Otis Singleton
Welding aluminium with an electric welder can be challenging due to its high thermal conductivity, low melting point, and chemical composition. Aluminium is also sensitive to oxygen, which can cause contamination during the welding process. To successfully weld aluminium, it is crucial to use the right welding technique, such as MIG, TIG, or stick welding, and prepare the aluminium by cleaning and preheating it. Additionally, the choice of electrode and filler material is critical to achieving successful results. The ideal location for welding aluminium is outdoors, where there is better ventilation, and it is important to take safety precautions, such as wearing welding gloves, aprons, helmets, and respirators.
| Characteristics | Values |
|---|---|
| Type of welding | MIG, TIG, Stick, Laser beam, Electron beam, Resistance, Shielded metal arc welding |
| Ideal location | Outdoors |
| Welding equipment | DC stick welder, Standard DCEP polarity, Stainless steel brush, Argon shielding gas, Tungsten electrode, Heat sink, Spool gun, Push-pull gun, Filler metal wire, Alternating current |
| Pre-welding preparation | Clean the base material, Remove aluminium oxide, Remove hydrocarbon contamination, Preheat aluminium |
| Welding technique | Avoid pulling, Push at 10-15 degree angle, Use multiple-pass straight beads, Keep a short arc, Move arc quickly, Use pulsed GMAW, Push the gun away from the weld puddle, Hot and fast |
| Post-welding | Ample post-weld cleanup |
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What You'll Learn
- Preheat the aluminium to avoid weld cracking, but don't exceed 230°F/250°F
- Use a pure tungsten rod electrode and a stainless steel brush to clean the aluminium
- Use a DC stick welder with DCEP polarity, and set the machine to 85 amps
- Avoid warping by using a heat sink, and weld at a 10-15-degree angle
- MIG welding is easier than TIG welding, but TIG welds look better
Preheat the aluminium to avoid weld cracking, but don't exceed 230°F/250°F
Aluminium is prone to cracking during welding due to its high thermal conductivity and low melting point. To prevent this, welders often preheat the metal before beginning the weld. Preheating the aluminium helps to “even out” the thermal expansion and contraction it experiences during the welding process. This also helps to prevent warping.
However, it is important not to preheat aluminium above 230°F-250°F. This is because exceeding these temperatures can negatively affect the metal's mechanical properties. Additionally, aluminium has a strong reaction to oxygen. At high temperatures, it can easily absorb hydrogen, which can cause the metal to become porous and weak.
To preheat aluminium, welders often use an acetylene torch. Before preheating, it is important to clean the aluminium thoroughly and remove any oxide and hydrocarbon contamination from oils or cutting solvents. This can be done using a stainless-steel bristle wire brush or solvents and etching solutions. When using a brush, only brush in one direction, and do not use too much force to avoid embedding oxides further into the metal.
Preheating aluminium is especially important when welding a thick piece of aluminium to a thin piece. In this case, if cold lapping occurs, run-on and run-off tabs can be used.
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Use a pure tungsten rod electrode and a stainless steel brush to clean the aluminium
When welding aluminium, it's important to remember that you're not working with steel. Aluminium is not a joy to weld, and the arc reacts violently, expelling a lot of spatter. Before you begin, ensure that all flammable and combustible materials are removed from the area.
To weld aluminium, it is crucial to clean the base material and remove any aluminium oxide and hydrocarbon contamination from oils or cutting solvents. This oxide layer forms when aluminium is exposed to air, protecting it from rust but making it difficult to bond with. To clean the aluminium, use a pure tungsten rod electrode and a stainless steel brush. It is important to note that this brush should be dedicated to aluminium-only work, as using a brush previously used on steel can contaminate the aluminium. When using the brush, scrub in one direction with gentle strokes, as scrubbing back and forth or brushing too roughly can cause the oxide to go deeper into the aluminium.
The choice of electrode is critical when welding aluminium. The ideal electrode for aluminium is typically a pure tungsten rod. However, when using stick welding, special stick electrodes designed for aluminium are required. These rods have a high affinity for moisture, so they must be stored properly to avoid becoming damp and useless.
To summarise, when preparing to weld aluminium, it is essential to clean the surface with a dedicated stainless steel brush and select the right tungsten electrode, typically a pure tungsten rod.
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Use a DC stick welder with DCEP polarity, and set the machine to 85 amps
Welding aluminium can be challenging, and it is recommended to use a DC stick welder with DCEP polarity. This is because aluminium has a high thermal conductivity and a low melting point, which can lead to burn-through.
To set up your welder, start by setting the machine to 85 amps. You will also need to ensure you have the correct electrode, as this is critical when welding aluminium. You should use a pure tungsten rod, or a special aluminium stick electrode. These rods are expensive and have an extreme affinity for moisture, so be sure to store them correctly.
Before welding, you must clean the aluminium. Use a stainless-steel brush dedicated for aluminium-only work, as using a brush used on steel can contaminate the aluminium. Scrub in one direction only, as scrubbing back and forth can cause the oxide to go deeper into the metal. You should also preheat the aluminium, but not above 230-250 degrees Fahrenheit, to avoid negatively affecting its mechanical properties.
When welding, be aware that aluminium requires more power than steel of the same thickness. You must be able to vary the amperage output to get the heat just right. Keep a short arc and move it quickly, as the weld pool sets faster than usual.
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Avoid warping by using a heat sink, and weld at a 10-15-degree angle
Welding aluminium can be challenging due to its high thermal conductivity and low melting point. Warping is a common issue when welding aluminium, and it occurs due to uneven expansion and contraction of the metal when heated and cooled during the welding process. Thin metals are particularly prone to warping because they heat up quickly and have less mass to dissipate the heat.
To avoid warping, it is crucial to control the heat input and manage the cooling process. One effective method to achieve this is by using a heat sink. A heat sink is a copper or aluminium plate or bar that helps pull heat away from the weld area and dissipate it evenly, preventing overheating and reducing the likelihood of distortion. When using a heat sink, it is important to clamp it directly behind the piece being welded to ensure its effectiveness.
In addition to using a heat sink, welding at a 10-degree to 15-degree angle can also help prevent warping. This technique, known as pushing, involves feeding the filler material into a puddle while pushing at the recommended angle. By pushing at a slight angle, you can control the heat input and reduce the risk of warping. It is important to note that pulling while welding should be avoided as it can contribute to warping.
By combining the use of a heat sink and welding at the recommended angle, you can effectively manage the heat input and cooling process, minimising the chances of warping and ensuring high-quality welds.
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MIG welding is easier than TIG welding, but TIG welds look better
Welding aluminium can be done through various methods, including MIG, TIG, stick, laser beam, electron beam, resistance, and shielded metal arc welding. However, the debate between MIG and TIG welding is prevalent, with each having its pros and cons.
MIG (Metal Inert Gas) welding is a straightforward process that is relatively easy to learn and master, making it ideal for beginners. It uses a feed wire that constantly moves through the gun to create a spark, then melts to form the weld. This process is automated, reducing the training time and effort required. MIG welding is faster and more efficient, making it suitable for large industrial operations that require high production rates. It also has high deposition rates, making it excellent for welding thicker materials. Additionally, it doesn't require the use of filler rods or a tungsten electrode, simplifying the process.
On the other hand, TIG (Tungsten Inert Gas) welding is a more specialized technique that requires higher skill and experience. It uses long rods to fuse two metals directly together and offers greater precision and control, making it better for thin metals and technical projects. TIG welding generally produces cleaner and more aesthetically pleasing welds, achieving excellent fusion and superior results when performed by an experienced welder. It is also more versatile, allowing welders to work at difficult angles using the foot pedal.
While MIG welding is easier to learn and faster, TIG welding provides higher-quality welds with better precision and control. The choice between the two depends on the specific project requirements, such as the thickness of the material, the desired aesthetics, and the level of precision needed.
To weld aluminium with an electric welder, it is crucial to follow specific steps and considerations. Firstly, use a stainless steel brush dedicated only for aluminium work to avoid contamination. When welding, use a pure tungsten electrode or rod, and ensure the aluminium is cleaned and preheated. Additionally, use a heat sink to prevent warping and weld at a slight push angle. Finally, ensure proper shielding gas coverage, typically using pure argon, to protect the weld from contamination.
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Frequently asked questions
MIG, TIG, and stick welding are the most common types of welding used for aluminium.
MIG welding is faster and easier than TIG welding, but the welds are not as aesthetically pleasing. It is also suitable for smaller, more detailed projects as it operates at lower temperatures.
TIG welding produces superior results and excellent fusion, but it is more challenging and requires an experienced welder.
Stick welding aluminium is more complex and less attractive than other methods. It requires a trained hand and very high welding speed. Preheating the aluminium can help improve puddle fluidity and reduce excessive heat dissipation, but it should not exceed 230-250 degrees Fahrenheit to avoid negatively affecting the aluminium's mechanical properties.
