| 摘要 |
PROBLEM TO BE SOLVED: To provide a DP type high strength steel plate selected based on optimum characteristics and standards as the one for absorbing impact energy in the case of a collision and certainly contributable to the security of safety. SOLUTION: This steel plate is the one having a compsn. contg., by weight, 0.02 to 0.15% C, 0.01 to 2.5% Si, 0.8 to 2.5% Mn, and the balance Fe with inevitable impurities and a structure essentially consisting of ferrite and contg. other low temp. formed phases including 3 to 30 vol.% martensitic phases, in which the ratio of the yield strength YS(0) to the maximum strength TS(5) in a tensile test after the application of predeformation of 5% as equivalent distortion, i.e., YS(0)/TS(5) is regulated to <=0.7, and after the application of predeformation of >0 to 10% as equivalent distortion, the difference (σd-σs) between the quasistatic deformation strengthσs and the dynamic deformation strengthσd is regulated to >=60 MPa. Furthermore, it lies in the range of (σd-σs)>=4.1×σs<0.8> -σs. Also, as for the case in which predeformation is applied by skinpass rolling or/and a tension leveller, prescriptions are made.
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