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This study was carried out to investigate the CO2 laser weldability of aluminum alloy sheets for the welding of hemmed region. Efforts were made to obtain the best bead dimension for hemming welding. Thus, a following criterion was formulated: a hemming bead which has less than 0.8 mm of welding depth and more than 1.0 mm of welding width works satisfactorily for hemming joint in terms of both strength and visual appearance. The dimension of hemming bead was greatly affected by surface conditions as well as welding parameters. Clean surface condition coupled with helium shielding gas produced a most sound welding bead. The effect of lubricant on the formation of welding defect was also investigated. It was found that the welding defect, i.e., porosity in the weld zone, was caused by the lubricant at the surface and degraded the strength of weld joint. The laser welding did not soften both the heat affected zone (HAZ) and weld zone of aluminum alloy sheets in this study.

A new joining method has been attempted in aluminum hood application to join steel reinforcements to aluminum inner panel. This method, Tox mechanical clinching(TMC), offers the best cost performance and productivity among several joining methods. This paper was focused on the practical understanding of TMC method and its applicability to aluminum hood manufacture. The results of this study showed that design by the TMC could be much easier than that by resistant spot welding(RSW) because TMC produced very reliable and consistent joint strength at the multipoint situation. The only drawback of this method was the low joint strength due to very small joint area. In order to maintain similar joint strength as that of steel hood welded by RSW, the number of TMC points should be increased. Approximately two times of more TMC points produced no problems during durability test of aluminum hood.