How does the material type influence the GTAW polarity setting?

The influence of material type on the GTAW polarity setting is significant as it determines the effectiveness of the welding process. Different materials have varying characteristics that affect their interaction with the welding arc.

Steel, a ferrous metal, commonly uses direct current (DC) in the negative polarity (DCEN) for GTAW. This polarity provides a more concentrated arc, allowing for better control and penetration when working with steel, which typically requires heat management and precision due to its commonly thicker sections and different thermal conductivity.

Aluminum, on the other hand, is a non-ferrous metal that poses unique challenges during welding. It reflects a large amount of the arc's heat and has a higher thermal conductivity. Using alternating current (AC) helps in addressing these challenges because AC allows for a cleaning action (due to the ‘positive’ half of the cycle) that removes the oxide layer that forms on aluminum. This oxide needs to be eliminated to achieve a proper weld.

Therefore, the correct response highlights that steel typically utilizes direct current while aluminum requires alternating current, underscoring the importance of understanding the specific requirements for different materials in the GTAW process.