| 摘要 |
PURPOSE: A high-strength steel plate used by being molded to parts which absorb impact energy at a collision, such as a front side member, and displaying a high impact energy absorption power, and a method of manufacturing such a steel plate are disclosed. CONSTITUTION: In this high-strength steel plate displaying a high impact energy absorption power, the microstructure of a finished steel plate is a dual-phase structure containing ferrite and/or bainite, and having a main phase of either ferrite or bainite, and the third phase containing 3-50 vol. % of residual austenite. An average value αdyn (Mpa) of deformation stress in a 3-10 % equivalent strain range of the microstructure deformed in a strain rate range of 5x102-5x103 after pre-deformed to a degree of over 0 % to not more than 10 % in terms of equivalent strain satisfies the expression αdyn ≧ 0.766xTS+250 where TS(MPa) is the maximum stress measured by a static tension test in a strain rate range of 5x10-4-5x10-3(l/s) prior to the application of the predeformation. The steel plate has a high dynamic deformation resistance satisfying a work hardening index at 1-5 % strain of not less than 0.080.
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