Which process involves heating a metal and letting it cool slowly at a controlled rate in a furnace aiming to rearrange the internal crystal structure of a metal to make it less hard and more ductile?

Which process involves heating a metal and letting it cool slowly at a controlled rate in a furnace aiming to rearrange the internal crystal structure of a metal to make it less hard and more ductile?

• A. Annealing
• B. Normalising
• C. Quenching
• D. Tempering

Answer: (A)

Softening a metal by heating it and letting it cool slowly in a furnace is annealing. By heating into the range where the crystal lattice can rearrange and relieve stresses, the material can recrystallize and form new, more stable grains. The slow cooling lets these grains grow gently, resulting in a structure that is easier to deform, with reduced hardness and improved ductility. Normalising also uses heating and cooling, but it’s done in air to produce a finer, tougher grain and often higher hardness than annealing. Quenching rapidly cools the metal to trap a hard, brittle structure, while tempering re-heats a quenched metal to reduce brittleness and adjust hardness. The described process specifically aims for ductility and softness through slow furnace cooling, so it is annealing.

Softening a metal by heating it and letting it cool slowly in a furnace is annealing. By heating into the range where the crystal lattice can rearrange and relieve stresses, the material can recrystallize and form new, more stable grains. The slow cooling lets these grains grow gently, resulting in a structure that is easier to deform, with reduced hardness and improved ductility. Normalising also uses heating and cooling, but it’s done in air to produce a finer, tougher grain and often higher hardness than annealing. Quenching rapidly cools the metal to trap a hard, brittle structure, while tempering re-heats a quenched metal to reduce brittleness and adjust hardness. The described process specifically aims for ductility and softness through slow furnace cooling, so it is annealing.