High strength plate with 980 MPa or above tensile strength excellent in bending workability

(19)

(11)

EP 2 105 515 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	24.03.2010 Bulletin 2010/12

(43)	Date of publication A2:
	30.09.2009 Bulletin 2009/40

(21)	Application number: 09001913.4

(22)	Date of filing: 11.02.2009

(51)

International Patent Classification (IPC):

C22C 38/12^(2006.01)
C22C 38/04^(2006.01)

C22C 38/02^(2006.01)

(84)	Designated Contracting States:
	AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK TR
	Designated Extension States:
	AL BA RS

(30)

Priority:

28.03.2008 JP 2008088309

(71)	Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
	Kobe-shi, Hyogo 651-8585 (JP)

(72)	Inventor:
	Shimoyama, Satoshi Kakogawa-shi Hyogo 675-0137 (JP)

(74)	Representative: Müller-Boré & Partner Patentanwälte
	Grafinger Strasse 2 81671 München 81671 München (DE)

(54)	High strength plate with 980 MPa or above tensile strength excellent in bending workability

(57) The high strength steel plate contains C: 0.1-0.25% (means mass%, hereinafter the same with respect to the chemical componential composition), Si: 0.1-0.5%, Mn: 0.5-2.0%, Cr: 0.1-1.5%, Mo: 0.1-0.5%, Ti: 0.01-0.05%, and Nb: 0.01-0.05% respectively, and contains V: 0.01-0.05% and/or B: 0.0001-0.005%, and the balance comprises iron with inevitable impurities, wherein the average grain size of prior austenite is 20 µm or below, the standard deviation (σ) of prior austenite grain size distribution is 5 µm or below, and the tensile strength is 980 MPa or above. With such constitution, high strength can be maintained while bending workability becomes excellent as well.

Search report