Research Article

Hot semi-punching and cold scrap removing processes for hot stamping of ultra-high strength steel parts

Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan

^* e-mail: mori@plast.me.tut.ac.jp

Received: 11 March 2015
Accepted: 8 April 2015

Abstract

Hot semi-punching and cold scrap removing processes for hot stamping of ultra-high strength steel parts were developed to eliminate laser cutting having low productivity after hot stamping. A quenchable steel sheet is semi-punched without separation of punching scraps during hot stamping, and subsequently, the scraps are removed from the hot-stamped part at room temperature. For hot semi-punching, additional channels for taking the punching scraps out of dies are not required. Minimum remainder without separation of punching scraps and no clearance between the die and punch were optimal for the hot semi-punching process. The hot punching and cold removing loads of the quenched sheet were considerably smaller than the cold punching load, the quality of the hole edge was high and the delayed fracture around the sheared edge was prevented. Hot semi-punching and cold scrap removal were applied to a hot hat-shaped bending process.