公开(公告)号：US20230212723A1

公开(公告)日：2023-07-06

申请号：US17995636

申请日：2021-04-28

Applicant: NIPPON STEEL CORPORATION

Inventor： Mikiko NOGUCHI ,  Jun NAKAMURA ,  Masayuki SAGARA ,  Daisuke MATSUO ,  Yoshihei WAKINO

IPC: C22C38/58 ,  F16L9/02 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00

CPC classification number: C22C38/58 ,  F16L9/02 ,  C22C38/54 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/008 ,  C22C38/005 ,  C22C38/002 ,  C22C38/001

Abstract: The duplex stainless steel seamless pipe according to the present disclosure has the chemical composition described in the description and a microstructure consisting of 30 to 55% of ferrite, and austenite. In a square observation field of view region with sides of 250 μm including a center portion of the wall thickness and including a T direction and a C direction, a number of intersections NT which is a number of intersections between the line segment T1 to T4 described in the description and ferrite interfaces is 65 or more. A number of intersections NC which is a number of intersections between the line segments C1 to C4 described in the description and ferrite interfaces is 50 or more.

公开(公告)号：US20220195610A1

公开(公告)日：2022-06-23

申请号：US17594934

申请日：2020-07-17

Applicant: NIPPON STEEL CORPORATION

Inventor： Mikiko NOGUCHI ,  Takashi YAMAGUCHI

IPC: C23G1/08 ,  C22C38/52 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C23G5/00 ,  C23G3/04

Abstract: A method of manufacturing a martensitic stainless steel pipe includes: preparing a hollow shell, S1; a pickling step, S3-2, in which the hollow shell is immersed in nitrohydrofluoric acid solution at a temperature below 50° C.; after pickling step S3-2, a high-pressure water washing step, S4, in which high-pressure water is injected onto the outer surface of the hollow shell to clean the outer surface of the hollow shell; after high-pressure water washing step S4, a hot-water immersion step, S5, in which the hollow shell is immersed in hot water if necessary; and spraying gas onto the surface of the hollow shell, S6, before a lapse of 15 minutes from completion of high-pressure water washing step S4 or hot-water immersion step S5.

公开(公告)号：US20220145438A1

公开(公告)日：2022-05-12

申请号：US17597745

申请日：2020-08-18

Applicant: NIPPON STEEL CORPORATION

Inventor： Mikiko NOGUCHI ,  Yusaku TOMIO ,  Toshio MOCHIZUKI

IPC: C22C38/58 ,  C22C38/54 ,  C22C38/50 ,  C22C38/48 ,  C22C38/46 ,  C22C38/44 ,  C22C38/42 ,  C22C38/06 ,  C22C38/02 ,  C22C38/00

Abstract: The duplex stainless steel material according to the present disclosure has a chemical composition consisting of, in mass %, C: 0.030% or less, Si: 0.20 to 1.00%, Mn: 0.50 to 7.00%, P: 0.040% or less, S: 0.0100% or less, Al: 0.100% or less, Ni: 4.20 to 9.00%, Cr: 20.00 to 28.00%, Mo: 0.50 to 2.00%, Cu: 1.90 to 4.00%, N: 0.150 to 0.350%, V: 0.01 to 1.50%, and one or more types of element selected from the group consisting of Ca: 0.0001 to 0.0200% and Mg: 0.0001 to 0.0200%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2) described in the description, a microstructure consisting of 35.0 to less than 50.0% of ferrite in volume ratio and austenite as the balance, and a yield strength of 550 MPa or more.