1997-02-24

Aluminum As-Rolled Sheet for Automotive Applications - Effect of Surface Oxide on Resistance Spot Welding and Adhesive Bonding Behavior 970013

In the automotive industry there is a considerable interest to reduce fuel consumption and exhaust fumes. Aluminum materials for car body panels parts such as doors, hood and trunk, have already proved to be an excellent solution for weight saving.
However the excess cost induced by weight saving must be kept as low as possible; therefore, aluminum production costs must be controlled.
With this aim, Pechiney has developed AA 5182 alloy sheets for inner parts without any surface treatment of the material. Aluminum sheets have been rolled under varying conditions in order to obtain different surface oxides. These products were tested for their joining behavior, especially resistance spot welding and adhesive bonding.
The objectives of the study were to determine the effect of rolling parameters and of storage on the oxide film and to compare the weldability lobes and the bonding strength for the different identified oxidation conditions.
For spot welding all the results are compatible with industrial requirements:
  • welding current range higher than 3,000 A,
  • electrode life above 400 welds without any electrode tip cleaning.
For adhesive bonding, the strength of the bond is not modified by the different surface oxides either for epoxy or for mastic adhesives, even after humid aging of oily surfaces.
From these results, it can be concluded that it is possible to use aluminum panels for resistance spot welding and for adhesive bonding without the necessity of preliminary surface treatment.

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