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Differences between welding aluminium and steel

December 22, 2020

Welding aluminium will present unique challenges compared to welding steel – particularly in terms of the crack sensitivity and the chemistry involved. Most welders’ start by learning how to weld steel and, depending on your work and experience, aluminium welding may be a valuable skill to learn. 

Although welding aluminium is similar to welding steel, the process is a little trickier. Welding aluminium requires special procedures to ensure the metal is treated correctly, such as selecting the right filler material and utilizing the proper welding techniques. Here is a look at the differences between welding aluminium and steel.


Even though metal-inert gas welding is a common technique used for welding both steel and aluminium, we recommend that when welding aluminium to only use straight argon rather than a mixture of argon and carbon dioxide. Thicker aluminium welds can be welded with a mixture of helium and argon. 

Many techniques that work well with welding steel will not work with aluminium welding – for example, oxy-acetylene torch welding will lead to defects in the weld due to the aluminium absorbing the hydrogen gas being utilised. 

The following are common techniques used for welding aluminium:

  • Laser Beam Welding and Electron Beam Welding
  • Resistance Welding


Aluminium welds solidify much faster than steel because of its higher rate of heat transfer – about six times greater than steel. Aluminium is also much lighter and less dense than steel, and has a lower melting point. It is also coated in a thin skin of aluminium oxide – which needs to be removed in order to get good welding results.


When welding steel, many welders use the colour of the heated metal to track their progress – this approach is a little problematic when welding aluminium as aluminium does not show its colour quite as well. Also, the molten metal looks silvery and less obvious. You could end up with a puddle of liquid metal if you are not careful when welding aluminium.


Compared to steel, pre-treatment before welding aluminium is much more crucial. All metal types require individualized treatment, for example, high-carbon steel requires heat-treatment after welding, whereas mild and low-carbon steels, by contrast, are much simpler to handle before welding. Aluminium, on the other hand, should be cleaned with non-chlorinated solvents and scrubbed with a stainless steel wire brush to remove the above-mentioned oxides. However, both metals generally require the edges to be cleaned.

The team at Rapid Fab are experts in the welding and fabrication industry and are happy to assist with the best practices of welding steel and welding aluminium. Contact the team at 07 5529 2622 to discuss anything and everything to do with welding.