ALUMINUM GLOSSARY - D

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 The holder can be unlocked and the die withdrawn for the removal of butt and scrap.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.