ANS:B - Rapid heating

Rapid cooling of grey cast iron produces white cast iron. Explanation: Grey cast iron typically consists of graphite flakes dispersed in a matrix of ferrite and pearlite. During rapid cooling, such as quenching, the carbon in the cast iron doesn't have enough time to form graphite flakes. Instead, it forms cementite (iron carbide) due to the rapid solidification process. As a result, the microstructure of the cast iron changes, and it transforms from grey cast iron to white cast iron. White cast iron is characterized by its white, crystalline fracture surface due to the presence of cementite. It tends to be harder and more brittle than grey cast iron, making it suitable for specific applications where wear resistance and hardness are essential, such as in the production of abrasive-resistant parts.