A study of the formability of stainless steel foils during micro deep drawing

Stainless steel foils are extensively used in the manufacture of micro-metallic products for their excellent corrosion resistance, high mechanical strength and superior ductility. In the present work, stainless steel foils with 50 μm thickness were annealed at temperatures ranging from 750 to 1150 °C for 5 min and then cupped at drawing speeds ranging from 0.1 to 2 mm/min. The formability of metal foils was systematically investigated and the quality of drawn cups via micro deep drawing (MDD) was discussed. The results show that the total elongation of metal foils appears a gradual increase when annealing temperature rises from 750 to 950 °C. With a further increase of annealing temperature from 950 to 1150 °C, both the ultimate tensile strength and the total elongation decline sharply, while the scatter of stress increases. The results of MDD tests show that wrinkling problem becomes increasingly significant on the drawn cups whilst thickness distribution on the drawn cup mouth become quite nonuniform with the increase of drawing speed from 0.1 to 2 mm/min. Overall, optimal annealing temperature and drawing speed are obtained with the purpose of manufacturing high quality micro circular cups.