steel pipe

Abstract

[Problem] Ensuring corrosion resistance of the welded area and its vicinity even in highly corrosive environments. [Solution] The steel pipe of the present invention comprises, in any cross-section: a first region containing a first cladding layer with a predetermined composition, a second region containing a second cladding layer with a predetermined composition, and a third region located between the first and second regions and containing a third cladding layer. The third cladding layer, in terms of its metallic microstructure, comprises: phase A dispersed in the third cladding layer, and phase B concentrated at the interface portion on the steel substrate side of the third cladding layer; phase A accounts for a total proportion of 30.0% to 70.0% relative to the total cross-sectional area of ​​the third cladding layer; in the third region, the length of the region where the thickness of the third cladding layer is less than 5.0 μm is less than 100.0 μm, and the proportion of the region with a thickness less than 5.0 μm relative to the overall length of the third cladding layer is 40.0% or less.

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