quenching

quenching

Rapid cooling, as by immersion in oil or water, of a metal object from the high temperature at which it is shaped. Quenching is usually done to maintain mechanical properties that would be lost with slow cooling. It is commonly applied to steel objects, to which it gives hardness. The quenching media and the type of agitation during quenching are selected to obtain specified physical properties with minimum internal stresses and distortions. Oil is the mildest medium, and salt brine has the strongest quenching effect. In special cases, steel is cooled and held for some time in a molten salt bath, which is kept at a temperature either just above or just below the temperature where martensite begins to form. These two heat treatments, called martempering and austempering, both result in even less distortion of the metal. Copper objects hardened by hammering or other deformation at ordinary temperatures can be restored to malleability by heating and quenching. See also tempering.

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quenching [′kwench·iŋ]

(atomic physics)

Phenomenon in which a very strong electric field, such as a crystal field, causes the orbit of an electron in an atom to precess rapidly so that the average magnetic moment associated with its orbital angular momentum is reduced to zero.

(electronics)

The process of terminating a discharge in a gas-filled radiation-counter tube by inhibiting reignition.

Reduction of the intensity of resonance radiation resulting from deexcitation of atoms, which would otherwise have emitted this radiation, in collisions with electrons or other atoms in a gas.

(engineering)

Shock cooling by immersing liquid or molten material into a cooling medium (liquid or gas); used in metallurgy, plastics forming, and petroleum refining.

(immunology)

An adaptation of immunofluorescence that uses two fluorochromes, one of which absorbs light emitted by the other; one fluorochrome labels that antigen, another the antibody, and the antigen-antibody complexes retain both; the initially emitted light is absorbed and so quenched by the second compound.

(mechanical engineering)

Rapid removal of excess heat from the combustion chamber of an automotive engine.

(solid-state physics)

Reduction in the intensity of sensitized luminescence radiation when energy migrating through a crystal by resonant transfer is dissipated in crystal defects or impurities rather than being reemitted as radiation.