Aluminium extruded profiles

Get to know the world of aluminium extruded profiles. Learn about the extrusion process and the different shapes and sections it can create.

1 What is aluminium profile?

Profile

Wrought product that is long in relation to its cross-sectional dimensions and have 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).
• Drawing. Pulling metal through a die in order to reduce or change the cross-section or to work harden the metal (Fig. 2).
• Cold roll forming (Fig. 3).

1.2 Raw materials

• Extrusion ingot. Ingot, intended and suitable for extruding, typically of solid circular 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 – Definition and principle of extrusion [2]

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

 2 Aluminium extruded products

Aluminium extruded products include (Fig. 4):

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

Figure 4 – Aluminium extruded products [5]

3 Aluminium extruded profiles

3.2 Types of aluminium extruded profiles

Solid profile

Profile in which the cross-section does not include any enclosed void (Figure 5c).

Hollow profile

Profile in which the cross section completely encloses one or more voids (Figure 5 b).

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 (Figure 5a).

 

Figure 5 [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.

(c) The solid die stack to produce a solid profile
includes die plate and die backer. The shape is formed by die plate.

Figure 6 – Extrusion process through hollow and semi-hollow dies [11]

3.3 Seamless tubes

Seamless tube is an hollow profile which does not contain any line joints from method of manufacture (Fig. 7).

Figure 7 – Seamlees tube extrusion with a die and a mandrel [5]

 

4 Extrusion aluminium alloys

4.1 Chemical composition

 

Figure 8 – Chemical composition of some AlMgSi extrusion alloys [5]

4.2 Mechanical properties

Figure 9 – Mechanical properties of some aluminium extrusion alloys [5]

 4.3 Aluminium alloys extrudability

Figure 10 – Relative extrudabilty of aluminium alloys [5] 

4.4 Minimum wall thickness

Figure 11 – Minimum wall thickness for various extrusion presses [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 alloy and 6063 alloy 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).

 Рисунок 12 – Circumscribed circle diameter (CCD) of the profile for a round billet [5]

5.2 Tolerances on cross-sectional dimensions

Figure 13 – Definition of cross-sectional dimensions A, B, C, E, H for tolerancing 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 aluminium profiles

6.1 Shape factors of aluminium profiles

Figure 14 – Shape factors of various extruded aluminium profiles [5]

6.2 Complexity of aluminium extruded profiles

Figure 15 – Classification of aluminium extruded profiles by complexity (K. Laue) [7]

7 Aluminium extruded profiles cost

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

• extrusion die cost
• type of profile (solid, hollow)
• extrudability of aluminum alloy (extrusion speed)
• 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).

Sources:

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