What is the primary use of pure tungsten in welding?

Pure tungsten is primarily used for AC welding of aluminum and magnesium because of its ability to maintain a stable arc and produce a clean weld pool in these materials. Tungsten has a high melting point and excellent thermal conductivity, making it an ideal electrode choice for the Tungsten Inert Gas (TIG) welding process. In AC mode, pure tungsten effectively handles the cleaning action necessary for aluminum, which is typically needed to remove the oxide layer on its surface. This oxide layer can hinder proper welding if not adequately addressed.

When it comes to the other materials listed in the options, while tungsten is used in various types of welding, pure tungsten electrodes are not suited for welding steel or titanium, as they do not provide the necessary performance characteristics for those metals. For stainless steel, more suitable options like thoriated or ceriated tungsten are commonly preferred due to their enhanced arc stability and improved performance under DC conditions. Thus, the use of pure tungsten is best aligned with the needs of AC welding for aluminum and magnesium.