| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet excellent in strength uniformity in a sheet width direction and a manufacturing method therefor.SOLUTION: A high strength hot rolled steel sheet has a component composition containing, by mass%, C:0.10 to 0.25%, Si:0.10% or less, Mn:1.0 to 2.0%, P:0.025% or less, S:0.005% or less, Al:0.005 to 0.10%, Nb:0.01 to 0.05%, Ti:0.005 to 0.05%, Cr:0.05 to 1.0%, B:0.0005 to 0.0050% and the balance Fe with inevitable impurities and a structure with tempered martensite phase of 95% or more by volume percentage based on whole structure, average particle diameter of old austenite particle of 20 μm or less in a cross section parallel to a rolling direction and 15 μm or less in a cross section orthogonal to the rolling direction. Yield strength (YS) is 960 MPa or more.SELECTED DRAWING: None |
