What appears on the surface of a weld when gases do not escape?

• A. Cracks
• B. Uniform surface
• C. Porosity but not elongated
• D. Elongated porosities

Answer: (D)

Gas trapped in the weld when it can’t escape during solidification forms voids in the weld metal. As the molten metal moves and solidifies, these gas pockets tend to stretch along the direction of the weld, creating elongated voids rather than round ones. On the surface, this appears as elongated porosities along the weld seam. Cracks are a different defect caused by excessive stresses, and a uniform surface would indicate no porosity. If the gas had escaped cleanly, you’d see no porosity; if venting were very effective, porosity would be less elongated and sometimes nearly spherical.