Why is pure tungsten not commonly used on DCEN?

When using pure tungsten on DCEN (Direct Current Electrode Negative), one of the primary challenges is related to its ability to initiate and stabilize the arc. Pure tungsten can lead to difficulties in establishing a reliable arc because it does not enhance the arc stability needed in many welding situations. The arc may not start with sufficient consistency or may be prone to fluctuations, thereby complicating the welding process.

In contrast, tungsten electrodes that contain additives, such as thorium or lanthanum, are often preferred in DCEN applications because these materials improve both the arc starting characteristics and provide better stability during the welding operation. This is particularly important in achieving a smooth weld bead, maintaining a steady arc length, and ensuring effective heat input to the workpiece.

The other factors, while relevant to the handling and functionality of tungsten electrodes, do not directly address the specific issues of arc initiation and stability that are critical when operating under DCEN conditions. Thus, the focus on strong arc starts provides a clear rationale for why pure tungsten is generally not favored in this scenario.