Can You Weld Aluminum with Flux Core?

Flux core welding is a very common technique, and it’s mostly used when you’re trying to weld thicker metals. While you technically can weld aluminum with flux core, it’s not the ideal option. It ends up forming aluminum oxide on the metal’s surface, and that doesn’t allow the flux to penetrate properly. That means a special type of flux is required for welding aluminum, one that has cleaning agents designed to remove any aluminum oxide deposits.

What Is Flux Core Welding?

At its core, flux core arc welding is an automatic or semi-automatic arc welding process. It needs a consumable tubular electrode that gets continually fed into the welding unit. The electrode contains flux, and it also has a constant voltage. Sometimes, an external shielding gas is used, but usually, the flux will create liquid slag and gaseous protection, all of which are designed to protect the weld. Variables like the arc voltage, wire feed and travel speed, electrode angles, electrode wire type, and angles: all can influence the process and its results.

Understanding the Basics of Flux Core Arc Welding (FCAW)

The way flux core arc welding works is you have an electric arc that helps unite the base material with the metal electrode (used as a continuous filler). During the welding process, the flux provides a shield gas designed to prevent various issues like atmospheric elements or even oxidation.

FCAW is great for shipbuilding, water tank repairs, construction, etc. In general, it’s suitable for using materials that are larger than 20 gauge. That means it’s great to work on stainless steel, cast iron, and alloys with high nickel content, but also low alloy steel or carbon steel. It’s very common in the industrial and construction setting, mainly because it can be used outdoors. It’s portable, and it comes with a very high welding speed, something that makes it extremely effective and powerful.

Another thing to consider about flux core arc welding is that it has the highest deposition rate out of all the flux cored welding systems. That relates to how much filler metal gets melted within the weld joint. Additionally, you can perform the FCAW welding method in various, different positions, which can help provide a more consistent result.

Why Aluminum Welding with Traditional Flux Core Wire Is Problematic?

Aluminum properties make the process difficult

Using aluminum with flux core wire can be problematic because aluminum has distinct properties that bring certain issues. For example, it has a very high thermal conductivity. That means it will dissipate heat very fast, which requires more energy in order to deliver an adequate fusion. In doing so, the welding process can prove to be very inconsistent.

Another issue is that aluminum will form an oxide layer on its surface, and that melts at a higher temperature when compared to aluminum itself. That means you have to go through the oxide layer while welding; otherwise, the welding bond will not be strong. Aluminum is also soft and ductile, and that leads to distortion. You will need to have better control over the heat input so that you can avoid any defects, such as warping.  

The flux welding process becomes more challenging

The aforementioned characteristics of aluminum are bringing certain challenges when it comes to flux core welding. Because the aluminum wire is normally softer than steel, it’s easier for it to break or bend as you feed it into the welding system. And since flux cored wires tend to have hollow spaces, that further adds to the problem.

Moreover, it’s very challenging to create a flux that works with aluminum. If you use fluxes that are ok with other materials, those might not always work with aluminum. In fact, they can lead to spattering, corrosion, and a multitude of other problems. Additionally, the weld quality is lower due to aluminum being soft, a problem that can lead to porosity issues.

How to Weld Aluminum Effectively?

· A very important tip when you are welding aluminum is to ensure that you maintain a steady hand. Brace the hand over the working surface and avoid angling the torch excessively. It also helps if you keep your hands separated and use them independently.

· Cleaning the workpiece before welding is a great idea because it allows you to remove contaminants. Those can affect the weld quality if you leave them on the material. Alloys tend to be a major concern here since they can bring marks, stains, and discolored spots.

· If you want to weld aluminum properly, the best method is gas tungsten arc welding. Other options can include electron beam welding, resistance, or laser beam welding.

· When you choose the filler metal, make sure you consider any heat treatment requirements, along with toughness, strength, color matching, ductility, corrosion resistance, crack sensitivity, and the elevated temperature service.

· Also, there are a few best practices to consider when you are welding aluminum. You shouldn’t weave, and you want to remove the oxide layer continually. Property storing aluminum sheets to prevent any porosity is a must as well.

Preparing Aluminum for Welding

Generally, when you want to weld aluminum, you will need to go through 2, important steps:

1. First, you need to remove hydrocarbon contaminants, lubricants, grease, or oils. A wire brush won’t help. Instead, mineral spirits, toluene, or acetone will do the trick. Add those into a clean rag and allow the degreasing solvent to evaporate. If a higher volume is needed, you can use a mild alkaline cleaning solution.

2. After that, it’s important to remove any oxide from those areas that you want to weld. That will help avoid weld defects, including a lack of fusion. A wire brush is a very good pick for this task.

Common Mistakes in Welding Aluminum and How to Avoid Them

· Not wearing protective gear is a problem since the molten metal can be very dangerous.

·  Some people don’t remove any grease or oxide from the material beforehand. If you don’t prepare aluminum for welding, results can be very inconsistent.

· Picking the wrong welding torch type can be a mistake, as the weld can be very difficult to finalize in these situations.

· Some welders don’t use special transport rolls for the wire. Aluminum is a very soft material, so a lack of protection can lead to breaking and bending.

· Using the wrong shielding gas is another common issue. Make sure that the dew point of your shielding gas is adequate. Most of the time, Argon 4.6 is used because it comes with a 99.996 purity. The dew point is -62 degrees Celsius.

· Not checking the gas pipe for condensation is another concern. If you allow the humidity levels to be too high, then hydrocarbon gets into your weld seam and damages your entire weld. Checking the gas pipes for condensation will help prevent that!

Safety Considerations for Aluminum Welding

If you’re performing any type of aluminum welding, always wear protective equipment. A respirator, gloves, overalls, goggles, or a welding mask are necessary. You should also have leather shoes or boots to protect your feet.

It also helps if you have light-blocking curtains since they will help minimize exposure to molten metal and light-related injuries. Regular cleanup of the weld and welding system is important so that you can eliminate any risks.

Conclusion

So, is it possible to weld aluminum with flux core? Yes, you can, but it’s far from the ideal option due to the complications brought by aluminum’s composition. If you want to weld aluminum, gas tungsten arc welding is the most appropriate method to consider. Alternatively, you could also opt for laser beam welding, electron beam or resistance welding as well!