HIGH-STRENGTH STEEL SHEET AND METHOD FOR PRODUCING SAME

Title:

HIGH-STRENGTH STEEL SHEET AND METHOD FOR PRODUCING SAME

Document Type and Number:

WIPO Patent Application WO/2015/092982

Kind Code:

A1

Abstract:

Provided are: a high-strength steel sheet which is suitable as a material for an automotive part, has yield strength (YS) of 780 MPa or more and tensile strength (TS) of 1180 MPa or more, and also has excellent spot weldability, ductility and bending workability; and a method for producing the high-strength steel sheet. The high-strength steel sheet has a C content of 0.15% or less and contains ferrite at an area ratio of 8 to 45% and martensite at an area ratio of 55 to 85%, wherein the ratio of martensite adjacent only to ferrite to the whole structure is 15% or less, the average crystal particle diameter of each of ferrite and martensite is 10 μm or less, and the ratio of the area of ferrite having a crystal particle diameter of 10 μm or more relative to the area of ferrite existing in a region lying between the depth of 20 μm from the surface of the steel sheet and the depth of 100 μm from the surface of the steel sheet is less than 5%.

Inventors:

HASEGAWA HIROSHI (JP)
KANEKO SHINJIRO (JP)
MAKIMIZU YOICHI (JP)
SUZUKI YOSHITSUGU (JP)

Application Number:

PCT/JP2014/005941

Publication Date:

June 25, 2015

Filing Date:

November 27, 2014

Export Citation:

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Assignee:

JFE STEEL CORP (JP)

International Classes:

C22C38/00; C21D9/46; C22C38/38; C22C38/58; C23C2/06; C23C2/28; C23C2/40; C22C18/00

Foreign References:

JP2012012703A	2012-01-19
JP2010255094A	2010-11-11
JP2009209384A	2009-09-17
JP2012237042A	2012-12-06
JP2011132602A	2011-07-07

Other References: