| 摘要 |
PROBLEM TO BE SOLVED: To provide a method which can industrially stably and effectively manufacture a thick high-strength steel sheet that has sufficient arrestability as a large-scale structural steel and is superior in characteristics of stopping the propagation of a brittle crack. SOLUTION: When heating a steel slab having an appropriate chemical composition to 950-1150°C, rough-rolling the steel slab with a cumulative rolling reduction of 30% or more at 900°C or higher, finish-rolling the rough-rolled material with a cumulative rolling reduction of 40% or more within a surface temperature range of Ar<SB>3</SB>to Ar<SB>3</SB>+60°C, subsequently acceleration-cooling the surface to 200°C or lower from a temperature of Ar<SB>3</SB>or higher with a cooling rate of 8°C/s or more by average in a sheet thickness and then tempering the steel sheet, this manufacturing method includes: setting a time interval after the end of the acceleration cooling before the start of tempering, at one hour or shorter; and heating the steel sheet to 400-650°C with a temperature-raising rate of 1°C/s or more by average in a sheet thickness. COPYRIGHT: (C)2011,JPO&INPIT
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