| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-rigidity high-strength thin steel sheet combining a high strength of≥590 MPa tensile strength and a high rigidity of≥240 GPa Young's modulus and a method for producing the same. SOLUTION: The high-rigidity high-strength thin steel sheet has a composition which consists of, by mass, 0.02 to 0.10% C,≤1.5% Si, 1.5 to 3.5% Mn,≤0.05% P,≤0.01% S,≤1.5% Al,≤0.01% N, 0.05 to 0.40% Nb and the balance substantially iron with inevitable impurities and in which the C, N and Nb contents satisfy 0.01≤C+(12/14)×N-(12/92.9)×Nb≤0.05 and N≤C+(14/92.9)×(Nb-0.02). The steel sheet has a structure containing a ferrite phase as a main phase and also containing, by area ratio,≥1%, in total, of a martensite phase and a bainite phase and further has≥590 MPa tensile strength and≥240 GPa Young's modulus. COPYRIGHT: (C)2006,JPO&NCIPI
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