STEEL PIPE AND STEEL SHEET

• Main Authors: HATTORI Yutaka, SHINOHARA Yasuhiro, EBIHARA Kiyoshi, HASHIMOTO Akira, HARA Takuya, ABE Nozomu, TSUTSUI Kazuteru
• Format: Patent
• Language: English; French; German
• Published: 05.05.2021
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; METALLURGY; TREATMENT OF ALLOYS OR NON-FERROUS METALS

This steel pipe has a base material portion composed of a tubular steel plate having a predetermined chemical composition and a welded part that is provided at a butt portion of the steel plate and extends in the longitudinal direction of the steel plate, an internal microstructure includes 85% or more of one or both of granular bainite and bainite in terms of the total area ratio and includes 1.0% or less of an MA in terms of the area ratio, the internal microstructure has a maximum hardness of 248 Hv or less and an average hardness of 170 to 220 Hv, the base material portion has a texture having an integration degree of {100} of 1.5 or more in a plane parallel to a plate surface at a 1/4 position of a plate thickness from the surface in a plate thickness direction, a surface layer area microstructure includes 95% or more of one or both of granular bainite and tempered bainite in terms of the total area ratio, the surface layer area microstructure has a maximum hardness of 250 Hv or less, and the steel plate has a plate thickness of 15 mm or less.