公开(公告)号：US20240353033A1

公开(公告)日：2024-10-24

申请号：US18683569

申请日：2022-10-25

Applicant: NIPPON STEEL CORPORATION

Inventor： Akira DOI ,  Takeshi MIKI ,  Hiroyuki NAGAYAMA ,  Naoki KURODA

IPC: F16L13/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54 ,  C22C38/58

CPC classification number: F16L13/02 ,  C22C38/001 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/54 ,  C22C38/58 ,  C22C2202/00

Abstract: A girth welded joint of steel pipe 10 includes base metal portions 1a, 1b and a girth welded portion 2, wherein the girth welded portion 2 is formed of a weld metal portion 2a and weld heat affected zones 2b, 2c, the base metal portions 1a, 1b have a predetermined chemical composition, Pcm is within a range of 0.25 to 0.30, the weld metal portion 2a has a predetermined chemical composition, a content of B is 0.0010% or less, tensile strength of both base metal portions 1a, 1b and tensile strength of the girth welded portion 2 in a cross weld tensile test is 980 MPa or more, average hardness of the base metal portions 1a, 1b is 300 HV10 or more, an average softening width of the weld heat affected zones 2b, 2c is 4.0 mm or less, and an average softening degree is 80 HV10 or less.