| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot rolled steel sheet having excellent fatigue properties and an excellent balance in strength-stretch flange formability. SOLUTION: The hot rolled steel sheet having excellent fatigue properties and stretch flange formability has a composition comprising, by mass, 0.01 to 0.10% C,≤2.0% Si and 0.5 to 2.5% Mn, and further comprising one or more kinds of elements selected from V, Nb, Ti, Mo, Zr and W by 0.01 to 0.30%, respectively, and also, satisfying equations (1) and (2), and the balance Fe with inevitable impurities; wherein a ferrite fraction is >90%, a ferrite grain size is≤10μm, a precipitate average grain size r(nm) satisfies equation (3) (X(V-W) is expressed by equation (5)), and the average grain size r and a precipitation fraction f satisfy equation (4). COPYRIGHT: (C)2009,JPO&INPIT
|
