Frames of bicycles or motorcycles, trailers for trucks, profiles of rail vehicles, materials in space travel – aluminum is the material when it comes to reducing weight and still achieving stability. In addition, a beautifully welded aluminum seam is a real eye-catcher.
Thanks to its low density and good strength, aluminum has become an integral part of modern production. In addition to all the advantages, there are also some tricky aspects when processing this metal.
Anyone who has ever accidentally burned a hole in an aluminum sheet knows what we are talking about. Welding aluminum requires special knowledge and skills. Read more in this blog about what is important for aluminum welding and how to properly weld aluminum.
Why Aluminum Welding Is Difficult?
Aluminum is a common type of metal used in fabrication. It’s non-corrosive, lightweight, and pleasing to the eye, making it an ideal choice of material for a wide variety of welds. However, the same traits that make aluminum desirable can also make it tricky to work with.
So why is aluminum so difficult to weld? This material is soft, highly sensitive, and is insulated by a tough oxidized layer. While in its molten state, aluminum is susceptible to impurities, which can lead to porous, weak welds.
Aluminum and its alloys have a great affinity for oxygen. Pure aluminum melts at 1,200°F (650°C), and the oxide that protects the metal melts at 3,700°F (2,037°C). Because the oxide melts at a temperature approximately 2,500°F (1,370°C) higher than the aluminum itself, the oxide must be cleaned from the metal before welding can begin.
Since aluminum has a higher thermal conductivity and low melting point, it has a smaller window of workability than other metals and can easily lead to burn through. This, in combination with it being harder to indicate weld progress and quality, can make aluminum a difficult material to work with.
How To Weld Aluminum?
Welding aluminum comes down to choosing the right welding process. Many tools and methods are designed for welding steel, but aluminum requires its own technique and equipment.
Before even beginning the welding process, the welder must clean the aluminum thoroughly. As mentioned previously, one of the challenges with aluminum is that it is more prone to impurities. Therefore, prepping the material correctly is key. Here are a few steps to follow:
- Use a solvent such as acetone or a mild alkaline solution like a strong soap to remove any oil, grease and water vapor from the aluminum’s surface.
- Use a stainless-steel wire brush (used exclusively for aluminum) to remove surface oxides. This can also be done with a strong alkaline or acid. Always be sure to rinse and fully dry the part before welding.
- Assemble the joint and cover it if you won’t be welding it immediately. This will prevent 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 critical component to welding aluminum or any material for that matter. Always ensure you wear the proper protective equipment such as goggles, safety glasses, a welding helmet with the appropriate lens shade number to protect your eyes, gloves, and leathers to protect yourself from metal sparks and splatters, the proper shoes to protect your feet and proper fume ventilation to keep the welding fumes away from your breathing zone.
Different Technique Use for 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
- SMAW welding
- Resistance welding
- Laser beam and electron beam welding
So what types of welding should be avoided with aluminum? In general, any type of welding that uses a flux is not ideal for aluminum, as it can result in porosity. These include flux-cored arc welding (FCAW), submerged arc welding, and stick welding.
Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is one of the most popular welding processes chosen for aluminum. This welding technique is often used by automotive enthusiasts and welders for professional racing teams.
GTAW requires constant current equipment with AC (alternating current) capabilities using 100 percent argon as a shielding gas. It does not require mechanical wire feeding, which has the potential to create feed ability issues.
Rather, the welder will feed the filler material into a puddle. This process is also very clean, as the alternating current cleans the oxidized layer off the aluminum as it welds. It also prevents aluminum from being contaminated throughout the process.
Tips for TIG welding:
- 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
- When welding, keep the proper aluminum filler electrode or rod free of contaminants and melt it with the base material to create a constant welding puddle
TIG Aluminum Welding Benefits
- One of the many advantages of TIG aluminum welding is it eliminates the requirement of flux. As a result, the welding is free from a source of corrosion.
- Welding can be done in any position. TIG welding also gives better visibility and high-speed welding can be performed.
- Pressure-tight joints can be got with very low distortion and high strength.
- GTAW is relatively easy to perform and it is a high-speed welding technique. It is one of the reasons that TIG is preferred over other fusion welding methods.
- TIG welding uses non-consumable electrodes and AC current. Argon or Helium is used as the inert shielding gas. If filler material is needed then it can be fed automatically or manually.
- Very thin aluminum (0.6 mm 0r 0.025 inches) can be welded but materials having thickness of 1 mm or more give good results.
Gas metal arc welding (GMAW), commonly referred to as metal inert gas (MIG) welding, is another common method used for aluminum welding.
This type of welding typically has faster travel speeds and higher deposition rates than TIG welding, affecting the weld quality. However, it does utilize a mechanical wire feeding system, which means the welder may have to use a spool gun or push-pull gun to make wire feeding possible
Additionally, in order to combat the risk of aluminum becoming porous, the base material and filler rod must be clean, free of moisture, and have excellent shielding gas coverage, typically pure argon content.
Tips for MIG welding:
- Prepare your push-pull wire feed
- Clean your aluminum, remove any oxide and file the edges that will be joined
- Avoid pulling while welding instead, push at a 10 degree to 15-degree angle
- Use multiple pass straight beads to improve the overall appearance of the weld and help to avoid defects
- Use a heat sink, which will absorb extra heat and allow you to weld slower
3. 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 great for aluminum. Laser beam welding is great for fast, clean welds and is ideal for materials sensitive to cracking, such as aluminum.
4. Resistance welding
This type of welding joins metals by applying pressure and passing a current through the metal areas being joined. It can be used for aluminum; however, the welder must be aware of the high thermal and electrical conductivity of this metal.
5. Shielded metal arc welding (SMAW)
This type of welding could be used to weld aluminum but is not recommended. In some cases, it is used to repair cast aluminum using constant current equipment with an aluminum electrode using electrode positive polarity.
Factor Affecting During Aluminum Welding
In sum, here are some of the most common factors that make aluminum challenging to weld:
- Oxidation: On top of aluminum sits an aluminum oxide layer, which melts at a significantly higher temperature than aluminum. Melting through this layer requires high heat, however, the welder must be careful to not burn holes in the aluminum underneath.
- Porousness: In its molten state, aluminum absorbs hydrogen quicker the more it heats up. This hydrogen separates out as the metal returns to a solid form, which can leave behind bubbles in the material, causing the metal to become porous and weak.
- Impurities: As aluminum is very sensitive, there are several ways it can become contaminated by dirt, air and water during the welding process. Aluminum can become contaminated by air that reaches the weld because of poor shielding or excessively long arcs. Oxygen can reduce aluminum’s strength, ductility and cause an oxide formation on aluminum welds, which affects its appearance and complicates multi pass welding. Hydrogen can come from many sources, such as moisture in electrode fluxes, humid air, damp weld joints and more. For all of these reasons, it’s important to clean aluminum thoroughly and store it correctly prior to welding.
- Thickness: Welding aluminum involves working with different material thicknesses. Welders must know how to avoid burning through thinner material while also penetrating thick material enough to create a strong weld.
While there are certainly challenges that come with welding aluminum, it’s not impossible to learn. Luckily, there are tools and techniques designed to help when working with aluminum’s unique properties.
By having knowledge of the way aluminum reacts and how to effectively use these tools and techniques, you’ll be well on your way to mastering the art of aluminum welding.
What Should You Avoid When Welding Aluminum?
Now that we’ve covered different methods that can be used to weld aluminum, let’s talk about some common mistakes to avoid.
- Taking a “one-size-fits-all” approach: When it comes to welding aluminum, the welder must take an entirely different approach than they would with a material like steel. It’s critical for the welder to not base their technique on experience they have with other metals or materials, as aluminum is very unique and can present dangers when not handled correctly.
- Not wearing the proper PPE: Speaking of dangers, welding aluminum or any kind of material is inherently dangerous. It’s important for welders to always wear the correct personal protective equipment (PPE) and educate themselves on safety procedures and best practices. This is key to a long, successful career in the industry.
- Failing to prepare: Preparation is key—both for the welder and the material being welded. Always be sure to properly clean your aluminum and store it correctly before beginning your weld. Additionally, make sure to prepare yourself by studying the art of aluminum welding and educating yourself on 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 smallest misstep can lead to a complicated error—especially with aluminum welding. Always pay attention to every detail and double check your work, as this will benefit your customers and your career in the long-run.
- Not being patient: Learning to weld aluminum takes time. Keep practicing and stick with it your hard work and persistence will pay off in the end!