| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet with a composite structure which has excellent fatigue properties, and is suitable for an automobile structural member to which a repeated load is frequently acted, and to provide a production method therefor. SOLUTION: The steel sheet with a composite structure comprises, by mass, 0.01 to 0.2% C,≤2.0% Si,≤3.0% Mn,≤0.08% P,≤0.03% S, 0.01 to 0.1% Al and≤0.01% N, and the balance substantially iron, and has a structural form in which a ferritic phase is isolatedly dispersed into a hard second phase. The fatigue properties of the steel sheet with a composite structure can further be improved by allowing the average ferrite grain size d and the hard second phase thickness t to satisfy the relational inequality of t(μm)>0.038×d(μm)+0.35. COPYRIGHT: (C)2004,JPO&NCIPI
|
