| 摘要 |
<p>Provided is a steel pipe for a linepipe with high compressive strength and a heavy wall thickness which can suppress lowering of yield stress caused by a Bauschinger effect by optimizing the metal microstructure of a steel plate without requiring particular forming conditions in forming the steel pipe and without requiring heat treatment after pipe making. To be more specific, provided are a steel pipe for a linepipe with high compressive strength and excellent sour resistance performance having the composition which contains by mass% 0.03 to 0.10% C, 0.30% or less Si, 1.00 to 2.00% Mn, 0.015% or less P, 0.003% or less S, 0.080% or less Al, 0.005 to 0.035% Nb, 0.005 to 0.020% Ti, and Fe and unavoidable impurities as a balance, wherein C(%) - 0.065Nb(%) is 0.025 or more, a Ceq value is 0.3 or more, and the steel pipe has metal microstructure where a fraction of bainite is 60% or more, a fraction of rolled ferrite is 5% or less, a fraction of M-A constituent (MA) is 3% or less, an average grain size of MA is 2 µm or less, and an aspect ratio of MA is 5 or less, and a method of manufacturing the steel pipe.</p> |
