COLD-ROLLED STEEL SHEET - NIPPON STEEL & SUMITOMO METAL CORP

Title:

COLD-ROLLED STEEL SHEET

Document Type and Number:

WIPO Patent Application WO/2013/005618

Kind Code:

A1

Abstract:

This high-tensile-strength cold-rolled steel sheet, which has superior rolling properties, work hardening properties and stretch flanging properties and has a tensile strength of at least 780 MPa, has: a chemical composition containing, by mass%, 0.020-0.30% exclusive of C, over 0.10% and no greater than 3.00% of Si, and over 1.00% and no greater than 3.50% of Mn; and a metal structure of which the primary phase is a phase formed by a low-temperature transformation, and the second phase contains residual austenite. The residual austenite has a volume ratio with respect to the overall structure of 4.0-25.0% exclusive and an average grain size of less than 0.80 μm, and of the residual austenite, the numerical density of residual austenite grains having a grain size of at least 1.2 μm is no greater than 3.0×10-2 grains/μm2.

Inventors:

HAGA JUN (JP)
NISHIO TAKUYA (JP)
WAKITA MASAYUKI (JP)
TANAKA YASUAKI (JP)
IMAI NORIO (JP)
TOMIDA TOSHIRO (JP)

Application Number:

PCT/JP2012/066380

Publication Date:

January 10, 2013

Filing Date:

June 27, 2012

Export Citation:

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Assignee:

NIPPON STEEL & SUMITOMO METAL CORP (JP)
HAGA JUN (JP)
NISHIO TAKUYA (JP)
WAKITA MASAYUKI (JP)
TANAKA YASUAKI (JP)
IMAI NORIO (JP)
TOMIDA TOSHIRO (JP)

International Classes:

C22C38/00; C22C38/06; C22C38/38; C21D9/46

Domestic Patent References:

WO2007015541A1

2007-02-08

Foreign References:

JP2005336526A	2005-12-08
JP2007182625A	2007-07-19
JP2006336074A	2006-12-14
JP2003277884A	2003-10-02
JP2004190050A	2004-07-08
JPS58123823A	1983-07-23
JPS59229413A	1984-12-22
JPH11152544A	1999-06-08
JPH1161326A	1999-03-05
JP2005179703A	2005-07-07
JP2001192768A	2001-07-17

Other References: