Steel for crude oil tanks and crude oil tanks with excellent corrosion resistance

摘要

By the component composition of this steel material comprising, in mass%, C: 0.03-0.18%, Si: 0.03-1.50%, Mn: 0.1-2.0%, P: 0.025% or less, S: 0.010% or less, Al: 0.015-0.049%, N: 0.008% or less, Co: 0.005-0.5%, and Sn: 0.005-0.3%, the remainder being Fe and unavoidable impurities, and by setting the dislocation density α of the steel material to within a range that satisfies the following formula (1), a steel material for a crude oil tank is obtained that has excellent general corrosion resistance in the upper plate of a crude oil tank such as a tanker oil tank unit and that also has excellent local corrosion resistance in the bottom plate of the crude oil tank. α(/m2) ≤ {1017×[%Co]×[%Sn]}/([%Al]-0.01)... (1), wherein [%M] is the content (mass%) of an element M