Global Patent Index - EP 2589678 A4

EP 2589678 A4 20170719 - HIGH-STRENGTH STEEL SHEET WITH EXCELLENT PROCESSABILITY AND PROCESS FOR PRODUCING SAME

Title (en)

HIGH-STRENGTH STEEL SHEET WITH EXCELLENT PROCESSABILITY AND PROCESS FOR PRODUCING SAME

Title (de)

HOCHFESTES STAHLBLECH MIT AUSGEZEICHNETER VERARBEITBARKEIT UND VERFAHREN ZUR HERSTELLUNG DAVON

Title (fr)

TÔLE D'ACIER À RÉSISTANCE ÉLEVÉE PRÉSENTANT UNE EXCELLENTE APTITUDE AU TRAITEMENT AINSI QUE PROCÉDÉ DE FABRICATION ASSOCIÉ

Publication

EP 2589678 A4 20170719 (EN)

Application

EP 11801026 A 20110629

Priority

  • JP 2010147419 A 20100629
  • JP 2011065415 W 20110629

Abstract (en)

[origin: EP2589678A1] A thin high strength steel sheet having excellent formability and a method for manufacturing the sheet are provided. A hot rolling step of hot-rolling a steel having a composition which includes, by mass%, 0.08 to 0.15% of C, 0.5 to 1.5% of Si, 0.5 to 1.5% of Mn, 0.01 to 0.1% of Al, and 0.005% or less of N to form a hot rolled sheet is conducted. After the hot-rolled sheet is pickled, the hot rolled sheet is subjected to an annealing treatment of holding the hot rolled sheet in a first temperature region of an A c1 transformation point to an A c3 transformation point for 5 to 400 s by a continuous annealing line without cold rolling; and to a cooling treatment of cooling the sheet at an average cooling rate of 5°C/s or higher from the first temperature region to 700°C and adjusting a residence time in a second temperature region of 700°C to 400°C in the range of 30 to 400 s. As a result, a microstructure composed of a ferrite phase having an area fraction in the range of 75 to 90% with respect to the entire microstructure and a second phase including pearlite, the second phase having an area fraction in the range of 10 to 25% can be obtained. The pearlite accounts for 70% or more in terms of the area fraction with respect to the entire second phase and the average grain size of the pearlite is 5 µm or smaller. Thus, a high strength steel sheet with excellent formability having a high strength, i.e., a tensile strength TS of 540 MPa or more, excellent elongation, and excellent stretch flangeability can be obtained.

IPC 8 full level

C22C 38/06 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/08 (2006.01); C22C 38/12 (2006.01); C22C 38/14 (2006.01); C22C 38/18 (2006.01); C22C 38/54 (2006.01)

CPC (source: EP KR US)

C21D 8/0226 (2013.01 - EP US); C21D 8/0263 (2013.01 - EP US); C21D 9/46 (2013.01 - EP KR US); C22C 38/001 (2013.01 - EP US); C22C 38/005 (2013.01 - EP US); C22C 38/02 (2013.01 - EP US); C22C 38/04 (2013.01 - EP US); C22C 38/06 (2013.01 - EP KR US); C22C 38/08 (2013.01 - EP US); C22C 38/12 (2013.01 - EP US); C22C 38/14 (2013.01 - EP US); C22C 38/18 (2013.01 - EP US); C22C 38/54 (2013.01 - KR); C21D 2211/005 (2013.01 - EP US); C21D 2211/009 (2013.01 - EP US)

Citation (search report)

Designated contracting state (EPC)

AL 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 RS SE SI SK SM TR

DOCDB simple family (publication)

EP 2589678 A1 20130508; EP 2589678 A4 20170719; EP 2589678 B1 20180905; CN 102971443 A 20130313; CN 102971443 B 20150325; JP 2012012623 A 20120119; JP 5018934 B2 20120905; KR 101485237 B1 20150122; KR 20130021409 A 20130305; TW 201207126 A 20120216; TW I431124 B 20140321; US 2013233453 A1 20130912; WO 2012002566 A1 20120105

DOCDB simple family (application)

EP 11801026 A 20110629; CN 201180032346 A 20110629; JP 2010147419 A 20100629; JP 2011065415 W 20110629; KR 20127032907 A 20110629; TW 100122843 A 20110629; US 201113704781 A 20110629