US 12,331,371 B2
Stainless steel pipe and method for manufacturing same
Shunsuke Sasaki, Tokyo (JP); Masao Yuga, Tokyo (JP); Tatsuro Katsumura, Tokyo (JP); and Hideo Kijima, Tokyo (JP)
Assigned to JFE Steel Corporation, Tokyo (JP)
Appl. No. 17/800,283
Filed by JFE Steel Corporation, Tokyo (JP)
PCT Filed Jan. 20, 2021, PCT No. PCT/JP2021/001884
§ 371(c)(1), (2) Date Aug. 17, 2022,
PCT Pub. No. WO2021/171836, PCT Pub. Date Sep. 2, 2021.
Claims priority of application No. 2020-031195 (JP), filed on Feb. 27, 2020.
Prior Publication US 2023/0090536 A1, Mar. 23, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. C21D 9/08 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01)
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
OG exemplary drawing
 
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.