____ of metals is the controlled heating and cooling of metals to change their characteristics.
A) Heat treatment
B) Case hardening
C) Annealing
D) Direct hardening

Question

Quizplus · Accepted Answer

Heat treatment is the controlled heating and cooling of metals to alter their properties, such as improving strength or hardness, increasing toughness or elasticity, and changing their electrical or magnetic properties. Case hardening involves adding a layer of hardness to the surface of a metal by changing its composition and is a specific type of heat treatment. Annealing is a heat treatment process that involves heating a metal to a specific temperature and then slowly cooling it to increase its ductility and reduce its hardness, whereas direct hardening is a specific heat treatment process that involves hardening a metal by heating it to a specific temperature and then rapidly cooling it.

____ of Metals Is the Controlled Heating and Cooling of Metals