Correct option is C
During normalising, steel is heated above its critical temperature and then cooled in air. The mention of “hammering” in the question relates to mechanical working (like forging), which helps in breaking coarse grains into finer grains. This results in a refined microstructure, improving strength, toughness, and uniformity.
A finer grain structure enhances mechanical properties and reduces internal stresses. Other options are incorrect because normalising does not primarily aim to increase brittleness or remove oxidation, and hardening is a separate heat treatment process.
