Annealing is used to induce softness, to alter ductility, toughness, electric, magnetic, or mechanical properties; or to produce a definite micro-structure.

Steel is annealed by heating the steel to a temperature above the upper critical temperature, holding it there until the temperature is uniform throughout the part, and then slow cooling the part through the transformation range. The heating and cooling rates depend on the composition, shape, and size of the part.

Full annealing removes the internal stresses, which build up because of cold working and other fabrication processes.