47 巻 (2006) 544 号 p. 394-398
The feasibility of hot stamping of high-strength steel sheet with resistance heating was examined. Resistance heating and hot stamping experiments were conducted using rectangular blanks of high-strength steel sheet, SPFC980Y, 1.2mm thick, 80mm wide and 130mm long. The blanks were resistance-heated between a pair of parallel electrodes placed 120mm away from each other, with an AC power supply, and heating temperature was measured by thermography. The function of input energy control adopted for heating temperature control and the performance of blank holders with multiple pins designed for eliminating unequal contact of the blank with electrodes and achieving stable and homogeneous blank heating were tested. It was concluded that hot stamping with resistance heating is highly feasible, from the experimental results as follows. (1) The rectangular blank was resistance-heated up to 900°C in approximately 2.5s at an average current density of 65A mm-2 in effective value. (2) The input energy control functioned well because of the rapidness of the resistance heating. (3) The designed blank holders worked well. (4) Hot stamping, whose controller is linked to the resistance heating controller, performed successfully.