VEHICLE COLLISION ENERGY ABSORBING MEMBER HAVING HIGH COLLISION ENERGY ABSORBING POWER, AND METHOD FOR MANUFACTURING SAME

摘要

Provided is a vehicle collision energy absorbing member excellent in collision energy absorbing performance in the axial direction upon collision. The vehicle collision energy absorbing member is formed of a high strength thin steel sheet having TS of at least 980 MPa and having an n-value and a limit bending radius Rc satisfying the following Formula: Rc / t ‰¤ 1.31 x ln(n) + 5.21. The use of the aforementioned high strength thin steel sheet allows the member to be stably buckled in the axial direction and crush-deformed into a bellows shape upon vehicle collision even if TS is 980 MPa or above. The high strength steel sheet used herein preferably includes a chemical composition containing, by mass%: C: 0.14 % to 0.30 %; Si: 0.01 % to 1.6 %; Mn: 3.5 % to 10 %; N: 0.0060 % or less; and Nb: 0.01 % to 0.10 %, and has a microstructure including a ferrite phase by 30 % to 70 % in volume fraction with respect to the entire microstructure and a secondary phase other than the ferrite phase, the ferrite phase having an average grain size of 1.0 µm or smaller, the secondary phase at least containing a retained austenite phase by at least 10 % in volume fraction to the entire microstructure, the retained austenite phase having an average spacing of 1.5 µm or less.