Perché è difficile saldare l’alluminio? - Tecnista

The aluminum welding, as we have been able to face in our previous article, consists of crushing the aluminum oxide film (alumina) that determines a difference in fusion temperature. This disparity causes the melting of aluminum even before the oxide layer is cleaned.

This process can be carried out mechanically a few minutes before welding or through the use of the "decapante" function operated by TIG welders tig pulsed with square wave in alternating current. In simple words we can say that the transfer of the current current to the fusion alternates (wave) with the moment of cleaning. This occurs at a variable frequency in order to allow perfect welding on various types of thickness.

An important aspect is the "direction" of the arch. While in the direct current welding (DC) the negative pole is in the torch, in the alternating current welding (AC) is exactly the opposite. This to ensure that it is the material, under the alumina layer, in Bucarla "going" towards the torch electrode.
ATTENTION: In the case of TIG welding on aluminum with alternating current welding machine, the TIG torch must always be connected to the connector with symbol (-). It will be the welding machine to reverse the current in a predetermined manner.

Always talking about TIG welding in AC it is good to note a particular concerning the diameter of the tungsten electrodes.

About the type we have already spoken (Read our specific article on tungsten electrodes and related applications) So let's see the differences in amperage between the AC welding with pickling and without:

Electrode diameter Current (a) with pickling Current (A) without pickling
1,6 40-75 30-60
2,4 60-120 60-100
3,2 100-180 90-150
 4,0 170-230 150-200

The shape of the electrode tip in AC can also be rounded without prejudice the quality of the cord.
Some examples of anomalies on the irregular consumption of the tungsten electrode tip.

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