Like any other metal, aluminium can be successfully welded to form a variety of joins and shapes. However, unlike other metals, aluminium is uniquely tricky to work with. This lightweight yet durable material has several properties that make welding aluminium a little complicated. Therefore, the right equipment and, especially, the right set of skills are needed to perform good, clean, strong aluminium welds. Let’s take a look at why aluminium welding can be so difficult.
Aluminium has a layer of aluminium oxide on top, which gives the metal its hardness. However, this aluminium oxide layer melts at far higher temperatures than the aluminium underneath it. This means that in order to weld aluminium, one must melt through the aluminium oxide top layer without burning holes through the softer aluminium underneath. This takes considerable skill, knowledge and the right set of tools to weld aluminium correctly and not end up burning it.
The more porous a metal is, the weaker it becomes. Aluminium is prone to becoming porous when melting because it absorbs a lot of hydrogen as it heats up. The problem is that when it cools down again, the hydrogen is then expelled from the material, leaving bubbles in the hardened metal. These bubbles not only look ugly, but they also cause significant weakening of the metal. This can be avoided by using gas shielding during welding.
Aluminium is highly sensitive to contamination during the welding process, which is why it is so important to use proper inert gas shielding when welding, which will protect the metal from being ingressed by oxygen or hydrogen, among other contaminants.
Oxygen and hydrogen can not only ruin the appearance of the metal and weaken it, but it can also create complications when attempting multi-pass welding. Other contaminants such as dirt can also get into the metal during melting and can significantly weaken it.
Before welding aluminium, it should be thoroughly cleaned with acetone and/or soap to ensure that no contaminants are present during the weld.