How is Incomplete Fusion (IF) due to cold lap defined?

Incomplete fusion (IF) specifically refers to a condition where the weld metal does not fully fuse with the adjoining weld or base metal surfaces. This condition occurs when there is insufficient heat, improper technique, or cleanliness issues during the welding process.

The correct choice defines this condition as a discontinuity that exists between two adjacent weld beads or between the weld metal and the base metal that is not open to the surface. This emphasizes that the incomplete fusion results in a weak bond without any visible external cracks or gaps, creating a potential failure point that can affect the integrity of the welded joint.

Understanding this definition is crucial for welders and inspectors to properly identify and address issues related to incomplete fusion, ensuring that welds meet the required strength and quality standards outlined in the API 1104 guidelines.