Aluminium Guide · Lesson 10

Aluminium glossary

The terms used in the aluminium industry, from A to Z, each explained in one line.

6 minutes’ read

In short

Billet, die and press: the three key elements of extrusion.
Alloy and temper: what the metal contains and what treatment it received.
kg/m, circumscribing circle and tolerance: the numbers that define a profile.

From A to Z

Ageing: Baking at about 170 to 200 °C that gives the profile its final strength (T5 or T6 temper).
Alloy: Aluminium with additions (magnesium, silicon, copper, zinc) that give it strength. It is named with four digits, such as 6063.
Alumina: Aluminium oxide, a white powder obtained from bauxite, from which aluminium is extracted by electrolysis.
Anodising: A finish that thickens the natural oxide layer of aluminium. It does not peel.
Bauxite: The ore from which aluminium is obtained.
Billet: A cylindrical bar of alloy that is heated and extruded. In Argentina it is called "tocho"; "billet" is also used.
Bridge die (porthole die): A die for profiles with closed hollows: the metal splits and welds back together inside it.
Circumscribing circle: The smallest circle that contains the whole cross-section of the profile. It determines which press is needed.
Container: The cylinder in the press where the billet is loaded before being pushed against the die.
Density: Mass per unit volume. For the aluminium used in extrusion, it is 2.70 g/cm³.
Die: A steel tool with the shape of the cross-section. Each profile has its own.
Extrusion: The process that shapes profiles by pushing a hot billet through a die.
Extrusion press: The machine that pushes the billet. Its force is measured in tonnes.
Flat bar: A solid profile with a rectangular cross-section.
kg/m: The weight per metre of a profile. It is used to calculate the weight of a length and of an order.
Length: Each bar of profile. In Argentina, profiles are sold in 6-metre lengths.
LME: London Metal Exchange: the global benchmark for the price of primary aluminium.
Moment of inertia (second moment of area): A number that measures how well a section resists bending. It is expressed in cm⁴.
Powder coating: A polyester coating that is melted in an oven. It allows any colour.
Scrap: Discarded aluminium that is remelted and reused, with about 5% of the energy needed to produce new metal.
Sealing: The last step of anodising: it closes the pores of the oxide layer.
Section modulus: A number that relates the moment of inertia to the distance to the outer edge; it is used to calculate stresses. It is expressed in cm³.
Standard profile: A profile with standard dimensions that is available from stock: tubes, angles, flat bars, U-channels, T-sections.
Stretching: The step in which the profile is pulled from both ends to straighten it.
Temper: The condition of the profile according to the heat treatment it received: T4, T5, T6.
Thermal break (RPT): Windows and doors with an insulating element between two aluminium profiles, to block the passage of heat and cold. RPT stands for the Spanish "ruptura de puente térmico".
Tolerance: How much the actual dimension may differ from the drawing without the profile falling outside the standard.
Tongue: A projecting part of the die that forms a channel in the profile. If it is long and thin, it can break.

Frequently asked questions

What is an aluminium billet?

A cylindrical bar of aluminium alloy that is heated and pushed through a die to make profiles. In Argentina it is called "tocho", although "billet" is also used.

What does RPT mean in aluminium windows and doors?

It stands for "ruptura de puente térmico", Spanish for thermal break: the profiles have an insulating element between the outer and inner faces that blocks the flow of heat and improves insulation.