CPC C21D 9/08 (2013.01) [C22C 38/001 (2013.01); C22C 38/004 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01)] | 20 Claims |
1. A stainless steel pipe of a composition that comprises, in mass %, C: 0.005 to 0.08%, Si: 0.01 to 1.0%, Mn: 0.01 to 10.0%, Cr: 20 to 35%, Ni: 1.0 to 15.0%, Mo: 0.5 to 6.0%, N: 0.150 to less than 0.400%, and W: 1.9% or less, and one or two or more selected from Ti: 0.0001 to 0.3%, Al: 0.0001 to 0.3%, V: 0.005 to 1.5%, and Nb: 0.005 to less than 1.5%, and in which the balance is Fe and incidental impurities,
the composition containing N, Ti, Al, V, and Nb so as to satisfy the following formula (1),
0.150>N−(1.58Ti+2.70Al+1.58V+1.44Nb) (1)
wherein N, Ti, Al, V, and Nb represent the content of each element in mass % (the content is 0 (zero) percent for elements that are not contained),
the stainless steel pipe having an axial tensile yield strength of 757 MPa or more, an axial compressive yield strength/axial tensile yield strength ratio of 0.85 to 1.15, and a microstructure that is 20 to 80% ferrite phase by volume with the remainder containing an austenite phase,
the stainless steel pipe having pipe end portions at least one of which has a fastening portion for an external thread or an internal thread, and having a curvature radius of 0.2 mm or more and 0.4 mm or less for a corner R formed by a bottom surface of a thread root and a pressure-side flank surface of the thread, measured in an axial plane section of the fastening portion.
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