Cryogenic Sheet Metal Forming - An Overview

Despite extensive efforts to improve energy efficiency in the automotive sector, the use of light-weight aluminium alloys for car bodies is impeded by formability limitations. Although it is a known phenomenon that Al alloys increase their strength and ductility at very low temperatures, it has not been attempted to exploit this effect to increase their overall formability at an industrial scale. Over the last four years, the cryogenic sheet metal forming behaviour of Al-alloys was extensively investigated to establish a process robust enough for manufacturing automotive parts at an industrial level. Initial experiments include tensile tests at temperatures down to -196 degrees C for characterisation of 5xxx and 6xxx series Al alloys, providing the mechanical material data for numerical design simulations of sheet metal forming processes at cryogenic temperatures. Numerical simulations will not be discussed in this publication. Furthermore, the necessary hardware for cryogenic sheet metal forming was developed and finally resulted in a semi-automated small scale industrial production site. The production of a miniaturized B-Pillar was demonstrated for 5xxx and 6xxx alloys. Due to the part's demanding geometry, defect-free deep drawing process is possible at cryogenic temperature only. These results demonstrate that the use of Al alloys could be extended beyond their current applications in cars components. For example, the overall formability of 5xxx series alloys nearly doubles compared to room temperature. This paper shall give an overview over our work in the field of cryogenic aluminium sheet metal forming within the last couple of years.