HOT-ROLLED STEEL SHEET SUPERIOR IN FORMABILITY AFTER WELDING, WITH HIGH STRENGTH HAVING TENSILE STRENGTH OF 780 MPa OR HIGHER, OF MAKING HEAT AFFECTED ZONE HARDLY BE SOFTENED, COLD-ROLLED STEEL SHEET WITH HIGH STRENGTH, AND SURFACE-TREATED STEEL SHEET WITH HIGH STRENGTH

Title:

Document Type and Number:

Japanese Patent JP3881559

Kind Code:

B2

Abstract:

PROBLEM TO BE SOLVED: To provide a hot-rolled steel sheet with high strength superior in press formability after welding, which can control reduction in strength of a welded heat affected zone, and to provide a cold-rolled steel sheet with high strength, and a surface-treated steel sheet with high strength.
SOLUTION: These steel sheets comprise, by wt.%, 0.05-0.20% C, 0.005-1.3% Si, 1.0-3.2% Mn, 0.001-0.05% P, 0.0001-0.01% S, 0.0005-0.01% N, 0.001-0.1% Al, 0.05-0.5% Mo, one or two elements of 0.005-0.05% Nb and 0.001-0.05% Ti, and the balance Fe with unavoidable impurities, wherein a microstructure consists of martensite of 5-40% by area rate, the rest consists of one or more of ferrite, retained austenite, bainite, and tempered martensite, and amounts of C, Si, Mn, and Mo, and amounts of C, Si, Mn, and Mo, and amounts of C, Si, Mn, Mo, Nb, and Ti, respectively satisfy particular expressions (A) and (B).

More Like This:

JP4013969	Hot forged products with excellent fatigue strength, their manufacturing methods, and mechanical structural parts
JP6237365	The high intensity steel plate excellent in fabrication nature and the collision characteristic
JP2002146472	STEEL HAVING EXCELLENT HYDROGEN EMBRITTLEMENT CRACKING RESISTANCE AND ITS PRODUCTION METHOD

Inventors:

Koichi Goto
Riki Okamoto
Yuichi Taniguchi

Application Number:

JP2002031678A

Publication Date:

February 14, 2007

Filing Date:

February 08, 2002

Export Citation:

Click for automatic bibliography generation Help

Assignee:

Nippon Steel Corporation

International Classes:

C22C38/00; C21D9/46; C22C38/14; C22C38/16; (IPC1-7): C22C38/00; C22C38/14; C22C38/16

Domestic Patent References:

JP2000087175A
JP6264184A
JP2000080440A
JP2001192767A
JP2002285279A
JP2001214242A
JP2001207235A
JP7252591A
JP2003193193A

Attorney, Agent or Firm:

Tatsuo Watanuki
Fumio Yamamoto

Previous Patent: METALLIC SURFACE COATING AND METHOD OF FORMING THE SAME

Next Patent: COATED METAL SHEET FOR PRINTING WITH TEMPORARY DISPLAYING LAYER