ALUMINUM GLOSSARY - S

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.