Steel sheets for high-strength line pipes and steel pipes for high-strength line pipes with excellent low-temperature toughness

摘要

Provided is a steel plate for a high-strength line pipe with excellent low temperature toughness that can ensure a high critical CTOD value even though separation occurs, and can be easily manufactured at low cost. In the steel plate for a high-strength line pipe, its chemical composition is adjusted appropriately, an average grain size of the steel plate is 10 µm or less in a t/4 position where t is a thickness of the steel plate, and a separation index SI measured on a fracture surface of a Charpy specimen of the steel plate at a specified temperature exceeds 0 mm/mm 2 and is equal to or less than 0.30 mm/mm 2 .