| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a thick steel sheet having superior fatigue resistance properties in the sheet thickness direction which is favorable for a welded steel structure such as a pressure vessel, and to provide a method for producing the same. <P>SOLUTION: The thick steel sheet has a compressive residual stress in the direction perpendicular to the sheet thickness direction of 100 MPa or more in the range from both sides or one side of the rolling surfaces of the steel plate to 4 mm in the thickness direction, and has a composition which preferably contains, by mass%, 0.03 to 0.15% C, 1.0% or less Si, and 1.0 to 2.0% Mn, one or two of 0.005 to 0.05% Ti and 0.001 to 0.05% Nb, 0.1% or less Al, and one or more of Cu, Ni, Cr, Mo, V, W, Zr, Ca, and B. The method for producing the thick steel sheet includes: heating a steel material having the chemical components as described above to a temperature range of 1,000 to 1,250°C, subjecting the heated steel material to hot rolling at a cumulative rolling reduction of 30% or more in a temperature region where the temperature in the central part of the sheet thickness is (a temperature of Ar3 point+50)°C or more and then cooling the hot-rolled steel sheet to 350°C or less at a cooling rate of 3°C/s or more. <P>COPYRIGHT: (C)2013,JPO&INPIT |
