Steel for chemical tank, excellent in sulfuric acid corrosion resistance and pitting corrosion resistance

摘要

The present invention provides a steel for a chemical tank, the steel suppressing the generation of corrosion damage by sulfuric acid and pitting corrosion by salt water, and is a steel for a chemical tank, the steel being excellent in sulfuric acid corrosion resistance and pitting corrosion resistance, characterized in that: the steel contains, by mass, C: 0.003 to 0.05%, Si: not more than 5%, Mn: not more than 2%, P: not more than 0.03%, S: not more than 0.010%, O: not more than 0.0050%, Cr: 18 to 25%, Ni: 10 to 20%, Mo: 1.0 to 4.5%, Cu: 1.0 to 3.0%, and N: 0.05 to 0.3%, with the balance consisting of Fe and unavoidable impurities; the GI value defined by the expression GI = [Cr] + 1.6 x [Ni] + 6.0 x [Mo] + 7.1 x [Cu] is in the range from 75 to 88, wherein the relevant components are expressed in terms of a mass percent; and the PI value defined by the expression PI = [Cr] + 1.3 x [Mo] + 1.4 x [Cu] + 2.2 x [N] is in the range from 23 to 32, wherein the relevant components are expressed in terms of mass percent.