Improvement of formability using partial cooling during transfer in hot stamping of ultra-high strength steel parts

摘要

The formability in hot stamping was improved by partial cooling of a heated sheet during the transfer from a furnace to dies. Using the transfer device having grips on the heated sheet, the temperature of the portions undergoing large deformation during forming is decreased to increase the flow stress. The cooling pressure and the contacting width in transfer device were changed to control the temperature distribution in the sheet. In W-bending, a temperature difference of 250°C and a flow stress difference of 300 MPa were obtained, and the depth of the W-bent sheet was increased by 26.1%.