Press-Formed Steel Member With Overlapping Flanges for Bending Safety

The patent applies hot stamping process which involves heating the steel sheet to austenite region and then rapidly cooling it to achieve tensile strength of 1320 MPa or more. This parameter change (temperature control during forming) allows high strength to be achieved while maintaining formability during the forming process.

The patent performs forming operations on the steel sheet before final hot stamping. The forming is conducted on a relatively soft, formable material state, and then the hot stamping process transforms it to high strength after forming, thus avoiding the workability issues of high strength materials during forming.

The patent creates ridge lines by forming projecting portions that extend in the longitudinal direction of the member. This dimensional approach (extending features along the length) increases the number of ridge lines without requiring complex cross-sectional geometries, thus improving collision safety while controlling structural complexity.

The patent divides the top plate portion into multiple segments by creating projecting portions at different positions. This segmentation creates multiple ridge lines that enhance collision safety while maintaining a relatively simple overall structural configuration.

Instead of forming recessed portions by pressing inward on the wall portions (which requires high precision), the patent forms projecting portions that extend outward from the boundary between vertical wall portions and top plate portion. This inverted approach creates similar structural benefits with reduced precision requirements.

The patent creates local projections at specific boundary regions between vertical wall portions and top plate portion, rather than forming recesses across entire wall surfaces. This localized approach improves collision safety through strategic reinforcement while reducing overall manufacturing precision requirements.