Title:
SEAMLESS STEEL PIPE AND METHOD FOR MANUFACTURING SEAMLESS STEEL PIPE
Document Type and Number:
WIPO Patent Application WO/2024/075433
Kind Code:
A1
Abstract:
Provided is a seamless steel pipe in which the difference between the strength at full wall thickness and the strength in a post-cutting state is low. This seamless steel pipe has a prescribed chemical composition. Fn1 represented by formula (1) is 0.44 or higher. The crystal grain size number according to ASTM E112-13 (2021) in a central portion of the wall thickness is 6.0 or higher. Each of NDos/NDc and NDis/NDc is 0.60 or higher, where, with respect to a cross-section perpendicular to the pipe axial direction, NDos is the number density of V-containing particles having a circle equivalent diameter of 10-100 nm at a depth of 2 mm from the outer surface of the steel pipe, Ndis is the number density of V-containing particles having a circle equivalent diameter of 10-100 nm at a depth of 2 mm from the inner surface of the steel pipe, and NDc is the number density of V-containing particles having a circle equivalent diameter of 10-100 nm in the central portion of the wall thickness. Formula (1): Fn1=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15. The atomic symbols in formula (1) are assigned the respective contained amount of the corresponding elements in terms of mass%.
Inventors:
SHITARA YUTARO (JP)
Application Number:
PCT/JP2023/031092
Publication Date:
April 11, 2024
Filing Date:
August 29, 2023
Export Citation:
Assignee:
NIPPON STEEL CORP (JP)
International Classes:
C22C38/00; C21D9/08; C22C38/58
Domestic Patent References:
| WO2011152240A1 | 2011-12-08 | |||
| WO2013161567A1 | 2013-10-31 |
Foreign References:
| JP2019127620A | 2019-08-01 |
Attorney, Agent or Firm:
UEBA, Hidetoshi et al. (JP)
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