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TIG Rods and Tungsten

ln TIG welding, there's a lot going on. You have a shielding gas, usually argon, running through the torch. You have an electrode that's made of tungsten, which is an extremely hard steel that stands up to high heat. But depending on the weld metal, the electrode needs a special alloy ingredient added so it can provide a stable arc and uncontaminated weld.

Finally, you'll often be welding with filler rod in your other hand. That makes three consumeables that get used up and replaced periodically.

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Tungsten Electrodes

Technically, the tungsten used in welding is not viewed as a consumeable, 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 tungsten every week. The electrodes are packaged in various quantities (10 packs are the most popular). They come in seven or three-inch lengths, which correspond to the two standard tips available with TIG torches. The electrodes come in a range of diameters similar to stick welding.

What's unusual about tungsten are the kinds of exotic alloys used to influence its performance in TIG welding. 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 is 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 current. Often used as a cheaper, safer substitute for thoriated tungsten. (ISO = WL15)

Ceriated 2% - EWTh-2 -- Can achieve high currents with good arc stability. Another substitute for thoriated tungsten. (ISO = WC20)

Thoriated 2% - 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)

grinding a tungsten electrode point

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 a little more description of 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, the same products are sold for TIG welding, under the category "TIG cut lengths.

Here are a few of standard rods governed by AWS and ASME codes which are the same ones used for MIG wire:

Carbon Steel:

These product classifications below are used to weld small diameter pipe and tubing andsheet metal applications, and oot pass pipe welding. 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.

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Stainless Steel:

Popular because of their high resistance to rust and corrosion, stainless steel alloys combine carbon steel with 10% or more chromium. The base metals are divided into three common categories based on their molecular structures; 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. To know which rods work on which base metals, print out this comprehensive Filler Metal Selector Guide for Stainless Steel.

Aluminum:

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.

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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. Be sure to find out the current range of the rod, polarity and any other specifications before you strike an arc and start welding with it.

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Getting set up to TIG weld aluminum TheFabricator.com

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How to Choose the Right TIG Torch Welding Consumable

Selection and Preparation Guide for Tungsten Electrodes

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Proper Tungsten Grinding Technique
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