Improvements in productivity and formability by water and die quenching in hot stamping of ultra-high strength steel parts

To improve the productivity in hot stamping of ultra-high strength steel parts, the parts are quenched not only with dies but also in water during holding at the bottom dead centre. Since the cooling speed for water quenching is higher than that for die quenching, the hold time for hardening is reduced. In hot stamping, water is kept in a lower die to increase the cooling rate during die quenching. In addition, local thinning around the punch corner was prevented by water and die quenching, and thus the drawablity increases.