| 摘要 |
A high strength hot rolled thick steel sheet has a tensile strength of 440 to 640 MPa, preferably 490 to 590 MPa, and an elongation of 20% or more; is excellent in uniformity in a sheet thickness direction and in strength and toughness after heat treatment; and is suitably used for structural components of automobiles, construction machines, and the like, and a method for manufacturing the hot rolled thick steel sheet. A steel material having a composition including C: 0.10 to 0.20%, Ti: 0.01 to 0.15%, B: 0.0010 to 0.0050%, and proper amounts of Si, Mn, Al, P, S, and N is hot-rolled at a finisher delivery temperature of 820 to 880� C. in finish rolling, is cooled at a cooling rate of 15 to 50� C./s until a temperature reaches a cooling stop temperature of 500 to 600� C., and is coiled. |
