2016 年 57 巻 661 号 p. 146-152
The deformation behaviour during the trimming of ultra-high-strength steel sheets was observed to reduce the flying speed of cut scraps. In the trimming of ultra-high-strength steel sheets, the flying speed is high owing to the high strength, and thus the trimming operation becomes noisy and scraps jump out from the disposal box. As the sheet strength and trimming speed increased, the flying speed became high. The flying speed for an 1180MPa sheet was accelerated to 2.7 times the free-fall speed, whereas the speed for the mild steel sheet was 1.2 times. As the strength of the sheet increased, the noise level in trimming increased. To reduce the flying speed, punches having single and double bevels were developed. Although the flying speed became high for the punch having a double bevel, the speed decreased when the punch had a single bevel. It was found that the trimming punch having a single bevel is effective in reducing the flying speed of scrap and the noise level in the trimming of ultra-high-strength steel sheets.