Process-safe spot welding of aluminium in the industrial sector
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Requirements of aluminium spot welding
Reliable industrial spot welding of aluminium is an ambitious venture
The reproducible, i.e. process-safe resistance spot welding of different aluminium alloys is a technologically very demanding task, especially under the condition, that such welding processes are carried out with the lowest possible energy input - i.e. currents.
In contrast to spot welding of steels, for example, far more physical variables and influencing variables have to be considered when welding aluminium. In this case, the material composition of the electrodes is of great importance, as are the physical properties of the aluminium material to be welded itself.
Aluminium materials occur in numerous alloy forms and the respective electrophysical properties of these alloys increase accordingly. Even different storage times of aluminium sheets influence the electrophysical properties of individual batches.
In contrast to steel construction, e.g. during spot welding of car body components made of high-alloy steels in the automotive industry, spot welding of aluminium with the usual copper electrode caps poses the fundamental problem of alloying the aluminium to the copper caps - aluminium oxides are formed, which immediately influence the electrical properties of the contact surfaces on the electrode and aluminium sheet.
In addition, higher current strengths must generally be used in the aluminium spot welding process than in the spot welding of high-alloy steel grades, for example. This in turn requires larger power sections in the current sources and more powerful transformers in the spot welding guns.
In the picture: Standard electrode copper caps alloyed under heavy load. Clear layers of aluminium oxide have formed. Welding spots set with such caps do not provide process-safe quality.