METHOD FOR MANUFACTURING THICK HIGH-STRENGTH STEEL SHEET HAVING SUPERIOR CHARACTERISTICS OF STOPPING PROPAGATION OF BRITTLE CRACK SHEET AND SHEET THICKNESS OF 50-125 mm

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, superior characteristics of stopping the propagation of a brittle crack and a sheet thickness of 50-125 mm.;SOLUTION: This manufacturing method includes: heating a steel slab having an appropriate chemical composition to 950-1,150°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 Ar₃-60°C to Ar₃; subsequently acceleration-cooling the finish-rolled material to 200°C or lower with a cooling rate of 8°C/s or more by average in a sheet thickness; subsequently heating the steel sheet with a temperature-raising rate of 1°C/s or more on the surface while keeping the surface of the steel sheet at a higher temperature than that in the central part in the sheet thickness direction by 30°C or higher; stopping heating when the surface of the steel sheet has reached 400-650°C; and tempering the steel sheet on the condition of keeping the surface at 400-650°C.;COPYRIGHT: (C)2011,JPO&INPIT