Which filler metal AWS classification is used specifically for welding aluminum?

The AWS classification that is specifically used for welding aluminum is ER4043. This classification designates a filler metal that contains silicon, which helps to improve the fluidity of the weld pool and provides excellent wetting characteristics when welding aluminum and aluminum alloys. The ER4043 filler metal is commonly used for applications in automotive and aerospace industries, and its composition makes it well-suited for producing strong, ductile welds in both base aluminum and heat-treated aluminum alloys.

In the context of aluminum welding, ER4043 is often favored due to its ability to enhance the overall appearance and integrity of the weld. This filler metal has a lower melting point compared to other options, which contributes to the ease of welding and minimizes the risk of creating defects like porosity or cracking.

Other filler metals listed, such as ER308, are intended for welding materials like stainless steel. ER70S-X is generally used for carbon steel and low-alloy steel applications. The classification ER4160 doesn't directly correspond to any widely recognized aluminum filler metal. Therefore, ER4043 is the correct choice specifically for aluminum welding applications.