TÔLE D'ACIER ÉPAISSE POUR TUYAU DE CONSTRUCTION, PROCÉDÉ POUR LA PRODUCTION DE TÔLE D'ACIER ÉPAISSE POUR TUYAU DE CONSTRUCTION ET TUYAU DE CONSTRUCTION

摘要

Disclosed is, as a high-strength steel plate of API X80 grade or higher with a thickness of 38 mm or more, a thick steel plate for structural pipes or tubes that exhibits high strength in the rolling direction and excellent Charpy properties at its mid-thickness part without addition of large amounts of alloying elements. The thick steel plate for structural pipes or tubes disclosed herein has: a specific chemical composition; a microstructure at its mid-thickness part that is a dual-phase microstructure of ferrite and bainite with an area fraction of the ferrite being less than 50 %, and that contains ferrite grains with a grain size of 15 µm or less in an area fraction of 80 % or more with respect to the whole area of the ferrite; a tensile strength of 620 MPa or more; and a Charpy absorption energy vE -20 °C at -20 °C at the mid-thickness part of 100 J or more..