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C
|
Chemical symbol for Carbon. |
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Ca
|
Chemical symbol for Calcium. |
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Calcium
|
In the form of calcium silicide acts as a deoxidizer and degasifier
when added to steel. Recent developments have found that carbon and
alloy steels modified with small amounts of calcium show improved
machinability and longer tool life. Transverse ductility and
toughness are also enhanced. |
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Car Furnace
|
A batch-type furnace using a car on rails to enter and leave the
furnace area. Car furnaces are used for lower stress relieving
ranges. |
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Carbon
|
A nonmetallic element
that is the principal hardening element present in all steels.
In general, increased carbon content reduces ductility but increases
tensile strength and the ability of the steel to harden when cooled
rapidly from elevated temperatures. At
temperatures below 700°C,
carbon is present in steel as iron carbide, cementite, Fe3C.
The cementite forms lamellae, which “reinforces” the iron.
This explains why a steel with a high-carbon content is harder than
one with a low-carbon content. Generally, 0.05 to 0.25% is
considered low-carbon steel, 0.25 to 0.5% is medium-carbon and 0.5
to 0.9% is high-carbon. The mixture of ferrite and cementite in a
grain is called pearlite. Ductility and weldability decrease
with increasing carbon content. Austenite can dissolve up to
2% carbon. When cooled in water or oil, carbon stays in a
supersaturated solution of martensite. |
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Carbon Potential
|
A measure of the ability of an environment containing active carbon
to alter or maintain, under prescribed conditions, the carbon level
of the steel. NOTE: In any particular environment, the carbon level
attained will depend on such factors as temperature, time and steel
composition. |
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Carbon Restoration
|
Replacing the carbon lost in the surface layer from previous
processing by carburizing this layer to substantially the original
carbon level. Sometimes called recarburizing. |
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Carbon Steel
|
A steel whose properties are determined primarily by the amount of
carbon present. Apart from iron and carbon, manganese up to 1.5% may
be present as well as residual amounts of alloying elements such as
nickel, chromium, molybdenum, etc. It is when one or more alloying
elements are added in sufficient amount that it is classed as an
alloy steel. Also known as ordinary steel, straight carbon steel, or
plain carbon steel. |
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Carbo-Nitriding
|
A case-hardening process in which steel components are heated in an
atmosphere containing both carbon and nitrogen. |
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Carburizing
|
The introduction of carbon into the surface layer of a steel that
has a low carbon content. The process is carried out by heating the
components in a solid liquid, or gaseous carbon containing medium.
The depth of penetration of carbon into the surface is controlled by
the time and temperature of the treatment. After carburising it is
necessary to harden the components by heating to a suitable
temperature and quenching. |
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Case
|
The surface layer of a steel whose composition has been changed by
the addition of carbon, nitrogen, chromium, or other material at
high temperature. |
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Case-Hardening
|
The process of hardening the surface of steel whilst leaving the
interior unchanged. Both carbon and alloy steels are suitable for
case-hardening providing their carbon content is low, usually up to
a maximum of 0.2%. Components subject to this process, particularly
in the case of alloy steels, have a hard, wear-resistant surface
with a tough core. |
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Cast Iron
|
A definition can be applied that Cast Iron is an alloy of iron and
carbon in which the carbon is in excess of the amount that can be
retained in solid solution in austenite at the eutectic temperature.
Carbon is usually present in the range of 1.8% to 4.5%, in addition,
silicon, manganese, sulfur and phosphorus are contained in varying
amounts. Various types of cast iron are covered by a British
Standard classification and includes grey, malleable and white
irons. Elements such as nickel, chromium, molybdenum, vanadium can
be added to produce alloy cast irons. |
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Cast Steel
|
A term originally applied to crucible steel and sometimes today used
to describe tool steels. The term is misleading and is falling into
misuse. It can also be applied to steel castings made by pouring
molten steel into a mould but which are not subject to further
forging or rolling. |
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Cb
|
Chemical symbol for Columbium. |
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Ce
|
Chemical symbol for Cerium. |
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Cementite
|
An iron carbide (Fe3C) constituent of steel. It is hard, brittle and
crystalline. Steel which has cooled slowly from a high temperature
contains ferrite and pearlite in relative proportions varying with
the chemical composition of the steel. Pearlite is a lamellar
structure of ferrite and cementite. |
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Charpy Test
|
A test to measure the impact properties of steel. A prepared test
piece, usually notched, is broken by a swinging pendulum. The energy
consumed in breaking the test piece is measured in Joules. The more
brittle the steel the lower the impact strength. Izod is a similar
and more widely used impact test in this country. Both are quoted in
the current edition of BS 970. |
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Chromium
|
When used as an alloying element, chromium increases the
hardenability of steel and in association with high carbon gives
resistance to wear and abrasion. Chromium has an important effect on
corrosion resistance and is present in stainless steels in amounts
of 12% to 20%. It is also used in heat-resisting steels and high
duty cast irons. |
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Co
|
Chemical symbol for Cobalt. |
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Cobalt
|
An alloying element used in tool, magnet and heat resisting steels.
Together with tungsten and molybdenum, cobalt is used to form the
super high speed steels. It improves the red hardness value of the
steel, that is, it enables the steel to resist softening at a high
temperature or in the case of a cutting tool to hold its edge under
severe conditions. |
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Coefficient of Expansion
|
The ratio of change in length, area, or volume per degree to the
corresponding value at a standard temperature. |
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Cogging
|
An intermediate rolling process when a hot ingot is reduced to a
bloom or slab in a cogging mill. |
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Cold Drawing
|
The process of reducing the cross sectional area of wire, bar or
tube by drawing the material through a die without any pre-heating.
Cold drawing is used for the production of bright steel bar in round
square, hexagonal and flat section. The process changes the
mechanical properties of the steel and the finished product is
accurate to size, free from scale with a bright surface finish. |
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Cold Treatment
|
Exposing to suitable subzero temperatures for the purpose of
obtaining desired conditions or properties such as dimensional or
microstructural stability. When the treatment involves the
transformation of retained austenite, it is usually followed by
tempering. |
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Cold Working
|
Altering the shape or size of a metal by plastic deformation.
Processes include rolling, drawing, pressing, spinning, extruding
and heading, it is carried out below the recrystallisation point
usually at room temperature. Hardness and tensile strength are
increased with the degree of cold work whilst ductility and impact
values are lowered. The cold rolling and cold drawing of steel
significantly improves surface finish. |
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Compressive Strength
|
The maximum compressive stress that a material is capable of
developing, based on original area of cross section. If a material
fails in compression by a shattering fracture, the compressive
strength has a very definite value. If a material does not fail in
compression by shattering fracture, the value obtained for
compressive strength is an arbitrary value depending upon the degree
of distortion that is regarded as indicating complete failure of the
material. |
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Contact Corrosion
|
When two dissimilar metals are in contact without a protective
barrier between them and they are in the presence of liquid, an
electrolytic cell is created. The degree of corrosion is dependent
on the area in contact and the electro-potential voltage of the
metals concerned. The less noble of the metals is liable to be
attacked, i.e. zinc will act as a protector of steel in sea water
whereas copper or brass will attack the steel in the same
environment. |
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Contact Fatigue
|
Cracking and subsequent pitting of a surface subjected to
alternating Hertzian stresses such as those produced under rolling
contact or combined rolling and sliding. The phenomenon of contact
fatigue is encountered most often in rolling-element bearings or in
gears, where the surface stresses are high due to the concentrated
loads and are repeated many times during normal operation. |
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Continuous Casting
|
A method of producing blooms, billets and slabs in long lengths
using water cooled moulds. The castings are continuously withdrawn
through the bottom of the caster whilst the teeming of the metal is
proceeding. The need for primary and intermediate mills and the
storage and use of large numbers of ingot moulds is eliminated. The
continuous casting process is also used in the production of cast
iron, aluminium and copper alloys. |
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Continuous Type Furnace
|
A furnace used for heat-treating materials that progress
continuously throughout the furnace, entering one door and being
discharged from another. |
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Control Zone
|
A portion of the working zone of a piece of thermal processing
equipment having a separate sensor/instrument/heat input or output
mechanism to control its temperature. |
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Controlled Atmosphere
|
A gas or mixture of gases in which steel is heated to produce or
maintain a specific surface condition. Controlled atmosphere
furnaces are widely used in the heat treatment of steel as scaling
and decarburisation of components is minimized by this process. |
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Controlled Cooling
|
Cooling from an elevated temperature in a pre-determined manner, to
avoid hardening, cracking, or internal damage, or to produce desired
microstructure or mechanical properties. |
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Cooling Curve
|
A curve showing the relation between time and temperature during the
cooling of a material. |
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Cooling Stresses
|
Residual stresses resulting from non-uniform distribution of
temperature during cooling. |
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Core
|
In the case of steel this refers to a component that has been
case-hardened where the centre is softer than the hard surface layer
or case. It can also be applied to the central part of a rolled
rimming steel. |
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Correction Factor
|
That number of degrees, determined from the most recent calibration,
which must be added to, or subtracted from, the temperature reading
of a sensor, or an instrument, or a combination thereof (system) to
obtain NIST true temperature. When expressed as a percent, it means
percent of reading. The correction factors of sensors and
instruments are usually kept separately and added together
algebraically when a combination is used. |
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Corrosion Embrittlement
|
The severe loss of ductility of a metal resulting from corrosive
attack, usually intergranular and often not visually apparent. |
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Corrosion Fatigue
|
Fatigue that arises when alternating or repeated stress combines
with corrosion. The severity of the action depends on the range and
frequency of the stress, the nature of the corroding condition and
the time under stress. |
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Cr
|
Chemical symbol for Chromium. |
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Creep
|
The dimensional change
with time of a material under a mechanical load. The flow or
plastic deformation of metals held for long periods of time
at stresses lower than the normal yield strength. Plastic
deformation that proceeds slowly and continuously when stress is
applied at elevated temperatures. In steel, creep is
negligible below about 300°C (572°F). Methods of creep testing
involve the determination of strain/time curves under constant
tensile load and at constant temperature. |
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Creep Strength
|
The
constant nominal stress that will cause a specified quantity of
creep or secondary creep in a given time at a constant temperature.
The resulting rate of continuous deformation is often expressed as
PSI to produce 0.1 percent elongation in 10,000 hours at the
temperature indicated. |
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Critical Cooling Rate
|
The
slowest rate of cooling required to suppress phase changes.
The term is most usually applied to the rate of quenching various
products that are heated or “worked.” For example, the rate
required to produce a martensic structure in the hardening of steel.
The critical cooling rate in patenting is selected to provide
minimum pearlitic spacing. |
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Critical Diameter
|
(D) Diameter of the bar that can be fully hardened with 50%
martensite at its center. |
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Critical Point
|
This generally refers to a temperature at which some chemical or
physical change takes place. These transformations cause evolution
of heat on cooling or absorption of heat on heating and appear as
discontinuities or arrest points in the heating and cooling curves.
The temperatures vary with the carbon content of the steel and the
rate of cooling. |
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Critical Range
|
The temperature range between an upper and lower critical point for
a given material. |
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Critical Temperature
|
The temperature at which some phase change occurs in a metal during
heating or cooling, i.e. the temperature at which an arrest or
critical point is shown on heating or cooling curves. |
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Crystalline Fracture
|
A type of fracture that appears bright and glittering, it having
formed along the cleavage planes of the individual crystals.
Normally an indication that brittle fracture has occurred. |
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Crystallization
|
(1) The separation, usually from a liquid phase on cooling, of
a solid crystalline phase. (2) Sometimes erroneously used to explain
fracturing that actually has occurred by fatigue. |
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Cu
|
Chemical symbol for Copper. |
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Cyanide Hardening
|
A process of introducing carbon and nitrogen into the surface of
steel by heating it to a suitable temperature in a molten bath of
sodium cyanide, or a mixture of sodium and potassium cyanide,
diluted with sodium carbonate and quenching in oil or water. This
process is used where a thin case and high hardness are required. |
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Cycle Annealing
|
An annealing process employing a predetermined and closely
controlled time-temperature cycle to produce specific properties or
microstructures. |
