Which type of penetration is expected when using DCEN polarity in GTAW?

Using Direct Current Electrode Negative (DCEN) polarity in Gas Tungsten Arc Welding (GTAW) results in deep penetration. This is primarily because the majority of the heat generated during the welding process is concentrated at the workpiece rather than the electrode. In DCEN, the electrode effectively transfers a smaller amount of energy to itself while directing a greater portion of that energy to the base material.

This characteristic of DCEN creates a highly focused heat source that is efficient in melting and fusing the base metals deeply. As a result, welds produced with DCEN tend to have narrow and deep penetration profiles, which is advantageous for thicker materials that require strong joints.

In contrast, the other options describe varying degrees of penetration that would not accurately reflect the nature of DCEN polarity. Shallow and medium penetration would typically be associated with alternatives like Direct Current Electrode Positive (DCEP), where less heat is directed into the workpiece, leading to wider and less penetrating welds. No penetration would suggest an ineffective welding process altogether, which does not apply in the context of using DCEN. Therefore, the understanding of penetration in relation to polarity is crucial for achieving the desired weld characteristics in GTAW applications.