Tempering p. pr. & vb. n. : of Temper

Tempering n. : The process of giving the requisite degree of hardness or softness to a substance, as iron and steel; especially, the process of giving to steel the degree of hardness required for various purposes, consisting usually in first plunging the article, when heated to redness, in cold water or other liquid, to give an excess of hardness, and then reheating it gradually until the hardness is reduced or drawn down to the degree required, as indicated by the color produced on a polished portion, or by the burning of oil.

Example:
Tempering chocolate vs melting wafers?

Taxonomy
steel, martensite, metal, precipitate, alloys, work piece, bainite, tempering process, alloying elements, free encyclopedia, ferrite, cementite, particles, carbon atoms, Improves, brittle, superalloys, precipitation hardened.

Defination from the web:
Tempering is a heat treatment technique for metals, alloys and glass. In steels, tempering is done to "toughen" the metal by transforming brittle ... Tempering is accomplished by a controlled reheating of the work piece to a temperature below its lower critical temperature. ...