How to Choose the Right Tungsten for TIG Welding?

How to Choose the Right Tungsten for TIG Welding?

Once you’ve invested in a top of the line TIG welding machine for aluminum welds or detailed projects, get the most out of your welds by picking the right TIG welding tungsten. Whether you’re using AC or DC processes for TIG welding, here are some tips to keep in mind when it’s time to stock up on TIG rods, including a new rod you may not know about. 

Choosing the Right Color Tungsten for TIG Welding

Each TIG welding electrode has a specific color classification that makes them easy to identify. Based on the composition of the electrode, welders will find specific applications and benefits that may work best for each electrode. Here is a brief roundup:

Green TIG Welding electrodes are pure Tungsten and are used for AC welding, often for aluminum and magnesium. They tend to be commonly used because they are inexpensive. However, they also burn up much faster than the other alloy electrodes, so prepare to stock up if you go this route.

Why use green, pure tungsten electrodes? They work well on AC sine wave welding and form a solid balled tip that results in a stable arc. Besides the high consumption rate, it doesn’t start as well as thoriated or ceriated electrodes, which remain the favorites among many welders.

Red Thoriated TIG Welding Electrodes are among the most commonly used electrodes because the 2% thorium mixed with the tungsten is durable and versatile. Welders can grind the tip of these electrodes to a sharp point and enjoy and stable arc that last a long time. The final weld puddle is cleaner since the electrode leaves fewer deposits, and thorium allows for easier arc starts and higher current-carrying capacity.

Switch between AC or DC welding with Thoriated electrodes. Welders can work on projects that include thin aluminum, titanium, carbon steel, stainless steel, and nickel. Since thorium is radioactive, welders remain cautious about using these electrodes.

Orange Ceriated TIG Welding Electrodes contain about 2% percent ceriated and are ideal for DC welding and lower current processes. Since it can weld carbon steel, stainless steel, nickel alloys, and titanium, some welders have found that it works well as a replacement for thoriated electrodes.

Ceriated is not recommended for welding at higher amps since the heat can change the composition of the electrode. Welders prefer to work with Ceriated electrodes at lower temperatures for small, precise parts, pipe fabricating, and welding thin metal.

Gold Lanthanated Electrodes for TIG Welding work in both AC and DC (electrode negative) settings since they can be sharpened or balled respectively depending on the project. It can weld steel from a square wave power source and it offers reliable arc starts and arc stability.

Due to its durability and versatility, some welders use Lanthanated in place of thoriated since there are no radioactive elements in the metal.

Brown Zirconiated TIG Welding Electrodes have a minimal amount of Zirconium and are best used only for AC welding jobs. Since the zirconium is a strong metal that resists cracking, it produces a stable arc and resists contamination. It can also carry an amperage current that is comparable to thoriated electrodes.

Gray Rare Earth Electrodes typically note which rare-earth oxides are present in the rod. These electrodes can be used for AC and DC welding jobs, but welders should take care to read the details of each metal listed on the package. At their best, rare earth electrodes can be counted on for a stable arc, longer life, and a current that rivals other electrodes even though they are usually smaller.

Get All Five TIG Electrodes in One Set

Can’t decide which electrode to purchase? Try out the new Weldporn Five Flavors Assorted Tungsten. These electrodes have been proven to provide stability and consistency in every weld. There are two of each electrode included in the set.

The options for the 3/32” electrodes include:

2% Thoriated

2% Ceriated

2% Lanthanated

Multimix

Pure Tungsten

The Purple Electrode Option

Purple E3 Tungsten If you’re looking for a safe alternative to thoriated electrodes and a longer lasting version of pure Tungsten, then you may want to consider the E3 Tungsten electrode that blends three oxides together. It has better ignition rates, it runs cooler, and there is no radiation. Compared to thoriated, it may even sustain a faster ignition and a more stable arc over time.

The E3 Tungsten is designed to give better arc starts and a longer lifespan for the electrode compared to pure Tungsten.

If you are planning to TIG weld with Aluminum check out this blog post.

Check out our YouTube video going over some common questions on Tungsten.

Tungsten electrodes

Wherever finely crafted weld seams are created, high-quality materials are welded and precisely welded joints are to be created, TIG welding is required – and good tungsten electrodes. With tungsten inert gas welding (TIG), in addition to the torch, the power source and the shielding gas, the non-melting, temperature-resistant tungsten electrode is an essential factor for optimal results.

The range of TIG welding electrodes is very extensive. At the latest when it comes to choosing the right TIG electrode for your own welding task, you will be confronted with colour coding of the tungsten electrodes. The individual electrode types are marked with different colours.

Tungsten Electrode Preparation

Electrode Geometry

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.

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:

Pointed electrode tip drops into weld pool creating weld defect

Reduction in electrode life

Arc instability

Change in arc voltage from one electrode to another due to inconsistent tip shape

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.

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:

Lasts Longer.

Have better weld penetration.

Have a narrower arc shape.

Can handle more amperage without eroding.

Sharper electrodes with smaller included angle provide:

Offer less arc weld

Have a wider arc

Have a more consistent arc

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.