Which description correctly characterizes the annealing process of steel?

• A. Rapid cooling; high hardness
• B. Slow cooling; low strength
• C. Slow cooling; high strength
• D. Rapid cooling; low strength

Answer: (B)

The process being tested is heat-treating steel to soften and improve ductility by allowing the microstructure to reorganize through diffusion. In annealing, steel is heated to a high temperature long enough for austenite to form, then cooled slowly. That slow cooling gives time for new ferrite and pearlite structures to develop rather than a hardened martensitic structure, which is what happens with rapid quenching. The result is a softer, more ductile material with lower hardness and strength, plus relief of internal stresses and improved machinability. Rapid cooling would produce high hardness but brittle martensite, and slow cooling paired with high strength would not describe annealing. Therefore, slow cooling leading to lower strength best matches the annealing description.