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Republic Heat Treat Resources / Definitions
Normalizing - A treatment consisting of heating uniformly to temperature at least 100ºF above the critical range and cooling in still air at room temperature. The treatment produces a recrystalization and refinement of the grain structure and gives uniformity in hardness and structure to the product.

Annealing - A treatment consisting of heating uniformly to a temperature, within or above the critical range and cooling at a controlled rate to a temperature under the critical range. This treatment is used to produce a definite microstructure, usually one designed for best machinability, and /or to remove stresses, induce softness, and alter ductility, toughness or other mechanical properties. When applied to nonferrous alloys, the term "annealing", without qualification, implies full anneal. When applied to nonferrous alloys, the term annealing implies a heat treatment designed to soften a cold worked structure by recrystalization or subsequent grain growth or to soften an aged-hardened alloy by causing a nearly complete precipitation of the second phase in relatively coarse form. Any process of annealing will usually reduce stress, but if the treatment is applied for the sole purpose of such relief, it should be designated stress relieving.

Austenitizing - Forming austenite by heating uniformly to temperature at least 100ºF above the critical range and cooling in still air at room temperature. The treatment produces a recrystalization and refinement of the grain structure and gives uniformity in hardness and structure to the product.

Quenching - a treatment consisting of heating uniformly to a predetermined temperature and cooling rapidly in air or liquid medium to produce a desired crystalline structure.

Tempering - A treatment consisting of heating uniformly to some predetermined temperature under the critical range, holding at that temperature a designated period of time and cooling in air or liquid. This treatment is used to produce one or more of the following end results:

• To soften material for subsequent machining or cold work,
• To improve ductility and relieve stress resulting from prior treatment or cold working,
• To produce the desired mechanical properties or structure in the second step of a double treatment.

Stress Relieve Temper - A thermal treatment to restore elastic properties and to minimize distortion on subsequent machining or hardening operations. This treatment is usually applied to material that has been heat treated (quenched and tempered). Normal practice would be to heat to a temperature of 100ºF lower than the tempering temperatures used to establish mechanical properties and hardness. Ordinarily, no straightening is performed after stress relieve temper.

 
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