Distortion in welding is caused primarily by:

• A. The use of a tungsten electrode in the GTAW welding process
• B. The uncontrolled heating and cooling of the weld metal
• C. Exposure to radiation and other NDE techniques
• D. The excess amount of porosity in the weld metal

Answer: (B)

Distortion from welding comes from how heat is added and removed. When the weld area is heated, it expands; as it cools, it contracts. The weld zone and surrounding metal don’t cool uniformly because they are restrained by the rest of the workpiece and by the joint geometry. That unequal expansion and contraction creates residual stresses that pull the part out of square or cause bending and twisting—warping that remains after cooling. The amount of distortion is influenced by heat input, joint design, weld size and sequence, and how well the work is restrained or preheated. By controlling heat input and planning the weld sequence and fixtures, distortion can be minimized.

The other options don’t explain distortion. The tungsten electrode is a torch/arc characteristic in GTAW, not the primary cause of distortion. Exposure to radiation and NDE techniques isn’t what induces distortion. Porosity describes gas pockets in the weld, a quality defect, not the main mechanism of dimensional change due to heating and cooling.