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Ta
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Chemical symbol for Tantalum. |
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Tantalum
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A rare metal of silver white color having excellent corrosion
resistance and a high melting point. It is widely used for chemical
process equipment and specialized aero-space and nuclear
applications. |
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Te
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Chemical symbol for Tellurium. |
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Tellurium
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Its main use in the steel industry is as an additive in leadbearing
freecutting steels to further improve their machinability. Its
presence in the steel is either within the manganese sulfide
particles, where it is partially soluble, or as particles combined
with lead or manganese. For certain applications it offers
significant improvements in machinability but the added cost is a
factor that should be taken into account. |
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Temper
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A term to which a number of definitions can be applied. These
include: a) The operation of tempering; b) The degree of hardness
left in a steel bar after quenching and tempering; c) The grading of
the hardness of low carbon cold rolled strip, e.g. Hard, Half Hard,
Quarter Hard, Skin Passed, Soft; d) An indication of the amount of
carbon present in a tool steel, e.g. razor temper, file temper, die
temper, etc. |
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Temper Brittleness
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The loss in impact resistance that is present in some low and medium
carbon alloy steels when tempered in the range of 350ºC - 600ºC. It
is revealed by the notched bar impact test but not the tensile test. |
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Temper Color
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A thin, tightly adhering oxide skin that forms when steel is
tempered at a low temperature, or for a short time, in air or a
mildly oxidizing atmosphere. Before the use of instruments such as
pyrometers, colors were used to judge temperatures when hardening
and tempering. For example, on carbon tool steel where the tempering
range may typically be from 200ºC to 350ºC, the colors change with
the rise in temperature giving Light Straw at around 210ºC, Purple
at 275ºC, and Grey at 330ºC. The practice still continues in
workshops where controlled heat treatment facilities are not
available. |
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Temper Rolling
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A light pass given to annealed cold rolled strip to prevent the
formation of kinks and stretcher strain markings on subsequent cold
working. Also termed Pinch pass and Skin pass. |
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Tempered Martensite Embrittlement
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Embrittlement of ultrahigh-strength steels caused by tempering in
the temperature range of 205 to 400°C (400 to 750°F); also called
350°C or 500°F embrittlement. Tempered martensite embrittlement is
thought to result from the combined effects of cementite
precipitation on prior-austenite grain boundaries or interlath
boundaries and the segregation of impurities at prior-austenite
grain boundaries. |
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Tempering
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A heat treatment applied to ferrous products after hardening. It
consists of heating the steel to some temperature below the
transformation range and holding for a suitable time at the
temperature, followed by cooling at a suitable rate. The object of
tempering is to decrease hardness and increase toughness to produce
the desired combination of mechanical properties. |
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Tensile Strength
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The maximum load applied in breaking a tensile test piece divided by
the original cross-sectional area of the test piece. Originally
quoted as tons/sq.in. it is now measured as Newtons/sq.mm. Also
termed Maximum Stress and Ultimate Tensile Stress. |
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Tensile Test
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A standard test piece is gripped at either end by suitable apparatus
in a testing machine which slowly exerts an axial pull so that the
steel is stretched until it breaks. The test provides information on
proof stress, yield point, tensile strength, elongation and
reduction of area. |
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Thermal Fatigue
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Fracture resulting from the presence of temperature gradients that
vary with time in such a manner as to produce cyclic stresses in a
structure. |
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Thermal Shock
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The development of a steep temperature gradient and accompanying
high stresses within a structure. |
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Thermal Stress
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Stresses in metal resulting from non-uniform temperature
distribution. |
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Thermocouple, Non-Expendable |
Those thermocouples that are not covered with fabric or plastic
insulation. One type consists of ceramic insulators over bare
thermocouple wire, sometimes inserted in a tube for stability and
protection. A second type consists of a combination of thermocouple
wires, mineral insulation, and a protecting metal sheath compacted
into a small diameter. |
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Thermocouple, Expendable
|
Such a thermocouple is made of fabric- or plastic-covered wire. The
wire is provided in coils or on spools. Insulation usually consists
of glass braid, asbestos, or ceramic fiber cloth on each conductor
plus glass braid overall. |
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Thomas Process
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The Continental name for the basic Bessemer steel making process,
now superseded by modern day BOS plants. |
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Ti
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Chemical symbol for Titanium. |
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Time Temperature Transformation Curve
|
An isothermal transformation diagram showing the relationship
between temperature and the time taken for the decomposition of
austenite when the transformation occurs at constant temperature. |
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Tin
|
When present in steel it is an undesirable impurity which gives rise
to temper brittleness. When used as a coating on steel, it has a
good resistance to corrosion for many applications. |
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Titanium
|
Small amounts added to steel contribute to its soundness and give a
finer grain size. In austenitic stainless steels it acts as a
carbide stabilizer and is used to prevent intercrystalline
corrosion, commonly termed "weld decay". Titanium carbide is also
used with tungsten carbide in the manufacture of hard metal tools. |
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Tolerances
|
The amount of variation permitted on dimensions or surfaces. The
tolerance is equal to the difference between the maximum and minimum
limits of any specified dimension. |
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Tool Steel
|
A generic term applied to a wide range of steels, both plain carbon
and alloy. It includes steels suitable for various types of cutting
tools, press tools, hot and cold heading dies, moulds for plastics
and die- casting, extrusion tools, hand tools, etc. |
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Torsional Strength
|
The resistance of a bar to twisting. Closely related to its shear
strength. |
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Total Carbon
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The sum of the free and combined carbon (including carbon in
solution) in a ferrous alloy. |
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Toughness
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The ability of a metal to rapidly distribute within itself both the
stress and strain caused by a suddenly applied load, or more simply
expressed, the ability of a material to withstand shock loading. It
is the exact opposite of "brittleness" which carries the implication
of sudden failure. A brittle material has little resistance to
failure once the elastic limit has been reached. |
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Transformation Hardening
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Heat treatment comprising austenitization followed by cooling under
conditions such that the austenite transforms more or less
completely into martensite and possibly into bainite. |
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Transformation Range
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The
temperature range in which a constitutional change occurs on heating
or cooling a metal in the solid state. It is the range where
austenite forms and ferrite or carbide progressively dissolves while
ferrous alloys are being heated. Also, the temperature range
within which austenite decomposes to form ferrite and carbide on
cooling. |
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Transformation Temperature
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The temperature at which a change in phase occurs or the limiting
temperature of a transformation range. These critical points are
denoted by symbols, e.g. Ac1; the temperature at which austenite
begins to form on heating. There are 12 principal temperatures to
which symbols are applied. The following symbols are used for irons
and steels: Accm. In hypereutectoid steel, the temperature at which
solution of cementite in austenite is completed during heating; Ac1.
The temperature at which austenite begins to form during heating;
Ac3. The temperature at which transformation of ferrite to austenite
is completed during heating; Ac4. The temperature at which austenite
transforms to delta ferrite during heating; Aecm, Ae1, Ae3, Ae4. The
temperatures of phase changes at equilibrium; Arcm. In
hypereutectoid steel, the temperature at which precipitation of
cementite starts during cooling; Ar1. The temperature at which
transformation of austenite to ferrite or to ferrite plus cementite
is completed during cooling; Ar3. The temperature at which austenite
begins to transform to ferrite during cooling; Ar4. The temperature
at which delta ferrite transforms to austenite during cooling; Ar°.
The temperature at which transformation of austenite to pearlite
starts during cooling; M1. The temperature at which transformation
of austenite to martensite is completed during cooling; M1 (or Ar°).
The temperature at which transformation of austenite to martensite
starts during cooling; NOTE: All these changes, except formation of
martensite, occur at lower temperatures during cooling than during
heating, and depend on the rate of change temperature. |
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Transgranular Cracking
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Cracking or fracturing that occurs through or across a crystal or
grains. Also called transcrystalline cracking. |
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Transgranular Fracture
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Fracture through or across the crystals or grains of a metal. Also
called transcrystalline fracture or intracrystalline fracture. |
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Transition Temperature
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The temperature at which a transition from ductile to brittle
fracture takes place in steel. It is usually determined by making a
series of Charpy impact tests at various temperatures, the
transition temperature is usually taken as the point where 50% of
the fracture is brittle. |
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Transverse Strength
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A measurement of strength when the load is applied across the
longitudinal flow of the grain of a metal. Certain impurities such
as sulfur have a detrimental effect on the transverse strength.
This can be minimized by the inclusion modification process. |
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Transverse Test
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A test taken at right angles to the principal direction of rolling
or forging. |
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TTT Curve
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An abbreviation of Time Temperature Transformation Curve. |
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Tufftriding
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A form of surface hardening, the process involves nitrogen but does
not achieve the hardness of conventional nitriding. |
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Tungsten
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When used as an alloying element it increases the strength of steel
at normal and elevated temperatures. Its "red hardness" value makes
it suitable for cutting tools as it enables the tool edge to be
maintained at high temperatures. In conjunction with other alloying
elements it finds applications in heat resisting and other severe
service conditions. |
