| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the impact energy absorption power of a steel sheet by allowing the average value of the deformation stress in the case deformation is generated in a specified strain rate range after the application of predeformation in a specified range of equivalent strain to a steel having a specified compsn. to satisfy specified relation. SOLUTION: The microstructure of a steel sheet contg. C, Si, Al, Mn, Ni, Cr, Cu and Mo is composite one contg. ferrite and bainite, in which either of them is used as the main phase and third phase contg. >=3 vol.% retained austenite. Furthermore, the average valueσdyn (MPa) of the deformation stress in the equivalent strain range of 3 to 10% in the case deformation is generated in the strain rate range of 5×10<2> to 5×10<3> (1/s) after the application of predeformation of >0 to 10% at equivalent strain to this steel sheet satisfies the inequality ofσdyn >=0.766×TS+250 expressed by the maximum stress TS (MPa) in a static tension test measured at the strain rear of 5×10<-4> to 5×10<-3> (1/s) before the application of the predeformation.</p> |
