SHIP STRUCTURAL STEEL AND SHIP WELDED STRUCTURE HAVING EXCELLENT CORROSION RESISTANCE

摘要

A steel material for a ship, which exhibits excellent resistance to crevice corrosion and the like in a wet atmospheric environment such as a ballast tank and a crude oil tank to which electrical corrosion protection is not applied, and a welded structure using the steel material are provided. A steel material for a ship having excellent corrosion resistance comprises 0.04 to 0.18 mass% of C, 0.1 to 0.50 mass% of Si, 0.10 to 1.8 mass% of Mn, 0.05 to 0.40 mass% of Al, 0.05 to 4.00 mass% of Cu, 0.05 to 4.50 mass% of Cr, 0.05 to 4.50 mass% of Ni, 0.008 to 0.20 mass% of Ti, 0.0010 to 0.015 mass% of Ca and 0.0005 to 0.020 mass% of Mg, and P and S of which contents are controlled to not more than 0.020 mass%(including 0 mass%) and not more than 0.010 mass%(including 0 mass%) respectively with the balance being Fe and inevitable impurities. A value([Cr]/[Al]) of a ratio of a Cr content [Cr] to an Al content [Al] is 1 to 50.