Even for the most experienced welders, aluminum welding can be a challenge. Aluminum welding requires different techniques and processes than welding steel. It is important to understand these differences in order to complete successful welds and work on a variety of different projects.
While welding aluminum can be difficult, it is a skill that can be developed with the right knowledge and practices. Read on to learn everything about welding aluminum from the different types of welding to general tips for success.
Why Aluminum Welding is Difficult
Aluminum is a common type of metal used in manufacturing. It’s non-corrosive, lightweight, and pleasing to the eye, making it an ideal material choice for a wide variety of welds. However, the same properties that make aluminum desirable can also make it difficult to work with.
Why is aluminum so difficult to weld? This material is soft, highly sensitive and isolated by a tough oxidized layer. When molten, aluminum is susceptible to contamination, which can lead to porous, weak welds.
Aluminum and its alloys have a great affinity for oxygen. Pure aluminum melts at 650°C(1200°F) and the oxide that protects the metal melts at 2037°C(3700°F). Since the oxide melts at a temperature about 1370°C (2500°F) higher than the aluminum itself, the oxide must must be cleaned of metal before welding can be started.
Because aluminum has a higher thermal conductivity and a low melting point, it has a smaller processing window than other metals and can easily burn through. This, combined with the difficulty of viewing weld progress and quality, can make aluminum difficult to work with.
In sum, here are some of the most common factors that make aluminum challenging to weld:
- Oxidation: There is an aluminum oxide layer on aluminum, which melts at a significantly higher temperature than aluminum. Melting through this layer requires high heat, but the welder must be careful not to burn holes in the aluminum underneath.
- Porousness: In a molten state, aluminum absorbs hydrogen the faster it heats up. This hydrogen separates out when the metal reverts to a solid form that can leave bubbles in the material, making the metal porous and weak.
- Impurities: Since aluminum is very sensitive, there are various ways in which it can be contaminated by dirt, air and water during the welding process. Aluminum can become contaminated with air reaching the weld from poor shielding or excessively long arcing. Oxygen can reduce the strength and ductility of aluminum and cause oxide to form in aluminum welds, affecting its appearance and making multipass welding difficult. Hydrogen can come from many sources, e.g. B. from moisture in electrode fluxes, moist air, moist welded joints and much more. For all of these reasons, it is important to thoroughly clean and properly store aluminum before welding.
- Thickness: When welding aluminum, different material thicknesses are used. Welders need to know how to avoid burning through thinner material while at the same time penetrating thick material enough to create a strong weld.
Welding aluminum certainly presents challenges, but it is not impossible to learn. Fortunately, there are tools and techniques out there that help in working with the unique properties of aluminum.
If you know how aluminum reacts and how to use these tools and techniques effectively, you are well on your way to mastering the art of aluminum welding.
The Best Way to Weld Aluminum
When welding aluminum, it is important to choose the right welding process. Many tools and methods are designed for welding steel, but aluminum requires its own technique and equipment.
Before starting the welding process, the welder must thoroughly clean the aluminum. As mentioned earlier, one of the challenges with aluminum is that it is more susceptible to contamination. Therefore, it is important to properly prepare the material.
Here are a few steps to follow:
- Use a solvent such as acetone or a mildly alkaline solution such as strong soap to remove oil, grease, and water vapor from the aluminum surface.
- Use a stainless steel wire brush (used exclusively on aluminum) to remove surface oxides. This can also be done with strong alkali or acid. Always make sure to rinse and completely dry the part before welding.
- Assemble the joint and cover it up if you don’t weld it right away. This prevents dirt or grit from contaminating the joint.
- Always keep your aluminum dry and stored at room temperature. It should be welded within a few days, and if it’s not, clean the joint again.
Safety is another important component when welding aluminum or other materials. Always make sure that you are wearing the correct protective equipment such as safety glasses, goggles, a welding helmet with the appropriate lens color number to protect your eyes, gloves and leather to protect yourself from metal sparks and splashes, the right shoes to protect your eyes Protecting your feet and having the right smoke ventilation to keep the sweat fumes away from your breathing zone.
Check out our welding guide to learn more.
Types of Aluminum Welding
If you’re wondering how to weld aluminum, it’s important to know that there are several welding processes that can be used:
- GTAW/TIG welding
- GMAW/MIG welding
Gas tungsten arc welding (GTAW), also known as tungsten inert gas welding (TIG), is one of the most popular welding processes for aluminum. This welding technique is widely used by automotive enthusiasts and welders for professional racing teams.
TIG requires constant current equipment with AC (alternating current) capabilities that uses 100 percent argon as the shielding gas. No mechanical wire feed is required, which can lead to feedability problems.
Rather, the welder will introduce the filler material into a puddle. This process is also very clean as the alternating current cleans the oxidized layer from the aluminum during welding. It also prevents aluminum from becoming contaminated throughout the process. For more information on this method, see What is TIG welding, and How To TIG weld? to learn more.
Tips for TIG welding:
- Choose the correct tungsten electrode or rod. The best choice for aluminum is usually a pure tungsten rod
- Take the time to prepare your aluminum by cleaning and preheating it
- Make sure that there is not too much argon flowing through the torch, which can lead to an irregular arc
- Use a heat sink to avoid warping
- When welding, keep the correct aluminum filler electrode or rod free of contamination and melt it with the base material to create a constant puddle of weld
Gas metal arc welding (GMAW), commonly referred to as metal inert gas welding (MIG), is another common method for aluminum welding.
This type of welding typically has faster travel speeds and higher deposition rates than TIG welding, which affects the weld quality. However, a mechanical wire feed system is used, which means the welder may have to use a spool torch or push-pull torch to make wire feeding possible
In order to combat the risk of porosity in aluminum, the base material, and the filler rod must also be clean, moisture-free, and provided with an excellent protective gas cover, typically containing pure argon. For more information on this method, see What is MIG welding, and How to MIG weld? to learn more.
Tips for MIG welding:
- Prepare your push-pull wire feeder
- Clean your aluminum, remove any oxides and file the edges to be joined
- Avoid pulling while welding. Instead, push at a 10 to 15 degree angle
- Use straight bead with multiple passes to improve the overall appearance of the weld and avoid mistakes
- Use a heat sink that will absorb extra heat and allow you to weld more slowly
Other Ways to Weld Aluminum
While MIG and TIG are commonly used methods of welding aluminum, there are several other types of welding that can be used:
- Laser beam and electron beam welding: Beam welding techniques are commonly used for aluminum. Electron beam welding has a very precise heat-affected zone that can be easily controlled, which makes it ideal for aluminum. Laser beam welding is ideal for quick, clean weld seams and is ideal for materials that are sensitive to cracks such as aluminum.
- Resistance welding: This type of welding joins metals by applying pressure and passing a current through the metal areas to be joined. It can be used for aluminum, but the welder must be aware of the high thermal and electrical conductivity of this metal.
- Shielded metal arc welding (SMAW): This type of welding can be used to weld aluminum, but it is not recommended. In some cases, it is used to repair aluminum castings using a constant current device with an aluminum electrode using the electrode’s positive polarity.
So what types of welding should be avoided with aluminum? In general, any type of welding that uses flux is not ideal for aluminum as it can lead to porosity. These include flux core arc welding (FCAW), submerged arc welding and rod welding.
Things to Avoid When Welding Aluminum
Now that we’ve looked at different ways that aluminum can be welded, let’s discuss some common mistakes that should be avoided.
- Taking a ‘one-size-fits-all’ approach: When it comes to aluminum welding, the welder has to take a completely different approach than when welding a material like steel. It is important for the welder not to base his technology on experience with other metals or materials, since aluminum is very unique and can be dangerous if handled improperly.
- Not wearing the proper PPE: Speaking of dangers, welding aluminum or other materials is inherently dangerous. It is important for welders to always wear the correct personal protective equipment (PPE) and to study safety procedures and best practices. This is the key to a long and successful career in the industry.
- Failing to prepare: Preparation is critical for both the welder and the material being welded. Always make sure to properly clean and properly store your aluminum before you start welding. Also, make sure you prepare for it by studying the art of aluminum welding and learning about the craft. Never jump into anything until you are adequately prepared.
- Ignoring minor details: The most successful welders will tell you that detail is everything. In this industry, the slightest misstep can lead to a complicated mistake, especially when welding aluminum. Always pay attention to every detail and double-check your work as this will benefit your clients and your career in the long run.
- Not being patient: Learning to weld aluminum takes time. Keep practicing and sticking to it, your hard work and perseverance will pay off in the end!
Benefits of Using Aluminum
Since welding aluminum is challenging, you may be wondering, “Why use aluminum at all?”
The use of aluminum as a structural material is relatively new. In fact, the Washington Monument, which was completed in 1884, was covered with 100 ounces. Pyramid made of pure aluminum because it was considered a precious metal. At the time, aluminum was not widely used.
It was not until 1886 that aluminum became available in commercial quantities due to the discovery of the electrolytic process to obtain pure aluminum from alumina. Since then, welders around the world have recognized their unique properties and have used them in many applications such as: in passenger cars, trucks, caravans, railroad cars, airplanes, cookware and even marine equipment.
While aluminum can be difficult to work with, this material offers several key benefits:
- Lightweight: Compared to steel, aluminum has a better strength-to-weight ratio and becomes more solid than brittle as the temperature drops. This makes it a great choice for projects that require strength but still need to remain lightweight.
- Electricity & heat: Aluminum conducts electricity and heat almost as well as copper.
- Non-corrosive: While oxidation creates challenges during the welding process, this quality is also a benefit to using aluminum, as it is non-corrosive.
- Recyclable: Aluminum is cost-efficient and recyclable, which is one of the reasons it has become increasingly popular.
- Appearance: Aluminum effectively absorbs paint and sealant, so it is often chosen for its cosmetic qualities.
As aluminum welding becomes more popular, it is important for today’s welders to have the skills to work with this material. This often requires formal, hands-on training.
Welding aluminum: Pick the right tungsten electrode or rod, the best choice for aluminum is typically a pure tungsten rod. Take the time to prepare your aluminum by cleaning and preheating it. Ensure there is not too much argon flow at the torch, which can cause an irregular arc. To prevent warping, use a heat sink.
Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is one of the most popular welding processes chosen for aluminum.
Simply put, aluminum is difficult to weld because it is a soft, highly sensitive metal insulated by a tougher oxidized layer. Aluminum is highly susceptible to impurities in its molten state, increasing the risk of ending up with weak, porous welds.
One of the most popular welding processes for aluminum is gas tungsten arc welding (GTAW), otherwise known as tungsten inert gas (TIG) welding. GTAW is a great process for aluminum because it does not require mechanical wire feeding, which can create feedability issues.
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