ALUMINUM GLOSSARY - A

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 self-contained 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.