Aluminium shaping - Spinning or extrusion

The extrusion deformation process, although used for lead since 1797 (by Bramah in Great Britain) and then developed for copper metals during the 19th century, was not really applied industrially to aluminum until the early 1920s. Since then, its use has grown steadily, with a marked leap forward in the 1960s as a result of the significant penetration of aluminum alloy profiles in the metal joinery sector.

Today, extrusion can be considered - after rolling, however - as one of the major and essential processes for shaping aluminum and its alloys:

• on the one hand, the progress made over the last few decades means that this technique lends itself admirably to the production of spun products with extremely varied, even highly sophisticated shapes and profiles;

• on the other hand, there are a large number of aluminium alloys suitable for extrusion, and thanks to the wide variety of their properties, they can be considered to be of high quality.

adapted to the various applications that are opening up for extruded aluminum products, applications that currently cover a wide variety of fields, the most important of which are transport (aerospace, land, sea), construction, mechanical engineering, etc.

In this article, we describe the specific characteristics of aluminium and its alloys, examining them in turn:

• technological aspects (processes, tools, lubrication) ;

• conditions and possibilities of deformation by extrusion: pressures, temperatures, speeds, dimensional limits, influence of the nature of the alloy and any prior heat treatments;

• metallurgical aspects (including the press-hardening process) ;

• the aluminum alloys most commonly used in extrusion.

It should be noted that it is common practice in aluminum alloy extrusion shops to distinguish between two types of alloy:

• Mild" alloys: alloys in the 1000, 3000, 5000 (with Mg ) and 6000 series have good or very good spinning properties;

• hard" alloys: 2000, 7000 and 5000 series alloys (with Mg