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1. (WO2018026014) STEEL SHEET AND PLATED STEEL SHEET

Pub. No.:    WO/2018/026014    International Application No.:    PCT/JP2017/028477
Publication Date: Fri Feb 09 00:59:59 CET 2018 International Filing Date: Sat Aug 05 01:59:59 CEST 2017
IPC: C22C 38/00
C22C 38/58
C21D 9/46
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: SANO, Kohichi
佐野 幸一
UNO, Makoto
宇野 誠
NISHIYAMA, Ryoichi
西山 亮一
YAMAGUCHI, Yuji
山口 裕司
SUGIURA, Natsuko
杉浦 夏子
NAKATA, Masahiro
中田 匡浩
Title: STEEL SHEET AND PLATED STEEL SHEET
Abstract:
This steel sheet has a specific chemical composition and is provided with a structure represented by, in terms of area ratio, 30–95% ferrite and 5–70% bainite. When a crystal grain is defined as a region which is surrounded by grain boundaries having a misorientation of 15° or higher and for which the equivalent circle diameter is 0.3 μm or larger, the proportion of crystal grains having an intragranular misorientation of 5–14° relative to all of the crystal grains is 20–100% in terms of area ratio. The average aspect ratio of ellipses equivalent to the crystal grains is 5 or lower. The average distribution density of the total of Ti carbides and Nb carbides having a particle size of 20 nm or larger in the ferrite grain boundaries is 10 particles/μm or lower.