Microdeep drawability of very thin sheet steels

The purpose of the present study is to clarify the microdeep drawing characteristics of very thin sheet steels of below 0.2 mm thickness. An experimental study was conducted with specially developed experimental apparatus. In this study, a relative punch diameter Dp/t (Dp: punch diameter, t: thickness of sheet material) was chosen as an important experimental parameter and ranged from 10 to 100. Drawability was evaluated, and the similarity laws in deep drawing were examined with sheet steels of 0.05, 0.1, 0.2 and 1.0 mm thickness. For Dp/t from 10 to 100, ordinary drawability was obtained for very thin sheet steels without a large amount of blank holder pressure, and a decrease in value of limiting drawing ratio was observed with an increase in Dp/t. The similarity law of thin sheet metal drawing is adapted above Dp/t=40 because the drawing mechanism below Dp/t=20 should differ from the above Dp/t=40. The differences are also revealed in the shape of drawn cups. For Dp/t=10 and Rd/t=5.0, bending is the dominant forming mechanism since blank holder pressure has little effect on drawability and no effect on the working material during the latter half of the drawing process. Therefore, the drawing behavior seems similar to that in drawing thick sheet metals and is characterized as microdeep drawing of very thin sheet metals.