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1. (WO2017150251) STEEL MATERIAL AND STEEL PIPE FOR USE IN OIL WELL

Pub. No.:    WO/2017/150251    International Application No.:    PCT/JP2017/006151
Publication Date: Sat Sep 09 01:59:59 CEST 2017 International Filing Date: Tue Feb 21 00:59:59 CET 2017
IPC: C22C 38/00
C22C 38/54
C21D 8/10
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: ARAI, Yuji
荒井 勇次
Title: STEEL MATERIAL AND STEEL PIPE FOR USE IN OIL WELL
Abstract:
A steel material is provided which has excellent SSC resistance even in high-pressure H2S environments. In mass%, the steel material contains C: 0.15-0.45%, Si: 0.10-1.0%, Mn: 0.10% to less than 0.90%, P: 0.05% or less, S: 0.01% or less, Al: 0.01-0.1%, N: 0.010% or less, Cr: 0.1-2.5%, Mo: 0.35-3.0% and Co: 0.50-3.0%, satisfies expressions (1) and (2), and contains 90% or more tempered martensite by volume fraction. C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15 - Co/6 + α ≧ 0.50 (1) (3C+Mo+3Co)/(3Mn+Cr) ≧ 1.0 (2) Effective B = B - 11(N-Ti/3.4)/14 (3) Here, α in expression (1) is 0.250 if the effective B (mass%), defined in expression (3), is greater than or equal to 0.0003%, and is 0 if the effective B is less than 0.0003%.