Understanding welding, complete with all its terminologies and methods, is hard work. A lot of the time, newbies struggle with why and how things are done. One such confusion is balling tungsten. Why should you ball tungsten before welding? Does regular tungsten not work as well?
Aluminum is a trickier metal to weld with. Welders often find it easier to work with steel or steel alloys, because aluminum takes higher temperatures to heat up. To weld aluminum, TIG is usually used. Occasionally, a welder might use MIG for aluminum welding too.
Tungsten Inert Gas (TIG) welding requires a non-consumable tungsten electrode. It uses the heat generated by an electric arc struck between the tungsten electrode and the metal workpiece. A pointed tungsten electrode was traditionally used to strike the arc, but now we know that balled tungsten yields better results. Balling tungsten for aluminum welding requires the welder to follow a series of steps. While tungsten balling isn’t the only method that guarantees better welding results, it is one of the primary ones, along with the welder’s welding technique, shielding wire, and the inert gas used when welding aluminum.
What are the Unique Challenges of Welding Aluminum?
Welders often find that it is harder to weld aluminum as opposed to regular steel, and it requires some special settings and arrangements. So what is it that makes welding aluminum so challenging? The basic difference between aluminum and steel lies in the two materials’ thermal conductivity and porosity.
Aluminum is a much better heat conductor than most metals. While that makes aluminum extremely useful in other applications, in welding, it is a huge inconvenience. The cooler parts of the metal keep pulling the heat away from the weld pool and can cause the weld to be weaker and less penetrating. To fight the problem, substantially higher temperatures are required to weld aluminum, as compared to steel.
In liquid form, aluminum absorbs hydrogen. But when it starts to solidify, it cannot hold the hydrogen in the same form. The hydrogen thus results in the formation of bubbles in aluminum, giving way to porosity issues. While hydrogen is not capable of causing cracks in aluminum welds, hot cracking does occur. Sometimes an argon and helium mixture as the shielding gas helps to lower the hydrogen bubbles formation, and thus, reduces the porosity.
For these reasons, welding aluminum requires more concentration, more technique, and more heat control.
Why Is Tungsten Used In Welding?
Tungsten is the choice metal that is used in welding because it is the metal with the melting burning point among all pure metals. Tungsten melts at a very high temperature of 3,422 °C (6,192 °F). In welding, the tungsten needs to be non-consumable. Thus, tungsten is used to make the electrodes because it can withstand the high temperatures and does not burn off during the process. Some erosion is to be expected and is called the “burn-off,” but generally, tungsten fares better than other metals when it comes to aluminum welding.
Traditionally, only pure tungsten was used, but now, there are many tungsten alloys that are approved by the International Organization for Standardization and the American Welding Society, that have more superior qualities than regular tungsten.
What is Tungsten Balling?
Tungsten balling simply refers to making the pointy edges of the tungsten electrodes softer and rounder. When working with pure tungsten electrodes, balling is considered necessary.
Why is Tungsten Balled?
Balled tungsten is said to perform better and create better arcs than sharp, pointed tungsten electrodes. When only pure tungsten was used to make electrodes, it was deemed as necessary to ball the electrodes for optimal performance, but the answer varies today.
With so many different tungsten alloys entering the market, and all being approved by the American Welding Society, the answer to “Is tungsten balling necessary for aluminum welding?” has changed. If you opt for the tungsten alloys to make the electrodes that you’ll be using in your aluminum welding, you don’t need to ball them up at all. Some of the common, approved alloys include:
Cerium oxide (or ceria) as an alloying agent improves arc stability, and it has the added advantage of not being radioactive!
An alloy of lanthanum oxide (or lanthana) also improves the arc stability and performance and is also not radioactive.
Thorium oxide (or thoria) gives great arc performance and is great for general purpose use. While it is one of the best to work with, it is radioactive and can pose more of a health risk than any of the others.
Tungsten electrodes containing zirconium oxide (or zirconia) improves arc stability and also increases electrode life, so you don’t have to keep replacing the electrodes every so often.
How is Tungsten Balled for Aluminum Welding?
In case you’re working with pure tungsten and need to ball your tungsten for aluminum welding, here’s what you need to do. Wear protective clothing and get to work. Don’t focus too much on making a perfect ball on the tip; just make sure the tungsten is rounded.
- Sharpen one side of the pure-tungsten electrode to a spiky tip using a bench grinder.
- Put the sharpened electrode aside for 10 minutes, letting it cool down.
- Sharpen the other edge of the electrode to a point too, exactly like the other end.
- Place the tungsten electrode in a TIG torch.
- The ground of the TIG welder must be connected to a conductive work surface, and a piece of aluminum should be placed on top of it.
- Place the sharp tip of the electrode 1/8 inch away from the scrap piece of aluminum. Now, start up the welder. Keep the welder running for 2 – 3 minutes till a ball of 1/3 the diameter of the tungsten electrode is observed on the tip of the electrode.
- Again, let the electrode rest. After it has cooled down, you can go ahead and use it to weld aluminum.
There you have it – a complete, step-by-step guide on how to ball tungsten for aluminum welding. However, pure tungsten isn’t even recommended by welders anymore, so save yourself the trouble and choose a better alternative that will not require you to ball it in the first place.
What is the best inert gas to use in aluminum welding?
The ideal choice for a shielding gas in aluminum arc welding is 100% pure argon gas. Pure argon gas and pure helium gas are the two top choices to be used all sorts of welding work.
Is balling tungsten dangerous?
Some tungsten alloys are radioactive and can pose a health risk, but otherwise, balling a tungsten electrode is no more dangerous than the welding itself. Sharpening the thoriated tungsten could generate radioactive dust, which could be severely harmful if ingested.
Can you use a pointed tungsten electrode?
Yes, you can, and traditionally, the pointed electrode was used a lot, but it is better to ball the tungsten to increase the stability of the arc and improve performance.
What type of tungsten should be used for welding?
There are multiple types of tungsten you can choose from:
- Rare Earth Mix
- 2% Lanthanated
- 0.8% Zirconiated