Aluminum welding for stable connections

Challenge of aluminum welding

Aluminum alloys are among the most commonly used construction materials in the metal sector, alongside steel. Their low weight, only about one-third that of steel, makes them particularly attractive for lightweight construction, for example in the automotive or aviation industries. However, welding aluminum poses a particular challenge: the surface is covered with a stable oxide layer that has a significantly higher melting point than the base material underneath. This combination complicates the welding process and requires precise process control and experience to achieve consistently high-quality results.

Interesting facts about aluminum

Pure aluminum (Al99.5) is not very strong. Adding other metals significantly increases its strength, allowing aluminum to be used in structures subject to high stress.

The protective oxide layer on aluminum can only be broken down using a positively polarized electrode, which works without any problems in MIG welding – in contrast to TIG welding, where this step is more technically demanding. Only inert shielding gases can be used for aluminum welding. Active gases would oxidize the melt and impair the quality of the weld seam. Particular attention must be paid to cleanliness: filler materials, workpiece surfaces, and shielding gas lines must be free of contamination. This is because aluminum reacts strongly with hydrogen, which quickly leads to porosity in the weld metal.

Aluminum alloys at a glance

The most important components of aluminum alloys and their properties are:

Magnesium (Mg)
0.3–7% higher strength, finer grain size
Manganese (Mn)
0.3–1.2% better corrosion resistance, higher strength
Copper (Cu)
roughly 5% higher strength, lower corrosion resistance, important for hardening capacity
Silicon (Si)
12% for casting, reduces the melting point to 577°C, however with coarse grains