HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND MANUFACTURING METHOD THEREFOR

Title:

HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND MANUFACTURING METHOD THEREFOR

Document Type and Number:

WIPO Patent Application WO/2013/099136

Kind Code:

A1

Abstract:

Provided is a high-strength hot-rolled steel sheet that exhibits little inter-coil variability in mechanical properties and excellent stretch flangeability. By mass, said steel sheet contains more than 0.010% and no more than 0.06% carbon, up to 0.3% silicon, up to 0.8% manganese, up to 0.03% phosphorus, up to 0.02% sulfur, up to 0.1% aluminum, up to 0.01% nitrogen, and 0.05-0.10% titanium, with the remainder comprising iron and unavoidable impurities. The amounts of silicon and manganese are minimized, the amount of segregation and the like is reduced, and strength variation due to inter-coil position differences is decreased. The structure of the steel sheet is such that the area fraction of a ferrite phase is at least 95%, the mean diameter of ferrite crystal grains is at least 1 µm, and TiC with a mean grain diameter of at most 7 nm is dispersed inside the ferrite crystal grains. This results in a high-strength hot-rolled steel sheet that maintains a yield strength of at least 530 MPa.

Inventors:

FUNAKAWA YOSHIMASA (JP)
YAMAMOTO TETSUO (JP)
UCHOMAE HIROSHI (JP)
NAKANO HIROSHI (JP)
KIZU TARO (JP)

Application Number:

PCT/JP2012/008003

Publication Date:

July 04, 2013

Filing Date:

December 14, 2012

Export Citation:

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Assignee:

JFE STEEL CORP (JP)

International Classes:

C22C38/00; B21B3/00; C21D9/46; C22C38/14; C22C38/60

Domestic Patent References:

WO2011162418A1	2011-12-29
WO2011162412A1	2011-12-29

Foreign References:

JP2010053434A	2010-03-11
JP2010255016A	2010-11-11
JP2003321736A	2003-11-14
JP2007308771A	2007-11-29
JP2004250743A	2004-09-09
JP2003321734A	2003-11-14
JP2003321735A	2003-11-14
JP2002363693A	2002-12-18
JP2011026690A	2011-02-10
JP2007247046A	2007-09-27

Other References: