Which of the following best describes a forging-related discontinuity that is not detectable by visual testing?

• A. Laminations
• B. Bursts
• C. Seams
• D. Laps

Answer: (C)

Visual testing only sees surface flaws, so a defect that can hide inside the material is the one that escapes this kind of inspection. A seam in forging is a line that forms along the forge flow and can remain internal, not always visible from the outside. Because it can lie beneath the surface, it may not be detected by a simple visual check and would require deeper nondestructive methods like radiography or ultrasound to reveal. The other defects tend to show up more readily on or near the surface (laps) or have characteristics that are more readily identified through surface inspection, or are more commonly found as internal features with detectable signs in practice. So a seam best fits a forging-related discontinuity that is not detectable by visual testing.