ALUMINUM GLOSSARY - E

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.