Gas discontinuities are reduced to flat discs parallel to the surface by Rolling.

• A. Rolling
• B. Machining
• C. Casting
• D. Welding

Answer: (A)

Rolling reshapes internal gas pockets by forcing plastic deformation in the sheet thickness while the material flows along the surface. This squeezes and spreads the pores, turning them into flat, pancake-like voids whose flat faces lie parallel to the surface. That orientation is a natural outcome of rolling and is particularly significant for ultrasonic testing, because a planar flaw facing the transducer in typical inspection setups reflects sound in a predictable way, making such discontinuities easier to detect. Other processes don’t systematically convert gas porosity into this flat-disc shape oriented with the surface, so rolling is the one that produces this specific geometry.