Electrode classification

The tungsten electrode has many different alloys that will affect the arc stability, starting, and longevity. These tungstens are color-coded for ease of identification during the work day. We will talk about a few of the main alloys of tungsten you will see and use. It is important to be aware that new alloys are being developed for specific purposes such as Stainless steel, aluminum, and robotic welding.

The old guard: Green and Red Tungsten

Green

The color green indicates that the tungsten electrodes are 99% pure. Green tungsten is used in AC welding of aluminum and magnesium. The end of the tungsten will ball as you weld giving good arc stability and relatively good resistance to contaminating the weld. This tungsten is for transformer machines only.

Red 2% Thoriated

Red color indicates that the tungsten contains 2% thorium. For a number of years, this was the most common tungsten used because of its versatility. This tungsten has a long service life, easy arc starting, high current capacity, and good resistance to contaminating the weld.

Red 2% Thoriated tungsten is used for welding carbon steel, stainless steel, nickel alloy, titanium, and copper. However, it can not be used for AC welding. The tungsten will not ball and it will contaminate the weld. Thorium is radioactive. Proper caution should be taken when using this tungsten. Most notably, take proper caution of the grind dust that is produced when sharpening the tungsten. Take proper care to collect and discard grind dust appropriately. You will also want to wash your hands after grinding. Review the SDS for proper handling instructions.

New and improved Tungsten

Gold 1.5% and Blue 2% Lanthanated

Gold and blue tungsten are alloyed with lanthanum giving them very strong characteristics such as easy arc starting, re-ignition, and arc stability. Gold 1.5% and Blue 2% tungsten each have a long service life and resistance to thermal shock when pulse welding. They have high resistance to contamination and will maintain an arc at a very low current. These can be used in DC and AC welding, making them incredibly versatile.

Gray 2% Ceriated

ontains 2% cerium. Excellent for very low amperage starting, good arc stability and long life. Performs very well with both AC and DC welding.

White .8% Zirconiated

Produces an extremely stable arc, maintains a balled end, and is highly resistant to contamination and spitting. Good replacement for pure (green tungsten). White .8% Zirconiated tungsten is used for AC welding when contamination is intolerable. This tungsten handles high amperage for welding aluminum and magnesium alloys.

Purple: Rare Earth Trimix

Purple tungsten is a good substitute for red 2% thoriated. It is very durable and produces reliable arc starts. It will perform well in both AC & DC welding applications. Purple tungsten is used for welding aluminum alloys, magnesium alloys, titanium alloys, nickel alloys, copper alloys, low-alloyed steels, and non-corrosive steels.

Maintaining Tungsten

Maintaining your tungsten is critical. When welding DC, you will want to sharpen the tip to a point. This will give you maximum control of your arc. After sharpening, you will want to blunt the tip slightly. This helps keep small bits of tungsten from falling into the weld creating inclusions. It’s also a good practice to strike an arc on a piece of scrap for a few seconds before you start to weld. This further reduces the possibility of tiny bits of tungsten from falling into the weld.

When sharpening make sure all grooves are long ways in relation to the tungsten. This helps direct the arc to the tip of your tungsten. Grooves going around the tungsten will create an unstable arc.

Balling tungsten

This practice is used with pure (green) tungsten electrodes welding with a transformer-type power source (weld machine). This can be accomplished in multiple ways. Set the machine to DC electrode negative (reverse polarity) and strike an arc for a second or two. Watch your tungsten closely. The end will begin to ball up. You do not want to overdo this; just round the end a little.

Another way to do this is to leave the settings of the machine on AC and strike an arc on a piece of scrap metal. It will take a little longer for the end to ball, but eventually, you will get the same result. You can adjust the balance of your machine to favor DCEP or the cleaning action, and your tip will ball more quickly. Be sure to adjust the balance after completing this task, as it will put excessive strain on your tungsten.

The profile of the tip you are looking for is rounded like the tip of your pinky, not your fist.

GTAW electrode (Filler rod) classification

Carbon steel filler rod

Classifications are the same for GMAW and GTAW even though the current is not conducted through the filler rod.

ER70S-2

ER= electrode or rod

70= tensile strength

S= solid wire

-2 is chemical composition. Deoxidizers and stabilizers

Stainless filler rod

ER309-L

ER= electrode or rod

309= Alloy for stainless this will be three digests

-L= low carbon

Aluminum

ER4043

ER= electrode or rod

4043= Alloy for aluminum this will be four digests

Attributions

1. Figure 11.11: Shape of Tungsten Electrode Tip by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
2. Figure 11.12: Grind Grooves on Tungsten Tips by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
3. Figure 11.13: Pure Tungsten with a Balled Tip by Karl Fulton, for WA Open ProfTech, © SBCTC, CC BY 4.0