, keep reasonable tolerances for the type of work being performed and remain as consistent as possible.
As a beginner, you might have heard fellow welders talk about red or gold tungsten electrodes, debating which one is better or suits steel or aluminum alloys. That's why we decided to help you understand tungsten electrode types and give you tips when choosing the right one for your application.
TIG stands for tungsten inert gas welding process, so as you can deduce, this process highly relies on tungsten electrodes. Tungsten is a rare metallic element with the highest melting point of any metal. As a result, the electrode is more than capable of withstanding the heat of the welding arc without melting.
Tungsten electrodes come in a wide variety of sizes, lengths, and compositions. Therefore, on the market, you can find TIG electrodes with electrode diameter ranging from 0.040"-3/32", composed of pure tungsten or with added oxides, 7" in length or shorter.
Each of these properties can affect welding results, so many beginners wonder where to start. Since choosing the right TIG welding tungsten is essential for the best welding results on different types of metals, we will help you understand their properties and preparation.
The American Welding Society published "Specification for Tungsten and Oxide Dispersed Tungsten Electrodes for Arc Welding and Cutting" to ensure each welder gets tungsten electrodes with a specific composition.
The AWS A5.12M/A5.12:2009 document also provides a table that identifies the color-coding used in the United States, Europe, and Japan, which is the majority of the market share of sold tungsten. Due to easier distinguishing, many welders today call TIG electrodes by color rather than their original name.
Source: https://www.techstreet.com/standards/aws-a5-12m-a5-12-2009?product_id=1620788
So let's see what the common types of tungsten electrodes are and what their characteristics are.
Pure tungsten electrodes contain 99.50% tungsten, and they are denoted as EWP in the AWS classification. Pure tungsten is one of the oldest electrode choices and was closely related to the discovery of Gas tungsten arc welding. TIG welding was initially developed for aluminum and magnesium welding, and these electrodes are used in the same applications even today.
Source: http://www.halversoncts.com/76-tungsten-electrodes.html
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 aluminum and magnesium welding due to lower prices.
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. Good DC welding arc starts and stability with longevity and medium erosion rate are why many older welders swear by thoriated electrodes.
Adding thorium oxide to the tungsten reduces the operating temperature below the melting point, which minimizes 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.
Source: https://weldguru.com/ac-vs-dc-welding/
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.
AWS recognizes three thoriated electrode types: yellow, red, and purple, but only two of them are commercially significant:
has a
yellow code color, and it 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.
have a
red color code, and they contain 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.
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. Safety concerns are one of the main reasons why many welders turn to alternatives such as lanthanated or ceriated tungsten electrodes.
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 - EWCe-2, which carries a gray color on its tip.
EWCe-2 ceriated electrodes provide excellent results at low amp DC welding. Compared to green tungsten, gray electrodes show exceptionally better arc starts and arc stability and reduced vaporization 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 not radioactive as thorium, which presents an advantage.
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.
Zirconiated tungsten electrode contains 99.10% tungsten and 0.15 to .40% zirconium oxide. They carry a brown color on the tip, and AWS classifies them as EWZr-1. Brown TIG welding electrodes were developed as an alternative to pure tungsten, which you can see from the high tungsten content.
Similarly, zirconiated tungsten electrodes are used for AC welding jobs which include TIG welding aluminum 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.
TIG welding with
zirconiated tungsten electrode
Brown 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.
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 aluminum alloys and non-ferrous metals at AC TIG welding.
Due to its favorable 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.
The AWS classifies lanthanated tungsten electrodes into three separate grades depending on the addition of lanthana:
electrodes contain 0.8-1.2 weight-percent lanthanum oxide and carry
black coloron 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.
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 La
2
O
3
, and you can distinguish them by the
gold coloron the tip.
WL15 Series 1.5% Lanthanated TIG WeldingTungsten Electrode
EWLa-2 electrodes
contain 1.8–2.2 wt.-% dispersed lanthanum oxide, which is among the highest amount of oxides in all AWS-specified electrode types. The high addition of oxides allows
blue tungstento resist high pulsing and amperage loads while retaining excellent arc start performance with a low consumption rate.
WL20 Series 2% Lanthanated TIG WeldingTungsten Electrode
The rare earth tungsten electrodes contain rare earth oxides that are not specified by an existing classification. The AWS classifies them as EWG electrodes, and manufacturers must use any color other than those standardized (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.
After choosing the correct tungsten electrode for your application, you must prepare its tip according to requirements. Typical preparations include balled, pointed, and truncated tungsten tips.
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.
For more information, please visit Tungsten Carbide Rod.
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 specialized tungsten electrode sharpener with a diamond grinder to sharpen the tungsten electrode.
TTG02 Tungsten Electrode Sharpener Grinder
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. This is because grinding the taper produces a more focused arc, increasing the overall penetration and stability. However, be careful when grinding thoriated tungsten electrodes due to already-known health risks.
Welding thin gauge aluminum 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.
By understanding the characteristics of each electrode type and tungsten preparation, you can already make some deduction on which is the suitable tungsten for steel, stainless steel, or aluminum alloys.
Nonetheless, this last section of our article will serve as an excellent summary of everything we learned today.
To TIG weld carbon steel, you can use a wide variety of TIG electrodes, and the right choice will vary on the process amperage.
Seasoned welders will tell you that the most versatile choice for steel welding is thoriated electrodes (red electrode tip.) The sole reason is the ability to work well with both thick and thin steel, AC/DC applications, extremely stable arc, outstanding arc start characteristics, and final weld puddle results.
However, due to the health hazards of thorium, many welders today started using lanthanated electrodes. Gold tip tungsten presents an alternative and another excellent all-around choice for steel. It doesn't cause health issues, and it is durable, but it tends to work somewhat worse on low-amp applications. Meanwhile, blue tungsten works great on high-amp DC steel welding.
DC welding steel at low current will require ceriated tungsten electrodes. Gray tungsten produces a more stable arc with thin steel, which is considered an alternative to red or gold tungsten.
While TIG welding stainless steel is fundamentally different and more challenging than joining mild steel, tungsten electrode selection remains the same. You can successfully TIG weld stainless steel with thoriated, lanthanated, or ceriated electrodes.
Once again, red tungsten is a versatile all-around choice for stainless steel, but you can use lanthanated electrodes as an alternative due to safety concerns. Ceriated tungsten will work better than gold tungsten on low-amp stainless steel applications.
Photo by @weldinginoxita
TIG welding aluminum requires an alternating current, so you will need a tungsten electrode that works great with it. Pure tungsten (green) or zirconiated tungsten (brown) electrodes are typical choices.
Many welders choose green tungsten for aluminum due to its low price and decent arc performance when welding magnesium, aluminum, or other non-ferrous metals. However, pure tungsten has the highest consumption rate of any tungsten type and tends to spit at higher amp applications.
When cleanliness is crucial, AC TIG welding will require zirconiated tungsten. Even though it is more expansive than green tungsten, brown electrodes show better arc start, lower consumption, and weld puddle contamination.
Photo by @pacificarctigwelding
Red, blue, gold, or green tungsten might sound confusing to you as a beginner, but understanding how they affect weld arc performance is crucial in ensuring the best results. Luckily, the AWS classification allows you to distinguish each type of tungsten by its color and know its composition.
By understanding the properties of each TIG electrode type, choosing the right one for your application should be a piece of cake. Hopefully, our article helped you understand a small part of the complicated puzzle called TIG welding.
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Tungsten electrodes may be used with a variety of tip geometries. In AC welding, pure or Zirconiated tungsten electrodes are usually used and are melted to form a balled end. This section of the guidebook is dedicated to grinding electrodes for DC welding. The complete geometry for DC welding is comprised of the electrode diameter, the included angle (a.k.a. taper) and the tip (flat) diameter. In addition, the surface finish of the grind is also important.
Figure 2: Electrode Geometry
Choosing the best electrode geometry requires compromise among various attributes such as: shorter to longer electrode life, easier to more difficult arc starting, deeper to shallower weld penetration, and wider to narrower arc shape (and thus bead shape and size as well). Whichever geometry is selected, it should be used consistently as part of a successful welding procedure.
For best results, electrode configuration should be tested while welding procedures are being developed; it should be noted as a critical process variable for the weld procedure; and close tolerances should be held for all subsequent welds.
Electrode Diameter: The welding equipment manufacturer’s recommendations are almost always the best way to choose which diameter electrode to use. There are also guidelines published by the American Welding Society, which are duplicated in Table 2 of this guidebook. Note that larger diameters can accommodate higher amperages; and larger diameter electrodes will last longer than smaller ones, but smaller ones will be easier to arc start. Use of higher current levels than those that are recommended for a given electrode size will cause the tungsten to deteriorate or breakdown more rapidly. As the tip erodes, the probability of tungsten particles falling into the weld pool and contaminating the weld is much greater. If the current used is too low for a specific electrode diameter, arc instability can occur.
For a given level of current, direct current with the electrode positive requires a much larger diameter, because the tip is not cooled by the evaporation of electrons but heated by their impact; and thus it will become hot and subject to erosion. In fact, an electrode used with DCEP can handle approximately only 10% of the current that it could with the electrode negative. With AC welding, the tip is cooled during the electrode negative cycle and heated when positive. Thus, an electrode on AC can handle the current somewhere between the capacity of an electrode on DCEN and DCEP and about 50% less than that of DCEN.
Electrode Tip/Flat: The shape of the tungsten electrode tip is an important process variable in precision arc welding. A good selection of tip/flat size will balance the need for several advantages. The bigger the flat, the more likely arc wander will occur and the more difficult it will be to arc start. However, increasing the flat to the maximum level that still allows arc start and eliminates arc wander will improve the weld penetration and increase the electrode life. Some welders still grind electrodes to a sharp point, which makes arc starting easier. However, they risk decreased welding performance from melting at the tip and the possibility of the point falling off in the weld pool. In situations where very low amperage is used or short weld cycles are used (i.e., one second or less), a pointed electrode is desirable; however, for other situations it would be beneficial to prepare a flat at the end of the electrode.
Guidelines for testing can be found in Table 6; also refer to the welding equipment manufacturer’s recommendations. During the welding operation, the accurately ground tip of a tungsten electrode is at a temperature in excess of 3000° C (5500° F). Incorrect or inconsistent diameter flat at the tip of the tungsten electrode can lead to the following problems:
In AC welding, pure or Zirconiated tungsten electrodes melt to form a hemispherical balled end. For DC welding, Thoriated, Ceriated, or Lanthanated tungsten electrodes are usually used. For the latter, the end is typically ground to a specific included angle, often with a truncated end. Various electrode tip geometries affect the weld bead shape and size. In general, as the included angle increases, the weld penetration increases and the width of the weld bead decreases. Although small diameter electrodes may be used with a square end preparation for DCEN (Direct Current Electrode Negative) welding, conical tips provide improved welding performance.
Table 6: Tip Recommendations by Electrode Diameter Size
Electrode Included Angle/Taper: Electrodes for DC welding should be ground longitudinally and concentrically with diamond wheels to a specific included angle in conjunction with the tip/flat preparation. Different angles produce different arc shapes and offer different weld penetration capabilities. In general, blunter electrodes that have a larger included angle provide the following benefits:
Sharper electrodes with smaller included angle provide:
Larger tungsten diameters and higher currents are normally paired with larger tapers in the 25° to 45° included angle range in order to increase electrode service life and provide a more stable arc. More pointed tips in the 10° to 25° included angle range are used for lower current.
Electrode Angle Surface Finish: The smoothness of the finish on the prepared tip of the electrode will determine some of the characteristics of the welding process. In general, points should be ground as fine as possible to improve welding properties and increase the service life of the electrode. Electrodes that are ground too coarse result in unstable arcs.
Surface finish is typically expressed as a Root Mean Square (RMS) or as a Roughness Average (Ra). RMS is a comparative number as related to surface finishes measured with a profilometer. A fine finish is in the range of 20-40 RMS, a machined finish often is in the range of 80-120RMS, and grit blasted surfaces will be in the range of 400-500 RMS. The Ra value is defined as the average value of the departures from its centerline through a prescribed sampling length. Measured values expressed as RMS will read approximately eleven percent higher than values expressed in Ra. (Microinches x 1.11 = RMS).
A standard finish of around 20 RMS, which would still show the longitudinally ground lines to the naked eye, is an all-purpose, quality finish for any application. A high-polished or mirror-like finish of approximately 6-8 RMS, where few or no lines can be seen, is better for the longevity of the electrode because without any grit to the electrode surface, it is much less likely for contamination to “stick” to the electrode point and thus less erosion takes place. However, for welding power supplies that do not have strong arc starting characteristics, a finish of approximately 20 RMS is better because the longitudinally ground lines will help steadily lead the electrons to the extreme point of the electrode which assists in arc starting. Some manufacturers of pre-ground welding electrodes provide coarser finishes in the 30 to 40 RMS ranges; however, these do not last long, they provide unstable arcs, and they tend to be too gritty for extended, effective arc starting.
Typical Manufacturers’ Recommended Geometries: Many manufacturers provide information on recommended electrode geometries, because they have already preformed testing to determine which electrode geometry is the most beneficial for their equipment in various applications. However, when this information is not available, Diamond Ground Products, Inc. or other industry experts are the best source for this information.
Tolerances Required for Different Applications: Many welding applications are deemed highly critical and require strict tolerances on the length, taper, and flat, in addition to a high-polished finish. These applications include orbital tube welding for high purity, pharmaceutical, aerospace applications, fitting manufacturing, and many others. Basic guidelines for tolerances in these applications are ± .002” for the length, ±½° for the taper, and ± .002” for the tip/flat. Where applications require electrodes to be manufactured to these extreme tolerances, it is necessary to use equipment such as an optical comparator, microscope, and micrometer in addition to the precision tungsten electrode grinder which is required for almost all applications. Other applications will often call for their own specific tolerances. Where not specified, keep reasonable tolerances for the type of work being performed and remain as consistent as possible.
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