Aluminium extruded profiles

1 What is aluminum profile?

Profile

Wrought product that is long in relation to its cross-sectional dimensions which is of a form other than that of sheet, plate, rod, bar, tube, wire or foil.
For profiles sometimes the term “shape” or “section” is used [1].

1.1 Aluminium profile forming processes

Extrusion. Process in which a billet in a container is forced under pressure through an aperture of a die (Fig. 1-1).
Drawing. Pulling metal through a die in order to reduce or change the cross-section or to work harden the metal (Fig. 1-2).
Cold roll forming (Fig. 1-3).

1.2 Raw materials

Extrusion ingot. Ingot, intended and suitable for extruding, typically of solid circular cross-section, sometimes with a central hollow or a flattened cross-section.
Extrusion log. Extrusion ingot not cut to length.
Extrusion billet. Extrusion ingot cut to length.
Drawing stock.
Aluminium strip.

1.3 Aluminium profile types

Extruded profile. Profile brought to final dimensions by extruding.
Drawn profile. Cold-finished profile brought to final dimensions by drawing through a die.
Roll formed profile.

Figure 1-1 – Definition and principle of extrusion [2]

Figure 1-2 – Manufacturing aluminium cold drawn tube from extruded drawing sock [3]:
Methods of tube drawing:
(a) without internal support by sinking;
(b) with internal support by fixed plug,
(c) with internal support by floating plug,
(d) with internal support by moving mandrel

Figure 1-3 – Roll-formed aluminium profiles. Profiles are made from aluminum strip [4]

2 Aluminium extruded products

Aluminium extruded products include (Fig. 2):

profiles
rods/bars (round, square, rectangle, hexagonal)
tubes (round, square, rectangle)
stocks for drawing, forging, machining, cold and impact extrusion

Figure 2 – Aluminium extruded products [5]

3 Aluminium extruded profiles

3.1 Extrudung aluminium profiles

Direct extrusion. Extrusion process with relative movement between billet and container (Fig. 3-1)
Indirect extrusion. Extrusion process without relative movement between billet and container (Fig. 3-2)
Extrusion press. Machine consisting essentially of a container, a ram or other pressure-applying device, and a die, used for extrusion (Fig. 3-3)
Container. Hollow cylinder in an extrusion press from which the billet is extruded
Extrusion tool. Term typically referring to the dies, mandrels, etc., used in the production of extruded profiles or tube (Fig. 3-4).
Extrusion die. Block of steel having one or more holes of the required contour through which a billet is forced.
Porthole die. Extrusion die that incorporates a mandrel as an integral part of the die assembly.
– Bridge, spider and self-stripping dies are special forms of porthole die.
– Hollow profiles or tubes extruded by a porthole die are characterized by one or more longitudinal extrusion seams.

Figure 3-1 – Direct extrusion [5]

Figure 3-2 – Indirect extrusion process [5]

Figure 3-3 – Schematic of a direct extrusion press.
1, counter platen; 2, die slide or rotary die head;
3, shear; 4, billet container; 5, moving crosshead;
6, stem; 7, cylinder crosshead; and
8, oil tank with drive and controls.
Source: Schloemann-Siemag [2]

Figure 3-4 – Extrusion is process in which a billet in a container is forced under pressure through an aperture of a die [6]

3.2 Types of aluminium extruded profiles

Solid profile

Profile in which the cross-section does not include any enclosed void.

Hollow profile

Profile in which the cross section completely encloses one or more voids.

Semi-hollow profile

Semi-hollow profile is a solid profile any part of whose cross section is a partially enclosed void the area of which is substantially greater than the square of the width of the gap. The ratio of the area of the void to the square of the gap is dependent on the class of semi-hollow profile, the alloy and the gap width.

A semi-hollow profile is defined by it’s tongue ratio as it partially encloses a void [7]:

A semihollow profile will be defined mathematically by comparing the area of the partially enclosed void to the size of the gap (to the mathematical square of the gap size).
If that ratio is larger than a pre-defined number, the shape is classified as semi-hollow; if the ratio is smaller, the shape is considered a solid .

Figure 3-5 – Three general categories that extruded profiles are categorised in: Solid, Semihollow & Hollow [7]

Extrusion dies for solid, hollow and semi-hollow profiles

Figure 3-6 [6]
{a) A semi-hollow die extrudes a shape
that is nearly hollow, partially enclosing a void.
The die set includes a mandrel section and cap section.

(b) A hollow die produces profiles with one or more voids.
The die set includes a mandrel section and cap section.

Figure 3-7 – Extrusion process through hollow and semi-hollow dies [11]

3.3 Seamless profile

Seamless profile is an hollow profile which does not contain any line junctures resulting from method of manufacture (Fig. 3-7).

Figure 3-7 – Extruding seamlees hollow tube with a die and a mandrel [5]

4 Extrusion aluminium alloys

4.1 Chemical composition

Figure 4-1 – Chemical composition of some AlMgSi alloys [5]

Figure 4-2 – Chemical composition of some aluminium alloys produces as extrusions [5]

4.2 Mechanical properties

Figure 4-3 – Mechanical properties of some aluminium alloys produced as extrusion [5]

4.3 Aluminium alloys extrudability

Figure 4-4 – Relative extrudabilty of aluminium alloys [5]

4.4 Minimum wall thickness

Figure 4-5 – A guide to minimum section thickness for 6063 extrusion depending on its complexity [5]

Figure 4-6 – Minimum wall thickness for extrusion presses 10-80 MN [7]

5 Dimension and form tolerances

Precision profile. Profile which fulfils special requirements concerning tolerances on form and dimensions. Aluminium extruded precision profiles of 6060 and 6063 alloys are produced according to EN 12020.
Structural (standard) profile. Profile commonly used for structural purposes such as angles, channels, H-beams, I-beams, tees, and zees. Aluminium extruded structural profiles of all extrusion aluminium alloys are produced according to EN 755.

5.1 Circumscribed circle diameter

Circumscribing circle. Circle that will just contain the cross-section of a profile, typically designated by its diameter (CCD – circumscribed circle diameter).

Figure 5-1 – Circumscribed circle diameter (CCD) of the profile for a round billet [5]

5.2 Tolerances on cross-sectional dimensions

Figure 5-2 – Definition of cross-sectional dimensions A, B, C, E, H in EN 755-9 [9]

Tolerances on the dimensions of the cross section of the profile depend on the type of the dimension. There are the following types of dimensions:

A: wall thicknesses of “solid part” of the profile;
B: wall thicknesses of “hollow part” of the profile (encloses the hollow spaces except those between two hollow spaces;
C: wall thicknesses of “hollow part” of the profole (between two hollow spaces);
E: the length of the shorter leg of profiles with open ends;
H: all dimensions (except wall thickness) between points on the cross section of the profile or the centres of open screw holes.

6 Categories of complexity of aluminum profiles

6.1 Shape factors of aluminium profiles

Figure 6-1 – Shape factors of various aluminium profiles [5]

5.2 Complexity of aluminium profiles

Figure 6-2 – Classification of aluminium extruded profiles by complexity (K. tepid) [7]

5.3 Optimising extruded profile design

Figure 6-3 – Optimising extruded profile design [2]

7 Aluminium extruded profile cost

The cost of an aluminum extruded profile is determined, among other things, by the following factors:

extrusion die cost (Fig. 6-1)
type of profile (solid, hollow or
extrudability of aluminum alloy (extrusion speed) (Fig. 6-2)
required temper of profile material (press quenching or furnace quenching, natural or artificial ageing)
level of requirements for dimensional and shape tolerances (EN 755 or EN 12020)
surface quality requirements (without coating, for powder coating, for anodising).

Figure 7-1 – Dependence of the cost of an extrusion tool
on the type of dies (solid or hollow),
as well as the size and complexity of the profile (1994 prices) [5]

Figure 7-2 – Extrusion speed and minimal wall thickness of various aluminium alloys [5]

Sources:

Global Advisory Group GAG – Guidance “Terms and Definitions” – 2011
Aluminum Extrusion Technology / P. Saha
Mechanical Properties and Working of Metals and Alloys / Amit Bhaduri – Springer Series in Materials Science – Volume 264 – 2018
ALUTECH GROUP
SPOKE IN 1302
Die Defects and Die Corrections in Metal Extrusion / S.Z. Qamar, T. Pervez and J. Ch. Chekotu – Metals 2018, 8(6), 380
https://www.bwcprofiles.co.uk/
SPOKE 2202
EN 755-9
IN 12020-2
Influence of Al Microstructure on Hard Anodising Quality / Tom Hauge, Hydro Aluminium, 2014.