Steel material having excellent corrosion resistance

Abstract

Disclosed is a steel material having excellent corrosion resistance, which is characterized by the following properties (A) to (C); (A) the steel material comprises the following components (by mass) as essential components: C: 0.02-0.15%, Si: 0.10-1.0%, Mn: 0.1-1.5%, S: 0.02-0.5%, Ti: 0.02-0.15%, Ca: 0.0001-0.01% and Al: 0.01-0.50%, and contains at least one component selected from Cu in an amount of 0.05-3.0% and Ni in an amount of 0.05-6.0%, with the remainder being Fe and unavoidable impurities, wherein the contents of Ni, Cu, S and Ti have the relationship represented by the following formula: [(Ni+4.5xCu)xSx2500xTi>5]; (B) the surface of the steel material is covered with a rust containing S in an amount of 0.3-5.0% by mass and further containing at least one element selected from Ti, Cu, Ni, Nb, Zr and V in the total amount of 0.5-10.0% by mass; and (C) a rust layer is formed on the surface of the steel material, wherein the crystallite size of a ss-FeOOH component in the rust layer is less than 50 nm as measured by the X-ray diffraction method, and the rust layer has a specific surface area of 10 m / g or greater as measured by the molecular adsorption method.

Description

technical field [0001] The present invention relates to materials suitable for steel structures such as civil engineering, construction, iron towers, bridges, construction machinery, steel pipes, storage tanks, etc., especially steel structures that require excellent corrosion resistance in an air-polluted environment with many sulfur oxides It is a steel material with excellent corrosion resistance as the raw material of the object. Background technique [0002] In general, the corrosion of steel is severe in heavy chemical industry areas, sulfur oxides and dusty air pollution environments accompanied by coal combustion, hot spring areas and volcanic areas with sulfur and hydrogen sulfide, and the reason is considered to be Slightly acidic environment due to sulfur oxides. As one of the corrosion-resistant materials suitable for this environment, alloy steel has been used conventionally. [0003] Conventionally, steel containing Cr and Ni to improve corrosion resistance h...

AI Technical Summary

Problems solved by technology

[0011] However, the existing steel products do not have excellent exposed corrosion resistance under acid rain with a pH of 4.5 or less and air pollution with a lot of sulfur oxides, and cannot be used in civil engineering, construction, iron towers, bridges, construction machinery, steel pipes, storage, etc. Exhibit high corrosion resistance for steel structures such as tanks

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