Production of the second generation Audi A8 - Audi A8 (D3) - began in 2002 year.
From Audi A8 (D2) to Audi A8 (D3)
The number of parts of the aluminum body of the Audi A8 (D3) has been reduced, and the degree of automation in its manufacture has been significantly increased compared to the body of the previous model Audi A8 (D2).
A feature of the body structure of the Audi A8 (D3) is the use of multifunctional large aluminum castings and a large proportion of straight extruded profiles. Curved profiles were used only where, where necessary on the outer skin. Therefore dolz sheet panels in a body fell from 55 to 37 % (by weight), while the percentage of castings increased from to 34 %, and profiles - up 29 %.
Weight all-aluminum bodywork version of the car Audi A8 D3 - pure body, without doors and other removable parts (then, which in English is called body-on-white) - is 277 kilograms.
Aluminum profiles and sheets
As the aluminum alloy sheet alloy is used 6016 for the outer skin and the alloy 6181A - for interior trim panel and power panels. 6xxx series aluminum alloys, Similar to Alloy 6060, used in the manufacture of extrusions.
For manufacturing aluminum castings, besides molding under high pressure in steel split form, It was used as the method of molding in "wet" sand molds. For casting steel separable mold casting aluminum alloy used AlSi10Mg, and for sand casting - Alloy AlSi7Mg.
The use of large multifunctional castings and the desire to combine functions made it possible to reduce the number of body parts (table 1).
Methods for joining aluminum parts
In the production methods of model D3 body parts compound, used in model D2 (MIG welding and self-piercing rivets), as well as laser welding, which was introduced on the Audi A2, further developed. Moreover, It was first introduced hybrid welding, not only the advantages of combined MIG welding and laser welding, but it made it possible to increase the performance of the body assembly.
MIG welding is used mainly for the connection of individual extruded aluminum profiles, castings, produced by high pressure casting, as well as compounds extrusions to castings.
Laser welding is used mainly for the connection of wide sheet panels to the frame body. Laser welding is also used to connect the panels with hollow profiles and hollow castings.
Technology samoprobivnyh rivets used in increased volumes for joining together sheet panels, extrusions and castings of different aluminum alloys to form a total thickness of 2 to 6 mm. Three different types of rivets used for the same hardness of about 100 different combinations of materials and thicknesses. Moreover, applied 17 meters of bonded joints.
The internal and external panels and door trim joined by seaming, and special bonding using robotic devices. The advantage of this method is the rapid adjustment of the equipment, its high flexibility, and high quality and good appearance of the seam. Rejection of adhesive produced by induction heating.
A source: The Aluminium Automotive Manual, The European Aluminum Association, 2013