抄録
Highly corrosion-resistant stainless-steel sheets have been increasingly used in various applications. In press forming, however, workpieces of stainless-steel sheets more easily adhere to die tools than to other metals. In this study, we propose to apply sintered polycrystalline diamond (PCD) to die tools used for press forming. Die tools made of sintered PCD can be fabricated by electric discharge machining. We carried out a deep drawing experiment on a thin SUS304 stainless-steel sheet using die tools made of sintered PCD (a die and a blank holder). It was found that the drawing limit was improved using the PCD tools compared with the conventional tool made of alloy tool steel (SKD11), because the coefficient of friction between the PCD tools and the workpiece was reduced. Moreover, we carried out 5,000 continuous deep drawing experiments without lubricant. For the conventional tool, the workpiece started adhering to the die immediately after the start of drawing, and large flaws were observed on the side wall of the drawn products. For the PCD tools, the workpiece never adhered to the tools during drawing, and high-precision- drawn products were stably obtained for up to 5,000 drawing experiments.
