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1. (WO2017038786) SURFACE-TREATED STEEL SHEET FOR FUEL TANK

Pub. No.:    WO/2017/038786    International Application No.:    PCT/JP2016/075253
Publication Date: Fri Mar 10 00:59:59 CET 2017 International Filing Date: Tue Aug 30 01:59:59 CEST 2016
IPC: C23C 28/00
C22C 38/00
C22C 38/14
C21D 9/48
Applicants: NIPPON STEEL & SUMITOMO METAL CORPORATION
新日鐵住金株式会社
Inventors: SHOJI, Hiromasa
莊司 浩雅
KANETO, Taihei
金藤 泰平
FUDA, Masahiro
布田 雅裕
SATO, Hironori
佐藤 寛哲
SUGIURA, Natsuko
杉浦 夏子
YAMAGUCHI, Yuji
山口 裕司
Title: SURFACE-TREATED STEEL SHEET FOR FUEL TANK
Abstract:
A surface-treated steel sheet for a fuel tank having a Zn-Ni alloy-plated layer and a trivalent chromate film layer or chromate-free film layer formed thereon on one surface or both surfaces of a steel sheet, wherein the steel sheet contains, in terms of mass%, C: 0.0005-0.0050%, Si: 0.01-1.00%, Mn: 0.70-2.00%, P: 0.060% or less, S: 0.010% or less, Al: 0.01-0.30%, N: 0.001-0.010%, Ti: 0.010-0.050%, Nb: 0.010-0.040%, and B: 0.0005-0.0030%, and having a component composed of remainder Fe and unavoidable impurities, and concavities being present on the topmost surface layer of the trivalent chromate film layer or chromate-free film layer in a number of 50-1000/mm2 and in a surface area ratio of 20-80% with respect to the surface area of the steel plate, the recesses having a depth of 0.1 µm or more from the arithmetic average height of the cross-sectional curve of the topmost surface layer.