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P
|
Chemical symbol for Phosphorus. |
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Parkerizing
|
A chemical treatment applied to ferrous metals to improve their
corrosion resistance. The process is based on a manganese phosphate
solution which produces a fairly thick coating. This can
subsequently be painted or impregnated with oil. |
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Patenting
|
A heat
treatment process often applied to high carbon wire. The steel is
heated to a suitable temperature well above the transformation
range, followed by cooling in air or a bath of molten lead or salt.
A structure is produced suitable for subsequent cold drawing and
which will give the desired mechanical properties in the finished
state. |
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Partial Annealing
|
An imprecise term used to denote a treatment given cold worked
material to reduce its strength to a controlled level or to affect
stress relief. To be meaningful, the type of material, the degree of
cold work, and the time-temperature schedule must be stated. |
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Pd
|
Chemical symbol for Palladium. |
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Pearlite
|
A
distinctive two-phase lamellar structure in steel consisting of thin
platelets of iron carbide (Fe3C) in a ferrite (essentially, Fe)
matrix. The fine pearlitic structure (small grain size) allows
maximum drawability and strengthening in steel wire,
and is
responsible for the mechanical properties of unhardened steel. |
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Ph
|
Chemical symbol for Lead. |
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pH Value
|
A method of expressing differences in the acidity or alkalinity of a
solution. A figure of 7 is regarded as neutral, figures below this
indicate the decree of acidity and above alkalinity. |
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Phosphorus
|
An element that forms 0.12% of the earth's crust, chiefly in the
form of phosphates. Its presence in steel is usually regarded as an
undesirable impurity due to its embrittling effect, for this reason
its content in most steels is limited to a maximum of 0.050%. |
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Physical Properties
|
Properties of a metal or alloy that are relatively insensitive to
structure and can be measured without the application of force; for
example, density, electrical conductivity, coefficient of thermal
expansion, magnetic permeability and lattice parameter. Does not
include chemical reactivity. Compare with mechanical properties. |
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Pickling
|
A process to chemically remove scale or oxide from steel to obtain a
clean surface. When applied to bars or coils prior to bright
drawing, the steel is immersed in a bath of dilute sulfuric acid
heated to a temperature of around 80oC. An inhibitor is added to
prevent attack and pitting of the cleaned metal. After pickling, a
washing process takes place followed by immersion in a lime-water
bath to neutralize any remaining acid. For environmental reasons
shot blasting has largely replaced pickling. |
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Pig Iron
|
The product of the blast furnace. The term was derived from the
method of casting the bars of the pig iron in depressions or moulds
formed in the sand floor adjacent to the furnace. These were
connected to a runner (known as a sow) and when filled with metal
the runner and the numerous smaller moulds were supposed to resemble
a litter of suckling pigs, hence the term pig iron. |
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Pinch Pass
|
A term applied when, after annealing, sheet or strip is lightly
rolled with the object of preventing stretcher lines or kinks on
subsequent cold working. |
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Pipe
|
A defect that arises during the solidification of steel in the ingot
mould. As steel contracts on solidification a central cavity forms
in the upper portion of the ingot, if this is not completely removed
before rolling into bars a central defect known as "pipe" results.
The risk of piping is considerably reduced on continuously cast
steel due to molten steel being available to fill any shrinkage
cavity. |
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Plasma Spraying
|
A thermal spraying process in which the coating material is melted
with heat from a plasma torch that generates a non-transferred arc
(defined in plasma-arc welding); molten coating material is
propelled against the basis metal by the hot, ionized gas issuing
from the torch. |
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Poisson's Ratio
|
If a square bar is stressed in a testing machine in the direction of
its length so that the length increases, there is a contraction in
each opposite direction, which produces a decrease in the thickness
of the bar. The ratio between the contraction at right angles to a
stress and the direct extension is called the Poisson's ratio. Its
value in steel is in the order of 0.28. |
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Pot Quenching
|
Quenching carburized parts directly from the carburizing pot or box. |
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Powder Metallurgy
|
A method of producing components by pressing or moulding metal
powders which may be simultaneously or subsequently heated to
produce a coherent mass. |
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Precipitation Hardening
|
Hardening caused by the precipitation of a constituent from a
supersaturated solid solution. See also age hardening and aging. |
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Precipitation Heat Treatment
|
Artificial Aging in which a constituent precipitates from a
supersaturated solid solution. |
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Pre-Heating
|
Used in the hardening process. Heating before some further thermal
or mechanical treatment. For tool steel, heating to an intermediate
temperature immediately before final austenitizing. For some
nonferrous alloys, heating to a high temperature for a long time, to
homogenize the structure before working. In welding and related
processes, heating to an intermediate temperature for a short time
immediately before welding, brazing, soldering, cutting, or thermal
spraying. Pre-heating reduces the time of exposure to the hardening
temperature and helps to minimize scaling and decarburization. |
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Projection Welding
|
A welding process that uses small projections on one or both
components of the weld to localize the heat and pressure, the
projections collapse when the weld is made. |
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Proof Stress
|
The stress that will cause a specified small, permanent extension of
a tensile test piece. Commonly the stress to produce 0.2% extension
is quoted in N/mm2 for steel. This value approximates to the yield
stress in materials not exhibiting a definite yield point. |
|
Proportional Limit |
The stress
(load divided by original area of cross section of the test piece)
at which the strain (elongation per unit of gauge length) ceases to
be proportional to the corresponding stress. If the load is
removed for any stress up to this point, the material will spring
back, or assume its original dimensions. The limit is usually
determined from a load-elongation diagram, obtained by plotting
extensometer readings and is the stress at which the load-elongation
line ceases to be straight. |
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Pusher Furnace
|
A type of continuous furnace in which parts to be heated are
periodically charged into the furnace in containers, which are
pushed along the hearth against a line of previously charged
containers thus advancing the containers toward the discharge end of
the furnace, where they are used. |
