AC welding

Under AC welding means the welding process using alternating current (as opposed to DC welding ). It is used with light metals.

In AC welding , the electrode is both anode and cathode . The positive half-wave of the alternating current has a cleaning effect and destroys the high-melting oxide layer of the light metal, which is particularly advantageous when welding aluminum. The negative half-wave is used to melt the metal. The high thermal stress on the tungsten electrode creates a hemispherical tungsten drop at the end of the electrode. The arc burns restlessly, which is disadvantageous for fine welding. The penetration is wide and flat.

In order to take this into account, most modern TIG power sources are equipped with a balance control. As a rule, a value of 20% positive to 80% negative and vice versa can be set. Adjusting it in the negative direction results in narrower seams due to a more stable arc. However, especially at high welding speeds, care must be taken to ensure that there is enough positive component so that cleaning and melting is guaranteed. When using mixed gases with helium proportions of 20% and more, it is essential to ensure that the "cleaning effect" is adequate.