Oxide cleaning action
Oxide cleaning action in TIG welding: In the electrode positive phase, the oxide layer on aluminum is broken up by AC, enabling a clean weld pool. This prevents porosity and improves weld toughness.
Physical-Chemical Mechanism of Action
In TIG welding (AC welding), an electrical voltage is set up between the workpiece edge and the filler rod. In the electrode-positive phase, the oxide layer on aluminum is activated and broken up by the alternating current. This allows a clean weld pool to form, since there are no oxides in the pool.
Metallurgical Relevance & Welding Risks
The oxide cleaning action is crucial for weld quality. Without this cleaning, porosity can occur, which affects the strength and reliability of the weld. Missing or insufficient oxide cleaning can also lead to hot cracking, since the weld pool isn't clean.
Workshop Practice & Action Guidelines
To ensure effective oxide cleaning, the voltage and duration of the electrode-positive phase must be set precisely. A typical electrode-positive time is 1 to 2 seconds at a voltage of 50 to 70 volts. It's important that the workpiece is clean and dry before welding starts. If oxide cleaning is insufficient, the weld pool can't get clean, which can lead to porosity and hot cracking.