Heating to and holding at a suitable temperature and then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitating cold working, producing a desired microstructure, or obtaining desired mechanical, physical or other properties.

Types of annealing include blue, black, box, bright, full, intermediate, isothermal, quench and recrystallization.

When applied to ferrous alloys, the term "annealing," without qualification, implies full annealing.

When applied to nonferrous alloys, the term "annealing" implies a heat treatment designed to soften a cold worked structure by recrystallization or subsequent grain growth or to soften an age-hardened alloy by causing a nearly complete precipitation of the second phase in relatively coarse form.

Sub-critical Annealing

A heat treating operation used to relieve or dissipate stresses in weldaments, heavily machined parts, castings and forgings. The parts are heated to 620C, uniformly heated through, and are either air cooled from temperature or slow cooled from temperature depending on the type of part and subsequent finishing or heat treating operations.

The more important purposes for which steel is annealed are:

See also: Annealing Twin, Flame Annealing, Flame Softening, Full Annealing.

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Subjects: Mechanical Engineering