Steel for lower plate of cargo oil tank of tanker

Abstract

The invention provides steel for the lower plate of a cargo oil tankof a tanker, which belongs to the technical field of ship plate steel. The steel comprises, by mass, 0.01 to 0.3% of C, 0.02 to 2% of Si, 0.1 to 2.0% of Mn, no more than 0.01% of S, no more than 0. 02% of P, 0.05 to 2.0% of Ni, 0.05 to 2.0% of Cu, 0.005 to 1.0% of Cr, 0.0005 to 0.3% of Se, 0.0005 to 0.3% of Ge, with the balance being Fe; preferably, (Cu + Ni + Cr) / S is 200 to 480. The steel can also comprise one or more selected from the group consisting of 0.0005 to 0.3% of Sn, 0.0005 to 0.3% of Sb and 0.0005 to 0.3% of Te, and / or one or more selected from the group consisting of 0. 0005 to 0.3% of W, 0.0005 to 0.3% of Mo, 0.0005 to 0.3% of Co and 0.0005 to 0.3% of REM, and / or one or more selected from the group consisting of 0.0001 to 0.2% of Ca, 0.0001 to 0.2% of Mg, 0.0001 to 0.2% of Sr and 0.0001 to 0.2% of Ba. The steel has the advantages of excellent local corrosion resistance under the conditions of a high concentration of Cl<-> and a high acidity and effective prolongation of the service life of a steel plate when the steel plate is coated by a protective layer or is exposed.

Description

technical field [0001] The invention belongs to the technical field of ship plate steel, and in particular relates to a steel for the lower floor of an oil tanker's cargo oil tank. The steel for the lower floor of an oil tanker's cargo oil tank used in a coated protective layer or in a bare state can significantly improve - , Resistance to pitting localized corrosion in high acidity environments. Background technique [0002] In recent years, incidents of oil pollution to the marine environment caused by shipping have occurred frequently, and the corrosion of oil tankers, especially the corrosion of cargo oil tanks, has attracted increasing attention. The cargo oil tank is the main structure for carrying crude oil, and the protection of its bottom plate is the key to preventing crude oil leakage. Some studies in recent years have found that in the cargo oil tanks of actual large oil tankers, severe pitting corrosion occurs on the lower bottom plate, most of which are 10-30m...

AI Technical Summary

Problems solved by technology

[0004] At present, the method of primer coating or metal spraying is mainly used to reduce the corrosion of the bottom plate. However, due to the large volume of the cargo oil tank, the method of painting and spraying will inevitably bring about long construction time and high maintenance costs. During the construction of the protective layer, microscopic defects on the surface will also be brought about. These microscopic defects will become hidden dangers of local corrosion, and pitting corrosion will inevitably occur and expand.

When the protective layer is damaged, the degree of corrosion damage of the steel plate is not much different from that of bare steel. Therefore, although the method of coating and spraying reduces the corrosion of the steel plate, it does not fundamentally solve the corrosion of the bottom plate, especially local corrosion problem

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