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1. (WO2017183630) STEEL

Pub. No.:    WO/2017/183630    International Application No.:    PCT/JP2017/015554
Publication Date: Fri Oct 27 01:59:59 CEST 2017 International Filing Date: Wed Apr 19 01:59:59 CEST 2017
IPC: C22C 38/00
C22C 38/14
C22C 38/58
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: SHINTAKU Yoshiaki
新宅 祥晃
OKAYAMA Atsushi
岡山 敦
Title: STEEL
Abstract:
For the steel according to the present invention, the chemical composition, in mass%, is C: 0.01-0.20%, Si: 0.02-0.70%, Mn: 0.30-2.50%, Ti: 0.003-0.024%, B: 0.0010-0.0050%, N: 0.0010-0.0090%, O: 0.0010-0.0050%, Insol. Zr: 0.0005-0.0100%, P: 0.050% or less, S: 0.0080% or less, Al: 0.005% or less, Sol. Zr: 0.0010% or less, total Ca and REM content: 0.0005% or less, the balance being made of Fe and impurities. BasBN represented by BasBN=(N−(Ti−(O−Insol.Zr×(32/91.224))×(95.734/48))×(14/47.867))×(10.811/14) is at least 0.0005 and BF represented by BF=B−BasBN is at least 0.0005. There are at least 50/mm2 Zr-containing oxides with equivalent circle diameter of at least 0.5 µm.