Similar to steel, aluminum can be produced with many different physical and chemical properties. While some grades react well to welding, others require more expertise or should not be welded at all. With a variety of combinations at hand, which type of aluminum is the best choice for your welding process?
The Challenges of Aluminum
The first thing to note about aluminum is that it is generally more difficult to work with than carbon or stainless steel. Aluminum behaves much differently during the welding process and is known to be finicky.
When welding aluminum, there are a number of challenges that are often presented, including:
- Parts may crack if they are squared after welding due to heat distortion
- Less malleable than steel
- Easily affected by heat
- Requires more skill to weld
Since aluminum is relatively expensive, there is the potential for extra costs when specifying a grade with low weldability. However, aluminum is still a top choice material for many engineers because it is light-weight, which makes it ideal for many applications. Aluminum is also a nonferrous metal, which means it’s less corrosive and won’t easily rust.
Our advice when deciding on a specific grade: use one that is commonly produced for maximum cost-effectiveness. If there’s a lot of supply in the market, you’ll receive a much better price.
The Best Aluminum Grades for Welding
When buying aluminum, you’re actually buying an aluminum alloy, meaning that there are other metals present in the compound. Those other metals give the aluminum properties that vary by grade. Aluminum grades are separated into series, beginning with 1XXX and ending with 7XXX. Generally, higher numbers mean a higher percentage of magnesium.
The series that react the best to welding are 5XXX and 6XXX. One common question we receive is whether 6061 aluminum is weldable. The answer is yes—we most often use 5052 or 6061 aluminum. These alloys are the most forgiving. Since they have a lower level of magnesium and aren’t as thick, they are less likely to crack. These two metals are also very common, so availability and price should be steady.
What’s the difference between 5XXX and 6XXX aluminum?
- 5XXX: This series is useful if you need to weld high-strength material for structural and heavy-duty applications, such as shipbuilding. However, due to the high amounts of magnesium, they should not be welded with 4XXX filler metal.
- 6XXX: This series includes alloys with magnesium and silicon. 6XXX is used most widely for welding fabrications and is strong enough for buildings and other structures. It also responds well to heat treatment.
Grades That Are OK, But Not Optimal
Depending on your project, these aluminum alloys may also be suitable:
- 1XXX: This series of alloys is 99% aluminum , which is as close to pure as you can get. It’s not very strong, but it is highly resistant to corrosion. In other words, it is not suitable to hold up a building, but it will withstand chemical environments.
- 3XXX: This series includes manganese. It is malleable and easy to weld, and is often featured in heat-related applications, such as cookware, heat exchangers in vehicles, and power plants. However, this series is not known for its strength, so it should not be used in structural applications.
- 4XXX: This series is highly weldable, but is more often used as filler materials for other grades.
Grades to Stay Away From
- 7XXX: This series should be handled by highly experienced welders due to its poor reaction to welding. In fact, you may want to avoid welding 7000 series aluminum all together. Hot cracking and stress corrosion are common issues. Specifically, 7075 alloys are great for marine applications because of their low density and steel-like strength. However, they’re also temperamental and expensive, making them a poor investment for welding.
- 2XXX: This series also reacts poorly to welding, so try to avoid specifying these. While the 2024 alloy is very common and immensely strong, it’s extremely crack-sensitive.
Talk to Your Vendor
5XXX and 6XXX series aluminum alloys are the best for welding overall. Remember that your project and application will ultimately determine which grade will work best. With so many aluminum types to choose from, it’s best to partner with a vendor that can tell you more information about each series.
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