Aluminum is a light, strong metal that we encounter everywhere in our everyday lives, in everything from bicycle frames to aeronautical structures and kitchen utensils. Its versatility and durability make it a desirable choice for many industrial functions.
Despite the many advantages of the material, welding aluminum presents several challenges. Unlike other metals, aluminum requires special attention and the application of unique techniques to achieve strong, durable welds.
Keep reading as our industrial welding professionals take you through the intricacies of aluminum welding.
Why learn how to weld aluminum properly?
Despite its lightness, aluminum is recognized for being strong and resistant to corrosion. To take full advantage of these qualities, aluminum welding must be carried out with precision and expertise.
Ensuring safe, long-lasting welds
Welding does more than just join two pieces of aluminum; it guarantees the strength of the entire aluminum structure. A poorly executed weld can compromise the safety of an installation or piece of equipment, with potentially disastrous consequences, particularly in high-performance fields like aeronautics or construction. A quality weld impacts the durability of the entire assembly, and can help avoid premature maintenance or replacement costs.
Challenges specific to aluminum welding
Unlike other metals, aluminum has special characteristics and a delicate welding process is required to make successful aluminum welds. Aluminum has high thermal conductivity, meaning that it dissipates heat quickly, making perfect temperature control absolutely necessary during welding.
In addition, an oxide layer forms quickly on the surface of an aluminum weld, and this can hinder the welding process if not managed correctly. These and other challenges mean that it is necessary to have in-depth knowledge and use the right techniques to weld aluminum safely and efficiently.
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Before beginning the aluminum welding process, it is vital to prepare the surface of the material. This step is often overlooked, but it is essential if you want to make a strong, durable aluminum weld.
Cleaning and degreasing surfaces
Although aluminum is naturally resistant to corrosion, impurities and contaminants can accumulate on its surface. Before any welding operation, make sure that the area to be welded is cleaned and degreased using wire brushes, solvents or specific degreasers. This step removes any traces of oil, grease or dirt that could compromise the quality of the weld.
The aluminum oxide layer that forms naturally on the surface of the metal has a much higher melting point than the aluminum itself. If this layer is not properly treated before welding, it can hinder fusion and lead to weak or porous welds. The surface must be prepared either by mechanical brushing or by using chemical solutions to achieve a clean, solid weld.
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Tips to avoid oxygen and humidity contamination
Moisture and oxygen are the enemies of many types of welding, and aluminum is no exception. Hydrogen from humidity can cause porosity in the weld, while oxygen can cause undesirable oxidation. To avoid these problems:
- Always store materials in a dry, moisture-free place
- Use shielding gases, such as argon or an argon/helium blend, to create a protective atmosphere during welding
- Store all equipment and consumables (such as welding rods or wires) in a dry place.
Aluminum welding processes
Because of its unique properties, aluminum requires the use of specific welding processes to guarantee strong, durable joints.
TIG welding uses a non-consumable tungsten electrode to produce the arc and an inert gas, usually argon, to protect the welding zone from atmospheric contaminants. This process is precise, applicable to thin welds, and also good for producing high-quality welds with minimal distortion.
MIG welding uses a consumable electrode in wire form, which serves as both filler material and conductor for the arc. Inert gas, usually argon or a blend of argon and helium, protects the weld. This process is fast, versatile and good for welding thicker aluminum.
Why the term MAG is not used for aluminum
Although MAG welding is similar to MIG welding (MIG/MAG welding), it uses a slightly oxidizing gas. However, for aluminum, it is necessary to use an inert gas to avoid oxidation, hence the term MIG.
Plasma and laser welding
Plasma welding involves creating an electric arc between an electrode and the workpiece, while laser welding uses a concentrated laser beam as a heat source. Both methods are recognized for their ability to produce deep welds with a reduced heat-affected zone. They are ideal for applications requiring high precision and speed, such as in the aerospace or automotive industries.
Choosing the right shielding gas
The main role of the shielding gas is to protect the welding zone from atmospheric contaminants such as oxygen, nitrogen and hydrogen. These contaminants can cause defects in the weld, such as porosity or oxidation. By using the right shielding gas, you can achieve a clean, inclusion-free weld with excellent mechanical integrity.
Pure argon vs. argon/helium blends
Pure argon is commonly used for aluminum welding because of its ability to provide a stable arc and minimize oxide formation. However, for certain applications, particularly for thicker aluminum or where deeper penetration is required, a blend of argon and helium may be a better choice. Helium raises the arc temperature, resulting in better penetration and faster welding speed.
Tips for avoiding hydrogen porosity
Porosity is one of the most common defects in aluminum welding. It is mainly caused by the presence of hydrogen, which can come from moisture on the aluminum surface or from the surrounding atmosphere. To avoid this problem:
- Make sure the aluminum surface is clean and dry before welding
- Use high-purity shielding gas, with a minimum specification of 99.5%
- Avoid welding in damp or wet areas
- Check your equipment regularly to ensure there are no leaks or other sources of moisture.
Tips for successful aluminum welding
Aluminum welding, while commonplace, presents unique challenges that require special attention if you want to obtain optimal results. Here are some practical tips to ensure that your aluminum welding is not only solid, but also looks good.
Aluminum has a relatively low melting point, which means it can be easily damaged or deformed by excessive heat. You need to monitor and control the temperature when welding.
Make sure the aluminum is preheated to an appropriate temperature before you start, usually between 100°C and 200°C (212°F and 392°F), depending on alloy and thickness. This helps reduce the risk of warping and cracking.
Managing welding speed
The speed at which you weld can influence the quality of the weld. Welding too quickly can result in insufficient penetration, while welding too slowly can cause overheating and distortion.
Find a balance according to the thickness of the material and the type of welding you’re doing. Remember that aluminum conducts heat quickly, which can affect the speed at which you need to move forward.
Tips to avoid common defects
- Porosity: As mentioned above, hydrogen is the main cause of porosity in aluminum welds. Make sure surfaces are clean and dry, and use an appropriate shielding gas.
- Cracking: Cracking can occur if aluminum is overstressed during welding. Use appropriate joint preparation techniques and avoid over-tightening.
- Deformation: To minimize deformation, try to weld in several passes rather than one thick pass. This distributes the heat more evenly.
- Oxidation: Aluminum quickly forms a layer of oxide on its surface. Although this layer is protective, it can interfere with welding. Use a stainless steel brush to brush the area just before welding.
HARtech: an aluminum welding company in Quebec
Aluminum welding is an intricate skill that is widely used in many industrial sectors. Understanding the appropriate grades and techniques is the key to achieving optimum results, and there’s no substitute for the expertise of a professional welder when it comes time to get the welding job done.
HARtech has been a leader in the field of industrial welding for many years. We have mastered the art and science of welding all types of metal, including aluminum. With a team of highly qualified experts, state-of-the-art equipment and a passion for excellence, HARtech is your trusted partner for all your welding needs.
If you have a complex project that requires meticulous precision, contact us today!