| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material for the bottom plate of a crude oil tank in which both of local corrosion resistance and coating corrosion resistance are excellent. SOLUTION: The steel material for the bottom plate of a crude oil tank has a composition comprising 0.01 to 0.3% C, 0.01 to 2% Si, 0.01 to 2% Mn, 0.005 to 0.1% Al, 0.01 to 1% Cu, 0.01 to 1% Cr, 0.0001 to 0.005% Ca, 0.005 to 0.2% Ti and 0.01 to 1% Ni, and the balance Fe with inevitable impurities, and has a structure composed of, by area ratio, 5 to 25% pearlite, <20% bainite and <10% martensite, and the balance ferrite, and in which the number per unit area of nonmetallic inclusions whose diameter of the equivalent circle exceeds 20μm is≤0.20 pieces/mm<SP>2</SP>. COPYRIGHT: (C)2008,JPO&INPIT
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