Tungsten is used as an electrode in the TIG welding process, hence the name: TIG-Tungsten Inert Gas, or GTAW-Gas Tungsten Arc Welding. It’s an especially useful metal in the welding field because of a couple of unique properties that lend themselves well to welding. The first of these is its melting point. It has the highest melting point of all metals; (6192°F or 3422°C). Another useful characteristic of tungsten is that it has the lowest coefficient of thermal expansion of any pure metal. As you can see, both of these properties lend themselves very well to any process that requires extreme heat, namely welding.
Tungsten Electrodes are outlined in A.W.S.-5.12, and come in several different sizes, lengths, and alloy compositions. The type of tungsten electrode is easily identified by a colored band on one end as outlined below.
Green-pure tungsten-AWS EWP
Black-1% lanthanum-AWS EWLa-1
Gold-1.5% lanthanum-AWS EWLa-1.5
Blue-2% lanthanum-AWS EWLa-2
Brown-1% zirconium-AWS EWZr-1
Orange-2% cerium-AWS EWCe-2
Gray-Rare Earth-AWS EWG
Red-2% Thorium -AWS EWTh-2
Yellow-1% Thorium -AWS EWTh-1
Red and Yellow band tungsten are thoriated tungstens. The most popular of these would be the red band tungsten. It has a thorium content of approximately 2%. It’s used to weld both carbon and stainless steels, titanium, nickel, and copper alloys. It’s primarily used with DC welding, although at lower amperages it can be used with AC. Thoriated tungsten electrodes provide a very stable arc, and are the longest lasting electrodes available. One thing to note about these electrodes is that Thorium is radioactive. You should always wear a respirator and follow proper safety procedures when sharpening them
Green band tungsten is pure tungsten, and is used primarily with AC on aluminum and magnesium. Since there is no alloy in them they’re the cheapest of the electrodes, but they also burn up the fastest. When you strike an arc with one, it will ball up on the end. This is normal and helps provide a more stable arc when welding.
Brown band tungsten is zirconiated tungsten. It has a zirconium content of approximately 2%. It’s used only for AC welding. Like pure tungsten, it too balls up when you strike an arc. A benefit of zirconiated tungsten is its high current carrying capacity.
Black, Gold, and blue band tungstens are lanthanated tungstens. They have a lanthanum content of approximately 1,1.5,and 2% respectively. They’re a good all-purpose choice since they can be used for either AC or DC welding, and will ball up or hold a point well if sharpened. Due to the addition of lanthanum, these electrodes can carry approximately 50% more current than pure tungsten. Also, because of the lack of radioactive material in them, lanthanated tungsten is often specified as a replacement for thoriated.
Orange band tungsten is ceriated tungsten. It has a cerium content of approximately 2%. It’s a great electrode for use with DC at low amperage levels on steel, stainless, titanium, nickel and nickel alloys, and copper alloys. It can also be balled up for use with AC. Its not for use at higher amp levels though, higher heat levels will causes the cerium to migrate from the tungsten. This same effect can be achieved through the use of pure tungsten electrodes, at a lower price.
Gray band tungstens are specified as a rare earth tungstens that don’t fit into any of the above categories. They can contain unspecified oxides, or combinations of the above mentioned additives. Whatever the content is, the manufacturer will list it on the package. It’s worth noting that there can be several different types of gray banded tungsten electrodes, and they could all possess differing characteristics depending upon the composition. Because of this they could be used for either AC, DC, or both.
If you’re interested in more information,Sylvania is a quality manufacturer of tungsten electrodes and has some great information about their products.
There’s a lot of discussion as to the best geometry, and proper way to grind an electrode. To sidestep that argument, the best way is the one that works best for you. Generally speaking, a pointed electrode with a longer taper is better for thin metals when using DC. For thicker metals using DC, a pointed electrode with a smaller taper is preferred. For aluminum, it’s an electrode with a ball on the end. That said, the best way is the way that allows you to produce the best welds. Only practice and experience will tell you what’s right for you. You can read about how to grind an electrode HERE.
As to what size works best, it’s what you’re most comfortable with. For most people it’s easier to use a .020″ tungsten for thin metal than it is to use 1/8″. But it all comes down to what you prefer. I know welders that use 1/8″ tungsten @ 40 amps when welding thin wall tubing and make some of the best welds I’ve ever seen. I’m not one of those welders though.
End Date: Thursday Aug-28-2014 1:05:49 PDT
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