TIG Rods and Tungsten
Compared to other welding processes, in TIG there’s a lot going on. A shielding gas, usually argon, is running through the torch. You have an electrode that’s made of tungsten, an extremely hard steel that stands up to high heat but can get easily contaminated during welding an may need to be sharpened often. Sometimes, the tungsten itself will require a special alloy ingredient added to provide a stable arc, which helps produce an uncontaminated weld.
If that all weren’t enough to wrap your head around, you’ll also be welding with a filler rod in your other hand. That makes three consumables that get used up and replaced periodically – gas, tungsten and filler. Notice in the image below the rod isn’t even included, yet all the gear and cords still fill up the space.
Technically, the tungsten used in welding is not a consumable, since it’s not meant to serve as filler rod. A seasoned welder can make a tungsten electrode last a long time. A newbie, on the other hand, may go through one seven-inch stick every week. The electrodes are packaged in various quantities, but ten-packs are the most popular. Tungstens come in seven or three-inch lengths, which correspond to the two standard tips available on TIG torches. The electrodes are also sold in a range of diameters, just like stick welding.
What’s unusual about tungsten is the variety of exotic alloys used to influence its performance. In order to distinguish one from another, a color code has been developed. Here are the most common choices, their colors, AWS and ISO numbers, and what they’re used for:
- Pure Tungsten – EWP — Used primarily for AC welding of aluminum and magnesium at low currents. The tip of the tungsten must be balled before using. (ISO = W)
- Lanthanated 1.5% – EWla-1.5 –General purpose electrode used for steel and stainless steel at a wide range of currents. Often used as a cheaper, safer substitute for high-priced thoriated tungsten. (ISO = WL15)
- Ceriated 2% – EWTh-2 — Can achieve high currents with good arc stability. Another substitute for thoriated tungsten. (ISO = WC20)
- TIG Welding Rods & Tungsten – EWTh-2 — An expensive and radioactive metal. Use care in grinding (i.e. wear a dust mask), keep your skin covered and avoid contact with the metal when it’s heated. (ISO = WT20)
- Zirconiated 2% – EWZr-2 — Another option for AC welding, zirconium is preferred in situations where resistence to contamination is paramount. The tip of the tungsten is balled before using. (ISO = WZ3)
The yellow code listed in parantheses represents International Standards Organization (ISO) classifications, which some manufacturers include when labeling products. The letter “W”, incidentally, stands for wolfram, which is used in place of the word tungsten in most countries. (In the periodic table, tungsten is represented by the letter W.)
For additional info on these electrodes, read the tungsten selection page provided by ProFusion.
TIG Filler Rods
Filler rods for TIG are fed by a second hand as the first holds the tungsten torch. These rods typically come in 3-foot lengths and are packed in 10 or 50-pound boxes (or tubes). A welder’s choice of diameter ranges from 1/16″ to 1/4″. Since the composition of the filler rod is the same as MIG, some of the same products are sold for TIG welding, identified as “TIG cut lengths”.
Here are a few of standard rods governed by AWS and ASME codes:
These products are typically used for small-diameter pipe and tubing, sheet metal applications, and root-pass pipe welding (i.e. the first pass only). Typical AWS numbers include ER70S-2, ER70S-6 and several other ER70S-series options with different digits at the end. Each represents a recipe of chemical additives in the filler metal to address specific conditions of the metal (e.g. dirty or clean) or the type of joint being welded.
Popular because of their high resistance to rust and corrosion, stainless steel alloys combine carbon steel with 10% or more chromium. As explained elsewhere on this website, each of the base metals welded on has its own classification. And those numbers are incorporated into the filler rod classifications. Basically, stainless steel is divided into three categories worth noting: austenitic (such as 302, 306, 308, 309), martensitic (such as 410, and 416), and ferritic ( 409, 430). If you’re not sure what kind of metal you have, the ferritic stainless steels stick to a magnet. The others don’t.
The following TIG/MIG classifications for wire and rod can be used on sheet metal, high pressure pipe and tubing.
ER308 and ER308L – One of the most common welding rods, it’s the choice for welding 304 stainless steel, which is widely used in manufacturing, as well as 200-series and other 300-series steels.
ER309 and ER309L – Used for welding dissimilar metals. Can handle higher heat than has good corrosion resistance.
ER316 and ER316L – Commonly used for pressure vessels, valves, chemical equipment and marine applications.
The “L” refers to extra low carbon in the rod (less than .08%), which helps even more in preventing corrosion. The numbers above are some of the more popular, but the roster of stainless steel base metals manufactured today is vast.
There are two standard rods used in TIG (although others are available).
ER4043 – For welding 6000-series aluminum alloys, along with most casting alloys. This typically covers automotive components such as frame and drive shafts, and bicycle frames.
ER5356 – This aluminum-magnesium alloy is good for welding cast and wrought aluminum alloys. Generally recommended for welding any 5000 or 6000- series aluminum alloys.
As in other forms of welding, choosing a filler rod depends on the base metal, type of joint, thickness and thermal properties of the metal. If you poke around, you will eventually find easy-to-follow reference charts that connect different metals and alloys to the appropriate filler rod. Also be sure to find out the current (amperage) range of the rod, polarity and any other specifications before you strike an arc and start welding with it.
Next: Oxy Gas Filler Rods