Body Audi A2: aluminum alloys and technologies

Audi A2 - is the first mini-car with an all-aluminum body, which is produced in large volumes. Its production started in 1999 year. It was the second generation of the technology of spatial self-supporting aluminum body. The first generation was aluminum body Audi A8 (D2).

Aluminum body Audi A2

audi-a2Figure 1 - Audi A2

Audi partner companies to develop aluminum body Audi A2 was a company Algroup Alusuisse, which later became known as the Alcan.

Weight aluminum body Audi A2 was only 153 kilograms - on 43 % smaller, than that of comparable conventional steel body. The total weight of the car Audi A2 version 1.2 TDI with forged aluminum wheels and special tires was only 825 kilograms. It was the world's first five-door "three-liter" car - the average fuel consumption was 2,99 liters 100 kilometers.

aljuminievyj-kuzov-audi-f2Figure 2 - The aluminum space frame Audi A2

Self-supporting body Audi A2 includes (by weight):

  • 60 % aluminum sheet panels;
  • 22 % aluminum castings;
  • 18 % aluminum extrusions.

Compared with the earlier manufacturing technology Audi A8 aluminum body Audi A2 has undergone significant changes. So, the number of individual parts has been significantly reduced: from 334 parts 225 details:

  • stamping: 183 (81 %);
  • profiles: 22 (10 %);
  • castings: 20 (9 %).

This was achieved by combining the various components into larger parts, mainly profiles or multifunctional castings.

aljuminievyj-kuzov-audi-a2-komponentyFigure 3 - Exploded View
aluminum body Audi A2

aluminum castings

Cast aluminum body parts were fabricated by vacuum casting technology under high pressure. Tight control technology ensures that the parameters, all molded pieces can be properly welded to the sheet metal stampings and extruded profiles using laser welding and MIG welding.

For cast body parts used foundry aluminum alloy AlSi10MgMnFe.

Heat treatment of aluminum castings was optimized so, to achieve high strength and good ductility of the material at low warpage their shape during cooling during hardening.

aljuminievye-otlivki-audi-a2Figure 4 - Structural body component
of three thin-walled aluminum castings

These thin-walled and complex shaped castings, are welded together using MIG method, provide high body resistance to collapse on impact.

The lower part of the aluminum body Audi A2 is formed of straight extruded profiles, are connected to each other by welding MIG, which allowed to exclude part of the cast of the attachment, which have been used in the body of the Audi A8.

Extruded aluminum profiles

Most of the extruded aluminum body components were fabricated by hydroforming. It gave them strict geometric tolerances for straight and curved profiles. However, hydroforming technology not only provides the ability to control the molding with a narrow geometric tolerances. Hydroforming operation may be combined with the punching operations, dimensional cutting into lengths and processing flanges. The figure 5 It is shown by the example of the side body frame roof.

For all alloy extrusions used 6014.

aljuminievye-profile-audi-a2Figure 5 - lateral roof frame body Audi A2,
manufactured by the hydroforming method

aluminum sheet

Aluminium alloy 6016 in the state before artificial aging PX (the pre-aged state PX) was used for the outer panels of the body. Aluminum Alloy 6181A was used for internal and bearing panels.

Three technologies of joining aluminum materials with each other were used to assemble the spatial body structure:

  • "Samoprokalyvayuschie" rivets - 1800 pcs,
  • cварка ME - 20 m,
  • Laser welding - 30 m.

Aluminum alloy body Audi A2

ximsostav-aljuminievyx-splavov

It is believed, that their design decisions Audi A2 was ahead of its time. However, the design and technological breakthrough, Unfortunately, I have not received due recognition buyers. The Audi company was disappointed with the level of sales of the Audi A2: the total production of these cars was only about 175 thousand units.

A source: The Aluminium Automotive Manual, The European Aluminum Association, 2013