Abrasion
The process of rubbing, grinding or wearing away by friction.
Abrasive
A substance used for grinding, honing, lapping, superfinishing, polishing, pressure
blasting or barrel finishing. It includes natural materials such as garnet, emery,
corundum and diamond, and electric furnace products like aluminum oxide, silicon
carbide and boron carbide.
Adhesion
Force of attraction between the molecules (or atoms) of two different phases, such
as liquid brazing filler metal and solid copper, or plated metal and basis metal,
or enamels and base wire. Contrast with cohesion.
Adsorption
The adhesion in an extremely thin layer of molecules (as of gases, solutes, or liquids)
to the surfaces of solid bodies or liquids with which they're are in contact.
Age hardening
Hardening by aging, usually after rapid cooling or cold working. See aging.
Aging
In a metal or alloy, a change in properties that generally occurs slowly at room
temperature and more rapidly at higher temperatures. See also age hardening, artificial
aging, interrupted aging, natural aging, overaging, precipitation hardening, precipitation
heat treatment, progressive aging, quench aging and strain aging.
Alloy
A substance having metallic properties and being composed of two or more chemical
elements of which at least one is an elemental metal.
Annealing
Heating to and holding at a suitable temperature and then cooling at a suitable
rate, for such purposes as reducing hardness, improving machinability, facilitating
cold working, producing a desired microstructure or obtaining desired mechanical,
physical or other properties. When applicable, the following should be used: bright
annealing, intermediate annealing, quench annealing, recrystallization annealing
and spheroidizing.
When applied to ferrous alloys, the term "annealing" implies a heat treatment designed
to soften a cold worked structure by recrystallization or subsequent grain growth
or to soften an age-hardened alloy by causing a nearly complete precipitation of
the second phase in relatively course form.
Any process of annealing will usually reduce stresses, but if the treatment is applied
for the sole purpose of such relief it should be designated stress relieving.
Ball mill
A mill in which crushed ores and a variety of other materials are finely ground
in a rotating cylinder containing pebbles or balls (often steel).
Barrel plating
Plating articles in a rotating container, usually a perforated cylinder that operates
at least partially submerged in a solution.
Bend test
A test for determining relative ductility of metal that is to be formed (usually
sheet, strip, plate or wire) or for determining soundness and toughness of metal
(after welding, for example) or twisting insulated wire around a mandrel or its
own diameter to determine if the insulation will crack under such stress. The specimen
is usually bent over a specified diameter through a specified angle for a specified
number of cycles.
Blister
A raised area, often dome-shaped, resulting from (a) loss of adhesion between a
coating or deposit and the basis metal or (b) delamination under the pressure of
expanding gas trapped in a metal in a near subsurface zone. Very small blisters
may be called pinheads or pepper blisters.
Brazing
Joining metals by flowing a thin layer, capillary thickness, of nonferrous filler
metal into the space between them. Bonding results from the intimate contact produced
by the dissolution of a small amount of base metal in the molten filler metal without
fusion of the base metal. Sometimes the filler metal is put in place as a thin solid
sheet or as a clad layer and the composite is heated as in furnace brazing. The
term brazing is used where the temperature exceeds some arbitrary value, such as
800° F; the term soldering is used for temperatures lower than the arbitrary value.
Brazing alloy
Same as brazing filler metal.
Brazing filler metal
A nonferrous filler metal used in brazing and braze welding.
Breaks
Creases or ridges usually in "untempered" or in aged material where the yield point
has been exceeded. Depending on the origin of the break, it may be termed a crossbreak,
a coil break, an edge break or a sticker break. Insulated wire failures in the insulation.
Brinell hardness test
A test for determining the hardness of a material by forcing a hard steel carbide
ball of specified diameter into it under a specified load. The result is expressed
as the Brinell hardness number which is the value obtained by dividing the applied
load in kilograms by the surface area of the resulting impression in square millimeters.
Brittle crack propagation
A very sudden propagation of a crack with the absorption of no energy except that
stored elastically in the body. Microscopic examination may reveal some deformation
even though it is not noticeable to the unaided eye.
Brittle fracture
Separation of a solid accompanied by little or no macroscopic plastic deformation.
Typically, brittle fracture occurs by rapid crack propagation with less expenditure
of energy than for ductile fracture.
BTU
British Thermal Unit. The quantity of heat necessary to raise the temperature of
one pound of water by 1° F.
Buildup
Excessive electrodeposition that occurs on high-current-density areas, such as corners
or edges.
Burr
A turned over edge on work resulting from cutting, punching or grinding.
Camber
(1) Deviation from edge straightness usually referring to the greatest deviation
of side edge from a straight line.
(2) Sometimes used to denote crown in rolls where the center diameter has been increased
to compensate for deflection caused by the rolling pressure.
Capillary attraction
The combination force, adhesion and cohesion, which causes liquids, including molten
metals, to flow between very closely spaced solid surfaces even against gravity.
Cast Diameter
The cast diameter is taken from the convolutions of the wire; it is essentially the diameter of the wire coil when taken off of a spool.
Caustice cracking
A form of stress-corrosion cracking most frequently encountered in carbon steels
or iron-chromium-nickel alloys that are exposed to concentrated Hydroxide solutions
at temperatures of 200° to 250° C (400° to 480° F).
Chatter
In machining or grinding. (1) a vibration of the tool, wheel or workpiece producing
a wavy surface on the work and,
(2) the finish produced by such vibration.
Checks
Numerous, very fine cracks in a coating or at the surface of a metal part. Checks
may appear during processing or during service and are most often associated with
thermal treatment or thermal cycling. Also called check marks, checking or heat
checks.
Cleavage fracture
A fracture, usually of a polycrystalline metal, in which most of the grains have
failed by cleavage, resulting in bright reflecting facets. It is one type of crystalline
fracture and is associated with low energy brittle fracture. Contrast with shear
fracture.
Coefficient
A number expressing the ratio of change under certain specified conditions such
as temperature, length, volume, etc.
Cold work
Permanent strain produced by external force in a metal below its recrystallization
temperature.
Cold working
Deforming metal plastically at a temperature lower than the recrystallization temperature.
Compressive yield strength
The stress in compression, (pushed together) at which a material exhibits a specified
limiting set, commonly taken by the offset method as 0.20 percent of the specimen's
original length. Expressed as psi.
Conductivity
A measure of the ability of a metal to conduct an electric current.
Conductor
A wire, cable, or other body or medium that is suitable for carrying electric current.
Constituent
(1) One of the ingredients which make up a chemical system.
(2) A phase or combination of phases which occur in a characteristic configuration
in an alloy microstructure.
Continuous casting
A casting technique in which an ingot, billet, tube or other shape is continuously
solidified while it is being poured, so that its length is not determined by mold
dimensions.
Corrosion
The deterioration of a metal by chemical or electrochemical reaction with its environment.
Corrosion embrittlement
The severe loss of ductility of a metal resulting from corrosive attack, usually
intergranular and often not visually apparent.
Corrosion fatigue
Cracking produced by the combined action of repeated or fluctuating stress and a
corrosive environment.
Creep strength
The rate of continuous deformation under stress at a specified temperature. Generally
expressed as psi to produce 0.1 percent elongation in 10,000 hours at the temperature
indicated.
Crystalline fracture
A pattern of brightly reflecting crystal facets on the fracture surface of a polycrystalline
metal and resulting from cleavage fracture of many individual crystals. Contrast
with fibrous fracture silky fracture.
Cupping
The fracture of severely worked rods or wire where one end has the appearance of
a cup and the other that of a cone.
Cup fracture (cup-and-cone fracture)
A mixed mode fracture, often seen in tensile test specimens of a ductile material,
where the central portion undergoes plane-strain fracture and the surrounding region
undergoes plane-stress fracture. It is called a cup fracture (or cup-and-cone fracture)
because one of the mating fracture surfaces looks like a miniature cup - that is,
it has a central depressed flat-face region surrounded by a shear lip; the other
fracture surface looks like a miniature truncated cone.
Dead soft
A temper of nonferrous alloys and some ferrous alloys corresponding to the condition
of minimum hardness and tensile strength produced by full annealing.
Decarburization
Loss of carbon from the surface layer of a carbon containing alloy due to reaction
with one or more chemical substances in a medium that contacts the surface.
Defect
A departure of any quality characteristic from its intended (usually specified)
level that is severe enough to cause the product or service not to fulfill its anticipated
function. According to ANSI standards, defects are classified according to severity.
- Very serious defects lead directly to severe injury or catastrophic
economic loss.
- Serious defects lead directly to significant injury or significant
economic loss.
- Major defects are related to major problems with respect to anticipated
use.
- Minor defects are related to minor problems with respect to anticipated
use.
Defective
A quality control term describing a unit of product or service containing at least
one defect, or having several lesser imperfections that, in combination, cause the
unit not to fulfill its anticipated function. NOTE: The term defective is not synonymous
with nonconforming (or rejectable) and should be applied only to those units incapable
of performing their anticipated functions.
Degreasing
Removing oil or grease from a surface. See solvent degreasing and vapor degreasing.
Density
The weight of a metal, usually expressed in pounds per cubic inch or grams per cubic
centimeter. Do not confuse with "Specific Gravity".
Deoxidizing
(1) The removal of oxygen from molten metals by use of suitable deoixidizers.
(2) Sometimes refers to the removal of undesirable elements other than oxygen by
the introduction of elements or compounds that readily react with them.
(3) In metal finishing, the removal of oxide films from metal surfaces by chemical
or electrochemical reaction.
Die lines
Lines or markings on formed, drawn or extruded metal parts caused by imperfections
in the surface of the die.
Discontinuity
Any interruption in the normal physical structure or configuration of a part, such
as cracks, laps, seams, inclusions or porosity. A discontinuity may or may not affect
the usefulness of a part.
Discontinuous yielding
The nonuniform plastic flow of a metal exhibiting a yield point in which plastic
deformation is inhomogeneously distributed along the gauge length. Under some circumstances,
it may occur in metals not exhibiting a distinct yield point, either at the onset
of or during plastic flow.
Distortion
Any deviation from an original size, shape or contour that occurs because of the
application of stress or the release of residual stress.
Divorced eutectic
A metallographic appearance in which the two constituents of a eutectic structure
appear as massive phases rather than the finely divided mixture characteristics
of normal eutectics. Often, one of the constituents of the eutectic is continuous
with and indistinguishable from an accompanying proeutectic constituent.
Drawability
A measure of the workability of a metal subject to a drawing process.
Draw marks
See scoring, galling, pickup, die lines.
Drawing
(1) Forming recessed parts by forcing the plastic flow of metal in dies.
(2) Reducing the cross section of wire or tubing by pulling it through a die.
(3) A misnomer for tempering.
Drawing compound
A substance applied to prevent pickup and scoring during drawing or pressing operations
by preventing metal-to-metal contact of the work and die.
Ductile fracture
Fracture characterized by tearing of metal accompanied by appreciable gross plastic
deformation and expenditure of considerable energy.
Ductile crack propagation
Slow crack propagation that is accompanied by noticeable plastic deformation and
required energy to be supplied from outside the body.
Ductility
The ability of a material to deform plastically without fracturing, being measured
by elongation or reduction in area in a tensile test, by height of cupping in an
Erichsen test, or by other means.
Eddy-current testing
An electromagnetic nondestructive testing method in which eddy-current flow is induced
in the test object. Changes in the flow caused by variations in the object are reflected
into a nearby coil or coils where they are detected and measured by suitable instrumentation.
Elastic deformation
A change in dimensions directly proportional to and in phase with an increase or
decrease in applied force.
Elastic limit
The maximum stress a material will stand without permanent deformation.
Electrical resistivity
The resistance of a material to passage through it of an electric current. Expressed
as ohms (units of resistance) per mil ft. or as microhms (millionth of an ohm) per
centimeter cube at a specified temperature.
Electrochemical corrosion
Corrosion that is accompanied by a flow of electrons between cathodic and anodic
areas on metallic surfaces.
Electrolysis
Chemical change resulting from the passage of an electric current through an electrolyte.
Electrolyte
A substance that dissociates into ions in solution or when fused, thereby becoming
electrically conducting.
Electron beam microprobe analyzer
An instrument for selective analysis of a microscopic component or feature in which
an electron beam bombards the point of interest in a vacuum at a given energy level.
Scanning of a larger area permits determination of the distribution of selected
elements. The analysis is made by measuring the wavelengths and intensities of secondary
electromagnetic radiation resulting from the bombardment.
Electroplating
Electrodepositing metal (may be an alloy) in an adherent form upon an object serving
as a cathode.
Electropolishing
Enhancing the surface finish by preferential dissolution of metal at the anode.
The current density, and hence solution rate, is greatest at sharp points.
Elongation
In tensile testing, the increase in the gage length, measured after fracture of
the specimen within the gage length, usually expressed as a percentage of the original
gage length.
Erosion
The abrasion of metal or other material by liquid or gas, usually accelerated by
pressure of solid particles of matter in suspension and sometimes by corrosion.
Etching
Subjecting the surface of a metal to preferential chemical or electrolytic attack
in order to reveal structural details for metallographic examination.
Fatigue
The phenomenon leading to fracture under repeated or fluctuating stresses having
a maximum value less than the tensile strength of the material. Fatigue fractures
are progressive, beginning as minute cracks that grow under the action of the fluctuating
stress.
Fatigue life
The number of cycles of stress that can be sustained prior to failure for a stated
test condition.
Fatigue limit
The maximum stress that presumably leads to fatigue fracture in a specified number
of stress cycles. If the stress is not completely reversed, the value of the mean
stress, the minimum stress, or the stress ratio also should be stated. Compare with
endurance limit.
Fatigue ratio
The fatigue limit under completely reversed flexural stress divided by the tensile
strength for the same alloy and condition.
Fatigue strength
The maximum stress that can be sustained for a specified number of cycles without
failure. The stress being completely reversed within each cycle unless otherwise
stated.
Fatigue striations
Parallel lines frequently observed in electron microscope fractographs of fatigue
fracture surfaces. The lines are transverse to the direction of local crack propagation;
the distance between successive lines represent the advance of the crack front during
one cycle of stress variation.
Flux
(1) In metal refining, a material used to remove undesirable substances, like sand,
ash or dirt, as a molten mixture. It is also used as a protective covering for certain
molten metal baths. Lime or limestone is generally used to remove sand, as in iron
smelting; sand, to remove iron oxide in copper refining.
(2) In brazing, cutting, soldering or welding, material used to prevent the formation
of, or to dissolve and facilitate removal of, oxides and other undesirable substances.
Fracture test
Breaking a specimen and examining the fractured surface with the unaided eye or
with a low power microscope to determine such things as composition, grain size,
case depth or soundness.
Fragmentation
The subdivision of a grain into small discrete crystallites outlined by a heavily
deformed network of intersecting slip as a result of cold working. These small crystals
or fragments differ from one another in orientation and tend to rotate to a stable
orientation determined by the slip systems.
Full annealing
Annealing a ferrous alloy by austenitizing and then cooling slowly through the transformation
range.
Full hard
A temper of nonferrous alloys 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.
Gage
(1) The thickness (or diameter) of sheet or wire. The various standards are arbitrary
and differ, ferrous from nonferrous products and sheet from wire.
(2) An instrument used to measure thickness or length.
(3) An aid for visual inspection that enables the inspector to determine more reliably
whether the size or contour of a formed part meets dimensional requirements.
Gage length
The original length of that portion of the specimen over which strain, change of
length and other characteristics are measured.
Galling
A condition whereby excessive friction between high spots results in localized welding
with subsequent spalling and a further roughening of the rubbing surfaces of one
or both or two mating parts.
Galvanic corrosion
Corrosion associated with the current of a galvanic cell consisting of two dissimilar
conductors in an electrolyte or two similar conductors in dissimilar electrolytes.
Where the two dissimilar metals are in contact, the resulting reaction is referred
to as couple action.
Grain
An individual crystal in a polycrystalline metal or alloy.
Grain boundary corrosion
Same as intergranular corrosion. See also interdendritic corrosion.
Grain depth of cut
In grinding, depth of cut for an individual grain.
Grain finesness number A weighted average grain size of a granular
material. The AFS grain fineness number is calculated with prescribed weighting
factors from the standard screen analysis.
Grain growth (coarsening)
An increase in the size of grains in polycrystalline metal, usually effected during
heating at elevated temperatures. The increase may be gradual or abrupt, resulting
in either uniform or nonuniform grains after growth has ceased. A mixture of nonuniform
grains is sometime termed "duplexed". Abnormal grain growth (exaggerated grain growth)
implies the formation of excessively large grains, uniform or nonuniform. The abrupt
form of abnormal grain growth is also termed "germinative grain growth" when a critical
amount of strain or other nuclei are present to promote the growth. Secondary recrystallization
is the selective grain growth of a few grains only, as distinct from uniform coarsening,
when the new set of grains resulting from primary recrystallization is subjected
to further annealing.
Grain size
(1) For metals, a measure of the areas or volumes of grains in a polycrystalline
material, usually expressed as an average when the individual sizes are fairly uniform.
Grain sizes are reported in terms of number of grains per unit area or volume, average
diameter or as a grain-size number derived from area measurements.
(2) For grinding wheels, see preferred term, grit size.
Granular fracture
A type of irregular surface produced when metal is broken that is characterized
by a rough, grainlike appearance and differentiated from a smooth silky, or fibrous
type. It can be subclassifed into transgranular or intergranular forms. This type
of fracture is frequently called crystalline fracture, but the inference that the
metal broke because it "crystallized" is not justified because all metals are crystalline
when in the solid state. Contrast with fibrous fracture, silky fracture.
Green rot
A form of high temperature attack on stainless steel, nickel-chromium alloys and
nickel-chromium alloys subjected to simultaneous oxidation and carburization. Basically,
attack occurs by first precipitating chromium as chromium carbide, then oxidizing
the carbide particles.
Grit size
Nominal size of abrasive particles in a grinding wheel corresponding to the number
of openings per linear inch in a screen through which the particles can just pass.
Sometimes called "grain size".
Half-hard
A temper of nonferrous alloys characterized by tensile strength about midway between
those of dead soft and full hard tempers.
Hardness
Resistance of metal to plastic deformation, usually by indentation. However, the
term may also refer to stiffness or temper, or to resistance to scratching, abrasion
or cutting. Indentation hardness may be measured by various hardness tests, such
as Brinell, Rockwell and Vickers.
Heat transfer
The passage of heat from a hot to a cold body, by conduction through intervening
layers of solid, liquid or gas. Overall rate of heat transfer through a given system
of obstructions is expressed in units of heat, per unit of area of obstructions
exposed per unit of difference in temperature between the hot and cold bodies (BTU
per sq. ft. per hr. per °F). The amount of heat transferred is measure in units
of heat per unit of time (BTU per hr.). See "Thermal Conductivity".
Heat treatment
Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions
or properties. Heating for the sole purpose of hot working is excluded from the
meaning of this definition.
Helix
The helix is the measurement of how high the end of one coil of wire lifts off of a flat surface.
High-conductivity copper
Copper, which in the annealed condition, has a minimum electrical conductivity of
100% IACS as determined in accordance with ASTM methods of test.
Hot working
Deforming metal plastically at such a temperature and rate that strain hardening
does not occur. The low limit of temperature is the recrystallization temperature.
Humidity test
A corrosion test involving exposure of specimens at controlled levels of humidity
and temperature. Contrast with salt-fog test.
Hydrogen damage
A general term for the embrittlement, cracking, blistering and hydride formation
that can occur when hydrogen is present in some metals.
Hydrogen embrittlement
A condition of low ductility in metals resulting from the absorption of hydrogen.
Impact strength
A measure of toughness. The stress to fracture a notched specimen with a single
blow. Expressed in foot-pounds of energy absorbed. Designated as "Charpy" or "Izod"
impact strength depending on the testing machine used.
Impedance
(1) Acoustical impedance is the complex ratio of the sound pressure to the product
of the sound velocity and the area at a given surface. It is frequently approximated
by only the product of the density and velocity.
(2) Electrical impedance is the complex property of an electrical circuit, or the
components of a circuit, that opposes the flow of an alternating current. The real
part represents the resistance and the imaginary part represents the reactance of
the circuit.
Imperfection
(1) When referring to the physical condition of a part of metal product, and departure
of a part of metal product, any departure of a quality characteristic from its intended
level or state. The existence of an imperfection does not imply nonconformance,
nor does it have any implication as the usability of a product or service. An imperfection
must be rated on a scale of severity, in accordance with applicable specifications,
to establish whether or not the part or metal product is of acceptable quality.
(2) In crystallography, any deviation from an ideal space lattice.
Inclusions
Particles of foreign material in a metallic matrix. The particles are usually compounds
(such as oxides, sulfides or silicates), but may be of any substance that is foreign
to (and essentially insoluble in) the matrix.
Indication
In inspection, a response to a nondestructive stimulus that implies the presence
of an imperfection. The indication must be interpreted to determine if (a) it is
a true indication or a false indication and (b) whether or not a true indication
represents an unacceptable deviation.
Ingot
A casting suitable for working or remelting.
Intercept method
A quantitive metallographic technique in which the desired quantity such as grain
size or amount of precipitate is expressed as the number of times per unit length
a straight line a metallographic image crosses particles of the feature being measured.
Ion
An atom, or group of atoms, that has gained or lost one or more outer electrons
and thus carries an electric charge. Positive ions, or cations, are deficient in
outer electrons. Negative ions, or anions, have an excess of outer electrons.
Ion exchange
The interchange of ions between a liquid and solid.
Knoop hardness
Microhardness determined from the resistance of metal to indentation by a pyramidal
diamond indenter, having edge angles of 172° 30_ and 130°, making a rhombohedral
impression with one long and one short diagonal.
Liquor finish
A smooth, bright finish characteristic of wet-drawn wire when a liquor from fermented
grain mash is used as a drawing lubricant.
Lot
A finite quantity of a given product manufactured under production conditions that
are considered uniform. Often used to describe a finite quantity of product submitted
for inspection as a single group. For a bulk product (such as a chemical or powdered
metal), the term "batch" is often used synonymously with lot.
Lubricant
Any substance used to reduce friction between two surfaces in contact.
Magnetic-analysis inspection
A nondestructive method of inspection to determine the existence of variations in
magnetic flux in ferromagnetic materials of constant cross section, such as might
be caused by discontinuities and variations in hardness. The variations are usually
indicated by a change in pattern on an oscilloscope screen.
Magnetic-particle inspection
A nondestructive method of inspection for determining the existence and extent of
surface cracks and similar imperfections in ferromagnetic materials. Finely divided
magnetic particles applied to the magnetized part are attracted to and outline the
pattern of any magnetic leakage fields created by discontinuities.
Magnetic transformation point
The temperature at which a normally magnetic material becomes substantially nonmagnetic.
Also called the Curie Point.
Martensite
A generic term for microstructures formed by diffusionless phase transformation
in which the parent and product phases have a specific crystallographic relationship.
Martensite is characterized by an acicular pattern in the microstructure in both
ferrous and nonferrous alloys. In alloys where the solute atoms occupy interstitial
positions in the Martensitic lattice (such as nickel in iron), the Martensite is
soft and ductile. The amount of high temperature phase that transforms to Martensite
on cooling depends to a large extent on the lowest temperature attained, there being
a rather distinct beginning temperature (M5) and a temperature at which the transformation
is essentially complete (Mf).
Mechanical properties
The properties of a material that reveal its elastic and inelastic behavior when
force is applied, thereby indicating its suitability for mechanical applications;
for example, modulus of elasticity, tensile strength, elongation, hardness and fatigue
limit. Compare with physical properties.
Mechanical testing
Determination of mechanical properties.
Mesh
The screen number of the finest screen of a specified standard screen scale through
which almost all the particles of a powder sample will pass. Also called mesh size.
Metallizing (spray metallizing)
Forming a metallic coating by atomized spraying with molten metal or by vacuum deposition.
Metallograph
An optical instrument designed for both visual observation and photomicrography
of prepared surfaces of opaque materials at magnifications ranging from about 25
to about 2,000 diameters. The instrument consists of a high intensity illuminating
source, a microscope and a camera bellows. On some instruments, provisions are made
for examination of specimen surfaces with polarized light, phase contrast, oblique
illumination and customary brightfield illumination.
Metallography
The science dealing with the constitution and structure of metals and alloys are
revealed by the unaided eye or by such tools as low powered magnification, optical
microscope, electron microscope and diffraction or X-ray techniques.
Metallurgy
The science and technology of metals and alloys. Process metallurgy is concerned
with the extraction of metals from their ores and with the refining of metals; physical
metallurgy, with the physical and mechanical properties of metals as affected by
composition, processing and environmental conditions; and mechanical metallurgy,
with the response of metals to applied forces.
Metrology
The science of weights and measures.
Micrograph
A graphic reproduction of the surface of a prepared specimen, usually etched, at
a magnification greater than ten diameters. If produced by photographic means it
is called a photomicrograph (not a microphotograph).
Microhardness
The hardness of a material as determined by forcing an indenter such as a Vickers
of Knoop indenter into the surface of a material under very light load; usually,
the indentations are so small that they must be measured with a microscope. Capable
of determining hardnesses of different microeconomics within a structure, or of
measuring steep hardness gradients such as those encountered in case hardening.
Microscopic
Visible at magnifications greater than ten diameters.
Microstructure
The structure of metals as revealed by microscopic examination of the etched surface
of a polished specimen.
Mil
A unit of length or a measure of thickness equal to one thousandth of an inch.
Modulus of elasticity
A measure of the rigidity of metal. Ratio of stress, below proportional limit, to
corresponding strain. Specifically, the modulus obtained in tension or compression
is Young's modulus, stretch modulus or modulus of extensibility; the modulus obtained
in torsion or shear is modulus of rigidity, shear modulus or modulus of torsion;
the modulus covering the ratio of the mean normal stress to the change in volume
per unit volume is the bulk modulus. The tangent modulus and secant modulus are
not restricted within the proportional limit; the former is the slope of the stress-strain
curve at a specified point; the latter is the slope of a line from the origin to
a specified point on the stress-strain curve. Also called elastic modulus and coefficient
of elasticity.
Moh's scale
A scratch hardness test for determining comparative hardness using ten standard
minerals from talc (the softest) to diamond (the hardest).
Necking
(1) Reducing the cross-sectional area of metal in a localized area by stretching.
(2) Reducing the diameter of a portion of the length of a cylindrical shell or tube.
Necking down
Localized reduction in area of a specimen during tensile deformation.
Neutron
Elementary nuclear particle with a mass approximately the same as that of hydrogen
atom and electrically neutral; its mass is 1.008986 mass units. Neutrons are commonly
divided into classes according to their energies as follows: thermal, about 0.025
ev; either, 0.1 ev to 100 ev; slow, less than 100 3v; intermediate 102 to 105 ev;
fast, greater than 0.1 mev.
Nonconforming
A quality control term describing a unit of product or service that does not meet
normal acceptance criteria for the specific product or service. A nonconforming
unit is not necessarily defective.
Nondestructive inspection
Inspection by methods that do not destroy the part nor impair its serviceability.
Nondestructive testing
Same as nondestructive inspection, but implying use of a method in which the part
is stimulated and its response measured quantitatively or semi-quantitatively.
Nucleus
(1) The first structurally stable particle capable of initiating recrystallization
of a phase or the growth of a new phase, and possessing an interface with the parent
matrix. The term is also applied to a foreign particle which initiates such action.
(2) The heavy central core of an atom, in which most of the mass and the total positive
electric charge are concentrated.
Ohm
A unit of electrical resistance that equals the resistance of a circuit in which
a potential difference of 1 volt produces a current of 1 ampere.
Orange peel
A surface roughening in the form of a pebble-grained pattern where a metal of unusually
coarse grain is stressed beyond its elastic limit. Also called pebbles and alligator
skin.
Oxidation
A reaction which there is an increase in valence resulting from a loss of electrons.
Contrast with reduction.
Passivation
The changing of the chemically active surface of a metal to a much less reactive
state. Contrast with activation.
Peeling
The detaching of one layer of a coating from another or from the basis metal because
of poor adherence.
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.
Physical testing
Determination of physical properties.
Pitting
Forming small sharp cavities in a metal surface by nonuniform electrodeposition
or by corrosion.
Pickling
Removing surface oxides from metals by chemical or electrochemical reaction.
Plating
Forming an adherent layer of metal upon an object.
Porosity
Fine holes or pores within a metal.
Powder lubricant
Powd met. An agent mixed with or incorporated in a powder to facilitate the pressing
and ejecting of the compact.
PPM
An abbreviation for parts per million. For reference, 1% = 10,000 ppm.
Precious metal
One of the relatively scarce and valuable metals; gold, silver and the platinum-group
metals.
Precipitation hardening
Hardening caused by the precipitation of a constituent from a supersaturated solid
solution. See also age hardening and aging.
Precipitation heat treatment
Artificial aging in which a constituent precipitates from a supersaturated solid
solution. See artificial aging, interrupted aging and progressive aging.
Process annealing
In the sheet and wire industries, heating a ferrous alloy to a temperature close
to, but below, the lower limit of the transformation range and then cooling in order
to soften the alloy for further cold working.
Progressive die
A die in which two or more sequential operations are performed at two or more positions,
the work being moved from station to station.
Proof stress
The stress that may be applied without leaving permanent elongation of more than
0.001 inch per inch of the specimen's original length after removal of that stress.
Expressed in psi.
Proportional counter
Gas-filled radiation detection tube in which the pulse produced is proportional
to the number of ions formed in the gas by the primary ionizing particle.
Proportional limit
The maximum, in psi, at which strain or deformation is directly proportional to
stress.
Psi
Pounds per square inch.
Quality
(1) The totality of features and characteristics of a product or service that bear
on its ability to satisfy a given need (fitness-for-use concept of quality).
(2) Degree of excellence of a product or service (comparative concept). Often determined
subjectively by comparison against an ideal standard or against similar products
or services available from other sources.
(3) A quantitative evaluation of the features and characteristics of a product or
service (quantitative concept).
Quality characteristic
Any dimension, mechanical property, physical property, functional characteristic,
or appearance characteristic that can be used as a basis for measuring the quality
of a unit of product or service.
Quantitative metallography
Determination of specific characteristics of a microstructure by making quantitative
measurements on micrographs or metallographic images. Quantities so measured include
volume concentration of phases, grain size, particle size, mean free path between
like particles or secondary phases, and surface area to volume ratio of microconstituents.
Quarter-hard
A temper of nonferrous alloys characterized by tensile strength about midway between
those of dead soft and half hard tempers.
Quenching
Rapid cooling. When applicable, the following more specific terms should be used:
direct quenching, fog quenching, hot quenching, interrupted quenching, selective
quenching, spray quenching and time quenching.
Recrystallization
(1) The change from one crystal structure to another, as occurs on heating or cooling
through a critical temperature.
(2) The formation of a new, strain-free grain structure from that existing in cold
worked metal, usually accomplished by heating.
Reduction
(1) In cupping and deep drawing, a measure of the percentage decrease from blank
diameter to cup diameter, or of diameter reduction in redraws.
(2) In forging, rolling and drawing, either the ratio of the original to final cross-sectional
area or the percentage decrease in cross-sectional area.
(3) A reaction in which there is a decrease in valence resulting from a gain in
electrons. Contrast with oxidation.
Reduction in area
(1) Commonly, the difference expressed as a percentage of original area, between
the original cross-sectional area of a tensile test specimen and the minimum cross-sectional
area measured after complete separation.
(2) The difference, expressed as a percentage of original area, between original
cross-sectional area and that after straining the specimen.
Refractory
(1) A material of very high melting point with properties that make it suitable
for such uses as furnace linings and kiln construction.
(2) The quality of resisting heat.
Refractory alloy
(1) A heat-resistant alloy.
(2) An alloy having an extremely high melting point. See refractory metal.
(3) An alloy difficult to work at elevated temperatures.
Refractory metal
A metal having an extremely high melting point. In the broad sense, it refers to
metals having melting points above the range of iron, cobalt and nickel.
Resistance
The opposition tht a conductor offers to the passage of an electric current, measured
in ohms. (Symbol = _).
Retort
A vessel used for the distillation of volatile materials, as in the separation of
some metals and in the destructive distillation of coal.
Rockwell hardness test
An indentation hardness test based on the depth of penetration of a specified penetrator
into the specimen under certain arbitrarily fixed conditions. Not performed on wire
below .125 inch diameter.
Rod mill
(1) A mill for rolling rod.
(2) A mill for fine grinding, somewhat similar to a ball mill, but employing long
steel rods instead of balls to effect the grinding.
Roll flattening
Flattening of sheets, that have been rolled in packs, by passing them separately
through a two-high cold mill, there being virtually no deformation. Not to be confused
with roller leveling.
Rolling
Reducing the cross-sectional area of metal stock, or otherwise shaping metal products,
through the use of rotating rolls.
Rolling mills
Machines used to decrease the cross-sectional area of metal stock and produce certain
desired shapes as the metal passes between rotating rolls mounted in a framework
comprising a basic unit called a stand. Cylindrical rolls produce flat shapes; grooved
rolls produce round, square and structural shapes.
Roughness
Relatively finely spaced surface irregularities, the height, width, and direction
of which establish the predominant surface pattern.
Rust
A corrosion product consisting of hydrated oxides of iron. Applied only to ferrous
alloys.
Sample
One or more units of product (or a relatively small quantity of a bulk material)
that is withdrawn from a lot or process stream, and that is tested or inspected
to provide information about the properties, dimensions or other quality characteristics
of the lot or process stream. Not to be confused with specimen.
Scaling
(1) Forming a thick layer of oxidation products on metals at high temperature.
(2) Depositing water-insoluble constituents on a metal surface, as in cooling tubes
and water boilers.
Scoring
Marring or scratching of a smooth surface; most often caused by sliding contact
with a mating member having a hard projection or embedded particle on its surface.
Scrap
(1) Defective product not suitable for sale.
(2) Discarded metallic material from whatever source that may be reclaimed through
melting and refining.
Segment die
A die made of parts that can be separated for the ready removal of the workpiece.
Synonymous with split die.
Shear strength
The stress required to produce fracture in the plane of cross-section, the conditions
of loading being such that the directions of force and of resistance are parallel
and opposite although their paths are offset a specified minimum amount.
Sliver
A defect consisting of a very thin elongated piece of metal attached by only one
end to the parent metal into whose surface it has been rolled.
Smelting
Thermal processing wherein chemical reactions take place to produce liquid metal
from a beneficiated ore.
Soil
Undesirable material on a surface and yet not an integral part of the surface. Oil,
grease and dirt can be soils; a decarburized skin or excess hard chromium are not
soils. Loose scale is soil; hard scale may be an integral part of the surface and
hence, not soil.
Solution heat treatment
Heating an alloy to a suitable temperature, holding at that temperature long enough
to allow one or more constituents to enter into solid solution, and then cooling
rapidly enough to hold the constituents in solution. The alloy is left in a supersaturated,
unstable state and may subsequently exhibit quench aging.
Solvent
The component of either a liquid or solid solution that is present to a greater
or major extent; the component that dissolves the solute.
Spalling
Flaking or chipping.
Specific gravity
The ratio of the weight of a solid or liquid to the weight of an equal volume of
water. See density.
Specific heat
The amount of heat necessary to raise the temperature of a substance by 1° F. Expressed
as BTU per pound °F.
Split die
Same as segment die.
Spring back
(1) The elastic recovery of metal after stressing.
(2) The degree to which metal tends to return to its original shape or contour after
undergoing a forming operation.
(3) In flash, upset or pressure welding, the deflection in the welding machine caused
by the upset pressure.
Spring temper
See temper.
Strain
A measure of the change in the size or shape of a body, referred to its original
size or shape. "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 referred to the original gage length. "Shearing strain" (or
"shear strain") is the change in angle (expressed in radians) between two lines
originally at right angles. When the term strain is used alone it usually refers
to the linear strain in the direction of the applied stress.
Strain aging
Aging induced by cold working. See aging.
Strain energy
(1) The work done in deforming a body.
(2) The work done in deforming a body within the elastic limit of the material.
It is more properly elastic strain energy and can be recovered as work rather than
heat.
Strain hardening
An increase in hardness and strength caused by plastic deformation at temperatures
lower than the recrystallization.
Strain rate
The time rate of straining for the usual tensile test. Strain as measured directly
on the specimen gage length is used for determining strain rate. Because strain
is dimensionless, the units of strain rate are reciprocal time.
Stress
Force per unit area, often thought of as force acting through a small area within
a plane. It can be divided into components, normal and parallel to the plane called
"normal stress" and "shear stress" respectively. "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 the original area. "Nominal
stress" is the stress computed by simple elasticity formulas, ignoring stress raisers
and disregarding plastic flow; in a notch bend test, for example, it is bending
moment divided by minimum section modulus.
Stress equalizing annealing
Heating and cooling to homogenize stresses so as to afford the best possible combination
of ductility and strength.
Stress-relief annealing
Heating and cooling to effect partial softening. Also called Temper Annealing.
Stress-rupture test
A method of evaluating elevated temperature durability in which a tension test specimen
is stressed under constant load until it breaks. Data recorded commonly includes:
initial stress, time to rupture, initial extension, creep extension and reduction
of area at fracture.
Stripping
Removing a coating from a metal surface.
Superalloy
An alloy developed for very high temperature service where relatively high stresses
(tensile, thermal, vibratory and shock) are encountered and where oxidation resistance
is frequently required.
Super-conductivity
The abrupt and large increase in electrical conductivity exhibited by some metals
as the temperature approaches absolute zero.
Superficial Rockwell hardness test
Form of Rockwell hardness test using relatively light loads that produce minimum
penetration by the indenter. Used for determining surface hardness or hardness of
thin sections or small parts, or where a large hardness impression might be harmful.
Superheating
(1) Heating a phase above a temperature at which an equilibrium can exist between
it and another phase having more internal energy, without obtaining the high energy
phase.
(2) Heating molten metal above the normal casting temperature so as to obtain more
complete refining or greater fluidity.
Surface finish
(1) Condition of a surface as a result of a final treatment.
(2) Measured surface profile characteristic, the preferred term being roughness.
Surface grinding
Producing a plane surface by grinding.
Tachometer
An instrument for measuring speed of a shaft or machine in rpm's.
Tandem mill
A rolling mill consisting of two or more stands arranged so that the metal being
processed travels in a straight line from stand to stand. In continuous rolling,
the various stands are synchronized so that the strip may be rolled in all stands
simultaneously. Contrast with single stand mill.
Tarnish
Surface discoloration of a metal caused by formation of a thin film of corrosion
product.
Taylor process
A process for making extremely fine wire by inserting common wire into a glass tube
and stretching the two together at high temperature.
T.C.R. - Temperature Coefficient of Resistance
The change in resistance of a given conductor resulting from a 1 degree change in
temperature about a reference temperature, divided by the conductor's resistance
at that reference temperature.
Temper
(1) In heat treatment, reheating hardened steel or hardened cast iron to some temperature
below the eutectoid temperature for the purpose of decreasing the hardness and increasing
the toughness. The process also is sometimes applied to normalized steel.
(2) In tool steels, "temper" is sometimes used, but unadvisedly, to denote the carbon
content.
(3) In nonferrous alloys and in some ferrous alloys (steels that cannot be hardened
by heat treatment), the hardness and strength produced by mechanical or thermal
treatment, or both, and characterized by a certain structure, mechanical properties,
or reduction in area during cold working.
Tempering
Reheating a quench hardened or normalized ferrous alloy to a temperature below the
transformation range and then cooling at any rate desired.
Tensile strength
In tensile testing, the ratio of maximum load to original cross-sectional area.
Also called ultimate strength. Compare with yield strength.
Thermal conductivity
The measure of the heat a substance will conduct through itself, expressed in BTU
per hour per square foot of exposed surface, per °F difference between the adjacent
hot and cold bodies, per inch thickness (or the metric equivalents). Do not confuse
with "Heat Transfer".
Thermal emf
The electromotive force generated when the junction of two dissimilar metals is
heated (see thermocouple).
Thermal expansion
The increase in length caused by heating. Expressed in inches of increase, per inch
or original length, per degrees of temperature.
Thermocouple
A device for measuring temperature, consisting of lengths of two dissimilar metals
or alloys that are electrically joined at one end and connected to a voltage measuring
instrument at the other end. When one junction is hotter than the other, a thermal
electromotive force is produced that is roughly proportional to the difference in
temperature between the hot and cold junctions.
Three-quarters hard
A temper of nonferrous alloys characterized by values of tensile strength and hardness
about midway between those of half hard and full hard tempers.
Tinning
Coating metal with a very thin layer of molten filler metal.
Tolerance
The specified permissible deviation from a specified nominal dimension, or the permissible
variation in size or other quality characteristic of a part.
Torsional properties
Figures expressing values of a material when stressed by twisting.
Toughness
Resistance to impact. A combination of strength and ductility.
Tough pitch copper
Copper containing from 0.02 to 0.05% O, obtained by refining copper in a reverberatory
furnace.
Transverse
Literally, "across", usually signifying a direction or plane perpendicular to the
direction of working. In rolled plate or sheet, the direction across the width is
often called long transverse, and the direction through the thickness, short transverse.
Tumbling
An operation where the work, usually castings or forgings, is rotated in a barrel,
with metal slugs or abrasives to remove sand, scale or fins. It may be done dry
or with aqueous solution. Sometimes called rumbling or rattling.
Turk's-head rolls
Four undriven working rolls, arranged in a square or rectangular pattern, through
which strip, wire or tubing is drawn to form square or rectangular sections.
Ultrasonic cleaning
Immersion cleaning aided by ultrasonic waves which cause microagitation.
Ultrasonic testing
A nondestructive test applied to sound-conductive materials having elastic properties
for the purpose of locating inhomogeneities or structural discontinuities within
a material by means of an ultrasonic beam.
Ultrasonic waves
Wave of ultrasonic frequency. They include longitudinal, transverse, surface and
standing waves.
Uniform strain
The strain occurring prior to the beginning of localization of strain (necking);
the strain to maximum load in the tension test.
Universal mill
A rolling mill in which rolls with a vertical axis roll the edges of the metal stock
between some of the passes through the horizontal rolls.
Vacuum melting
Melting in a vacuum to prevent contamination from air, as well as to remove gasses
already dissolved in the metal; the solidification may also be carried out in a
vacuum or at low pressure.
Vacuum refining
Same as vacuum melting.
Vapor degreasing
Degreasing working vapor over a boiling liquid solvent, the vapor being considerably
heavier than air. At least one constituent of the soil must be soluble in the solvent.
Vickers hardness test
An indentation hardness test employing a 136° diamond pyramid indenter (Vickers)
and variable loads enabling the use of one hardness scale for all ranges of hardness
from very soft lead to tungsten carbide. Not performed on wire below .125 inch diameter.
Viscosity
Internal fluid friction. The property of being glutinous or sticky.
Welding
(1) Joining two or more pieces of material by applying heat, pressure or both, with
or without filler material, to produce a localized union through fusion or recrystallization
across the interface. The thickness of the filler material is much greater than
the capillary dimensions encountered in brazing.
(2) May also be extended to include brazing.
Welding procedure
The detailed methods and practices, including joint welding procedures, involved
in the production of a weldment.
Welding rod
Filler metal in rod or wire form used in welding.
Weldment
An assembly whose component parts are joined by welding.
Wenstrom mill
A rolling mill similar to a universal mill but where the edges and sides of a rolled
section are acted on simultaneously.
Wire bar
A cast shape, particularly of tough pitch copper, which has a cross section approximately
square with tapered ends, designed for hot rolling to rod for subsequent drawing
into wire.
Wiredrawing
Reducing the cross-section of wire by pulling it through a die. See Taylor process.
Yield point
The first stress in a material, usually less than the maximum attainable stress,
at which an increase in strain occurs without an increase in stress. Only certain
metals exhibit a yield point. If there is a decrease in stress after yielding, a
distinction may be made between upper and lower yield points.
Yield strength
The stress at which a material exhibits a specified deviation from proportionality
of stress and strain. An offset of 0.2% is used for many metals. Compare with tensile
strength.
Young's modulus
See modulus of elasticity.
