Which material category is associated with bursts, laps, and cracks as discontinuities?

• A. Castings
• B. Welds
• C. Forgings
• D. Extrusions

Answer: (C)

Discontinuities in forged parts arise from the plastic deformation and flow of metal during shaping. Forging pushes metal into new shapes, creating highly directional grain structure and complex flow paths. This can produce surface folds or overlaps called laps, where material has folded over itself. If the flow or internal pressure gets excessive, the surface can rupture, producing bursts. Cracks can form from tensile stresses that develop during heating, deformation, or cooling, especially when the material is overworked or improperly heated. These types of flaws are characteristic of forging processes, whereas other categories tend to have different typical defects (for castings, porosity or misruns; in welds, lack of fusion or welding cracks; in extrusions, other flow-related surface irregularities).