Title:
THIN STEEL SHEET, PLATED STEEL SHEET, HOT-ROLLED STEEL SHEET MANUFACTURING METHOD, COLD-ROLLED FULL HARD STEEL SHEET MANUFACTURING METHOD, THIN STEEL SHEET MANUFACTURING METHOD, AND PLATED STEEL SHEET MANUFACTURING METHOD
Document Type and Number:
WIPO Patent Application WO/2017/168991
Kind Code:
A1
Abstract:
The purpose of the present invention is to provide: a 340 MPa grade thin steel sheet, which in addition to excellent bake hardenability and aging resistance combines excellent ductility and excellent surface quality; a plated steel sheet in which a thin steel sheet has been plated; methods for manufacturing a hot-rolled steel sheet and a cold-rolled full hard steel sheet that are necessary for obtaining a thin steel sheet; a thin steel sheet manufacturing method; and a plated steel sheet manufacturing method. Provided is a thin steel sheet characterized in: having a component composition that contains, in mass%, C: 0.0008-0.0024%, Si: less than 0.15%, Mn: greater than 0.55% and less than 0.90%, P: greater than 0.025% and less than 0.050%, S: 0.015% or less, sol. Al: 0.01%-0.1%, N: 0.01% or less, B: greater than 0.0003% and less than 0.0035%, Nb: greater than 0.005% and less than 0.016%, Ti: 0.009% or less, and Sb: 0.002-0.030%, wherein C and Nb satisfy expression (1) and the balance is made of Fe and unavoidable impurities, and having a steel structure in which the average crystal grain diameter d of ferrite at the ¼ sheet thickness position is 8-18 µm and the ratio ds/d of the average crystal grain diameter ds of ferrite in the steel sheet surface layer to d is 0.40-1.20; tensile strength being 340-380 MPa; bake hardening amount BH being 20-60 MPa; and r value being at least 1.4.
−10≤([%C]−([%Nb]/93)×12)×10000≤14 (1)
[%C] and [%Nb] represent the C and Nb contents, respectively.
Inventors:
ONO YOSHIHIKO (JP)
FUNAKAWA YOSHIMASA (JP)
FUNAKAWA YOSHIMASA (JP)
Application Number:
PCT/JP2017/002042
Publication Date:
October 05, 2017
Filing Date:
January 23, 2017
Export Citation:
Assignee:
JFE STEEL CORP (JP)
International Classes:
C22C38/00; C21D9/46; C22C38/60; C22C18/00; C22C18/04
Foreign References:
| JP2011246767A | 2011-12-08 | |||
| JP2013064169A | 2013-04-11 | |||
| JP2013072107A | 2013-04-22 | |||
| JP2007254766A | 2007-10-04 | |||
| JP2007092134A | 2007-04-12 | |||
| JP2013185240A | 2013-09-19 | |||
| JP2008274360A | 2008-11-13 | |||
| JP2010196096A | 2010-09-09 | |||
| JP2004137565A | 2004-05-13 | |||
| JP2009518541A | 2009-05-07 | |||
| JP2014043631A | 2014-03-13 |
Attorney, Agent or Firm:
KUMASAKA Akira et al. (JP)
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