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S
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Chemical symbol for Sulfur. |
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Salt Bath
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A method of heating steel using a bath of molten salts. Salt baths
give uniform heating and prevent oxidation, they are used for
hardening, tempering or quenching. The type of salt used depends on
the temperature range required. For hardening, sodium cyanide,
sodium carbonate and sodium chloride are in common use. |
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Sb
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Chemical symbol for Antimony. |
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Scale
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The oxidized surface of steel produced during hot working, as in
rolling, and by exposure to air or steam at elevated temperature. |
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Scarfing
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Also termed deseaming. It is a process for burning out defective
areas on the surface of ingots or semi-finished products such as
billets so that the product is suitable for subsequent rolling or
forging. |
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Scleroscope Test
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A hardness test in which the loss in kinetic energy of a falling
metal "tup," absorbed by indentation upon impact of the tup on the
metal being tested, is indicated by the height of rebound. |
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Scrap
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It forms the basic raw material for making steel by the electric arc
process. Steel offers ecological advantages as it can be recycled
enabling the discarded car of today to appear as part of a new model
tomorrow. Scrap is sorted and graded before use and the necessary
elements are added during the steel making process to achieve the
desired specifications. |
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Se
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Chemical symbol for Selenium. Seams A surface defect caused during
the steel making process. Seams are generally formed from blow holes
in the ingot, non metallic inclusions, or stresses arising during
the solidification stage. They appear as longitudinal
discontinuities in the bar. |
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Secondary Hardness
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An increase in hardness which sometimes occurs when hardened steel
is re-heated. It can be caused by the transformation of retained
austenite to martensite or by the precipitation of alloy carbides. |
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Segregation
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A term applied to the concentration and partial separation of one or
more elements from solution during solidification of liquid steel in
an ingot mould. Sulfur and phosphorus tend to segregate to a
greater extent than other elements which can have a particular
adverse effect on machinability in high sulfur free-cutting
steels. Modern steel making and continuous casting have largely
overcome this problem. |
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Selective Heating
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Intentionally heating only certain portions of a work piece. |
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Selective Quenching
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Quenching only certain portions of an object. |
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Selenium
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An element that closely resembles sulfur in its properties. The
main use in steel is as a free cutting additive but due to high cost
its use is limited to stainless steel. One of the benefits being the
ability to obtain a very good surface finish on machined components. |
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Severity of Quench
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Ability of quenching medium to extract heat from a hot steel
work piece; expressed in terms of the H value. |
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SG Iron
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An abbreviation for Spheroidal Graphite Cast Iron. As the name
implies, graphite is present in spheroidal form instead of flakes
and compared with Grey Cast Iron it has higher mechanical strength,
ductility and increased shock resistance. |
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Shaker-Hearth Furnace
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A continuous type furnace that uses a reciprocating shaker motion to
move the parts along the hearth. |
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Shear
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(1) That type of force that causes or tends to cause two
contiguous parts of the same body to slide relative to each other in
a direction parallel to their plane of contact. (2) A type of
cutting tool with which a material in the form of wire, sheet, plate
or rod is cut between two opposing blades. (3) The type of cutting
action produced by rake so that the direction of chip flow is other
than at right angles to the cutting edge. |
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Shearing Test
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The test applied to metal to determine the stress required to
fracture it across its section. |
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Sherardizing
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A process developed in Britain in 1904 by Sherard Cowper-Coles. It
is a method of producing a protective zinc coating on iron and steel
products. |
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Shim
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A thin piece of material placed between two surfaces to obtain a
proper fit, adjustment, or alignment. The piece can also be analyzed
to measure furnace carbon potential (that is, because while in the
furnace it will quickly carburize to a level equal to the furnace
carbon potential). |
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Shore Scleroscope
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An instrument that measures the hardness of a sample in arbitrary
terms of elasticity. A diamond tipped hammer is allowed to fall
freely down a graduated glass tube on to the sample under test. The
hardness is measured by the height of the rebound. In another form
the rebounding hammer actuates the pointer of a scale so that the
height of the rebound is recorded. |
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Slack Quenching
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The incomplete hardening of steel due to quenching from the
austenitizing temperature at a rate slower than the critical cooling
rate for the particular steel, resulting in the formation of one or
more transformation products in addition to martensite. |
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Slot Furnace
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A common batch furnace where stock is charged and removed through a
slot or opening. |
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Snap Temper
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A precautionary interim stress-relieving treatment applied to high-hardenability
steels immediately after quenching to prevent cracking because of
delay in tempering them at the prescribed higher temperature. |
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Soaking
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Prolonged holding at a selected temperature to effect homogenization
of structure or composition. |
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Solid Solution
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A single, solid, homogenous crystalline phase containing two or more
chemical species. |
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Solution Heat Treatment
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Heating an alloy to a suitable temperature, holding at that
temperature long enough to cause one or more constituents to enter
into a solid solution, and then cooling rapidly enough to hold these
constituents in solution. |
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Spalling
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A chipping or flaking of a surface due to any kind of improper heat
treatment or material dissociation. |
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Spheroidizing
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Heating and cooling to produce a spheroidal or globular form of
carbide in steel. Spheroidizing methods frequently used are: 1.
Prolonged holding at a temperature just below Ae1; 2. Heating and
cooling alternately between temperatures that are just above and
just below Ae1; 3. Heating to a temperature above Ae1 or Ae3 and
then cooling very slowly in the furnace or holding at a temperature
just below Ae1; 4. Cooling at a suitable rate from the minimum
temperature at which all carbide is dissolved, to prevent
re-formation of a carbide network, and then reheating in accordance
with method 1 or 2 above. (Applicable to hypereutectoid steel
containing a carbide network.) |
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Spinning
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The formation of sheet metal blanks into hollow circular shapes.
This is carried out on a lathe with forming tools which service to
press and shape the metal. Annealing may be needed during and/or
after the operation to remove the effects of work hardening. |
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Spot Welding
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A process for joining steel sheets. The two parts are held between
electrodes and the heat generated at the interface between the
sheets causes local welding when pressure is applied. |
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Spray Quenching
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A quenching process using spray nozzles to spray water or other
liquids on a part. The quench rate is controlled by the velocity and
volume of liquid per unit area per unit of time of impingement. |
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Spring Steel
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The steels used for spring making depend on the application and type
of spring. They range from plain carbon grades in the range 0.5% to
1.00% C. to Chromium, Chromium-Vanadium, Nickel-Chromium-Molybdenum,
Silico- Manganese and Silicon-Manganese-Chromium-Molybdenum types.
Full details can be found in BS5770. |
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Spring Temper
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A temper of nonferrous alloys and some ferrous alloys characterized
by tensile strength and hardness about two-thirds of the way from
full hard to extra spring temper. |
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Stabilization
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A term applied to a number of processes: a) A type of heat treatment
to relieve internal stresses: b) The retarding or prevention of a
particular reaction by the addition of a stabilizing element; c) A
thermal and/or mechanical treatment given to magnetic material in
order to increase the permanency of its magnetic properties or
condition. |
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Stabilizing Treatment
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(1) Before finishing to final dimensions, repeatedly heating a
ferrous or nonferrous part to or slightly above its normal operating
temperature and then cooling to room temperature to ensure
dimensional stability service. (2) Transforming retained austenite
in quenched hardenable steels, usually cold treatment. (3) Heating a
solution-treated stabilized grade of austenitic stainless steel to
879( to 900(C (1600( to 1650(F) to precipitate all carbon as TiC,
NbC or TaC so that sensitization is avoided on subsequent exposure
to elevated temperature. |
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Stainless Steel
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Can be defined as a group of corrosion resisting steels containing a
minimum 10% chromium and in which varying amounts of nickel,
molybdenum, titanium, niobium as well as other elements may be
present. An Englishman, Harry Brearley, is generally acknowledged to
be the pioneer who developed stainless steels for commercial use. |
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Statistical Process Control
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The application of statistical techniques for measuring and
analyzing the variation in processes. |
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Statistical Quality Control
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The application of statistical techniques for measuring and
improving the quality of processes and products (includes
statistical process control, diagnostic tools, sampling plans, and
other statistical techniques). |
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Steel
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Generally defined as a metallic product whose principal element is
iron and where the carbon content is not more than 2%. (The presence
of large quantities of carbide forming elements may modify the upper
limit of the carbon content.) |
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Strain
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Strain.
A measure of the relative change in the size or shape of a body.
Linear strain is the change per unit length of a linear dimension.
True strain (or natural strain) is the natural logarithm of the
ratio of the length at the moment of observation to the original
gage length. Conventional strain is the linear strain over the
original gage length. Shearing strain (or shear strain) is the
change in angle (expressed in radians) between two lines originally
in right angles. Deformation produced by a stress is expressed as
the change per unit of original dimension or as angular displacement
in the case of shear. When used alone, the term usually refers to
the linear strain in the direction of the applied stress. |
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Strain Aging
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The gradual changes in physical and mechanical properties, in
particular hardness and tensile strength, which takes place
following cold rolling or deformation. At atmospheric temperatures,
this may take place over a number of weeks but can be accelerated by
heating. |
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Strain Hardening
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The loss of ductility and gain in hardness resulting from strain
aging. An increase in hardness and strength caused by plastic
deformation at temperatures below the recrystallization range. |
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Stress
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Force or load per unit area, often thought of as force acting
through a small area within a plane. Can be divided into normal,
perpendicular to the surface, and shear, parallel to the surface,
components. True stress denotes the stress where force and area are
measured at the same time. Conventional stress, as applied to
tension and compression tests, is force divided by original area.
Nominal stress, ignoring stress raisers and disregarding plastic
flow, in a notch bend test, for example, it is bending moment
divided by minimum section modulus. |
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Stress Equalizing
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A low-temperature heat treatment used to balance stresses in
cold-worked material without an appreciable decrease in the
mechanical strength produced by cold working. |
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Stress Relieving
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A heat treatment including heating and soaking at a suitable
temperature (e.g. 600-650°C) followed by cooling at an appropriate
rate in order to reduce internal stresses without substantially
modifying the steel's structure. This treatment may be used to
relieve stresses induced by machining, quenching, welding or cold
working. |
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Stress Strain Curve
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A graph in which stress (load divided by the original cross
sectional area of the test piece) is plotted against strain (the
extension divided by the length over which it is measured). |
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Sub-Critical Annealing
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Heating to, and holding at, some point below the critical
temperature. Subsequent cooling may be in air. This form of heat
treatment has a variety of uses depending on the temperature and
specification of the steel, its purpose is often to soften the
material. |
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Sub-zero Treatment
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A low temperature treatment carried out after quenching on hardened
steel to transform the retained austenite into martensite. It
involves immersing the component in a bath of solid carbon dioxide
at a temperature of minus 70-80°C. |
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Sulphur
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Generally regarded as an impurity in steel as it can have
detrimental effects on strength, ductility and weldability as well
as producing hot and cold shortness. Its content in most steels is
limited to a maximum of 0.050%. Sulfur is beneficial to machining
and is added to freecutting steels in amounts up to 0.35% with the
manganese content increased to overcome any detrimental effects. |
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Supercooling
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Cooling below the temperature at which an equilibrium phase
transformation can take place, without actually obtaining the
transformation. |
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Superheating
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Heating above the temperature at which an equilibrium phase
transformation should occur without actually obtaining the
transformation. |
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Surface Hardening
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A generic term covering several processes applicable to a suitable
ferrous alloy that produces, by quench hardening only, a surface
layer that is harder or more wear resistant than the core. There is
no significant alteration of the chemical composition of the surface
layer. The processes commonly used are carbonitriding, carburizing,
induction hardening, flame hardening, nitriding, and
nitrocarburizing. Use of the applicable specific process name is
preferred. |
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Swaging
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A method of forming or reducing steel or other metals to a desired
shape by a series of blows rapidly applied by dies or hammers. The
process is applied to wires, rods and tubes and can be used for a
variety of pointing, tapering, sizing and reducing operations. |
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Swarf
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The particles of metal arising from machining or grinding
operations, much of it finds its way to the steel maker for
remelting. |
