Why is an AC welder required for aluminum welding
Welding aluminum is particularly difficult because the material is surrounded by an oxide layer. This only melts at approximately 2015 degrees Celsius, but aluminum itself, depending on the alloy, melts at around 650 degrees. This means that the aluminum would run away while the oxide layer was being melted, making welding impossible. The oxide layer needs to be destroyed or displaced in order for the process to work. When welding using alternating current (AC), the electrode continues to change from plus to minus. When the electrode is set to positive, the negatively polarized electrons move from the workpiece into the electrode, rupturing the oxide layer in the process. The electrode is then set to negative and the electrons moving into the workpiece generate heat—this is how the penetration required for the weld seam occurs.
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