ALUMINUM GLOSSARY - Airoldi Metalli

ALUMINUM GLOSSARY
AMS
Abbreviation for Aerospace Material Specification.
ASTM
Abbreviation for American Society for Testing and Materials.
Adhesion
Bonding strength. The attraction of a coating to the surface to which it is applied.
Adjustable Cores & Die Plate Die
Die with inserts in the core and/or plate that can be adjusted to compensate for deflection or replaced
because of wear.
Age Hardening
An aging process that results in increased strength and hardness.
Aging
Precipitation from solid solution resulting in a change in properties of an alloy, usually occurring slowly at
room temperature (natural aging) and more rapidly at elevated temperatures (artificial aging).
Alloy
A substance with metallic properties, composed of two or more chemical elements of which at least one is
a metal. More specifically, aluminum plus one or more other elements, produced to have certain specific,
desirable characteristics.
Alumina
Aluminum oxide produced from bauxite by a complicated chemical process. It is a white powdery material
that looks like granulated sugar. Alumina is an intermediate step in the production of aluminum from
bauxite, and is also a valuable chemical on its own.
Aluminum
A silver-white soft metal, noted for its lightness, high reflectivity, high thermal conductivity, nontoxicity,
and corrosion resistance. It is the most abundant metallic element, comprising about 1/12th of the earth's
crust. It is never found in nature as an elemental metal, but only in combination with oxygen and other
elements. In ordinary commercial and industrial use, the word aluminum is often understood to mean
aluminum alloy, rather than the pure metal.

Aluminum Oxide
A chemical compound of aluminum with oxygen, which forms immediately on an unprotected aluminum
surface exposed to air. Unlike iron oxide (the rust which forms on steel) aluminum oxide does not flake
off, but forms a protective layer that blocks further oxidation and so protects the integrity of the metal. It
is transparent and does not alter the appearance of the aluminum surface.
Angularity
Conformity to, or deviation from, specified angular dimensions in the cross section of a shape or bar.
Annealing
A thermal treatment to soften metal by removal of stress resulting from cold working or by coalescing
precipitates from solid solution.
Anodizing
Forming a coating on a metal surface produced by electrochemical treatment through anodic oxidation.
This process may be used to increase the protective effect of aluminum's transparent natural oxide
surface. It may also be given a decorative coloration.
Aperture
In an extrusion die, the shaped opening through which the heat-softened metal is forced and which gives
the extruded product its cross-sectional shape. Also called the orifice.
Architectural Finish
An architectural finish is a standard finish characterized by a uniform appearance. This finish is most often
specified for exposed surfaces.
Assembly Fit
Refers to two parts designed for mating assembly and requiring exact dimensions and contours to assure
a proper fit.
Assignable Cause
A factor contributing to variation that is feasible to detect and identify.
Backer (back-up plate)
A tool , or reinforcing part, which presses against the outer surface of an extrusion die, supporting it
against the pressure of the extruding metal. The backer has an opening larger than the die aperture,
allowing the extruded product to emerge without marring its soft surface.
Back Taper (Relief)

Cut-away portion of die beginning at breakaway point to the die exit either angled or undercut (stepped
back) for back clearance.
Bake
The curing of paint at an elevated temperature for a specific period of time, allowing the paint to become
hard and dry.
Bar
A solid extrusion that is long in relation to cross section, which is square or rectangular (excluding plate or
flattened wire) with sharp or rounded corners or edges; or is a regular hexagon or octagon; and in which
at least one perpendicular distance between parallel faces is 0.375 inch or greater. (Smaller sizes are
classified as wire.)
Bauxite
One of the ores from which alumina is extracted and from which aluminum is eventually smelted. Bauxite
usually contains at least 45 percent aluminum oxide (alumina), and the best grades have a low silica
content. About four pounds of bauxite is required to produce one pound of aluminum.
Beam
The principal horizontal load-bearing member of a structure.
Bearing
The surface of the extruding aperture, at right angles to the die face, that controls metal flow and to some
extent speed of flow which is also the conforming surface along which the aluminum flows.
Bell
Electrostatic spray device whose paint applicator is bell-shaped, atomizing paint off its edge.
Belly
The area of a liner that has an increased inside diameter from nominal, appearing convex (may be caused
by a weak container).
Billet, Extrusion
May be solid or hollow in form, commonly cylindrical, used as the final length of material charged into the
extrusion press cylinder. It is usually a cast product, but may be a wrought product or sintered from
powder compact.
Billet Container
The part of an extrusion press into which the billet to be extruded is placed.

Blank
A piece of metal cut or formed to regular or irregular shape for subsequent processing such as by forming,
bending, or drawing. The piece of sheet stock cut out by blanking die. It will subsequently be drawn into a
cup or end shell.
Blending
The machining of the transition in the bearing length from long to short.
Blister
A raised area on the surface of an extruded product due to subsurface gas expansion during extrusion or
thermal treatment.
Blistering
A defect in the paint film appearing as bubbles, usually caused by the expansion of air, solvent vapor, or
moisture trapped beneath the film.
Blocking
The use of graphite blocks to support the emerging extrusion as it exits the die.
Bloom
A semi-finished hot rolled product, rectangular or square in cross section, produced on a blooming mill.
Blow Hole
A blister that has ruptured and may produce a void. See also Blister .
Bolster (die block)
A tool , or reinforcing part, which supports the backer -- which, in turn, supports an extruding die against
the pressure of extrusion.
Bow
Longitudinal curvature of rod, bar, profiles (shapes), and tube. Bow is measured after allowing the weight
of the extrusion to minimize the deviation. Bow can be caused by a non-uniform extrusion rate across the
cross section resulting in one portion of the extrusion being longer than the other or non-uniform
contraction during quenching.
Bow, Lateral
Deviation from straight of a longitudinal edge.

Bow, Longitudinal
Curvature in the case of sheet or plate in the rolling direction, along the length of an extrusion.
Bow, Transverse
Curvature across the rolling direction of sheet or plate, across the width of an extrusion.
Breakaway Point
Is usually formed by the step where die undercut starts and bearing surface ends and is also where the
extrusion leaves the bearing.
Breakout Pressure
The initial pressure required to start metal flow through the extrusion die.
Breakthrough
The point in time when the billet emerges from the exit side of the die as an extruded profile.
Bridge
In extrusion: the part of an extrusion bridge die that supports a void-forming mandrel. During extrusion,
the metal divides and flows around the bridge, reuniting as it is extruded through the die orifice. The
resulting weld line can be detected upon microscopic examination, but the extrusion appears functionally
and visually seamless.
Bridge Type Die
A die having a stationary core or mandrel which is held in place by core supports or webs (bridge) bolted
to the back of the die. The die contains a weld chamber so that when the billet is pushed the metal divides
to flow around the core supports and welds together in the welding chamber before passing through the
die. See Porthole Die and Spider Die . Bridge dies normally have unenclosed ports which protrude into the
container liner.
Bridging (Webs Network)
The network of support webs which hold in place the internal surface forming portion of the mandrel,
created when the ports are machined into the mandrel.
Bridging (Design Purpose)
Is used to reduce pressure on critical tongue areas of a semi-hollow or hollow die.
Bright Dipping

Chemical polishing of aluminum, often by treatment with a mixture of nitric acid and phosphoric acid,
yielding a mirror-shiny (specular), highly reflective surface. It is almost always followed by anodizing to
protect the surface and provide some choice of colors.
Brinell Hardness
See Hardness , Brinnell .
Broken Die
A deviation from the desired cross section due to the absence of a certain portion of the die used to
extrude the profile (shape).
Buckle
A distortion of the surface of the metal.
Buffing
A mechanical finishing operation in which fine abrasives are applied to a metal surface by rotating fabric
wheels for the purpose of developing a lustrous finish.
Burr
A thin ridge of roughness left by a cutting operation such as slitting, trimming, shearing, blanking, or
sawing.
Burrs
Tiny, almost microscopic shards of die steel protruding into the die aperture (opening), usually from either
the entry or exit edge of the bearing. They are typically formed during the manufacture of the die but can
also be formed by striking the die opening with a hammer, dies bumping together during handling or
other abnormal impacts to the die face.
Bus Bar
A rigid electric conductor in the form of a bar.
Butt
The unextruded portion of the billet remaining in the container after the extrusion cycle is completed. The
butt varies in thickness depending upon the alloy, die configuration, and extruded profile characteristics.
Butt End
The residual portion of an extrusion billet that is not formed through the die at the end of the extrusion
cycle.
Butt Weld

The welding of two sections that butt against each other, end to end.
CAD
Computer Assisted Design. The use of computer programs to generate, analyze and modify designs.
Extrusion dies and their supporting tools, for example, may be designed with the aid of computers.
CAM
Computer Assisted Manufacturing. The use of computers to monitor, regulate and control manufacturing
processes.
Cap
The outer part of a hollow die, which shapes the outside of a hollow extrusion.
Cap Bearings
The surfaces in the aperture of a hollow die which form the outside contour of a hollow extrusion. These
surfaces are located on that part of a hollow die which fits against the web or bridge base of the mandrel
and are on the same plane as the mandrel bearing. See Bearings .
Cast
To form a molten material into a desired shape by pouring into a mold and letting it harden.
Casting Alloy
An alloy formulated for casting.
Caustic
(Sodium Hydroxide, NaOH and derivatives). The active ingredient in an alkaline bath, generally with a pH
higher than 10, which removes aluminum from used extrusion dies by etching. The primary ingredient,
Caustic Soda (NaOH), dissolves the aluminum alloy by chemical reactions with no affect on the die steel.
Cavity
See Prechamber , Pocket , Piastrina , and Weld Pocket. An area in the entry side of the die which serves to
control flow of metal and in a solid die it permits a profile to be continuously extruded as metal from the
succeeding billet face is welded to the previous rear face remaining in the cavity after shearing. The
pocket generally follows the contour of the profile with milled depths varying from 0.040" to 1" or more
depending upon its function.
Cell
In aluminum production: the electrolytic reduction cell, commonly called a pot , which alumina dissolved
in molten cryolite is reduced to metallic aluminum. A series of cells connected electrically is called a pot

line.
Center
The difference in thickness between the middle and edges (average) of a sheet.
Chalking
A white powdery deposit on the surface of the exposed paint film caused by weathering.
Chamfer
A bevel at the apex of an angle on a machined part to allow clearance and prevent interference when
assembled with another machined part. The interference may occur from dirt, burrs, or incidental marring
of the die surface. A chamfer aids in the assembly of closely fit machined parts. Large chamfers are
sometimes used on the webs of hollow die entry ports to reduce the initial contact area between die and
billet.
Chatter
A surface defect consisting of alternating ridges and valleys at right angles to the direction of extrusion.
Chatter Mark
Numerous intermittent lines or grooves that are usually full width and perpendicular to the extrusion
direction.
Chemical Milling
Removing metal from a piece by controlling chemical etching.
Chemical Polishing
Improving the surface luster of metal by chemical treatment.
Choke
The angle filed on a bearing surface at the point where bearing and die face meet (where aluminum
enters aperture). Choke length and choke angle may vary independently. The angle of choke generally
falls between 1 2 degrees to 5 degrees.
Circumscribed Port Entry
An imaginary circle defining the maximum port entry for a given container liner where this diameter is
typically approximately 75% to 90% of the die diameter.
Circumscribing Circle

The smallest circle that will completely enclose the cross section of an extruded shape.
Cladding
A protective layer of pure aluminum or appropriate alloy to increase corrosion resistance and/or to allow
for brazing, applied to the surface of aluminum.
Cleanout Block
A circular tool or block used for scraping the aluminum skull from the container liner's inside wall. The
cleanout block diameter is greater than that of a dummy block and is sometimes called a scavenger block
or cleanout disk.
Cleanout Plate
Is similar to a cleanout block except that it is made from 2 or 3/4 inch mild steel plate.
Coating
Continuous film on the surface of a product.
Coating, High or Low
Cobble
(1) A jamming of the mill by aluminum product while being rolled. (2) A piece of aluminum which for any
reason has become so bent or twisted that it must be withdrawn from the rolling operation and scrapped.
Coefficient of Thermal Expansion
The relative rate at which a substance expands on heating, compared to a standard rate.
Cold Working
Plastic (i.e., permanent) deformation of metal at such temperature and rate that strain-hardening occurs.
Coloring
A finishing process, or combination of processes, which alters the appearance of an aluminum surface via
coating, chemical, and/or mechanical operations.
Composite Alloy
An aluminum alloy containing relatively large amounts of two or more other elements.
Composite Joint
A joint that is both welded and joined mechanically.

Compressive Strength
Strength to resist outside pressure (as distinguished, for example, from bending or stretching forces).
Concentricity
Conformance to a common center as, for example, the inner and outer walls of round tube.
Condenser Tube
The term Heat-Exchanger Tube is preferred, unless specific reference to a condenser application is
intended and purpose is to dissipate heat as efficiently as possible.
Conductivity
The ability of a substance to transmit heat, light or electricity. Aluminum has high electrical and thermal
conductivity, making it useful in a wide range of electrical and heat-exchanging applications.
Conduit
A tube used to protect electric wiring. See also Tubing, Electrical Metallic .
Conduit, Rigid
Conduit having dimensions of ANSI Schedule 40 pipe in standardized length and threaded ends.
Container
The steel cylinder, usually fitted with a removable liner, having an inside diameter slightly larger than the
billet to be extruded which holds and confines the billet during the extrusion cycle. Its length may vary
with the press tonnage rating and manufacturer.
Container Liner
The removable, replaceable cylindrical unit of press tooling which holds or confines the billet during the
extrusion cycle.
Container Seal
The interface between the container and the die. There must be sufficient clearance between the outer
edge of the die port and the inner edge of the container opening to prevent extrusion of the billet skin or
skull.
Container Wall Clearance
The difference in dimensions between the billet diameter and container liner internal diameter.

Contour
That portion of the outline of a transverse cross-section of an extruded profile that is represented by a
curved line or curved lines.
Contour Correction Rolling
An operation in which the extrusion is passed between rollers to adjust profile dimensions so that
specified tolerances in angularity, cross-sectional space dimensions, flatness, and contour are achieved.
Bow and twist may also be minimized or eliminated by contour rolling.
Conversion Coating
A chemical layer formed on the metal in the pretreatment process which aids in paint adhesion and
corrosion resistance.
Corrosion
The deterioration of metal by chemical or electrochemical reactions with substances in its environment.
Corrosion, Galvanic
Corrosion associated with the current of galvanic cell consisting of two dissimilar conductors in an
electrolyte or two similar conductors in dissimilar electrolytes. Aluminum will corrode if it is anodic to the
dissimilar metal.
Corrosion, Pitting
Localized corrosion resulting in small pits or craters in a metal surface.
Corrosion, Water Stain
Superficial oxidation of the surface with a water film, in the absence of circulating air, held between
closely adjacent metal surfaces.
Coupon
A piece a metal from which a test specimen may be prepared.
Covering Area
Yield expressed in terms of a given number of square inches in a pound. For metric units, use square
meters per kilogram.
Cratering
A paint film defect appearing as small, round bare spot on the painted part. This may be caused by
gassing, incompatability, or silicones.

Crazing
A macroscopic effect of numerous surface tears, transverse to the rolling direction, which can occur when
the entry angle into the cold mill work rolls is large.
Crease
A sharp deviation from flat in the sheet which is transferred from processing equipment subsequent to
the roll bite.
Creep
The strain in a metal that results from continuing constant stress.
Crosshatch
Test to demonstrate adhesion characteristics of a paint or powder coated surface, performed by scribing a
crosshatch pattern at specified intervals.
Cryogenic
Pertaining to very low temperatures. Aluminum gains strength as temperature is reduced, making it an
appropriate material for cryogenic applications.
Cure
The process of converting a liquid paint to a solid, durable film, usually accomplished by the action of heat
and catalysts.
Curl
An undesirable condition caused by uneven rates of absorption or evaporation of moisture, uneven rates
of contraction or expansion, or internal stresses in the material. Curl is most prevalent in laminated
structures where the components have differing physical properties.
Dead Metal Zone
An area of inactive metal that generally remains dormant and stagnant throughout the extrusion process.
These zones are inherent to the process and are normally found inside the mandrel of a hollow die and in
direct extrusion inside the container adjacent to the die.
Dead Soft
Fully annealed, the softest form of a metal, the temper of aluminum.
Deburring
Removing burrs, sharp edges, or fins from metal parts by filing, grinding, or tumbling.

Deep Drawing
Forming a deeply recessed part by forcing sheet metal to undergo plastic flow between dies, usually
without substantial thinning of the sheet.
Defect
A defect is anything that renders the aluminum unfit for the specific use for which it was ordered.
Deflection
The distortion or bending of the die or components thereof. Insufficient support of die will cause it to
deflect, lessening the effectiveness of the bearing; also termed dishing, caving, and sagging.
Density
Weight per unit of volume (for example pounds per cubic foot). The density of aluminum is only about
one-third that of steel, and this weight-saving characteristic is one of aluminum's best-known advantages.
Dent
A sharply defined surface impression on the metal which may be caused by a blow from another object.
Dent, Repeating
Repeating depression caused by a particle adhering to a rotating roll over which the metal has passed.
Depth of Fusion
The depth to which base metal melts during welding.
Detection
A past-oriented strategy that attempts to identify unacceptable output after is has been produced and
then separate it from the good output.
Diametrical Temperature
The temperature of a circular object, measured from the center to the edge (average).
Die
In extrusion a tool with an opening through which heated aluminum is forced by pressure, taking on that
cross-sectional shape.
Die Assembly
In an extrusion press, the die and its associated tooling.

Die Face
The surface of an extrusion die facing the billet.
Die Holder
The press component which is located between the container and press platen to retain the extrusion die
and its components. It may take many different forms and added functions depending upon its design.
The holder can be unlocked and the die withdrawn for the removal of butt and scrap.
Die, Hollow
A steel extrusion tool which forms extruded closed profiles containing one or more voids such as
rectangular tubing. The tool generally consists of a die cap which generates the outer surface of the profile
and the mandrel or core which generates the inside contour. Hollow or semi-hollow profiles are produced
usually with either bridge, porthole or spider (taper seal) type dies or variants thereof. Extruded sections
produced on such dies have seams or longitudinal weld lines, due to the metal flow around the web
supports (bridges) that hold the mandrel. The latter determines the inside contour of the profile being
extruded. After flowing around the supports, the metal is fused in a weld chamber before passing through
the die (die cap) proper.
Die Kinks
The sectional irregularities caused by an uneven extrusion rate, or by material either not being led from
the die in a uniform manner or being adequately supported.
Die Lines
A longitudinal depression or protrusion formed on the surface of drawn or extruded material. Die lines are
present to some degree in all extrusions and are caused by a roughening of the die bearing.
Die Number
The number assigned to a die for identification and cataloging purposes, and which usually is assigned for
the same purpose to the product produced from that die.
Die Ring
A cylindrical sleeve that holds the die and backer in axial relationship to each other.
Die, Semihollow
A circular steel extrusion tool which forms an open profile with a high tongue ratio. Generally this tongue
ratio is greater than three to one. This type of die is similar to a hollow die. The tongue is protected by a
web or bridge which reduces the billet pressure. When possible, for maximum support the tongue should
be bolted to the web.
Die Slide

The extrusion press component located between the container and press platen. It supports, aligns to the
press and retains the tooling (die, backer, bolster, sub-bolster, etc.) for the specified profile, as a unit. It
may be designed to facilitate butt shearing and to provide die accessibility for replacement and repairing.
Die, Solid
A steel disk, with one or more orifices or apertures, of similar cross-section and contour as the desired
product, through which metal is forced forming open profiles such as bar, channel and angle.
Die Stop
A defect resembling a weld around the entire extruded section, caused by stopping a press during
extrusion and then restarting it.
Die Tool Assembly
The various components making up the assembly within the tool carrier or Die Slide. A typical example
would be (from front to rear): die and backer enclosed in a die ring, bolster and possibly a sub-bolster or
spacer.
Die Weld
A region in extruded hollow profiles created by two streams of metal within the die joining themselves in
the weld chamber around the mandrel of a hollow type die. Die welds are generally present in all
extruded hollow profiles and in most cases are not visible.
Dimensional Allowance
The specified difference in size between mating parts.
Dimensional Stability
The ability of an object to retain its original shape under varying physical conditions.
Disc
(1) A circular blank fabricated from plate, sheet, or foil, from which a central concentric area has been
removed. (2) An electrostatic paint application shaped like a disc which atomizes paint utilizing centrifugal
force off the edge of the disc.
Discontinuities
Abnormalities such as cracks, laps, folds, cold shuts, inclusions, segregation and porosity. Voids of any
kind.
Distortion
Any deviation from the desired shape or contour.

Dove-tail
An interlocking connection frequently used for the assembly of interconnecting extrusions; it is assembled
by a sliding action.
Draft
Taper on the sides of a die or mold impression to facilitate removal of forgings, castings or patterns from
dies or molds.
Drawing Stock
A hot worked intermediate solid or tubular product of uniform cross section along its whole length,
supplied in coils and of a quality suitable for drawing into tube or wire.
Drawn Product
A product formed by pulling material through a die.
Ductility
The property that permits permanent deformation before fracture by stress in tension.
Duct Sheet
Coiled or flat sheet in specific tempers, widths and thicknesses, suitable for duct applications.
Dummy Block
A tight-fitting steel block placed between the ram and the billet in an extrusion press to prevent metal
from leaking backward along the ram during extrusion.
E.C. (or EC) Alloy or Grade
Electrical conductor aluminum, an alloy specifically formulated for good electrical conductivity; it is about
99.5 percent aluminum. Typically AA1350 alloy.
EDM (Electrical Discharge Machining)
A process that utilizes high frequency pulsating DC current in the presence of a dielectric to erode tool
steel. The Ram or Plunge EDM process is utilized for burning relief into the back of the die, or burning the
shape into the mandrel core. Wire EDM is utilized to cut die openings in dies.
Eccentricity
Deviation from a common center, as, for example, the inner and outer walls of a round tube. The
difference between the mean wall thickness and minimum or maximum wall thickness at any one cross
section. The permissible degree of eccentricity can be expressed by a plus and minus wall-thickness

tolerance.
Edge, Broken (Cracked)
Edge(s) containing crack, split, and/or tear which may be caused by an inability to deform without
fracturing.
Edge, Damaged
Edge of a coil that has been bent, torn, or scraped by an object.
Edge, Dropped
A continuous, downward edge deflection.
Edge, Liquated
Surface condition remaining after portions of a side of an as-cast rolling ingot deforms enough during hot
rolling to become top and/or bottom surface(s) of the rolled product at an edge.
Elastic Deformation
A temporary dimensional change induced by stress. The body returns to its original dimensions when the
stress is removed if its elastic limit has not been surpassed.
Elasticity
The ability of a material or body to return to its original shape and dimensions after being deformed by
stress.
Elastic Limit
The maximum stress that a body can withstand without permanent deformation.
Electrical Conductivity
The capacity of a material to conduct electric current. For
aluminum, this capacity is expressed as a percentage of the International Annealed Copper Standard
(IACS), which has a resistivity of 1/58 ohm-mm2/meter at 68 º F and an arbitrarily designated conductivity
of unity.
Electrical Resistivity
The electrical resistance of a body of unit length and unit cross-sectional area or unit weight. The value of
1/58 ohm-mm2/meter at 68 º F is the resistivity equivalent to the International Annealed Copper Standard
for 100 percent conductivity. This means that a wire of 100 percent conductivity, 1 meter in length and 1

square millimeter in cross-sectional area would have a resistance of 0.017241 ohms at 68 degrees F.
Electrochemical
Pertaining to chemical reactions induced by an electric current such as electrolysis or electroplating.
Electrodeposition
Application of a coating by immersing the parts in a bath of water containing resin, electrolytic stabilizers
and pigments, an electric current is passed through the bath, using the parts as anodes, plating them with
resins and color.
Electrolysis
The separation of a chemical compound into its components by passing an electric current through it.
Electrolyte
A dissolved or fused substance capable of conducting an electric current, examples include the molten
solution electrolyzed in an aluminum reduction cell, or the acid solution in a wet-cell battery.
Electroplating
Depositing a thin layer of a metal, usually copper, tin or silver, on the surface of another metal by
electrifying the metal to be plated in an electrolyte containing the plating metal.
Electrostatic Application
A system of applying paint in which the paint droplets or powder particles are given an electrical surface
charge resulting in their attraction to a grounded workpiece. Higher transfer efficiency, better wrap and
penetration, finer atomization and less overspray are distinct advantages.
Electrostatic Spraying
Application of a coating by applying a static electricity charge to the droplets of a spray and an opposite
charge to the part being sprayed, which then attracts the droplets directly to its surface.
Elongation
The percentage increase in distance between two gauge marks that results from stressing the specimen in
tension to fracture. The original gauge length is usually 2 inches for flat specimens and round specimens
whose diameter is 0.5 inch, or four times the diameter for specimens where that dimension is under 0.5
inch. Elongation values depend to some extent upon size and form of the test specimen. For example, the
values obtained from sheet specimens will be lower for thin sheet than for thicker sheet.
Embrittlement
Reduction in the normal ductility of a metal, due to physical or chemical change.

Emissivity
The relative ability of a material to radiate energy per unit of surface area expressed as a ratio to the
radiation rate of an ideal black body of identical area and temperature.
Endurance Limit
The limiting stress below which a material will withstand a specified large number of cycles of stress.
Equivalent Round
The diameter of a circle having a circumference equal to the outside perimeter of other than round tube.
Etchant
Chemical solutions used to change the metal surface for cleaning, examination or for finishing.
Etching
Shaping or texturing a metal surface by controlled corrosive action.
Exposed Surface
Any face of an extruded profile which is exposed to view or other critical end-use aspects.
Extraction
The general process of separating a metal from its ore.
Extrude
To force material through a die by pressure.
Extruded Length
The length of a profile (section) extruded in a single push.
Extruded Profile
A profile usually of constant cross section brought to final dimensions by extruding. The preferred term
describing an extrusion formerly termed an extruded shape .
Extruded Shape
Any aluminum extrusion other than rod, bar, or tube.
Extrusion Billet

The starting stock for the extrusion operation. Extrusion billet is a solid or hollow form, commonly
cylindrical and is the length charged into the extrusion press cylinder. It is usually a cast product but may
be a wrought product or powder compact.
Extrusion Butt End Defect
A longitudinal discontinuity in the extreme rear portion of an extruded product, which is normally
discarded.
Extrusion Defect
A cone-shaped abnormality such as a cavity in an extruded product (ring in a hollow profile or tube)
formed in the extreme rear portion, if extruded too far.
Extrusion (Direct)
The method of extruding wherein the die and ram are at opposite ends of the billet and the product and
ram travel in the same direction.
Extrusion (Indirect)
The method of extruding where the die is at the ram end of the billet and the product travels through the
hollow ram and in the opposite direction.
Extrusion Ingot
A cast form that is solid or hollow, usually cylindrical, suitable for extruding. See also Fabricating Ingot.
Extrusion Ingot (Scalped)
A cast solid or hollow extrusion ingot which has been machined on the outside surface. Scalped billets are
normally used with the indirect extrusion process.
Extrusion Log
The starting stock for extrusion billet. Extrusion log is usually produced in lengths from which shorter
extrusion billets are cut.
Extrusion Pressure
That force employed to cause billet metal flow through a die.
Extrusion Seam
A region in extruded hollow profiles observed after creating two streams of metal and rejoining them
around the mandrel of a porthole or bridge die.
Extrusion Speed

The velocity or rate at which an extrusion exits from the die usually expressed as feet per minute.
Extrusion Tools
The auxiliary equipment required to produce extrusions, which is not an integral or fixed part of the
extrusion press. Tools consist principally of container, dies, die backers, dummy blocks, etc.
Fabricate
To work a material into a finished state by machining, forming or joining.
Fabricating Ingot
A cast form suitable for subsequent working by such methods as rolling, forging, extruding, etc.
Fat Edge
An application defect where too much paint accumulates along a square edge or corner of the part, often
evidenced by higher gloss or blistering.
Fatigue
The tendency for a metal to break under conditions of repeated cyclic stressing considerably below the
ultimate tensile strength.
Fatigue Strength
The maximum stress that a metal can sustain for a specified number of cycles without failure.
Faying Surface
The surface of a piece of metal in contact with another to which it is, or will be, joined.
Feed
Pertains to the amount of aluminum directed to a specific area of an extrusion die, generally achieved by
adjusting the port size.
Feeder Die
A die design which permits through certain design features the extrusion of profiles normally too large for
an extrusion press if conventional means were employed or to assist in extrusion of difficult profiles.
Feeder Plate
A plate employed in front of the extrusion die to alter the metal billet dimensions permitting extrusion of
larger dimensioned product than normally possible or to assist in extrusion of difficult profiles.

Ferrous
Pertaining, derived from, or based on iron.
Filler Metal
Metal added in making a brazed, soldered or welded joint.
Fillet
Generally, a concave junction where two surfaces meet.
Fillet Weld
A weld, approximately triangular in cross section, joining two surfaces at right angles to each other.
Film Thickness
The depth of applied coating, expressed in mils, i.e. 1/1000 inch.
Fin
A thin projection on a forging or casting resulting from trimming or from the metal under pressure being
forced into hairline cracks in the die or around die inserts.
Fin Stock
Coiled sheet or foil in specific alloys, tempers, and thickness ranges suitable for manufacture of fins for
heat-exchanger applications.
Finish
In extrusion, the condition, quality or appearance of the final aluminum surface. Aluminum can be finished
in a very wide variety of textures and colors.
Finishing
Usually secondary operations applied to extrusions to improve product dimensionally or change surface
condition (etching) or color (anodizing, plating, painting, buffing, etc).
Fisheye
A defect in the paint film appearing as a circular depression resembling a crater but not revealing bare
substrate.
Fishtail Die Extruding
The utilization of a transition piece of tooling between the container and die (feeder plate), whereby a

conventional round billet is forced to assume the elliptical shape of the cavity and opening in the
transition piece, before reaching the aperture of the die proper, thus allowing sections to be extruded that
are much wider than the container. Such dies can also be made in one piece (feeder die), incorporating
the same principles.
Fit
The range of clearance or interference between mating parts. The American Standards Association
recognizes 33 classes of fits ranging from loose sliding fit to tight force fit.
Fixed Dummy Block
A dummy block attached to the ram with self expansion capabilities.
Flag
A marker inserted adjacent to the edge at a splice or lap in a coiled product.
Flaking
A condition in coated sheet where portions of the coating become loosened due to inadequate adhesion.
Flash
A thin protrusion at the parting line of a forging or casting which forms when metal, in excess of that
required to fill the impressions, is forced between the die interfaces. Also, metal forced between
container and die due to improper seal.
Flash Line
A line left on a forging or casting where flash has been removed.
Flat Layout
The design method of locating the apertures in a die so that the major axis of each profile is parallel to
each other and may be mirrored.
Flatness
(1) For rolled products, a distortion of the surface of sheet such as a bulge or a wave, usually transverse to
the direction of rolling. Often described by location across width, i.e., edge buckle, quarter buckle, center
buckle, etc. (2) For extrusions, flatness (off contour) pertains to the deviation of a cross-section surface
intended to be flat. Flatness can be affected by conditions such as die performance, thermal effects and
stretching.
Flexibility
(1) The capability of a material to be curved, folded, or bent. (2) The ability of a paint to resist chipping,
peeling, or cracking after the substrate has been bent, twisted, bowed, or punched.

Floating (Fixed) Dummy Block
A fixed dummy block design which has self alignment capabilities.
Flow
A term used when referring to the movement of aluminum through the die during the extrusion process.
Flow Line
(1) Lines on the surface of painted sheet, brought about by incomplete leveling of the paint. (2) The line
pattern revealed by etching, which shows the direction of plastic flow on the surface or within a wrought
structure.
Flow Through
A forging defect caused when metal flows past the base of a rib resulting in rupture of the grain structure.
Flow Coating
Painting a part by directing streams of paint against it and letting excess paint drain into a tank for
recirculation. Complicated shapes can be painted this way, but they must be correctly positioned for paint
drainage.
Fluorocarbon
A stable carbon compound in which hydrogen from a hydrocarbon has been replaced by fluorine. Coatings
containing the fluorocarbon PVF2, among the most stable known, are applied by roll coating or spray.
Fluxing
The removal of impurities from molten metal in a crucible, furnace, or scrap remelting furnace by bubbling
a mixture of gasses up through the melt. The combined chemical and mechanical action carries oxides and
other impurities to the top of the melt, forming a scum or dross that is skimmed off.
Formability
The relative ease with which a material can be shaped through plastic deformation.
Forming
Changing the shape of metal except by shearing or blanking without intentionally altering its thickness.
Fracture
A generic term for measure of resistance to extension of a crack.

Frictional Heat
That heat imparted to the extrusion or billet as the result of metal movement within the container or
through the die.
Galvanic Corrosion
Deterioration of a metal caused by the electric current produced when two unlike metals are in contact
under certain condition.
Galvanizing
An undesirable grainy or spangled condition on the surface of etched or anodized extrusions. This
condition is not obvious in mill finish aluminum extrusions but can be revealed by etching or anodizing.
Gas Entrapment
A situation that occurs when air is trapped inside the die or container, usually during the dead cycle, as a
result of sloppy butt shearing or the upsetting of the billet inside the container.
Gasket
A relatively soft sealer often of cork, asbestos, or rubber placed in a joint between two metal parts to
prevent leakage through the joint.
Gauge
A term previously used in referring to the thickness or diameter of a wrought product. Thickness or
diameter is preferred in dimensional descriptions.
German Mandrel
Fixed mandrel.
Gloss
The degree to which a surface reflects light, generally, the smoother the surface, the higher the gloss.
Grain Flow
The directional characteristics of the metal structure after working, revealed by etching a polished section.
Grain Size
A measure of crystal size usually reported in terms of average diameter in millimeters, grains per square
millimeter, or grains per cubic millimeter.
Grinding

Removing material from a workpiece with an abrasive wheel.
Hard Coat Anodizing
A combined electrical and chemical finishing process for aluminum that produces a hard, colored,
protective film on the surface.
Hardening
Increasing the hardness of metal by suitable treatment, usually involving heating and cooling.
Hardness
Resistance to plastic deformation, usually by indentation. The term may also refer to stiffness or temper,
or to resistance to scratching, abrasion or cutting.
Hardness, Brinell
A measure of hardness (resistance to indentation) obtained by applying a load--through use of a ball
indenter--and measuring the permanent impression in the material. The hardness value of aluminum
alloys is obtained by applying a load of 500 kilograms to a ball 10 millimeters in diameter for 30 seconds;
the applied load (in kilograms) is divided by the spherical area of the impression (in square millimeters).
Hardness, Pencil
A method of evaluating hardness/adhesion using graded drawing
Hardness, Rockwell
An indentation hardness test based on the depth of penetration of a specified penetrator into the
specimen under certain fixed conditions.
Heat-affected Zone
That portion of the base metal in welding, brazing or flame cutting whose microstructure and physical
properties have been altered by the heat.
Heat Checking
Horizontal cracks or separation of material usually observed initially on the inside of hollow profiles.
Heat-Treatable Alloy
An aluminum alloy that can be hardened to produce desired properties by a controlled cycle of heating
and cooling.
Heat Treating
Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties.

Commonly used as a shop term to denote a thermal treatment to increase strength. Heating for the sole
purpose of hot working is excluded from the meaning of this definition -- see Solution Heat Treating .
Aging .
Hiding
The ability of a paint to mask the color or pattern of the substrate it covers.
High-Solids Coating
Coatings greater than 40% solids by volume, thereby reducing solvent emissions during the application.
Hinge Joint
A joint which, when assembled, allows its parts to rotate relative to each other without separating. Hinge
joints are extruded as relatively loose slip-fit joints with an open-sided ball-in-socket design.
Hollow Billet
A billet prepared for extruding seamless tube or pipe. The outside diameter may be scalped and the inside
diameter may be bored or cast hollow to assure sound metal.
Hollow Dies
Are extrusion tools capable of forming profiles with voids where such dies are typically classified as either
bridge, porthole or spider types. Extruded sections produced on these dies have one or more seams or
longitudinal weld lines, due to metal flow around the supports that hold the stub mandrel. The stub
mandrel determines the inside contour of the section being extruded. After passing around the supports,
the metal is fused in a weld chamber before passing through the die proper.
Hollow Profile
An extruded profile, any part of whose cross section completely encloses a void.
Hollow Shape
An extruded shape, any part of whose cross section completely encloses a void.
Homogenizing
Is a process whereby ingots are raised to temperatures near the solidus temperature and held at that
temperature for varying lengths of time. The purposes of this process are to (1) reduce microsegregation
by promoting diffusion of solute atoms within the grains of aluminum and (2) Improve workability.
Hook
An abrupt deviation from straightness. Hook can be caused by non-uniform metal flow during
breakthrough. See also Bow .

Horse Shoe
Is a hardened tool steel, horse shoe shaped device intended to hold, position and retain the die ring in the
die slide or tool carrier.
Hot Forming
Working operations, such as bending, drawing or forging, performed above the softening temperature of
the metal.
Hot Hardness
The hardness of metals at elevated temperatures. For example in the case of H-11, H-12, and H-13 hot
work tool steel hot hardness at 900 º F is lower than at room temperature.
Hot Tears
Transverse surface scars or separations along the length of the extruded profile caused by excess speed
and/or temperature.
Hot Shortness
A condition of the metal at excessively high working temperatures characterized by low mechanical
strength and a tendency for the metal to crack rather than deform.
Hot Spot
Dark gray or black surface patches appearing after anodizing. These areas are usually associated with
lower hardness and coarse magnesium silicide precipitate caused by non-uniform cooling after extrusion.
Hot Working
Plastic deformation of metal at such temperature and rate that strain hardening does not occur.
Housing
Part of a hollow die that replaces the die ring and is another term for a mandrel when referring to a selfcontained
die.
Housing Face
The surface on the entry of a hollow die. On the aluminum entry side one usually finds ports while on the
exit side is located the sealing face.
Hydraulic Press
A press in which the ram is activated by fluid pressure.
Impact

A part formed in a confining die from a metal slug, usually cold, by rapid single stroke application of force
through a punch, causing the metal to flow around the punch and/or through an opening in the punch or
die.
Impact Strength
The ability of a material to withstand shock loading.
Inclusion
Foreign material in the metal or impressed into the surface.
Inclusion, Stringer
An impurity, metallic or non-metallic, which is trapped in the ingot and elongated subsequently in the
direction of working. It may be revealed during working or finishing as a narrow streak parallel to the
direction of working.
Inflation
The term associated with hollow profiles that extrude convex rather than flat.
Ingot
A cast form suitable for remelting or fabricating. See Fabricating Ingot , Extrusion Ingot , Forging Ingot .
Insulator
A material that resists the flow of heat, sound, electricity or another form of energy.
Interference Fit
The class of fit in which a mating part is deliberately made slightly oversize for the part into which it will be
inserted.
Interleaving
The insertion of paper or application of suitable strippable coatings between layers of metal to protect
from damage.
Interlocking Joint
A joint in which a curved projection on one part is inserted by a rotating motion into a similarly curved
receiving groove on the other part. The parts cannot then be separated by straight-line motion.
Joint Efficiency

The strength of a welded joint expressed as a percentage of the strength of the unwelded base metal.
Kerf
The notch or slit made by a saw or torch when cutting.
Key-locked Joint
A joint with two or more primary elements which are locked together only when an additional specialized
part, the key is inserted to prevent them from separating.
Keyway
A slot in the shaft of a mechanical drive system that provides a means of locking a gear or other part onto
the shaft.
Kink
An abrupt deviation from straightness. A kink can be caused by handling.
Lacquer
A solution of natural or synthetic resin in an organic solvent with modifying agents, suitable for protective
coatings. Lacquers may be clear or colored.
Lambda
The Greek letter, corresponding to the letter L, used as a symbol for the coefficient of heat conductivity,
the relative rate at which heat is transmitted through a material.
Lamination
An internal crack or separation aligned parallel to the extrusion direction, usually caused by contaminants
that feed into the metal flow during the forming process or by cracked billets.
Lap Joint
A joint formed with one member overlapping the other; the simplest type of nesting joint.
Lapping
A method of finishing metal to produce a very smooth, highly accurate surface.
Layout Sample
A prototype forging or a cast used to determine conformance to designed dimensions.
Lead-out (equipment context)

The initial adjustable and removable section of runout table which is usually stationary (non-activated).
Lead-out (process context)
The initial portion of an extruded profile.
Light Walls
Undersized wall dimensions often caused by shifting or caving of mandrel or housing section of hollow die.
Lineal Temperature
Temperature along the extruded profile's length.
Linearity
The extent to which a measuring instrument's response is proportional to the measured quantity.
Line, Flow
The line pattern which shows the direction of flow on the surface.
Line, Looper
Closely spaced symmetrical lines on the surface of metal which has undergone non-uniform deformation,
usually in a drawing operation.
Liner
The slab of coating metal that is placed on the core alloy and is subsequently rolled down to clad sheet as
composite.
Liquation
The bleeding of the low-melting constituents through the solidified ingot surface.
Location
A general concept for the typical values or central tendency of a distribution.
Lock
A condition in which the parting line of a forging is not all in one plane.
Log
The starting stock for extrusion billet. Extrusion log is usually produced in lengths from which shorter

extrusion billets are cut.
Long Transverse Direction
For plate, sheet and forgings, the direction perpendicular to the longitudinal direction which is also at
right angles to the thickness of the product. See also Longitudinal Direction .
Longitudinal Direction
The direction of major metal flow in a working operation.
Lot , Heat Treat
Material usually of the same mill form, alloy, temper, section and size traceable to one heat-treat furnace
load (or extrusion charge or billet in the case of press heat-treated extrusions) or, if heat treated in a
continuous furnace, charged consecutively during an 8-hour period.
Lot , Inspection
(1) For non-heat treated tempers, an identifiable quantity of material of the same mill form, alloy, temper,
section and size submitted for inspection at one time. (2) For heat treated tempers, an identifiable
quantity of material of the same mill form, alloy, temper, section and size traceable to a heat treat lot or
lots and submitted for inspection at one time. (For sheet and plate, all material of the same thickness is
considered to be of the same size.)
Lube, High
Lubricant limit exceeds the maximum agreed upon limit measured in weight per unit area.
Lube, Low
Failure of the lubricant to meet the agreed upon minimum limit measured in weight per unit area.
Lubricant
Any of a number of liquids or semi-solids such as oil, kerosene, grease, lard, fat, soap, tallow and wax used
on metal to reduce friction and binding during extruding or forming operations.
Machinability
The relative ease of working a metal with machine tools. Aluminum has good machinability.
Machining
The quantified removal of metal from the die using a cutting tool or erosion through the electrical
discharge process.
Main Cylinder

The chamber of an extrusion press into which hydraulic fluid is pumped to generate the desired ram
pressure and movement.
Mandrel
The fixed or floating projection positioned in the die opening that forces metal to flow around it. The wall
thickness of the extrusion is determined by the difference in the dimensions of the die aperture and the
mandrel.
Mark
Damage in the surface of the product whose name is often described by source.
Mark , Arbor
Surface damage in the vicinity of a coil ID caused by contact with a roughened, damaged or non-circular
arbor or by the end of the product.
Mark , Bearing
A depression in the extruded surface caused by a change in bearing length in the extrusion die.
Mark , Carbon (Graphite)
Gray or black surface marking caused by contact with carbon runout blocks.
Mark , Chatter (roll or leveller)
Numerous intermittent lines or grooves that are usually full width and perpendicular to the rolling or
extrusion direction.
Mark , Handling
(1) For rolled products, an area of broken surface that is introduced after processing. The mark usually has
no relationship to the rolling direction. (2) For extrusions, damage that can be imparted to the surface
during handling operations.
Mark , Rub
A large number of very fine scratches or abrasions. A rub mark can occur by metal-to-metal contact,
movement in handling and movement in transit.
Mark , Stop
A bank-like pattern around the full perimeter of an extruded section and perpendicular to its length. A
stop mark occurs whenever the extrusion process is suspended.
Mark , Stretcher Jaw

A cross hatched appearance left by jaws at the end(s) of metal that has been stretched. These marks are
seen if insufficient metal has been removed after the stretching operation.
Mark , Traffic
Abrasion which results from relative movement between contacting metal surfaces during handling and
transit. A dark color from the abrasively produced aluminum oxide is usually observed. A mirror image of a
traffic mark is observed on the adjacent contacting surface.
Maximum Speed
The fastest practical extrusion rate or velocity which is related to the extrusion press ram's velocity. The
formula is: Max. ram speed (ipm) x reduction ratio x 12 = maximum speed (ft/min).
Mechanical Properties
Those properties of a material that are associated with elastic and inelastic reaction when force is applied,
or that involve the relationship between stress and strain; for example, modulus of elasticity, tensile
strength, endurance limit. These properties are often incorrectly referred to as physical properties.
Mechanical Working
Subjecting metal to pressure exerted by rolls, dies, presses, or hammers to change its form or to affect its
structure and its mechanical and physical properties.
Metal Dimension
Any dimension, through a part of an extruded cross-sectional shape, whose length includes at least 75
percent metal, versus open space.
Metal Entry
The location where the aluminum alloy enters the port opening of a hollow die or the initial opening of a
solid die.
Metal Flow
The manner in which metal moves both in the container and through the extrusion die.
Mil
A unit of length; 0.001 inch.
Mild Steel
Steel with a maximum carbon content of about 0.25 percent.
Mill Finish

Mill finish is the finish obtained by standard extrusion practices and produced without the aid of any
subsequent operations. This finish generally varies from a structural finish with surface imperfections to
an architectural finish with uniformly good appearance.
Milling
Removing metal with a machine tool something like a rotary chisel.
Mini Insert Die
Small self-contained dies that fit into a housing.
Modulus of Elasticity
The ratio of stress to corresponding strain throughout the range where they are proportional. As there are
three kinds of stresses, so there are three kinds of moduli of elasticity for any material -- modulus in
tension, in compression, and in shear.
Multivoting
A technique used in the expression of opinions regarding several topics.
Natural Aging
See Aging .
Nesting Joints
A general class of joints with mating elements that serve to align adjoining parts with little or no selflocking
action.
Nitriding
The introduction of nitrogen into the surface of tool steels by holding at a suitable temperature in contact
with a nitrogenous material, usually ammonia, to produce a hard wear resistant case.
Nitrogen Shrouding
The process of injecting nitrogen, either liquid or gaseous, at the die openings to surround the emerging
extrusion in an environment high in nitrogen and low in oxygen. This delays the formation of oxides on the
exit edge of the die bearing providing a superior surface finish on the extrusion.
Nonferrous
Not containing iron; a generic term for metals other than iron and alloys not containing iron.
Nonfill

Failure of metal to fill a forging die impression.
Non-Heat Treatable Alloys
Aluminum alloys that are strengthened by cold working and not by heat treatment.
Notch Double Shear
An abrupt deviation from straight on a sheared edge. This offset may occur if the flat sheet or plate
product is longer than the blade for the final shearing operation.
O.D. (Outside Diameter)
The nominal overall measurement of tube or pipe diameter measured across its outer perimeter because
of variations in actual wall thickness, it does not necessarily indicate true dimensions at all location.
Off Contour
The deviation of a cross-section surface otherwise intended to be flat.
Off Gauge
Deviation of thickness or diameter of a solid product, or wall thickness of a tubular product, from the
standard or specified dimensional tolerances.
Offset-Yield Strength
Yield strength by the offset method is computed from a load-strain curve obtained by means of an
extensometer. A straight line is drawn parallel to the initial straight line portion of the load-strain curve
and at a distance to the right corresponding to 0.2 percent offset (0.002 in. per in. of gauge length). The
load reached at the point where this straight line intersects the curve divided by the original crosssectional
area (sq. in.) of the tension test specimen if the yield strength.
Opaque
Impervious to the transmission of light. Aluminum is opaque; even a thin aluminum foil completely blocks
the transmission of light.
Open Space Dimension
A dimension, across a part of an extruded cross-sectional shape which only partially encloses a space,
whose length includes more than 25 percent space, versus metal.
Operational Definition
A means of clearly communicating quality expectations and performance; it consists of 1) A criterion to be
applied to an object or to a group, 2) A test of the object or of the group, 3) A decision: yes or no; the
object or the group did or did not meet the criterion.

Orange Peel
(1) Surface roughening on formed products which occurs when large grains in the metal are present. (2)
An irregularity in the surface of a paint film resulting from the inability of the wet film to level out, or
become smooth after being applied, thus resembling the surface of an orange. This finish may be
considered desirable or a defect depending on the end use.
Orientation (Laying Out)
The placement of die openings for best profile attitude and consequent flow distribution.
Orifice
The opening in an extrusion die through which the material is extruded.
Oscillation
Uneven wrap in coiling and lateral travel during winding. Improper alignment of rolls over which the metal
passes before rewinding and insufficient rewind tension are typical causes. See also Telescoping .
Ovality
Deviation from a circular periphery, usually expressed as the total difference found at any one cross
section between the individual maximum and minimum diameters, which usually occur at or about 90
degrees to each other. Since ovality is the difference between extreme diameters, it is not expressed as
plus or minus.
Overbending
Bending metal through a greater angle than that required in the finished part, to compensate for the
tendency of the metal to spring part way back to its original shape.
Oxide
A chemical compound of oxygen with another element. Hydrated (water-including) iron oxide is called
rust; it does not cling tightly to the underlying metal, so the oxidation process is progressive and iron
easily rusts away. Aluminum oxide is a hard, transparent compound which clings tightly to the underlying
metal and protects it against further oxidation.
PSA
Abbreviation for a process known as Pressure Swing Absorption which produces gaseous nitrogen for
shrouding in the die area.
PSI (or P.S.I.)
Pounds per square inch a measure of pressure or mechanical load.
Pancake Die

A three piece hollow die composed of a die, backer and porthole, which shortens the feed length.
Parent Coil
A coil that has been processed to final temper as a single unit. The parent coil may subsequently be cut
into two or more smaller coils or into individual sheets or plates to provide the required width and length.
Parent Plate
A plate that has been processed to final temper as a single unit. The parent plate may subsequently be cut
into two or more smaller plates to provide the required width and length.
Parting Line
A condition unique to stepped extrusions where more than one cross section exists in the same extruded
shape. A stepped shape uses a split die for the minor or small cross section and after its removal another
die behind it for the major configuration. Slightly raised fins can appear on that portion of the shape
where the two dies meet.
Peen Gun
A tool used to hammer the surface of a die.
Pencil Hardness
A method of evaluting hardness/adhesion using graded drawing leads, often used as an indication of cure.
Permanent Set
The plastic (non-elastic) deformation or deformation above the elastic limit, remaining after the load is
removed.
Permeability
The passage or diffusion of a gas, vapor, liquid or solid through a barrier without physically altering it; the
rate at which this diffusion or passage occurs. Aluminum is essentially impermeable, an important factor
in its widespread use in containers and packaging.
Physical Properties
The properties, other than mechanical properties, that pertain to the physics of a material; for example,
density, electrical conductivity, heat conductivity, thermal expansion.
Piastrina
A pocket in the die cap of specified depth and distance from the bearing around the profile's contour
before the bearing that allows additional control of the metal flow. Sometimes termed a Forming Pocket.

Pick-Off
The transfer of portions of the coating from one surface of the sheet to an adjacent surface due to poor
adhesion of the coating.
Pickup
Small particles of oxide adhering to the surface of a product at irregular intervals.
Pigment
An insoluble coloring agent suspended in a fluid medium, as in inks, lacquers, and paints.
Pigment
A dry substanced dispersed uniformly in a paint to give color, opacity, or other special properties.
Pin Core
A replaceable mandrel core.
Pin Gauges
Precision machined pins used for measuring normally available as plus, minus and net size.
Pin Openings
A method commonly used for checking wall thickness consistency in a die using pin gauges.
Pinouts
The actual dimensions of a die opening measured with pin gauges.
Pinhole
(1) Minute hole in foil. (2) A small-sized void in the coating of a sheet or foil product. A typical cause is
solvent popping.
Pipe, Drawn
Pipe brought to the final dimensions by drawing through a die.
Pipe, Extruded
Pipe formed by hot extruding.
Pipe, Structural

Pipe, brought to final dimensions by extruding through a bridge-type die or by similar methods at the
option of the producer. (Typically used for structural, nonpressure applications.)
Pit
(1) A depression in the rolled surface which is usually not visible from opposite side. (2) A sharp
depression in the surface.
Plastic Deformation
Distortion that remains after removal of the load that caused it.
Plasticity
The ability of a material to be deformed extensively without rupture.
Plastisol
A coating incorporating polyvinyl chloride (PVC), used mainly on such products as industrial building
sheets and residential siding, and sometimes formulated for spraying. Plastisols require application of a
special primer to achieve proper bonding to aluminum.
Plate
A rolled product that is rectangular in cross section and with thickness not less than 0.250 inch with
sheared or sawed edges.
Plate Circle
Circle cut from plate.
Plate, Alclad
Composite plate comprised of aluminum alloy core having on both surfaces (if on one side only, Alclad
One Side Plate) a metallurgically bonded aluminum or aluminum alloy coating that is anodic to the core,
thus electrolytically protecting the core against corrosion.
Platen Pressure Ring
A hardened tool steel ring inserted into the platen to support the die and support tools.
Platen Ring Opening
The recessed opening in the rear face of the front extrusion press platen into which the pressure ring is
inserted to provide support for the tool stack.
Polishing
Smoothing a metal surface, usually by rubbing with fine abrasives. A mechanical finishing operation for

the purpose of producing a gloss or luster on the surface of a product.
Polymer
A chain-like compound of high molecular weight formed by the linkage of simple molecules (monomers)
under suitable conditions. When two or more different monomers are involved, the product is called a
copolymer.
Pop, Solvent
Blister and/or void in the coating resulting from trapped solvents released during curing process.
Porosity
Fine pores or hollows within a body of metal.
Port Opening
The openings or entry on the face of a porthole die through which the aluminum separates and flows into
the welding chamber.
Porthole Die
A die having a stationary core or mandrel which is held in place by integral core supports or webs. The
porthole die is a modification of the spider die, except that the spider is replaced with a chambered disk
that supports the mandrel (sometimes termed a stub mandrel); several portholes running through it
annularly about the mandrel, distinguish the porthole types. The die contains a weld chamber so that
when the billet is pushed the metal divides to flow around the core supports and welds together in the
welding chamber before passing through the die. Porthole dies are used in producing extruded hollow
profiles and tubing. See Bridge and Spider Dies .
Ports
The feed area on the entry side of a hollow side of a hollow die which are the openings through which the
metal stream flows.
Pot
The common name for a single electrolytic aluminum reduction cell. See Cell .
Powder Coating
Application of a coating in the form of a finely ground powder of coloring agents, resins, and additives;
heating of the part, either before or after powder deposition, fuses the powder into a continuous coating.
Prechamber
A recessed pocket built into the die cap of a hollow die with the approximate configuration of the die
openings. The purpose of this pocket is to aid in correcting for small distortion.

Precision (of measurement)
The extent to which repeated measurement of a standard with a given instrument yields the same result.
Preheating
A high temperature soaking treatment to provide a desired metallurgical structure. Homogenizing is a
form of preheating.
Press Alignment
The relationship between the center lines of the container, ram, and tool stack.
Press, Extrusion
The hydraulic machine which applies pressure to an aluminum billet inside a container, extruding it
through the opening of a die.
Press Tools
Parts of an extrusion press that are changed to produce a specific shape. This includes stem, fixed dummy,
container and liner.
Pressure Ring
A steel ring that is fitted into the center of the press platen against which the tooling stack is supported
during extrusion.
Pretreatment
The chemical alteration of a surface to make it suitable for application of paint or powder. The process
usually includes cleaning and applying a conversion coating.
Primer
Type of paint applied to a surface to increase its comptability with a topcoat, or to improve adhesion or
the corrosion resistance of the substrate.
Profile
A product that is long in relation to its cross-sectional dimensions, having a cross-section other than those
of wire, rod, bar, and tube, produced by extrusion, rolling, drawing, or cold finishing. Formerly termed a
shape.
Profile, Class 1 Hollow Extruded
A hollow extruded profile, the void of which is round and 1 inch or more in diameter and whose weight is
equally distributed on opposite sides of two or more equally spaced axes.

Profile, Class 2 Hollow Extruded
Any hollow extruded profile other than Class 1, which does not exceed a 5-inch diameter circumscribing
circle and has a single void of not less than 0.375-inch diameter or 0.110-square inch area.
Profile, Class 3 Hollow Extruded
Any hollow extruded profile other than class 1 or Class 2.
Profile, Cold-Finished
A profile brought to final dimensions by cold-working to obtain improved surface finish and dimensional
tolerances.
Profile, Cold-Finished Extruded
A profile produced by cold-finishing an extruded profile.
Profile, Cold-Finished Extruded
A cold-finished section produced from an extruded profile which is brought to final dimensions by cold
working to obtain improved surface finish and closer dimensional tolerances.
Profile, Cold-Finished Rolled
A profile produced by cold-finishing a rolled profile.
Profile, Drawn
A profile brought to final dimensions by drawing through a die.
Profile, Extruded
A profile produced by hot extruding.
Profile, Fluted Hollow
A hollow profile having plain inside surfaces and whose outside surfaces comprise regular, longitudinal,
concave corrugations with sharp cusps between corrugations.
Profile, Helical Extruded
An extruded profile twisted along its length. (Sometimes erroneously called spiral ).
Profile, Hollow
A profile, any part of whose cross section completely encloses a void.

Profile, Hollow Extruded (Class 1)
A hollow extruded profile whose void is round and one inch or more in diameter, and whose weight is
equally distributed on opposite sides of two or more equally spaced axes.
Profile, Hollow Extruded (Class 2)
Any hollow extruded profile other than Class 1, which does not exceed a 5-inch diameter circumscribing
circle and has a single void of not less than 0.375 inch diameter or 0.110 square inch area.
Profile, Hollow Extruded (Class 3)
Any hollow extruded profile other than Class 1 or Class 2.
Profile, Lip Hollow
A hollow profile of generally circular cross section and nominally uniform wall thickness with one hollow
or solid protuberance or lip parallel to the longitudinal axis; used principally for heat-exchange purposes.
Profile, Pinion Hollow
A hollow profile with regularly spaced, longitudinal serrations outside and round inside, used primarily for
making small gears.
Profile, Rolled
A profile produced by hot rolling.
Profile, Semihollow
A profile any part of whose cross section is a partially enclosed void the area of which is substantially
greater than the square of the width of the gap. The ratio of the area of the void to the square of the gap
is dependent on the class of semihollow profile, the alloy and the gap width.
Profile, Semihollow Extruded
A semihollow profile brought to final cross-sectional area by extruding.
Profile, Solid
A profile other than hollow or semihollow.
Profile, Spiral
Erroneously used sometimes where the term helical extruded profile is intended.
Profile, Stepped Extruded

An extruded profile whose cross-section changes abruptly in area at intervals along its length.
Profile, Streamline Hollow
A hollow profile with a cross-section of teardrop shape.
Profile, Structural
A profile in certain standard alloys, tempers, sizes, and section, such as angles, channels, H-sections, Ibeams,
tees, and zees commonly used for structural purposes. For channels and I-beams, there are two
standards, namely Aluminum Association Standard and American Standard.
Profile, Tapered Extruded
An extruded profile whose cross section changes continuously in area along its length or a specified
portion thereof.
Puller
A device which guides metal down the runout table as it is being extruded.
Quench, Air and Water
Usually refers to quenching or rapid cooling at the die, where large volumes of forced air, water or a
combination thereof are directed against aluminum extruded sections as they emerge from the die.
Quenching
Controlled rapid cooling of a metal from an elevated temperature by contact with a liquid, a gas, or a
solid.
Radial Layout
The method of locating the apertures in a die so that the major axis of each profile lies along a circle of
defined radius, giving each portion of bearing surface the same relationship to the center of the die as
similar portions on other profiles.
Ram
The press component which applies force against the dummy block. Ram and stem are interchangeable
terms describing any extension of the main cylinder in an extrusion press.
Reciprocator
A mechanical device which moves an applicator along a determined path repeatedly.
Recovery

The amount of saleable aluminum in the form of extrusions obtained from a press run. The recovery ratio
is the proportion of such saleable metal to either the original ingot or to the ready-to-extrude billet, as the
case may be.
Reduction
In metallurgy, the electrochemical process by which purified alumina (aluminum oxide) is broken down
into its constituents, freeing metallic aluminum.
Reduction Ratio (Extrusion Ratio)
The comparison of the cross-sectional billet area to total cross-sectional area of the resulting extrusions.
This is determined by the cross-sectional area of the container or upset billet divided by the crosssectional
area of the combined die openings.
Refined Aluminum
Aluminum of very high purity (99.950 percent or higher) obtained by special metallurgical treatments.
Reflectivity
The ability of a surface to reflect light and other electromagnetic radiation. Aluminum has high reflectivity:
80% or more for visible light, and 90% or more for infrared radiation.
Reheating
Heating metal again to hot-working temperature. In general no structural changes are intended.
Relieved
Aperture or opening in a die where its entrance is smaller than the exit.
Residual Stresses
Those stresses set up within a metal as the result of non-uniform plastic deformation which may be
caused by drastic temperature gradients in quenching.
Resilience
The ability of a material to regain its original shape after distortion. Aluminum is a resilient material.
Resolution (of a measuring instrument)
The smallest unit of measure that an instrument is capable of accurately and repeatedly indicating.
Restrictor Bumps (dams, speed bumps)
A bulge or hump in the die's metal flow area serving as a means of controlling the flow or feed of metal.

Rib
An elongated projection on a shape, forging or casting to provide stiffening.
Ring Tooling (die ring)
A cylindrical sleeve that holds the die and backer in axial relationship to each other.
Rivet
(1) To connect two or more pieces of material by inserting in a hole through them a metal pin with a head
on one end of it, and then forming a second head on the other end; (2) The connecting pin itself.
Rockwell Hardness
See Hardness, Rockwell .
Rod
A solid wrought product, long in relation to its cross-section, which is not less than 0.375 inch in diameter.
(Smaller sizes are classified as wire.)
Rod, Alclad
Rod having on its surface a metallurgically bonded aluminum or aluminum alloy coating that is anodic to
the core alloy to which it is bonded, thus electrolytically protecting the core alloy against corrosion.
Rod, Extruded
Rod produced by hot extruding.
Rod, Rolled
Rod produced by hot rolling.
Rod Runout Length
The length of extrusion rod from each billet.
Roundness
This term is not recommended. The term Ovality is preferred.
Rub, Tool
A surface area showing a scratch or abrasion resulting from contact of the hot extrusion with the press
equipment or tooling or, in the case of multi-hole dies, with others sections as they exit the press.

Run, Statistics
A consecutive number of points consistently increasing or decreasing, or above or below the central line.
Can be evidence of the existence of special causes of variation.
Runout Table
Table at immediate exit of press leadout equipment which helps to guide and support the extrusion.
Sag
Downward flow of a paint film as a result of its being applied too heavily or too wet. Also called Runs.
Salt Spray
Corrosion test using salt sprayed as a mist in a heated humidity chamber to simulate seashore conditions,
or to accelerate corrosion at a controlled rate.
Sandwiching
The simultaneous extrusion of two layers of metal failing to weld because of film impurities between
them.
Scalping
Mechanical removal of the surface layer from a fabricating ingot or semi-finished wrought product so that
surface imperfections will not be worked into the finished product.
Screw Index
A provision on some extrusion presses for moving the die in a horizontal plane with respect to the
container.
Screw Boss
The part of the die or mandrel bearing used to make screw holes in the extrusion.
Sealing Pressure
The pressure which locks the container and die face during the extrusion cycle.
Seam
The junction line of metal that has passed through a hollow die, separated and rejoined at the exit point.
Seams are present in all extruded hollows produced from the extrusion process and in many cases are not
visible.

Seam Defect
An unbonded fold or lap on the surface of the metal, which appears as a crack, usually the result of a
defect in casting or working that has not bonded shut.
Seam, Extrusion
See Seam, Weld .
Seam, Weld
The junction line of metal that has passed through a hollow die, separated and rejoined at the exit point.
Seams are present in all extruded hollows produced from the direct extrusion process and in many cases
are not visible.
Seamless
A hollow product which does not contain any line junctures resulting from method of manufacture.
Secondary Aluminum
Aluminum recovered primarily from scrap, segregated by alloy, and resmelted. Aluminum scrap is widely
recycled and supports a large secondary aluminum production industry.
Section
(1) A drawing showing an imaginary view through an item as though it had been cut by a plane (2) To cut
through a piece of metal to expose an internal area for metallurgical examination.
Section Number
The number assigned to an extruded or drawn profile for identification and cataloging purposes, usually
the same number assigned for the same purpose to the die from which the profile is made.
Section Print
An engineering drawing depicting the extrusion profile's cross-section.
Self-tapping Screw
A hardened screw with a sharp point, so designed that its threads cut their own mating threads when
inserted and rotated in an appropriately-sized hole.
Semihollow Profile
An extruded profile, any part of whose cross section partially encloses a void, the area of which is
substantially greater than the square of the width of the gap.
Shadow

Surface discoloration.
Shear Bridge Die
A bridge die that is recessed in a ring so that the butt can be sheared without any die stripping.
Shear, Butt
The device which separates or removes the extrusion residue or discard (billet butt) at the end of each
cycle.
Shear Edge
The leading (entry side) edge of a mandrel or die cap bearing.
Shear Edge Shifted
A condition where the mandrel shear edge is offset from the die cap bearing edge.
Shear Strength
The maximum stress that a material is capable of sustaining in shear. In practice, shear strength is
considered to be the maximum average stress computed by dividing the ultimate load in the plane of
shear by the original area subject to shear. Shear strength is usually determined by inserting a cylindrical
specimen through round holes in three hardened steel blocks, the center of which is pulled (or pushed)
between the other two so as to shear the specimen on two planes. The maximum load divided by the
combined cross-sectional area of the two planes is the shear strength.
Sheet
A rolled product that is rectangular in cross section with thickness less than 0.250 inch but not less than
0.006 inch and with slit, sheared or sawed edges.
Sheet Stock
See Reroll, Stock .
Sheet, Alclad
Composite sheet comprised of an aluminum alloy core having on both surfaces (if one side only, Alclad
One Side Sheet) a metallurgically bonded aluminum or aluminum alloy coating that is anodic to the core,
thus electrolytically protecting the core against corrosion.
Sheet, Anodizing
Sheet with metallurgical characteristics and surface quality suitable for the development of protective and
decorative films by anodic oxidation processes.

Sheet, Clad
Composite sheet having on both surfaces (if on one side only, Clad One Side Sheet) a metallurgically
bonded metal coating, the composition of which may or may not be the same as that of the core.
Sheet, Coiled
Sheet in coils with slit edges.
Sheet, Coiled Circles
Circles cut from coiled sheet.
Sheet, Coiled Cut to Length
Sheet cut to specified length from coils and which has a lesser degree of flatness than flat sheet.
Sheet, Flat
Sheet with sheared, slit, or sawed edges, which has been flattened or leveled.
Sheet, Flat Circles
Circles cut from flat sheet.
Sheet, Mill Finish (MF)
Sheet having a non-uniform finish that may vary from sheet to sheet and within a sheet, and may not be
entirely free from stains or oil.
Sheet, One Side Bright Mill Finish (1SBMF)
Sheet having a moderate degree of brightness on one side and a mill finish on the other.
Sheet, Painted
Sheet, one or both sides of which has a factory-applied paint coating of controlled thickness.
Sheet, Standard One Side Bright Finish (S1SBF)
Sheet having a uniform bright finish on one side and a mill finish on the other.
Sheet, Standard Two Sides Bright Finish (S2SBF)
Sheet having a uniform bright finish on both sides.
Shifting Walls

Uneven walls caused by core (mandrel) movement.
Short Choke
A condition in an extrusion die where a very slight chamfer is created on the edge formed by the bearing
surface and die face which is much shorter than regular choke. This tends to slow metal flow.
Short Transverse Direction
For plate, sheet and forgings, the direction through the thickness perpendicular to both longitudinal and
long transverse directions.
Shrinkage
Contraction that occurs when metal cools from the hot-working temperature.
Shut Off/Seal Off Semihollow Die
A semihollow die where the die plate (cap) and the mandrel overlap each other at or near the tongue. The
interior profile surface is formed by the mandrel and the outside surface by the die cap. The two tooling
components mate together with an overlapping condition to crate the semihollow profile.
Side Set
A difference in thickness between the two edges of plate, sheet or foil.
Skewed
A nonsymmetric distribution is said to be skewed.
Skip
An area of uncoated sheet which is frequently caused by equipment malfunction.
Skull
A residual buildup of aluminum alloy from preceding billets that adhere to the container liner wall. The
thickness is determined by difference in container I.D. and circumference of dummy block. See Cleanout
Block.
Slip-fit Joint
A joint assembled by sliding two mating parts together in the direction of their length.
Sliver
Thin fragment of aluminum which is part of the material but only partially attached. Surface damage or
residual liquation which is subsequently rolled are typical causes.

Slug
A metal blank for forging or impacting.
Smudge
A dark film of debris, sometimes covering large areas, deposited on the sheet during rolling.
Snap-fit Joint
A self-locking joint whose mating parts exert a cam action, flexing until one part slips past a raised lip on
the other part, preventing their separation.
Snap Ring
A mark or blemish left on the surface of the extrusion caused by any sudden die or extrusion tooling
movement.
Soaking
In metallurgy: the prolonged heating period during several methods of heat treating metals, soaking
allows the heat to penetrate completely the mass of metal, and so permits the required metallurgical
changes to take place.
Soft Alloy
A general term loosely describing most alloys of the 1xxx, 3xxx, or 6xxx series.
Soldering
Joining metals by flowing a molten filler metal between the connecting surfaces at a melting range below
an arbitrary temperature, usually about 800 º F. (At higher temperatures, the process is call brazing.) The
filler metal, called solder, may have any of a variety of compositions formulated for the different metals to
be joined; the so-called soft, or low-melting, solders are primarily of tin and lead.
Solid Dies
A steel disk with one or more orifices or apertures of the same cross-sectional area and contour as the
desired product, through which metal is forced. Such dies are generally employed where profiles other
than hollow are required. If solid dies are used for hollow profiles (as opposed to the use of hollow dies of
the bridge, porthole or spider type containing a fixed stub mandrel as an integral part of the die) then a
mandrel actuated by the action of the ram must be employed. These may be fixed or floating mandrels
which require hollow (cast or bored) billets. An exception is the piercing type mandrel, which needs no
cored billet.
Solid Profile
Any profile other than a hollow or semihollow.

Solution Heat Treating
Heating an alloy at a suitable temperature for sufficient time to allow soluble constituents to enter into
solid solution where they are retained in a supersaturated state after quenching.
Solvent Pop
Blistering caused by entrapped solvent during baking, possibly caused by short flashoff or improper
solvent balance.
Solvent Resistance
The ability of cured paint film to resist attack by a particular solvent. Often used as an indication of cure.
Specification
The engineering requirement for judging acceptability of a particular characteristic. A specification is
never to be confused with a control limit.
Specimen
That portion of a sample taken for evaluation of some specific characteristic or property.
Speed, Bearing
Is a reduction in the effective bearing length and is the opposite correction technique to choke. See
Relieved, Back Taper.
Speed Tear
A series of surface cracks perpendicular to the extruding direction. Speed tearing normally occurs in
corner radii or extremities of a section and is caused by localized high temperature.
Spider Die
An extrusion die for producing hollow shapes, whose mandrel is supported by multiple legs attached to
the cap. Metal flows between the spider's legs and reunites before emerging through the die aperture.
Splice
The end joint uniting two webs.
Spot, Lube
A non-uniform extraneous deposit of lube on the coated sheet.
Spreader

An auxiliary tool sometimes attached to the end of the container to produce an effective billet of greater
size than the I.D. of the container. Use of a spreader permits the extruding of sections considerably wider
than container I.D., but only under definitely limited operating conditions.
Square Bearing
A bearing surface exactly perpendicular to the die face and ideally to the metal flow.
Squareness
(1) The measure of a bearing being perpendicular to the die face which can be accomplished with a
toolmaker's square or equivalent techniques. (2) Characteristic of having adjacent sides or planes meeting
at 90 degrees.
Stabilizing
A low temperature thermal treatment designed to prevent age-softening in certain strain hardened alloys
containing magnesium.
Stain, Heat Treat
A discoloration due to non-uniform oxidation of the metal surface during heat treatment.
Stain, Oil
Surface discoloration which may vary from dark brown to white and is produced during thermal treatment
by incomplete evaporation and/or oxidation of lubricants on the surface.
Stain, Saw Lubricant
A yellow to brown area of surface discoloration at the ends of the extruded length. It is the residue of
certain types of saw lubricants if they are not removed from the metal prior to the thermal treatment.
Stain, Water
See Corrosion, Water Stain .
Standard
An established dimensional tolerance for a certain class of product.
Starvation

Non-uniform coating application which results in absence of coating in certain areas.
Starving Wall
Light walls on the extruded profile caused by a restricted flow of metal before the bearing entry.
Stepped Extrusion
An extrusion having one or more abrupt changes in cross section at intervals in its length.
Stepped Extrusion Process
A process similar to the conventional extrusion process producing an extrusion with abrupt changes in
dimension. In this process the extrusion press is stopped when the billet is only partially extruded, the
split dies are removed and replaced with dies of larger opening or orifice. Extrusion is then resumed. The
result is an extrusion which has an abrupt change in cross section. The first portion extruded having the
smaller cross section is called the minor section while the second portion having the larger cross section is
called the major section.
Sticking
Adherence of foil surfaces sufficient to interfere with the normal ease of unwinding.
Straightness
The absence of divergence from a right (straight) line in the direction of measurement.
Strain
A measure of the change in size or shape of a body under stress, referred to its original size or shape.
Tensile or compressive strain is the change, due to force, per unity of length in an original linear
dimension in the direction of the force. It is usually measured as the change (in inches) per inch of length.
Strain Hardening
Modification of a metal structure by cold working, resulting in an increase in strength and hardness with
loss of ductility.
Streak (Stripe)
A superficial band or elongated mark which produces a non-uniform surface appearance. A streak is often
described by source.
Streak, Bearing
A longitudinal discoloration that can occur where there are large changes in wall thickness as a result of
uneven cooling. These streaks usually appear lighter than the surrounding metal.
Streak, Bright

A bright superficial band or elongated mark which produces a non-uniform surface appearance.
Streak, Buff
A dull continuous streak caused by smudge buildup on a buff used at shearing or other operations.
Streak, Burnish
A bright region on the sheet caused by excessive roll surface wear.
Streak, Coating
A banded condition caused by non-uniform adherence of roll coating to a work roll. It can be created
during hot and/or cold rolling. If generated in the hot rolling process, it is also called Hot Mill Pick-up.
Streak, Diffusion
Surface discoloration which may vary from gray to brown and found only on Alclad products.
Streak, Dirt
Surface discoloration which may vary from gray to black, is parallel to the direction of rolling, and contains
rolled in foreign debris. It is usually extraneous material from an overhead location that drops onto the
rolling surface and is shallow enough to be removed by etching or buffing.
Streak, Grease
A narrow discontinuous streak caused by rolling over an area containing grossly excessive lubricant
drippage.
Streak, Grinding
A streak with a helical pattern appearance transferred to a rolled product from a work roll.
Streak, Heat
Milky colored band(s) parallel to the rolling direction which vary in both width and exact location along
the length.
Streak, Herringbone
Elongated alternately bright and dull chevron markings.

Streak, Leveller
A streak on the sheet surface in the rolling direction caused by transfer from the leveler rolls.
Streak, Roll
A non-uniform surface appearance parallel to the rolling direction.
Streak, Structural
A non-uniform appearance on an etched or anodized surface caused by heterogeneities (variabilities)
remaining in the metal from the casting, thermal processes or hot working stages of fabrication.
Strength/Weight Ratio
The relationship between the structural strength of a material and its weight. the strength-to-weight ratio
of structural aluminum alloys is about twice that of mild steel.
Stress
Force per unit of area. Stress is normally calculated on the basis of the original cross-sectional dimensions.
The three kinds of stresses are tensile, compressive, and shear.
Stress Relieving
The reduction of the effects of internal residual stresses by thermal or mechanical means.
Stretch Straightening
The process of stretching extruded sections beyond the yield strength of the alloy to achieve longitudinal
straightness.
Stretcher Flattening
A process of removing bow and warpage where an extrusion is gripped between jaws and subjected to a
stress higher than its yield strength and is elongated a definite amount to establish a permanent set.
Stretching
In extrusion: straightening an aluminum member by pulling. An average stretch increases the length by
about one-half of one percent, and produces correspondingly a slight decrease in the cross-sectional
dimensions, called stretch-down.
Striation
Longitudinal non-uniform coating thickness caused by uneven application of the liquid coating.
Structural Finish

A structural finish is a standard finish where surface imperfections are acceptable and appearance is not a
requirement. This finish could be characterized by the term non-exposed.
Structural Shape
An aluminum section, now usually extruded, of any design accepted as standard by the structural industry.
Such shapes include I-beams, wide flange or H-beams, channels, angles, tees and zees.
Sub-Bolster
A hardened alloy steel disk often employed when the bolster does not fill the die stack. See Bolster .
Substrate
The Layer below the paint; that is, the substance being painted.
Suck-In
A defect caused when one face of a forging is sucked in to fill a projection on the opposite side.
Surface Tear
Minute surface cracks on rolled products which can be caused by insufficient ingot scalping.
Taper Heating
A staged or gradient heating.
Taper Seal Die
A type of hollow die using a taper or conical angle to seal the die and its ring.
Tear, Speed
A series of surface cracks perpendicular to the extruding direction. Speed tearing normally occurs in
corner radii or extremities of a section and is caused by localized high temperature.
Tearing
Typically cracks or separations due to high extrusion speed or extrusion temperature.
Telescoping
Lateral stacking, primarily in one direction, of wraps in a coil so that the edges of the coil are conical rather
than flat. Improper alignment of rolls over which the metal passes before rewinding is a typical cause. See
also Oscillation.

Temper
The combination of hardness and strength imparted to a metal by mechanical or thermal treatments and
characterized by certain metallurgical structures and mechanical properties determining temper
designation.
Tensile Strength
In tensile testing, the ratio of maximum load to original cross-sectional area. Also called Ultimate Strength.
Thermal Conductivity
The ability of a material to transmit heat through its bulk and, by direct contact, to other substances.
Aluminum is a good heat conductor and is widely used in cookware and in radiators and other heat
exchangers.
Tolerance
Allowable deviation from a nominal or specified dimension.
Tongue
That portion of die cap metal surrounded by the aperture except at one end which is termed the base of
the tongue.
Tongue (of an extrusion die)
An area of a die surrounded on three sides by the extrusion aperture.
Tongue Cave
Distortion of the die tongue.
Tongue and Groove Joint
A joint in which one part has a groove which receives a projection (tongue) on the other part, shaped to fit
snugly.
Tonnage
Press hydraulic pressure times cylinder area, expressed in U.S. tons.
Tool
A term usually referring to the dies, mandrels, etc., used in the production of extruded or drawn profiles
or tube.
Tools or Tooling

The parts of an extrusion press that are changed to produce a specific shape. Tools include dies and
mandrels, and various supporting parts.
Tool Deflection
See Deflection . The distortion, displacement or caving in the extrusion direction of the extrusion die or
tool surface under extrusion pressure.
Tool Rub
A surface area showing a scratch or abrasion resulting from contact of the hot extrusion with the press
equipment or tooling or, in the case of multi-hole dies, with other sections as they exit the press.
Tooling Plate
A cast or rolled product of rectangular cross section of thickness 0.250 inch or greater, and with edges
either as-cast, sheared or sawed, with internal stress levels controlled to achieve maximum stability for
machining purposes in tool and jig applications.
Topcoat
In a multi-coat system, the coat applied over a primer, usually the final coat applied.
Torn Surface
A deep longitudinal rub mark resulting from abrasion by extrusion or drawing tools.
Toxicity
The degree to which a substance is toxic, or poisonousness.
Traffic Mark
Abrasion which results from relative movement between contacting metal surfaces during handling and
transit. A dark color from the abrasively produced aluminum oxide is usually observed. A mirror image of a
traffic mark is observed on the adjacent contacting surface.
Transverse Direction
A direction perpendicular to the direction of working.
Transverse Weld
A condition existing within an extrusion which is created by the interface of two separate billets. In
practice the interface is extruded at different rates through the die and is formed into a conical or pointed
configuration within a portion of the extrusion.
Tread Plate

Sheet or plate having a raised figured pattern on one surface to provide improved traction.
Trend
A gradual, systematic change with time or other variables.
Trim Inclusion
Edge trimming accidentally wound into a roll of foil.
Tube
A hollow wrought product that is long in relation to its cross section, which is symmetrical and is round, a
regular hexagon or octagon, elliptical, or square or rectangular with sharp or rounded corners, and that
has uniform wall thickness except as affected by corner radii.
Tube Bloom
This term is not recommended. The term Tube Stock is preferred.
Tube Stock
A semi-finished tube suitable for the production of drawn tube.
Tube, Butt-Welded
A welded tube, the seam of which is formed by positioning one edge of the sheet against the other for
welding.
Tube, Drawn
A tube brought to final dimensions by drawing through a die.
Tube, Embossed
A tube the outside surface of which has been roll-embossed with a design in relief regularly repeated in a
longitudinal direction.
Tube, Extruded
A tube formed by hot extruding.
Tube, Finned
Tube which has integral fins or projects protruding from its outside surface.
Tube, Fluted

A tube of nominally uniform wall thickness having regular, longitudinal, concave corrugations with sharp
cusps between corrugations.
Tube, Heat-Exchanger
A tube for use in apparatus in which fluid inside the tube will be heated or cooled by fluid outside the
tube. The term usually is not applied to coiled tube or to tubes for use in refrigerators or radiators.
Tube, Helical-Welded
A welded tube produced by winding the sheet to form a closed helix and joining the edges of the seam by
welding.
Tube, Lap-Welded
A welded tube the seam of which is formed by longitudinally lapping the edges of the sheet for welding.
Tube, Redraw
This term is not recommended. The term Tube Stock is preferred.
Tube, Seamless
Tube that does not contain any line junctures (metallurgical welds) resulting from the method of
manufacture. This product may be produced by die-and-mandrel or by hot-piercer processes. Tube
produced by porthole-die extrusion, bridge-die extrusion, or welding processes is generally not considered
Seamless. (Seamless tube is typically used for fluid-carrying applications under pressure.)
Tube, Sized
A tube that, after extrusion, has been cold drawn a slight amount to minimize ovality.
Tube, Stepped Drawn
A drawn tube whose cross section changes abruptly in area at intervals along its length.
Tube, Structural
Tube commonly used for structural purposes.
Tube, Welded
A tube produced by forming and seam-welding sheet longitudinally.
Tubing, Electrical Metallic
A tube having certain standardized length and combinations of outside diameter and wall thickness

thinner than that of Rigid Conduit , commonly designated by nominal electrical trade sizes, for use with
compression-type fittings as a protection for electric wiring.
Tubing Product
A general term comprising tube, hollow profiles, and semi-hollow profiles.
Tubular Conductor
A tubular product suitable for use as an electric conductor.
Twist
(1) For rolled products, a winding departure from flatness. (2) For extrusions, a winding departure from
straightness.
Two-Tone
A sharp color demarcation in the appearance of the metal due to a difference in the work roll coating.
Ultraviolet
Electromagnetic radiation at wavelengths shorter than violet light and just beyond the visible light
spectrum. Sunlight includes ultraviolet radiation, which causes tanning or sunburn in human skin and
which may cause chemical or structural changes in some commercial materials. Aluminum reflects
ultraviolet radiation and is not damaged by it.
Unbalanced Feed
Is insufficient metal in one or more locations within the die aperture and is the result of a situation where
hollow die ports or flow plate openings do not permit uniform metal flow to all areas of the extrusion die.
Undercure
The result of curing a paint at either too low of a temperature or too little time, resulting in inadequate
hardness and solvent resistance.
V.O.C.
Volatile organic compound; any organic compound that participates in atmospheric photochemical
reactions as designated by EPA standards.
Vapor barrier
A material which prevents or impedes the passage of water vapor through the walls of a structure or
container. Aluminum is an excellent vapor barrier.
Vent

The action of relieving entrapped air or gases by a venting or burp procedure during the extrusion process.
Vent Mark
A small protrusion on a forging resulting from the entrance of metal into a die vent hole.
Viscosity
That property of a liquid which enables it to resist flow. High viscosity means a fluid resists flowing; low
viscosity means it flows readily.
Void
An empty space. In extrusion, the number, sizes, positions, and forms or voids within a hollow shape
influence the difficulty of production and the dimensional tolerances which can be assured.
Waving
A ripple effect, usually in the leg or legs of an extrusion, caused primarily by either an excessive deflection
in the tooling, excessive heat or unbalanced feed.
Web
(1) A single thickness of foil as it leaves the rolling mill. (2) A connecting element between ribs, flanges, or
bosses on shapes and forgings.
Webs
The supporting members of a hollow die mandrel that support the internal surface forming portion of the
die.
Weld
To join two pieces of metal by applying heat or pressure, causing them to melt in the welded area, mingle
and resolidify, forming a single piece.
Weld Chamber
The space directly between the web of the mandrel and the die plate, designed to facilitate welding of the
billet back together before it is extruded through the die aperture or opening.
Weld Line
A region in extruded hollow profiles observed after creating the two streams of metal within the die and
rejoining them around the web of a porthole or bridge die. Weld lines may appear as a narrow, dark line.
Weld, Incomplete
The junction line of metal that has passed through a die forming a hollow profile (shape), separated and

not completely rejoined. Flare testing is a method of evaluating weld integrity.
Welding
Joining two or more pieces of aluminum by applying heat or pressure, or both, with or without filler metal
to produce a localized union through fusion or recrystallization across the interface. (In cold welding, it is a
solid state welding process in which pressure is used at room temperature to produce coalescence of
metals with substantial deformation at the weld.)
Welding Rod
A rolled, extruded, or cast round filler metal for use in joining by welding.
Welding Wire
Wire for use as filler metal in joining by welding.
Wettability Test
The degree to which a metal surface may be wet to determine the absence of or the amount of residual
rolling or added lubricants or deposits on the surface.
Wire
A solid wrought product that is long in relation to its cross section, which is square or rectangular with
sharp or rounded corners or edges, or is round, hexagonal, or octagonal, and whose diameter or greatest
perpendicular distance between parallel faces is less than 0.375 inch.
Wire, Alclad
A composite wire product comprised of an aluminum-alloy wire having on its surface a metallurgically
bonded aluminum or aluminum-alloy coating that is anodic to the alloy to which it is bonded, thus
electrolytically protecting the core alloy against corrosion.
Wire, Cold-Heading
Wire of quality suitable for use in the manufacture of cold-headed products such as rivets and bolts.
Wire, Drawn
Wire brought to final dimensions by drawing through a die.
Wire EDM
Is an electrical discharge machining except that a wire is used as the electrode and the dielectric is
frequently ionized water. These machines are numerically controlled and computer programmed.
Wire, Extruded

Wire produced by hot extruding.
Wire, Flattened
Wire having two parallel flat surfaces and rounded edges produced by roll-flattening round wire.
Wire, Flattened and Slit
Flattened wire that has been slit to obtain square edges.
Workability
The relative ease with which various alloys may be formed by extruding, rolling, forging, etc.
Wrap
A characteristic of liquid or powder coatings in an electrostatic application to seek out and adhere to parts
of the substrate not in direct line of sight of the delivery system end point.
Wrap, Loose
A condition in a coil due to insufficient tension which creates a small void between adjacent wraps.
Wrought Product
A product that has been subjected to mechanical working by extruding, rolling, forging or other processes.
Yield Strength
The stress at which a material exhibits a specified permanent set. The offset used for aluminum and its
alloys is 0.2 percent of gauge length. For aluminum alloys the yield strengths in tension and compression
are approximately equal.