To effectively improve impact collapse resistance by minimizing the formation of a hardening-strengthened part while securing excellent press formability.
The member is a steel plate member 1 prepared by press- forming a steel plate containing, by weight, 0.05-0.3% C and 0.5-3.0% Mn. In the cross section of the steel plate member 1, a reference range of (R+7)mm (where R is the radius of a corner part) is set from the center P of a corner part at least on either of two planes forming the corner part, and one or plural hardening-strengthened parts 4 are formed a long the corner part within the reference range. Further, with respect to all the planes forming all the corners of the steel plate member 1, the occupancy ratio of the total width of the hardening-strengthened parts 4 within the reference ranges to the total length of the reference ranges is regulated to ≥20%.
TOYODA TETSUO
WATANABE KENICHI
SATO AKIHITO
TAMADA KENJI
TOYOTA MOTOR CORP