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F
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Chemical symbol for Fluorine. |
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Face Centered Cubic Lattice
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An arrangement of atoms in crystals in which the atomic centers are
disposed in space in such a way that one atom is located at each of
the corners of the cube and one at the centre of each face. Steel in
the face-centered cubic arrangement is termed austenite. |
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Fatigue
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The phenomenon leading to fracture under repeated or fluctuating
stresses having a maximum value less than the ultimate tensile
strength of the material. Fatigue failure generally occurs at
loads which applied statically would produce little perceptible
effect. Fatigue fractures are progressive, beginning as minute
cracks that grow under the action of the fluctuating stress.
There is no obvious warning as such a crack forms without
appreciable surface deformation, making it difficult to detect.
Fractures often start from small nicks or scratches or fillets that
cause a localized concentration of stress. Failure can be
influenced by a number of factors including size, shape and design
of the component, condition of the surface or operating environment. |
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Fatigue Limit
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The maximum value of the applied alternating stress which a test
piece can stand indefinitely. |
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Fatigue Testing
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Fatigue tests are made with the object of determining the
relationship between the stress range and the number of times it can
be applied before causing failure. Testing machines are used for
applying cyclically varying stresses and cover tension, compression,
torsion and bending or a combination of these stresses. |
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Fe
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Chemical symbol for Iron. |
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Ferrite
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Ferrite is the name given any solid solution in which alpha iron is
the solvent. Ferrite is strictly a structure name and means nothing
as to composition. |
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Ferritic Steel
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A term usually applied to a group of stainless steels with a
chromium content in the range of 12- 18o and whose structure
consists largely of ferrite. Such steels possess good ductility and
are easily worked but do not respond to any hardening or tempering
processes. Types of applications include automotive trim and
architectural cladding. |
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Ferritizing Anneal
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A treatment given as-cast gray or ductile (nodular) iron to produce
an essentially ferritic matrix. For the term to be meaningful, the
final microstructure desired or the time-temperature cycle used must
be specified. |
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Ferro Alloys
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Alloys of iron with chromium, manganese, silicon, tungsten,
molybdenum or vanadium. Used in steelmaking as a means of
introducing these alloying elements into the cast or as deoxidizers. |
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Fettling
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The removal of sand adhering to castings by hammering, tumbling or
shot blasting. |
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Fin
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In rolling mill practice a fin is a projection extending from the
side of rolled sections. It causes considerable trouble and is the
result of overfill. The fin, formed when the bar or shape is fed
through one pass, is likely to be rolled back into the bar at the
next pass. It is rarely encountered in modern rolling mills. |
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Final Annealing
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An imprecise term used to denote the last anneal given to a
nonferrous alloy prior to shipment. |
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Finish Annealing
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A sub critical annealing treatment applied to cold-worked low-or
medium-carbon steel. Finish annealing, which is a compromise
treatment, lowers residual stresses, thereby minimizing the risk of
distortion in machining while retaining most of the benefits to
machinability contributed by cold working. Compare with final
annealing. |
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Fixturing
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The placing of parts to be heat-treated in a constraining or
semi-constraining apparatus to avoid heat-related distortions. See
Racking. |
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Flame Annealing
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Annealing in which the heat is applied directly by a flame. |
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Flame Hardening
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A surface hardening process in which heat is applied by a high
temperature flame followed by quenching jets of water. It is usually
applied to medium to large size components such as large gears,
sprockets, slide ways of machine tools, bearing surfaces of shafts
and axles, etc. Steels most suited have a carbon content within the
range 0.40-0.55%. |
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Flash
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A fin that arises from metal in excess of that required to fill the
final impression in a forging die and is exuded from the parting
line between the dies; similarly it can arise at the mould joint in
a casting. |
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Forced-Air Quench
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A quench utilizing blasts of compressed air against relatively small
parts such as a gear. |
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Forging
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A process of working metal to a finished shape by hammering or
pressing and is primarily a "hot" operation. It is applied to the
production of shapes either impossible or too costly to make by
other methods or needing properties not obtainable by casting.
Categories of forgings include Hammer, Press, Drop or Stamping. |
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Formability
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The relative ease with which a metal can be shaped through plastic
deformation. |
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Fracture
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The separation of material into two or more parts.
Fractures are often described by the appearance of the surface of
the break in a piece of steel. Crystalline is bright and
glittering, failure having developed along the cleavage planes of
individual crystals and can be typical of brittle material.
A silky fracture has a smooth dull grain indicative of ductile
material such as a mild steel. In tensile testing fractures
are described by shape, e.g. cup and cone. |
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Fracture Stress
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(1) The maximum principal true stress at fracture. Usually refers to
unnotched tensile specimens. (2) The (hypothetical) true stress that
will cause fracture without further deformation at any given strain. |
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Free Carbon
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The
part of the total carbon in steel or cast iron that is present in
elemental form as graphite or temper carbon. |
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Free Ferrite
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Ferrite that is formed directly from the decomposition of
hypoeutectoid austenite during cooling, without the simultaneous
formation of cementite. Also called proeutectoid ferrite. |
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Freecutting Steels
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Steels which have had additions made to improve machinability. The
most common additives are sulfur and lead, other elements used
include tellurium, selenium and bismuth. |
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Freezing Range
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That temperature range between liquidus and solidus temperatures in
which molten and solid constituents coexist. |
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Full Annealing
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Annealing a ferrous alloy by austenitizing and then cooling slowly
through the transformation range. The term is meant to denote
an annealing cycle that produces minimum strength and hardness, but
for the actual value to be known requires the composition and
starting condition of the material as well as the time-temperature
cycle. |
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Full Hard
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A temper
corresponding approximately to a cold-worked state beyond which the
material can no longer be formed by bending. In specifications, a
full hard temper is commonly defined in terms of minimum hardness or
minimum tensile strength (or alternatively, a range of hardness or
strength) corresponding to a specific percentage of cold reduction
following full annealing. For
aluminum, a full hard temper is equivalent to a reduction of 75%
from dead soft; for austenitic stainless steels, a reduction of
about 50% to 55%. |
