A welding discontinuity typically referred to as distortion is caused 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 in welding comes from uncontrolled heating and cooling of the weld area. When you weld, the metal in the weld zone gets very hot and expands. As it cools, it contracts. If the surrounding base metal restrains that movement, the different parts of the joint heat and cool at different rates, creating residual stresses that pull the workpiece out of its original shape. The amount of distortion depends on heat input, joint design, restraint, material thickness, and cooling rate.

The other options don’t describe this geometric change. The use of a tungsten electrode in GTAW is a tool choice that can affect heat input but isn’t the cause of distortion by itself. Exposure to radiation and NDE techniques doesn’t physically deform the material. Porosity relates to voids in the weld metal, not the overall distortion of the part.