Global Patent Index - EP 2465961 A1

EP 2465961 A1 20120620 - High-strength steel sheets and processes for production of the same

Title (en)

High-strength steel sheets and processes for production of the same

Title (de)

Hochfeste Stahlbleche und Verfahren zur deren Herstellung

Title (fr)

Feuilles d'acier très résistantes et leurs procédés de production

Publication

EP 2465961 A1 20120620 (EN)

Application

EP 11193464 A 20070713

Priority

  • EP 07790799 A 20070713
  • JP 2006194056 A 20060714
  • JP 2007144466 A 20070531
  • JP 2007144705 A 20070531
  • JP 2007145987 A 20070531

Abstract (en)

A high strength steel sheet with both excellent elongation and stretch-flanging performance is provided. The high strength steel sheet of the present invention comprises, in percent by mass, C : 0.05 to 0.3%, Si: 0.01 to 3.0%, Mn: 0.5 to 3.0%, Al: 0.01 to 0. 1%, and Fe and inevitable impurities as the remainder, and has a structure mainly composed of tempered martensite and annealed bainite. The space factor of the tempered martensite is 50 to 95%, the space factor of the annealed bainite is 5 to 30%, and the mean grain size of the tempered martensite is 10 µm or smaller in terms of the equivalent of a circle diameter. The steel sheet has a tensile strength of 590 MPa or higher. The high strength steel sheet of the present invention has a space factor of the martensite phase which is a main component of the metal structure is 80% or higher; the mean grain size of the martensite phase is 10 µm or smaller in terms of the equivalent of a circle diameter; in the martensite phase, the space factor of the martensite phase having a grain size of 10 µm or larger in terms of the equivalent of a circle diameter is 15% or lower; and the space factor of the retained austenite phase in the metal structure is 3% or lower. The high strength steel sheet of the present invention is a dual phase steel sheet mainly composed of a ferrite phase and martensite, and the space factor of the ferrite phase is 5 to 30%, and the space factor of the martensite phase is 50 to 95%. Moreover, the ferrite phase is annealed martensite.

IPC 8 full level

C22C 38/00 (2006.01); C21D 9/46 (2006.01); C22C 38/06 (2006.01); C22C 38/58 (2006.01)

CPC (source: EP KR US)

C21D 1/25 (2013.01 - EP KR US); C21D 6/005 (2013.01 - EP KR US); C21D 9/46 (2013.01 - EP KR US); C22C 38/02 (2013.01 - EP KR US); C22C 38/04 (2013.01 - EP KR US); C22C 38/06 (2013.01 - EP KR US); C22C 38/12 (2013.01 - EP KR US); C22C 38/14 (2013.01 - EP KR US); C21D 2211/005 (2013.01 - EP KR US); C21D 2211/008 (2013.01 - EP KR US)

Citation (applicant)

Citation (search report)

Designated contracting state (EPC)

AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC MT NL PL PT RO SE SI SK TR

Designated extension state (EPC)

AL BA HR MK RS

DOCDB simple family (publication)

EP 2053140 A1 20090429; EP 2053140 A4 20110629; EP 2053140 B1 20131204; CN 101460647 A 20090617; CN 101460647 B 20150520; EP 2465961 A1 20120620; EP 2465961 B1 20131204; EP 2465962 A1 20120620; EP 2465962 B1 20131204; KR 101082680 B1 20111115; KR 20090018166 A 20090219; US 2009277547 A1 20091112; WO 2008007785 A1 20080117

DOCDB simple family (application)

EP 07790799 A 20070713; CN 200780021032 A 20070713; EP 11193464 A 20070713; EP 11193479 A 20070713; JP 2007064019 W 20070713; KR 20087031702 A 20070713; US 30599807 A 20070713