If you want to know how to weld aluminum, you’re in good company. There are endless uses for this metal – and just as many welding projects that involve aluminum. It’s a fairly soft metal, with an optimum weight-to-strength ratio. These factors, coupled with its general aesthetic appeal, make it the top choice for a huge variety of applications.
Naturally, this means that aluminum gets welded a lot. But what’s the best way to weld aluminum? There are actually two different techniques that work best for this metal, which are explored below.
Why welding aluminum can be tricky
One of the main challenges of welding aluminum is created by its oxidized outer layer. Since aluminum has an affinity for oxygen, this layer forms on any aluminum surface that’s exposed to air. In any other context, this isn’t a problem. If you’re trying to weld aluminum, though, this outer layer will cause all kinds of issues. Pure (and un-oxidized) aluminum will melt at 650 ̊ C; however, the outer layer has to be heated up to 2,037 ̊ C before melting. If you want to successfully weld aluminum, no matter what technique you’re using, this outer layer will have to be removed first.
Another challenging aspect of learning how to weld aluminum stems from its high thermal conductivity and low melting point. In a nutshell, this gives you less time to work before you burn a hole right through the metal. Fortunately, this is something that can be avoided with caution and plenty of practice.
How to weld aluminum with MIG
The fact that MIG welding uses less heat than some other techniques makes it ideal for welding aluminum. It’s also easier to work faster with MIG welding, which is another plus.
- Choose the right filler material – The filler should be chosen based not only on the type of aluminum you’re working with, but also based on the purpose the project is for. Is a strong weld essential, or do you just need the pieces to stay together and look nice?
- Clean the surface – If you’re going to MIG weld aluminum, thorough cleaning is a must. This means removing paint, grease, and other contaminants, but it also refers to the oxidized outer layer. You can easily get rid of debris and dirt with degreasers or solvents, but the outer layer will take a little more effort. A stainless wire brush is most effective; if you’re using a power wire brush, use a lower RPM setting to avoid smearing on the surface.
- Use the correct shielding gas – Even if you haven’t learned how to weld aluminum, you may already know which shielding gases can be used for MIG welding. To setup a MIG welder for aluminum, make sure the gas cylinder is 100% argon gas; it works perfectly for welding aluminum.
- Consider the thickness of the material – If you’re going to MIG weld aluminum, the metal should be at least 14-gauge; anything less than that, and you’re likely to burn holes through the metal. If there’s no way around using a MIG welder for aluminum, the best option is to use a specialized pulse MIG welding setup.
How to TIG weld aluminum
It should come as no surprise that you can TIG weld aluminum; after all, you can TIG weld just about anything. Used for everything from art installations to racecars, TIG welding’s tidy seams and overall versatility make it a favorite among welders. One benefit of TIG welding aluminum is that it lowers the risk of contamination; if you know how to weld aluminum, you’ll know that this is important to avoid.
- Use the right filler metal – You may or may not decide to use filler material, depending on the type of project you’re working on. Make sure to consider the thickness of the metal, joint design, and alloy when choosing the filler metal.
- Clean before welding – Just like with MIG welding, the TIG welding process requires the removal of the outer oxidized layer.
- Select your shielding gas – Again, you’ll be doing the same thing with both MIG and TIG welding. 100% argon gas works well here, but you could also use helium (or a mixture of the two) if that’s what you already have on hand.
- Choose the right electrode – Since you’re TIG welding, you’ll need a tungsten electrode; fortunately, any type of tungsten electrode will work if you’re going to TIG weld aluminum. You could go for the budget-friendly pure tungsten electrode, or a more expensive thoriated tungsten electrode; it’s up to you. Those who are learning how to weld aluminum for the first time usually go for the cheaper electrodes, and why not? In this case, there actually isn’t much to be gained by switching to another type.
- Grind the electrode – With TIG welding, the shape of the electrode’s tip will influence the heat distribution; you want to distribute it as widely as possible. To get this effect, make sure the electrode has a ball tip rather than a point.
- Adjust amperage and gas flow – TIG welding gives you a lot of control over several aspects of the process, so you’ll need to keep an eye out for anything that needs to be adjusted. Since aluminum melts at a lower temperature than many metals, a lower amperage may be needed.
- Use AC electricity – High-frequency AC works best here; if you’re learning how to weld aluminum, this approach lets you balance weld penetration with surface cleaning, while also preventing the tip of the electrode from getting too hot.
Can you learn how to weld aluminum using other techniques?
Even though MIG and TIG welding are the most popular techniques for welding aluminum, they’re far from the only options.
- Friction welding doesn’t require the metal to melt in order to fuse; this technique works with the most stubborn aluminum alloys.
- Electron beam welding offers the advantage of producing pure welds, even without the use of shielding gas. That being said, there’s still a pretty high risk of cracking with this technique.
- Laser beam welding is optimum for metals that require clean, quick welds – such as aluminum. You’ll have to use shielding gas with this technique; the type you choose will depend on the kind of aluminum that’s being welded.
The takeaway
Welding aluminum takes a fair bit of know-how, but that’s a small cost compared to the many benefits we get from using aluminum every day. From its corrosion resistance, to its conductivity, to its overall strength, aluminum is something we’ll always find uses for. Just like with welding, you start to appreciate it more every time you learn more about it. Now the only question is – when will you learn how to weld aluminum?
