annealing


annealing

Treatment of a metal, alloy, or other material by heating to a predetermined temperature, holding for a certain time, and then cooling to room temperature, done to improve ductility and reduce brittleness. Process annealing is carried out intermittently during the working of a piece of metal to restore ductility lost through repeated hammering or other working, if several cold-forming operations are required but the metal is so hardened after the first operation that further cold working would cause cracking (see hardening). Full annealing is done to give workability to such parts as forged blanks destined for use in the machine-tool industry. Annealing is also done for relief of internal stresses in metal and glass. Annealing temperatures and times differ for different materials and with properties desired; steel is usually held for several hours at about 1,260°F (680°C) and then cooled for several hours. See also heat treating, solid solution.

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