High-strength steel sheet for sour line pipes, method for producing the same, and high-strength steel pipe using high-strength steel sheets for sour line pipes

摘要

The present invention provides a high-strength steel plate for a sour line pipe having excellent HIC resistance and SSCC resistance under a more severe corrosive environment and excellent hardness uniformity in the thickness direction. The high-strength steel sheet for a sour line pipe of the present invention has a predetermined component composition, and the steel structure at 0.5 mm below the steel sheet surface has a dislocation density of 0.5 × 1014 to 7.0 × 1014 (m−2). The difference ΔHV between the average value of Vickers hardness at 0.5 mm below the steel sheet surface and the average value of Vickers hardness at the center of the steel sheet thickness is 25 HV or less, and has a tensile strength of 520 MPa or more. It is characterized.