| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a steel for a welded structure, which is excellent in high temperature strength and low temperature toughness, is industrially stable and can be inexpensively supplied. SOLUTION: A cast slab or a steel slab has a composition comprising, by mass%, 0.005 to 0.05% C, 0.60% or less Si, 0.8 to 2.0% Mn, 0.020% or less P, 0.010% or less S, more than 0.50 to 3.0% Cr, 0.05 to 0.50% Nb in a range of satisfying Nb≥2C, 0.060% or less Al, 0.001 to 0.006% N, 0.03% or less Mo in a level of being contained as a contaminating element and not being substantially contained, and the balance Fe with unavoidable impurities; and has a P<SB>CM</SB>value of 0.24% or less. The production method comprises the steps of: heating the cast slab or the steel slab to 1,000 to 1,300°C; hot-rolling the slab with an accumulated rolling-reduction ratio of 30% or more in a temperature region at which austenite is not recrystallized; finishing the hot rolling at a temperature of 750°C or higher; and air-cooling the plate. COPYRIGHT: (C)2008,JPO&INPIT
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