McKean’s Proper Aluminium Welding Service

Blog | November 8th, 2022

Aluminium is the ultimate material to use when it comes to lowering weight while attaining stability. Aluminium can be found in the frames of bicycles and motorcycles, trailers for trucks, profiles of rail cars, and even materials used in space flight. In addition, an aluminium seam that has been skilfully welded together is a real show-stopper.

Aluminium has established itself as an essential component in modern manufacturing thanks to the favourable combination of its lightweight and high strength. There are several challenging things to consider besides all of the benefits when it comes to processing this metal. Those who inadvertently burned a hole in an aluminium sheet will understand what we are discussing here. Aluminium welding demands specialised training and much prior experience. You can learn more about how to correctly weld aluminium and what factors should be considered by reading more in this blog.

Difficulty in Welding Aluminium

One feature of aluminium is responsible for the difficulty associated with welding this metal: as soon as aluminium is exposed to the surrounding air, a wafer-thin coating of aluminium oxide is formed on the surface of the aluminium. In addition, this layer is responsible for giving the metal its characteristic silvery-grey colouration. However, this process also renders the aluminium resistant to corrosion when exposed to water, oxygen, and various chemicals. In a sense, it acts as a shield for the metal. This protection needs to be actually “cracked” first because, much like a solid suit of armour, the oxide layer stops the arc and the weld pool from connecting and so cannot be bypassed.

The melting point of the oxide layer is 2050 degrees Celsius, while the melting point of aluminium itself is about 660 ° C. If you wanted to break the oxide layer using welding by itself, you would need to apply a temperature three times greater than the surface. Because of the large amount of energy that is being applied, there is a significant possibility that the aluminium may disintegrate as soon as the oxide layer is breached. As a result, it is necessary to prepare aluminium for the welding process by removing the oxide layer that it naturally possesses on its surface.

Proper Preparation is Key

Before reaching the oxide layer, any dirt, grease, or oil must be removed. A clean workpiece surface is essential for aluminium welding. After removing all grease lubrication and residue, remove the aluminium oxide layer. Depending on the ambient circumstances, you may need to repeat the preparation process many times. Black, sooty welding remnants indicate gas, base material, or welding wire impurities.

Aluminium welding requires cleanliness by welding with an alternating current. Where positive and negative half-waves alternate, the oxide layer can also be broken up. A positive half-wave breaks the oxide layer. Negative half-wave welding achieves penetration, recooling the electrode. When welding alternating current, you must also weld a ball on the front of the electrode, the calotte. With this, the molten oxide may be pushed forwards like clods to avoid the weld seam. Preheating the workpiece is recommended for welding aluminium sheets thicker than 10 mm. Without preheating, too much heat would escape during welding, making seam formation impossible.

Selecting the Right Welding Torch

Aluminium may be welded using various methods, including TIG, MIG, and plasma. TIG welding using alternating current is often utilised for thinner sheets. TIG welding is very effective for butt joints. For example, if you wish to join two 2 mm thick sheets of aluminium, you must ensure that the back edge is fractured. Only then will there be a beautiful root, adequate wetting of the weld metal, and a good weld. Thicker sheets are best treated with MIG welding since these torches can produce a faster melting rate through the wire. MIG torches are ideal for fillet welds because they inject the welding filler appropriately. The plasma welding procedure with the direct current has the benefit of introducing heat into the workpiece in a targeted manner, but it is a difficult operation.

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