Corner Strengthening by Local Thickening and Ausforming Using Planar Compression in Hot Stamping of Ultra-High Strength Steel Parts

Abstract

Hot-stamped products are widely used for the body-in-white of an automobile as they are lightweight and improve crashworthiness. A hot-stamping process using planar compression was developed to strengthen corners of ultra-high strength parts by local thickening and hardening. In this process, the corners are thickened by compressing the blank in the planar direction with the upper and lower dies while blocking the movement of both edges with stoppers in the latter stage of forming. Thickening of the corners largely heightens the strength of the formed parts. Not only the thickness but also the hardness of the corner was increased by large plastic deformation and die quenching. For a hot hat-shaped part, a 30% increase in thickness and a 530 HV20 hardness around the corners were attained. The bending rigidity and strength of the formed parts thickened by 30% in the corners increased by 25% and 20%, respectively. In addition, the improvements of the part shape accuracy and the sidewall quenchability were obtained.

Prevention of peeling of Al-Si coated layer in hot stamping using corner thickening by planar compression

“…Although the thickness distribution of components is changed by using tailor welded and rolled blanks, the change is partial, and these blanks are not suitable for local thickening around the corners. Maeno et al [5] have developed the corner strengthening by local thickening using planar compression in hot stamping. Not only the thickness but also the hardness of the corner was increased by large plastic deformation and die quenching.…”